Secondary recovery stimulation techniques and chemicals

The use of waterflooding has grown rapidly and there are currently waterflood projects underway in nearly all oil-producing areas. Since waterflooding involves the injection of large quantities of water into underground formations, many problems are encountered which are not normally associated with producing wells. Until the past few years, some of these problems were not correctly diagnosed and methods of maintaining or increasing injectivity were limited to conventional acidizing and hydraulic fracturing techniques. Within the past 3 or 4 yr, stimulation techniques have been developed primarily for problems related directly to water-injection wells. Two of these new injection well-stimulation methods have been widely used and have proved highly successful. the first of these removes permeability damage caused by bacterial activity. The second increases relative permeability of the formation to water by removing much of the residual oil saturation from the formation near the well bore of the injection well. The use of these methods should be limited to wells where an analysis of well conditions shows the problem to be one that can be solved by the application of these techniques.