The Lucaogou Formation in the Jimusar Sag of the eastern Junggar Basin is an important sedimentary stratum accumulating huge amounts of lacustrine tight oil in China, where organic-rich rocks are commonly observed. Fo...The Lucaogou Formation in the Jimusar Sag of the eastern Junggar Basin is an important sedimentary stratum accumulating huge amounts of lacustrine tight oil in China, where organic-rich rocks are commonly observed. Focusing on the Lucaogou Formation, a precise analysis of the inorganic and organic petrology and the inorganic geochemistry characteristics was conducted. The paleoclimate and paleoenvironment during sedimentation of the Lucaogou Formation were established,and the key factors that were controlling the accumulation of organic matter during this time were identified. The results of this study suggest that during the sedimentation of the Lucaogou Formation, the paleoclimate periodically changed from a humid environment to an arid environment. As a result, the salinity of the water and the redox environment fluctuated.During the sedimentation period, the lake showed su cient nutrient supplies and a high primary productivity. The interval studies in the Lucaogou Formation were divided into five sedimentary cycles, where the first, second, and fifth sedimentary cycles consisted of cyclical paleoclimate fluctuations varied from a humid environment to an arid environment and shifted back to a humid environment with levels of salinity from low to high and decreased again. The third and fourth cycles have cyclical fluctuations from a humid to an arid environment and corresponding salinity variation between low and high levels.During the period when organic-rich rocks in the Lucaogou Formation deposited in the Jimusar Sag, the paleoclimate and the water body were suitable for lower aquatic organisms to flourish. As a result, its paleoproductivity was high, especially during the early period of each cycle. A quiet deep water body is likely to form an anoxic environment at the bottom and is also good for accumulation and preservation of organisms. Fine-grained sediments were accumulated at a low deposition rate, with a low dilution of organic matter. Therefore, high paleoproductivity provided a su cient volume of organisms in the studied area in a quiet deep water body with an anoxic environment and these were the key factors controlling formation of organic-rich rocks.展开更多
Unconventional oil and gas resources require petrophysical logs to answer the question of how best to optimize geological and engineering‘sweet spots'.Therefore,the establishment of a key well with comprehensive ...Unconventional oil and gas resources require petrophysical logs to answer the question of how best to optimize geological and engineering‘sweet spots'.Therefore,the establishment of a key well with comprehensive descriptions of lithology,reservoir properties,hydrocarbon-bearing properties,electronic well log responses,source rock properties,brittleness,and in situ stress magnitude and direction is important for the effective exploration and production of unconventional hydrocarbon resources.Cores,thin sections,scanning electron microscopy(SEM)and comprehensive well log suites are used to build a key well for the Permian Lucaogou Formation,Jimusar Sag of the Junggar Basin.The results show that there are three main types of lithologies,including siltstone,mudstone and dolostone.Lithologies can be predicted using the combination of conventional well and image logs.The pore spaces consist of interparticle pores,intragranular dissolution pores and micropores.Nuclear Magnetic Resonance(NMR)T_(2)components longer than 1.7 ms are superposed as effective porosity.Permeability is calculated using the Coates model from NMR T_(2)spectra.The ratio of T_(2)components>7.0 ms to T_(2)components>0.3 ms is used to calculate oil saturation.TOC is calculated using theΔlog R method.Brittleness index is calculated using Poisson-Young's method,ranging from 13.42%-70.53%.In situ stress direction is determined,and in situ stress magnitudes(maximum horizontal stress SH_(max),minimum horizontal stress Sh_(min),vertical stress S_(v))are calculated using density and sonic logs.The strike-slip stress type(SH_(max)>S_(v)>Sh_(min))is encountered.The key well which comprehensively includes the above seven properties is established.Geological and engineering(geomechanical)‘sweet spots'are then optimized from the key well by fully analyzing lithology,reservoir property,oilbearing potential,in situ stress magnitude and brittleness.It is hoped that the results support engineers'and geologists'decisions for the future exploitation of unconventional hydrocarbon resources.展开更多
