【作者】 刘新社；

【导师】 周立发；

【作者基本信息】 西北大学 ， 矿产普查与勘探， 2008， 博士

【摘要】 重点围绕鄂尔多斯盆地东部上古生界岩性气藏成藏地质特征,以成藏地球化学与天然气成藏流体历史分析为手段,以盆地构造演化史—热史、生烃史—沉积/成岩史、天然气聚集史和天然气成藏动力学为主线,详细解剖了致密岩性气藏形成过程及形成机理,分析了岩性气藏形成的主控因素,总结出不同含气组合天然气的富集规律。研究区发育有下部、中部、上部三个不同的含气组合,烷烃气碳同位素特征及气源对比表明,天然气主要来自煤成气,个别井混有少量油型气。气藏中甲烷含量及δ¹³C₁与烃源岩成熟度具有明显相关性,表现为天然气近距离运聚成藏的特征。根据烃源岩的主要排烃时间、流体包裹体、自生伊利石K-Ar同位素及甲烷同位素动力学分馏等方法综合研究认为,下部、中部含气组合气藏形成经历了两期油气充注,晚侏罗世—早白垩世为天然气主要充注期,上部含气组合主要存在早白垩世一期主要充注时间。研究区上古生界地史期普遍发育异常高压,源储剩余压差是天然气运移的主要动力。下部、中部组合源储剩余压差大,天然气充注强度高,含气饱和度高;上部组合远离烃源岩,烃类的充注受气源供给条件控制,天然气充注强度小。上古生界储层总体反映了“先致密、后成藏”的特点。下部含气组合各种成藏要素匹配合理,天然气聚集效率高,多形成大型气田;中部含气组合各种成藏要素匹配较好,聚集效率较高,多形成大-中型气田;上部含气组合成藏要素匹配较差,聚集效率较低,多形成小型气田。盆地东部天然气的富集规律主要受烃源岩生烃强度、气藏成藏期源储剩余压力差、输导体系类型、优质储层分布、盖层厚度和排替压力等因素控制,不同含气组合具有不同油气富集成藏规律,以此作为有利勘探目标优选的依据,并将研究区上古生界优选出4个有利勘探目标区,它们分别是下部组合的神木、余兴庄勘探目标区,中部组合的大佛寺勘探目标区,上部组合的王家砭勘探目标区。更多还原

【Abstract】 Aimed at lithologic gas reservoir of the upper Paleozoic in eastern Ordos Basin, this paper analyzes the course, the mechanism and the main control factors of tight lithologic gas reservoir synthetically. The accumulating regularities of different gas zones are recognized. The research is based on the studies of tectonic evolution, thermal and hydrocarbon generation, sediment and diagenetic evolution, accumulating history, and dynamics of gas accumulation by means of the geochemistry and fluid history analyzing.There are three different gas zones in research area, including lower, middle and upper gas zones. The studies of alkane carbon isotope and gas-source rock correlation indicate that the natural gas originate from coal-derived gas mainly, and in very few areas, a little quantity oil-type gas is mixed in. The obvious relationship between the quantity of methane gas and itsδ¹³C₁ and maturity of the hydrocarbon source rock reveals the reservoir feature of close-migration and accumulation.Through investigation of main hydrocarbon-expulsion epoch, fluid inclusion, K-Ar isotope of authigenic illite and isotope dynamic fractionation of methane, it can be drawn a conclusion that lower and middle gas layers experienced two times injection, and the main gas injection occurred from late Jurassic to early Cretaceous. Whereas, the main filling of upper gas zone only occurred in early Cretaceous.During the deepest buried period, abnormal high pressure was developed at large in upper Paleozoic of eastern Ordos basin, and the overpressure between reservoir and hydrocarbon source rock was the dominating driving-force of gas migration. Powerful filling and high saturation in lower and middle gas zone was resulted from exceed overpressure. Whereas, far distance between reservoir and hydrocarbon source rock restricted the supply of gas in upper gas layers."Compact firstly, hydrocarbon accumulation secondly" characterize the process of the upper Paleozoic reservoir. For lower layers, rational matching of reservoir factors brought on efficient accumulation and formed large-scale gas field. As for the upper gas layers, immoderate framework of reservoir factor resulted in inefficient assembly, and formed small reservoirs. Accordingly, Large-middle scale reservoirs were fashioned in the middle layers usually for it’s accumulation condition lies between the upper and the lower gas layers.The hydrocarbon enrichment in the east of basin was mainly controlled by such geological factors as gas generation intensity of source rock, the overpressure between reservoirs and source rocks at accumulation stage, the type of passage system, the distribution of high quality reservoir, the thickness of cap socks and displacement pressure, etc. The different gas zones are of the different accumulation rule. Based on the study mentioned above, four favorable exploration targets are obtained. Aimed at Lower gas zone, Shenmu and Yuxingzhuang regions are well evaluated. To the middle and upper gas zones, Dafusi and Wangjiabian regions are prospective.更多还原