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Petroleum Exploration

13 Questions

GATE→2026→Core→Petroleum Exploration

Q1

MCQ[2 Marks]

Choose the CORRECT match of the sedimentary rocks in GROUP X with their processes/mechanisms of formation in GROUP Y. **GROUP X:** (P) Evaporite (Q) Sandstone (R) Limestone (S) Siltstones **GROUP Y:** (I) Physical process mainly consisting of lithification or cementation of deposition (II) Chemical process and depositions by marine living organisms (III) Anaerobic deposition of organic materials in mud bed (IV) Evaporation and precipitations of marine water

(A)

P-IV; Q-I; R-II; S-III

(B)

P-II; Q-IV; R-I; S-III

(C)

P-II; Q-III; R-IV; S-I

(D)

P-IV; Q-III; R-I; S-II

Explanation

GATE→2025→Core→Petroleum Exploration

Q2

MCQ[2 Marks]

Classification of kerogen is based on the relative amount of Carbon (C), Hydrogen (H) and Oxygen (O). Which ONE of the following options is CORRECT about Type II kerogen?

(A)

It is low in aliphatic compounds and H:C ratio < 0.84.

(B)

It is rich in aliphatic compounds and H:C ratio < 0.84.

(C)

It is low in aliphatic compounds and H:C ratio > 1.0.

(D)

It is rich in aliphatic compounds and H:C ratio > 1.0.

Explanation

GATE→2025→Core→Petroleum Exploration

Q3

NAT[2 Marks]

A homogeneous rock layer Q of density $2600\text{ kg/m}^3$ is lying below homogeneous rock layer P of density $2400\text{ kg/m}^3$. A compressional wave travels from P to Q. On reaching the interface of P and Q, this wave is incident normally and gets reflected and refracted. The velocity of the compressional wave is $2.7\text{ km/s}$ in the rock layer P and $3.5\text{ km/s}$ in layer Q. The ratio of reflection coefficient to the transmission coefficient at the interface is ______ (rounded off to two decimal places).

Explanation

GATE→2024→Core→Petroleum Exploration

Q4

MCQ[1 Mark]

Which ONE of the following options represents the waves generated during partitioning of acoustic energy at an interface inside the Earth?

(A)

Rayleigh waves

(B)

Love waves

(C)

Body waves

(D)

Surface waves

Explanation

GATE→2024→Core→Petroleum Exploration

Q5

MCQ[1 Mark]

"Earth is a low-pass filter". This implies it filters out which ONE of the following parameters in the subsurface?

(A)

Phase

(B)

Amplitude

(C)

Frequency

(D)

Velocity

Explanation

GATE→2024→Core→Petroleum Exploration

Q6

MCQ[1 Mark]

Which ONE is the correct formula for calculation of Foldage of a 2D seismic line?

(A)

$Foldage = (\frac{1}{2})(\text{number of geophones})(\frac{\text{geophone interval spacing}}{\text{shot interval spacing}})$

(B)

$Foldage = (\frac{1}{2})(\text{number of geophones})(\frac{\text{shot interval spacing}}{\text{geophone interval spacing}})$

(C)

$Foldage = (\frac{1}{2})(\text{number of shots})(\frac{\text{shot interval spacing}}{\text{geophone interval spacing}})$

(D)

$Foldage = (\frac{1}{2})(\text{number of shots})(\frac{\text{geophone interval spacing}}{\text{shot interval spacing}})$

Explanation

GATE→2024→Core→Petroleum Exploration

Q7

MCQ[2 Marks]

The figures below show the typical geometry of the subsurface strata in relation to the boundaries of the depositional sequences. Which ONE of the following options CORRECTLY represents the four seismic sequences with their corresponding names?

(A)

I-Onlap; II-Toplap; III-Erosional truncation; IV-Downlap

(B)

I-Onlap; II-Downlap; III-Erosional truncation; IV-Toplap

(C)

I-Erosional truncation; II-Toplap; III-Onlap; IV-Downlap

(D)

I-Erosional truncation; II-Downlap; III-Onlap; IV-Toplap

Explanation

GATE→2023→Core→Petroleum Exploration

Q8

MCQ[1 Mark]

Which of the following is a sedimentary rock?

(A)

Amphibolite

(B)

Chalk

(C)

Gabbro

(D)

Schist

Explanation

GATE→2023→Core→Petroleum Exploration

Q9

MCQ[1 Mark]

Kerogen classification (Van Krevelen diagram) plots atomic ratios. Which of the following represents the X-axis and Y-axis, respectively?

(A)

H:C ratio and O:C ratio

(B)

O:C ratio and H:C ratio

(C)

C:H ratio and C:O ratio

(D)

C:O ratio and C:H ratio

Explanation

GATE→2023→Core→Petroleum Exploration

Q10

MSQ[1 Mark]

Which of the following hydrocarbon trap(s) is/are a result of sedimentary facies changes (stratigraphic traps)?

(A)

Salt dome

(B)

Unconformity

(C)

Pinch out

(D)

Sand lens

Explanation

GATE→2023→Core→Petroleum Exploration

Q11

MCQ[2 Marks]

Match the seismic data processing terms in Group-I with their objectives/features in Group-II: **Group-I:** (P) Stacking (Q) Multiple (R) Bow tie (S) Deconvolution **Group-II:** (I) Synform (II) Noise reduction (III) Resolution enhancement (IV) Echo

(A)

P-II; Q-IV; R-I; S-III

(B)

P-II; Q-I; R-IV; S-III

(C)

P-II; Q-IV; R-I; S-II

(D)

P-II; Q-I; R-IV; S-II

Explanation

GATE→2022→Core→Petroleum Exploration

Q12

MSQ[2 Marks]

An exploratory well is planned in a basin up to $5000 \text{ m}$. Surface temperature $T_s = 30^\circ\text{C}$, geothermal gradient $G = 0.025^\circ\text{C/m}$. Select the possible depth range(s) corresponding to the oil window ($60^\circ\text{C}$ to $120^\circ\text{C}$ / $90^\circ\text{C}$ to $150^\circ\text{C}$).

(A)

800 m to 950 m

(B)

1500 m to 1650 m

(C)

3100 m to 3150 m

(D)

4550 m to 4600 m

Explanation

GATE→2022→Core→Petroleum Exploration

Q13

NAT[2 Marks]

Hydrogen index (HI) of a source rock is $500 \text{ mg HC/g TOC}$. If $400 \text{ g}$ of rock produces $6000 \text{ mg}$ of hydrocarbons during pyrolysis, the total organic carbon (TOC) in weight% is (rounded off to one decimal place).

Explanation

Oil and Gas Well Drilling Technology

35 Questions

GATE→2026→Core→Oil and Gas Well Drilling Technology

Q14

MCQ[1 Mark]

Which of the following is the basic mechanism of hydrocyclones and centrifuges used for solids control in a drilling operation?

(A)

Screening

(B)

Forced settling

(C)

Chemical flocculation

(D)

Dilution

Explanation

GATE→2026→Core→Oil and Gas Well Drilling Technology

Q15

MCQ[1 Mark]

Which of the following is the role of stabilizer subs in the rotary drilling process?

(A)

To prevent the drill-string from falling into the wellbore

(B)

To keep casing equidistant from the wellbore wall

(C)

To assist in keeping the drill collars centralized

(D)

To isolate the wellbore fluid from the subsurface formations

Explanation

GATE→2026→Core→Oil and Gas Well Drilling Technology

Q16

MSQ[1 Mark]

Which of the following options is/are representing the rheological behavior of a conventional drilling fluid?

(A)

Dilatant

(B)

Pseudoplastic

(C)

Thixotropic

(D)

Rheopectic

Explanation

GATE→2026→Core→Oil and Gas Well Drilling Technology

Q17

NAT[1 Mark]

When 92 ml of distilled water (density = $1.0 \text{ g/cm}^3$) is mixed with 23 grams of NaCl salt, the density of the resultant brine solution is $1.15 \text{ g/cm}^3$. The volume of the brine solution (in ml) is

Explanation

GATE→2026→Core→Oil and Gas Well Drilling Technology

Q18

MCQ[2 Marks]

Stokes' law is used to calculate the settling rate in the drilling fluid for two batches (P and Q) of barite. The particle (spherical) size of barite from batch P is $75~\mu m$ and that for batch Q is $25~\mu m$. The particle settling rate in the drilling fluid for the batch P is ______ times that for the batch Q.

(A)

Four

(B)

Nine

(C)

Two

(D)

One

Explanation

GATE→2026→Core→Oil and Gas Well Drilling Technology

Q19

MSQ[2 Marks]

A wellbore has true vertical depth (TVD) of 10000 ft. The pore pressure of the formation fluid in the permeable stratum at the bottom of the wellbore is 6500 psig. Which of the following is/are the acceptable average static mud density value(s) (in lbm/gal) to prevent the flow of the formation fluid from the permeable stratum to the wellbore? [Given: $1 \text{ lbm/gal}$ mud is equivalent to $0.052 \text{ psi/ft}$]

(A)

13.8

(B)

11.3

(C)

11.8

(D)

13.2

Explanation

GATE→2026→Core→Oil and Gas Well Drilling Technology

Q20

NAT[2 Marks]

A drilling fluid following power law model is being circulated in a wellbore at the rate of $600 \text{ gal/min}$. The internal diameter ($D_i$) of the drill-pipe is 4.276 inches. The power law parameter ($n$) for the drilling fluid in the applicable flow regime is 0.67. The wall shear-rate ($\dot{\gamma}_w$) inside the drill-pipe is given by the following equation: $$\dot{\gamma}_w = \left(\frac{3n+1}{4n}\right) \times \frac{8V}{D_i}$$ where $V$ is the average drilling fluid velocity inside the drill-pipe. The value of wall shear-rate inside the drill-pipe (in $\text{s}^{-1}$) is [Given: 1 gallon = $3785.4 \text{ cm}^3$; 1 inch = $2.54 \text{ cm}$]

Explanation

GATE→2026→Core→Oil and Gas Well Drilling Technology

Q21

NAT[2 Marks]

The upper limit of the scale of the dial reading for a given rotational oilfield viscometer is $300^{\circ}$. At the rotational rate of 100 RPM, the highest possible effective (apparent) viscosity measurable (in cP) is [Given: $1^{\circ}$ dial reading is equivalent to $5.11 \text{ dynes/cm}^2$ or $0.511 \text{ Pa}$; $1 \text{ RPM} = 1.703 \text{ s}^{-1}$]

Explanation

GATE→2026→Core→Oil and Gas Well Drilling Technology

Q22

NAT[2 Marks]

A drill-string placed in a wellbore is composed of 6000 ft of drill-pipe having internal diameter of 4.67 inches. The drilling fluid is being pumped at the rate of 80 cycles/minute and the pump factor is $0.21 \text{ bbl/cycle}$. Assume the amount of drilling fluid in the drill-collar and drill-bit to be negligible. The time required to circulate the drilling fluid from the surface to the drill-bit (in minutes) is [$1 \text{ bbl} = 5.61 \text{ ft}^3$]

Explanation

GATE→2025→Core→Oil and Gas Well Drilling Technology

Q23

MCQ[1 Mark]

Which ONE of the following options is CORRECT in relation to the standard drill pipe?

(A)

Nominal weight is equal to the actual weight.

(B)

Nominal weight is less than the actual weight.

(C)

Nominal weight is greater than the actual weight.

(D)

Nominal weight is twice the actual weight.

Explanation

GATE→2025→Core→Oil and Gas Well Drilling Technology

Q24

MCQ[1 Mark]

Four different multilateral well patterns (Forked, Branched, Dual opening and Splayed) are shown in the figure. Which ONE of the following options correctly identifies the multilateral well patterns?

(A)

I - Forked; II - Branched; III - Dual Opening; IV - Splayed

(B)

I - Dual Opening; II - Branched; III - Forked; IV - Splayed

(C)

I - Dual Opening; II - Splayed; III - Forked; IV - Branched

(D)

I - Branched; II - Dual Opening; III - Splayed; IV - Forked

Explanation

GATE→2025→Core→Oil and Gas Well Drilling Technology

Q25

NAT[1 Mark]

The hoisting system of a drilling rig contains 7 lines strung (ideal sheaves) with hook load of $3.0 \times 10^5\text{ kg}$. The static derrick load is ______ $\times 10^5\text{ kg}$ (rounded off to one decimal place).

Explanation

GATE→2025→Core→Oil and Gas Well Drilling Technology

Q26

MCQ[2 Marks]

Three different pressure profiles are shown in the figure. CSD is Casing Setting Depth. Match the entries in GROUP I with the entries in GROUP II: **GROUP I:** (P) Profile 1 (Q) Profile 2 (R) Profile 3 **GROUP II:** (I) Reduced wellbore integrity due to weak formation (II) Reduced wellbore integrity due to weak casing (III) Full wellbore integrity

(A)

P-I; Q-II; R-III

(B)

P-II; Q-III; R-I

(C)

P-III; Q-I; R-II

(D)

P-II; Q-I; R-III

Explanation

GATE→2025→Core→Oil and Gas Well Drilling Technology

Q27

MCQ[2 Marks]

A drilling fluid with time-dependent rheology is used for the rotary drilling of a reservoir. The following equation describes the dependence of shear stress ($\tau$) on shear rate ($\dot{\gamma}$): $$\tau + \frac{\mu_0}{\alpha} \frac{d\tau}{dt} = \mu_0 \dot{\gamma}$$ where $\mu_0$ and $\alpha$ are constants. If the rotation of the drill pipe is stopped at time $t=0$ (so $\dot{\gamma} = 0$), then the relaxation behavior of the fluid stress with time is

(A)

$\tau \propto e^{-\frac{\mu_0 t}{\alpha}}$

(B)

$\tau \propto e^{\frac{\mu_0 t}{\alpha}}$

(C)

$\tau \propto e^{-\frac{\alpha t}{\mu_0}}$

(D)

$\tau \propto e^{\frac{\alpha t}{\mu_0}}$

Explanation

GATE→2025→Core→Oil and Gas Well Drilling Technology

Q28

MSQ[2 Marks]

In a capillary rise experiment with a capillary tube of length $l_1$, water rises to a height $h$ such that $h < l_1$. If the capillary tube is cut to a length $l_2$ such that $l_2 < h$ and the experiment is repeated, which of the following statements is/are CORRECT?

(A)

Water overflows from the top of the tube.

(B)

Water does not overflow from the top of the tube.

(C)

At equilibrium, radius of curvature of meniscus are same in both the experiments.

(D)

At equilibrium, radius of curvature of meniscus are different in both the experiments.

