The shale of the Cambrian Qiongzhusi Formation in the Sichuan Basin is characterized by large burial depth and high maturity,but the shale gas enrichment pattern is still unclear.Based on the detailed characterization...The shale of the Cambrian Qiongzhusi Formation in the Sichuan Basin is characterized by large burial depth and high maturity,but the shale gas enrichment pattern is still unclear.Based on the detailed characterization of Deyang-Anyue aulacogen,analysis of its depositional environments,together with reconstruction of shale gas generation and enrichment evolution against the background of the Leshan-Longnüsi paleouplift,the aulacogen-uplift enrichment pattern was elucidated.It is revealed that the Deyang-Anyue aulacogen controls the depositional environment of the Qiongzhusi Formation,where high-quality sedimentary facies and thick strata are observed.Meanwhile,the Leshan-Longnüsi paleouplift controls the maturity evolution of the shale in the Qiongzhusi Formation,with the uplift located in a high position and exhibiting a moderate degree of thermal evolution and a high resistivity.The aulacogen-uplift overlap area is conducive to the enrichment of shale gas during the deposition,oil generation,gas generation,and oil-gas adjustment stage,which also has a joint control on the development of reservoirs,resulting in multiple reservoirs of high quality and large thickness.Based on the aulacogen-uplift enrichment pattern and combination,four types of shale gas play are identified,and the sweet spot evaluation criteria for the Qiongzhusi Formation is established.Accordingly,a sweet spot area of 8200 km^(2)in the aulacogen is determined,successfully guiding the deployment of Well Zi 201 with a high-yield industrial gas flow of 73.88×10^(4) m^(3)/d.The new geological insights on the aulacogen-uplift enrichment pattern provide a significant theoretical basis for the exploration and breakthrough of deep to ultra-deep Cambrian shale gas,highlighting the promising exploration prospect in this domain.展开更多
The Chang 73 sub-member of Triassic Yanchang Formation in the Ordos Basin was taken as an example and the lamina types and combinations,reservoir space features and shale oil enrichment patterns in organic-rich shale ...The Chang 73 sub-member of Triassic Yanchang Formation in the Ordos Basin was taken as an example and the lamina types and combinations,reservoir space features and shale oil enrichment patterns in organic-rich shale strata were investigated using core observation,thin section analysis,XRF element measurement,XRD analysis,SEM,high solution laser Raman spectroscopy analysis,and micro-FTIR spectroscopy analysis,etc.According to the mineral composition and thickness of the laminae,the Chang 73 organic-rich shales have four major types of laminae,tuff-rich lamina,organic-rich lamina,silt-grade feldspar-quartz lamina and clay lamina.They have two kinds of shale oil-bearing layers,"organic-rich lamina+silt-grade feldspar-quartz lamina"and"organic-rich lamina+tuff-rich lamina"layers.In the"organic-rich+silt-grade feldspar-quartz"laminae combination shale strata,oil was characterized by relative high maturation,and always filled in K-feldspar dissolution pores in the silt-grade feldspar-quartz laminae,forming oil generation,migration and accumulation process between laminae inside the organic shales.In the"organic-rich+tuff-rich lamina"binary laminae combination shale strata,however,the reservoir properties were poor in organic-rich shales,the oil maturation was relatively lower,and mainly accumulated in the intergranular pores of interbedded thin-layered sandstones.The oil generation,migration and accumulation mainly occurred between organic-rich shales and interbedded thin-layered sandstones.展开更多
The quest for enrichment model of continental shale oil in the Zhanhua Sag of the JiyangDepression in the Bohai Bay Basin to provide reference for exploration and development requires acomprehensive approach. Therefor...The quest for enrichment model of continental shale oil in the Zhanhua Sag of the JiyangDepression in the Bohai Bay Basin to provide reference for exploration and development requires acomprehensive approach. Therefore, this study employs rock pyrolysis, Scanning Electron Microscopy(SEM), X-Ray diffraction analysis (XRD), Nuclear Magnetic Resonance (NMR), and other experiments toanalyze the conditions for shale oil enrichment and establish its patterns. The results show that favorablehydrocarbon generation potential and appropriate thermal maturation degree control “in situ enrichment”;while the storage capacity and the mobility of shale oil determine “migration enrichment.” In the process,the TOC governs the oil-generating capacity of shale with medium to large pores and microfractures servingas the main enrichment spaces and migration pathways for shale oil. Based on the deposition model, thestudy area can be divided into five