Heat Extraction Evaluation and Well Pattern Comparison of Abandoned OilWells Converted into Geothermal Wells

Geothermal energy development has many advantages, but well construction accounts for half of the total costs, which restricts the promotion and utilization of geothermal energy. Some abandoned oil wells have abundant geothermal resources and converting them into geothermal wells for heat extraction can significantly reduce costs and improve economic efficiency. Moreover, the reservoirs that reach the economic limit of water cut can also be used for heat extraction to achieve co-production of heat and oil. Currently, most research on heat extraction from geothermal well patterns focuses on fixed well patterns or/and does not consider oil-water two-phase flows. However, the oil-water flow and heat transfer characteristics of different well patterns are of great significance for the design and adjustment of geothermal development schemes of oilfields. Therefore, a heat-flow coupling model considering oil-water two-phase flows was established. The production characteristics of diverse well patterns were compared, such as production temperature, pressure difference between injection and production, liquid production, and oil production. Research shows that the maximum difference of the production temperatures and pressure differences between diverse well patterns can reach 22.56 K and 1.03 MPa, respectively. When the injection wells and production wells are cross-symmetrically distributed, the heat extraction system has the highest production temperature and oil production, as well as a lower pressure difference between injection and production. The research reveals the evolution characteristics of temperature and pressure fields during heat extraction from different well patterns, providing a basis for designing and adjusting the well patterns and some guidance for the evaluation of the co-production of heat and oil in oilfields.