Explanation

GATE→2025→Core→Oil and Gas Well Drilling Technology

Q29

NAT[2 Marks]

The hydrostatic pressure gradient in a vertical well drilled in a relaxed depositional basin is $0.452\text{ psi/ft}$. Assume that the gradient of effective horizontal stress with depth is constant in the drilling zone and has a value of $9.96 \times 10^{-2}\text{ psi/ft}$. The casing shoe is at 4000 ft depth. While drilling the bore hole below the casing shoe with 10 ppg mud, the maximum allowed standpipe pressure is ______ psi (rounded off to one decimal place).

Explanation

GATE→2025→Core→Oil and Gas Well Drilling Technology

Q30

NAT[2 Marks]

A vertical well is drilled up to a depth of 4000 ft. Further drilling starts with 10 ppg of fresh mud and $50000\text{ lbf}$ weight on bit (WOB). An equivalent circulation density (ECD) of 10.75 ppg was recorded. The total circulation pressure loss is estimated to be 110 psi. The decrease in hook load is ______ lbf (rounded off to one decimal place).

Explanation

GATE→2025→Core→Oil and Gas Well Drilling Technology

Q31

NAT[2 Marks]

A horizontal well is planned with two radial sections to land the target at an angle of $90^\circ$. The total vertical depth (TVD) between the surface and the target is 8000 ft. The buildup rate is $6^\circ$ per 100 ft in the first section and $9^\circ$ per 100 ft in the second section. The total angle built by the second section is $30^\circ$. The distance of the first kickoff point from the surface is ______ ft (rounded off to one decimal place).

Explanation

GATE→2025→Core→Oil and Gas Well Drilling Technology

Q32

NAT[2 Marks]

A Newtonian fluid is transported through a smooth horizontal pipe of diameter $1\text{ m}$ at a flow rate of $3.14\text{ m}^3/\text{s}$. The length of the pipe is $1\text{ km}$. The viscosity of the oil is $0.02\text{ Pa}\cdot\text{s}$ and its density is $800\text{ kg/m}^3$. Consider the Darcy friction factor ($f$) for turbulent flow in a smooth pipe is given as: $$f = \frac{0.316}{Re^{0.25}}$$ Assuming fully-developed flow in the pipe, the pressure drop due to the frictional effect is ______ kPa (rounded off to two decimal places).

Explanation

GATE→2024→Core→Oil and Gas Well Drilling Technology

Q33

MCQ[1 Mark]

Marsh funnel viscosity is reported as number of seconds required for one quart of drilling fluid sample to flow out of a Marsh funnel. The time of efflux of one quart of fresh water from a Marsh funnel at $70 \pm 5^\circ\text{F}$ is ______ seconds.

(A)

$21 \pm 0.5$

(B)

$26 \pm 0.5$

(C)

$31 \pm 0.5$

(D)

$36 \pm 0.5$

Explanation

GATE→2024→Core→Oil and Gas Well Drilling Technology

Q34

MCQ[1 Mark]

Which mud type will have the highest acoustic velocity from the following options?

(A)

Mud with live oil at low temperature

(B)

Mud with dead oil at high temperature

(C)

Mud with live oil at high temperature

(D)

Mud with dead oil at low temperature

Explanation

GATE→2024→Core→Oil and Gas Well Drilling Technology

Q35

NAT[1 Mark]

A field rotational viscometer containing a drilling fluid gives a dial reading of $12^\circ$ and $20^\circ$ at rotor speeds of 300 rpm and 600 rpm, respectively. The drilling fluid is assumed to obey power law model, $\tau = K\dot{\gamma}^n$. The power law index, $n$, is (round off to two decimal places).

Explanation

GATE→2024→Core→Oil and Gas Well Drilling Technology

Q36

NAT[2 Marks]

If a weight of $P = 100\text{ N}$ is supported by two massless strings connected to the walls as shown in the figure, the value of $T_1$ is ______ N (round off to one decimal place).

Explanation

GATE→2024→Core→Oil and Gas Well Drilling Technology

Q37

NAT[2 Marks]

The settling velocity ($v_s$) of a spherical particle in a Newtonian fluid using Stokes' law is $v_s = \frac{g d_s^2 (\rho_s - \rho_l)}{18 \mu}$. Density of barite is $4200\text{ kg/m}^3$ and drilled solid particle is $2600\text{ kg/m}^3$. Fluid density is $1300\text{ kg/m}^3$. The diameter of a drilled spherical solid particle that has the same settling velocity as a spherical barite particle of $0.1\text{ mm}$ diameter in the drilling fluid is ______ mm (round off to two decimal places).

Explanation

GATE→2024→Core→Oil and Gas Well Drilling Technology

Q38

NAT[2 Marks]

A two-cylinder reciprocating positive-displacement duplex/double-acting mud pump is used for mud circulation (delivering fluid on both forward and backward strokes, i.e., 2 displacements per cylinder per stroke cycle). Liner diameter = $15\text{ cm}$, piston rod diameter = $6\text{ cm}$, stroke length = $40\text{ cm}$, volumetric efficiency = $85\%$. The total volume of fluid displaced per complete pump cycle (2 cylinders $\times$ both strokes) is ______ $\text{cm}^3$ (round off to nearest integer).

Explanation

GATE→2023→Core→Oil and Gas Well Drilling Technology

Q39

MSQ[1 Mark]

Which of the following option(s) is/are indication(s) of a well kick?

(A)

Decrease in mud pit volume

(B)

Increase in mud pit volume

(C)

Decrease in pump pressure

(D)

Increase in pump pressure

Explanation

GATE→2023→Core→Oil and Gas Well Drilling Technology

Q40

NAT[2 Marks]

A kill mud density is required such that bottomhole pressure equals formation pressure. Shut-in pressure (SIDPP) = $6.8 \times 10^6 \text{ Pa}$ at $3500 \text{ m}$ depth. Original mud density $\rho_1 = 1100 \text{ kg/m}^3$. The kill mud density $\rho_2$ is $\text{kg/m}^3$ (rounded to two decimal places).

Explanation

GATE→2023→Core→Oil and Gas Well Drilling Technology

Q41

NAT[2 Marks]

A non-Newtonian drilling fluid obeying Bingham plastic model ($\tau_{yx} = \mu_p \dot{\gamma} + \tau_{yx}^o$) is placed between two flat parallel plates of area $10 \text{ cm}^2$ separated by $1 \text{ cm}$. Force to initiate motion (yield stress) = $300 \text{ dyne}$. Force to keep upper plate moving at $10 \text{ cm/s}$ = $600 \text{ dyne}$. The Bingham plastic viscosity $\mu_p$ is $\text{dyne}\cdot\text{s/cm}^2$ (rounded to nearest integer).

Explanation

GATE→2022→Core→Oil and Gas Well Drilling Technology

Q42

MCQ[1 Mark]

The dynamic mud inflow and outflow rate profiles are shown. Identify 'Hole ballooning' and 'Lost circulation' cases.

(A)

Case 1 - Hole ballooning; Case 3 - Lost circulation

(B)

Case 2 - Lost circulation; Case 3 - Hole ballooning

(C)

Case 1 - Lost circulation; Case 2 - Hole ballooning

(D)

Case 2 - Hole ballooning; Case 3 - Lost circulation

Explanation

GATE→2022→Core→Oil and Gas Well Drilling Technology

Q43

MSQ[1 Mark]

A drilling mud with high gel strength is undesirable because it

(A)

retards the separation of cuttings and entrained gas at the surface.

(B)

leads to the lost circulation.

(C)

creates swabbing action beneath the bit while pulling the string.

(D)

leads to the hole ballooning.

Explanation

GATE→2022→Core→Oil and Gas Well Drilling Technology

Q44

NAT[1 Mark]

An oil well is drilled using an $8.5\text{-inch}$ drill bit at ROP = $30 \text{ ft/hr}$. Rotary speed $N = 20 \text{ rpm}$, WOB $W = 3500 \text{ lb}$. The value of the 'd' exponent is (rounded off to two decimal places).

Explanation

GATE→2022→Core→Oil and Gas Well Drilling Technology

Q45

NAT[1 Mark]

A vertical wellbore is drilled with a $12.25\text{-inch}$ bit, drilling $385 \text{ ft}^3$ of rock in $6.5 \text{ hr}$. The washed-out hole diameter is $12.49 \text{ inches}$. The average rate of penetration (ROP) in $\text{ft/hr}$ is (rounded off to two decimal places).

Explanation

GATE→2022→Core→Oil and Gas Well Drilling Technology

Q46

NAT[2 Marks]

Station survey data: A ($4499 \text{ m}$, $\alpha_1 = 14.8^\circ$, $\beta_1 = 19^\circ$), B ($4530 \text{ m}$, $\alpha_2 = 13.5^\circ$, $\beta_2 = 10^\circ$). Using the provided dogleg formula, the dogleg severity per $100 \text{ m}$ is (rounded off to one decimal place).

Explanation

GATE→2022→Core→Oil and Gas Well Drilling Technology

Q47

NAT[2 Marks]

Drill string length = $2500 \text{ m}$ ($2000 \text{ m}$ drill pipe at $30 \text{ kg/m}$, $500 \text{ m}$ drill collar at $870 \text{ kg/m}$). Annulus mud SG = 1.5, internal mud SG = 1.4. Steel density = $7850 \text{ kg/m}^3$. The overall buoyant weight acting on the hook is kN (rounded off to two decimal places).

Explanation

GATE→2022→Core→Oil and Gas Well Drilling Technology

Q48

NAT[2 Marks]

A drilling rig has 12 lines strung, output power = $650 \text{ HP}$. At pullout speed $v_1 = 52.5 \text{ ft/min}$, fast line tension $F_1 = 46180 \text{ lb}$. If fast line tension $F_2 = 35690 \text{ lb}$ at the same power and constant efficiency, the new pullout speed $v_2$ is ft/min (rounded off to one decimal place).

Explanation

Reservoir Engineering

45 Questions

GATE→2026→Core→Reservoir Engineering

Q49

MCQ[1 Mark]

For a single-phase dry gas reservoir having a well producing only dry gas, E represents gas expansion factor and $B_g$ represents gas formation volume factor. Which of the following options is CORRECT?

(A)

$E \propto \frac{1}{B_g}$

(B)

$E \propto B_g$

(C)

$E \propto B_g^2$

(D)

$E \propto B_g^3$

Explanation

GATE→2026→Core→Reservoir Engineering

Q50

NAT[1 Mark]

An oil has a density of $50 \text{ lbm/ft}^3$ at Standard Temperature and Pressure (STP) conditions. The density of the oil (in °API) is [Given: water density is $62.4 \text{ lbm/ft}^3$ at STP]

Explanation

GATE→2026→Core→Reservoir Engineering

Q51

MSQ[2 Marks]

Which of the following is/are obtained using a core sample?

(A)

Porosity

(B)

Pore size distributions

(C)

Absolute permeability

(D)

Reservoir boundary

Explanation

GATE→2026→Core→Reservoir Engineering

Q52

NAT[2 Marks]

Oil is being produced from an undersaturated oil reservoir (with no initial gas cap). The reservoir rock compressibility and water saturation are negligible. There is no water influx, and there is no water production from the well. The initial oil formation volume factor was $1.24 \text{ RB/STB}$. After production of oil for a short period of time, the reservoir pressure is still above the bubble-point pressure, and the oil formation volume factor has changed to $1.25 \text{ RB/STB}$. The calculated oil recovery factor (in fraction) is [RB: Reservoir Barrel; STB: Stock Tank Barrel]

Explanation

GATE→2026→Core→Reservoir Engineering

Q53

NAT[2 Marks]

Consider one-dimensional oil flow in a horizontal porous media having length of 2000 ft, constant cross-sectional area of $6000 \text{ ft}^2$ and absolute permeability of 50 mD. Oil of viscosity 2 cP is flowing along the length (perpendicular to the cross section) such that the pressure at the inlet and outlet are 2500 psig and 2200 psig, respectively. Using the Darcy's equation for single phase flow, the flow rate of the oil through this porous media (in bbl/day) is [$1 \text{ bbl} = 5.61 \text{ ft}^3$]

Explanation

GATE→2026→Core→Reservoir Engineering

Q54

NAT[2 Marks]

A gas reservoir has bulk volume of $10000 \text{ ft}^3$, connate water saturation of 0.2 and porosity of 0.2. There is no oil present in the reservoir. The gas formation volume factor, $B_g$ is $0.005 \text{ RCF/SCF}$. The volume of gas in-place for this reservoir (in SCF) is $\times 10^4$.

Explanation

GATE→2025→Core→Reservoir Engineering

Q55

MCQ[1 Mark]

Four curves designated as I, II, III, and IV are shown in the figure. $P_b$ is the bubble point pressure of a crude oil at the given temperature. Which ONE of the following options correctly depicts the solubility of asphaltene ($q_a$) in the crude oil with pressure ($P$) at a given temperature?

(A)

I

(B)

II

(C)

III

(D)

IV

Explanation

GATE→2025→Core→Reservoir Engineering

Q56

MCQ[1 Mark]

Crude oil denser than pure water has the API gravity

(A)

less than $10^\circ$

(B)

between $10^\circ$ and $20^\circ$

(C)

between $20^\circ$ and $60^\circ$

(D)

more than $60^\circ$

Explanation

GATE→2025→Core→Reservoir Engineering

Q57

MCQ[1 Mark]

For a hydrocarbon reservoir, the following parameters are used in the general material balance equation (MBE): $N$ = Initial oil in place, stb $G$ = Initial volume of gas cap, scf $m$ = Ratio of initial gas cap volume to initial oil volume, rb/rb $S_{wi}$ = Initial water saturation $S_{oi}$ = Initial oil saturation $B_{oi}$ = Initial oil formation volume factor, rb/stb $B_{gi}$ = Initial gas formation volume factor, rb/scf The total pore volume (in rb) of the reservoir is

(A)

$\frac{G B_{gi} (1+m)}{1 - S_{oi}}$

(B)

$\frac{N B_{oi} (1-m)}{1 - S_{oi}}$

(C)

$\frac{N B_{oi} (1+m)}{1 - S_{wi}}$

(D)

$\frac{G B_{gi} (1-m)}{1 - S_{wi}}$

Explanation

GATE→2025→Core→Reservoir Engineering

Q58

MSQ[1 Mark]

Which of the following statement(s) is/are CORRECT?

(A)

Gradient of temperature is a vector.

(B)

Gradient of pressure is a vector.

(C)

Divergence of velocity is a vector.

(D)

Gradient of velocity is a scalar.

Explanation

GATE→2025→Core→Reservoir Engineering

Q59

NAT[1 Mark]

Reservoir Quality Index (RQI) based on Kozeny-Carman equation as a function of permeability ($k$ in mD) and porosity ($\phi$ in fraction) is given by: $$RQI = C \sqrt{\frac{k}{\phi}}$$ where $C$ is a constant with a value of 0.0314. If a carbonate reservoir has the permeability of 152 mD and the porosity of 0.18, then the RQI is ______ $\mu m$ (rounded off to two decimal places).

