Analysis Of Influence Factor Of CO₂ Adsorption On Different Lithofacies Shale

Clarifying the characteristics and influencing factors of CO₂ adsorption on shale is the basis of CO₂ capture and geological storage.In order to study the characteristics and the influencing factors of the adsorption of CO₂ in shale of different sedimentary environment.Study based on the marine shale of the Longmaxi formation in the Southeast of Chongqing,the transition shale of the Shanxi-Taiyuan Formation in the Ordos Basin,and the continental Shale in the Shuinan formation of the Jiaolai basin,as the research object.Through basic experimental tests,the organic geochemical characteristics and mineralogical characteristics of three types of shale are obtained.Characterization of shale pore type,morphological characteristics and connectivity by scanning electron microscopy.Characterizing the macropore characteristics by high pressure mercury intrusion experiments,the mesoporous characteristics were characterized by low temperature N₂ adsorption experiments,characterization of micropore characteristics by low temperature CO₂ adsorption experiments.And combined with three types of experimental results to characterize pore structure parameters of different pore sizes.The CO₂ adsorption characteristics of shale were characterized by CO₂ isothermal adsorption test.Based on the shale organic geochemical characteristics and mineralogical characteristics,the influencing factors and control mechanism of shale adsorption CO₂ were discussed in combination with sedimentary environment.The results show that The type of organic matter in marine shale is type I,and the TOC is more than 2%.It is in the stage of high maturity and evolution,and the dominant mineral composition of brittle minerals.;The organic matter type of the marine-continental transitional shale is type III,and the average TOC content is1.47%;The type of continental shale organic matter is type II,the average content of TOC is 0.90%,and the mineral composition is complex.It is in the stage of high maturity and evolution,and the dominant mineral composition of clay and brittle minerals;micro-and nano-scale organic pore,intergranular pore,and intergranular pore are all developed in the three types of shale.There are four types of pore:intragranular pore and micro-fissure,but the scale and development are different.The CO₂ adsorption isotherm of shale is type I.When the pressure is greater than 7 MPa,the physical properties of shale gradually reach supercritical state,and the adsorption isotherm begins to decrease,then reaches equilibrium.The CO₂ adsorption of shale is affected by environmental factors?temperature,pressure?and organic geochemical characteristics of shale?TOC,R_o?and mineral composition characteristics are jointly controlled;temperature and pressure conditions control the properties of adsorbate and adsorbent carrier,thus affecting CO₂ adsorption;organic geochemistry represents the thermal evolution of organic matter in shale,controls the pore development of organic matter,and then controls CO₂ adsorption;diagenetic evolution controls pore development characteristics in various shale minerals,and then shadows.Sound shale's ability to absorb CO₂;There are differences in main influencing factors and functions among different types of shale.TOC is the main factor affecting CO₂adsorption in marine shale.The development of clay minerals in marine-terrestrial transitional phase promotes CO₂ adsorption.Multiple regression analysis shows that different types of organic matter exist in three types of samples.The correlation between CO₂ adsorption capacity of shale and organic geochemical and mineralogical characteristics of shale is obvious,and the influence is different.