渤海莱州湾走滑拉分凹陷的构造研究及其石油勘探意义

STRIKE-SLIP AND PULL-APART STRUCTURE STUDY AND ITS SIGNIFICANCE TO PETROLEUM EXPLORATION ON LAIZHOUWAN SAG,BOHAI AREA

首次明确提出莱州湾凹陷为走滑拉分成因。估算郯－庐断裂营（口）－潍（坊）段新生代在莱州湾地区的右旋走滑量约为４０ｋｍ。利用平衡剖面计算其拉分伸展量达５～７ｋｍ，伸展率达２０％左右。根据凹陷断裂发育特征及沉降史分析结果指出：莱州湾凹陷经历了始新世的强断陷初始沉降阶段，渐新世的弱断陷、强坳陷－热沉降作用为主的断坳阶段和晚第三纪以来的区域热沉降背景上新的断裂作用（构造事件）叠加活化阶段，与一般的裂陷盆地有显著不同。探讨了其陆壳拉分伸展变形模式及其油气勘探意义，并指出其东、西两侧的走滑构造带与凹陷中央构造带是该凹陷最有前景的油气勘探区带。

This paper points out distinctly for the first time that Laizhouwan Sag is a pull-apart sub-basin that is related to the strike-slipping of Yingkou-Weifang fault in the Cenozoic. Yingkou-Weifang fault is a segment of Tan-Lu fault system,we estimate its wrench displacement in the Cenozoic is about 40km. Utilizing balance cross section technique,we calculated the pull-apart extensional length in Laizhouwan Sag is about 5-7km, extensional rate is about 20%. Further more,based on the analyses of the characteristics of fault development and the subsidence history, we find that Laizhouwan Sag had been experienced three structural evolution stages-those were the initial strong rifting stag during Eocene,the tender rifting but stronger down-warp subsidence stag during Oligocene and the tectonic rejuvenation stage under the background of thermal subsidence during Neogene. Finally, the continental pull-apart extension model in the study area has been disussed. And also points out that the strike-slip belts on the eastern and western sides of the sag and the central structure belt in the sag are the good oil and gas potential exploration zones.