Title:

Demonstration of Geothermal Energy Production Using CO2 as a Working Fluid at the SECARB Cranfield Site, Cranfield, Mississippi

Authors:

Barry FREIFELD, Lehua PAN, Christine DOUGHTY, Steve ZAKEM, Kate HART, Steve HOSTLER

Key Words:

carbon dioxide, CO2 heat mining, alternative working fluids

Conference:

Stanford Geothermal Workshop

Year:

2016

Session:

Field Studies

Language:

English

Paper Number:

Freifeld

File Size:

940 KB

View File:

Abstract:

Donald Brown presented at the Twenty-Fifth Workshop on Geothermal Reservoir Engineering at Stanford University, January 2000, a concept for using supercritical CO2 (scCO2) to produce geothermal energy. He conjectured that scCO2 would have advantages as a working fluid in comparison to water, with its much greater mobility offsetting the reduced heat capacity and density to provide better heat mining efficiency, along with lower parasitic losses due to scCO2’s large expansivity. In the intervening 15 years there have been numerous theoretical studies suggesting the benefits of using scCO2 as a heat mining fluid, but to our knowledge no field scale demonstration. To test the concept of scCO2 heat extraction, in January 2015 we operated a CO2 thermosiphon at the SECARB Cranfield Site, Cranfield, Mississippi. The Cranfield Site has been under near continuous CO2 flood since December 2009 as part of a U.S. Department of Energy demonstration of CO2 sequestration. Our well pair was perforated at a depth of 3.2 km with a reservoir temperature of approximately 127 C. The lateral distance between the producer and injector was 100 m, a distance considered pre-commercial in scale, but great enough that thermal breakthrough was still not significant after several years of injection. Instead of producing power with a turbine we extracted heat from our recirculated fluid using a heat exchanger and portable chiller. The wellfield and surface equipment were heavily instrumented to enable a comparison of numerical models with field observations. In the end our thermosiphon did not meet our predicted flow rates or energy production rates. We will explore the reasons why our predictions diverged from our observations in this presentation and make suggestions for future research needed to advance the concept of heat extraction using scCO2.


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