Dissolution Rates for Quartz, Aluminum-Bearing Minerals, and Their Mixtures in Sodium and Potassium Hydroxide

Abstract

Abstract High pH dissolution of quartz, aluminum-bearing minerals and their mixtures is important in several oil production processes. Rock consumption of caustic is a major limiting factor for successful alkaline waterf looding. Chemical dissolution of the gravel pack and near well-bore rock are problems in both steam and caustic flooding. Mineral dissolution is probably a contributing mechanism for the reported success of potassium hydroxide treatments in effectively and permanently stabilizing clays. The presence of even small amounts of soluble aluminum can greatly reduce the kinetics of silica dissolution in near neutral and high pH solutions. Earlier research has shown that clay minerals frequently dissolve more slowly than quartz or amorphous silica. Although these clay minerals may not themselves contribute substantially to caustic consumption, they release aluminum ions which may slow dissolution rates of other silaceous minerals. Most previous dissolution experiments have examined dissolution of single minerals. In this paper we report experimental dissolution results for quartz, kaolinite, and α-alumina and their binary mixtures in 0.1 N NaOH solutions at 70°C. Results for quartz and kaolinite in 0.1 N KOH are also described. When soluble aluminum or aluminum-bearing minerals are present, the dissolution rate of quartz is significantly reduced. Adding soluble silica can have a similar affect on kaolinite dissolution rates as measured by production of aluminum and silicon. In-congruent dissolution occurred when kaolinite solutions were shaken.