Estimations of fracture surface area using tracer and temperature data in geothermal fields

Reinjection is crucial for sustainable geothermal developments. In order to predict thermal performances due to cold-water injection, a method was developed to estimate effective fracture surface areas (i.e., heat transfer areas). Tracer response curves at production wells are analyzed to determine flow rates and pore volumes, and the fracture surface areas are optimized by short-term thermal response curves. Because the method erases fracture apertures from the equation by combining mass and heat transfer equations, the fracture surfaces can be analyzed without assuming that the fracture shape is a parallel plate. The estimation method was applied to two geothermal field datasets: One involved an artificially created reservoir, and the other involved a naturally occurring reservoir. The estimated heat transfer areas are reasonable in the field geometries. Once the fracture surface area is estimated, the future temperature change and power generation can be predicted. This can provide a simple and quick method to design reinjection strategies.