Analysis Of Forming Conditions Of Shale Gas And Formation Preferred Of The Lower Jurassic In Fuling Block

Through the efforts of recent years, the marine shale gas has made significant exploration breakthrough in Sichuan basin, whereas the studies on continental shale gas are relatively few because of its complicated formation conditions. The continental hydrocarbon source rocks in Sichuan basin are mainly the Jurassic Qianfuya Formation, Ziliujing Formation, and the Triassic coal hydrocarbon source rocks. They are characterized by the stable distribution of the shale, high organic matter abundance and large thickness, etc., which shows good shale gas accumulation conditions and great exploration potential. This paper takes ―Analysis of Forming Conditions of Shale Gas and Formation Preferred of the Lower Jurassic in Fuling block‖ as title, using field observation, survey, core observation and mud shale organic geochemical analysis, physical property analysis, X-ray diffraction analysis, specific surface analysis, electron scanning microscopy(sem) etc. to analyze and research on the shale gas enrichment in Ziliujing Formation of the lower Jurassic in Fuling area in detail, and optimizing the shale gas enrichment area and favorable strata for shale gas accumulation of Ziliujing Formation in the lower Jurassic in Fuling district. Then, the exploration and research on the shale gas accumulation conditions of Ziliujing Formation in the lower Jurassic in Fuling area are improved by the the research on the shale gas enrichment.It is ascertained through the research that the favorable micro sedimentary facies in the Lower Jurassic in Fuling area are semi-deep lake storm shoals and semi-deep lake; the lithology of semi-deep lake storm shoals is mainly characterized by interbedded dark gray shale and micrite bioclastic limestone and shelly limestone, and semi-deep lake deposits are characterized by the main black shale and marl, the representatives are Da’anzhai and Dongyuemiao; Da’anzhai Formation is divided into three sub-members i.e. a large period, large-Sec and junior section three sub segments. From the Fuling area continental sedimentary shale gas phase histogram that Fuling big Sec and development Dongyuemiao thick dark organic-rich shale, therefore, Fuling Lower Jurassic artesian well set research priorities for the big Sec and east Yuemiao segment.reviewing the Fuling block under the Jura artesian well group research. Has been clear about the half deep lake beach and half deep lake of mud storm is the favorable sedimentary microfacies of the lower Jurassic in Fuling block. Lithology of sedimentary microfacies are half deep lake storm beach chip in dark grey mud shale and micritic limestone, shell limestone for different thickness interbed characteristics, half deep lake sedimentary microfacies in the mud is characterized by black shale and marl, main representative for Da’anzhai and Dongyuemiao member. Da’anzhai is divided into three sub sections, they are the first sub section, the second sub section and the third sub section. From Fuling area of continental shale gas well sedimentary facies histogram that the Da’anzhai second sub section and Dongyuemiao member of development of thick dark mud shale rich organic matter in Fuling block, and hence lower Jurassic in fuling artesian well group focuses on the Da’anzhai second sub section and Dongyuemiao member.According to the organic chemical analysis data in Fuling area, the average TOC of Da’anzhai second sub section is1.33%, average Ro is 1.27%, in the mature stage, generation of wet gas, kerogen is given priority to with type Ⅱ. The average TOC of Dongyuemiao member is 1.78%., average Ro is 1.64%, in the high mature stage, mainly produce moisture, and kerogen is given priority to with typeⅡ.According to Fuling district property analysis data, reservoir space of the Da’anzhai second sub section and Dongyuemiao member is mainly made up of pore and fracture. Pore types mainly include intergranular pore, intergranular hole and a small amount of organic matter. The micro cracks are mainly type of Fracture type, including hard mineral seam edge. The scale to the micron grade micro pore and micro cracks for the permeability of shale, the gas reservoir and the adsorption plays an important role. Fuling district the Da’anzhai second sub section average brittleness mineral content is 43.75%,and Dongyuemiao member average brittleness mineral content is 43.9%, the characteristic of brittle mineral content is higher, can be pressed. At the same time, Fuling district most continental shale gas distribution area is located in the synclinorium area, has a simple structure, stable, gentle formation, fracture development, structure, good preservation condition. According to the shale gas formation conditions and main controlling factors, the hydrocarbon-generating condition is superior the Da’anzhai second sub section and Dongyuemiao member, the widely distributed in the study area has a high content of organic matter, and Burial is moderate. From the hydrocarbon generation conditions, reservoir conditions, comprehensive analysis of preservation condition selected of Fuling block for shale gas exploration and development in the northeast region. Dongyuemiao member for optimal formation, and the Da’anzhai second sub section relative to the Dongyuemiao member.