酒西坳陷下白垩统近岸水下扇沉积特征及控制因素分析

酒西坳陷石大凹陷为一东断西超的中新生代箕状断陷湖盆.早白垩世早期,在右旋扭动背景下受局部拉张作用的影响,凹陷内形成了一系列NE、NNE向张扭性断裂,这些张扭性断裂控制了石大凹陷下白垩统的沉积,在湖盆陡坡带主要发育了独具特色的近岸水下扇砂岩沉积体.石大凹陷陡坡带控凹边界断层在早白垩世早期的强烈活动是导致近岸水下扇形成的决定性因素.近岸水下扇砂体常常下切到深湖--半深湖暗色泥岩,油源条件得天独厚,决定了近岸水下扇砂体具有优越的成藏条件.开展近岸水下扇沉积特征及控制因素的研究对指导断陷湖盆岩性油气藏勘探具有重要意义.

Sedimentary Characteristics and Controlling Factors of Lower Cretaceous Nearshore Subaqueous Fans in Jiuxi Depression

The Shida sag is a haif-graben fault depression lake basin which has fault in the east and onlap in the west. In Early Cretaceous, lots of transtensional faults of NE and NNE trend were formed under right lateral forces, they controlled the Lower Cretaceous sedimentation and led to nearshore subaqueous fans in the steep slope. The strong movement of the fault boundary in the Early Cretaceous epoch resulted in the formation of inshore subsea aprons. The sand bodies of the nearshore subaqueous fans cut down into the dark colored mudstones of deep lake and half-deep lake. It makes the sand bodies of the nearshore subaque-ous fans have excellent conditions of petroleum accumulation.