Subject:      Enhanced Oil Recovery

Topic:      Factors Common To All EOR Methods

OUTLINES

 

 

—Introduction.

—Factors on which efficiency of an EOR method depends.

—Reservoir characteristics.

—Fluid Characteristics.

—Types of injection well location.

 

 

INTRODUCTION

 

—Enhanced oil recovery is the recovery of residual oil that is done by injecting various materials into the reservoir, which lacks internal energy, sufficient enough to produce naturally at economical rates.

—The efficiency of an EOR method is a measure of its ability to provide greater Hydrocarbon recovery than by natural depletion, at an economically attractive rate

Efficiency Of An EOR Method Depends On:

 

 

—The reservoir characteristics.

—The nature of displacing and displaced fluids.

—The arrangement of injection and production wells.

Following are some of the most important    characteristics of reservoir:

—Average Depth.

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—Structure, in particular the dip of the bed.

—

—Degree of homogeneity.

—Petrophysical Properties (porosity, permeability, wettability, capillary pressure etc).

Average Depth

—Reservoir depth has an important influence on both the technical and economical aspects of an EOR project.

—Technically, a shallow reservoir puts a restraint on the injection pressure that can be used, since this must be less than the fracture pressure.

—Economically, the cost of an EOR project is directly related to depth.

 

Dip

 

 

—Hydrocarbon recovery from a porous medium is greater when gravity plays a part than when it does not.

—NOTE: Gravitational forces are only truly effective in reservoirs having high permeability or in which the dip is unusually high.

 

 Homogeneity

—In order to have high HC recovery, there should be no impediment (restriction) to fluid flow within reservoir.

—Possible impediments may be of tectonic                 (e.g. isolating faults) or stratigraphic nature.

—In faulted and fissured reservoirs, and those with high permeability streaks, channelling allows the displacing fluid to bypass some of the oil in place and leads to low recovery.

 

Petro physical Properties

—Porosity: Higher the porosity and higher the residual oil saturation after natural recovery phase, more attractive  an EOR project becomes.

—Permeability: High permeability is encouraging for an EOR project. However, higher the permeability greater is the chance that the natural recovery will be so high that any EOR project would be uneconomic.

 

The influence of fluid charateristics:

—The principal fluid property to be taken into account when designing an EOR project is  the viscosity.

—If the fluids are highly viscous the displacement velocities will be low, since the applied pressure gradients are limited.

—Oil production will be at such a low rate that it will not be economically attractive.

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