Abstract

The petroleum industry is becoming ever more dependent on increasing oil production from existing oil fields beyond the recovery in primary production and water flooding. Enhanced oil recovery employs various chemicals to increase the reservoir volume contracted by oil well injected fluids, ie, to increase the volumetric sweep efficiency, and thus increase production. Increases in the oil displacement efficiency can be brought about by a variety of mechanisms. The primary processes used to increase oil displacement efficiency are miscible gas flooding and steam flooding. Micellar polymer flooding and alkaline flooding may also be used. Miscible gas flooding most often employs carbon dioxide and/or hydrocarbon gases. Polymer flooding increases the volumetric sweep efficiency of waterflooding. The two most commonly used polymers used are partially hydrolyzed polyacrylamides and xanthan gum. Polymer injection followed by in situ cross-linking reduces the permeability of fractures and rock thief zones increasing volumetric sweep efficiency. Injection of surfactants and noncondensible gases to generate foam in situ also increases volumetric sweep efficiency.