New Material and Technique for Matrix Stimulation in High-Water-Cut Oil Wells

Abstract

Summary A new process has been developed that effectively diverts acid away from zones with high water saturation into hydrocarbon zones. This process is designed to increase the success of matrix acidizing treatments. Because of the relative permeability effect, aqueous acid predominantly enters the zone with highest water saturation, resulting in stimulation of the water zones and 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 in some areas and additional handling equipment is required. A new nonparticulate, nongaseous material has been developed to effectively divert acid away from highly water saturated zones. The material forms a highly viscous plug when it contacts water in the matrix yet degrades when mixed with oil in the matrix of the formation. In this article we discuss in detail the diversion technique from both laboratory 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-permeability formation. Case histories showed the new material successfully diverted acid and stimulated the carbonate formations in the Permian Basin.