The composition and sedimentary controlling effect of the coal measure gas-bearing(CMG)system of the Jurassic Xishanyao Formation in the southern margin of the Junggar Basin(SJB)are analysed based on core observations...The composition and sedimentary controlling effect of the coal measure gas-bearing(CMG)system of the Jurassic Xishanyao Formation in the southern margin of the Junggar Basin(SJB)are analysed based on core observations,sample tests,and logging data.The results show that the lithological associations of the SJB can be classified into 6 types based on sediment supply strengths and sealing abilities,while the gas shows of CMG reservoirs vary greatly among different lithological associations.Due to the diversified coal-forming environment and multistage coal accumulation,superimposed CMG systems are generally developed in the SJB,and their types include:superimposed unattached CMG systems,multilayer unified CMG systems,and superimposed mixed CMG systems.Furthermore,sedimentary controls on the vertical and regional distributions of different types of CMG systems are discussed according to the sedimentary facies of single wells and well cross-sections and the corresponding data of well log,gas logging,and gas contents.Shore shallow lake environments in the Fukang,Miquan,and northern Liuhuanggou areas were favourable for forming superimposed unattached CMG systems.Braided river environments in the Houxia and the southern Liuhuanggou areas usually formed multilayer unified CMG systems.Braided river delta environments in the Manasi,Hutubi,and eastern Sikeshu areas generally developed multilayer unified CMG systems and superimposed mixed CMG systems.For different types of superimposed CMG systems,the number of gas-bearing units,coal seam gas content,vertical hydraulic connectivity and lateral continuity vary considerably,which makes it necessary to tailor the CMG co-production plan to the type of CMG system.展开更多
An improved evaluation method for estimating gas content during the inversion process of deep-burial coal was established based on the on-site natural desorption curves.The accuracy of the US Bureau of Mines(USBM),Pol...An improved evaluation method for estimating gas content during the inversion process of deep-burial coal was established based on the on-site natural desorption curves.The accuracy of the US Bureau of Mines(USBM),Polynomial fitting,Amoco,and the improved evaluation methods in the predicting of lost gas volume in deep seams in the Mabidong Block of the Qinshui Basin were then compared.Furthermore,the calculation errors of these different methods in simulating lost gas content based on coring time were compared.A newly established nonlinear equation was developed to estimate the minimum error value,by controlling the lost time within 16 min,the related errors can be reduced.The improved evaluation was shown to accurately and rapidly predict the gas content in deep seams.The results show that the deep coal bed methane accumulation is influenced by various factors,including geological structure,hydrodynamic conditions,roof lithology,and coalification.Reverse faults and weak groundwater runoff can hinder the escape of methane,and these factors should be considered in the future exploration and development of coalbed methane.展开更多
Unconventional natural gas in deep coal measures has become an exploration and research hotspot in recent years.The exploration breakthrough of deep coalbed methane and tight sandstone gas in Daning-Jixian Block in th...Unconventional natural gas in deep coal measures has become an exploration and research hotspot in recent years.The exploration breakthrough of deep coalbed methane and tight sandstone gas in Daning-Jixian Block in the eastern Ordos Basin has revealed huge resource potential and commercial prospects in the deep Upper Paleozoic Carboniferous-Permian coal measures.However,the ambiguity of gas accumulation in deep coal measures has restricted exploration and development.Based on a series of tests for fluid inclusions,including petrographic observation,Raman spectroscopy analysis,and microthermometry,combined with the burial-thermal evolution history recovered from basin modeling,this study aims to clarify the timing of gas accumulation in deep coal measures.The results show four types of secondary fluid inclusions in the deep coal measure sandstone layers of Daning-Jixian Block,including CH4-rich inclusions,C2+hydrocarbons-bearing inclusions,CO_(2)-bearing inclusions,and aqueous inclusions.The main formation stage of fluid inclusions corresponded to the mesodiagenesis stage of the deep coal measure sandstone,and the coeval assemblages of fluid inclusions vary due to the recording of gas charging in different maturity stages of coal measure source rocks.This study suggests that tight sandstone gas accumulation in deep coal measures was a continuous charging process with one period-multiple episodes in Daning-Jixian Block,and occurred mainly during the Early Cretaceous(137−127 Ma BP).The results of this study contribute to further understanding of gas accumulation mechanisms in deep coal measures.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.41772132,41502157,41530314)the key project of the National Science&Technology(No.2016ZX05043-001)+1 种基金the Fundamental Research Funds for the Central Universities(No.2652019095)the China Postdoctoral Science Foundation(No.2021M692998)。
