List of top Reservoir Engineering Questions asked in GATE PE

A 1 kg-mol bottled gas consists of the following composition at 30\(^\circ\)C. The equilibrium vapour composition of n-Butane in mol % is ____________ (rounded off to two decimal places).
Well testing is to be conducted on the bounded sandstone reservoirs as shown in the figures. All the reservoirs have the same drainage area, rock and fluid properties, and well bore conditions. Which of the following statements are CORRECT for the given reservoirs?
An exploratory well is planned to be drilled in a basin that extends up to a depth of 5000 m. The surface temperature is 30°C. The geothermal gradient of the basin is 0.025°C/m. Select the possible range(s) of depth at which the potential oil-bearing zones can be encountered.
The following data are given for an oil well scheduled for a drawdown test.

Total compressibility = \( 20 \times 10^{-6} \, \text{psi}^{-1} \)
Oil compressibility = \( 100 \times 10^{-6} \, \text{psi}^{-1} \)
Volume of fluid in the wellbore = 180 rb
Average oil density in the wellbore = 45 lb/ft\(^3\)
Tubing outer diameter = 2 inch
Casing inner diameter = 7.675 inch
Porosity = 15%
Wellbore radius = 0.25 ft
Oil viscosity = 2 cP
Pay zone thickness = 50 ft
Skin factor = 0
Permeability = 30 mD
If the well is tested at a constant rate, the ‘Wellbore Storage Effect’ would sustain for ______________ hours (rounded off to two decimal places).
During the core analysis, the following data are measured at laboratory and reservoir conditions.
The capillary pressure at the laboratory condition is 50 psi. The calculated capillary pressure using the Leverett J-function at the reservoir condition is ________________ psi (rounded off to two decimal places).
The total oil production rate (measured at the bottom hole conditions) from a volumetric reservoir is 200 bbl/day (1 bbl = 5.615 ft\(^3\)) at the flowing bottom hole pressure (FBHP) of 3000 psi. The reservoir has the following properties:
Considering a radial flow under pseudo steady state, the bottom hole pressure after 180 days is ________________ psi (rounded off to two decimal places).
An incompressible fluid (density = 40 lb/ft\(^3\)) flows at a steady state through a linear porous media with the following properties:

Length (L) = 1500 ft
Height (H) = 15 ft
Width (W) = 30 ft
Permeability = 150 mD
Viscosity = 1.5 cP
Inlet pressure (P\(_1\)) = 1600 psi
Outlet pressure (P\(_2\)) = 1590 psi
Porosity = 18%
The absolute value of the difference between the actual fluid velocity (ft/day) at \( \theta = 0^\circ \) and \( \theta = 10^\circ \) is ______________ (rounded off to three decimal places).
A real gas is produced from a gas reservoir at a constant temperature of 30°C. The compressibility factor (\(Z\)) is observed to change with pressure (\(P\)) at a rate of \[ \left( \frac{\partial Z}{\partial P} \right)_T = Z^2 \] The difference in the compressibility of the real gas from the ideal gas at a given pressure (\(P\)) and temperature (\(T\)) is:
Capillary pressure (\(P_c\)) vs water saturation (\(S_w\)) curves for different sandstone reservoirs (I, II, III and IV) are given in the following figure.
Which reservoir has the most uniform pore size distribution?
Flow tests are conducted for oil well in reservoirs P, Q, R and S having different parameters as given in the following table. In all the four cases the wells are tested at 1200 stb/day.
Identify the reservoir in which the pressure transient reaches earliest at a point 2000 ft away from the wellbore.
Identify the CORRECT match for the flow regimes (Group 1) with the corresponding slopes of the pressure derivative (Group 2) used in the type curve analysis.
The log data obtained for a particular well section are shown in the following figures. Identify the CORRECT interpretations for different zones.
Which of the following Logging tool combinations are required to estimate the Hydrocarbon Initial in Place (HCIP)?
A homogeneous sandstone reservoir is under a radial steady state flow. The wellbore radius is 0.1 m. The formation near the wellbore is damaged up to 0.9 m from the sand face. The permeability impairment results in \( k/k_s = 5 \), where \( k \) is the permeability in the undamaged region and \( k_s \) is that of the damaged region. The value of skin factor is (rounded off to two decimal places) ______________.
A reservoir is producing oil at 7000 stb/day with a producing gas to oil ratio (GOR) of 2000 scf/stb. At a certain point of time, the reservoir pressure is monitored and decided to be maintained at a constant pressure of 2500 psi using water injection. The PVT properties estimated at 2500 psi are:

