Page 42 - Fundamentals of Enhanced Oil and Gas Recovery

30 Amirhossein Mohammadi Alamooti and Farzan Karimi Malekabadi

K 1

H 1

K 2
H 2

K 3

3
H

Figure 1.14 Permeability and thickness variations in the vertical direction.

1.14.6.5 Factors That Influence Displacement Efficiency
1. The size and shape of the reservoir
Since the miscible thrust process includes injection operations, and since recov-
ering the oil reservoir depends on the amount of reservoir surface coated by the
displacing fluid, it is essential that the injected fluids have the maximum contact
interface with pore spaces within the reservoir. This fact becomes more compli-
cated when we know that the fluids are going to be injected into the reservoir
from a certain spot. The coated surface in the project is controlled by the geomet-
rical nature of the reservoir and the spots where the displacing fluids are injected
into the reservoir. The basic shape of the reservoir is unchangeable.
2. Constructional slope
Since the miscible thrust process is a process in which gas is the source of
mobility and energy and causes the oil to displace, separation through density is a
very important factor in providing maximum force to thrust the miscible mass and
eventually displace the oil. Extreme steepness of the oil reservoirs allows the oil to
be segregated from the gas and makes it move in front of gas, which leads to the
formation of a complete and distinctive mass of solvent that will eventually sepa-
rate gas and oil phases in motion.
3. The nature of the reservoir oil
The properties of the oil in the reservoir are determined through laboratory
techniques prior to launching the project. These properties determine the