Coupled Processes Analysis of Flexible Geothermal Production from Steam- and Liquid-dominated Systems: Impact on Wells

Abstract

We present results from a study on the potential impact of flexible geothermal production on production rates, well integrity and reservoir behavior. The impact on production rates and well integrity is performed by coupled process modeling based on linking a reservoir-wellbore simulator with a geomechanical simulator, whereas potential scaling is analyzed by geochemical modeling. We consider both steam- and liquid-dominated geothermal systems using data from The Geysers and Casa Diablo geothermal fields, California. The simulations related to well integrity show that production-induced temperature and pressure changes can cause non-linear mechanical responses, including frictional sliding at material interfaces and material yielding. However, if the production rates are controlled between certain limits, e.g., ramping up production slowly and not completely shutting down the production in each cycle, the impact on the well assembly can be minimized. Geochemical simulations show that the effects of flexible production on scaling and corrosion in a liquid-dominated system can be controlled by keeping the wellhead pressure above the saturation pressure and at the same time keeping the temperature above the silica saturation temperature.