Granular calcite is an authigenic mineral in fine-grained sedimentary rocks.Core observation,thin section observation,cathodoluminescence analysis,fluid inclusion analysis,scanning electron microscope(SEM),and isotopi...Granular calcite is an authigenic mineral in fine-grained sedimentary rocks.Core observation,thin section observation,cathodoluminescence analysis,fluid inclusion analysis,scanning electron microscope(SEM),and isotopic composition analysis were combined to clarify the genesis of granular calcite in the lacustrine fine-grained sedimentary rocks of the Permian Lucaogou Formation in the Jimusar Sag,Junggar Basin.It is found that the granular calcite is distributed with laminated characteristics in fine-grained sedimentary rocks in tuffite zones(or the transitional zone between tuffite and micritic dolomite).Granular calcite has obvious cathodoluminesence band,and it can be divided into three stages.Stage-Ⅰ calcite,with non-luminesence,high content of Sr element,inclusions containing Cos,and homogenization temperature higher than 170℃,was directly formed from the volcanic-hydrothermal deposition.Stage-Ⅱ calcite,with bright yellow luminescence,high contents of Fe,Mn and Mg,enrichment of light rare earth elements(LREEs),and high homogenization temperature,was formed by recrystallization of calcareous edges from exhalative hydrothermal deposition.Stage-IlI calcite,with dark orange luminescence band,high contents of Mg,P,V and other elements,no obvious fractionation among LREEs,and low homogenization temperature,was originated from diagenetic transformation during burial.The granular calcite appears regularly in the vertical direction and its formation temperature decreases from the center to the margin of particles,providing direct evidences for volcanic-hydrothermal events during the deposition of the Lucaogou Formation.The volcanic-hydrothermal event was conducive to the enrichment of organic matters in fine-grained sedimentary rocks of the Lucaogrou Formation,and positive to the development of high-quality source rocks.The volcanic-hydrothermal sediments might generate intergranular pores/fractures during the evolution,creating conditions for the self-generation and self-storage of shale oil.展开更多
The diagenesis and diagenetic facies of shale reservoirs in Lucaogou Formation of Jimusar Sag were studied by means of microscopic observation and identification of ordinary thin sections and cast thin sections,X-ray ...The diagenesis and diagenetic facies of shale reservoirs in Lucaogou Formation of Jimusar Sag were studied by means of microscopic observation and identification of ordinary thin sections and cast thin sections,X-ray diffraction,scanning electron microscope and electron probe tests.The results show that alkaline and acidic diagenetic processes occurred alternately during the deposition of Permian Lucaogou Formation in Jimusar Sag.The evolution of porosity in the shale reservoirs was influenced by compaction and alternate alkaline and acidic diagenetic processes jointly,and has gone through three stages,namely,stage of porosity reduction and increase caused by alkaline compaction,stage of porosity increase caused by acid dissolution,and stage of porosity increase and reduction caused by alkaline dissolution.Correspondingly,three secondary pore zones developed in Lucaogou Formation.The shale reservoirs are divided into three diagenetic facies:tuff residual intergranular pore-dissolution pore facies,tuff organic micrite dolomite mixed pore facies,and micrite alga-dolomite intercrystalline pore facies.With wide distribution,good pore structure and high oil content,the first two facies are diagenetic facies of favorable reservoirs in Lucaogou Formation.The research results provide a basis for better understanding and exploration and development of the Lucaogou Formation shale reservoirs.展开更多
Aiming at the complicated problem of the genesis of high-quality hybrid sedimentary rocks,the pore-throat systems,controlling factors and fluid mobility of hybrid sedimentary rocks in the Permian Lucaogou Formation in...Aiming at the complicated problem of the genesis of high-quality hybrid sedimentary rocks,the pore-throat systems,controlling factors and fluid mobility of hybrid sedimentary rocks in the Permian Lucaogou Formation in Jimusar Sag were examined.The results show that the hybrid sedimentary rocks contain 5 types of pore-throat system,intergranular(Type A),mixed intergranular-dissolved-intercrystalline(Type B),dissolved(Type C),mixed dissolved-intercrystalline(Type D)and intercrystalline(Type E)ones.The pore-throat systems are controlled by 3 major