Performance analysis of pinnate horizontal well in enhanced geothermal system

•Feasibility of enhanced geothermal system with pinnate horizontal wells is studied.•Total heat production is improved by 21.4% with pinnate horizontal wells.•Effect of wells structure on heat extraction performance is evaluated.•Reliable layout of pinnate horizontal well is presented. The well layout is crucial for improving the utilization of hot dry rock geothermal resources. In present work, a three-dimensional enhanced geothermal system (EGS) with pinnate horizontal well is proposed. Furthermore, the effect of pinnate horizontal well structure on the heat extraction performance of present EGS is numerically investigated. For scCO2-based EGS and water-based EGS, the stable heat extraction state and a competitive heat production can be obtained by present EGS. Compared with the conventional EGS with doublet system, the production temperature and the total heat production of EGS with pinnate horizontal well increase by 21.54 K and 21.4 %, respectively. The heat extraction performance of EGS with pinnate horizontal well is positively correlated with the main well bore number and length. In comparison, the branch well structure and number have less effect on the heat extraction performance. Consequently, main wellbore number with 3 or main wellbore length with 300 m can be taken as criterion for the design of the main wellbore. Besides, the branch well with staggered pattern, inclination angel of 60° and the number of 4, is proved to be the optimum arrangement.