Explanation

GATE→2025→Core→Reservoir Engineering

Q60

NAT[1 Mark]

Natural gas is produced at a flow rate of $2\text{ MMscf/day}$ at the wellhead having temperature and pressure of $560^\circ\text{R}$ and $200\text{ psi}$, respectively. The apparent molecular weight and the compressibility factor ($z$) of the gas are estimated to be $20\text{ g/g-mole}$ and 0.8, respectively, at wellhead conditions. The gas formation volume factor ($B_g$) at the wellhead condition is ______ $\times 10^{-2}\text{ ft}^3/\text{scf}$ (rounded off to one decimal place).

Explanation

GATE→2025→Core→Reservoir Engineering

Q61

MSQ[2 Marks]

The effect of pressure on various properties of black oil is shown in the figure. The bubble point pressure is $P_b$. Which of the following option(s) is/are CORRECT?

(A)

Curve 1 represents solution gas-oil ratio.

(B)

Curve 2 represents oil viscosity.

(C)

Curve 3 represents oil formation volume factor.

(D)

Curve 3 represents oil density.

Explanation

GATE→2025→Core→Reservoir Engineering

Q62

NAT[2 Marks]

The drainage oil-water capillary pressure data for a core retrieved from a homogeneous isotropic reservoir is listed in the table (at WOC = 4100 ft, $P_c = 0$). Assume densities of water and oil are $1.04\text{ g/cc}$ and $0.84\text{ g/cc}$, $g = 980\text{ cm/s}^2$, $\sigma = 35\text{ dynes/cm}$, $\theta = 0^\circ$. The depth of free-water level (FWL) is at ______ ft (rounded off to one decimal place).

Explanation

GATE→2025→Core→Reservoir Engineering

Q63

NAT[2 Marks]

The laboratory analysis data obtained from the core is as follows: Weight of clean dry core in air = $30\text{ g}$ Weight of core completely saturated with oil = $32\text{ g}$ Weight of saturated core completely immersed in oil = $24\text{ g}$ If the density of oil used for saturation of core during the experiment is $0.88\text{ g/cc}$, then the effective porosity of the core is ______ % (rounded off to two decimal places).

Explanation

GATE→2025→Core→Reservoir Engineering

Q64

NAT[2 Marks]

The Buckley Leverett frontal advance theory is employed to evaluate the performance of the water flooding operation in a horizontal reservoir. Given: Cross-sectional flow area = $40000\text{ ft}^2$ Payzone thickness = $20\text{ ft}$ Porosity = 20% Water injection rate = $1000\text{ rb/day}$ Distance between injection and production well = $1000\text{ ft}$ Cumulative pore volume of water injected (PVWI) at breakthrough = 0.5 The time of breakthrough is ______ days (rounded off to one decimal place). [Use: 1 acre = $43560\text{ ft}^2$ and $1\text{ bbl} = 5.615\text{ ft}^3$]

Explanation

GATE→2025→Core→Reservoir Engineering

Q65

NAT[2 Marks]

An isotropic and homogeneous oil reservoir has a porosity of 20%, thickness of 20 ft and total compressibility of $15 \times 10^{-6}\text{ psi}^{-1}$. Variation of flowing bottomhole pressure ($p_{wf}$) with time ($t$) under pseudo steady state of a drawdown test in the well (under radial flow condition) is given as: $$p_{wf} = 2850 - 5t$$ where pressure is in psi and time is in hours. During the well test, the oil flow rate is $1800\text{ rb/day}$. The drainage area of the reservoir is ______ acres (rounded off to two decimal places). [Use: 1 acre = $43560\text{ ft}^2$]

Explanation

GATE→2024→Core→Reservoir Engineering

Q66

MCQ[1 Mark]

A constant composition expansion (CCE) test is conducted on a slightly compressible reservoir fluid sample in a pressure-volume-temperature (PVT) cell at $130^\circ\text{F}$. The relative fluid volume $(V/V_{sat})$ data is given. The bubble point pressure (psia) of the reservoir fluid is

(A)

2530

(B)

1650

(C)

1250

(D)

1095

Explanation

GATE→2024→Core→Reservoir Engineering

Q67

MCQ[1 Mark]

Which ONE of the following methods makes use of the centrifugal force for measuring the interfacial tension between two immiscible phases?

(A)

Pendant drop method

(B)

Spinning drop method

(C)

Du Noüy ring method

(D)

Wilhelmy plate method

Explanation

GATE→2024→Core→Reservoir Engineering

Q68

NAT[1 Mark]

Two reservoir sands A and B of same thickness are encountered in a well at different depths. The hydrocarbon in the shallow reservoir sand A is $10^\circ\text{API}$ whereas, in the deeper reservoir sand B, it is $20^\circ\text{API}$. For single phase incompressible systems, it may be assumed that the permeability in the deeper reservoir sand B is half of that of the shallow reservoir sand A, and the viscosity is directly proportional to the specific gravity of oil in respective sands. The ratio of the mobility in reservoir sand A to that of reservoir sand B is (round off to two decimal places).

Explanation

GATE→2024→Core→Reservoir Engineering

Q69

MCQ[2 Marks]

From the following figure, match the CORRECT set of liquid shrinkage curves from GROUP I with various crude oil systems from GROUP II. **GROUP I:** (P) Curve P (Q) Curve Q (R) Curve R (S) Curve S **GROUP II:** (I) High shrinkage crude oil (II) Low shrinkage crude oil (III) Ordinary black oil (IV) Near-critical crude oil

(A)

P-I; Q-II; R-III; S-IV

(B)

P-I; Q-III; R-IV; S-II

(C)

P-II; Q-III; R-I; S-IV

(D)

P-II; Q-IV; R-I; S-III

Explanation

GATE→2024→Core→Reservoir Engineering

Q70

MCQ[2 Marks]

Match the following pressure-volume-temperature (PVT) studies from GROUP I with their objectives from GROUP II. **GROUP I:** (P) Constant composition expansion (Q) Differential liberation (R) Separator test (S) Slim tube experiment **GROUP II:** (I) to determine the minimum miscibility pressure for gas injection (II) to determine the saturation pressure of the crude oil (III) to mimic the reservoir performance during production (IV) to design and optimize the separator conditions

(A)

P-III; Q-II; R-IV; S-I

(B)

P-III; Q-IV; R-I; S-II

(C)

P-II; Q-I; R-IV; S-III

(D)

P-II; Q-III; R-IV; S-I

Explanation

GATE→2024→Core→Reservoir Engineering

Q71

MCQ[2 Marks]

Hydrocarbon fluids usually are classified as dry gas, wet gas, gas condensate and black oil. Which ONE of the following combinations is the CORRECT pressure temperature phase diagram that represents the reservoir fluid type?

(A)

I-dry gas; II-wet gas; III-gas condensate; IV-black oil

(B)

I-dry gas; II-gas condensate; III-wet gas; IV-black oil

(C)

I-black oil; II-wet gas; III-gas condensate; IV-dry gas

(D)

I-gas condensate; II-black oil; III-wet gas; IV-dry gas

Explanation

GATE→2024→Core→Reservoir Engineering

Q72

MCQ[2 Marks]

Which ONE of the following is the CORRECT combination of dimensionless numbers and their force ratios? **Dimensionless Number:** (P) Froude Number (Q) Capillary Number (R) Reynolds Number (S) Bond Number **Ratio of Forces:** (I) Inertia/Gravity (II) Buoyancy/Capillary (III) Inertia/Viscous (IV) Viscous/Capillary

(A)

P-I; Q-IV; R-II; S-III

(B)

P-II; Q-IV; R-III; S-I

(C)

P-I; Q-IV; R-III; S-II

(D)

P-I; Q-III; R-II; S-IV

Explanation

GATE→2024→Core→Reservoir Engineering

Q73

MSQ[2 Marks]

Consider flow of two immiscible viscous fluids inside a thin slit of width $2B$. The flow rates of both the fluids are such that the planar interface is exactly at the center of the slit ($X=0$). Upper and lower boundaries are at $X=B$ and $X=-B$. $\tau_{XZ}^I$ and $\tau_{XZ}^{II}$ are shear stresses, $v_z^I$ and $v_z^{II}$ are velocities. Which of the following options represent(s) the CORRECT boundary condition(s)?

(A)

$|\tau_{XZ}^I| = |\tau_{XZ}^{II}|$ at $X=0$

(B)

velocity continuity at boundaries

(C)

no-slip condition at solid walls ($X=\pm B$)

(D)

shear stress continuity across fluid-fluid interface

Explanation

GATE→2024→Core→Reservoir Engineering

Q74

NAT[2 Marks]

Porosity and oil saturation of various core samples retrieved from a layered reservoir are given below along with layer thicknesses. Assuming uniform area of cross section for all the layers, the average oil saturation of the reservoir is ______ % (round off to one decimal place). [Layer 1: h=1.0 ft, phi=10%, So=60% Layer 2: h=1.5 ft, phi=15%, So=65% Layer 3: h=2.0 ft, phi=20%, So=70% Layer 4: h=2.5 ft, phi=25%, So=75%]

Explanation

GATE→2024→Core→Reservoir Engineering

Q75

NAT[2 Marks]

A natural gas has the following composition: - $CO_2$: mole fraction 0.02, $M = 44$ - $CH_4$: mole fraction 0.93, $M = 16$ - $C_2H_6$: mole fraction 0.03, $M = 30$ - $C_3H_8$: mole fraction 0.02, $M = 44$ Assume $Z = 0.82$, $R = 10.73\text{ psia}\cdot\text{ft}^3/(lb\text{-mole}\cdot^\circ\text{R})$. Density at 2000 psia and $150^\circ\text{F}$ ($610^\circ\text{R}$) is ______ $\text{lb/ft}^3$ (round off to two decimal places).

Explanation

GATE→2024→Core→Reservoir Engineering

Q76

NAT[2 Marks]

Consider the displacement of oil by water through a 1D porous medium. $k_{ro}^0 = 0.8$, $k_{rw}^0 = 0.3$, $S_{or} = 0.35$, $S_{wr} = 0.25$, $\mu_w = 1\text{ cP}$, $\mu_o = 8\text{ cP}$. Normalized water saturation $S_w^* = \frac{S_w - S_{wr}}{1 - S_{or} - S_{wr}}$. Relative permeabilities: $k_{ro} = k_{ro}^0(1 - S_w^*)$, $k_{rw} = k_{rw}^0 S_w^*$. The mobility ratio corresponding to $S_w = 0.6$ is (round off to one decimal place).

Explanation

GATE→2023→Core→Reservoir Engineering

Q77

MCQ[1 Mark]

Which of the following relations defines the coefficient of isothermal compressibility ($C_g$) for a gas? (Here, $p, T$, and $v$ represent pressure, temperature, and volume)

(A)

$C_g = -\frac{1}{v} \left(\frac{\partial v}{\partial p}\right)_T$

(B)

$C_g = -\frac{1}{v} \left(\frac{\partial p}{\partial v}\right)_T$

(C)

$C_g = -\frac{1}{p} \left(\frac{\partial v}{\partial p}\right)_T$

(D)

$C_g = -\frac{1}{p} \left(\frac{\partial p}{\partial v}\right)_T$

Explanation

GATE→2023→Core→Reservoir Engineering

Q78

MCQ[1 Mark]

Consider an ideal liquid-vapor mixture at equilibrium having liquid phase mole fraction $x_i$ and gas phase mole fraction $y_i$. For an ideal solution (Raoult's law), the equilibrium ratio ($k_i$) is given by

(A)

$k_i = \frac{x_i}{y_i} = \frac{P_{vi}}{P}$

(B)

$k_i = \frac{x_i}{y_i} = \frac{P}{P_{vi}}$

(C)

$k_i = \frac{y_i}{x_i} = \frac{P_{vi}}{P}$

(D)

$k_i = \frac{y_i}{x_i} = \frac{P}{P_{vi}}$

Explanation

GATE→2023→Core→Reservoir Engineering

Q79

MCQ[1 Mark]

Contact angle measurements are performed on smooth surfaces. The interfacial tensions between solid-liquid, liquid-air, and air-solid are $\gamma_{SL}$, $\gamma_{LA}$, and $\gamma_{AS}$, respectively. Which of the following expressions describes Young's equation for the contact angle, $\Theta$?

(A)

$\cos \Theta = \frac{\gamma_{AS} - \gamma_{SL}}{\gamma_{LA}}$

(B)

$\cos \Theta = \frac{\gamma_{SL} - \gamma_{AS}}{\gamma_{LA}}$

(C)

$\cos \Theta = \frac{\gamma_{LA} - \gamma_{AS}}{\gamma_{SL}}$

(D)

$\cos \Theta = \frac{\gamma_{LA} - \gamma_{SL}}{\gamma_{AS}}$

Explanation

GATE→2023→Core→Reservoir Engineering

Q80

MSQ[1 Mark]

The mean free path of the gas molecule is $10^{-6}\text{ mm}$, while the pore size of the rock is $10^{-3}\text{ mm}$. Which of the following statements is TRUE?

(A)

The Knudsen number is $10^3$ and the continuum principle would be applicable

(B)

The Knudsen number is $10^{-3}$ and the continuum principle would be applicable

(C)

The Knudsen number is $10^3$ and the continuum principle would not be applicable

(D)

The Knudsen number is $10^{-3}$ and the continuum principle would not be applicable

Explanation

GATE→2023→Core→Reservoir Engineering

Q81

MCQ[2 Marks]

Match the organic solid phase deposition regions (I, II, III) around the bubble point curve with Wax, Hydrate, and Asphaltene.

(A)

I - Wax; II - Hydrate; III - Asphaltene

(B)

I - Hydrate; II - Asphaltene; III - Wax

(C)

I - Asphaltene; II - Hydrate; III - Wax

(D)

I - Hydrate; II - Wax; III - Asphaltene

Explanation

GATE→2023→Core→Reservoir Engineering

Q82

NAT[2 Marks]

Consider the flow of oil and water in a 1D porous medium, with $k_{ro}^o = 1$, $k_{rw}^o = 0.2$, $S_{wr} = 0.2$, $S_{or} = 0.4$, $\mu_o = 5 \text{ cP}$, $\mu_w = 1 \text{ cP}$. The total relative mobility ($\lambda_{total} = k_{ro}/\mu_o + k_{rw}/\mu_w$) at $S_w = 0.4$ is $\text{cP}^{-1}$ (rounded to one decimal place).

Explanation

GATE→2023→Core→Reservoir Engineering

Q83

NAT[2 Marks]

A binary mixture of n-butane ($C_4H_{10}$) and n-pentane ($C_5H_{12}$) is at $180^\circ\text{F}$ and $95 \text{ psia}$. Vapor pressures are $160 \text{ psia}$ and $54 \text{ psia}$, respectively. Assuming ideal solution behavior (Raoult's and Dalton's laws), the mole fraction of n-butane in the gas phase is (rounded to three decimal places).

