Pressure and Rate Transient Analysis for Crossflow Test in Enhanced Geothermal Systems

Abstract

Using a semi-analytical solution for the pressure and rate transient response in multifractured enhanced geothermal systems, we developed a mathematical formulation to handle multiple wells with switching between flux control and pressure control for injector and producer. By decoupling well control, we could use a two-step approach to compute the solution effectively. We first solved the pressure and rate transient response with constant rate impulse in each well individually. Then, we combined them together to satisfy flux control and pressure control in each well. With this new semi-analytical solution, we estimated system parameters from inverse modeling for the crossflow tests in the Frisco pad of the Project Cape development, using both injection/production rate and wellhead/downhole pressure. The system parameters in consideration are fracture permeability, fracture area, rock matrix permeability, and initial reservoir pressure. Interestingly, one of the unique aspects of Frisco is that there are multiple injectors and multiple observers operating at the same time and their interactions are dependent on their connectivity through fractures – this is in distinction to the case of Utah FORGE which had only a single injector-producer pair.