The Logging Evaluation Of Shale Gas And Its Application

Shale gas exploration has been hugely succeeded in the United States,while China shale gas studies are still in its initial stage.As an unconventional resource,the potential of shale gas is gradually recognized by the State agencies and the oil companies.However,how to reasonable indentify shale gas and assess shale gas content or resource potential,are still big problems.Primarily based on the basic principles of different loggings,as well as combined with experimental testing,this thesis studied the shale gas evaluation through well logging technologies.Shale gas mainly exists in dark shales or carbonaceous shales in adsorbed and free gas.Free gas exists in the pores or cracks,and adsorbed gas mainly exists in organic matter or clay surface.Through our study,we proposed "four steps" for evaluation of the content of free gas:(1) Identify lithology with spontaneous potential and natural gamma logging;(2) measure porosity using data of sonic logging; (3) the gas saturation acquired by Archie equation;(4) to determinate the free gas by real gas equation of state content.Adsorption gas obtained from three-steps:(1) Combining resistivity and sonic logging to established the shale organic carbon content of logging recognition model;(2) using the logging model to calculate organic carbon content;(3) determine the relationship between organic carbon content and the adsorption of gas via isothermal adsorption experiments.According to the shale gas calculation models,we can obtain the total gas content,and so realize the rapid evaluation of shale gas by using log data.The thesis respectively applies to the eastern continental sag of Liaohe Depression and the marine shale of Sichuan Basin.The "four steps" and "three steps" have been used to study the above two areas for the free gas and adsorbed gas content.The eastern sag of Liaohe depression,Well Ci3,Tie2,and Huang45 taken as examples,are divided into 8 types of sedimentary facies,and to calculate the free gas and adsorbed gas content based on these sedimentary facies.The results show that the southern section of depression is better than the northern section.In Sichuan Basin,logging evaluation technique has been used to study the shallow basin facies of Longmaxi and bathyal to deep basin facies of Niutitang group.The results show that the free gas content of the Lower Silurian Longmaxi is better than the Lower Cambrian Niutitang group, adsorbed gas content of the Lower Cambrian Niutitang group better than the Lower Silurian Longmaxi.