Study On The South Of Erdos Basin Sedimentary Characteristics And Pore Development Of Chang7Mud Shale

This paper has studied chang7mud shale of Yanchang formation of Mesozoic in the southof the Ordos basin, deep and Systematically by a large number of geological data collectionand analysis and take advantage of the outcrop, drilling, logging, core and sliceobservational analysis, a variety of analytical testing methods, such as scanning electronmicroscopy on the characteristics of sedimentary, the distribution of sedimentary facies andthe characteristics of porosity development.Studies have shown that,chang7deposition of Yanchang formation of source material inthe Ordos Basin mainly from the neighboring five directions northeast, southwest, south-westand west of the basin,and the Northeast and Southwest are the two main source direction.Study area mainly developed deep lake-semi-deep lake facies. Chang7deposition of Yanchangformation in the Ordos Basin was the heyday of basin development, which had quiet lake, thewidest range lake,and up to a maximum thickness of dark mudstone120m is a high-qualitysource rocks. Study area constructed basically inherited the whole region of Ordos Basinconstructed: East depth:350~600m, western depth:1170~1750m, the overall performancefor the North West, the tendency of the large flat monoclinic. Chang7formation stratigraphicthickness long range research in the area of78~132m, which was divided into chang71,chang72, chang73three small layers from top to bottom. Thre top of chang71developed athin black shale development or dark muddy siltstone, which performanced high gamma,medium-high resistance, medium-high acoustic in electric measuring curve and Multi-frequency sound waves with jumping phenomenon; chang72mainly developed Mudstone,silty mudstone and siltstone which performanced medium-high gamma, medium-highacoustic and the magnitude more gentle curve; chang73mainly developed a dark black oilshale and silty mudstone shale represented Zhangjiatan shale which performanced highvelocity difference(>300us/m), high gamma (>150API), medium-high resistance,especially in the high box-shaped curve shape of the most prominent difference. Zhangjiatanshale buried in this area more than700m~1900m depth, farther east the more shallow depth,thickness variations ranging in30m~40m. Shale facies with three kinds in the study areawere mainly mud with dark gray shale, gray and black mudstone facies, black shale facies and gray siltstone. Clay minerals illite, chlorite and illite mixed layers. The study areabelonged to peak oil shale source rocks,and the vitrinite reflectance distribution between0.75%-1.13%. Chang7shale mainly development in three main pore types: intergranularporosity within the grain pores, the particles inside the particles and pores between particlesand organic matter by scanning electron microscopy. Hydrocarbon process and type of organicmatter might effect on the generation of porosity.