Sustainable electricity generation from an Enhanced Geothermal System considering reservoir heterogeneity and water losses with a discrete fractures model

Abstract

Electricity production from Enhanced Geothermal System (EGS) is faced with premature thermal breakthrough due to the preferential flow path of the geofluid which is the consequence of the reservoir heterogeneity. Heat extraction investigation has been performed with assumptions of no water losses, isotropic and homogeneous reservoir. However, EGS reservoir is heterogeneous due to the preexistence of natural fractures and different formations. Water injection under high pressure causes water losses from reservoir boundaries to surrounding formations. Considering reservoir heterogeneity, permeability anisotropy, and water losses is required for reliable assessment of heat extraction. These important aspects were considered in this study and the effects of reservoir heterogeneity, water losses, wells spacing, wells orientation, regional flow direction, injection temperature on system performance with a discrete fractures model were analyzed. Neglecting water losses and assuming homogeneous reservoir overestimate the system performance. The maximum electric power is obtained for vertical wells with 540 m of wells spacing, the thermal breakthrough time is 25.6 years, and the average electric power is 9.7 MWe. Water losses from 0% to 10% lead to a decrease in energy efficiency from 2.4–2.2 to 2.3–2.1. The regional flow direction from the production well to the injection well improves the system performance.