鄂尔多斯盆地中部气田奥陶系风化壳天然气成藏分析

根据地质和地球化学资料,并结合前人研究成果,研究了鄂尔多斯盆地古生界烃源岩生气中心及生气高峰,探讨了中部气田天然气的成藏期次、成藏过程和成藏模式.鄂尔多斯盆地中部气田位于烃源岩生气中心及其附近,可以获得充足的气源;天然气成藏主要有2期,即晚三叠世末和早白垩世末;成藏过程包括4个演化阶段:储集层孕育阶段(O1-C1)、圈闭形成阶段(C2-P)、天然气运聚成藏阶段(T3-K1)和气藏调整/定型阶段(K2-Q);奥陶系风化壳天然气成藏存在上古生界天然气穿层运移至奥陶系顶风化壳聚集和下古生界天然气自生自储型2种成藏模式.

Analysis of the natural gas accumulation in the Ordovician weathered crust of the central gasfield in Ordos Basin

On the basis of geological and geochemical data,and combined with previous works,the gas generating center and the main gas generating peak periods of the Paleozoic source rocks in Ordos Basin are studied.The formation periods,process and models of the natural gas reservoir in the central gasfield in Ordos Basin are also discussed.It is shown that the central gasfield is located in the gas generating center of Ordos Basin and near it,and it can be supplied for enough natural gas.The natural gas reservoir formation of the gasfield is mainly in the end of late Triassic epoch and the end of early Cretaceous epoch.The gas pool forming process includes four stages,i.e.the gestation of reservoir (O1-C1),the formation of trap (C2-P),the migration and accumulation of natural gas (T3-K1),the adjustment and determination of gas reservoir (K2-Q).There are two formation models of the natural gas reservoirs in Ordovician weathered crust:the natural gas generated in Upper Plaeozoic source rocks migrating to the weathered crust at the top of Ordovician and then accumulating there;the natural gas generated in Lower Plaeozoic source rocks accumulating here.