中国西部含油气盆地石油地质条件的主要认识和勘探方向

Some recognitions of the petroleum geological feature and exploration directions in the western China

我国西部的盆地基本上都属于小型克拉通盆地 ,其石油地质特征可以概括为 :①盆地主要为叠合盆地 ,具有多期构造发育史 ,造成油气资源分散 ;②多套烃源岩复合叠置 ,多阶段成烃演化与油气多期成藏 ;③两套构造层和多套沉积沉序形成多种储集类型 ;④多套沉积层序和后期构造运动控制的油气多期成藏决定了勘探的多目的层和勘探工作的复杂性 ,晚期成藏现象尤其值得重视 ;⑤油气藏类型多。各层系圈闭和油气藏类型丰富 ,前陆盆地冲断带主要是构造型 ,克拉通区油气藏类型主要是构造、岩性、地层和复合型油气藏。根据这些石油地质特征 ,西部地区的重点勘探领域主要分布在继承性的古隆起区、前陆盆地和正向构造上的岩性地层带。参照西部地区年均新增探明油气储量的趋势 ,未来 10年内年新增探明油气可采储量可保持在 0 5～ 0 7亿t和 15 0 0～2 0 0 0亿m3 。

The basins of western China are composed of small crust massifs and their petroleum geological features can be summarized from five aspects. The first feature is that in terms of plate movements, the western basins has experienced several times of tectonic events and subsidence, which made the hydrocarbon resources dispersed. The second feature is that the western basins have multiple overlapping petroleum systems with multiple source rocks, multiple phases of source rock evolution and multiple times of hydrocarbon accumulation. Different area of each basin has its own main source rocks. The Paleozoic source rock is mainly centralized in the craton area and the Mesozoic source rock is mainly centralized in foreland basin and depressions. The third feature is that the western basins have two tectonic strata and multiple sedimentary sequences, which determines that there exists multiple reservoirs. The fourth feature is that the western basins have multiple source-reservoir-seal combinations, which determines the multiple targets and the complex exploration. The fifth feature is that the western basins have different kind of pools. In the foreland over-thrusts, oil and gas occur mainly in Mesozoic and Cenozoic strata, structural pools are the dominating type. In the cratonic area, oil and gas occur both in Paleozoic and Mesozoic strata with multiple types of pools including tectonic pools, lithologic pools and composite pools. According to these features, the most important exploration fields are centralized in paleo-uplift, foreland basin and stratigraphic and lithologic pool on the positive structures. In the past ten years, the annual oil and gas reserves have been increasing quickly. It is estimated that the annual oil and gas reserves will increase 50-70 million tons and 150-200 billion cubic meters in the next 10 years.