费尔干纳盆地油气成藏特征及其主控因素分析

费尔干纳盆地是位于中亚地区南天山山系中呈负向地形的坳陷，受基底断裂和区域构造活动控制，形成3个不同的构造层系。盆地基底为褶皱造山条件下形成的强烈变质的古生代地层，中部的盆地盖层沉积为中生代至古近纪拉张裂谷稳定沉降条件下形成的，最上部为新近纪至现今造山阶段形成的磨拉石建造。费尔干纳盆地主要发育中下侏罗统湖相沼泽相泥页岩、上白垩统乌斯特里奇组区域海侵层和古近系海相泥岩和泥灰岩等3套烃源岩；发育侏罗系、白垩系、古近系及新近系等4套含油气储集层系；且区域性盖层、准区域性盖层和局部盖层发育，形成了良好的生储盖组合。受构造变形和沉积环境控制，主要发育构造型、构造—地层型和地层(岩性)型3大类型油气藏(田)。第四纪早期的构造活动控制了盆地内油气田的最终分布，扭断层破坏了已有的圈闭并为烃类向上覆新近系储层的运移提供了运移通道，造成大量烃类气体散失。

CHARACTERISTICS OF HYDROCARBON ACCUMULATION IN FERGANA BASIN AND ITS CONTROLLING FACTORS

The Fergana Basin is a large depression in the southern part of the Tianshan Mountains. Controlled by basement faults and related tectonic activities, three tectonic layers are defined in the basin. The basement of the basin consists of strongly metamorphosed Paleozoic deposits by folding orogeny, and the middle tectonic layer is the sedimentary cover deposited in the stable phase of the tensional rift from Mesozoic to Paleogene, while the uppermost tectonic layer is the molasse deposits after the orogenic stage since Neogene up to the present. Three sets of source rocks have been found in the Basin, which include marine mudstone and marl of Paleogene, regional transgressive deposits of upper Cretaceous and lacustrine and swamp mud shale of Middle and Lower Jurassic. There are four sets of reservoir systems in the basin in Jurassic, Cretaceous, Paleogene and Neogene respectively. Both the regional and local cap rocks are well developed in the basin. Therefore, there occur effective source rock-reservoir-cap rock assemblage for oil and gas accumulation. In addition, under the control of tectonic deformation and depositional environment, three types of traps are available in the basin, i.e. the structural, structural-stratigraphic and stratigraphic traps. The distribution of oil and gas in the basin is finally dependant on the tectonic activities in early Quaternary. Torsional faults may destroy existing traps, and create a path for the hydrocarbon migration to the overlying reservoir rocks in Neogene. Of cause, it will cause heavy loss of hydrocarbon gas.