Carbon sequestration potential of the Habanero reservoir when carbon dioxide is used as the heat exchange fluid

摘要

The use of sequestered carbon dioxide(CO_2) as the heat exchange fluid in enhanced geothermal system(EGS) has significant potential to increase their productivity, contribute further to reducing carbon emissions and increase the economic viability of geothermal power generation. Coupled CO_2 sequestration and geothermal energy production from hot dry rock(HDR) EGS were first proposed 15 years ago but have yet to be practically implemented. This paper reviews some of the issues in assessing these systems with particular focus on the power generation and CO_2 sequestration capacity. The Habanero geothermal field in the Cooper Basin of South Australia is assessed for its potential CO_2 storage capacity if supercritical CO_2 is used as the working fluid for heat extraction. The analysis suggests that the major CO_2 sequestration mechanisms are the storage in the fracture-stimulation damaged zone followed by diffusion into the pores within the rock matrix. The assessment indicates that 5% of working fluid loss commonly suggested as the storage capacity might be an over-estimate of the long-term CO_2 sequestration capacity of EGS in which supercritical CO_2 is used as the circulation fluid.