| Abstract |
Geologic Derisking and mining sustainability are two indissociable concepts while contemplating geothermal resource exploration and field development issues. But, contrary to the Mining and Petroleum industries, the Geothermal Community shares no global vision of risk assessment and mitigation prior to resource reclamation. Moreover it lacks a risk evaluation methodology related to resource classification and standardised reporting codes and templates, which incidentally would act as a strong stimulus among potential investors/operators and energy/environmental planners and stake holders. Whereas a risk analysis of an Oil and Gas play would currently integrate a number of geologic, tectonic and reservoir features, a geothermal exploratory drilling application would in most instances reduce to the sole temperature and flow performance predictions, regardless of any normalized, multi-attribute, reservoir assessment. Neither is a post mortem screening systematically exercised further to well completion and testing. Recent failures, in particular in the widely developed Paris Basin, Dogger carbonate resource, have shed some light on the mining risk problematic in geothermal exploration of a reservoir; long regarded as a proven reserve of low geologic risk. Here also sustainable exploitation of the 48 operated district heating sites raises major issues addressing thermal life and well integrity expectations , which added to, injection, induced seismicity require, in tectonically active areas, adequate monitoring remedial/preventing procedures and policies. It became here obvious retrospectively that the oil and gas mining rationale would have thoroughly modified the former exploration/production strategy. The foregoing are exemplified by several case studies borrowed in most instances from the Paris Basin geothermal development. Lessons learned leads us to share a vision in which the exploration problematic would be revised, and the extensively drilled area revisited as a single development field (equivalent to an oil/gas field development) and not as a multiplicity of "exploration" (according to the mining law) doublets. Hence, the present paper aims at statistically quantifying the history of geothermal wells and field development on two reservoir case studies via a type of prior to post mortem well/campaign review. Not restricting to he exploration/resource/reserve segment, the assessment exercise advocates the need for a standard geothermal reporting code/template as already practiced or suggested by the Australian and Canadian national organization respectively. Summing up, these guidelines should provide guidance to geothermal explorationists and operators by bridging the gap between the, less mature, geothermal and, demonstrated, oil and gas know how. |