川中地区震旦系沥青的成因及来源

发布时间：2018-05-14 19:16

本文选题：四川盆地 + 震旦系　；参考：《中国石油大学(北京)》2016年博士论文

【摘要】：四川盆地及其周缘地区震旦系中普遍富集沥青。众所周知,沥青是石油与天然气之间的中间产物,它记录了石油生成后所经历的各种地质和地球化学过程,沥青中所蕴含的地质信息将有助于理解震旦系的油气成藏过程,并对四川盆地的油气勘探和资源预测起到重要作用。本文以川中地区震旦系沥青作为研究对象,通过光学显微镜和扫描电镜观察,对沥青的赋存特征进行分析发现,川中地区震旦系发育有两类沥青,一类是原沥青,即烃源岩有机质原地热演化而形成的沥青;另一类是固体沥青,根据赋存位置和运移距离可将其细分为烃源岩固体沥青和储层固体沥青。震旦系原沥青和烃源岩固体沥青主要赋存于灯三段黑色泥质白云岩中,表明泥质白云岩具备生烃能力并发生过生烃过程;而震旦系储层固体沥青大量分布于灯影组白云岩中,表明在地质历史时期存在大规模油气充注过程。震旦系储层固体沥青具有较高的随机反射率(平均值约为3.4%)和双反射率(4.2%~6.9%),呈现出强烈的光学各向异性,并发育有各种各样的焦炭结构,包括细粒、中粒、粗粒镶嵌焦炭结构以及似流动状-片状焦炭结构。储层固体沥青的焦炭结构类型由其前体性质决定,具有细粒-粗粒镶嵌焦炭结构的储层固体沥青可能来源于富沥青质的重油前体,而具有似流动状-片状焦炭结构的储层固体沥青来源于脱沥青质的重油前体。这些重油前体和储层固体沥青的形成主要受控于热蚀变作用,包括正常的热成熟作用和异常的热液蚀变作用。自生高岭石对沥青质的吸附促进了储层固体沥青的沉淀,因此自然脱沥青质作用也是震旦系储层固体沥青的一种形成机制;另外,震旦系储层固体沥青未发生明显的生物降解作用。通过对川中和威远地区震旦-寒武系储层固体沥青的稀土元素组成进行研究发现,尽管震旦-寒武系储层固体沥青的稀土元素总量(∑REE)十分低(0.20μg/g~2.36μg/g),但是稀土元素及其参数可以将不同地理位置、不同层位和不同赋存单元中的储层固体沥青区分开来。因此,稀土元素可以用于固体沥青分类研究。稀土元素数据的因子分析和主成份分析表明,稀土元素浓度在固体沥青分类中起主要作用,而轻重稀土元素分馏程度(如LREE/HREE和La_N/Yb_N比率)在固体沥青分类中起次要作用。储层固体沥青的稀土元素浓度和配分模式主要受两个地质过程的控制,包括烃源岩继承作用和水-岩作用。储层固体沥青的∑REE值与δ~(13)C值存在完美的二次函数关系表明,控制储层固体沥青稀土元素浓度的主要因素是烃源岩有机质类型。川中和威远地区震旦-寒武系储层固体沥青均具有较低的∑REE值与δ~(13)C值,这与前人报道的来源于下寒武统页岩的储层固体沥青具有很好的对比性,表明川中和威远地区震旦-寒武系储层固体沥青也可能来源于下寒武统页岩。另一方面,水-岩作用导致了储层固体沥青气孔中形成一些自生矿物,如伊利石和重晶石等。这些自生矿物在储层固体沥青中所占比重通常较小,它们对储层固体沥青稀土元素组成的影响较弱。但是,这些自生矿物对缝合线储层固体沥青的稀土元素组成影响较大。通过对川中地区震旦-寒武系进行岩心观察发现,潜在烃源岩包括下寒武统筇竹寺组页岩、筇竹寺组Ni-Mo多金属矿层、灯三段泥质白云岩以及灯影组的藻白云岩和白云岩。岩石学和地球化学研究表明,这些潜在烃源岩的有机质类型均为I-II型,热演化程度较高。灯影组藻白云岩和白云岩沉积于氧化条件下,有机质丰度低,属于差-非烃源岩;灯三段黑色泥质白云岩仅下部富含有机质,主要沉积于亚氧化环境中,为一般-好烃源岩,其上部贫乏有机质,沉积于氧化环境中,为差烃源岩;筇竹寺组多金属矿层沉积于硫化环境中,有机质丰度最高,属于最好的烃源岩,但沉积厚度薄制约了其生烃潜力;筇竹寺组黑色页岩有机质丰度高,沉积于持续的缺氧条件下,且广泛分布于四川盆地及其周缘地区,为研究区内最现实的、最有潜力的好烃源岩。通过碳同位素和微量元素比率(如V/Ni)方法进行沥青-源岩对比表明,川中地区震旦系-寒武系储层固体沥青与威远地区震旦系储层固体沥青具有共同的来源,均来源于下寒武统筇竹寺组缺氧黑色页岩。尽管灯三段泥质白云岩和筇竹寺组多金属矿层具有一定的生烃潜力,但它们对震旦系烃类的贡献可能不大。
[Abstract]:Asphalt is generally enriched in the Sinian system in the Sichuan basin and its periphery. It is well known that asphalt is a intermediate product between petroleum and natural gas. It records various geological and geochemical processes experienced after the formation of petroleum. The geological information contained in the asphalt will help to understand the oil and gas accumulation process of the Sinian system and to the Sichuan basin. Oil and gas exploration and resource prediction play an important role. In this paper, the Sinian bitumen in the central Sichuan area is taken as the research object. Through the observation of optical and scanning electron microscopy, it is found that there are two kinds of bitumen in the Sinian system in the Middle Sichuan area, one is the original bituminous, that is, the original geothermal evolution of the organic matter of the source rocks. The other type is solid bitumen, which can be subdivided into source rock solid bitumen and reservoir solid bitumen according to the location and migration distance. Sinian primary bitumen and hydrocarbon source rock solid bitumen are mainly deposited in three black dolomite dolomites of lamp, indicating that muddy dolomite has hydrocarbon generating capacity and hydrocarbon generation process; Sinian reservoir The solid bitumen is widely distributed in the dolomite of the Dengying group. It shows that there is a large-scale oil and gas filling process in the geological history. The Sinian solid bitumen has a high random reflectance (about 3.4%) and double reflectivity (4.2%~6.9%), showing a strong optical anisotropy and a variety of coke structures, including a variety of coke structures. Fine particles, medium particles, and coarse grains are inlaid with coke structure and like flake like Coke structure. The structure of the coke structure of the reservoir solid bitumen is determined by its precursors. The solid bitumen with fine grain and coarse grain inlaid coke structure may come from the heavy oil precursor of the rich asphaltene, and the reservoir solid Lek with a flow like flake like Coke structure is found. The formation of these heavy oil precursors and reservoir solid bitumen is mainly controlled by thermal alteration, including normal thermal ripening and abnormal hydrothermal alteration. The adsorption of asphaltenes to asphaltenes by authigenic kaolinite promotes the precipitation of reservoir solid bitumen. Therefore, natural deasphalting is also a Sinian system. In