The Xinjiang oilfield faces the challenges such as complex reservoir type, strong reservoir heterogeneity, and low recovery efficiency. Considering the requirements for petroleum industry to meet China’s “dual carbon” goals, and through literature review, laboratory experiments, integration of key technologies, and field application in typical reservoirs, this paper proposes a theory of full-domain CO2 flooding to effectively guide the significant enhancement of oil recovery through CO2 flooding in highly heterogeneous reservoirs. A coupling mechanism between displacing medium (CO2) and reservoir characteristics across three dimensions (space domain, time domain, and fluid domain) is established to maximize the mobilization of crude oil in pores and throats of varying scales. Consequently, a series of key CO2 flooding technologies featuring full-reservoir coverage, full-scale adaptation, full-cycle optimization, and full-process integration have been formed. Field applications of the full-domain CO2 flooding theory and associated technologies in the Xinjiang oilfield have demonstrated remarkable results, with the estimated recovery enhancement by over 20%. This theory provides a new idea/approach for the efficient development of various complex reservoirs in the Xinjiang oilfield, but also lays a theoretical foundation for the significant EOR in complex reservoirs across China. It is promising, industrially and economically, for application in other oilfields.
Geothermal resources, as clean and stable non-carbon-based energy sources, are of great significance for China to achieve its “Dual Carbon” goals. The geothermal resources in the Junggar Basin have been insufficiently studied. This paper discusses the distribution of present geothermal field and performs the evaluation of geothermal resources in the western uplift of the Junggar Basin. Based on the high-quality, continuous temperature measurement data from 11 wells, the distribution characteristics of geothermal gradient and terrestrial heat flow were analyzed. Using the one-dimensional steady-state heat conduction equation, the planar distribution of temperature in the strata shallower than 5 000 m was revealed. On this basis, the geothermal resources of 7 sets of geothermal reservoirs (including the Carboniferous and above systems) were evaluated. The results show that, in the western uplift of the Junggar Basin, the average geothermal gradient is (21.3±3.0) ℃/km, and the average terrestrial heat flow is (43.9±6.9) mW/m2. In the Zhongguai bulge, a relatively high-temperature anomaly area, the average geothermal gradient is (23.3±2.8) ℃/km, and the average terrestrial heat flow is (47.9±5.8) mW/m2. The formation temperature at a depth of 4 000 m ranges from 78.0 ℃ to 122.9 ℃ in the western uplift, with an average of 100.7 ℃ in the Zhongguai bulge, indicating a good geothermal potential. The geothermal resources are estimated to be 411.24 EJ in the study area, with the largest quantity (132.61 EJ) endowed in the Permian, followed by the Carboniferous (121.52 EJ). The largest fluid resources are registered by the Cretaceous, reaching 19.58 EJ. This study provides key parameters for the development and utilization of geothermal resources in the western uplift and also offers a methodological reference for geothermal evaluation in other areas of the Junggar Basin.
