INVESTIGATION OF HEAT EXTRACTION FROM SUPERCRITICAL GEOTHERMAL RESERVOIRS

This paper presents the outlines of a new project on "Investigation on Design Methodology of Supercritical Subsurface Boiler for Next Generation Geothermal Energy Extraction (1997-2002)" at Tohoku University. The “Supercritical Subsurface Boiler” refers to an underground heat exchanging system which takes advantage of the thermal energy transferred to supercritical water. The goal of the project is to establish the potential of supercritical water as heat extraction fluid, and to develop a design methodology for supercritical geothermal reservoirs with the objective of enhancing the geothermal energy output. The selected research tasks are concerned with (1) fracture mechanics study of the formation processes of supercritical reservoirs, (2) dynamics of supercritical reservoirs (supercritical waterrock interactions), (3) subsurface structure and stress monitoring method, and (4) thermal evaluation. Brief descriptions of the research tasks set up for the project are presented, together with recent preliminary results from the individual research tasks.