A semi-analytical model to predict the heat extraction from an enhanced geothermal system with multiple wells and areal flow

In order to meet the rapidly increasing demand for energy supply, multiple wells have been used to improve the output productivity and performance of an Enhanced Geothermal System (EGS). As the output performance of an EGS is affected by many factors, such as number and placement of wells, direction and magnitude of areal flow and flow rates, reservoir optimization is an important topic in EGS design. In this paper, a semi-analytical model is developed to study the heat extraction from a multiple-well (some for recharging and the others for production) geothermal reservoir, where fluid circulates in a single, planar hydraulic fracture with a constant hydraulic aperture. The effect of parallel areal flow across the well field is included in the analysis. The streamline function and velocity potential method used in the authors' previous work (Wu et al., 2013) is extended to the current problem. A comparison of the flow behaviour and temperature evolution in a given well layout with and without areal flow is carried out. The results show that the areal flow plays an important role in affecting the temperature distribution and thus the EGS output performance. Therefore, the well layout needs to be optimized when there exists areal flow.