Chemical Method for Formation Plugging

Abstract

The chemical process described here has proved to be an effective method of preventing fluid movement out of or into a wellbore. This process provides a strong, durable plug at normal formation temperatures as well as under steam injection conditions where most plugging methods fail. Introduction Control of fluid movement, from the wellbore into earthen formations or from the formation into the wellbore, is a universal problem in the oil industry. Injection profile control is an integral part of most assisted recovery or steam stimulation programs. Premature entry of water or gas into the producing Premature entry of water or gas into the producing wellbore in both primary and assisted recovery operations also creates many problems. Numerous mechanical, physical, and chemical techniques have been used to try to overcome these problems. The most commonly used technique is cement problems. The most commonly used technique is cement squeezing, a method that is much less effective than generally recognized. Cement, a particulate material that cannot penetrate formation matrix to any great depth, forms a filter cake on the formation face that often breaks down under pressure. Mechanical packers are used to isolate zones in a wellbore. packers are used to isolate zones in a wellbore. This technique is effective if the wellbore is cased and good cement bonding exists between the casing and formation. Lost circulation materials are often used to form a filter cake, which impedes fluid flow into thief zones; for the most part, noted improvements are temporary. A number of chemical processes for plugging or reducing formation permeability are commercially available. These processes range from pumping two chemical solutions into the formation to mix and form an insoluble precipitate to using relatively sophisticated polymer systems that are chemically activated prior to pumping into the matrix where they set up at a later time to form a gel or solid that plugs and reduces permeability. All are based on true solutions that can be pumped through matrix. The success of these techniques depends on the formation being treated (matrix or fracture plugging, carbonate content, etc.), volume of chemical used (large volume treatments are recommended with gel-forming systems to assure coverage), and the precautions taken to assure proper fluid placement. None of the commercial processes proper fluid placement. None of the commercial processes are recommended for steam injection wells. We have developed a chemical method for permanent formation plugging that has a number of permanent formation plugging that has a number of advantages over commercially available processes. In the following pages the process, process fluids, laboratory development, and field applications are summarized and discussed. Process Description Process Description This new process is based on the acid-catalyzed polymerization of furfuryl alcohol resins. It is polymerization of furfuryl alcohol resins. It is applied by injecting an acidic solution into the interval to be plugged, followed by the resin solution. The two solutions mix in the formation to start a rapid, vigorous, exothermic reaction forming a hard solid that fills the pore space (or fracture). JPT P. 559