List of top Questions asked in GATE Petroleum Engineering

The drainage oil-water capillary pressure data for a core retrieved from a homogeneous isotropic reservoir is listed in the table. The reservoir top is at 4000 ft from the surface and the water-oil contact (WOC) depth is at 4100 ft. 
 


Assume the densities of water and oil at reservoir conditions are 1.04 g/cc and 0.84 g/cc, respectively. The acceleration due to gravity is 980 m/s². The interfacial tension between oil and water is 35 dynes/cm and the contact angle is 0°. 
The depth of free-water level (FWL) is .......... ft (rounded off to one decimal place). 
 

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 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: 

The eigenvalues of the matrix 

are \( \lambda_1, \lambda_2, \lambda_3 \). The value of \( \lambda_1 \lambda_2 \lambda_3 ( \lambda_1 + \lambda_2 + \lambda_3 ) \) is: 
 

Match the well logging methods in GROUP I with their corresponding measured parameters in GROUP II: 

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. 

 

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 the radial distance from the center of the wellbore, \( t \) denotes time, and \( \eta \) is the diffusivity constant. The initial pressure of the reservoir 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:

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

For a hydrocarbon reservoir, the following parameters are used in the general material balance equation (MBE). 

The total pore volume (in rb) of the reservoir is:

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?

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

Match the entries in GROUP I with the entries in GROUP II. 

Which ONE of the following options is CORRECT?

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? 

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? 

Four fair coins are tossed simultaneously. The probability that at least one tail turns up is:
An isotropic and homogeneous oil reservoir has a porosity of 20%, thickness of 20 ft, and total compressibility of \( 15 \times 10^{-6} \) 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
\[ p_{{wf}} = 2850 - 5t \] The pressure is in psi and time is in hours. During the well test, the oil flow rate is 1800 rb/day.
The drainage area of the reservoir is .......... acres (rounded off to two decimal places).
A production tubing string of length 1500 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°C. The Young’s modulus of elasticity of the tubing material is 3000 N/m², 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 .......... N/m² (rounded off to two decimal places).
A homogeneous rock layer \( Q \) of density 2600 kg/m³ is lying below homogeneous rock layer P of density 2400 kg/m³. 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 km/s in the rock layer P and 3.5 km/s in layer Q.
The ratio of reflection coefficient to the transmission coefficient at the interface is .......... (rounded off to two decimal places).
The hydrostatic pressure gradient in a vertical well drilled in a relaxed depositional basin is 0.452 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 × 10⁻² 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).
A vertical well is drilled up to a depth of 4000 ft. Further drilling starts with 10 ppg of fresh mud and 50000 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 still density is 65.5 ppg.
The decrease in hook load is .......... lbf (rounded off to one decimal place).
A horizontal well is planned with two radial sections to land the target at an angle of 90°. The total vertical depth (TVD) between the surface and the target is 8000 ft. The buildup rate is 6° per 100 ft in the first section and 9° per 100 ft in the second section. The total angle built by the second section is 30°.
The distance of the first kickoff point from the surface is .......... ft (rounded off to one decimal place).
The laboratory analysis data obtained from the core is as follows:
Weight of clean dry core in air = 30 g
Weight of core completely saturated with oil = 32 g
Weight of saturated core completely immersed in oil = 24 g
If the density of oil used for saturation of core during the experiment is 0.88 g/cc, then the effective porosity of the core is .......... % (rounded off to two decimal places).
The Buckley Leverett frontal advance theory is employed to evaluate the performance of the water flooding operation in a horizontal reservoir.
The following data are given:
- Cross-sectional flow area = 40000 ft²
- Payzone thickness = 20 ft
- Porosity = 20%
- Water injection rate = 1000 rb/day
- Distance between injection and production well = 1000 ft
- Cumulative pore volume of water injected (PVWI) at breakthrough = 0.5
The time of breakthrough is .......... days (rounded off to one decimal place).
A hydraulically fractured vertical well has fracture permeability of 4000 mD, fracture width of 0.12 in, and fracture half-length of 1000 ft.
Dimensionless fracture conductivity is .......... \( \times 10^{-4} \) (rounded off to two decimal places).
An electrical submersible pump is to be installed to lift oil of 30° API in a 10000 ft deep well. The oil formation volume factor (\( B_o \)) is 1.25 rb/stb. The desired flow rate is 8000 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).