Geothermal Resource Evaluation In The Sichuan Basin and Suggestions For Development and Utilization of Abandoned Oil and Gas Wells

Geothermal and petroleum are two kinds of resources coexisting in sedimentary basins. The distribution area of oil and gas fields in sedimentary basins is often also an area where geothermal resources are widely distributed. Therefore, the exploration, development, and utilization of geothermal (oilfield geothermal), that is, geothermal resources in oil and gas areas, is one of the key tasks for the evaluation of medium-low temperature (≤ 150 ℃) hydrothermal geothermal resources in sedimentary basins. As an important oil and gas basin in China, the Sichuan Basin is also rich in hydrothermal geothermal resources. Based on the collection of relevant data and the summary of previous oil and gas exploration results, a three-dimensional geological model is established by using different formation thicknesses, porosity distribution, and lithology in the Sichuan Basin. Combined with the rock thermal physical parameters, geothermal gradient, and terrestrial heat flow data in the Sichuan Basin, the temperature of different thermal reservoirs is calculated by a one-dimensional thermal steady-state conduction equation. Finally, the geothermal resource intensity and resource amount of different thermal reservoirs are calculated by volume method. The results show that the Sichuan Basin is rich in geothermal resources, and there are seven sets of potential geothermal reservoirs. The total resources of geothermal reservoirs reach 4.26 × 1013GJ, equivalent to 1450.4 billion tons of standard coal. Among them, the potential geothermal resources of the Qixia-Maokou Formation are the largest, reaching 1.36 × 1013GJ, equivalent to 464 billion tons of standard coal. The Permian Qixia-Maokou Formation in the southern Sichuan Basin has the condition of priority development and utilization of geothermal resources and has the characteristics of the highest formation water temperature, the largest current water production, and cumulative water production. According to the characteristics of geothermal resources in the Sichuan Basin and the formation temperature of the abandoned oil and gas wells, the abandoned oil and gas wells are divided into two categories, and different utilization methods of geothermal resources are proposed: Class I wells: This type of well has a formation temperature greater than 90 ℃, and the current water production is high. It can be used for ORC low-temperature geothermal power generation, and then geothermal cascade utilization based on power generation tail water; type II well: the formation temperature is between 60 ℃ and 89 ℃, which forms a solar-geothermal energy system to generate electricity, and then cascade utilization of geothermal resources. This study lays a foundation for the future screening of abandoned oil and gas wells and the geothermal development of oil fields.