addition, the solid bitumen of Sinian reservoir has no obvious biodegradation. Through the study of the rare earth element composition of Sinian Cambrian solid bitumen in Weiyuan and Weiyuan area, the total amount of rare earth elements (sigma) of Sinian Cambrian reservoir solid bitumen (0.20) is very low (0.20 The rare earth elements and their parameters can be distinguished from the solid bitumen in different locations, different beds and different storage units. Therefore, the rare earth elements can be used in the study of the classification of solid bitumen. The factor analysis and principal component analysis of the rare earth element data show that the concentration of rare earth elements is classified in the classification of solid bitumen. It plays a major role, and the degree of fractionation of heavy and heavy rare earth elements (such as the ratio of LREE/HREE and La_N/Yb_N) plays a secondary role in the classification of solid bitumen. The concentration and distribution pattern of the rare earth elements of the reservoir solid bitumen are mainly controlled by two geological processes, including the inheritance of source rocks and water rock. The sigma REE value and delta ~ (13) of the solid bitumen of the reservoir. The perfect two function relation of the C value indicates that the main factor of controlling the concentration of the rare earth element in the reservoir is the organic matter in the source rock. The solid bitumen of the Sinian Cambrian reservoir in the Sichuan and Weiyuan regions has a lower value of sigma REE and the value of delta ~ (13) C, which is from the predecessors' reports from the reservoir solid bitumen of the lower Cambrian shale. It is clear that the Sinian Cambrian reservoir solid bitumen in the Sichuan and Weiyuan areas may also be derived from the lower Cambrian shale. On the other hand, the water rock action leads to the formation of some authigenic minerals, such as illite and barite, in the pores of the reservoir solid bitumen, such as the illite and the barite. They have little influence on the composition of the rare-earth elements of the reservoir solid bitumen. However, these authigenic minerals have great influence on the composition of the rare-earth elements of the Sinian solid bitumen in the seam line. The potential source rocks include the lower Cambrian bamboo shales and the Ni-Mo polymetallic ore of the bamboo Temple formation. The lithology and geochemical studies show that the organic matter of these potential source rocks is I-II type and has a high degree of thermal evolution. Under the condition of the deposition of the dolomite and dolomite in the oxidizing condition, the organic matter is low in the abundance of organic matter, and the three section of the lamp is black. The lower part of the argillaceous dolomite is rich in organic matter, mainly deposited in the oxidizing environment, which is a general good hydrocarbon source rock, and its upper part is poor in organic matter and is deposited in the oxidizing environment, which is a differential source rock, and the polymetallic ore deposits in the bamboo Temple formation are deposited in the vulcanized environment, with the highest organic abundance and the best hydrocarbon source rocks, but the thinness of the sedimentary thickness restricts its hydrocarbon generation. The black shale has high abundance of organic matter, deposited in the continuous anoxic condition and widely distributed in the Sichuan basin and its periphery. It is the most realistic and most potential good source rock in the study area. The comparison of carbon isotopes and trace elements (such as V/Ni) shows that the Sinian system of the Sinian region in the Middle Sichuan area was compared. The solid bitumen of Cambrian reservoir has a common source with Sinian solid bitumen in Weiyuan area, all of which are derived from the anoxic black shale of the lower Cambrian bamboo Temple formation. Although the three segment of the muddy dolomite and the polymetallic ore layer of the bamboo Temple group have certain hydrocarbon generating potential, they may not contribute much to the hydrocarbon of the Sinian system.

【学位授予单位】：中国石油大学(北京)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P618.13

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