Assessment of connectivity between source rocks and strike-slip fault zone in the Fuman oilfield, Tarim Basin

The formation of hydrocarbon reservoirs in the Tarim Basin is significantly influenced by strike-slip fault zones, whose connectivity with source rocks is vital for hydrocarbon migration and accumulation. The 3D seismic data helps us to assess the connectivity of source rocks with the F_Ⅰ17 strike-slip fault zone in block Ⅱ of the Fuman oilfield using both a discrete element model (DEM) for Riedel shear structures and a perfectly plastic medium-stress ascending function model. The findings reveal that the drag-point depth (h) of the en echelon faults of F_I17 during the Late Hercynian obtained by theoretical calculation is far less than that measured by the Riedel shear DEM. This discrepancy suggests that the strike-slip faults of F_Ⅰ17 originated from T-tensional rupturing rather than R-shear rupturing. The average depths of source rocks connected to the F_I17 reach up to 9-18 km, suggesting that this fault zone acts as an immediate channel for the migration of hydrocarbons generated by the underlying source rocks of the Yurtus Formation at a burial depth of over 10 km to the overlying fault-karst (or fractured karst) traps of the Ordovician to form reservoirs. The depth (H) of source rocks connected to the F_I17 zone increase from north to south. Parameters of the fault-controlled hydrocarbon reservoirs of F_I17 zone, such as crude oil density, natural gas dryness coefficient, and hydrocarbon charging stages and their respective contributive degrees, are closely associated with the connectivity of F_I17 zone with source rocks. Thereby, such connectivity plays a role in controlling hydrocarbon accumulation, with the controlling effects varying with the order, along-strike segmentation, activity intensity, and strike-slip fault-cut strata. The connectivity of the F_I17 with source rocks changes significantly along the fault strikes, which affects the efficiency of vertical hydrocarbon transport.