Explanation

GATE→2023→Core→Reservoir Engineering

Q84

NAT[2 Marks]

A highly permeable reservoir with initial pressure of $3000 \text{ psi}$ is under active water drive. Stabilized pressure is $2500 \text{ psi}$. Oil production rate = $30,000 \text{ STB/day}$, water production = 0, $B_o = 1.5 \text{ bbl/STB}$, $B_g = 0.0007 \text{ bbl/scf}$, $B_w = 1$, $GOR = 850 \text{ scf/STB}$, $R_s = 700 \text{ scf/scf}$? (Given $R_s = 700 \text{ scf/STB}$). The water influx rate is bbl/day (rounded to nearest integer).

Explanation

GATE→2023→Core→Reservoir Engineering

Q85

NAT[2 Marks]

A volumetric undersaturated solution gas drive reservoir has initial water saturation of 15% (unchanged). After production of 10% of initial oil ($N_p = 0.1 N$), $B_o$ changes from $1.4$ to $1.2 \text{ bbl/STB}$. The final gas saturation in percentage is (rounded to one decimal place).

Explanation

GATE→2023→Core→Reservoir Engineering

Q86

NAT[2 Marks]

An oil droplet is to be mobilized by water injection. Rear radius of curvature $r_A = 25 \times 10^{-6} \text{ m}$, forward radius of curvature $r_B = 5 \times 10^{-6} \text{ m}$, wetting contact angle = $0^\circ$, interfacial tension $\sigma = 0.025 \text{ N/m}$. The magnitude of the minimum capillary pressure drop required to mobilize the droplet is $\text{N/m}^2$ (rounded to nearest integer).

Explanation

GATE→2022→Core→Reservoir Engineering

Q87

MCQ[1 Mark]

The formation volume factors of oil and water are $B_o$ and $B_w$. The CORRECT relationship between surface water cut ($f_{ws}$) and reservoir water cut ($f_w$) is

(A)

$f_{ws} = \frac{B_o f_w}{B_w + B_o}$

(B)

$f_{ws} = \frac{B_o f_w}{B_w + B_o f_w}$

(C)

$f_{ws} = \frac{B_w}{B_o(\frac{1}{f_w}-1) + B_w}$

(D)

$f_{ws} = \frac{B_o}{B_w(\frac{1}{f_w}-1) + B_o}$

Explanation

GATE→2022→Core→Reservoir Engineering

Q88

MCQ[1 Mark]

The liquid shrinkage curves for different types of crude oil are shown. Which curve represents the Black Oil?

(A)

I

(B)

II

(C)

III

(D)

IV

Explanation

GATE→2022→Core→Reservoir Engineering

Q89

NAT[1 Mark]

A reservoir produces oil at $7000 \text{ stb/day}$ with producing GOR = $2000 \text{ scf/stb}$. Maintained at $2500 \text{ psi}$ by water injection. Given $B_o = 1.2 \text{ rb/stb}$, $B_w = 1.0 \text{ rb/stb}$, $B_g = 0.0012 \text{ rb/scf}$, solution $R_s = 300 \text{ scf/stb}$. The water injection rate (stb/day) required is (rounded off to nearest integer).

Explanation

GATE→2022→Core→Reservoir Engineering

Q90

MCQ[2 Marks]

Capillary pressure ($P_c$) vs water saturation ($S_w$) curves for different sandstone reservoirs (I, II, III, and IV) are given. Which reservoir has the most uniform pore size distribution (indicated by a flat/plateau-like median portion)?

(A)

I

(B)

II

(C)

III

(D)

IV

Explanation

GATE→2022→Core→Reservoir Engineering

Q91

NAT[2 Marks]

During core analysis, lab conditions: $\sigma_{lab} = 35 \text{ dynes/cm}$, $\phi_{lab} = 30\%$, $k_{lab} = 100 \text{ mD}$, $P_{c,lab} = 50 \text{ psi}$. Reservoir conditions: $\sigma_{res} = 25 \text{ dynes/cm}$, $\phi_{res} = 25\%$, $k_{res} = 80 \text{ mD}$. The calculated capillary pressure at reservoir condition using Leverett J-function is psi (rounded off to two decimal places).

Explanation

GATE→2022→Core→Reservoir Engineering

Q92

NAT[2 Marks]

An incompressible fluid (density $\rho = 40 \text{ lb/ft}^3$) flows through a linear porous media: $L = 1500 \text{ ft}$, $k = 150 \text{ mD}$, $H = 15 \text{ ft}$, $\mu = 1.5 \text{ cP}$, $P_1 = 1600 \text{ psi}$, $P_2 = 1590 \text{ psi}$, width $W = 30 \text{ ft}$, dip angle $\theta$. The absolute difference between actual fluid interstitial velocity at $\theta = 0^\circ$ and $\theta = 10^\circ$ is (rounded off to three decimal places).

Explanation

GATE→2022→Core→Reservoir Engineering

Q93

NAT[2 Marks]

A 1 kg-mol bottled gas mixture ($50\%$ Ethane, $45\%$ n-Butane, $5\%$ Propane) is at $30^\circ\text{C}$. Vapor pressures are Ethane $10 \text{ bar}$, n-Butane $40 \text{ bar}$, Propane $3 \text{ bar}$. Equilibrium vapor mole composition of n-Butane in mol% is (rounded to two decimal places).

Explanation

Petroleum Production Operations

37 Questions

GATE→2026→Core→Petroleum Production Operations

Q94

MCQ[1 Mark]

Which of the following has the most proppant carrying capacity during hydraulic fracturing process?

(A)

Pentane

(B)

Cross-linked gel

(C)

Slickwater

(D)

Untreated formation brine

Explanation

GATE→2026→Core→Petroleum Production Operations

Q95

MSQ[1 Mark]

Which of the following improve(s) the productivity index of a vertical well in an oil reservoir?

(A)

Hydraulic fracturing

(B)

Increasing the perforation length

(C)

Increasing the skin factor

(D)

Reducing the oil viscosity by steam injection

Explanation

GATE→2026→Core→Petroleum Production Operations

Q96

MSQ[1 Mark]

Which of the following methods is/are used to separate water from crude oil-water emulsion?

(A)

Heating

(B)

Centrifugation

(C)

Addition of interfacial tension reducing agents

(D)

Electrostatic coalescence

Explanation

GATE→2026→Core→Petroleum Production Operations

Q97

MCQ[2 Marks]

The sectional view of three different damaged regions (marked as P, Q and R) near the vicinity of a perforation is shown in the figure. Choose the correct option by matching the entries in GROUP X with corresponding terms in GROUP Y. **GROUP X:** P, Q, R **GROUP Y:** (I) Grain fracturing (II) Charge and core debris (III) Compacted pulverized zone

(A)

P-I; Q-II; R-III

(B)

P-II; Q-III; R-I

(C)

P-I; Q-III; R-II

(D)

P-II; Q-I; R-III

Explanation

GATE→2026→Core→Petroleum Production Operations

Q98

MSQ[2 Marks]

Which of the following statements is/are CORRECT about the skin factor?

(A)

Successful hydraulic fracturing increases the skin factor.

(B)

Successful hydraulic fracturing decreases the skin factor.

(C)

Formation damage near wellbore increases the skin factor.

(D)

Formation damage near wellbore decreases the skin factor.

Explanation

GATE→2026→Core→Petroleum Production Operations

Q99

NAT[2 Marks]

The Inflow Performance Relationship (IPR) for a vertical well in a single-phase oil reservoir was found to be linear. The flowing bottomhole pressures are 4000 psi and 1000 psi at oil flow rates of 200 STB/day and $600 \text{ STB/day}$ respectively. At the flowing bottomhole pressure of 2875 psi, the value of flow rate (in STB/day) is

Explanation

GATE→2026→Core→Petroleum Production Operations

Q100

NAT[2 Marks]

A matrix acidizing job is planned on a sandstone pay zone at a depth of 7000 ft without formation breakdown by keeping a safety margin of 250 psi with the help of a coil tubing unit. Consider the fracture gradient of $0.7 \text{ psi/ft}$, average specific gravity of the injection fluid as 1.065, and frictional pressure drop of 200 psi. The maximum surface injection pressure (in psi) is [Given: Hydrostatic gradient (psi/ft) = $0.433 \times \text{Specific Gravity}$]

Explanation

GATE→2026→Core→Petroleum Production Operations

Q101

NAT[2 Marks]

A conventional Sucker Rod Pumping (SRP) unit is being used for lifting 25 °API oil from a depth of 5000 ft. The maximum and minimum values of polished rod loads are 14300 lbf and 5200 lbf, respectively. The ideal counter balance load (in lbf) is

Explanation

GATE→2025→Core→Petroleum Production Operations

Q102

MCQ[1 Mark]

The primary objective of the electrostatic grid in electrostatic heater-treater used in crude oil processing is to

(A)

separate sand particles.

(B)

promote coalescence of water droplets.

(C)

generate electrical energy from the kinetic energy of the feed.

(D)

prevent corrosion by the cathodic protection.

Explanation

GATE→2025→Core→Petroleum Production Operations

Q103

MCQ[1 Mark]

The maximum Polished Rod Load (PRL) in the operation of the sucker rod pump is observed near the

(A)

top of the stroke and the traveling valve is open.

(B)

top of the stroke and the traveling valve is closed.

(C)

bottom of the stroke and the traveling valve is open.

(D)

bottom of the stroke and the traveling valve is closed.

Explanation

GATE→2025→Core→Petroleum Production Operations

Q104

MCQ[1 Mark]

Match the entries in GROUP I with the entries in GROUP II. **GROUP I:** (P) Liquid hold-up (Q) Liquid carryover (R) Gas blowby (S) Gas dehydration **GROUP II:** (I) Water removal (II) Free gas escaping with liquid phase (III) Free liquid escaping with gas phase (IV) Fraction of pipe volume occupied by liquid

(A)

P-III; Q-IV; R-I; S-II

(B)

P-IV; Q-III; R-II; S-I

(C)

P-I; Q-II; R-IV; S-III

(D)

P-IV; Q-II; R-III; S-I

Explanation

GATE→2025→Core→Petroleum Production Operations

Q105

MSQ[1 Mark]

Which of the following statement(s) is/are CORRECT about the chemicals used for the processing of sour crude oil and natural gas?

(A)

Amine solutions cannot be regenerated after removal of $H_2S$ from natural gas.

(B)

Amine solutions in liquid form absorb $H_2S$ from natural gas.

(C)

Glycols become corrosive in the presence of oxygen.

(D)

Iron sponges cannot be used for $H_2S$ removal.

Explanation

GATE→2025→Core→Petroleum Production Operations

Q106

NAT[2 Marks]

A hydraulically fractured vertical well has fracture permeability of $4000\text{ mD}$, reservoir permeability of $80\text{ mD}$, fracture width of $0.12\text{ in}$, and fracture half-length of $1000\text{ ft}$. Dimensionless fracture conductivity is ______ $\times 10^{-4}$ (rounded off to one decimal place).

Explanation

GATE→2025→Core→Petroleum Production Operations

Q107

NAT[2 Marks]

An electrical submersible pump is to be installed to lift oil of $30^\circ\text{API}$ in a $10000\text{ ft}$ deep well. The oil formation volume factor ($B_o$) is $1.25\text{ rb/stb}$. The desired flow rate is $8000\text{ stb/day}$. Minimum suction pressure of the chosen pump is 200 psi. Inflow performance relationship shows a flowing bottomhole pressure of 2820 psi at the desired flow rate. Assuming casing pressure and weight of the gas in the annulus to be negligible, the minimum pump setting depth is ______ ft (rounded off to one decimal place).

Explanation

GATE→2025→Core→Petroleum Production Operations

Q108

NAT[2 Marks]

A production tubing string of length $1500\text{ m}$ is tightly held by packers to prevent any expansion in either direction. Production of hot gases from the reservoir increases the temperature of the tubing by $20^\circ\text{C}$. The Young's modulus of elasticity of the tubing material is $3000\text{ N/m}^2$, and the linear coefficient of thermal expansion is $5 \times 10^{-6}$ per °C. Assuming no radial expansion, and neglecting the weight of the gas in the tubing and its viscosity, the increase in the stress of the tubing due to temperature rise is ______ $\text{N/m}^2$ (rounded off to two decimal places).

Explanation

GATE→2024→Core→Petroleum Production Operations

Q109

MCQ[1 Mark]

Absolute open flow potential of a well is the

(A)

maximum theoretical flow rate of reservoir fluid that a well can deliver.

(B)

minimum theoretical flow rate of reservoir fluid that a well can deliver.

(C)

flow rate of reservoir fluid from a well when the sandface pressure is 100 psia.

(D)

minimum flow rate of reservoir fluid when a well is stimulated.

Explanation

GATE→2024→Core→Petroleum Production Operations

Q110

MCQ[1 Mark]

Gas-liquid flow regimes for horizontal pipelines are shown below. Identify the correct pair from the list given below.

(A)

I-Stratified; II-Slug; III-Annular; IV-Bubbly

(B)

I-Slug; II-Bubbly; III-Annular; IV-Stratified

(C)

I-Annular; II-Slug; III-Stratified; IV-Bubbly

(D)

I-Slug; II-Stratified; III-Bubbly; IV-Annular

Explanation

GATE→2024→Core→Petroleum Production Operations

Q111

MCQ[1 Mark]

Which ONE of the following can result in a negative value of skin factor near the wellbore?

(A)

Hydraulic fracturing

(B)

Fines migration

(C)

Asphaltene deposition

(D)

Clay swelling

Explanation

GATE→2024→Core→Petroleum Production Operations

Q112

MSQ[2 Marks]

Fixed roof tank for storage of organic liquids reduces volatile organic compound (VOC) emissions... The objective(s) of such a vent is/are to

(A)

control pressure build-up in the tank.

(B)

control vacuum generation in the tank.

(C)

add oil to the tank.

(D)

add water to the tank.

Explanation

GATE→2024→Core→Petroleum Production Operations

Q113

MSQ[2 Marks]

A choke is generally installed at the well head and/or downhole. The desired function(s) of the choke is/are to

(A)

protect surface equipment from damage.

(B)

avoid sand ingress problem.

(C)

regulate production rate.

(D)

ensure oil and water coning.

