University of Houston - Reservoir Engineering Assignment Solution

This document presents a comprehensive solution to a petroleum reservoir engineering assignment. The solution addresses two primary problems: calculating the initial gas in place and initial gas reserves for a volumetric dry gas field, and analyzing whether an oil company can publicly announce additional oil reserves. The first problem involves detailed calculations using provided parameters like area, thickness, porosity, connate water, and gas formation volume factors at different pressures. The second problem delves into the justification for public announcements of additional reserves, considering technical proof and economic factors. Additionally, the solution outlines two enhanced oil recovery (EOR) methods that reduce oil viscosity: gas injection and thermal injection, explaining how these methods increase oil recovery. The gas injection method, also known as miscible flooding, involves injecting gases like carbon dioxide to reduce oil viscosity and maintain reservoir pressure. Thermal injection utilizes methods like steam flooding to heat the crude oil, reducing viscosity and enhancing permeability. References to relevant petroleum engineering literature are also included.

PETROLEUM RESERVOIR ENGINEERING 1
Petroleum Reservoir Engineering
Name of student
Course
Date

PETROLEUM RESERVOIR ENGINEERING 2
1. A volumetric dry gas field with 640 acres and 10ft pay thickness has an initial pressure of
6800 psia, a porosity of 12.2 percent, and connate water of 27 percent. The gas formation
volume factor at 6800 psia is 0.0024 cu-ft/scf and at 1500 psia is 0.0124 cu-ft/scf.
(a) calculate the initial gas in place in standard billion cubic feet.
(b) calculate the initial gas reserve in standard billion cubic feet, assuming an abandonment
pressure of 1500 psia
provided parameters
p1 = 6800 psi
vg.f = 0.0024 cu-ft/scf.
porosity= 0.122
connate water = 0.27
gas volume factor at 1500 psia = 0.0124 cu-ft/scf
therefore; we first determine the initial gas available
G = 43560 AL O(1−Swt )
Bgi
where, A -= the area of the reservoir in acre
= 640 acres
L = thickness of reservoir,
= 10
replacing back;
G = 43560∗640∗10∗0.122(1−0.27)
0. 0024
= 1.034 * 10 ^ 10 SCF

PETROLEUM RESERVOIR ENGINEERING 3
determination of initial gas reserve
G = 43560∗640∗10∗0.122(1−0.27)
0. 0 124
= 0.2 * 10 ^10 scf
gas reserve = G – G ab
= 1.034 * 10 ^ 10 scf - 0.2 * 10 ^10 scf
= 0.834 * 10^10 scf
2. Big oil company identify 100 barrels crude oil under the ground of uhv campus (assume
technically proved), can big oil company make an announcement that they have additional
100 barrels reserve in public and why?
Big oil company can go public and make an announcement on the additional barrels. The
reason behind this is that if we assume that the additional barrels can be technically proved, it,
therefore, implies that the extra amounts are proved reserves and for the purposes of economics,
can be declared publicly (Ezekwe, 2010).
3. List two enhanced oil recovery methods that enhance oil recovery by reducing oil viscosity;
explain how these enhanced oil recovery methods increase oil recovery.
The two methods include gas injection and thermal injection
 Gas injection

PETROLEUM RESERVOIR ENGINEERING 4
Also known as miscible flooding, this method is one of the enhanced oil recovery
techniques. The approach is to introduce miscible gases into a reservoir. A process known as
missile displacement then maintains the pressure within the reservoir, as well as enhancing the
displacement of oil since there is a reduction in the tension between the water and the oil. It is
also known as the elimination of the interface existing between the interacting fluids. The
purpose is to enable total displacement efficiency. The gases which are utilized include natural
gas, carbon dioxide and nitrogen (Ezekwe, 2010).
Mostly, carbon dioxide is the one used as it assists in the reduction of the oil viscosity
and also it is less costly as compared to other gases. This method depends on the phase behavior
of the crude and gas mixture to increase the process of oil recovery. Some parameters which are
also significant in the process is the pressure, temperature as well as the composition of the oil.
 Thermal injection
This approach applies a number of methods to heat the crude oil in order to lessen the
rate of viscosity as well as the mobility ratio. The pool which is heated as well can vaporize and
thereafter condense thereby resulting in enhanced oil. The various techniques include
combustion, steam flooding and steam injection. All the methods enhance displacement
efficiency as well as the sweep efficiency (Terry et al., 2015).
Taking steam flooding as our case, the heat is introduced into the reservoir through the
pumping of steam. With time, the steam will condense forming hot water, leaving the oil to
evaporate and later on expand upon the formation of the hot water. The outcome is that the oil
will expand, making the viscosity to drop and its permeability enhanced. To enhance this process
in contemporary society, solar EOR is applied, which utilizes solar arrays to concentrate the
energy from the sun to heat and then generate steam.

PETROLEUM RESERVOIR ENGINEERING 5
References
Ezekwe, n. (2010). Petroleum reservoir engineering practice. Pearson education.
Terry, r. E., rogers, j. B., & craft, b. C. (2015). Applied petroleum reservoir engineering. Pearson
education.