Sedimentary Characteristics Of The Carboniferous-permian In The Bohai Bay Basin

This thesis takes the Bohai Bay Basin and its periphery as the research area and the Carbonic-Permian as the target layer,through field outcrop survey,core observation and description,logging data,combined with identification of rock slices and cast slices,scanning electron microscopy observation,X-ray diffraction analysis,physical property test,constant trace elements analysis and high pressure mercury test,based on the theory of Sedimentology,Sequence Stratigraphy and Reservoir Geology,to make a systematic study of the Carboniferous-Permian's stratigraphic characteristics,sedimentary characteristics,and favorable sand bodies in the Bohai Bay area.The main development strata in the study area are the Benxi Formation,the Taiyuan Formation,the Shanxi Formation,the lower Shihezi Formation,the upper Shihezi Formation and the Shiqianfeng Formation,the Benxi and Taiyuan Formations mainly develop the coastal barrier sedimentary system,and are mainly dominated by epicontinental sea sediments,the Shanxi Formation develops a shallow-water delta sedimentary system,which belongs to the continental-continental transitional sedimentary system,the lower Shihezi Formation,upper Shihezi Formation and Shiqianfeng Formation developed river-lake sediments.System,seawater completely receded,a set of terrestrial clastic sediments.The field profile measurement of Shabagou,Zibo Boshan,and Shihuang Village of Qinhuangdao,and drilling and logging data of internal depressions in the Huanghua Depression and Jiyang Depression were conducted to summarize the law of plane thickness variation of each formation,sandstone,and limestone.Then come to the conciusion that the initial direction of the transgression of the Benxi and Taiyuan Formations in the Bohai Bay Basin starts from the east to the southwest and the northwest.After the Taiyuan Formation took place in the Beilong Nansheng tectonic movement,it was mainly from southto north,the Shanxi-Ziqianfeng group is mainly supplied by the northern Yinshan orogenic belt.The coarse-grain quartz sandstones of the Shihezi Formation above the reservoir rock types in the study area are the best,followed by the coarse-grain sandstones of the Lower Shihezi Formation,and the distribution planes of the Shangshihe Formation reservoir sandstones are relatively wide.Among them,there are a large number of oil and GRs shows in both the Huanghua Depression and the Jiyang Depression.The pore type of sandstone is dominated by leaching and erosion pores,with an average porosity of 26.3% and an average permeability of60.5mD.The lower Shihezi Formation is well-developed in the entire sandstone area,and the Jiyang Depression is well-expressed.The pore type of sandstone is dominated by dissolved pores,with an average porosity of 12.86% and an average permeability of 22.5mD.By drawing the isopach maps of the sandstone,it is believed that the central and southwestern parts of the Bohai Bay Basin have greater exploration value.