Optimization and Simulation of Geothermal Resources Development In Longchuan Basin

The Longchuan basin in western Yunnan is a Neogene rift basin located in the Yunnan-Tibetan high temperature geothermal belt. The basin is characterized as a ‘hot basin’ by high heat flow (75 to 90 mW/m2). The basin has thin sedimentary layers (≤2km), granitic basement with low porosity and low permeability is the potential dry hot rock target in the study area, in consideration of that the rock temperature ranges in 150-180℃ at a depth of 5000m. In this study, the measured temperature and thermal parameters (inter-well distance, injection-production rates, etc.) were adopted to establish a hot-dry rock target model to analyze the influence of different exploitation parameters on the mining efficiency and the total heat within 50 years. The results showed that the inter-well distance of production-rejection and the production flow rate should be the main consideration for production. In other words, the inter-well distance of production and rejection is proportional to the exploitation temperature persistence, and the production flow rate is inversely proportional to the exploitation life. Besides, different well distribution patterns also have a significant impact on exploitation efficiency. The ‘Double Injection-Production’ mode provides higher energy productivity than the ‘Single Injection-Production’ one within 50 years, which is the common understanding on the exploitation life of hot-dry rock resource. The mining efficiency of 1.66 × 1015 J/a can be obtained from a hot-dry rock target with a thickness of 300 m and an area of 2km×2km using the ‘Double Injection-Production’ exploitation mode with a well distance of 100m and an injection-production rate of 140m3/h. Based on the above simulation and the extent of dry thermal rock distribution in the study area, the hot-dry rock mining efficiency in the study area can be inferred as 5.20×1016 J/a.