Thermal Reservoir Characteristics and Geothermal Resource Evaluation of Qixia-Maokou Formation In Southern Sichuan Basin, Sw China

ABSTRACT China's petroliferous basins are not only rich in oil and gas, but also richer in geothermal resources (Wang et al., 2016). With the gradual deepening of oil and gas exploration in major petroliferous basins in China, a large amount of accompanying geological data provides an important way for the subsequent exploration and development of geothermal resources (Wang et al., 2020). In oil and gas exploration and development, petroliferous basins not only have abundant geological and development data, mature drilling and completion technology and reservoir fracturing and stimulation technology, but also have a large number of abandoned wells that can be transformed into geothermal wells through stimulation. It has unique advantages in the development and utilization of geothermal energy. The Sichuan Basin is rich in geothermal resources, especially in the southern Sichuan region, which is rich in medium and low temperature geothermal resources, but it also faces the problems of single utilization form and low development and utilization scale (Zhang et al., 2019). If it is reasonably developed and utilized, it is of great significance to promote the conversion of new and old thermal energy in this area and to promote local economic development. On the basis of data collection and summary of previous oil and gas exploration results, this paper determines that the geothermal gradient in southern Sichuan is mostly above 24℃/km, and the geothermal heat flow is mostly above 60mW/m2, which is a relatively high abnormal area (Xu et al., 2011; Hu et al., 2019). The thermal reservoir structure of the Qixia-Maokou Formation in the southern Sichuan region is mainly studied: the thermal reservoir thickness is 450-670 m, the burial depth is relatively shallow (mostly 2000-3000 m), the thermal storage temperature is relatively high (mostly 60-110 m) and the karst is developed, with the characteristics of layered thermal reservoirs and belt thermal reservoirs, it is a favorable thermal reservoir for the development of geothermal resources. At the same time, combined with the three-dimensional geological model established using different strata thickness, porosity distribution and lithological characteristics, the volume method is used to estimate the geothermal resources in the Qixia-Maokou Formation in this area to be 2.37×1021J, equivalent to 80.887 billion tons of standard coal. The recoverable geothermal resources are 4.74×1021J, equivalent to 16.177 billion tons of standard coal. According to the current situation of geothermal resources development and utilization in southern Sichuan and the distribution characteristics of abandoned wells in the region, I put forward my own views on the utilization prospects of geothermal resources in the region.