Characterizing the microscopic occurrence and distribution of in-situ pore water and oil is crucial for resource estimation and development method selection of shale oil.In this paper,a series of nuclear magnetic reso...Characterizing the microscopic occurrence and distribution of in-situ pore water and oil is crucial for resource estimation and development method selection of shale oil.In this paper,a series of nuclear magnetic resonance(NMR)experiments were conducted on shales from the Gulong Sag,Songliao Basin,China,at AR,WR-AR,WOR-AR,Dry,SO,and WR states.In-situ pore water and oil were reconstructed after WOR-AR.An improved T1-T2pattern for shale oil reservoirs comprising water and oil was proposed to classify and quantitatively detect pore fluids at different occurrence states.The total and free oil contents derived from NMR T1-T2spectra at AR states were found to correlate well with those from multistage Rock-Eval.Moreover,the NMR-calculated total and free oil are generally larger than those measured from multistage Rock-Eval,whereas adsorbed oil is the opposite,which implies that adsorbed,bound,and movable oils in shale pores can be accurately and quantitatively detected via NMR,without absorbed hydrocarbons in kerogen.As per the NMR T2and T1-T2spectra at WOR-AR state,the micro-distributions of in-situ pore water and oil were clearly demonstrated.Adsorbed,bound,and movable oils primarily occur in the micropores(<100 nm),mesopores(100-1000 nm),and macropores(>1000 nm),respectively,whereas capillary-bound water is primarily correlated with micropores.Thus,the microscopic occurrence and distribution of adsorbed oil are remarkably affected by pore water,followed by bound oil,and movable oil is hardly affected.This study would be helpful in further understanding the microscopic occurrence characteristics of pore fluids in-situ shale oil reservoirs.展开更多
The pyrolysis parameter S1,which indicates the amount of free hydrocarbons present in shale,is often underestimated due to hydrocarbon loss during sample handling and measurement processes.To remedy this issue,we stro...The pyrolysis parameter S1,which indicates the amount of free hydrocarbons present in shale,is often underestimated due to hydrocarbon loss during sample handling and measurement processes.To remedy this issue,we strongly recommend an immediate three-step hydrocarbon thermal desorption(HTD)approach to be conducted on oil shale at the drilling site.This approach measures S_(g),S_(O),and S_(1)^(*),which refer to gaseous,light,and free hydrocarbons,respectively.The new shale oil content value,calculated from the total of these three parameters,is far more precise and reliable than traditional pyrolysis S1.Moreover,we thoroughly investigated the components and microscopic occurrence features of hydrocarbons thermally desorbed at three temperature stages using gas chromatography(GC)and X-ray microcomputed tomography(CT).For example,we selected Chang 7_(3)mud shale.Our experimental results irrefutably indicate that the ultimate shale oil content of poor resource rocks is significantly impacted by evaporative loss,with this effect being greater when the total organic carbon(TOC)is lower.Additionally,C_(1-5)and C_(1-7)hydrocarbons constitute almost all of S_(g)and S_(O),respectively.S_(g)and S_(O)are predominantly composed of C_(1-3)gaseous hydrocarbons,with a maximum proportion of 42.93%.In contrast,S_(1)^(*)contains a substantial amount of C_(16-31)hydrocarbons.A three-dimensional reconstruction model of an X-ray micro-CT scan shows that while the amount of shale organic matter greatly decreases from the frozen state to 300℃,the pore volume significantly increases,particularly between 90 and 300℃.The increased pore volume is mainly due to macropores and fractures.It is imperative to note that the shale oil triple-division boundaries must be adjusted based on more accurate oil content,although this would not affect the resource zones to which the samples already belong(ineffective,low-efficient,and enriched resources).In conclusion,we strongly advise conducting an immediate well-site analysis or utilizing preservation procedures,such as deep freezing or plastic film wrapping followed by core waxing,to minimize volatile loss.展开更多