Explanation

GATE→2024→Core→Petroleum Production Operations

Q114

MSQ[2 Marks]

Which of the following options is/are CORRECT about the below mentioned hydrocarbons? LNG: Liquefied Natural Gas; LPG: Liquefied Petroleum Gas; NGL: Natural Gas Liquid; CNG: Compressed Natural Gas

(A)

LNG is primarily methane at approximately 110 K temperature

(B)

LPG is primarily propane and butane at standard temperature and pressure

(C)

NGL is primarily methane at standard temperature and pressure

(D)

CNG is primarily pentane at standard temperature and pressure

Explanation

GATE→2024→Core→Petroleum Production Operations

Q115

NAT[2 Marks]

An ideal mixture of benzene and toluene is in equilibrium at a pressure of $750\text{ mm Hg}$ and temperature of $90^\circ\text{C}$. The concentration of benzene in the vapour phase in mole fraction is (round off to two decimal places). [Given Antoine equation: $\log_{10} P_i^0 = A_i - \frac{B_i}{T + C_i}$ with $T$ in $^\circ\text{C}$]

Explanation

GATE→2024→Core→Petroleum Production Operations

Q116

NAT[2 Marks]

The invasion of a drilling fluid to a radius of $3\text{ ft}$ from the center of the wellbore into the formation has resulted in the development of skin. Permeability of the damaged skin zone is $50\text{ mD}$, unaffected formation permeability is $400\text{ mD}$, and wellbore radius is $0.25\text{ ft}$. The value of the skin factor is (round off to two decimal places).

Explanation

GATE→2023→Core→Petroleum Production Operations

Q117

MCQ[1 Mark]

Which of the following is the primary role of proppants in hydraulic fracturing?

(A)

Keep the fractures open during production

(B)

Decrease the viscosity of fracturing fluid

(C)

Decrease the density of fracturing fluid

(D)

Reduce the viscosity of crude oil in reservoir

Explanation

GATE→2023→Core→Petroleum Production Operations

Q118

MSQ[1 Mark]

Which is/are the thermodynamic inhibitor(s) for natural gas hydrate?

(A)

Tetrahydrofuran

(B)

Sodium chloride

(C)

Ethylene glycol

(D)

Tetra n-butyl ammonium bromide

Explanation

GATE→2023→Core→Petroleum Production Operations

Q119

MCQ[2 Marks]

A centrifugal pump running at $500 \text{ rpm}$ delivers $60 \text{ liters/minute}$ with a head of $50 \text{ m}$. At the same efficiency, if the rotational speed is increased to $1000 \text{ rpm}$, the discharge rate and head would respectively be

(A)

$120 \text{ liters/minute}$ and 200 m

(B)

$120 \text{ liters/minute}$ and 100 m

(C)

$60 \text{ liters/minute}$ and 200 m

(D)

$60 \text{ liters/minute}$ and 100 m

Explanation

GATE→2023→Core→Petroleum Production Operations

Q120

MCQ[2 Marks]

Match the pure gas hydrate phase diagrams (I, II, III, IV) with the corresponding gases: $CH_4$, $CO_2$, $H_2S$, and $N_2$.

(A)

$I-CH_4; II-N_2; III-CO_2; IV-H_2S$

(B)

$I-H_2S; II-CH_4; III-CO_2; IV-N_2$

(C)

$I-N_2; II-CH_4; III-H_2S; IV-CO_2$

(D)

$I-N_2; II-CH_4; III-CO_2; IV-H_2S$

Explanation

GATE→2023→Core→Petroleum Production Operations

Q121

NAT[2 Marks]

Crude oil ($\rho = 850 \text{ kg/m}^3$, $\mu = 2 \times 10^{-3} \text{ Pa}\cdot\text{s}$) flows at $V = 0.35 \text{ m/s}$ through a horizontal capillary tube ($D = 2.5 \times 10^{-3} \text{ m}$, $L = 0.30 \text{ m}$). With Fanning friction factor $f = 16 / Re$, the pressure drop across the capillary tube is Pa (rounded to one decimal place).

Explanation

GATE→2023→Core→Petroleum Production Operations

Q122

NAT[2 Marks]

A shell and tube heat exchanger cools crude oil ($3650 \text{ kg/h}$, $C_p = 2.5 \text{ kJ/kg}\cdot\text{K}$) from $400 \text{ K}$ to $360 \text{ K}$. Water ($1600 \text{ kg/h}$, $C_p = 4.187 \text{ kJ/kg}\cdot\text{K}$) enters at $310 \text{ K}$. Countercurrent flow, $U = 300 \text{ W/m}^2\cdot\text{K}$. The heat transfer area required is $\text{m}^2$ (rounded to one decimal place).

Explanation

GATE→2022→Core→Petroleum Production Operations

Q123

MCQ[1 Mark]

The general production decline equation is $\frac{1}{q} \frac{dq}{dt} = -b q^d$. Match the value of $d$ (Group 1: I. $d=0$, II. $d=1$, III. $0<d<1$) with decline types (Group 2: P. Harmonic, Q. Exponential, R. Hyperbolic).

(A)

I-P; II-Q; III-R

(B)

II-R; I-P; III-Q

(C)

III-P; I-Q; II-R

(D)

I-Q; II-P; III-R

Explanation

GATE→2022→Core→Petroleum Production Operations

Q124

MCQ[1 Mark]

In project economic evaluation, present value of cash flow discounted at rate $i$ over $m$ years with annual incremental revenue $\Delta R_n$ is given by

(A)

$NPV_R = \sum_{n=1}^m \frac{(1+i)^n}{\Delta R_n}$

(B)

$NPV_R = \sum_{n=1}^m \frac{\Delta R_n}{(1+i)^{n-1}}$

(C)

$NPV_R = \sum_{n=1}^m [\frac{\Delta R_n}{1+i}]^n$

(D)

$NPV_R = \sum_{n=1}^m \frac{\Delta R_n}{(1+i)^n}$

Explanation

GATE→2022→Core→Petroleum Production Operations

Q125

MCQ[1 Mark]

Which ONE of the following is used to anchor and support a packer against the casing while expanding its rubber sealing element?

(A)

Blast joints

(B)

Slips

(C)

Landing nipples

(D)

Side pocket mandrels

Explanation

GATE→2022→Core→Petroleum Production Operations

Q126

MSQ[1 Mark]

Which of the following statements are NOT CORRECT during the operating cycle of a 'sucker rod pump'?

(A)

Standing valve is open during the upward stroke.

(B)

Standing valve is closed during the upward stroke.

(C)

Travelling valve is closed during the upward stroke.

(D)

Travelling valve is open during the upward stroke.

Explanation

GATE→2022→Core→Petroleum Production Operations

Q127

MCQ[2 Marks]

A brine solution is injected downward through tubing of diameter $d$ inclined at angle $\theta$ from vertical. The condition such that the ratio of frictional pressure drop to gravitational pressure drop equals $4f$ (where $f$ is Fanning friction factor) is

(A)

$u = (2gd)^{1/2}$; $\theta = 30^\circ$

(B)

$u = gd$; $\theta = 30^\circ$

(C)

$u = (gd)^{1/2}$; $\theta = 60^\circ$

(D)

$u = gd^{1/2}$; $\theta = 30^\circ$

Explanation

GATE→2022→Core→Petroleum Production Operations

Q128

NAT[2 Marks]

An oil well ($r_w = 0.5 \text{ in} = 0.04167 \text{ ft}$) in a heavy oil reservoir ($r_e = 745 \text{ ft}$, $\mu_1 = 500 \text{ cP}$) operates at $q = 200 \text{ rb/day}$ and $P_{wf} = 150 \text{ psi}$ under steady state. Steam stimulation reduces viscosity to $\mu_2 = 35 \text{ cP}$ in the stimulated zone up to $r_s = 65 \text{ ft}$. The new production rate at downhole conditions is rb/day (rounded off to two decimal places).

Explanation

GATE→2022→Core→Petroleum Production Operations

Q129

NAT[2 Marks]

In a horizontal circular pipe, liquid and gas flow concurrently at the same superficial velocity $u_{sl} = u_{sg} = u_s$. The average gas velocity $u_g$ is greater than liquid velocity $u_l$. If slip velocity $u_s = u_g - u_l$ equals the superficial velocity of each phase ($u_s$), the fractional liquid holdup $H_l$ is (rounded to two decimal places).

Explanation

GATE→2022→Core→Petroleum Production Operations

Q130

NAT[2 Marks]

Crude oil ($\dot{m}_o = 1000 \text{ kg/hr}$, $C_{po} = 2 \text{ kJ/kg}\cdot\text{K}$) is cooled from $80^\circ\text{C}$ to $40^\circ\text{C}$ using water ($\dot{m}_w$, $C_{pw} = 4.2 \text{ kJ/kg}\cdot\text{K}$) entering at $20^\circ\text{C}$ and leaving at $40^\circ\text{C}$ in counter-flow. Overall heat transfer coefficient $U = 0.25 \text{ kW/m}^2\cdot\text{K}$. The minimum heat exchanger area ($m^2$) is (rounded off to two decimal places).

Explanation

Offshore Drilling and Production Practices

16 Questions

GATE→2026→Core→Offshore Drilling and Production Practices

Q131

MCQ[1 Mark]

Which of the following statements is NOT CORRECT in the context of offshore operational environment?

(A)

The motion of ocean's surface can be due to energy transfer from wind to water.

(B)

Lunar tides are caused by the moon.

(C)

Solar tides are caused by the sun.

(D)

The motion of ocean's surface can be due to energy transfer from water to wind.

Explanation

GATE→2026→Core→Offshore Drilling and Production Practices

Q132

MSQ[1 Mark]

Which of the following statements is/are CORRECT about the water injection well platforms?

(A)

These are meant for injection of gas through the injection well.

(B)

Metering devices are not required to determine injection rate of injection wells.

(C)

Metering devices are required to determine injection rate of injection wells.

(D)

Firefighting and life-saving equipment should be present on the platform.

Explanation

GATE→2026→Core→Offshore Drilling and Production Practices

Q133

MSQ[1 Mark]

Which of the following statements is/are CORRECT about the floating production, storage, and offloading systems (FPSOs)?

(A)

Existing tankers cannot be converted into FPSOs.

(B)

FPSOs can be selected in the absence of any pipeline infrastructure.

(C)

FPSOs cannot process the produced fluids.

(D)

FPSOs can be used for the storage of produced crude oil.

Explanation

GATE→2025→Core→Offshore Drilling and Production Practices

Q134

MSQ[1 Mark]

Which of the following offshore drilling platform(s) has/have legs on the seabed?

(A)

Jack up

(B)

Tension leg

(C)

Concrete gravity

(D)

Semi-submersible

Explanation

GATE→2025→Core→Offshore Drilling and Production Practices

Q135

MCQ[2 Marks]

A stationary tank is cylindrical in shape with two hemispherical ends and is horizontal, as shown in the figure. $R$ is the radius of the cylinder as well as of the hemispherical ends. The tank is half filled with an oil of density $\rho$ and the rest of the space in the tank is occupied by air. The air pressure, inside the tank as well as outside it, is atmospheric. The acceleration due to gravity ($g$) acts vertically downward. The net horizontal force applied by the oil on the right hemispherical end (shown by the bold outline in the figure) is

(A)

$\frac{1}{2} \rho g R^3$

(B)

$\frac{2}{3} \rho g R^3$

(C)

$\frac{3}{4} \rho g R^3$

(D)

$\frac{1}{3} \rho g R^3$

Explanation

GATE→2024→Core→Offshore Drilling and Production Practices

Q136

MCQ[1 Mark]

The speed of Tsunami is a function of

(A)

only water depth.

(B)

only wave height.

(C)

both water depth and wave height.

(D)

both wind speed and wave height.

Explanation

GATE→2024→Core→Offshore Drilling and Production Practices

Q137

MCQ[1 Mark]

Which ONE of the following is a POSITIVELY BUOYANT floating structure?

(A)

Jacket Platform

(B)

Semi-Submersible

(C)

Tension Leg Platform

(D)

Barge

Explanation

GATE→2024→Core→Offshore Drilling and Production Practices

Q138

MCQ[2 Marks]

From the standard flexible riser configurations shown schematically in the figure, choose the CORRECT combination.

(A)

I-Steep Wave; II-Lazy Wave; III-Steep S; IV-Lazy S

(B)

I-Lazy Wave; II-Steep Wave; III-Lazy S; IV-Steep S

(C)

I-Tethered Wave; II-Tethered S; III-Steep S; IV-Lazy S

(D)

I-Steep Wave; II-Lazy Wave; III-Tethered S; IV-Tethered Wave

Explanation

GATE→2024→Core→Offshore Drilling and Production Practices

Q139

NAT[2 Marks]

The diameter and draft of a freely floating classical upright spar without moonpool is $30\text{ m}$ and $75\text{ m}$, respectively. The added mass in heave mode is 1.8 times the mass of the spar. The critical damping of the spar in heave mode is ______ $\times 10^6\text{ kg/s}$ (round off to one decimal place).

Explanation

GATE→2024→Core→Offshore Drilling and Production Practices

Q140

NAT[2 Marks]

A long vertical hollow steel pipe used as a column in an offshore structure follows Euler's column theory. The length, outer diameter and thickness of the pipe are $30\text{ m}$, $0.50\text{ m}$, and $0.03\text{ m}$, respectively. The Euler buckling load (assuming no environmental loads) of the pipe pinned at both the ends, is ______ kN (round off to one decimal place).

Explanation

GATE→2023→Core→Offshore Drilling and Production Practices

Q141

MCQ[1 Mark]

Which of the following offshore rigs has the HIGHEST water depth operating capability?

(A)

Submersible drilling barge

(B)

Jackup rig

(C)

Jacket platform

(D)

Semi-submersible rig

Explanation

GATE→2023→Core→Offshore Drilling and Production Practices

Q142

NAT[2 Marks]

Figure shows an inextensible catenary mooring cable in still water. Submerged weight per unit length $w = 100 \text{ kg/m}$, anchor radius $x = 50 \text{ m}$, horizontal tension $T_h = 1600 \text{ kg}$. The catenary length (AB) is m (rounded to two decimal places).

Explanation

GATE→2023→Core→Offshore Drilling and Production Practices

Q143

NAT[2 Marks]

An empty steel pipeline with massless endcaps has an outer diameter $D$ and thickness $t$. Steel density $\rho_s = 7850 \text{ kg/m}^3$, seawater density $\rho_w = 1025 \text{ kg/m}^3$. The critical $D/t$ ratio at which the pipeline starts floating is (rounded to two decimal places).

Explanation

GATE→2023→Core→Offshore Drilling and Production Practices

Q144

NAT[2 Marks]

A four-column semi-submersible floater has column diameter $D = 5 \text{ m}$ each ($N = 4$ columns). Total displaced weight = $4000 \text{ tonnes} = 4 \times 10^6 \text{ kg}$. Added mass = 50% of mass ($m_a = 0.5 m$), $\rho_w = 1025 \text{ kg/m}^3$, $g = 9.81 \text{ m/s}^2$. The natural period of oscillation in heave mode is seconds (rounded to one decimal place).

