Organic-rich mudstones and shales,which hold significant potential for shale oil resources,characterize the first member of the Upper Cretaceous Qingshankou Formation(K_(2)qn~1)in the Sanzhao sag of the Songliao Basin...Organic-rich mudstones and shales,which hold significant potential for shale oil resources,characterize the first member of the Upper Cretaceous Qingshankou Formation(K_(2)qn~1)in the Sanzhao sag of the Songliao Basin,NE China.Focusing on 30 core samples obtained from the first shale oil parameter well,named SYY3 in the study area,we systematically analyzed the composition and stratigraphic distribution of the K_(2)qn~1 heteroatomic compounds using electrospray ionization Fourier transform-ion cyclotron resonance mass spectrometry(ESI FT-ICR MS),to assess their geological relevance to shale oil.The findings indicate that in the negative ion mode,the heteroatomic compounds predominantly consist of N_(1),N_(1)O_(1)-N_(1)O_(8),O_(1)-O_(8),O_(1)S_(1)-O_(6)S_(1);contrastingly,in the positive ion mode,they are primarily composed of N_(1)-N_(2),N_(1)O_(1)-N_(1)O_(4),N_(2)O_(1),O_(1)-O_(4),O_(1)S_(1)-O_(2)S_(1).Heteroatomic compound distributions vary significantly with depth in the negative ion mode,with minor variations in the positive ion mode.These distributions are categorized into three types based on the negative ion ratio((N_(1)+N_(1)O_(x))/O_(x)):TypeⅠ(>1.5),TypeⅡ(0.8-1.5),and TypeⅢ(<0.8);typesⅠandⅡgenerally exhibit a broader range of carbon numbers compared to TypeⅢ.The distribution of double bond equivalent(DBE)values across various sample types exhibits minimal variance,whereas that of carbon numbers shows substantial differences.Variations in heteroatomic compound compositions among the samples might have resulted from vertical sedimentary heterogeneity and differing biotic contributions.TypeⅢsamples show a decrease in total organic carbon(TOC)and free oil content(S_(1))compared to typesⅠandⅡ,but an increased oil saturation index(OSI),indicating a lower content of free oil but a higher proportion of movable oil.The reduced content of N-containing compounds implies lower paleolake productivity during deposition,leading to a reduction in TOC and S_(1).A lower TOC can enhance oil movability due to reduced oil adsorption,and the decreased presence of polar nitrogenous macromolecules with fewer highC-number heteroatomic compounds further promote shale oil movability.Additionally,the negative ion ratios of N1/N1O1and O2/O1 exhibit positive and negative correlations with the values of TOC,S_(1),and extractable organic matter(EOM),respectively,indicating that the salinity and redox conditions of the depositional water body are the primary controlling factors for both organic matter enrichment and shale oil accumulation.展开更多
Polygonal faults,generally distributed in fine-grained sediments,are layer-bound faults and are important in hydrocarbon accumulation.Using 3D seismic data,we analyzed the plane and profile features of faults develope...Polygonal faults,generally distributed in fine-grained sediments,are layer-bound faults and are important in hydrocarbon accumulation.Using 3D seismic data,we analyzed the plane and profile features of faults developed in the Qingshankou formation of the Sanzhao sag.We identified these faults as having typical features of polygonal faults:1) layer-bound;2) normal faults;3) slight fault displacements and steep in dip angles;4) multi-directional in strike and 5) a single fault has a short horizontal extension.In addition,these faults intersect each other and form polygons.These polygonal faults are the result from the combined action of compaction,volume contraction and episodic hydraulic fracturing,conditions favorable for oil/gas accumulation.They are the dominant channels for migration of fluids in the Qingshankou mudstone,forming a large number of fault-lithologic oil traps.Polygonal faults improve reservoirs.展开更多
基金jointly funded by the National Natural Science Foundation of China(Grant Nos.42072178 and U2244207)the funding project of Northeast Geological S&T Innovation Center of China Geological Survey(Grant No.QCJJ2022-37)Geological Survey Project of China Geological Survey(Grant Nos.DD20190114,DD20230022,and DD20240045)。
文摘Organic-rich mudstones and shales,which hold significant potential for shale oil resources,characterize the first member of the Upper Cretaceous Qingshankou Formation(K_(2)qn~1)in the Sanzhao sag of the Songliao Basin,NE China.Focusing on 30 core samples obtained from the first shale oil parameter well,named SYY3 in the study area,we systematically analyzed the composition and stratigraphic distribution of the K_(2)qn~1 heteroatomic compounds using electrospray ionization Fourier transform-ion cyclotron resonance mass spectrometry(ESI FT-ICR MS),to assess their geological relevance to shale oil.The findings indicate that in the negative ion mode,the heteroatomic compounds predominantly consist of N_(1),N_(1)O_(1)-N_(1)O_(8),O_(1)-O_(8),O_(1)S_(1)-O_(6)S_(1);contrastingly,in the positive ion mode,they are primarily composed of N_(1)-N_(2),N_(1)O_(1)-N_(1)O_(4),N_(2)O_(1),O_(1)-O_(4),O_(1)S_(1)-O_(2)S_(1).Heteroatomic compound distributions vary significantly with depth in the negative ion mode,with minor variations in the positive ion mode.These distributions are categorized into three types based on the negative ion ratio((N_(1)+N_(1)O_(x))/O_(x)):TypeⅠ(>1.5),TypeⅡ(0.8-1.5),and TypeⅢ(<0.8);typesⅠandⅡgenerally exhibit a broader range of carbon numbers compared to TypeⅢ.The distribution of double bond equivalent(DBE)values across various sample types exhibits minimal variance,whereas that of carbon numbers shows substantial differences.Variations in heteroatomic compound compositions among the samples might have resulted from vertical sedimentary heterogeneity and differing biotic contributions.TypeⅢsamples show a decrease in total organic carbon(TOC)and free oil content(S_(1))compared to typesⅠandⅡ,but an increased oil saturation index(OSI),indicating a lower content of free oil but a higher proportion of movable oil.The reduced content of N-containing compounds implies lower paleolake productivity during deposition,leading to a reduction in TOC and S_(1).A lower TOC can enhance oil movability due to reduced oil adsorption,and the decreased presence of polar nitrogenous macromolecules with fewer highC-number heteroatomic compounds further promote shale oil movability.Additionally,the negative ion ratios of N1/N1O1and O2/O1 exhibit positive and negative correlations with the values of TOC,S_(1),and extractable organic matter(EOM),respectively,indicating that the salinity and redox conditions of the depositional water body are the primary controlling factors for both organic matter enrichment and shale oil accumulation.
基金the National Natural Science Foundation of China (No.40672143)the National Basic Research Program of China (No.2005CB 4221007)
文摘Polygonal faults,generally distributed in fine-grained sediments,are layer-bound faults and are important in hydrocarbon accumulation.Using 3D seismic data,we analyzed the plane and profile features of faults developed in the Qingshankou formation of the Sanzhao sag.We identified these faults as having typical features of polygonal faults:1) layer-bound;2) normal faults;3) slight fault displacements and steep in dip angles;4) multi-directional in strike and 5) a single fault has a short horizontal extension.In addition,these faults intersect each other and form polygons.These polygonal faults are the result from the combined action of compaction,volume contraction and episodic hydraulic fracturing,conditions favorable for oil/gas accumulation.They are the dominant channels for migration of fluids in the Qingshankou mudstone,forming a large number of fault-lithologic oil traps.Polygonal faults improve reservoirs.
