Authigenic clays and calcite cements are important in the development of reservoir tightness and the formation of hydrocarbon sweet spots.We investigated Jurassic low-permeability sandstone reservoirs in the central J...Authigenic clays and calcite cements are important in the development of reservoir tightness and the formation of hydrocarbon sweet spots.We investigated Jurassic low-permeability sandstone reservoirs in the central Junggar Basin,NW China,using petrography,mineralogy,porosity,and permeability assessment,and stable C and O isotope analysis to ascertain the influence of authigenic clays and calcites on reservoir quality.Here,we establish the properties and diagenetic processes of the reservoir sandstones,and construct a generalizable model of reservoir quality.The results show that the sandstones are mainly litharenite and feldspathic litharenite and can be classified into ductile-lithic-rich sandstones and ductile-lithic-poor sandstones according to rock composition.The ductile-lithic-rich sandstones are tight(mean porosity?7.31%;mean permeability?0.08 mD)as a result of intense compaction.In contrast,the ductile-lithic-poor sandstones can be classified into five types according to diagenetic process.The formation of favorable hydrocarbon reservoir properties is closely related to the presence of authigenic clays and dissolution of calcite.In particular,kaolinite fills intergranular pores,thereby blocking pore space and reducing reservoir quality.Chlorite coating resists compaction and limits the formation of quartz overgrowths,thereby preserving pore space and enhancing reservoir quality.Calcite controls reservoir quality through both precipitation and dissolution.Calcite precipitation results in reduced reservoir quality,whereby early calcites that were precipitated in formation water resist compaction and provide the basis for subsequent dissolution and late precipitation,whereas dissolution of calcite in mesodiagenesis improves reservoir quality.A generalized model is formulated by relating diagenetic facies types to depth and porosity,providing a reference for other similar reservoirs.Our data suggest that deeply buried tight sandstones can be exploration prospects under favorable conditions involving the presence of authigenic clays and dissolution of calcite,as in the central Junggar Basin of this study.展开更多
油源对比微量元素地球化学示踪是油气地球化学领域的前沿科学问题.以准噶尔盆地二叠系风城组碱湖含油气系统为例,对此进行了探索研究.通过对烃源岩和原油样品的微量元素组成进行电感耦合等离子体质谱(inductively coupled plasma mass s...油源对比微量元素地球化学示踪是油气地球化学领域的前沿科学问题.以准噶尔盆地二叠系风城组碱湖含油气系统为例,对此进行了探索研究.通过对烃源岩和原油样品的微量元素组成进行电感耦合等离子体质谱(inductively coupled plasma mass spectrometry,ICP-MS)分析和系统对比,发现检出的33个常见微量元素中,过渡族金属元素(Ti、V、Cr、Ni、Cu、Zn、Mn和Zr)、碱土金属元素(Sr和Ba)和非金属元素(B和As)在烃源岩与原油间具有较好的继承性,展示出油源对比和示踪意义,但由源到油,元素含量下降0.3~1141倍,差异富集特征显著,表明不能直接简单应用于油源对比.分析认为,微量元素从源到油的差异富集主要受控于微量元素以有机络(螯)合物或无机盐离子形式在有机质成烃演化与成藏过程中的动态分配.Ni和部分V以N–Ni/V键合于卟啉化合物,受油气运移影响小,相对稳定;大部分V以难溶矿物相赋存,油气初次运移时优先富集于烃源岩;Cr、Cu和Zn与有机酸中O/S原子络合,但在油气二次运移过程中化学键容易破裂;Mn、Zr、Ti、Sr和Ba主要以矿物相赋存于烃源岩中,在油气运移中以离子形式存在,易受油-岩相互作用发生离子交换;B以矿物相赋存于烃源岩中,但在初次运移时易与有机酸络合且受二次运移影响有限;As主要以砷化物或砷酸根离子赋存,受二次运移影响较大.据此,Ni、V、B、Cr、Cu、Zn和As具有较好的示踪意义,形成了4组参数:Ni含量进行油源对比、V/Ni和Ni/B示踪初次运移、Cr–Cu+Zn–As三端元图示踪二次运移.油气形成演化过程中的元素地球化学行为复杂,可在深入剖析后遴选有效参数应用于油气示踪,是经典有机地球化学方法的有效补充.展开更多
Maturity evaluation of highly evolved organic matter is an important problem in oil and gas geochemistry,because conventional organic geochemical proxies are not applicable due to hydrocarbon generation and expulsion....Maturity evaluation of highly evolved organic matter is an important problem in oil and gas geochemistry,because conventional organic geochemical proxies are not applicable due to hydrocarbon generation and expulsion.In this study,we investigated the pyrobitumen in the reservoirs of the Sinian Dengying Formation in the Sichuan Basin,China.We focused on aromatic hydrocarbon biomarkers,and the calibration and application of aromatic maturity proxies using pyrobitumen reflectance and Raman spectral parameters.Our results show that only the thiophene compounds are effective maturity indicators,such as MDR(4-/1-MDBT),MDR′(4-MDBT/(1-MDBT+4-MDBT)),MDR1(1-MDBT/DBT),4,6-/(1,4+1,6)-DMDBT,(2,6+3,6)-/(1,4+1,6)-DMDBT,and[2,1]BNT/([2,1]BNT+[1,2]BNT),as these are largely independent of the optical anisotropy of pyrobitumen.The condensation and incorporation of thiophene compounds can lead to an increase in the reflectance of pyrobitumen,which means the thiophene compound parameters are positively or negatively correlated with pyrobitumen reflectance.New potential maturity parameters were proposed,including DMDBTs/MDBTs,TeMDBTs/(DBT+MDBTs+DMDBTs+TMDBTs+TeMDBTs),1-MDBT/MDBTs,and[2,1]BNT/BNTs.This method and these parameters are universally applicable to maturity characterization,especially in rocks that lack vitrinite,contain strongly anisotropic organic matter,and have high contents of thiophene compounds.展开更多
基金This work was funded by the National Science and Technology Major Project of China(Grant No.2016ZX05002-006-005)National Natural Science Foundation of China(Grant No.41830425).
