Heat extraction characteristics of stratified production and reinjection in a single geothermal well in Shaanxi

Geothermal energy, as a key clean and renewable resource, is abundant in China, particularly in medium- to deep-layer geothermal reservoirs, which hold significant development potential. Promoting the development and utilization of medium- to deep-layer geothermal resources is crucial for optimizing China’s energy consumption structure, achieving energy savings and emissions reductions, and advancing the “Dual Carbon” goals. This study took a geothermal well in Shaanxi as an example and proposed a “lower production and upper reinjection” technical scheme implemented within a single wellbore. By comprehensively considering the dynamic heat exchange processes among the inner pipe, annulus, and surrounding formation, a 3D coupled thermal-fluid-solid model of the horizontal wellbore and reservoir was established. The model was used to investigate the effects of interlayer thickness, formation permeability and porosity, and completion tubing structure on heat extraction efficiency. Results indicated that the interlayer significantly impacted heat extraction. Without an interlayer, the extracted water temperature decreased by as much as 9°C after 30 a of stratified production and reinjection. The optimal heat extraction was achieved with an interlayer thickness of 40 m. While maintaining constant production and reinjection rates, reductions in porosity and permeability of the reinjection layer and interlayer negatively impacted heat extraction, whereas the permeability and porosity of the production layer had minimal influence.