Resource Performance at Ormat's Tuscarora Geothermal Project, Nevada

Abstract

In late 2011, Ormat Nevada, Inc. started up an 18-MW binary plant at its Tuscarora geothermal project in northeastern Nevada, USA. The project has successfully overcome two resource challenges since start-up. First, the initial drawdown in reservoir pressure was too large to allow use of the original discovery well when a downhole production pump was installed. This was rectified by drilling an additional production well with a casing configuration that allowed a greater pump-setting depth, and the plant is now operating with stable reservoir pressures. Second, the project experienced an undesirable decline in plant inlet temperatures in its first year and a half of operation. This was addressed by shutting in one injection well that was shown by tracer testing to be communicating too directly with production wells. Temperature declines at the plant inlet have now been reduced to a level compatible with long-term commercial operations. Numerical modeling of the reservoir has closely matched the trends in reservoir pressures and temperatures and has been valuable in forecasting project performance.