库车前陆盆地含油气系统的地质特征

THE GEOLOGICAL CHARACTERISTICS OF THE PETROLEUM SYSTEM IN KUCHA FORELAND BASIN

论述了库车含油气系统的地质特征:1具有一个生烃灶,发育有三叠系和侏罗系烃源岩,岩性为湖相泥岩、沼泽相煤系和高碳泥岩,干酪根为 ～ 1型;2具有低温度场、高压力场和强应力场,这种能量场导致了晚期运聚和事件成藏;3成藏组合包括三叠系-侏罗系烃源岩,侏罗系红色泥岩和下第三系-上第三系膏泥岩两套区域盖层和其它局部盖层,和三叠系-上第三系的砾岩、砂岩、粉砂岩和白云岩储层;4圈闭主要为坳陷区中新世以来形成的成排成带的断层相关褶皱和前缘隆起正断层下盘的断块;5由于强烈的构造运动,有早白垩世成油期和中新世末两个成气期,最重要的成藏期为中新世末(1.8Ma前);6有3种成藏模式,油藏、凝析气藏和气藏分布于三叠系-侏罗系的砂岩和砾岩储层、白垩系和下第三系的砂岩和粉砂岩以及白云岩储层。认为形成大油气田的关键因素有区域盖层、有效烃源岩的范围、疏导体系的连通性和圈闭的规模等。

In last two decades, with some oil and gas fields were discovered in Kucha foreland basin, more progress have been made on Kucha petroleum system. In this paper, the main geological characteristics about Kucha petroleum system are showed as follows: The Kucha petroleum system is composed of Triassic-Jurassic source rock which is characterized by Ⅲ-Ⅱ_(1) type kerogen from mudstone of lacustrine facies and coal beds-mudstone bearing high carbon of swamp facieses. Its energy fields are characterized by lower temperature, high pressure and forceful stress fields, and have controlled event reservoir-formation in Neogene's Himalaya tectonic event. The play is composed of Triassic-Jurassic source rock, Tertiary-Neogene, Cretaceous and Jurassic sandstone reservoir rock, and the seal rocks of regional Jurassic red mudstone and Tertiary-Neogene's salty gypseous mudstone. Traps are mainly composed of anticlines formed in fault related folds in the depression and fault-block at the foot wall of normal fault in the frontier uplift. The oil pool formed in the end of early Cretaceous, and gas pool, in the end of Neocene. So three type of petroleum reservoir(oil, condensate and gas pool) distributed in the sandstone and conglomerate of Triassic-Jurassic and the sandstone, siltstone and dolomite of lower Cretaceous, Tertiary and Neocene. The main key point of the reservoir-formation is at the end of Neocene (1.8 Ma). The key elements to form a large gas field is valid combination of those geological elements, such as an active source pad, regional seal rock, carrier system (sandstone, coal beds, faults and fissure), the capacity of traps. And these mainly distributed under the main faults may be form a large one.