西湖凹陷始新世平湖运动的地质表征及其油气地质意义

Geological Characterization of the Eocene Pinghu Movement in the Xihu Sag and Its Hydrocarbon Geological Significance

针对西湖凹陷始新世平湖运动认识不深入的问题,以三维地震资料精细解释和综合地质分析为基础,系统总结了西湖凹陷平湖运动的地质表征。研究表明,平湖运动是西湖凹陷一次重大的构造事件,控制了始新世伸展应力场从前平湖组沉积时期的北西-南东向转为平湖组沉积时期的北西西-南东东向。在平湖运动过程中,西湖凹陷构造变形和沉积充填发生了巨大变化,早期强烈活动的北东向断层逐渐弱化,而北北东向断层开始兴盛,控制着沉降中心从凹陷北部迁移至中部,岩浆活动从凹陷周缘向内部集中。平湖运动作为对西太平洋构造域在始新世一次重大运动学调整事件的响应,影响了西湖凹陷平湖组煤系地层的展布,具有重要的理论研究和勘探实践意义。

The Pinghu Movement is an important Cenozoic tectonic process, but its influence on the Xihu sag is still unclear. Based on three-dimensional(3 D) seismic data interpretation and comprehensive geological analysis, the geological characteristics of the Pinghu Movement in the Xihu sag are systematically summarized. The study shows that the movement was a major tectonic event in the Xihu sag, controlling the extensional stress field transformation in the Eocene Xihu sag. The extensional direction was NW-SE before the movement, and changed to NWW-SEE after the movement. Because of the Pinghu Movement, the tectonic deformation and sedimentary filling of the Xihu sag changed greatly. The early NE-trending faulting gradually weakened, while NNE-trending faulting began, migrating the subsidence center from the northern part of the sag to the middle part. The magmatism was concentrated from the periphery of the sag to the interior. As a response to a major kinematic adjustment of the Eocene West Pacific tectonic system, the Pinghu Movement has affected the distribution of coal-bearing sequences of the Pinghu Formation in the sag.