Bubble point pressure = 3000 psi
Oil formation volume factor = 1.2 rb/stb
Water formation volume factor = 1.0 rb/stb
Gas formation volume factor = 0.0012 rb/scf
Solution GOR = 300 scf/stb
The initial water injection rate (stb/day) required to maintain oil production at 7000 stb/day is ________________ (rounded off to the nearest integer).
The logging tool(s) preferred for the measurement of formation resistivity in a well drilled with oil-based mud is/are:
Which of the following statements related to the 'enriched gas drive' are CORRECT?
Select the CORRECT statements for the injection-production well pattern.
The liquid shrinkage curves for different types of crude oil are shown in the following figure.
Which curve represents the Black Oil?
The Timur chart for estimating the permeability is the plot between
The formation volume factors of oil and water are \(B_o\) and \(B_w\), respectively. The CORRECT relationship between the fractional water cut at the surface condition \(f_{ws}\) and the fractional water cut at the reservoir condition \(f_w\) is:
A depleted and shut-in oil reservoir originally contained \(25 \times 10^6\) STB of oil with a formation volume factor of 1.35 res bbl/STB and a connate water saturation of 0.25. Cumulative oil production to date has been \(2.5 \times 10^6\) STB of oil. The oil formation volume factor is now 1.25 res bbl/STB. Assuming no water influx, the gas saturation in the reservoir is \(\underline{\hspace{2cm}}\) % (round off to one decimal place).

The fluid flow through an under-saturated oil reservoir is driven by solution gas drive mechanism. The reservoir parameters are as given below. 
\(\text{Compressibility of water, } c_w = 1 \times 10^{-6} \, \text{psi}^{-1}, \\ \text{Compressibility of formation, } c_f = 1 \times 10^{-5} \, \text{psi}^{-1},\)
\( \text{Connate water saturation, } S_{wc} = 0.2, \\ \text{Initial reservoir pressure, } p_i = 4000 \, \text{psi}, \\ \text{Reservoir pressure at bubble-point, } p_b = 3000 \, \text{psi},\)
\( \text{Oil formation volume factor, } B_{oi} = 1.24 \, \text{rb/STB}, \\ \text{Formation volume factor at bubble point pressure, } B_{ob} = 1.26 \, \text{rb/STB.}\)
The percentage of oil recovered as a fraction of the Original Oil in Place (OOIP) is \(\underline{\hspace{2cm}}\)% (round off to one decimal place).

A heavy oil reservoir with an initial oil recovery of 10% has the following properties. 
\(\text{Confined area } A = 1.5 \, \text{acres}, \text{ thickness of the reservoir } h = 15 \, \text{ft}, \text{ effective porosity }\) 
\(\phi = 15\%, \text{ irreducible water saturation } S_{wr} = 25\%, \text{ oil formation volume factor } B_o = 1.10 \, \text{bbl/STB}.\) 
An in-situ combustion test was conducted in the above reservoir. Oil recovery due to the combustion process at the well is observed to be 12000 bbl. 
The total (overall) oil recovery at the end of the in-situ combustion process is \(\underline{\hspace{2cm}}\)% (round off to nearest integer) of the original oil in place.

A cylindrical crude oil reservoir with a radius of 3000 ft is under water influx from a cylindrical aquifer with an estimated radius of 9000 ft. The reservoir has the following properties. 
\(\text{Aquifer thickness, } h = 40 \, \text{ft}, \text{ Porosity, } \phi = 15%, \)
\(\text{Formation compressibility, } C_f = 4.5 \times 10^{-6} \, \text{psi}^{-1}, \text{ Water compressibility, } C_w = 4.0 \times 10^{-6} \, {psi}^{-1}.\) 
Assuming a pot reservoir model with fractional encroachment angle as unity, the water influx into the reservoir for a pressure drop of 700 psi is \(\underline{\hspace{2cm}}\) MMbbl (million barrels) (round off to two decimal places).