List of top Reservoir Engineering Questions

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).

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:

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?

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).

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, 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 $ psi and $ t = 10 $ hrs. Oil flow rate is 500 rb/day. Viscosity of oil is 1.5 cP. Thickness of the reservoir is 10 ft and formation volume factor of oil is 1.2 rb/stb.
The permeability of the reservoir is .......... mD (rounded off to one decimal place).

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

Reservoir Quality Index (RQI) based on Kozeny-Carman equation as a function ($ f $) of permeability ($ k $, in mD) and porosity ($ \phi $, in fraction) is given by: \[ {RQI} = C f(k, \phi) \] 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).

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

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

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

$ C_1, C_2, $ and $ C_3 $ are the Dietz shape factors of three reservoirs with circular, square, and rectangular 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?