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Based on the data of reservoir rock cores and 3D seismic inversion for reservoir, a comprehensive analysis was conducted using in-situ U-Pb dating of calcite cements, fluid inclusions, and geochemical data of fractured-vuggy reservoirs to investigate the key controls on the formation of reservoirs along the ultra-deep strike-slip fault zone in the depression, northern Tarim Basin, and establish the reservoir development model. The Middle Ordovician Yijianfang Formation contains tight matrix reservoirs and strike-slip faults with small displacement but relatively wide damage zone, forming a series of fault-fracture and fault-karst reservoirs which are distributed contiguously along the fault zone. Strike-slip faulting occurred during the deposition of the Yijianfang Formation, giving rise to penecontemporaneous atmospheric freshwater dissolved pores/vugs. The U-Pb ages of 440–468 Ma obtained from calcite cements in the fractures/vugs indicate that the reservoirs along the strike-slip fault zone were formed in Middle to Late Ordovician. Data of reservoir fluid inclusions, trace elements, and C/O/Sr isotopic compositions suggest that the fracture/vug cementation and filling took place in a penecontemporaneous to shallow burial stages dominated by atmospheric freshwater. On the basis of intra-platform high-energy shoal deposits, strike-slip faulting coupled with dissolution is identified as the primary control on reservoir formation and spatial distribution, and a penecontemporaneous–shallow burial strike-slip fault-controlled reservoir development model is thus proposed. Comprehensive analysis indicates that large-scale fault-fracture and fault-karst reservoirs can develop along ultra-deep strike-slip fault zone in intracratonic depression, with their scales and distribution scope controlled by the coupling of facies, faulting, and dissolution processes in the penecontemporaneous–shallow burial stages.
TIAN et al. (Mon,) studied this question.