Explanation

GATE→2023→Core→Offshore Drilling and Production Practices

Q145

NAT[2 Marks]

An underwater riser with outer diameter $D_o = 250 \text{ mm}$ and wall thickness $t = 20 \text{ mm}$ (inner diameter $D_i = 210 \text{ mm}$) is subjected to effective tension $T_{eff} = 1200 \text{ kN}$, internal pressure $P_i = 25 \text{ MPa}$, and external pressure $P_o = 6 \text{ MPa}$. The true wall tension in the riser is (in $\times 10^6 \text{ N}$, rounded to two decimal places).

Explanation

GATE→2022→Core→Offshore Drilling and Production Practices

Q146

MCQ[1 Mark]

'Cupola' offshore storage tank is an example of

(A)

floating storage type.

(B)

above-water storage type.

(C)

submerged storage type.

(D)

platform storage type.

Explanation

Petroleum Formation Evaluation

29 Questions

GATE→2026→Core→Petroleum Formation Evaluation

Q147

MSQ[1 Mark]

For a radioactive material, if $N$ is the number of nuclei present at time $t$, and $\lambda$ is decay constant, then which of the following is/are CORRECT representation(s) of the rate of decay?

(A)

$-\frac{dN}{dt} = \lambda N^2$

(B)

$-\frac{dN}{dt} = \lambda N$

(C)

$-\frac{dN}{dt} = \frac{\lambda}{N^2}$

(D)

$-\frac{dN}{dt} = \frac{\lambda}{N}$

Explanation

GATE→2026→Core→Petroleum Formation Evaluation

Q148

MSQ[1 Mark]

Which of the following logging methods is/are NOT used for investigation in Cement Bond Logging (CBL)?

(A)

Gamma ray

(B)

Neutron

(C)

Electrical

(D)

Acoustic wave

Explanation

GATE→2026→Core→Petroleum Formation Evaluation

Q149

MCQ[2 Marks]

Which of the following "logging methods" in a borehole will provide the highest depth of investigation for a given marine formation?

(A)

Neutron

(B)

Sonic

(C)

Density

(D)

Resistivity

Explanation

GATE→2026→Core→Petroleum Formation Evaluation

Q150

MSQ[2 Marks]

Which of the following approaches is/are used to get the response of Formation Micro Scanner (FMS) log?

(A)

Optical

(B)

Electrical

(C)

Thermal

(D)

Nuclear

Explanation

GATE→2026→Core→Petroleum Formation Evaluation

Q151

MSQ[2 Marks]

Which of the following conditions is/are inferred using cross plots of neutron porosity $\phi_N$ and density porosity $\phi_D$?

(A)

Gas zone

(B)

Shale distribution

(C)

Water zone

(D)

Oil zone

Explanation

GATE→2026→Core→Petroleum Formation Evaluation

Q152

NAT[2 Marks]

For a given reservoir of porosity, $\phi = 0.1$, the water saturation is equal to the irreducible water saturation. The BVI (Bulk Volume Irreducible) water saturation was estimated as 0.04 using NMR (Nuclear Magnetic Resonance) log. The permeability, $k$ in mD is estimated using the relation: $$k = 10^4 \phi^4 \left(\frac{FFI}{\phi - FFI}\right)^2$$ where FFI is the Free Fluid Index. Based on this information, the permeability (in mD) is

Explanation

GATE→2025→Core→Petroleum Formation Evaluation

Q153

MCQ[1 Mark]

Which ONE of the following rocks shows the highest reading in the natural gamma ray log?

(A)

Dolomite

(B)

Anhydrite

(C)

Oil Shale

(D)

Limestone

Explanation

GATE→2025→Core→Petroleum Formation Evaluation

Q154

MCQ[2 Marks]

Match the well logging methods in GROUP I with their corresponding measured parameters in GROUP II. **GROUP I:** (P) Neutron log (Q) Density log (R) Microspherically Focused Log (MSFL) (S) Sonic log **GROUP II:** (I) Resistivity in the flushed/invaded zone (II) Hydrogen ion concentration in the formation (III) Interval transit time of a compressional wave (IV) Electron density of the formation

(A)

P-IV; Q-I; R-II; S-III

(B)

P-II; Q-IV; R-I; S-III

(C)

P-II; Q-III; R-IV; S-I

(D)

P-III; Q-IV; R-I; S-II

Explanation

GATE→2025→Core→Petroleum Formation Evaluation

Q155

MSQ[2 Marks]

Which of the following logging tool(s) underestimate(s) porosity in a gas-bearing formation?

(A)

Neutron log

(B)

Nuclear Magnetic Resonance (NMR) log

(C)

Sonic log

(D)

Density log

Explanation

GATE→2025→Core→Petroleum Formation Evaluation

Q156

NAT[2 Marks]

The formation resistivity factor ($F$) is related to the formation porosity ($\phi$) in a water-bearing carbonate formation by the following correlation: $$F = 0.9 \phi^{-2}$$ where $\phi$ is in fraction. The resistivity of the invaded zone of the formation obtained by the Microspherically Focused Log (MSFL) is $4.5\text{ }\Omega\text{m}$, and the resistivity of the mud-filtrate is $0.05\text{ }\Omega\text{m}$. The formation porosity is ______ % (rounded off to one decimal place).

Explanation

GATE→2025→Core→Petroleum Formation Evaluation

Q157

NAT[2 Marks]

The porosity of a formation with matrix density of $2.65\text{ g/cc}$ and fluid density of $1.0\text{ g/cc}$ is 0.15. The formation has shear modulus of 30 GPa and bulk modulus of 36 GPa. The compressional wave velocity in the formation is ______ $\times 10^3\text{ m/s}$ (rounded off to two decimal places).

Explanation

GATE→2024→Core→Petroleum Formation Evaluation

Q158

NAT[1 Mark]

Shear wave velocity ($V_s$) in a limestone formation is $3600\text{ m/s}$. Assume that the modulus of incompressibility ($K$) is twice that of the modulus of rigidity ($G$), and the bulk density ($\rho_b$) of the formation is $2700\text{ kg/m}^3$. For this limestone formation, the compressional wave velocity ($V_p$) is ______ m/s.

Explanation

GATE→2024→Core→Petroleum Formation Evaluation

Q159

MCQ[2 Marks]

The decay of Gamma ray energy in the Earth formation goes through three dominant processes represented by regions I, II, and III in the figure below. Which ONE of the following options is CORRECT?

(A)

I-Photoelectric effect; II-Pair production effect; III-Compton effect

(B)

I-Epithermal effect; II-Pair production effect; III-Photoelectric effect

(C)

I-Photoelectric effect; II-Compton effect; III-Pair production effect

(D)

I-Epithermal effect; II-Photoelectric effect; III-Compton effect

Explanation

GATE→2024→Core→Petroleum Formation Evaluation

Q160

NAT[2 Marks]

A core sample from a well-consolidated sand has a length of $10\text{ cm}$, diameter of $4\text{ cm}$, and a resistance ($r$) of $100\text{ }\Omega$ at $T_2 = 200^\circ\text{F}$ when completely saturated with brine. The resistivity $R_w(T_1)$ of brine is $0.5\text{ }\Omega\cdot\text{m}$ at $T_1 = 75^\circ\text{F}$. The cementation factor $m=2$ and tortuosity $a=1$. The porosity (in fraction) of the core sample using Archie's/Humble's formula at $200^\circ\text{F}$ is (round off to two decimal places).

Explanation

GATE→2024→Core→Petroleum Formation Evaluation

Q161

NAT[2 Marks]

In an exploratory well, both clean and dirty reservoir sand with quartz as major mineralogy is encountered. The fraction of shale volume ($V_{sh}$) in the dirty reservoir sand is 25% with grain density ($\rho_{sh}$) of $2.7\text{ g/cc}$, quartz grain density ($\rho_q$) of $2.65\text{ g/cc}$. Bulk density of clean sand is $2\text{ g/cc}$ and dirty sand is $2.25\text{ g/cc}$, fluid density $\rho_f = 1\text{ g/cc}$. The difference of porosity $(\phi_{Clean} - \phi_{Dirty})$ in fraction is (round off to three decimal places).

Explanation

GATE→2023→Core→Petroleum Formation Evaluation

Q162

MCQ[1 Mark]

Which of the following instruments can measure contact angle of a liquid drop placed on a surface?

(A)

Goniometer

(B)

Pycnometer

(C)

Soxhlet apparatus

(D)

Rheometer

Explanation

GATE→2023→Core→Petroleum Formation Evaluation

Q163

MCQ[1 Mark]

The response of a four-arm caliper log in a drilled section is shown. The borehole features associated with the three identified sections P, Q, and R are

(A)

P: washout; Q: in-gauge hole; R: key-seat

(B)

P: key-seat; Q: in-gauge hole; R: washout

(C)

P: under-gauge hole; Q: in-gauge hole; R: washout

(D)

P: dog-leg; Q: in-gauge hole; R: key-seat

Explanation

GATE→2023→Core→Petroleum Formation Evaluation

Q164

MCQ[1 Mark]

Which of the following is necessary for the generation of electrokinetic (streaming potential) across well-bore and permeable rock formation?

(A)

Salinity gradient

(B)

Pressure gradient

(C)

Shale membrane

(D)

Mud cake

Explanation

GATE→2023→Core→Petroleum Formation Evaluation

Q165

MCQ[1 Mark]

A first arrival amplitude of the Cement Bond Log (CBL) of a cased hole section is given. The identified depth intervals P, Q, and R represent

(A)

P: not cemented; Q: partially cemented; R: well-cemented

(B)

P: not cemented; Q: well-cemented; R: partially cemented

(C)

P: partially cemented; Q: not cemented; R: well-cemented

(D)

P: well-cemented; Q: not cemented; R: partially cemented

Explanation

GATE→2023→Core→Petroleum Formation Evaluation

Q166

NAT[2 Marks]

A compressional acoustic wave takes $55 \text{ }\mu\text{s}$ to travel $0.3048 \text{ m}$ through a rock formation having bulk modulus $K = 37.5 \text{ GPa}$ and shear modulus $G = 31 \text{ GPa}$. The bulk density of the rock is $\text{kg/m}^3$ (rounded to two decimal places).

Explanation

GATE→2023→Core→Petroleum Formation Evaluation

Q167

NAT[2 Marks]

A gamma ray log run across a sand-shale sequence recorded maximum (shale) and minimum (clean sand) values of $70 \text{ API}$ and $30 \text{ API}$, respectively. A bed has a gamma log value of $50 \text{ API}$. Assuming a linear relationship, the volume fraction of shale ($V_{sh}$) in the bed is (rounded to one decimal place).

Explanation

GATE→2023→Core→Petroleum Formation Evaluation

Q168

NAT[2 Marks]

Flushed zone resistivity $R_{xo} = 20 \text{ }\Omega\cdot\text{m}$, 100% brine saturated core resistivity $R_0 = 6 \text{ }\Omega\cdot\text{m}$, brine resistivity $R_w = 0.6 \text{ }\Omega\cdot\text{m}$, mud filtrate resistivity $R_{mf} = 0.9 \text{ }\Omega\cdot\text{m}$, saturation exponent $n = 2$. The estimated residual hydrocarbon saturation ($S_{hr} = 1 - S_{xo}$) in percentage is (rounded to two decimal places).

Explanation

GATE→2022→Core→Petroleum Formation Evaluation

Q169

MCQ[1 Mark]

The Timur chart for estimating permeability is a log-log plot between

(A)

Porosity and Water Saturation

(B)

True Resistivity and Water Saturation

(C)

Porosity and Irreducible Water Saturation

(D)

Porosity and True Resistivity

Explanation

GATE→2022→Core→Petroleum Formation Evaluation

Q170

MSQ[1 Mark]

The logging tool(s) preferred for measuring formation resistivity in a well drilled with oil-based mud (non-conductive mud) is/are

(A)

Dual Laterolog

(B)

Compensated Neutron Log

(C)

Compensated Density Log

(D)

Induction Log

Explanation

GATE→2022→Core→Petroleum Formation Evaluation

Q171

MSQ[1 Mark]

Which of the following Logging tool combinations are required to estimate Hydrocarbon Initial in Place (HCIP) requiring porosity and water saturation ($S_w$)?

(A)

Resistivity Log, Neutron Log and Gamma Ray Log

(B)

Sonic Log, Neutron Log and Gamma Ray Log

(C)

Resistivity Log, Density Log and Gamma Ray Log

(D)

Neutron Log, Density Log and Sonic Log

Explanation

GATE→2022→Core→Petroleum Formation Evaluation

Q172

MCQ[2 Marks]

The log data obtained for a well section (Gamma Ray, Density, Neutron logs) are shown. Identify the CORRECT interpretations for Zones 1, 2, 3, and 4.

(A)

Zone 1 - shale, Zone 2 - clean sand with oil, Zone 3 - clean sand with gas, Zone 4 - clean sand with water

(B)

Zone 1 - clean sand with gas, Zone 2 - clean sand with oil, Zone 3 - clean sand with water, Zone 4 - shale

(C)

Zone 1 - shale, Zone 2 - clean sand with gas, Zone 3 - clean sand with oil, Zone 4 - clean sand with water

(D)

Zone 1 - clean sand with water, Zone 2 - clean sand with oil, Zone 3 - clean sand with gas, Zone 4 - shale

Explanation

GATE→2022→Core→Petroleum Formation Evaluation

Q173

NAT[2 Marks]

Sandstone reservoir top at $3421 \text{ ft}$. At $3425 \text{ ft}$, pressure is $1560 \text{ psi}$, oil API = $35^\circ$. Brine density = $1.04 \text{ g/cc}$ ($0.451 \text{ psi/ft}$), displacement pressure = $1.2 \text{ psi}$. The Oil-Water Contact (OWC) depth is ft from surface (rounded off to two decimal places).

Explanation

GATE→2022→Core→Petroleum Formation Evaluation

Q174

NAT[2 Marks]

Sandstone reservoir with density log reading $\rho_b = 2.11 \text{ g/cc}$ and sonic log reading $\Delta t = 90 \text{ }\mu\text{s/ft}$. Given $\rho_{ma} = 2.68$, $\rho_{fl} = 1.0$, $\Delta t_{ma} = 54$, $\Delta t_{fl} = 189$. The calculated secondary (vuggy/fracture) porosity $\phi_2 = \phi_{sonic} - \phi_{density}$ in % is (rounded to nearest integer).

Explanation

GATE→2022→Core→Petroleum Formation Evaluation

Q175

NAT[2 Marks]

Waxman-Smits shaly sand equation with $\phi = 0.25$, $BQ_v = 17.0$, $m^* = n^* = 2.0$, $R_w = 0.05 \text{ }\Omega\cdot\text{m}$ ($C_w = 20 \text{ }\Omega^{-1}\text{m}^{-1}$), $R_t = 12 \text{ }\Omega\cdot\text{m}$ ($C_t = 1/12$). Calculated water saturation $S_w$ in % is (marked MTA).

