A study on geothermal resources and their structural heat accumulation mechanisms based on abandoned oil and gas wells

The oil and gas development in the Luzhou Area of the Sichuan Basin has entered a mature stage, charactericed by a large number of abandoned wells with high warter-cut. Research on the redevelopment of its geothermal resources holds strategic significance for achieving the region's "dual carbon"goals. The study area located on the Indosinian Luzhou-Kaijiang paleo-uplift, hosts the Qixia-Maokou Formation of the Permian, recognized as the region's most significant karst-type geothermal reservoir. This formation exhibits the typical features of a basin-type, stratabound, medium- to low-temperature geothermal system. Drawing on geological, seismic, drilling, and logging data, this study analyzes the reservoir-caprock assemblages, temperature distribution, and structural characteristics of the area. Findings reveal that geothermal heat accumulation in the paleo-uplift zone results from a combined mechanism of heat conduction, concealed fault-driven heat convection, and thermal radiation reflection. A volumetric approach was used to quantitatively assess geothermal resource reserves. The results indicate that crustal uplift from the Indosinian Luzhou paleo-uplift, together with fault development caused by Himalayan and Yanshan tectonic movements, facilitated the accumulation of deep geothermal fluids in the Luzhou area, forming a distinctive tectonic heat accumulation system. The estimated geothermal resources in the Qixia-Maokou Formation total 2.894×10²⁰ J, equivalent to 9.87×10⁹ tons of standard coal, demonstrating substantial potential for geothermal development in the region.