渤海海域前古近系深层潜山类型及其成因

锦州南潜山油田和渤中19-6潜山大气田的发现揭示出渤海海域深层潜山具有巨大的油气勘探潜力。但是,该区复杂多样的潜山结构导致潜山分类方案繁多,制约了对渤海海域潜山类型及油气成藏规律的认识。为此,基于该区已钻井和三维地震资料,在区域地质背景分析的基础上,研究渤海海域潜山地层结构和断裂分布特征,明确潜山构造特征和潜山演化动力力学机制,讨论潜山分类方案,进而评价潜山带的油气勘探潜力。研究结果表明:(1)中生代以来的历次构造运动奠定了渤海海域潜山构造的发育基础,侏罗纪—白垩纪的燕山运动主导了潜山内幕构造样式和外部形态的形成,新生代以来的晚期断陷走滑活动对潜山具有加强及定型作用;(2)渤海海域前古近系构造层自下而上可划分为太古界—元古界构造层、古生界构造层和中生界构造层;(3)潜山构造样式可划分为挤压褶皱、伸展断裂、走滑、反转、底辟等5种类型;(4)渤海海域潜山具有多成因、多结构、多岩性、多形态的复杂特征,依据潜山的"成因—结构"分类原则将其划分为2大类7小类,其中侵蚀残丘型潜山和拉张断垒型潜山具有较好的油气勘探前景。结论认为,渤中低凸起PL7-1中生界潜山与辽西凸起SZ36-1潜山具有较好的油气勘探前景,辽西凸起南端、渤海海域西部的沙垒田凸起西侧—歧口凹陷和渤中凹陷西南缓坡带是有利的潜山油气成藏区。

Type and genesis of Pre-Tertiary deep buried hills in the Bohai Sea area

The discovery of Jinzhou South Buried-Hill Oilfield and BZ19-6 Buried-Hill Gasfield reveals the immense oil and gas exploration potential of deep buried hills in the Bohai Sea area. In this area, however, complex and diverse buried hill structures lead to multiple classification schemes of buried hills, restricting the understanding on buried hill types and hydrocarbon accumulation rules in the Bohai Sea area. In this paper, the regional geological setting was analyzed. Then, based on the drilling and 3D seismic data in the Bohai Sea area, the stratigraphic structure and fault distribution characteristics of the buried hills in this area were studied, and the structural characteristics and evolutionary mechanical mechanisms of the buried hills were clarified. Finally, the buried-hill classification scheme was discussed, and the oil and gas exploration potential of buried hill belts was evaluated. And the following research results were obtained. First, the tectonic movements since Mesozoic lay a foundation for the development of the buried hill structures, the Yanshan Movement During Jurassic–Cretaceous dominates the formation of the internal structural style and external morphology of the buried hills, and the late fault-depression strike–slip activity since Cenozoic has a strengthening and shaping effect on the buried hills. Second, the Pre-Tertiary structural layer in the Bohai Sea area can be divided into Archeozoic–Proterozoic, Paleozoic and Mesozoic structural layers. Third, the buried hill structures can be divided into five patterns, i.e., compressional fold, extensional fault, strike–slip, inversion and diapir. Fourth, the buried hills in the Bohai Sea area present the complex characteristics of multi-genesis, multi-structure, multi-lithology and multi-morphology. And according to the classification principle of genesis and structure, the buried hills in the Bohai Sea area are divided into 2 types and 7 sub-types, among which the eroded residual mound type buried hill and the tensile barrier type buried hill are better in the prospects of oil and gas exploration. It is concluded that PL7-1 Mesozoic buried hill in Bozhong low uplift and SZ36-1 buried hill in Liaoxi uplift have better prospects of oil and gas exploration, and the southern end of Liaoxi uplift, the western edge of Shaleitian uplift–Qikou sag in the west of Bohai Sea area and the gentle slope belt in the southwest of Bozhong sag are favorable areas for hydrocarbon accumulation of buried hill.