There is increasing emphasis on enhancing production and extending economic life of mature fields, especially including waterflood operations, globally. With that, it stands to reason that greater focus should be placed on controlling production of unwanted water relative to oil and gas production, as well as on improving the utilization of the large volumes of water to optimize waterflood sweep efficiency.
Mechanical and chemical treatment methods for shutting off or at least controlling, unwanted water production have existed for many years. Technologies and methods continue to evolve, albeit slowly. The same is true for injection well treatments for profile modification and improved oil reservoir sweep efficiency purposes. In the family of chemical treatments confined to production wells for controlling water rate are the so-called relative permeability modifiers (RPMs). Despite the long-standing (and continuing) skepticism of RPMs, in general, their implementation has increased in recent years - including uses in conjunction with oil and gas well stimulation treatments. Certainly, some of the criticism of RPMs is justified as they are often misapplied beyond their realistic physical and chemical capabilities. However, the creative application of RPM chemistry in production enhancement applications and in waterflood operations should not be generally dismissed or discouraged.
This paper discusses creative uses of RPM systems with properties conducive to application in both matrix and naturally-fractured sandstones and carbonates. Such applications include using RPM systems in hydraulic fracturing, acidizing, scale removal and inhibition, salt block inhibition, and waterflood injection profile modification. Both conceptual and field-proven applications are included. Results of laboratory studies and field case examples are presented.
Many of the well problems in mature fields can be attributed to the consequences of unwanted water production: Fines migration, sand production, corrosion, scale deposition, water blocks, emulsion blocks, liquid loading, water treatment and disposal challenges. These issues plague mature operations - narrowing operating profit margins and shortening well and field economic life.
Given current levels of water production worldwide (estimated at over 4 barrels of water for every barrel of oil), operators and service providers should give greater consideration to the variety of fit-for-purpose water control options they now have. One such area is the application of relative permeability modifiers (RPMs), used generically here for chemical treatments that selectively reduce water flow relative to hydrocarbon flow. RPMs have creative application potential beyond their original and understood use in reducing water production from oil (and gas) wells completed in matrix sandstone formations only.
The following sections briefly discuss successful "alternative" applications of RPMs chosen for application-specific properties.