Page 35 - Fundamentals of Enhanced Oil and Gas Recovery

An Introduction to Enhanced Oil Recovery 23

For downstream minus upstream pressure
2σcosθ
8μ L w v 1 8μ L o v 1
w
o
P A 2 P B 5 2 1
r 2 1 r 1 r 2 1
μ 1 μ 5 μ and L w 1 L o 5 L; so
o w
8μLv 1
ΔP AB 5 2 ΔP c1
r 1 2
For displacement of trapped oil fluid velocity in both pores must be positive;
therefore ΔP AB should be more than ΔP c1 and also more than ΔP c2 . Because of the
size structure of the pores, ΔP c1 is more than ΔP c2 .

ΔP AB . ΔP c1
8μLv 1
2 ΔP c1 . ΔP c2
r 2
1
By applying capillary pressure equations, the required velocity to push oil in a big-
ger pore (for having positive velocity in a bigger pore) can be calculated as:

σcosθr 2 1 1
v 1 . 1 2
μL r 1 r 2

1.14 MICROSCOPIC DISPLACEMENT OF FLUIDS IN THE
RESERVOIR (ED)

An essential part of any EOR process consists of the ability of the injected fluids
to displace oil in the pore space at a microscopic scale. The microscopic displacement
efficiency, E D , has a significant impact on the success or failure of a project. For crude
oil, microscopic efficiency depends on the magnitude of residual oil (S or ) at the end of
the process where the displacing fluid is in contact with the displaced fluid.
Nonetheless, since the EOR processes are usually associated with the injection of
many slugs, the efficiency of each of the fluids is different in the porous environment
of the reservoir. Moreover, low efficiency leads to early fingering phenomenon and
consequently to poor performance in the injection process [1].
Capillary and viscous forces and viscosity of fluids and their mobility in porous
media are among the important parameters affecting the microscopic displacement
that are worth investigating as a research topic.

1.14.1 Macroscopic Displacement Efficiency
The oil efficiency in each displacement depends on the volume of the reservoir in
contact with the fluid injected. The Volumetric Sweep Efficiency is a measure that