基金financially supported by the National Natural Science Foundation of China(42302160,42302170,42302183,and 42072174)the Sanya City Science and Technology Innovation Project(2022KJCX51)the Support Plan for Outstanding Youth Innovation Team in Shandong Higher Education Institutions(2022KJ060)。
文摘Characterizing the microscopic occurrence and distribution of in-situ pore water and oil is crucial for resource estimation and development method selection of shale oil.In this paper,a series of nuclear magnetic resonance(NMR)experiments were conducted on shales from the Gulong Sag,Songliao Basin,China,at AR,WR-AR,WOR-AR,Dry,SO,and WR states.In-situ pore water and oil were reconstructed after WOR-AR.An improved T1-T2pattern for shale oil reservoirs comprising water and oil was proposed to classify and quantitatively detect pore fluids at different occurrence states.The total and free oil contents derived from NMR T1-T2spectra at AR states were found to correlate well with those from multistage Rock-Eval.Moreover,the NMR-calculated total and free oil are generally larger than those measured from multistage Rock-Eval,whereas adsorbed oil is the opposite,which implies that adsorbed,bound,and movable oils in shale pores can be accurately and quantitatively detected via NMR,without absorbed hydrocarbons in kerogen.As per the NMR T2and T1-T2spectra at WOR-AR state,the micro-distributions of in-situ pore water and oil were clearly demonstrated.Adsorbed,bound,and movable oils primarily occur in the micropores(<100 nm),mesopores(100-1000 nm),and macropores(>1000 nm),respectively,whereas capillary-bound water is primarily correlated with micropores.Thus,the microscopic occurrence and distribution of adsorbed oil are remarkably affected by pore water,followed by bound oil,and movable oil is hardly affected.This study would be helpful in further understanding the microscopic occurrence characteristics of pore fluids in-situ shale oil reservoirs.
基金This study is financially supported by the National Natural Science Foundation of China(Grant Number 41972122,42172139 and 42072186)the China Scholarship Council(CSC),the Open Foundation of Cooperative Innovation Center of Uncon-ventional Oil and Gas,Yangtze University(Ministry of Education&Hubei Province)(Grant Number UOGBX 2022-03)Petro-China Innovation Found(No.2020D-5007-0101)。
文摘The pyrolysis parameter S1,which indicates the amount of free hydrocarbons present in shale,is often underestimated due to hydrocarbon loss during sample handling and measurement processes.To remedy this issue,we strongly recommend an immediate three-step hydrocarbon thermal desorption(HTD)approach to be conducted on oil shale at the drilling site.This approach measures S_(g),S_(O),and S_(1)^(*),which refer to gaseous,light,and free hydrocarbons,respectively.The new shale oil content value,calculated from the total of these three parameters,is far more precise and reliable than traditional pyrolysis S1.Moreover,we thoroughly investigated the components and microscopic occurrence features of hydrocarbons thermally desorbed at three temperature stages using gas chromatography(GC)and X-ray microcomputed tomography(CT).For example,we selected Chang 7_(3)mud shale.Our experimental results irrefutably indicate that the ultimate shale oil content of poor resource rocks is significantly impacted by evaporative loss,with this effect being greater when the total organic carbon(TOC)is lower.Additionally,C_(1-5)and C_(1-7)hydrocarbons constitute almost all of S_(g)and S_(O),respectively.S_(g)and S_(O)are predominantly composed of C_(1-3)gaseous hydrocarbons,with a maximum proportion of 42.93%.In contrast,S_(1)^(*)contains a substantial amount of C_(16-31)hydrocarbons.A three-dimensional reconstruction model of an X-ray micro-CT scan shows that while the amount of shale organic matter greatly decreases from the frozen state to 300℃,the pore volume significantly increases,particularly between 90 and 300℃.The increased pore volume is mainly due to macropores and fractures.It is imperative to note that the shale oil triple-division boundaries must be adjusted based on more accurate oil content,although this would not affect the resource zones to which the samples already belong(ineffective,low-efficient,and enriched resources).In conclusion,we strongly advise conducting an immediate well-site analysis or utilizing preservation procedures,such as deep freezing or plastic film wrapping followed by core waxing,to minimize volatile loss.
