Oil Recovery by a Water-Driven Steam Slug

Abstract

Abstract Results of an experimental study of oil recovery by a steam slug driven by a cold waterflood in a linear porous medium are described. The model included simulation of heat losses to the adjacent formations. Steam displacements were conducted, using a number of hydrocarbons and various steam-slug sizes, with the core initially containing a residual oil or irreducible water saturation. It was found that the steam-slug displacement is more efficient in the case of light oils than for the heavier ones. The injection of cold water following steam resulted in almost total condensation of the steam present in the porous medium, with the process degenerating into a hot waterflood. The oil process degenerating into a hot waterflood. The oil recovery efficiency of the process depends on whether an oil bank is formed during the steam-injection phase and whether the oil responds favorably to a hot phase and whether the oil responds favorably to a hot waterflood. Introduction Steam injection has been shown to be an effective oil recovery method both by field and laboratory tests. However, the method has the inherent disadvantages of a high cost of operation and excessive heat losses. The modification discussed here consists in the injection of cold water after a slug of steam, which helps to offset the above disadvantages partly at the expense of oil recovery. The injected water serves to propel the oil bank formed ahead of the steam-invaded zone and transports the heat contained in the steam-swept zone farther downstream, thus leading to more complete utilization of the heat injected.