南堡凹陷沉降史分析

Analysis of the Subsidence History in Nanpu Sag

孙风涛 郭铁恩 田晓平

SUN Fengtao GUO Tieen TIAN Xiaoping

中海石油(中国)有限公司天津分公司勘探开发研究院, 天津塘沽 300452

Exploration and Development Research Institute of CNOOC Ltd, Tianjin Branch, Tanggu Tianjin 300452, China

南堡凹陷是渤海湾内小型断陷盆地,近年来油气勘探取得不断突破。相对而言,对于其整个盆地构造和沉降演化规律的认识仍十分薄弱,而研究构造活动控制下的沉降史对于研究油气特征及有利区带的预测具有重要的意义。采用回剥法对南堡凹陷的构造沉降速率进行恢复,在此基础上进行了构造期次的划分。研究认为受到区域构造运动的控制,南堡凹陷总体上可以划分为裂陷期、凹陷期和裂后加速沉降期三个阶段,其中古近系整体表现为幕式沉降的特征,即Es34+5为裂陷Ⅰ幕、Es33-Es2为裂陷Ⅱ幕、Es1为裂陷Ⅲ幕、Ed3-Ed1为裂陷IV幕。回剥法是进行地史恢复的有效方法,为研究构造活动控制下的沉降史提供了理论基础。

Nanpu Sag is a small scale fault basin in Bohai bay, and great breakthrough has been made in recent years in oil and gas exploration. Comparatively speaking, the understanding about the basin structure and subsidence evolution is poor. The research of subsidence history is very importance for the research of oil and gas and forecast the favorable structural belts. With back stripping method, tectonic subsidence rate of Nanpu Sag has been restored, and the phases of tectonic activity have been divided. Controlled by tectogenesis, the tectonic subsidence of Nanpu Sag can be divided into three phases, including rifting phase, depression phase, and post rift accelerated subsidence phase. Paleogene is charactered by episodic subsidence. Es34+5 is phase I rifting episode, Es33-Es2 is phase Ⅱ rifting episode, Es1 is phase Ⅲ rifting episode, Ed3-Ed1 is phase Ⅳ rifting episode. Back stripping method is an effective method for geohistory restoration, providing theoretical basis for the research of subsidence history.

https://doi.org/10.3969/j.issn.1008-2336.2012.03.029