Principal controlling factors of oil and gas accumulation and key exploration targets in southwestern Tarim Basin

The Lower Cambrian Yuertus Formation and the Carboniferous Kalashayi Formation in the southwestern Tarim Basin have high-quality source rocks. The paleotectonic framework and evolution of fault activity are well aligned with the critical periods of oil and gas charging, and the reservoir-cap configuration is favorable. Recently, multiple wells have achieved industrial oil and gas flows, presenting a multi-layer, multi-type three-dimensional exploration potential. However, significant differences exist in the controlling factors of accumulation and exploration directions among different strata. Focusing on the Cambrian effective source rock development zone, the Maigaiti slope, the Hetian and Maixi peo-uplifts, and three major domains, this study systematically investigated the main controlling factors of oil and gas accumulation and key breakthrough directions in key strata of the southwestern Tarim Basin. The main target areas of the Cambrian in the Maigaiti slope included: (1) grain shoal facies developed under a gentle slope setting of the Xiaoerbulake Formation in the western segment (favorable area exceeding 100 km²); (2) progradational bodies in the Upper Cambrian Awatag Formation in the eastern Yuzhong area of the central segment; and (3) subsalt structural-lithologic traps in the Yudong-Yuzhong structural belt in the eastern segment. For the Ordovician carbonate rock in the Hetian paleo-uplift and its peripheral structural zones, exploration was mainly focused on stable areas of continuous tectonic movement and inherited active fault zones in hydrocarbon-generating depressions, which were favorable target areas for late-stage oil and gas charging. The key challenge was the formation and preservation of large-scale reservoirs. Critical zones included: six break-back thrust nappe structural belts and karst superposition areas in the Yudong fault-fold area, and three strike-slip faults plus fractured-vuggy body superimposed areas with bead-like strong reflections in the Yuzhong low uplift. Seismic imaging of small-scale fractured-vuggy bodies under multiple-wave interference conditions was strengthened. The Upper Paleozoic in the Bashituo area of the Maixi paleo-uplift remained in a structural high position after the Hercynian period and received dual-source supply from the Cambrian and Carboniferous, providing favorable oil and gas accumulation. In the updip direction, targets included high-energy shoal facies of the bioclastic limestone section of the Bachu Formation and the lithologic-structural traps of the Donghetang Formation. In the Yuepuhu block, targets were the favorable traps of the high-energy shoal facies of the Xiaohaizi Formation. A series of acquisition, processing, and interpretation techniques with amplitude preservation and fidelity enhancement for improving seismic resolution were adopted to achieve accurate prediction of thin and tight sandstone reservoirs.