塔里木盆地富满油田走滑断裂带通源性评价

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

塔里木盆地走滑断裂带对油气藏形成具有控制作用,走滑断裂带与油源连通性对油气运移、聚集非常重要。基于3D地震资料,运用Riedel剪切离散元模型和完全塑性介质-应力上升函数模型,对塔里木盆地富满油田Ⅱ区块FI 17走滑断裂带油源连通性进行了评价。研究结果显示:①FI 17走滑断裂带海西晚期雁列断裂拖曳点深度(h)理论计算值远小于实测值,表明其走滑断裂T张破裂成因,而非R剪切断裂。②FI 17走滑断裂带通源深度平均达9~18 km,表明该断裂能够将其下伏埋深10 km以下的玉尔吐斯组烃源岩生成的油气直接输导至上覆奥陶系断(缝)溶体圈闭中聚集成藏。③FI 17走滑断裂带通源深度(H)自北而南增加,其断控形成油气藏中的原油密度、天然气干燥系数、油气充注期次及各期次贡献度与油源连通性密切相关,表明油源连通性对油气聚集具有控制作用。走滑断裂级别、走向分段性、活动强度和断穿地层不同,控制作用也不同。油源连通性会沿着走向发生显著变化,影响油气垂向输导效能。

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 FⅠ17 strike-slip fault zone in blockⅡof 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 FI 17 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 FⅠ17 originated from T-tensional rupturing rather than R-shear rupturing.The average depths of source rocks connected to the FI 17 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 FI 17 zone increase from north to south.Parameters of the fault-controlled hydrocarbon reservoirs of FI 17 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 FI 17 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 FI 17 with source rocks changes significantly along the fault strikes,which affects the efficiency of vertical hydrocarbon transport.