环玛湖凹陷二叠—三叠系沉积构造背景及其演化

准噶尔盆地玛湖凹陷是已被证实的富油凹陷，以二叠、三叠系砂砾岩扇体油气藏著称于世。揭示扇体发育的构造—沉积环境，是探索构造、气候、地形等因素之间耦合关系的重要窗口，也是进一步评价油气勘探潜力、加快勘探开发进程的重要基础。利用新的钻探与地球物理勘探资料，从“源—汇系统”的概念出发，揭示该区二叠系—三叠系的构造及沉积背景。研究表明，玛湖凹陷是在石炭纪之前的褶皱基底基础上，受周缘冲断活动控制而形成的石炭纪—第四纪凹陷；二叠纪—三叠纪为玛湖凹陷的主要沉积充填期，经历了晚石炭世—早二叠世的造山后伸展、中二叠世—中三叠世挤压逆冲以及晚三叠世克拉通内拗陷的演化过程，主要发育冲积扇—扇三角洲—湖泊沉积体系；冲断活动的幕式发育与前展式迁移、撕裂断层与横向构造转换带（区）形成的优势搬运通道、干旱的气候环境等因素控制了玛湖凹陷周缘规模巨大的扇三角洲体系。伸展背景下风城组的碱湖沉积提供了优质烃源岩，其上的扇三角洲体系提供了有利的储集体，上三叠统厚层泥岩构成区域盖层，共同形成了一个完整的含油气体系。玛湖凹陷含油气潜力巨大，多层系立体勘探前景广阔。

Tectono-Depositional Setting and Its Evolution during Permian to Triassic around Mahu Sag,Junggar Basin

Mahu sag in Junggar basin is proved to be rich of oil and gas, and famous for its Permian and Triassic oil and gas pools in sandy conglomerate fans. To discuss the tectono?depositional setting for the development of fan bodies is an important clue to explore the coupling among the tectonic, the climatic, and the geomorphic processes, is a foundation for appraisal of petroleum exploration potential, and an accelerator for petroleum exploration and development. Based on the newly-acquired drilling and geophysical exploration data, the paper is to disclose the tectono?depositional setting during Permian to Triassic Period from a point of view of sedimentary source to sink concept. The study result shows that the Mahu sag is a depression of Carboniferous to Quaternary built upon the pre?Carboniferous folded basement. The Permian to Triassic saw its dominant period of sedimentary filling, and underwent such evolution processes as the post?orogenic extension during Late Carboniferous to Early Permian, the compression and thrusting during Middle Permian to Middle Triassic, and intra?cratonic depression in Late Triassic, during which alluvial fan, fan delta, and lake sedimentary systems were mainly developed. The episodic and breaking?forward thrusting, the priority transportation pathways made up of tear faults and lateral transfer zones and the arid environment controlled the large?scale fan delta systems in and around Mahu sag. It is an integrated petroliferous system with the Fengcheng formation mudstones in the extensional alkaline lacustrine facies as the excellent hydrocarbon source, the overlying fan deltas as the favorable reservoirs, and the Upper Triassic thick mudstone as the regional cap rock. The Mahu sag is of great potential for oil and gas, and has a board prospect for multi-layer stereoscopic exploration