库车坳陷煤成油、气的分布及控制因素

DISTRIBUTION OF COAL-DERIVED OIL AND GAS IN KUQA DEPRESSION AND ITS CONTROL FACTORS

塔里木盆地库车坳陷中生界煤系烃源岩主要以生气为主,该坳陷油气藏类型共有5种:纯干气气藏、湿气气藏、凝析气藏、油气共存的油气藏、纯油藏。烃源岩以镜质组和惰性组为主,贫壳质组,形成气藏还是油藏主要取决于地质因素,而不是由显微组分决定的;干气气藏是因为圈闭形成后捕获了下伏高—过成熟的煤系烃源岩生成的干气而形成的;湿气藏和凝析气藏是因为圈闭捕获了成熟阶段煤系烃源岩生成的湿气或凝析气;油藏主要形成于盖层封闭性稍差地区、有断裂破坏地区,原来的湿气或凝析气藏中天然气大量散失,少量的油得以保存,形成小规模的残余煤成油藏或油气藏。

Mesozoic coal-measure source rocks in Kuqa depression of Tarim basin are gas-prone. Totally 5 types of oil and gas reservoir exist in the depression, namely pure dry gas reservoir, wet gas reservoir, condensate gas reservoir, associated oil and gas reservoir and pure oil reservoir. The source rocks are rich in vitrinite and inertinite, but poor in exinite. The types of reservoirs are mainly determined by geologic factors rather than maceral. Dry gas reservoirs are formed through trapping the dry gas generated by the underlying high-to-over mature coal measure source rocks. Wet gas reservoir and condensate gas reservoir are formed through trapping the wet gas or condensate gas generated by mature coal-measure source rocks. Oil reservoirs are mainly formed in areas with relatively poor sealing ability of cap rocks and/or highly-developed faults. The gas in the original wet gas reservoirs or condensate gas reservoirs has largely escaped while small amount of oil has been preserved, which leads to the formation of small residual coal-derived oil reservoirs or oil and gas reservoirs.