Profile Modification and Water Control With Silica Gel-Based Systems

Abstract

ABSTRACT A major problem in maximizing oil production potential is the maintenance of adequate mobility control and favorable permeability profiles within the reservoir. Currently, polymer systems are receiving a great deal of attention in this application, not only as viscosifying agents, but also as cross-linked/gelled water blocking agents. Traditionally, silica gel systems had been used for such purposes. They still offer advantages in situations where polymer systems are limited by degradation and syneresis or are inadequate to shut off major thief zones. This paper presents the chemistry of silica polymer gel systems, and reviews their properties, benefits, limitations, and methods of application. The properties such as gel time, strength, and shrinkage vary considerably versus the concentrations of reactants, the type of acidifying/gelling agent used, or the particular reservoir environmental conditions such as temperature, salinity, hardness, and hydrocarbon saturation. Gels ranging from elastic to rigid can be made with set times varying from a few seconds to several hours. Inorganic acids and reactants such as CaCl2 or NaAlO2 tend to react quite rapidly. Organic reactants that slowly hydrolyze or oxidize give more gradual formation of gels. Most reservoirs that contain high salinity, hardness, or temperature environments tend to accelerate the gel formation. Examples of these effects are presented for several silicate based systems. Also the gelation of silicate in the presence of organic chemicals is discussed. Information from the grouting literature is reviewed so that a complete picture can be presented on the use and application of silicate based water control and production methods.