中东扎格罗斯盆地:沿走向变化的构造及油气特征

扎格罗斯盆地是全球富含油气的前陆盆地,沿走向不同构造段的油气储量规模差别巨大,各段构造特征及其对油气富集和主控因素的认识是海外超前选区选带的重要基础。本文综合分析沿盆地走向(NW-SE向)的土耳其迪亚巴克尔段、伊拉克基尔库克段以及伊朗洛雷斯坦段、胡齐斯坦段和法尔斯段等5段的构造特征、油气成藏特征及其主控因素。结果表明:扎格罗斯盆地沿走向各段油气2P可采储量差异明显,胡齐斯坦段和基尔库克段储量规模最大,且以新近系储层为主;扎格罗斯造山作用形成一系列背斜构造、不同时期形成的蒸发盐岩盖层影响盆地各段油气聚集差异;中新世以来,随着阿拉伯板块与欧亚板块的持续碰撞,扎格罗斯盆地发生了大规模的挤压褶皱作用,下白垩统油气沿裂缝向上运移至渐新统-中新统优质储层中;基尔库克段和胡齐斯坦段新生界沉积物厚度较大,渐新统-中新统蒸发岩为优质的区域性盖层,对新生界油气的保存起重要作用;法尔斯段构造变形较为强烈,三叠系之上的上侏罗统、中新统蒸发岩受不同程度的破坏,油气主要分布于下三叠统-上二叠统碳酸盐岩。通过本研究将对中东扎格罗斯盆地的新项目评价具有一定的指导意义。

Zagros basin in Middle East: Along-strike variations of structure and petroleum accumulation characteristics

The Zagros basin is one of the most important petroleum-bearing foreland basins in the world, with quite different reserves of different sections along strike. To understand structural characteristics, oil and gas accumulation and the controlling factors is an important foundation when developing the oversea new venture evaluation. We take the the synthetical analysis of the along-strike (NW-SE) structural deformation differences, hydrocarbon accumulation and the controlling factors of the Diyarbakir section of Turkey, the Kirkuk section of Iraq, and Luristan, Khuzestan and Fars sections of Iran. The results show an obviously different 2P recoverable reserves of oil and gas along the strike in the Zagros basin. The Khuzestan section has the largest reserves and is dominated by Neogene reservoirs. The Zagros orogenesis forms a series of anticline structures, and the evaporite caprock forming in different periods affects the oil and gas accumulation differences in various sections of the basin. Since the Miocene, with the continuous collision between the Arabian plate and the Eurasian plate and the large-scale compression and folding occurring in the basin, the Lower Cretaceous hydrocarbon can migrates upward to the Oligocene-Miocene reservoirs along the fractures. The Cenozoic sediment is quite thick in Kirkuk and Khuzestan sections, and the Oligocene-Miocene evaporite can be a quite good regional caprock. The deformation in Fars section is strong, and the Upper Jurassic and Miocene evaporites are destroyed in different scale and the hydrocarbon mainly accumulates within the Upper Permian to Lower Triassic carbonate reservoirs. This study will provide the guidance of the new venture evaluation of the Zagros basin.