An Empirical Injection Limitation in Fault-Hosted Basin and Range Geothermal Systems

Abstract

Volumetric methods of predicting sustainable megawatt outputs of fault-hosted geothermal systems in the Basin and Range Province have not been particularly accurate because they cannot assess cooling due to recycling of injectate. Two to three decades of production experience from four fault-hosted geothermal systems empirically shows that it is possible to sustainably extract +20 megawatts of electrical energy from a mile of fault length with initial production temperatures of 480 to 500 oF and up to about 15 MW/mile of fault length from reservoirs with initial temperatures near 400 oF. The most common limiting factor is cooling due to recycling of injectate. The highest injection density to date for a sustainably operating plant supplied from a fault-hosted system is at Beowawe where up to 3600 gpm/linear mile of fault length is occurring. Attempted injection rates of >10,000 gpm/mile of utilized fault length have twice resulted in rapid cooling commencing within weeks to months.