Effects of the Injection Temperature on Injection-Capacity of Geothermal Wells

Numerical Simulation on the Measured Downhole Pressure

Abstract

An injection test on Sumikawa well SD-1 was carried out to evaluate the effect of water temperature on injection-capacity. It was conclude that injecting low temperature water increases the permeability-thickness product and the injection flow rate owing to increase in fracture aperture and decrease in reservoir pressure around the injection well. To examine quantitatively this behavior, we have conducted numerical studies using a one-dimensional slab geometry model. Considering the relationship between porosity, permeability, and pressure/temperature, a modified Kozeny-Carman relation was applied to a vertical, one-dimensional slab geometry model, where the fracture-porosity and permeability should increase as a result of cooling in the reservoir. Consequently, we explain the improvement of transmissivity as a result of porosity increase due to low temperature water injection. We also explain that the decrease in reservoir pressure around the injection well is induced by the downward flow of low temperature water and the cooling reservoir where the fracture system has a strongly vertical orientation.