Research On The Adsorption Mechanism And Influencing Factors Of Shale Gas Reservoirs

As a hot spot of the global exploration and development of the unconventional gas,shale gas has achieved its commercial development first in the United States in the 21st century,this process has drastically changed the traditional US energy structure.In addition,our potential domestic shale gas resource,with features like large thickness,wide distributions,high gas content and enormous reserves,will undoubtedly induce a significant impact on the energy industry of the future,as well as to greatly ease the problem of non-renewable energy shortage.But,it cannot be ignored that there are several obstacles and difficulties in the shale gas development,such as the unique properties of self-generation and self-storage,the low porosity,low permeability and the adsorption/desorption mechanism which is similar to coalbed methane.Fully understanding the shale-related adsorption properties is rather important to struggle for the commercialization of shale gas development in our country.Therefore,in the thesis,three typical shale gas areas of different sedimentary facies-North American marine shales,domestic marine shales and domestic terrestrial shales are focused.Through massive literature researches,laboratory experiments and adsorption data fitting,their physical and chemical characteristics and adsorption influencing factors are analyzed,several adsorption models are optimizing selected,and the application standards of adsorption model fitting are also established.The major contents of this thesis are as follows:(1)Several experimental methods such as isothermal methane adsorption,nitrogen adsorption,X-ray diffraction,argon-ion polishing,scanning electron microscope(SEM),nuclear magnetic resonance(NMR),mercury intrusion,gas porosity are utilized to obtain the domestic reservoir data.With this information,the similarities and differences of the characteristics of three abovementioned shale gas areas are systematic analyzed.(2)Domestic and foreign adsorption data are compared and analyzed to discover the influencing factors of shale gas adsorption,including temperature,TOC,organic maturity,kerogen type,pore status,humidity,surface area,mineral composition,grain diameter,gas composition,et cetera.On this basis,the main factors are also determined.(3)Exerting the nonlinear data fitting by using subcritical-state adsorption models like Langmuir,Freundlich,T-BET,Toth,Langmuir-Freundlich,Extended-Langmuir and Dubinin-Radushkevich model.The optimum models among them under different conditions are selected and the supercritical-state absorption corrections are also applied.(4)Based on the fitting accuracy data,the fitting degree differences in subcritical-state models,the improvements of data fitting precision in supercritical-state models,the influence of temperature and TOC on both models are all studied.Ultimately,the universalism application standard of adsorption model fitting of all researched areas is established.This thesis has important theoretical significance and practical value on domestic shale gas reservoirs commercial exploitation of China.