Research on circulating heat recovery law of single horizontal well for hot dry rock geothermal resources

Abstract

Hot dry rock is essential to geothermal resources because of its advantages of clean green, good stability, large reserves, and high utilization coefficient. However, there are few large-scale and commercial mining schemes due to increased development costs, induced earthquakes, and low recovery during fracturing. Based on the above background, the concept of hot dry rock development for circulating heat recovery in the single horizontal well is put forward, injection and recovery of circulating working fluid are realized by single horizontal well, interchange of hollow pipe in well with liquid flow passage in wall annulus is realized by the fast connection of flow passage transformation, and flow direction control of thermal fluid is recognized by its unique bottom hole structure, to achieve the goal of cleanliness, low energy consumption, and high-efficiency heat recovery, to achieve the purpose of avoiding a series of problems caused by reservoir fracturing. A mathematical model has been created to calculate heat recovery efficiency in a single horizontal well. This model analyzes the impact of critical parameters in mining hot dry rock geothermal resources from single horizontal wells. The results show that the flow rate of circulating working fluid, the wellbore’s horizontal section length, and the formation’s thermal conductivity greatly influence thermal recovery. For instance, a domestic hot dry rock project can recover heat up to 3.08 MW through cyclic mining with a single horizontal well over 30 years.