Cold-Water Injection into Single- and Two-Phase Geothermal Reservoirs

Abstract

Approximate analytical solutions are derived for cold water injection into single- and two-phase ìporous mediumî geothermal reservoirs. A numerical geothermal reservoir simulator is used to verify the applicability of the analytical solutions for pressure transient analysis. In accordance with these numerical results, the analytical solutions indicate that the pressure buildup behavior during injection into either a single-phase-liquid or two-phase reservoir is governed by the kinematic viscosity of the cold injected fluid. The fall-off pressures after cold water injection into a single-phase liquid reservoir (except for very early shutin times) are primarily controlled by the kinematic viscosity in situ (hot) reservoir fluid. For two-phase
reservoirs, however, the fall-off behavior is considerably more complex and cannot be fully described by the analytical solution developed in this paper.