Development characteristics of Paleozoic strike-slip fault and its control on traps in Fuman Oilfiled, Tarim Basin

The Paleozoic ultra-deep strike-slip fault-controlled fracture-vuggy reservoirs in the Fuman Oilfield represent a focal point for hydrocarbon exploration and development in the Tarim Basin. However, current research on the regional development characteristics, evolutionary phases, and the governing principles of these strike-slip faults remains scarce. In this study, based on newly acquired 3-D seismic data from the Fuman Oilfield, and seismic planar attributes such as coherence and likelihood, we have conducted a refined interpretation of the spatial distribution patterns of the strike-slip faults. By integrating structural features of unconformities, the intersectional relationships of faults, and sedimentological characteristics of the strata, the active periods of the strike-slip faults are clarified. Concurrently, the classification and summary of trap types and their characteristics have been based on the correlation between reservoir attributes and the spatial arrangement of faults. The research reveals that the planar distribution of strike-slip faults across the 3D surveys of the Fuman Oilfield exhibits distinct zonal characteristics, categorizable into four deformation zones: the oblique zone of faults, the boundary-restricted zone, the main fault development zone, and the weak fault development zone. The Paleozoic strike-slip faults within the Fuman Oilfield can be stratified into three structural deformation layers from the deep to shallow: the deep structural deformation layer (below TЄ₃), the middle structural deformation layer (TЄ₃-TO₃t), and the shallow structural deformation layer (TO₃t-TP). In the deep structural deformation layer, the basement generally exhibits rift structures with weak strike-slip fault activity; in the middle structural deformation layer, strike-slip faulting is intense, with most developing positive flower-like structures near the top surface of the Ordovician carbonate rocks; in the shallow structural deformation layer, en echelon normal faults associated with the reactivation of strike-slip faults are widely developed, and they exhibit a vertically layered distribution characteristic. The evolution of the strike-slip faults can be delineated into three principal phases of activity: the Middle to Late Cambrian, the Middle to Late Ordovician, and the Silurian-Carboniferous. The majority of these faults ceased activity by the Middle to Late Ordovician, with only a few large, later reactivated strike-slip faults remaining active into the Silurian-Carboniferous. The scale and positioning of reservoir development are significantly influenced by the spatial distribution of the faults. Under the sealing of lateral dense bedrock and the Upper Ordovician caprock, fault-controlled fracture-cave traps are formed. Based on the geometric characteristics observed on the fault plane, the traps can be further classified into six distinct types: pinnate, braided, linear, horsetail, diamond superimposed, and soft connection types.