| Abstract |
Any finite quantification of the “capacity” of a geothermal resource implicitly involves a start point and an end point for energy extraction. The issue addressed in this paper is: at what time and why does energy extraction cease from a geothermal resource, and what are the implications for resource assessment? The point of cessation can be referred to as the “end point” and the reason for cessation as the “failure mode”. The objective of this paper is to define the various ways that geothermal energy extraction development can be quantified and might have to cease, and then look at to what extent these can be built into predictive models. Useful insights can be gained from experience in “conventional” geothermal projects based on high temperature naturally convective systems with long operating histories, in excess of 50 years in some cases. This study is theoretical in the sense that to date, no whole geothermal power schemes anywhere have been decommissioned due to the resource reaching the end point and failing (though individual plants have ceased to operate). However, this will eventually be the case. These issues will became increasingly important in Australia as projects move from Inferred Resource estimates to higher Resource and Reserve categories. |