Aqueous Foams for Geothermal Drilling Fluids I: Surfactant Screening

Abstract

Aqueous foam is a promising drilling fluid for geothermal wells because it will not harm the producing formation and would eliminate the erosion problems of air drilling. Successful use of aqueous foam will require a high foaming surfactant which will: 1. be chemically stable in the harsh thermal and chemical environment, and 2. form stable foams at high temperatures and pressures. this paper presents the procedures developed to generate and test aqueous foams and the effects at 260°C temperature cycle on aqueous surfactant solutions. More than fifty selected surfactants were evaluated, with representatives from the amphoteric, anionic, cationic, and nonionic classes included. Most surfactants were severely degraded by this temperature cycle; however, some showed excellent retention of their properties. The most promising surfactant types were the alkyl and alkyl aryl sufonates and the ethoxylated nonionics.