Explanation

Oil and Gas Well Testing

29 Questions

GATE→2026→Core→Oil and Gas Well Testing

Q176

MCQ[1 Mark]

A circular shaped reservoir has external radius of $r_e$. A well of radius $r_w$ lies in the centre of the reservoir. The part of the reservoir around the wellbore up to a radius of $r_s$ is damaged, where $r_w < r_s < r_e$. Formation damage causes additional pressure drop $\Delta P(r)$ that varies with radial distance $r$. Which of the following is TRUE about the additional pressure drop at the radial location, $r_s$ due to formation damage?

(A)

$\Delta P(r_s) = \Delta P(r_w)$

(B)

$\Delta P(r_s) = 0$

(C)

$\Delta P(r_s) = 2 \times \Delta P(r_w)$

(D)

$\Delta P(r_s) = 4 \times \Delta P(r_w)$

Explanation

GATE→2026→Core→Oil and Gas Well Testing

Q177

MCQ[1 Mark]

In a drawdown test, $P_D$, $t_D$, and $C_D$ are dimensionless pressure, dimensionless time, and dimensionless wellbore storage coefficient, respectively. In the early time of a drawdown test, fluid flow results from wellbore unloading. For this period, which of the following is the CORRECT representation of the relationship among these parameters?

(A)

$t_D = P_D C_D$

(B)

$C_D = P_D t_D$

(C)

$P_D = t_D C_D$

(D)

$t_D = P_D + C_D$

Explanation

GATE→2026→Core→Oil and Gas Well Testing

Q178

MSQ[1 Mark]

Pressure ($p$) as function of radius ($r$) and time ($t$) can be found from the analytical solution of radial diffusivity equation for homogenous and isotropic reservoir following Darcy law. For this solution, if $\frac{\partial p}{\partial t}$ is treated as constant, which of the following correctly describe(s) the state(s) of pressure change?

(A)

Transient

(B)

Pseudo-steady

(C)

Steady

(D)

Unsteady

Explanation

GATE→2026→Core→Oil and Gas Well Testing

Q179

NAT[1 Mark]

A circular reservoir with a well in the centre is producing oil at constant rate under pseudo steady state. The rate of pressure change measured at the wellbore is $1.0 \text{ psi/day}$. Pressure at the external radius of the reservoir at a certain time was 3500 psi. After 500 days, the pressure (in psi) at the external radius will be

Explanation

GATE→2026→Core→Oil and Gas Well Testing

Q180

MCQ[2 Marks]

Real gas pseudo pressure is used to derive diffusivity equation for highly compressible fluid for which viscosity ($\mu$) and gas compressibility factor ($Z$) are functions of pressure ($p$). Which of the following represents the partial derivative of the real gas pseudo pressure with respect to time ($t$)?

(A)

$\frac{2p}{\mu Z} \frac{\partial p}{\partial t}$

(B)

$\frac{p^2}{2\mu Z} \frac{\partial p}{\partial t}$

(C)

$\frac{\mu Z}{2p} \frac{\partial p}{\partial t}$

(D)

$\frac{2\mu Z}{p^2} \frac{\partial p}{\partial t}$

Explanation

GATE→2026→Core→Oil and Gas Well Testing

Q181

MSQ[2 Marks]

Pressure change and derivative type curves (Bourdet type curves) are used in the well test analysis. Which of the following statements is/are CORRECT about these type curves?

(A)

These curves are on Log-Log plot.

(B)

Horizontal axis is for dimensionless time $t_p$.

(C)

All derivative type curves merge in the middle time region.

(D)

Vertical axis is for dimensionless pressure $P_D$ only.

Explanation

GATE→2026→Core→Oil and Gas Well Testing

Q182

NAT[2 Marks]

A drawdown test data is analyzed to find out the permeability and skin factor of the reservoir using a semi-log plot. Flowing bottomhole pressure (in psi) is plotted on the linear scale against time (in hours). Flow rate is 1500 STB/day, oil formation volume factor is 1.2 RB/STB, oil viscosity is 1 cP, and thickness of the bed is 10 ft. After plotting, it is found that the slope of the straight line fitting the data in the middle time region is $-60 \text{ psi/log cycle}$. The permeability of the reservoir (in mD) is [RB: Reservoir Barrel; STB: Stock Tank Barrel]

Explanation

GATE→2026→Core→Oil and Gas Well Testing

Q183

NAT[2 Marks]

Matthews-Brons-Hazebroek (MBH) plots are used to calculate the Dietz shape factor ($C_A$) for reservoirs of various shapes. The MBH plot for a right-angled triangle reservoir with a well in the centre shows a reading of dimensionless pressure $P_{D(MBH)} = 3.0$ at the modified dimensionless time $t_{DA} = 1.0$. The Dietz shape factor of this right-angled triangle reservoir is

Explanation

GATE→2026→Core→Oil and Gas Well Testing

Q184

NAT[2 Marks]

Three wells are at the corners of an equilateral triangle inside an infinite acting reservoir. The reservoir is horizontal, homogenous and isotropic and has uniform thickness. Initial reservoir pressure is 3000 psi. If only one of the wells had been producing in the transient state, the pressure at the centre of equilateral triangle would have dropped by 100 psi after 60 days. If all the three wells started producing simultaneously in transient state at the same rate, then after 60 days since the start of production, the pressure at the centre of the equilateral triangle (in psi) is

Explanation

GATE→2025→Core→Oil and Gas Well Testing

Q185

MCQ[1 Mark]

Which ONE of the following CANNOT be obtained from pressure transient analysis in well testing?

(A)

Formation damage

(B)

Average reservoir pressure

(C)

Solution gas-oil ratio

(D)

Drainage pore volume

Explanation

GATE→2025→Core→Oil and Gas Well Testing

Q186

MCQ[1 Mark]

$C_1$, $C_2$, and $C_3$ are the Dietz shape factors of three reservoirs with circular ($C_1$), square ($C_2$), and rectangular ($C_3$) shape of drainage area, respectively. The well is located at the geometric center of the reservoir. Which ONE of the following options is CORRECT about the shape factors?

(A)

$C_3 < C_2 < C_1$

(B)

$C_2 < C_1 < C_3$

(C)

$C_1 < C_2 = C_3$

(D)

$C_1 = C_2 < C_3$

Explanation

GATE→2025→Core→Oil and Gas Well Testing

Q187

MCQ[1 Mark]

Four curves designated as I, II, III, and IV are shown in the figure. $q_f$ is the bottomhole oil flow rate, $q_s$ is the surface oil flow rate, and $B_o$ is the oil formation volume factor. Which ONE of the following curves depicts the minimum wellbore storage effect?

(A)

I

(B)

II

(C)

III

(D)

IV

Explanation

GATE→2025→Core→Oil and Gas Well Testing

Q188

MSQ[1 Mark]

Consider the following diffusivity equation for the radial flow of a fluid in an infinite and homogeneous reservoir: $$\frac{1}{r} \frac{\partial}{\partial r} \left( r \frac{\partial P}{\partial r} \right) = \frac{1}{\eta} \frac{\partial P}{\partial t}$$ where $P$ denotes pressure, $r$ is radial distance, $t$ is time, and $\eta$ is diffusivity constant. Initial reservoir pressure is $P_i$. The condition(s) used in the derivation of analytical solution of the above equation for pressure transient analysis in an infinite acting reservoir is/are:

(A)

At time $t=0$, $P=P_i$ for all r.

(B)

Wellbore is treated as a line source.

(C)

As $r \to \infty$, $P \to P_i$ for all t.

(D)

At any radius r and time t, the pressure gradient $\frac{\partial P}{\partial r}$ is constant.

Explanation

GATE→2025→Core→Oil and Gas Well Testing

Q189

MSQ[2 Marks]

Which of the following option(s) is/are CORRECT for well testing analysis of a reservoir?

(A)

Permeability, skin and reservoir geometry are calculated using data from pseudo steady state.

(B)

Permeability, skin and reservoir geometry are calculated using data from transient state.

(C)

Reservoir geometry is calculated using data from pseudo steady state.

(D)

Absolute open flow potential is calculated from back pressure test for a gas well.

Explanation

GATE→2025→Core→Oil and Gas Well Testing

Q190

NAT[2 Marks]

Log-log plot of pressure drop ($\Delta p$) versus time ($t$) obtained using well test data is matched with one of the Grigarten type curves. Thereafter, a point on the type curve is chosen with $P_D = 10$ and $t_D/C_D = 100$, where $P_D$, $t_D$, and $C_D$ are dimensionless pressure, dimensionless time, and dimensionless wellbore storage, respectively. The corresponding match point on the log-log plot is $\Delta p = 250\text{ psi}$ and $t = 10\text{ hrs}$. Oil flow rate is $500\text{ rb/day}$. Viscosity of oil is $1.5\text{ cP}$. Thickness of the reservoir is $10\text{ ft}$ and formation volume factor of oil is $1.2\text{ rb/stb}$. The permeability of the reservoir is ______ mD (rounded off to one decimal place).

Explanation

GATE→2025→Core→Oil and Gas Well Testing

Q191

NAT[2 Marks]

Correlation equations for gas compressibility factor ($z$) and viscosity ($\mu$) as functions of pressure ($p$) are given as below: $$z = C_1 p^{-0.25} ; \quad \mu = C_2 p^{1.25}$$ where $C_1$ and $C_2$ are constants, consistent with field units ($p$ in psi, $\mu$ in cP), with values 1.96 and $7 \times 10^{-4}$, respectively. Real gas pseudo pressure corresponding to a pressure of 2500 psi is ______ $\times 10^6\text{ psi}^2/\text{cP}$ (rounded off to two decimal places).

Explanation

GATE→2024→Core→Oil and Gas Well Testing

Q192

MCQ[1 Mark]

Well tests can be classified as either 'single well productivity test' or 'descriptive reservoir test'. Which ONE of the following CANNOT be determined from a 'single well productivity test'?

(A)

Characteristics of the formation damage and other source of skin

(B)

Well deliverability

(C)

Characteristics of both vertical and horizontal reservoir heterogeneity

(D)

Identification of produced fluids and their respective volume ratios

Explanation

GATE→2024→Core→Oil and Gas Well Testing

Q193

MCQ[2 Marks]

Which of the following tests is/are used to obtain reservoir deliverability ($kh/\mu$) information? 1. Exploration or appraisal well openhole wireline 2. Exploration or appraisal well Drill Stem Test (DST) 3. Development well openhole wireline 4. Development well Drill Stem Test (DST)

(A)

1 only

(B)

3 only

(C)

1 and 3

(D)

2 and 4

Explanation

GATE→2024→Core→Oil and Gas Well Testing

Q194

MCQ[2 Marks]

Consider single-phase radial flow of a fluid with constant viscosity and low compressibility... Match the flow regime with the CORRECT mathematical relation given in the table. **Flow Regime:** (P) Steady-state flow (Q) Transient flow (R) Pseudosteady-state flow **Mathematical Relation:** (I) $(\partial P / \partial t)_r = 0$ (II) $(\partial P / \partial t)_r = \text{constant}$ (III) $(\partial P / \partial t)_r = f(r,t)$

(A)

P-I; Q-II; R-III

(B)

P-I; Q-III; R-II

(C)

P-II; Q-II; R-I

(D)

P-II; Q-I; R-III

Explanation

GATE→2023→Core→Oil and Gas Well Testing

Q195

MCQ[1 Mark]

Consider an immiscible liquid mixture of n-decane and water containing fully dissociated NaCl. Using Gibbs Phase Rule ($F = C - P + 2$), the number of degrees of freedom for this system is

(A)

3

(B)

4

(C)

5

(D)

2

Explanation

GATE→2023→Core→Oil and Gas Well Testing

Q196

MCQ[2 Marks]

Match the flow regimes associated with a vertically fractured well in a reservoir: (P) Formation Linear Flow (Q) Fracture Linear Flow (R) Bilinear Flow (S) Pseudo-Radial Flow\nwith their corresponding schematic flow descriptions.

(A)

P-I; Q-III; R-II; S-IV

(B)

P-III; Q-I; R-II; S-IV

(C)

P-III; Q-I; R-IV; S-II

(D)

P-I; Q-II; R-III; S-IV

Explanation

GATE→2023→Core→Oil and Gas Well Testing

Q197

MSQ[2 Marks]

Which of the following statement(s) is/are TRUE regarding Horner plot regions (ETR, MTR, LTR) in a pressure build-up test?

(A)

Early Time Region (ETR): Pressure build-up data is affected by reservoir boundaries and other reservoir heterogeneities such as sealing faults

(B)

Middle Time Region (MTR): Pressure build-up data is reached after end of the wellbore storage and the pressure transient has entered the virgin reservoir

(C)

Late Time Region (LTR): Pressure build-up data is affected by reservoir boundaries and other reservoir heterogeneities such as sealing faults

(D)

Middle Time Region (MTR): Pressure build-up data is affected by reservoir boundaries and other reservoir heterogeneities such as sealing faults

Explanation

GATE→2023→Core→Oil and Gas Well Testing

Q198

NAT[2 Marks]

After well completion, a discovery well in an oil reservoir is produced and then closed for a pressure build-up test. Production history: $500 \text{ STB/day}$ for $5 \text{ days}$, $550 \text{ STB/day}$ for $7 \text{ days}$, $400 \text{ STB/day}$ for $8 \text{ days}$. Horner's pseudo-producing time $t_{pH}$ is hr (rounded to nearest integer).

Explanation

GATE→2022→Core→Oil and Gas Well Testing

Q199

NAT[1 Mark]

A homogeneous sandstone reservoir is under radial steady state flow. Wellbore radius $r_w = 0.1 \text{ m}$. Formation damage radius $r_s = 1.0 \text{ m}$. Permeability ratio $k/k_s = 5$. The value of skin factor is (rounded off to two decimal places).

Explanation

GATE→2022→Core→Oil and Gas Well Testing

Q200

MCQ[2 Marks]

Flow tests are conducted for oil wells in reservoirs P, Q, R, and S with given parameters. Identify the reservoir in which the pressure transient reaches earliest at a point $2000 \text{ ft}$ away from the wellbore (highest hydraulic diffusivity $\eta = \frac{k}{\phi \mu c_t}$).

