走滑断裂特征对油气勘探方向的选择——以塔中北坡顺1井区为例

通过三维地震精细解释,运用断距分析、断层生长指数等方法,探讨了塔中北坡顺1井区走滑断裂的几何学特征、活动期次及其成因机制。该区走滑断裂及其伴生构造具有明显的分层特征,同时又具有分段差异:西段构成基底走滑卷入的"负花状"构造,东段则表现为盖层滑脱型。加里东中期(Ⅲ幕)基底走滑断裂已开始活动;海西早期,走滑断裂再次活动,上奥陶统桑塔木组厚层泥岩起到滑脱层的作用,基底走滑断裂剪切引起的盖层变形,在志留系发育伴生雁列正断层及其地堑、地垒组合;海西末期,挤压应力沿NE走向释放减弱而出现构造分异,基底走滑断裂西段再次复活,并与雁列正断裂上下贯通构成"负花状"构造;之后在印支期持续活动,发育断层相关褶皱等。海西末期-印支期,基底卷入型走滑断裂油气运移通道的开启、志留系等构造圈闭的定型与主成藏期具备良好的时空配置关系,走滑断裂附近可发育奥陶系岩溶。 

Fault characteristics and their petroleum geology significance:A case study of well Shun-1 on the northern slope of the central Tarim Basin

The geometric characteristics, active stages and formation mechanism of strike-slip faults in well Shun-1 area on the northern slope of the central Tarim Basin were studied through 3D seismic interpretation and combined with fault throw and fault growth index analyses. The study area has clear layered characteristics. Deep structures are mainly of linear strike-slip faults; middle structures are primarily normal faults which group sinistralen echelon and form horst-graben structures, locally forming negative flower structures with a basement strike-slip fault. Small-scale normal faults are developed in shallow structures. Basement strike-slip faults have formed in the middle Caledonian and activated again associated with en echelon normal faults in Silurian during the early Hercynian. The thick Sangtamu Formation mudstone of the Upper Ordovician is identified as a detachment layer, which resulted the decollement between the basement strike-slip fault and its cover. This region has experienced magmatism and widespread extension in the late Hercynian. The rejuvenation of basement strike-slip faults resulted in the local strong compression in the latest Hercynian and fault-related folds in the Indosinian.In the latest Hercynian, basement strike-slip faulting was linked with en echelon normal faults, which could be favorable hydrocarbon migration paths. Strike-slip induced folds cut by en echelon normal faults, forming faulted anticlines, faulted nose and fault blocks, could be favorable traps for petroleum accumulation. The Ordovician palaeokarst that developed extensively near strike-slip fault zones, is an important future target for petroleum exploration.