Investigation on the effect of symmetrical multi-well layout on geothermal energy extraction from a fractured granitic reservoir: A case study in the Gonghe Basin, Northwestern China

Abstract

Reasonably designing a multi-well layout has required attention to improve the enhanced geothermal system (EGS) productivity in a fractured reservoir. The optimization of the well layout includes several constraints which depend on the geological conditions, the thermal potential of the reservoir, and the investment cost. The power generation potential of a fractured deep-seated geothermal reservoir in the Gonghe Basin, Northwestern China is analyzed and an optimized well pattern proposed. We simulate the long-term heat extraction process of EGSs of four well layouts, including the standard doublet well layout, two triplet well layouts, and a five-spot well layout. The results from multiple points such as fluid impedance, energy production, energy efficiency, and energy cost indicate that an EGS with five-spot well layout can perform better than an EGS with triplet well and doublet well layouts in a fractured reservoir. A five-spot layout EGS could yield an electric power of 6.66–9.71 MW, with the flow impedance of 0.05–0.08 MPa/(kg/s), at an energy efficiency of 19.3–70.2 over a 30-year period in the Gonghe Basin. The operation of such a system could achieve profitability in its sixth year, and the levelized cost of energy (LCOE) is 0.019–0.08 $/kWh.