渤海湾盆地冀中坳陷古潜山的三维地质结构特征

Characteristics of geologic framework of buried-hill in Jizhong depression, Bohai Bay Basin

地质结构研究是开展盆地分析与油气勘探的重要基础。渤海湾盆地冀中坳陷以古潜山油气田著称于世，潜山地质结构的精细研究是深化油气勘探、进一步获得油气发现的关键。本文基于对覆盖整个冀中坳陷的2D和3D高精度地震资料的系统解释及对钻达潜山的数百口探井资料的综合整理与分析，开展了潜山地层与断裂系统的精细解析，整体揭示了潜山的三维地质结构。研究表明，冀中坳陷内发育长城系底、寒武系底、石炭系底、中生界底、古近系底和新近系底6个区域性不整合面，据此，在纵向上划分出7个构造层。冀中坳陷内切穿潜山顶面的断裂按其走向可以分为NE、NW和近EW向3组。其中，NE向断层最为发育，NW向断层多发育于坳陷中部偏东。以近EW向的徐水-安新断层和衡水断层为界，将冀中坳陷分为北、中、南3段，各段的构造样式存在明显的差异。从潜山成因类型的角度出发，根据潜山的地层组成、构造演化、控山断层及潜山本身几何学特征等因素，在坳陷内划分出42个潜山构造带，并详细总结了重点潜山带的发育特征。前中生代的构造-沉积演化为潜山的发育奠定了良好的物质基础，印支运动和燕山运动早期的挤压事件对潜山地层有着明显的改造作用，晚侏罗世以来的多期伸展控制了坳陷内不同成因类型潜山的形成-调整一定型过程。

The study of geological structure is very important for basin analysis and petroleum exploration. The Jizhong depression in Bohai Bay Basin is known to the world for its oil and gas fields on buried-hills, hence study in detail on the geological structure of the buried hills is key to improve petroleum exploration as well as further oil and gas discoveries. Based on analysis of hundreds of exploratory wells and systematic interpretation of 2D and 3D seismic data covering most areas of the whole Jizhong depression, the paper explored the stratigraphy and the fault system of the buried hills and revealed the general 3D structure of the buried-hills of Jizhong depression. The study shows in Jizhong depression there are six reginal unconformities which are bases of Changcheng, Cambrian, Carboniferous, Mesozoic, Paleogene and Neogene, accordingly the evolution of the Jizhong depression can be divided into seven tectonic stages. Faults cutting through the top unconformity of the buried hills can be grouped into three populations according to their strikes, such as the NE-, NW-, and EW-trending. Faults striking NE is the most developed population while NW striking faults developed mostly on the central- east part of the depression, and the E-W population is most seen at the transfer zones. Jizhong depression can be divided into north, middle and south three segments by two major transfer zones such as Xushui-Anxin fault and Hengshui fault, each one with its distinguished characteristics. From the genetic point of view, combining the stratigraphic combination, tectonic evolution, dominant faults and the present geometry of the buried-hills, we delineated 42 structural zones of the buried hills and discussed the evolutionary characteristics of the most important and representative buried hills in detail. The Pre-Mesozoic tectono-sedimentary evolution provided material basis for the development of the buried-hills, the compressional events during Indosinian movement and Early ＂Yanshan movement has significantly modified the geometry of the stratigraphic units of the buried-hills, and the muhiphase rifting since the Late Jurassic has controlled the generation-adjustment-molding process of the buried-hills in Jizhong depression.