关键词: 走滑断裂, 于奇中西部地区, 阿克库勒凸起, 成因机制, 断裂控储

Abstract: Multiple sets of strike-slip faults are developed in the central-western Yuqi area of the Akkule uplift in Tarim Basin, exhibiting complex fault characteristics and serious reservoir filling. It is essential to clarify the geometric and kinematic features, genetic mechanisms, and reservoir control effects of strike-slip faults in this area. This study focuses on multiple groups of strike-slip faults. Using fine-scale analysis techniques for small and medium-sized faults, a detailed investigation was performed on the fault orientation, density, extension length, vertical pattern, slip direction, activity intensity and phases, and genetic mechanisms. Combined with actual drilling data, the reservoir control effects of these faults were elucidated. The findings indicate that four groups of strike-slip faults are developed in the Ordovician System of the central-western Yuqi area. Among these, the dominant NNE-striking fault was formed by the coalescence of the NNE-striking segments of conjugate faults from the Tahe area and the secondary faults derived from Luntai fault. As the intermediate principal stress (σ₂) increases with depth, the NNE-striking fault develops downward, exhibiting multiple stages of inherited activity. As influenced by the basement tectonic activity of pre-existing structures and the gradual variations in σ₂, the NE-striking faults display lateral connection features at the top boundary of the Middle Cambrian system. The NEE-striking fault undergoes slow left-lateral slip due to low stress, forming a braided structure composed of Riedel shear fractures (R) and secondary co-trending shear fractures (P), which is consistent with Riedel’s left-lateral shear model. The SN-striking fault formed during the Middle to Late Hercynian period, and subsequently truncated both the NNE- and NE-striking faults. All these three faults exhibit left-lateral strike-slip characteristics. During the Middle-Late Hercynian to Indosinian period, the faults experienced a shift in their slip direction and remained active until the Himalayan period. The central-western Yuqi area primarily develops fracture- and cave-type reservoirs. The development degree of the fracture-type reservoirs shows an exponential negative correlation with the distance from the well to the faults. Strike-slip faults provide favorable conduits for corrosive fluids, facilitating the formation of cave-type reservoirs. Strong bead-like anomalies are observed in seismic profiles in the proximity of strike-slip faults with intense late-stage activity and high fluid connectivity, where both fracture- and cave-type reservoirs are more developed. These areas represent favorable targets for further exploration.

Key words: strike-slip fault, central-western Yuqi area, Akekule uplift, genesis mechanism, fault-controlled reservoir