莱州湾凹陷东部新生代走滑构造特征及油气勘探意义

莱州湾凹陷位于渤海南部海域,为中生界基底之上发育的新生代半地堑.郯庐断裂带分东西两支穿过莱州湾凹陷东部,在新生代盖层中表现出渤海最复杂最典型的为NNE向的右旋走滑断裂特征.其中东支断裂在渐新世以后活动强烈,发育多条NNE向走滑断层及NE向伴生断层组成的复杂断裂带.走滑断裂带内断层展布符合右旋单剪作用下的脆性走滑剪切模式,地震方差切片存在右旋运动拖拽断裂证据.通过对主断裂活动期次分析表明,研究区主要有三期大的构造活动,同时形成了三期构造反转.应力分布的局域性导致了形变特征的差异性,产生了褶皱、挤压反转、掀斜断块、花状构造等典型的构造类型.研究区首次利用三维地震资料对本区构造特征进行了分析,研究认为走滑活动形成了良好的构造背景、优越的油源及运移等成藏条件,具有较大的油气勘探潜力.

Cenozoic Strike-slip Tectonic Character and the Significance of Oil and Gas Exploraton in Eastern Laizhou Bay

Laizhou bay sag is located in the south of Bohai sea region, being a Cenozoic half-graben developed on the basement of Mesozoic. Tan-Lu fault belt is divided into two fault branches, the west fault branch and east fault branch, running across Laizhou bay sag, being the most complex and typical NNE direction dextral strike-slip fault belt in Cenozoic. The east branch fault was extremely active after Oligocene, resulting in the development of a number of NNE direction strike-slip faults and NE direction associated faults, forming complex fault belt. The fault distribution within strike-slip fault belt is consistent with the brittle shear model of dextral simple shear. The dextral drag faulting evidence can be seen on seismic variance slices. Through analysis of phases of fault activities, it is indicated that this area has experienced three major tectonic activities, forming three tectonic inversions. Due to the regional distribution of dextral stress field, the deformation characteristics is different, resulting in the formation of multi-type structural styles, such as folds, compression inversion structures, tilted fault blocks and flower-shaped structures. In the study area, the tectonic characteristics has been analyzed for the first time with 3D seismic data. The result shows that this area has excellent tectonic setting, predominant source rocks and good hydrocarbon migration conditions, and the hydrocarbon exploration potential is great.