文摘Authigenic clays and calcite cements are important in the development of reservoir tightness and the formation of hydrocarbon sweet spots.We investigated Jurassic low-permeability sandstone reservoirs in the central Junggar Basin,NW China,using petrography,mineralogy,porosity,and permeability assessment,and stable C and O isotope analysis to ascertain the influence of authigenic clays and calcites on reservoir quality.Here,we establish the properties and diagenetic processes of the reservoir sandstones,and construct a generalizable model of reservoir quality.The results show that the sandstones are mainly litharenite and feldspathic litharenite and can be classified into ductile-lithic-rich sandstones and ductile-lithic-poor sandstones according to rock composition.The ductile-lithic-rich sandstones are tight(mean porosity?7.31%;mean permeability?0.08 mD)as a result of intense compaction.In contrast,the ductile-lithic-poor sandstones can be classified into five types according to diagenetic process.The formation of favorable hydrocarbon reservoir properties is closely related to the presence of authigenic clays and dissolution of calcite.In particular,kaolinite fills intergranular pores,thereby blocking pore space and reducing reservoir quality.Chlorite coating resists compaction and limits the formation of quartz overgrowths,thereby preserving pore space and enhancing reservoir quality.Calcite controls reservoir quality through both precipitation and dissolution.Calcite precipitation results in reduced reservoir quality,whereby early calcites that were precipitated in formation water resist compaction and provide the basis for subsequent dissolution and late precipitation,whereas dissolution of calcite in mesodiagenesis improves reservoir quality.A generalized model is formulated by relating diagenetic facies types to depth and porosity,providing a reference for other similar reservoirs.Our data suggest that deeply buried tight sandstones can be exploration prospects under favorable conditions involving the presence of authigenic clays and dissolution of calcite,as in the central Junggar Basin of this study.
文摘油源对比微量元素地球化学示踪是油气地球化学领域的前沿科学问题.以准噶尔盆地二叠系风城组碱湖含油气系统为例,对此进行了探索研究.通过对烃源岩和原油样品的微量元素组成进行电感耦合等离子体质谱(inductively coupled plasma mass spectrometry,ICP-MS)分析和系统对比,发现检出的33个常见微量元素中,过渡族金属元素(Ti、V、Cr、Ni、Cu、Zn、Mn和Zr)、碱土金属元素(Sr和Ba)和非金属元素(B和As)在烃源岩与原油间具有较好的继承性,展示出油源对比和示踪意义,但由源到油,元素含量下降0.3~1141倍,差异富集特征显著,表明不能直接简单应用于油源对比.分析认为,微量元素从源到油的差异富集主要受控于微量元素以有机络(螯)合物或无机盐离子形式在有机质成烃演化与成藏过程中的动态分配.Ni和部分V以N–Ni/V键合于卟啉化合物,受油气运移影响小,相对稳定;大部分V以难溶矿物相赋存,油气初次运移时优先富集于烃源岩;Cr、Cu和Zn与有机酸中O/S原子络合,但在油气二次运移过程中化学键容易破裂;Mn、Zr、Ti、Sr和Ba主要以矿物相赋存于烃源岩中,在油气运移中以离子形式存在,易受油-岩相互作用发生离子交换;B以矿物相赋存于烃源岩中,但在初次运移时易与有机酸络合且受二次运移影响有限;As主要以砷化物或砷酸根离子赋存,受二次运移影响较大.据此,Ni、V、B、Cr、Cu、Zn和As具有较好的示踪意义,形成了4组参数:Ni含量进行油源对比、V/Ni和Ni/B示踪初次运移、Cr–Cu+Zn–As三端元图示踪二次运移.油气形成演化过程中的元素地球化学行为复杂,可在深入剖析后遴选有效参数应用于油气示踪,是经典有机地球化学方法的有效补充.
基金supported by the National Natural Science Foundation of China(Grant Nos.42230808 and 41830425).
文摘Maturity evaluation of highly evolved organic matter is an important problem in oil and gas geochemistry,because conventional organic geochemical proxies are not applicable due to hydrocarbon generation and expulsion.In this study,we investigated the pyrobitumen in the reservoirs of the Sinian Dengying Formation in the Sichuan Basin,China.We focused on aromatic hydrocarbon biomarkers,and the calibration and application of aromatic maturity proxies using pyrobitumen reflectance and Raman spectral parameters.Our results show that only the thiophene compounds are effective maturity indicators,such as MDR(4-/1-MDBT),MDR′(4-MDBT/(1-MDBT+4-MDBT)),MDR1(1-MDBT/DBT),4,6-/(1,4+1,6)-DMDBT,(2,6+3,6)-/(1,4+1,6)-DMDBT,and[2,1]BNT/([2,1]BNT+[1,2]BNT),as these are largely independent of the optical anisotropy of pyrobitumen.The condensation and incorporation of thiophene compounds can lead to an increase in the reflectance of pyrobitumen,which means the thiophene compound parameters are positively or negatively correlated with pyrobitumen reflectance.New potential maturity parameters were proposed,including DMDBTs/MDBTs,TeMDBTs/(DBT+MDBTs+DMDBTs+TMDBTs+TeMDBTs),1-MDBT/MDBTs,and[2,1]BNT/BNTs.This method and these parameters are universally applicable to maturity characterization,especially in rocks that lack vitrinite,contain strongly anisotropic organic matter,and have high contents of thiophene compounds.
