Chapter 18 - Water shutoff

Abstract

This chapter is closely related to the subject of gelling agents, that is treated in detail in chapter 8. The action of both gelling and plugging agents have a similar performance: to minimize the permeability of a formation. The idea of water shutoff treatments raised already in 1922 when the injection of silicate solutions into oil producing wells with the aim at gelation in situ to form a blocking phase was patented. The developments with regard to water shutoff can be categorized into two major types. The first type is polymer gels for total water shutoff in the near-wellbore region, in which a polymer is crosslinked with either an organic or an inorganic crosslinker. The second type is concerned with deep treatment of water-injection wells diverting fluids away from high-permeability zones (thief zones). These thief zones take most of the injected water, which results in a large amount of unrecovered oil. This chapter deals with the procedures and issues of water shutoff and special chemicals used for this purpose.