【作者】 何江林；

【导师】 王剑；

【作者基本信息】 中国地质科学院 ， 古生物学与地层学， 2010， 硕士

【摘要】 羌塘盆地是在前寒武纪结晶基底和古生界褶皱基底之上发育起来的以中生界海相沉积为主的一个残留盆地,其总体上具有两拗一隆的构造格局(北羌塘拗陷、南羌塘拗陷和中央隆起带)。胜利河地区位于北羌塘拗陷内的一个三级构造带(龙尾湖凹陷)内,该区构造强度较弱、新生代岩浆活动微弱、大型断裂带不发育。近年来在胜利河地区内发现了目前国内最大规模的海相油页岩,本文力争通过对胜利河油页岩的沉积环境及其石油地质意义的研究,丰富我国油页岩的理论研究、促进北羌塘拗陷油气勘探工作的进行。在地球物理资料和对北羌塘拗陷的区域构造和沉积特征的认识的基础上,以1：25万地质图的实测地层厚度为控制点,运用改进谢别德法对数据进行插值,反演出晚侏罗世北羌塘拗陷的沉积中心分布图。在此基础上,结合区域演化背景、胜利河地区的实测剖面和探槽的岩性化石组合和沉积构造等特征,对胜利河油页岩沉积时期的岩相古地理特征做了初步分析。在对油页岩沉积时期岩相古地理演化特征、油页岩中有机质聚集机理认识的基础上,结合胜利河油页岩特性、沉积水体特征等,推测胜利河油页岩有机质聚集机理符合分层水体成矿模式,沉积环境对胜利河油页岩形成的控制作用主要表现为海湾—泻湖、半封闭泻湖和蒸发泻湖三个演化阶段。通过油页岩的GC-MS实验和岩石热解实验等分析发现,胜利河油页岩热演化程度达到低成熟；油页岩的生物降解程度为3-4级；样品中甾类和萜类化合物能较为有效的反映油页岩的相关地质信息；油页岩中有机质的母质来源主要为浮游植物,部分为细菌来源,另外浮游动物、底栖动物和陆缘有机质碎屑可能对油页岩的有机质有少量的贡献；油页岩沉积水体存在一定程度的盐度分层,且具有较高盐度和较强的还原性。孢粉和C、O同位素研究表明,胜利河油页岩形成时期气候温暖潮湿,而油页岩上覆的膏岩沉积时期区域气候炎热干燥。结合胜利河地区的区域构造背景、龙尾湖凹陷区域地层特征、羌资1井中流体包裹体资料和镜质体反射率资料等,运用Ro—Tmax模型回归得出油页岩历史最高古地温时期龙尾湖凹陷的地温梯度为2.559℃/100m,胜利河油页岩的历史最大埋深为3194.4 m,当时门限深度在胜利河油页岩上覆940.8±m。在运用Ro—Tmax模型对地层剥蚀量进行半定量计算的基础上,综合实测剖面地层厚度和盆地演化特征,运用美国Platte River Associates开发的Basinmod软件对龙尾湖凹陷的埋藏史和热史进行了一维变地温梯度模拟。结合埋藏史曲线、胜利河油页岩排烃模拟实验、油页岩中残留烃含量以及膏岩层溶孔中见有沥青的现象,推测胜利河油页岩可能已进入排烃门限。油页岩及其同期形成的烃源岩可能为龙尾湖凹陷内J3S—N21 s(·)含油气系统提供丰富的油气来源,油页岩及其上覆的膏岩层可能为龙尾湖凹陷内J2b—J2x(·)含油气系统提供良好的区域盖层。更多还原

【Abstract】 Qiangtang basin is a residual basin, which developed on the Precambrian crystalline basement and Palaeozoic fold basement. It’s mainly filled by marine strata. In the basin, there are three secondary structure units which are named the Northern Qiangtang depression, the central uplift and the Southern Qiangtang depression. The Shengli River zone is located in the Longweihu sag, which is a tertiary structure unit in Northern Qiangtang depression. The intensive tectonic movements, huge Neozoic-magmatic activities and big fault belt are absent in the sag. In recent year, the largest marine oil shale resource in China has been discovered in the Shengli River zone. The aims of this study are to enrich the theory study of oil shale in China and promote the development of oil and gas exploration in Northern Qiangtang depression, by studying the depositonal conditions and the significance in petroleum geology of Shengli River oil shale.Base on the characteristics of geophysics, regional tectonic setting and sedimentary setting, the depocenter pattern of Northern Qiangtang depression in Late Jurassic can be simulated by using the formation thickness from 1:250000 geologic map as control points and interpolating data by the updated Xie Be D method. On the base of depocenter pattern of Northern Qiangtang depression, we had studied the characteristics of lithofacies paleographic map during the Shengli River oil shale depostional period, by synthesizing the data of regional geologic setting, the section and the trenches of oil shale in Shengli River zone.Base on the study of the lithofacies paleographic map and the enrichment mechanism of organic in sedimentary matter, we conjecture the enrichment mechanism of organic in Shengli River oil shale coincidence with the layering-water-accumulation model, by integrating the characteristics of lithology, sedimentary water body an so on. The control action of depositional conditions are expressed by three steps, which are bay-lagoon, semi-closed lagoon and closed lagoon.The experimental analysis of GC-MS and Rock-Eval indicate that the thermal evolution of Shengli River oil shale had got the low maturity phase. The biodegradation degree of Shengli River oil shale is range rank 3 to rank 4. The steranes and terpanes in the Shengli River oil shale can reflect the geologic information effectively. The organic matters contented in Shengli River oil shale are mainly from phytoplankton, partly from bacterium, a little from bottom fauna and terrestrial plant. The sedimentary water body is salinity stratification. The oil shale sedimentary environments are anoxic and relatively hypersaline. The characteristics of C&O isotope in oil shale section indicate the climate in the Qiangtang basin region during the deposition of oil shales was warm and humid or sub-humid. However, it’s hot and arid during the plaster formation sedimentary period.According to the regional tectonic setting, the distribution characteristics of stratum in Longweihu sag, the characteristics of fluid inclusion under NO.1 prospect hole in Qiangtang basin, the characteristics of Ro in organic matters in stratum an so on, we had got the geothermal gradient value is 2.559℃/100m when the oil shale burial to the largest depth in history, by the regression analysis method base on the Ro—Tmax model. The largest burial depth of Shengli River oil in history was 3194.4 m. The threshold depth in that time is 940.8±m upon the oil shale formation.Base on the semi-quantity study of denudation thickness by Ro—Tmax model, the formation thickness and the basin evaluation characteristics, we had got the characteristics of 1-D burial and thermal history of Longweihu sag, by using the Basinmod software which was developmented by Platte River Associates, USA. According to the burial history, the hydrocarbons expulsion simulating experiment of Shengli River oil shale, we are supposed that the Shengli River oil shale had got the expulsion threshold. Finally, we recognized that the Shengli River oil shale and the formation sediment in the same time may be the source rock in J3s—N21s(·) petroleum system and as cap formation in J2b—J2x(·) petroleum system in Longweihu sag.更多还原