Water Injection as a Means for Reducing Non-Condensible and Corrosive Gases in Steam Produced from Vapor-Dominated Reservoirs

Abstract

Large-scale water injection at The Geysers, California, has generated substantial benefits in terms of sustaining reservoir pressures and production rates, as well as improving steam composition by reducing the content of non-condensible gases (NCGs). Two effects have been recognized and discussed in the literature as contributing to improved steam composition, (1) boiling of injectate provides a source of "clean" steam to production wells, and (2) pressurization effects induced by boiling of injected water reduce upflow of native steam with large NCG concentrations from depth. In this paper we focus on a possible additional effect that could reduce NCGs in produced steam by dissolution in a condensed aqueous phase.

Boiling of injectate causes pressurization effects that will fairly rapidly migrate outward, away from the injection point. Pressure increases will cause an increase in the saturation of condensed phase due to vapor adsorption on mineral surfaces, and capillary condensation in small pores. NCGs will dissolve in the additional condensed phase which, depending upon their solubility, may reduce NCG concentrations in residual steam.

We have analyzed the partitioning of HCl between vapor and aqueous phases, and have performed numerical simulations of injection into superheated vapor zones. Our simulations provide evidence that dissolution in the condensed phase can indeed reduce NCG concentrations in produced steam.