塔里木盆地巴楚隆起西南缘构造特征与勘探前景

Structural characteristics and exploration prospects of the southwestern margin of Bachu Uplift,Tarim Basin

塔里木盆地中央隆起带西部巴楚隆起发育丰富的断裂构造样式。为了揭示巴楚隆起西南缘构造特征,进而为寻找有利勘探目标提供基础依据,通过对三维地震资料的精细解析,明确了断裂构造几何学特征及分布规律,并结合已知油气藏的特征,揭示了油气成藏规律。巴楚隆起西南缘主要发育扭动变形和逆冲推覆等两类典型的构造样式,NW走向的断裂多具有扭动变形特征,近EW走向的断裂则以逆冲作用为主,且都具有多期复合叠加特征,滑脱层的存在加剧了构造变形的复杂程度;近EW走向的断裂形成的圈闭完整性比NW走向的断裂相关背斜圈闭好,且膏盐岩之下的推覆体下盘构造圈闭具有较好的保存条件,和寒武系烃源岩形成完整的油气系统。寒武系盐下、盐间构造相对完整的圈闭及加里东期古构造圈闭不但具备良好的烃源岩条件,保存条件也相当优越,是下一步勘探的有利目标。

Structural faults of various styles are developed in the Bachu Uplift of western central uplift zone in the Tarim Basin.To pinpoint potential exploration targets in the southwestern margin of this petroliferous uplift,the geometry and distribution of the faults were defined through a fine interpretation of available seismic data and the connection between the faults and hydrocarbon pooling patterns was analyzed based on known reservoir characteristics.The results reveal two typical faulting styles in the margin:transpression,mostly recognized in NW-trending faults,and thrust nappe,largely found in near EW-trending faults.Both of the faults show a multi-phase composite superposition feature,which is made more complicated with the occurrence of some decollement layers.Traps formed by the EW-trending faulting is comparatively better than the NW-trending faulting-related anticline traps in terms of integrity.The structural traps in thrust nappe footwall under the gypsolyte are relatively favorable for hydrocarbon preservation,and together with the overlying gypsolyte and the Cambrian source rocks,they form a complete petroleum system.It is then concluded that the relatively integrated traps in the Cambrian pre-salt and inter-salt structures as well as the Caledonian paleo-tectonics in the margin are potential targets for further exploration with their quality source rocks and excellent preservation conditions.