Study On Control Factors Of Shale Adsorption Capacity And Simulation Of Shale Gas Storage Capacity

In recent years,China makes a breakthrough in shale gas in Chongqing area,and Chongqing Fuling shale gas field of Sinopec becomes the world's first commercial productio n outside of North America,outputting more than 50 billion cubic meters shale gas during 2016.Looking for shale gas resources "Sweet spot" has become one of the key factors in shale gas exploration and development.Storage capacity of shale directly determines the shale gas resources.There are many studies on the store mechanism of shale gas,but there is still a lot of work for the quantitative characterization of shale gas storage capacity.In this paper,the effects of organic matter content,maturity,type,mineral composition and temperature and pressure on the adsorption capacity of shale were studied by systemat ic experiment and collecting adsorption experiment data.On this basis,we established an adsorption model combining the Polanyi potential theory,the results of supercritical adsorption experiment and computer simulation.The relationship between adsorption gas and free gas was analyzed by numerical simulation.Based on the model of adsorbent gas and free gas model,the quantitative characterization model of shale gas storage capacity was established.The results show that the adsorption capacity of shale is mainly related to the adsorbate(humidity,gas component),adsorbent(mineral composition,organic matter)and external temperature and pressure conditions.Shale storage capacity increases with the increase of the maturity and the content of organic matter.The adsorbent directly determines the size of the adsorption space,and temperature and pressure directly determine the density of adsorption phase.The adsorption model produces good fits for the adsorption experiment data,and the correlation coefficient is 98.8%.The numerical simulation shows that the absolute adsorption capacity of shale increases first and then decreases with the increase of burial depth.The maximum adsorption capacity corresponds to a depth of about 1000 m.The higher the geothermal gradient,the more obvious the adsorption capacity decreases with the depth.It shows that during the shal ow portion pressure plays a major role resulting in the adsorbed phase density becoming large and deep portion temperature plays a major role causing adsorbed phase density gradually decreasing.In the primary extraction of shale gas,the gas mainly comes from the free gas,and then adsorption gas contributing more.The free gas is linearly reduced with the decrease of pressure,and the adsorption gas is initially reduced slowly,then the conversion rate was accelerated type "J".The shallow shale gas is mainly composed of adsorbed gas,and deep mainly to free gas-based.