factors,the component content and arrangement(CCA)of hybrid sedimentary rocks,sedimentary environment and diagenesis.CCA controls the matrix support mode of hybrid sedimentary rocks,and therefore controls the types and changes of pore-throat system.The sedimentary environment mainly controls the macroscopic distribution of pore-throat system,i.e.,hybrid sedimentary rocks deposited in the near source and high-energy environment are characterized by high content of coarse-grained component,granular/interbedded-support mode,and development of Type A and Type B pore-throat systems.Hybrid sedimentary rocks deposited in the medium-energy environment far from source are characterized by dolomitic/mud support mode and Type C and Type D pore-throat systems.Hybrid sedimentary rocks deposited in low-energy environment far from source have mainly Type E and Type D pore-throat systems.Diagenetic processes such as compaction and calcite cementation make the proportions of Type A and Type C pore-throat systems decrease further.In the hybrid sedimentary process of sandy-mud,pore-throat system types show a change of"A→B→C→D",in that of dolomite-sand,pore-throat system types show a change of"A→C→D→E"or"B→D→E",and in that of dolomite-mud,pore-throat system types show a change of"D→E",which are affected in details by the contents of coarse-grain component,feldspar and dolomite.The reservoir with Type A pore-throats has the best physical properties and fluid mobility,and the reservoirs with Type D and Type E pore-throats have the poorest.The movable fluid distribution is related to the matrix support mode,and the larger pores in hybrid sedimentary rocks of dolomite/mud support mode have no obvious advantage in fluid mobility.The findings of this study provide a geological basis for evaluating and building reasonable interpretation model of hybrid sedimentary rocks sweet spot.展开更多
准噶尔盆地吉木萨尔凹陷二叠系芦草沟组含有丰富的油气资源,其烃源岩主要有页岩、碳酸盐质页岩和粉砂质泥岩,它们均具有有机质丰度高、生烃潜力大、当前处于低成熟至成熟阶段、有机质类型以Ⅰ型和Ⅱ型为主的特征,在对其特征进行评价的...准噶尔盆地吉木萨尔凹陷二叠系芦草沟组含有丰富的油气资源,其烃源岩主要有页岩、碳酸盐质页岩和粉砂质泥岩,它们均具有有机质丰度高、生烃潜力大、当前处于低成熟至成熟阶段、有机质类型以Ⅰ型和Ⅱ型为主的特征,在对其特征进行评价的基础上,选取中—低成熟度、有机质丰度较高的烃源岩进行开放体系条件下的热解实验和动力学模拟实验,进而研究烃源岩样品的生排烃特征。结果表明,芦草沟组烃源岩活化能主要为210 k J/mol;上述3种烃源岩中,页岩具有最高的生烃量和排烃效率,碳酸盐质页岩次之,而粉砂质泥岩的生烃量和排烃率均最低,但前两者却具有较高的滞留烃含量。综合前人的研究成果,最终认为芦草沟组烃源岩生烃增压作用是烃源岩排烃和致密油气聚集的主要动力,页岩和碳酸盐质页岩段是致密油勘探的目标层段。展开更多
基金supported by the National Science and Technology Major Program of China(Grant No.2017ZX05009002)the National Basic Research Program of China(Grant No.2014CB239002)+1 种基金the Natural Science Foundation of Shandong Province,China(Grant No.ZR2014DQ016)the Natural Science Foundation Joint Special of Shandong Province,China(Grant No.ZR2016DL05)
文摘The Lucaogou Formation in the Jimusar Sag of the eastern Junggar Basin is an important sedimentary stratum accumulating huge amounts of lacustrine tight oil in China, where organic-rich rocks are commonly observed. Focusing on the Lucaogou Formation, a precise analysis of the inorganic and organic petrology and the inorganic geochemistry characteristics was conducted. The paleoclimate and paleoenvironment during sedimentation of the Lucaogou Formation were established,and the key factors that were controlling the accumulation of organic matter during this time were identified. The results of this study suggest that during the sedimentation of the Lucaogou Formation, the paleoclimate periodically changed from a humid environment to an arid environment. As a result, the salinity of the water and the redox environment fluctuated.During the sedimentation period, the lake showed su cient nutrient supplies and a high primary productivity. The interval studies in the Lucaogou Formation were divided into five sedimentary cycles, where the first, second, and fifth sedimentary cycles consisted of cyclical paleoclimate fluctuations varied from a humid environment to an arid environment and shifted back to a humid environment with levels of salinity from low to high and decreased again. The third and fourth cycles have cyclical fluctuations from a humid to an arid environment and corresponding salinity variation between low and high levels.During the period when organic-rich rocks in the Lucaogou Formation deposited in the Jimusar Sag, the paleoclimate and the water body were suitable for lower aquatic organisms to flourish. As a result, its paleoproductivity was high, especially during the early period of each cycle. A quiet deep water body is likely to form an anoxic environment at the bottom and is also good for accumulation and preservation of organisms. Fine-grained sediments were accumulated at a low deposition rate, with a low dilution of organic matter. Therefore, high paleoproductivity provided a su cient volume of organisms in the studied area in a quiet deep water body with an anoxic environment and these were the key factors controlling formation of organic-rich rocks.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.42002133,42072150)the Strategic Cooperation Project of Petro China and CUPB(Grant No.ZLZX2020-01-06-01)the Science Foundation of China University of Petroleum,Beijing(Grant No.2462021YXZZ003)。
