Improving heat extraction performance of an enhanced geothermal system utilizing cryogenic fracturing

Abstract

Engineered fractures play an important role in improving heat extraction performance of Enhanced Geothermal Systems (EGS). It is possible to create these engineered fractures with cryogenic fracturing technology. Cryogenic liquid nitrogen could be used as a stimulation fluid - causing severe thermal shock. This thermal shock would lead to a well-connected fracture network in a hot, low permeability reservoir. Based on local thermal equilibrium theory, a coupled thermal-hydraulic model has been developed to simulate the heat extraction process in an EGS as a function of different fracture configurations. The proposed model is validated against analytical solutions. Using this validated model, EGS heat extraction is simulated for different stimulation scenarios. The characteristics of the temperature distribution and heat extraction are analyzed and compared for the different stimulation scenarios. The production well temperature and flow rate, as well as the potential power output over a 30 year period are calculated and compared for four scenarios. The results indicate that fracture networks created by cryogenic fracturing could significantly improve the heat extraction performance of an EGS.