The Characteristics Of Pore Size Evolution And The Quantitative Characterization Of Delayed Hydrocarbon In Hydrocarbon Source Rocks

The global energy development and the great success of the United States in shale oil and gas exploitation,it has shown that shale oil and gas has extremely high commercial value.According to the survey conducted by the National Bureau of Land Resources,the potential of shale gas resources in China is huge,and further exploration and development are needed to ease the current energy shortage in China.Therefore,in recent years,the National Energy Administration of China has raised shale oil and gas development to the country.Energy strategy level.However,the current exploration and development of shale oil and gas in China is still in the primary exploration stage.The most important point in the exploration and development of shale oil and gas is the reservoir space of shale oil and gas reservoirs,the evolution characteristics of pore sizes at different scales,and the retention of retained hydrocarbons.Happening.Based on the current evolving characteristics of shale oil and gas reservoir space apertures and the urgency and importance of the quantitative characterization of retained hydrocarbons for shale oil and gas exploration and development,this paper carried out basic research work under the funding of major research projects of the China Petroleum Exploration and Development Research Institute.This paper focuses on two major issues: 1.The pore size evolution characteristics of source rocks at different scales;2.The quantitative characterization of hydrocarbons retained in different pore sizes in source rocks.Regarding question 1,the author's research idea is: firstly obtain low-matched samples,then ripen them to different mature stages through ripening experiments,and then conduct high-pressure mercury injection experiments on rock samples of different mature stages,N2 adsorption,CO2 adsorption experiments and NMR experiments were performed to obtain the pore structure and pore size distribution evolution characteristics of different maturity through these four experimental methods.At the same time,scanning electron microscopy and EDS spectroscopy were performed on samples of different maturity levels to obtain the evolution and distribution characteristics of organic and inorganic pores and rock minerals.Regarding question 2,the authors first conducted basic geochemistry experiments on samples of different maturity to obtain basic geochemical data.,Then the samples with different maturity were divided into two parts for extraction and no extraction experiments.Then,the extracted and unextracted samples were separately subjected to nuclear magnetic,N₂,CO₂ adsorption experiments.The former extracted samples can obtain the total pore size distribution of the samples.Characteristics,the late unextracted samples can obtain the pore size distribution when oil is contained,and eventually the distribution of hydrocarbons retained in different pore sizes can be obtained.Because the above experimental techniques have certain defects and scope of application,the author of this article comprehensively and innovatively applies the above-mentioned several experimental methods to enhance their strengths and evade their shortcomings to study the evolutionary characteristics of shale pore size,and the author used The comparative study of ripening samples and samples under geological conditions is to make up for the defects of ripening samples that do not conform to the true evolution of the geology.The comparison with the actual geological samples also contributes to the comparison and correction of later geological parameters,so the actual ripened samples and the actual Good combination of geological samples.Finally,the authors of this study found that the shale samples of the Qingshankou Formation in the Songliao Basin are mainly developed with micro-and nano-pores whose porosity is about 5.6%.With the increase of the maturity,the pores are more and more developed,and the pores with smaller pore diameters change.More developed,its pore size is mainly distributed in the range of 2⁵0nm and greater than 1000 nm.The shale development range of the Longmaxi Formation in the Sichuan Basin ranges from 3.9% to 7.53%.With increasing maturity,the porosity increases,with organic pores becoming more and more developed,accounting for an increase in the proportion of mesopores,and organic pores.Mainly developed between 50 and 300 nm,inorganic pores are less affected by the degree of maturity.The evolution of retained hydrocarbons in the Songliao Basin shows that the retention of hydrocarbons in the mesopores tends to decrease with increasing maturity.In the low-mature and mature stages,the amount of retained hydrocarbons is relatively high,about 0.015cm3/g,and it is high.In the mature and overrunning stages,the retained hydrocarbons are basically zero;in the retained hydrocarbons in the micropores,the retention of hydrocarbons in the pores first decreases and then increases as the maturity increases.