文摘Unconventional oil and gas resources require petrophysical logs to answer the question of how best to optimize geological and engineering‘sweet spots'.Therefore,the establishment of a key well with comprehensive descriptions of lithology,reservoir properties,hydrocarbon-bearing properties,electronic well log responses,source rock properties,brittleness,and in situ stress magnitude and direction is important for the effective exploration and production of unconventional hydrocarbon resources.Cores,thin sections,scanning electron microscopy(SEM)and comprehensive well log suites are used to build a key well for the Permian Lucaogou Formation,Jimusar Sag of the Junggar Basin.The results show that there are three main types of lithologies,including siltstone,mudstone and dolostone.Lithologies can be predicted using the combination of conventional well and image logs.The pore spaces consist of interparticle pores,intragranular dissolution pores and micropores.Nuclear Magnetic Resonance(NMR)T_(2)components longer than 1.7 ms are superposed as effective porosity.Permeability is calculated using the Coates model from NMR T_(2)spectra.The ratio of T_(2)components>7.0 ms to T_(2)components>0.3 ms is used to calculate oil saturation.TOC is calculated using theΔlog R method.Brittleness index is calculated using Poisson-Young's method,ranging from 13.42%-70.53%.In situ stress direction is determined,and in situ stress magnitudes(maximum horizontal stress SH_(max),minimum horizontal stress Sh_(min),vertical stress S_(v))are calculated using density and sonic logs.The strike-slip stress type(SH_(max)>S_(v)>Sh_(min))is encountered.The key well which comprehensively includes the above seven properties is established.Geological and engineering(geomechanical)‘sweet spots'are then optimized from the key well by fully analyzing lithology,reservoir property,oilbearing potential,in situ stress magnitude and brittleness.It is hoped that the results support engineers'and geologists'decisions for the future exploitation of unconventional hydrocarbon resources.
基金Supported by the National Natural Science Foundation Project of China(42072161)College Basic Research Funding Project(22CX07008A).
文摘Granular calcite is an authigenic mineral in fine-grained sedimentary rocks.Core observation,thin section observation,cathodoluminescence analysis,fluid inclusion analysis,scanning electron microscope(SEM),and isotopic composition analysis were combined to clarify the genesis of granular calcite in the lacustrine fine-grained sedimentary rocks of the Permian Lucaogou Formation in the Jimusar Sag,Junggar Basin.It is found that the granular calcite is distributed with laminated characteristics in fine-grained sedimentary rocks in tuffite zones(or the transitional zone between tuffite and micritic dolomite).Granular calcite has obvious cathodoluminesence band,and it can be divided into three stages.Stage-Ⅰ calcite,with non-luminesence,high content of Sr element,inclusions containing Cos,and homogenization temperature higher than 170℃,was directly formed from the volcanic-hydrothermal deposition.Stage-Ⅱ calcite,with bright yellow luminescence,high contents of Fe,Mn and Mg,enrichment of light rare earth elements(LREEs),and high homogenization temperature,was formed by recrystallization of calcareous edges from exhalative hydrothermal deposition.Stage-IlI calcite,with dark orange luminescence band,high contents of Mg,P,V and other elements,no obvious fractionation among LREEs,and low homogenization temperature,was originated from diagenetic transformation during burial.The granular calcite appears regularly in the vertical direction and its formation temperature decreases from the center to the margin of particles,providing direct evidences for volcanic-hydrothermal events during the deposition of the Lucaogou Formation.The volcanic-hydrothermal event was conducive to the enrichment of organic matters in fine-grained sedimentary rocks of the Lucaogrou Formation,and positive to the development of high-quality source rocks.The volcanic-hydrothermal sediments might generate intergranular pores/fractures during the evolution,creating conditions for the self-generation and self-storage of shale oil.
