Operational Aspects of Placing Proppant in a Naturally Fractured Geothermal Reservoir

Abstract

For the past twelve years the Camborne School of Mines has been researching a geothermal water flood system in naturally fractured igneous rocks (hot dry rock) at Rosemanowes Quarry in Cornwall. For the past four years circulation has been carried out on an experimental reservoir, at a depth of 2.5 km with a bottom hole temperatures of less than 100°C. One of the targets of the preset circulation program was to investigate the use of proppant to improve the hydraulic performance of the reservoir. This was the first large scale proppant injection to be carried out in a hot dry rock (HDR) system and was designed to show whether the technique of placing proppant could be a beneficial part of developing a reservoir. The objective of the experiment was to treat an isolated open hole section of the production well to demonstrate: the ability to place proppant into natural fractures in a crystalline rock, the effects of the proppant on the hydraulic behavior of the reservoir. The experiment was successful and carried out according to plan. It demonstrated that the technique of placing proppant into natural fractures had been effective. Initial results have shown an improvement in the production recovery, although further long term steady state circulation is required to quantify this. This paper outlines the operational planning and implementation but does not include details of the treatment design or of the resultant change in hydraulic performance.