GAS-WATER-ROCK INTERACTIONS IN SANDSTONE RESERVOIRS: IMPLICATIONS FOR ENHANCE RE-INJECTION INTO GEOTHERMAL RESERVOIRS AND CO2 GEOLOGICAL SEQUESTRATION

Much geothermal energy is stored in sandstone reservoirs in sedimentary basins in China, which is being extracted for direct use of heat. However, the injection rate of waste water is rather low for these reservoirs. Studies on gas-water-rock interactions in sandstone reservoirs have flourished in the last decade due to the need for enhanced oil recovery and the fact that deep saline aquifers in sedimentary basins are promising candidates for geological sequestration of CO2. Experiments at laboratory and field scales and numerical modelling of various scales have been carried out. It has been shown by these studies that porosity and permeability of the sandstone reservoirs would increase as a consequence of CO2 injection. Further tests at the field scale are suggested to verify these predictions and with an attempt to overcome the bottle neck technology in sustainable exploitation of geothermal energy from sandstone reservoirs.