文摘The composition and sedimentary controlling effect of the coal measure gas-bearing(CMG)system of the Jurassic Xishanyao Formation in the southern margin of the Junggar Basin(SJB)are analysed based on core observations,sample tests,and logging data.The results show that the lithological associations of the SJB can be classified into 6 types based on sediment supply strengths and sealing abilities,while the gas shows of CMG reservoirs vary greatly among different lithological associations.Due to the diversified coal-forming environment and multistage coal accumulation,superimposed CMG systems are generally developed in the SJB,and their types include:superimposed unattached CMG systems,multilayer unified CMG systems,and superimposed mixed CMG systems.Furthermore,sedimentary controls on the vertical and regional distributions of different types of CMG systems are discussed according to the sedimentary facies of single wells and well cross-sections and the corresponding data of well log,gas logging,and gas contents.Shore shallow lake environments in the Fukang,Miquan,and northern Liuhuanggou areas were favourable for forming superimposed unattached CMG systems.Braided river environments in the Houxia and the southern Liuhuanggou areas usually formed multilayer unified CMG systems.Braided river delta environments in the Manasi,Hutubi,and eastern Sikeshu areas generally developed multilayer unified CMG systems and superimposed mixed CMG systems.For different types of superimposed CMG systems,the number of gas-bearing units,coal seam gas content,vertical hydraulic connectivity and lateral continuity vary considerably,which makes it necessary to tailor the CMG co-production plan to the type of CMG system.
基金supported by the National Natural Science Foundation of China(Grant No.42130802)PetroChina Company Limited“14th Five Year Plan”Science and Technology Major Project(No.2021DJ2301).
文摘An improved evaluation method for estimating gas content during the inversion process of deep-burial coal was established based on the on-site natural desorption curves.The accuracy of the US Bureau of Mines(USBM),Polynomial fitting,Amoco,and the improved evaluation methods in the predicting of lost gas volume in deep seams in the Mabidong Block of the Qinshui Basin were then compared.Furthermore,the calculation errors of these different methods in simulating lost gas content based on coring time were compared.A newly established nonlinear equation was developed to estimate the minimum error value,by controlling the lost time within 16 min,the related errors can be reduced.The improved evaluation was shown to accurately and rapidly predict the gas content in deep seams.The results show that the deep coal bed methane accumulation is influenced by various factors,including geological structure,hydrodynamic conditions,roof lithology,and coalification.Reverse faults and weak groundwater runoff can hinder the escape of methane,and these factors should be considered in the future exploration and development of coalbed methane.
基金supported by the National Natural Science Foundation of China(Grant Nos.42130802 and 42072198)the Fundamental Research Funds for the Central Universities(No.265QZ2021011)+1 种基金PetroChina Company Limited“14th Five Year Plan”Science and Technology Major Project(No.2021DJ2301)PetroChina Company Limited Science and Technology Project(No.2023-KJ-18).
文摘Unconventional natural gas in deep coal measures has become an exploration and research hotspot in recent years.The exploration breakthrough of deep coalbed methane and tight sandstone gas in Daning-Jixian Block in the eastern Ordos Basin has revealed huge resource potential and commercial prospects in the deep Upper Paleozoic Carboniferous-Permian coal measures.However,the ambiguity of gas accumulation in deep coal measures has restricted exploration and development.Based on a series of tests for fluid inclusions,including petrographic observation,Raman spectroscopy analysis,and microthermometry,combined with the burial-thermal evolution history recovered from basin modeling,this study aims to clarify the timing of gas accumulation in deep coal measures.The results show four types of secondary fluid inclusions in the deep coal measure sandstone layers of Daning-Jixian Block,including CH4-rich inclusions,C2+hydrocarbons-bearing inclusions,CO_(2)-bearing inclusions,and aqueous inclusions.The main formation stage of fluid inclusions corresponded to the mesodiagenesis stage of the deep coal measure sandstone,and the coeval assemblages of fluid inclusions vary due to the recording of gas charging in different maturity stages of coal measure source rocks.This study suggests that tight sandstone gas accumulation in deep coal measures was a continuous charging process with one period-multiple episodes in Daning-Jixian Block,and occurred mainly during the Early Cretaceous(137−127 Ma BP).The results of this study contribute to further understanding of gas accumulation mechanisms in deep coal measures.
