New material and technique for matrix stimulation in high-water-cut oil wells

A new process has been developed that effectively diverts acid away from zo nes with high water saturation into hydrocarbon zones. This process is desi gned to increase the success of matrix acidizing treatments. Because of the relative permeability effect, aqueous acid predominantly enters the zone w ith highest water saturation, resulting in stimulation of the water zones a nd an increase of water cut. Although foam can be used to divert acid from the "aquifer" to the damaged oil zones, nitrogen is not readily available i n some areas and additional handling equipment is required. A new nonpartic ulate, nongaseous material has been developed to effectively divert acid aw ay from highly water saturated zones. The material forms a highly viscous p lug when it contacts water in the matrix yet degrades when mixed with oil i n the matrix of the formation. In this article we discuss in detail the diversion technique from both labo ratory testing and field studies. Laboratory tests conducted in a dual-core flow apparatus showed excellent diversion from a water-rich zone to an oil -rich zone, as well as from a high-permeability formation to a low-permeabi lity formation. Case histories showed the new material successfully diverte d acid and stimulated the carbonate formations in the Permian Basin.