准噶尔盆地玛湖凹陷大油（气）区形成条件与勘探方向研究

准噶尔盆地西北缘玛湖凹陷是全球著名的湖相富烃凹陷,最新勘探成果展示出大油(气)区特征。为及时总结,丰富发展当代中国特色叠合盆地油气地质理论与勘探实践,本文主要分析了这一大油(气)区的基本形成条件与勘探领域。结果表明,玛湖凹陷大油(气)区得以形成主要缘于三大有利基础条件:前陆碱湖优质高效烃源岩、立体输导体系、三类规模有效储层与储盖组合,由此造就油气在充足的烃源条件下,沿立体的输导体系,被三套区域性盖层有效封盖,向着三类规模有效储层,在有利圈闭中运聚成藏,因此油气富集规律可归纳为"源-输控烃、储-盖控藏"。相应,按目的层和圈闭类型形成了三大有利油气成藏领域,由浅至深依次为三叠系下统百口泉组岩性油(气)藏群、二叠系下统风城组致密油、石炭系—下二叠统大构造油气藏群。玛湖凹陷大油(气)区的勘探突破缘于勘探理念创新,具有巨大勘探潜力和基础科学研究意义。

Study on the Forming Conditions and Exploration Fields of the Mahu Giant Oil (Gas) Province, Junggar Basin

The Mahu sag in the northwestern Junggar Basin, NW China, is a well-known petroliferous sag globally. Recent exploration results indicate a geological framework of a giant oil (gas) province. Therefore, to perform an on-time summary is of significance to improve the theory and exploration practice of modern petroleum geology in Chinese superimposed basins. In this paper, we mainly address the forming conditions and exploration fields of this hydrocarbon province. Results indicate that the forming conditions can be divided into three aspects, including high-quality alkaline lacustrine source rocks formed under foreland settings, well-developed multiple types of migration pathways, and three types of effective reservoirs and reservoir-cap rock assemblages. As a consequence, large amounts of oil and gas migrated along multiple types of pathways and accumulated in the three types of reservoirs and favorable traps under the effective sealing of three sets of caprock sequences. Thus, the oil and gas enrichment rules can be summarized as source-migration control the primary hydrocarbon accumulation and reservoir-caprock control the hydrocarbon pool formation. Accordingly, there are three hydrocarbon accumulation fields, from top to bottom including stratigraphic oil (gas) plays in the Lower Triassic Baikouquan Formation, tight oils in the lower Permian Fengcheng Formation, and structural oil and gas plays in the Carboniferous to lower Permian. The exploration breakthrough of the Mahu giant oil (gas) province is initiated by theoretical innovations, which has huge exploration potential and fundamental scientific significance.