【作者】 张娣；

【导师】 张金功；

【作者基本信息】 西北大学 ， 地球化学， 2005， 硕士

【摘要】 本文以模拟实验和地质分析为主要研究手段,在分析沉降埋藏、抬升剥蚀过程天然气成藏机理的基础上,研究中卫探区及其周围地区在沉降埋藏、抬升剥蚀及剥蚀后再沉降三个过程的天然气成藏地质特征,并对该区进行成藏单元的划分。主要取得了以下认识: 1.中卫探区及其周围地区在不同时期处于不同的构造单元中,在白垩纪末,探区中部形成逆冲推覆带,东部鄂尔多斯盆地则一直处于稳定抬升剥蚀中,西部巴彦浩特盆地和东部银川盆地成为断陷沉降区。 2.中卫探区及其周围地区上古生界同属一套海陆过渡相煤系地层,煤和暗色泥岩是上古生界主要烃源岩,有机质热演化程度较高,以生成天然气为主。上古生界河流—三角洲相砂体构成了天然气的储集层。气藏类型主要以深盆气藏、背斜圈闭及断块圈闭气藏为主。 3.对中卫探区及其周围地区天然气成藏机理的认识: (1) 在沉降埋藏过程中,压实造成的烃源岩孔隙度的大幅度降低阶段仅仅对应于有机质向烃类转化的早期阶段,压实过程水的运移阻力较小、气的运移阻力较大,另外,埋藏过程的增压导致天然气不断压缩、吸附并溶解。因此,沉降埋藏过程不是天然气的大规模运移的过程。 (2) 抬升剥蚀导致烃源岩和储集层的破裂或孔隙的回弹,改善运移通道,造成天然气的膨胀、脱附和出溶,使得天然气大量由烃源岩向储集层的运移。 (3) 在孔隙性砂岩中天然气的运移阻力很大,单靠浮力驱动很难上浮,必须有外加的压差驱动力,在压差驱动下天然气往往在近气源附近的部位聚集,但天然气在断裂、裂缝中容易上浮。 4.中卫探区及其周围地区在抬升剥蚀、逆冲推覆及剥蚀后再沉降过程都有成藏的可能,但它们的成藏特点各不相同。根据成藏特点可将中卫探区及其周围地区成藏区划分为:逆冲推覆构造成藏区、抬升剥蚀成藏区、剥蚀后再沉降成藏区。 (1) 逆冲推覆构造成藏区 逆冲推覆构造成藏区主要分布在中卫探区中部的逆冲推覆带范围,该成藏区的特点是气藏类型以背斜圈闭、断块圈闭气藏为主,其成藏范围有限,但可形成局部的天然气富集区。 (2) 抬升剥蚀成藏区 抬升剥蚀成藏区主要发育在探区东部的鄂尔多斯盆地。该成藏区的特点是烃源岩广布,剥蚀区广布,天然气成藏的范围是大面积,但并不富集,并有可能形成气水倒置现象。 (3) 剥蚀后再沉降成藏区 剥蚀后再沉降成藏区主要发育于探区西部巴彦浩特盆地和探区东部银川盆地内。该成藏区的特点是以背斜圈闭、断块圈闭气藏为主要类型,其成藏范围有限,但有可能富集程度较高。更多还原

【Abstract】 The dissertation researches the geologic characters of accumulation in ZhongWei exploration area and its circumference regions during subsidence, uplift-erosion, erosion-resubsidence and classifies the accumulation unit by simulation test and geology analysis, based on the analysis of gas accumulation mechanism during the process of subsidence and uplift-erosion. The conclusions are as follows:1. The exploration area lies in different structure unit on different stage. In the late Cretaceous period, the center of the exploration area formed overthrusting tectonics, Ordos basin was steadily eroded. Yinchuan basin and Bayanhaote basin became rift-subsidence areas.2. The stratum of Upper Palaeozoic in the exploration area belongs to a same set of sea-land transition facies coal measure strata. The predominant source rocks of Upper Palaeozoic are the coal and the dark shale. The evolvement degree of the origins is much high and the primary products are gas. The fluvial-delta depositional facies sandbodies is good reservoir, primary types of the gas pool are deep basin gas trap, anticlinal trap and fault block trap.3. The conclusions of accumulation mechanism in the exploration area are as follows:(l)Because the stage of the porosity of source rocks descend greatly is consistent with the stage of origins changing into hydrocarbon, the resistance of water is weak, but that of gas is strong in compacting, with the pressure increasing, the hydrocarbon is apt to be compress, the absorbing amount and solubility will increase. So the stage of subsidence may be not the main stage of gas migrating.(2)Erosion can lead to the source rocks and reservoirs breaking and the sand porosity springing , so it can greatly improve the migrating channels. In addition, it can induce the gas to expand, break away, dissolve, which make lots of gas migrate from source rocks to reservoirs.(3)Because the resistance to gas migrating in sand reservoirs is strong , buoyancy can not conquer the resistance to gas migrating. The gas often accumulate near the source when it being drived by pressure difference.4. There are possibility of accumulation during the process of uplift-erosion,overthrusting and erosion-resubsidence in the exploration area. They are different about the characters of accumulation. So petroleum accumulation units can be classified according to the characters: erosion-resubsidence accumulation zone, uplift-erosion accumulation zone, overthrusting tectonics accumulation zone.(1) Overthrusting tectonics accumulation zoneIt mostly distributes in the midland of the exploration area. The characters are following: main types of the gas accumulation are fault block trap and anticlinal trap. The distribution of the gas is limited ,but it can enrich gas in local.(2) Uplift-erosion accumulation zoneIt mostly distributes in Ordos basin. The characters are following:the distribution of source rocks is vast and the erosion zone is also vast. So the distribution area of generating gas is vast, but the gas can not be enriched. At the same time, the phenomena of the downdip gas-bearing reservoirs can possibly be formed.(3) Erosion-resubsidence accumulation zoneIt mostly distributes in Bayanhaote basin and Yinchuan basin . The characters are following: main types of the gas accumulation are fault block trap and anticlinal trap. The distribution of the gas is limited, but it can enrich gas in local.更多还原