基金Supported by the China National Science and Technology Major Project(2017ZX05008-004-008)the PetroChina Science and Technology Major Project(2017E-0401)
文摘The diagenesis and diagenetic facies of shale reservoirs in Lucaogou Formation of Jimusar Sag were studied by means of microscopic observation and identification of ordinary thin sections and cast thin sections,X-ray diffraction,scanning electron microscope and electron probe tests.The results show that alkaline and acidic diagenetic processes occurred alternately during the deposition of Permian Lucaogou Formation in Jimusar Sag.The evolution of porosity in the shale reservoirs was influenced by compaction and alternate alkaline and acidic diagenetic processes jointly,and has gone through three stages,namely,stage of porosity reduction and increase caused by alkaline compaction,stage of porosity increase caused by acid dissolution,and stage of porosity increase and reduction caused by alkaline dissolution.Correspondingly,three secondary pore zones developed in Lucaogou Formation.The shale reservoirs are divided into three diagenetic facies:tuff residual intergranular pore-dissolution pore facies,tuff organic micrite dolomite mixed pore facies,and micrite alga-dolomite intercrystalline pore facies.With wide distribution,good pore structure and high oil content,the first two facies are diagenetic facies of favorable reservoirs in Lucaogou Formation.The research results provide a basis for better understanding and exploration and development of the Lucaogou Formation shale reservoirs.
基金Supported by the National Key Basic Research and Development Program(2015CB250906)National Natural Science Foundation of China(41972139,41922015)Special Funds for Basic Scientific Research in Central Universities(18CX02069A)。
文摘Aiming at the complicated problem of the genesis of high-quality hybrid sedimentary rocks,the pore-throat systems,controlling factors and fluid mobility of hybrid sedimentary rocks in the Permian Lucaogou Formation in Jimusar Sag were examined.The results show that the hybrid sedimentary rocks contain 5 types of pore-throat system,intergranular(Type A),mixed intergranular-dissolved-intercrystalline(Type B),dissolved(Type C),mixed dissolved-intercrystalline(Type D)and intercrystalline(Type E)ones.The pore-throat systems are controlled by 3 major factors,the component content and arrangement(CCA)of hybrid sedimentary rocks,sedimentary environment and diagenesis.CCA controls the matrix support mode of hybrid sedimentary rocks,and therefore controls the types and changes of pore-throat system.The sedimentary environment mainly controls the macroscopic distribution of pore-throat system,i.e.,hybrid sedimentary rocks deposited in the near source and high-energy environment are characterized by high content of coarse-grained component,granular/interbedded-support mode,and development of Type A and Type B pore-throat systems.Hybrid sedimentary rocks deposited in the medium-energy environment far from source are characterized by dolomitic/mud support mode and Type C and Type D pore-throat systems.Hybrid sedimentary rocks deposited in low-energy environment far from source have mainly Type E and Type D pore-throat systems.Diagenetic processes such as compaction and calcite cementation make the proportions of Type A and Type C pore-throat systems decrease further.In the hybrid sedimentary process of sandy-mud,pore-throat system types show a change of"A→B→C→D",in that of dolomite-sand,pore-throat system types show a change of"A→C→D→E"or"B→D→E",and in that of dolomite-mud,pore-throat system types show a change of"D→E",which are affected in details by the contents of coarse-grain component,feldspar and dolomite.The reservoir with Type A pore-throats has the best physical properties and fluid mobility,and the reservoirs with Type D and Type E pore-throats have the poorest.The movable fluid distribution is related to the matrix support mode,and the larger pores in hybrid sedimentary rocks of dolomite/mud support mode have no obvious advantage in fluid mobility.The findings of this study provide a geological basis for evaluating and building reasonable interpretation model of hybrid sedimentary rocks sweet spot.
文摘准噶尔盆地吉木萨尔凹陷二叠系芦草沟组含有丰富的油气资源,其烃源岩主要有页岩、碳酸盐质页岩和粉砂质泥岩,它们均具有有机质丰度高、生烃潜力大、当前处于低成熟至成熟阶段、有机质类型以Ⅰ型和Ⅱ型为主的特征,在对其特征进行评价的基础上,选取中—低成熟度、有机质丰度较高的烃源岩进行开放体系条件下的热解实验和动力学模拟实验,进而研究烃源岩样品的生排烃特征。结果表明,芦草沟组烃源岩活化能主要为210 k J/mol;上述3种烃源岩中,页岩具有最高的生烃量和排烃效率,碳酸盐质页岩次之,而粉砂质泥岩的生烃量和排烃率均最低,但前两者却具有较高的滞留烃含量。综合前人的研究成果,最终认为芦草沟组烃源岩生烃增压作用是烃源岩排烃和致密油气聚集的主要动力,页岩和碳酸盐质页岩段是致密油勘探的目标层段。
