藏北羌塘盆地双湖地区中侏罗统布曲组白云岩储层特征研究

发布时间：2018-09-05 13:07

【摘要】：羌塘盆地位于青藏高原北部无人区,是我国油气勘探的重点区块,它是青藏高原海陆相盆地中含油气前景最为广阔的盆地。目前羌塘盆地所发现具有勘探意义的油气显示几乎都赋存于盆地内中侏罗统布曲组晶粒白云岩之中。针对白云岩的物性和岩石成因的研究对于羌塘盆地油气藏勘探与开发具有十分重要的意义。因此,论文通过野外地质调查以及白云岩显微结构观察、阴极发光、荧光发光对研究区白云石的特征进行研究,并结合白云石结构特征以及碳氧同位素、流体包裹体温度以及盐度的分析对白云岩成因进行了研究。研究区侏罗系主要发育台地相与深海-陆棚相两种沉积体系,中侏罗统布曲组白云岩主要发育北部的台地体系中。白云岩的可以归纳出4类垂向序列分别对应4种沉积序列,沉积序列分别为:海进型序列、海进—海退型序列、海退—海进型序列以及海退型序列。研究区白云岩按晶粒大小可以划分5类,为粉晶白云岩、细晶白云岩、中晶白云岩、粗晶白云岩以及不等晶白云岩,按白云岩晶体结构形态,又划分为粉-细晶直面白云石、细晶直面白云石、细-粗晶曲面它形白云石、粗晶曲面鞍形白云石、粗晶曲面鞍形白云石胶结物等。阴极发光与荧光显微镜观察发现这些白云石存在环带或环边结构,推测研究区白云岩为多种成因的白云石构成。白云石的微观结构反映部分白云岩具有准同生白云岩与浅埋藏白云岩的特征,白云岩全岩碳、氧同位素特征具有埋藏白云岩与热液白云岩的相同或相似的组成特征,包裹体测温及盐度数据结合羌塘盆地的埋藏史认为研究区白云石主要为埋藏-热液成因的白云石。因此推测白云岩经历了三期白云石化作用,分别为准同生白云石化、埋藏白云石化以及热液白云石化。白云岩储集层的孔隙类型可以分为晶间孔、晶间溶孔、晶内孔、溶蚀洞、晶间缝以及裂隙等6类,主要储集空间为原生粒间孔和粒间溶孔,总体上为中等-较好的储层类型,优质储集层的孔隙以粗大晶粒的白云岩为主。白云岩储集层的发育受沉积相以及成岩作用的控制,同生期、表生期以及埋藏期的岩溶作用对储集层物性有较好的建设性作用,而压实作用、压溶作用、胶结作用以及重结晶作用则对储集层物性起着破坏作用,而热液作用则具有两面性,只有当热液溶蚀作用产生的孔隙未被充填时,才可能形成优质的储层。
[Abstract]:Qiangtang Basin is located in no man's land in the northern part of Qinghai-Xizang Plateau and is a key oil and gas exploration area in China. It is the most promising basin in the marine and continental facies basins of the Qinghai-Xizang Plateau. At present, almost all of the exploration oil and gas in Qiangtang basin occur in the grain dolomite of the Buqu formation of the Middle Jurassic in the basin. The study of physical properties and petrogenesis of dolomite is of great significance for exploration and development of oil and gas reservoirs in Qiangtang Basin. Therefore, the characteristics of dolomite in the study area were studied by field geological investigation and microstructural observation of dolomite, cathodoluminescence and fluorescence luminescence, and combined with the structural characteristics of dolomite and carbon and oxygen isotopes. The origin of dolomite was studied by analyzing the temperature and salinity of fluid inclusions. The Jurassic mainly developed platform facies and deep-sea shelf facies, and the dolomite of the Buqu formation of the Middle Jurassic mainly developed in the northern platform system. The vertical sequences of dolomite can be concluded to correspond to four kinds of sedimentary sequences respectively. The sedimentary sequences are as follows: the transgressive type sequence, the marine-regressive type sequence, the regressive type sequence and the regressive type sequence. In the study area, dolomite can be divided into 5 types according to grain size, which are powdery dolomite, fine-grained dolomite, mesocrystalline dolomite, coarse dolomite and heterocrystalline dolomite, which can be divided into silt-fine-grained perpendicular dolomite according to the crystal structure of dolomite. Fine-grained straight-faced dolomite, fine-coarse-grained surface-shaped dolomite, coarse-grained surface-saddle-shaped dolomite cement, etc. Cathodoluminescence and fluorescence microscopy show that these dolomite have ring zone or ring edge structure. It is inferred that dolomite is composed of dolomite of various origin in the study area. The microstructure of dolomite shows that some dolomite have the characteristics of quasi-syngenic dolomite and shallow buried dolomite, and the carbon and oxygen isotopic characteristics of dolomite have the same or similar composition characteristics as buried dolomite and hydrothermal dolomite. According to the temperature and salinity data of inclusions and the burial history of Qiangtang basin, the dolomite in the study area is mainly composed of burial and hydrothermal origin dolomite. Therefore, it is inferred that dolomite underwent three stages of dolomitization, which were quasi-syngeneic dolomitization, buried dolomitization and hydrothermal dolomitization. The pore types of dolomite reservoir can be divided into 6 types: intergranular pore, intergranular dissolved pore, intergranular pore, solution cavity, intergranular fracture and fissure, etc. The main reservoir space is primary intergranular pore and intergranular dissolved pore, which is generally of medium to better reservoir type. The porosity of high quality reservoir is dominated by coarse grain dolomite. The development of dolomite reservoir is controlled by sedimentary facies and diagenesis. The karstification of syngenic, epigenetic and burial periods has a good constructive effect on the physical properties of reservoir, while compaction and pressure-solubilization. The cementation and recrystallization destroy the physical properties of the reservoir, but the hydrothermal process has two sides. Only when the pores produced by hydrothermal dissolution are not filled, can the high-quality reservoir be formed.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.13

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