Hydrocarbon Generation Characteristics And Reservoir Evaluation Of The Lower Paleozoic Shales In Southeast Chongqing

The tectonic evolution of the Lower Paleozoic shales in southeast Chongqing is complex and has the characteristics of strong hydrocarbon generation ability and complex reservoir conditions.In this thesis,taking O₃w-S₁l formation as an example,we systematically analyzed the characteristics of shale distribution by using the outcrops,cores,logging and experimental data.For the collected core samples,detailed geochemical characteristics,reservoir characterization and gas content analysis were performed,by using analyses of organic carbon content,microscopic component experiments,rock flake identification,X-ray diffraction,mercury intrusion,scanning electron microscopy and field desorption analysis.The thickness of shale in O₃w-S₁l formation is 40¹40m,and gradually decreases from northwest to southeast.The buried depth of the formation increases from southeast to northwest.The sedimentary type is mainly bathyal deposit.The content of organic matter in the shale of O₃w-S₁l formation is between 0.86%and4.61%,up to 5.33%,and the maturity is high—over mature.The hydrocarbon generation quantity in the study area was calculated by the volume method,and then the southeastern Chongqing area is divided into four levels of prospective areas of hydrocarbon generation.Brittle mineral content is higher,especially the quartz.Porosity and permeability are low,and nano-pores are developed.The amount of gas generated by the shale is quite different in the study area,showing a trend of high in the northwest and low in the south.Through the analysis of the influence of various parameters on the reservoir,we summed up the four main control factors of reservoir performance as follows:organic carbon content,the degree of thermal evolution,mineral composition and reservoir property.The comprehensive evaluation of reservoir was carried out in this project using not only the main controlling factors of reservoir performance,also the hydrocarbon content and effective thickness of reservoir.