(A)

P

(B)

Q

(C)

R

(D)

S

Explanation

GATE→2022→Core→Oil and Gas Well Testing

Q201

MCQ[2 Marks]

Identify the CORRECT match for flow regimes (Group 1) with pressure derivative log-log slopes (Group 2): I. Spherical flow II. Linear flow III. Bilinear flow IV. Boundary dominated flow Slopes: (P) 1, (Q) 1/4, (R) -1/2, (S) 1/2

(A)

I-P; II-Q; III-R; IV-S

(B)

I-Q; II-S; III-R; IV-P

(C)

I-R; II-S; III-Q; IV-P

(D)

I-S; II-P; III-Q; IV-R

(E)

I-R; II-S; III-Q; IV-P (Option C check)

Explanation

GATE→2022→Core→Oil and Gas Well Testing

Q202

MSQ[2 Marks]

Well testing is to be conducted on bounded sandstone reservoirs with different well locations (Reservoirs 1, 2, 3). Which of the following statements are CORRECT?

(A)

Pseudo steady flow regime will develop first in Reservoir 1.

(B)

Infinite acting behavior will stop first in Reservoir 2.

(C)

Infinite acting behavior will sustain the longest in Reservoir 1.

(D)

Pressure depletion will be the fastest in Reservoir 3.

Explanation

GATE→2022→Core→Oil and Gas Well Testing

Q203

NAT[2 Marks]

For an oil well drawdown test with total compressibility $c_t = 20 \times 10^{-6} \text{ psi}^{-1}$, porosity $\phi = 15\%$, wellbore radius $r_w = 0.25 \text{ ft}$, wellbore fluid volume $V_w = 180 \text{ rb}$, oil viscosity $\mu = 2 \text{ cP}$, thickness $h = 50 \text{ ft}$, permeability $k = 30 \text{ mD}$, skin $S = 0$, the duration of the wellbore storage effect ($t_{wbs}$) in hours is

Explanation

GATE→2022→Core→Oil and Gas Well Testing

Q204

NAT[2 Marks]

Total oil production rate from a volumetric reservoir is $q = 200 \text{ bbl/day}$ at initial FBHP = $3000 \text{ psi}$. Reservoir properties: $h = 10 \text{ ft}$, $\phi = 18\%$, $c_t = 50 \times 10^{-6} \text{ psi}^{-1}$, $k = 35 \text{ mD}$, $r_w = 0.25 \text{ ft}$, $S = 0$, $r_e = 1000 \text{ ft}$, $\mu = \dots$ (or derived). Considering pseudo steady state, the bottomhole pressure after $180 \text{ days}$ is psi (rounded off to two decimal places).

Explanation

Health Safety and Environment in Petroleum Industry

12 Questions

GATE→2026→Core→Health Safety and Environment in Petroleum Industry

Q205

MCQ[2 Marks]

Choose the CORRECT match of the fire detection systems in GROUP X with their corresponding working mechanisms in GROUP Y. **GROUP X:** (P) Fusible plug loops (Q) Thermal and smoke detection system (R) Gas detection system **GROUP Y:** (I) Detects rise in temperature caused by fire and visible/invisible particles of combustion. (II) Functions based on drop in pressure that activates fire shutdown. (III) Detects flammables.

(A)

P-I; Q-II; R-III

(B)

P-II; Q-I; R-III

(C)

P-III; Q-I; R-II

(D)

P-II; Q-III; R-I

Explanation

GATE→2026→Core→Health Safety and Environment in Petroleum Industry

Q206

MSQ[2 Marks]

Which of the following is/are objective(s) of a safety system in offshore production platforms?

(A)

To prevent leak or overflow of hydrocarbons.

(B)

To prevent ignition of hydrocarbons released on the platform.

(C)

To prevent water coning in the reservoir.

(D)

To prevent gas coning in the reservoir.

Explanation

GATE→2025→Core→Health Safety and Environment in Petroleum Industry

Q207

MSQ[2 Marks]

Which of the following definition(s) related to fire and explosion is/are CORRECT?

(A)

Fire point is the lowest temperature at which the vapour above a liquid will continue to burn once ignited.

(B)

Deflagration is the explosion in which the reaction front moves at a speed greater than the speed of sound in the unreacted medium.

(C)

Detonation is the explosion in which the reaction front moves at a speed less than the speed of sound in the unreacted medium.

(D)

Flash point of a liquid is the lowest temperature at which it gives enough vapour to form an ignitable mixture with air.

Explanation

GATE→2024→Core→Health Safety and Environment in Petroleum Industry

Q208

MSQ[1 Mark]

Dilute sodium hydroxide is used in oilfield operations for enhanced oil recovery. For economic reasons, sodium hydroxide is delivered on site as anhydrous solid beads/cakes. This compound must be diluted on site by mixing water. Which of the following precautions must be followed during handling and preparation of dilute sodium hydroxide?

(A)

Use of Personal Protective Equipment (PPE) while handling and processing sodium hydroxide

(B)

Adequate ventilation to avoid exposure of sodium hydroxide aerosols

(C)

Stable supply of hot utility line as sodium hydroxide dilution is an endothermic reaction

(D)

Stable supply of cold utility line as sodium hydroxide dilution is an exothermic reaction

Explanation

GATE→2023→Core→Health Safety and Environment in Petroleum Industry

Q209

MCQ[1 Mark]

A mixture of a flammable gas and air can ignite ONLY if

(A)

the gas concentration is below the limiting oxygen concentration

(B)

the gas concentration is above the upper flammable limit

(C)

the gas concentration is between the lower and upper flammable limits

(D)

the gas concentration is below the lower flammable limit

Explanation

GATE→2023→Core→Health Safety and Environment in Petroleum Industry

Q210

MSQ[1 Mark]

Which of the following is/are the route(s) by which a toxic substance may enter a human body?

(A)

Ingestion

(B)

Inhalation

(C)

Perspiration

(D)

Asphyxiation

Explanation

GATE→2023→Core→Health Safety and Environment in Petroleum Industry

Q211

MSQ[1 Mark]

Select ALL the safety system(s) that is/are required in an offshore platform.

(A)

Permit to work system

(B)

Fire and gas alarms

(C)

Lock out-tag out

(D)

Financial monitoring system

Explanation

GATE→2023→Core→Health Safety and Environment in Petroleum Industry

Q212

MCQ[2 Marks]

Consider an industrial accident scenario involving a drain connection failure, vapor cloud formation, ignition, and eventual burnout. Match the three steps of the accident (P: Initiation, Q: Propagation, R: Termination) to the events: (I) Formation of vapor cloud (II) Failure of drain connection (III) Consumption of all combustibles

(A)

P-I; Q-III; R-II

(B)

P-II; Q-I; R-III

(C)

P-II; Q-III; R-I

(D)

P-I; Q-II; R-III

Explanation

GATE→2023→Core→Health Safety and Environment in Petroleum Industry

Q213

MSQ[2 Marks]

Select the statement(s) that is/are TRUE regarding combustion, fire, and explosion fundamentals.

(A)

Combustion always occurs in the vapor phase

(B)

Combustion cannot occur if air/oxidizer is absent

(C)

Flash point is the lowest temperature at which a vapor above a liquid will continue to burn once ignited

(D)

The distinction between a fire and explosion is in their rate of energy release

Explanation

GATE→2022→Core→Health Safety and Environment in Petroleum Industry

Q214

MCQ[1 Mark]

What is the maximum permissible limit of 'oil and grease' in discharged wastewater from a petroleum industry as per CPCB India guidelines?

(A)

5 ppm

(B)

10 ppm

(C)

30 ppm

(D)

50 ppm

Explanation

GATE→2022→Core→Health Safety and Environment in Petroleum Industry

Q215

MSQ[1 Mark]

The flammable gas detector works on which of the following phenomena/sensor technologies?

(A)

Catalytic

(B)

Paramagnetic

(C)

Electrochemical

(D)

Photoionisation

Explanation

GATE→2022→Core→Health Safety and Environment in Petroleum Industry

Q216

MCQ[2 Marks]

Match the contaminants (Group I) with their effluent wastewater treatment techniques (Group II): I. Suspended solids II. Biodegradable organics III. Heavy metals IV. Suspended oil and grease Techniques: (P) Ion exchange, (Q) Filtration, (R) Trickling filters, (S) Flocculation

(A)

I-P; II-Q; III-R; IV-S

(B)

II-R; III-P; I-Q; IV-S

(C)

II-S; I-Q; III-P; IV-R

(D)

II-S; I-R; III-Q; IV-P

Explanation

Enhanced Oil Recovery Techniques

14 Questions

GATE→2026→Core→Enhanced Oil Recovery Techniques

Q217

MSQ[1 Mark]

Which of the following is/are conventional Enhanced Oil Recovery method(s)?

(A)

Water flooding

(B)

In-Situ combustion

(C)

Surfactant flooding

(D)

Steam flooding

Explanation

GATE→2025→Core→Enhanced Oil Recovery Techniques

Q218

MSQ[1 Mark]

Which of the following statement(s) is/are CORRECT about polymer flooding?

(A)

Viscous fingering in the reservoir decreases.

(B)

Viscosity of the displaced fluid increases.

(C)

Mobility of the displacing fluid increases.

(D)

Mobility ratio decreases.

Explanation

GATE→2025→Core→Enhanced Oil Recovery Techniques

Q219

NAT[1 Mark]

The ratio of number of production to injection wells for a regular Seven-Spot pattern is ______ (rounded off to one decimal place).

Explanation

GATE→2024→Core→Enhanced Oil Recovery Techniques

Q220

MCQ[1 Mark]

For a schematically shown five-spot pattern, what is the ratio of number of production wells to the number of injection wells per pattern unit?

(A)

2

(B)

1

(C)

1/4

(D)

1/2

Explanation

GATE→2024→Core→Enhanced Oil Recovery Techniques

Q221

MSQ[1 Mark]

Which of the following is/are thermal enhanced oil recovery method(s)?

(A)

Alkali-surfactant-polymer flooding

(B)

In situ combustion

(C)

Steam assisted gravity drainage

(D)

Low salinity water flooding

Explanation

GATE→2024→Core→Enhanced Oil Recovery Techniques

Q222

MSQ[2 Marks]

The microbial enhanced oil recovery method helps to recover oil by which one or more of the following phenomena?

(A)

Reducing the interfacial tension due to production of biosurfactants.

(B)

Stimulating the well due to production of acids.

(C)

Increasing the mobility ratio due to production of biopolymers.

(D)

Reducing the viscosity due to production of gases in situ.

Explanation

GATE→2024→Core→Enhanced Oil Recovery Techniques

Q223

NAT[2 Marks]

A surfactant enhanced oil recovery process has been employed on a sandstone reservoir: $A = 20\text{ acres}$, $h = 25\text{ ft}$, $\phi = 0.20$, $S_{orw} = 0.30$, $S_{orc} = 0.10$, $B_o = 1.05$, $E_v = 1$, $S_{oi} = 0.75$. The ratio of oil displaced due to surfactant flood to the original oil in place at reservoir condition is (round off to two decimal places).

Explanation

GATE→2023→Core→Enhanced Oil Recovery Techniques

Q224

MCQ[1 Mark]

In-situ combustion method for enhanced oil recovery is commonly used for

(A)

gas condensate reservoirs

(B)

light oil reservoirs

(C)

brown oil reservoirs

(D)

heavy oil reservoirs

Explanation

GATE→2023→Core→Enhanced Oil Recovery Techniques

Q225

MSQ[1 Mark]

Polymer flooding enhances oil recovery from an oil reservoir by

(A)

increasing the mobility ratio

(B)

reducing the mobility ratio

(C)

reducing the viscous fingering

(D)

increasing the viscous fingering

Explanation

GATE→2023→Core→Enhanced Oil Recovery Techniques

Q226

NAT[2 Marks]

Consider a micellar displacement process in a reservoir with porosity $\phi = 0.30$. Microemulsion slug volume = 4% of pore volume, with 4 vol% surfactant. Rock density $\rho_{rock} = 2.7 \text{ g/cm}^3$, surfactant density $\rho_{surf} = 1.1 \text{ g/cm}^3$. Average surfactant adsorption = $0.25 \text{ mg/g}$ of rock. The fraction of injected surfactant adsorbed is (rounded to two decimal places).

Explanation

GATE→2022→Core→Enhanced Oil Recovery Techniques

Q227

MSQ[1 Mark]

Which of the following statements related to the 'enriched gas drive' are CORRECT?

(A)

The enriching components are transferred from the oil to the gas.

(B)

The enriched gas drive is an example of immiscible enhanced oil recovery.

(C)

A miscible zone is formed between the injected gas and the reservoir oil.

(D)

In enriched gas drive, the viscous fingering results in poor sweep efficiency.

Explanation

GATE→2022→Core→Enhanced Oil Recovery Techniques

Q228

MSQ[1 Mark]

Select the CORRECT statements for the injection-production well patterns.

(A)

Inverted 5-spot drive includes four injectors at the corners and the producer at the centre.

(B)

Regular 7-spot drive includes six injectors at the corners and the producer at the centre.

(C)

Staggered-line drive involves staggered injectors and producers.

(D)

Crestal injection involves positioning of the wells along the periphery of the reservoir.

Explanation

GATE→2022→Core→Enhanced Oil Recovery Techniques

Q229

NAT[2 Marks]

During waterflooding, areal sweep $E_a = 0.75$, vertical sweep $E_i = 0.85$. Average water saturation behind front $S_{wf} = 0.63$, initial water saturation $S_{wi} = 0.17$. Initial oil volume = $3200 \text{ rb}$. The amount of oil produced at breakthrough is rb (rounded off to two decimal places).

Explanation

GATE→2022→Core→Enhanced Oil Recovery Techniques

Q230

NAT[2 Marks]

Initial water saturation $S_{wi} = 30\%$, initial gas saturation $S_{gi} = 40\%$. At end of waterflooding, free gas dissolves, $B_o = 1.20 \text{ rb/stb}$, and final water saturation $S_{wf} = 50\%$. Two-phase FVF at initiation was $2.3 \text{ rb/stb}$. The pore-to-pore displacement efficiency is % (marked MTA / standard evaluation).

Explanation

Latest Trends in Petroleum Engineering

2 Questions

GATE→2026→Core→Latest Trends in Petroleum Engineering

Q231

MCQ[1 Mark]

Choose the correct option by matching the entries in Group X with their description in Group Y. **Group X:** (P) Gas hydrate (Q) Oil shale (R) Coal bed methane (S) Shale oil **Group Y:** (I) Gas is mostly present in adsorbed state (II) Sedimentary rock contains kerogen (III) Oil recovered from shale (IV) Gas is present inside the cages formed by water molecules

(A)

P-IV; Q-III; R-I; S-II

(B)

P-I; Q-II; R-IV; S-III

(C)

P-IV; Q-II; R-I; S-III

(D)

P-I; Q-III; R-IV; S-II

Explanation

GATE→2024→Core→Latest Trends in Petroleum Engineering

Q232

MCQ[1 Mark]

From the options given below, identify the process through which coal bed methane is produced.

(A)

Underground coal gasification

(B)

Open cast mining of coal

(C)

Depressurization, using vertical/horizontal wells

(D)

Underground coal combustion

Explanation