lithofacies stages (I-algal limestone, II-laminated marl, III-laminatedrecrystallized limestone, IV-laminated mudstones, and IV-blocky calcareous mudstones). Integrating thegeochemical parameters into the sedimentary patterns makes it clear that the study area underwent two phasesof hydrocarbon expulsion during the thermal evolution of source rocks (Stage II: 3 060–3 120 m and StageIV: 3 020–3 040 m). However, judging by the observed TOC (2% to 5.6%), thermal maturity (Ro>0.8%),S1 (>2 mg/g) and OSI (>100 mg/g) as well as moderate basin size, climate, and quantity of terrestrial input,the blocky calcareous mudstones (Stage IV) have better oil-prone characteristics and potential to generate asubstantial quantity of hydrocarbons at this stage. More so, with a brittleness index exceeding 60%, it exhibitsfavorable fracturability accounting for the main controlling factors and enrichment patterns of shale oil in thearea. Hence, this study further enriches and develops the theoretical understanding of shale oil enrichment inthe area, provides valuable insights for future exploration of continental shale oil in eastern China and othersimilar basin around the world.展开更多
The distribution and enrichment patterns of selenium(Se) in the E-?1 strata in the Yangtze Gorges area of South China were obtained. The geochemical characteristics of the significantly and non-significantly enriched ...The distribution and enrichment patterns of selenium(Se) in the E-?1 strata in the Yangtze Gorges area of South China were obtained. The geochemical characteristics of the significantly and non-significantly enriched strata of Se were analyzed.The observed enrichment factor(EF, relative to the upper continental crust) and concentration coefficient(CC, relative to the similar lithology in Eastern China) both suggest that Se is the most enriched/concentrated(SeEF=26.97, SeCC=48.04) among the analyzed23 trace elements the E-?1 strata. The normalized enrichment factor(EF′, EF after Al or Th normalized) shows Se is secondly enriched(SeEF′=218.73), which is slightly lower than cadmium(CdEF′=288.46) but significantly higher than the third enriched trace element arsenic(AsEF′=97.49). Se concentrations in the E-?1 strata vary from <10.5 to 30.08 ppm with an arithmetic mean value of 1.35 ppm. Compared to the Nantuo Formation, Se increased 11.78 times in the whole E-?1 strata and the average EF values are displayed as Shuijingtuo(92.58)>Yanjiahe(54.45)>Doushantuo(24.72)>Dengying(2.48)>Shipai(1.95)>lower Tianheban(1.24)Formations. Se concentrations in the E-?1 strata are best displayed on natural logarithm normal quantile-quantile(Q-Q) plots and shown as a positive-skewed distribution pattern. The Se significantly enriched(EF>10) strata sequences mainly include the lower and upper Doushantuo member II(DST-II), top DST-III, DST-IV, the basal and upper Yanjiahe Formation, and lower and upper Shuijingtuo Formation. Geochemical characteristics indicate that Se concentrations in the significantly enriched strata were generally influenced by terrigenous detrital as well as the combined action of single or multiple factors, such as hydrotherm,volcanic debris and deep source. Moreover, pyrite and organic matter promoted the enrichment of Se in the upper DST-II, DST-IV,upper Shuijingtuo Formation and lower DST-II, upper Shuijingtuo Formation, respectively. The Se concentrations in the not significantly enriched strata(except for DST-I, middle Shuijingtuo Formation, Shipai Formation and lower Tianheban Formation)were also influenced by terrigenous detrital, but other enrichment activities(e.g., hydrothermal, volcanic debris, and deep source)were generally insignificant.展开更多
Based on the comparison of basic geological conditions and enrichment characteristics of shale oil plays, the heterogeneity of source and reservoir conditions and differential enrichment of medium-high maturity contin...Based on the comparison of basic geological conditions and enrichment characteristics of shale oil plays, the heterogeneity of source and reservoir conditions and differential enrichment of medium-high maturity continental shale oil plays in China have been confirmed.(1) Compared with the homogeneous geological settings and wide distribution of marine shale oil strata in North America, the continental medium and high maturity shale oil plays in China are significantly different in geological conditions generally;continental multi-cyclic tectonic evolution forms multiple types of lake basins in multi-stages, providing sites for large-scale development of continental shale oil, and giving rise to large scale high-quality source rocks, multiple types of reservoirs, and diverse source-reservoir combinations with significant heterogeneity.(2) The differences in sedimentary water environments lead to the heterogeneity in lithology, lithofacies, and organic material types of source rocks;the differences in material source supply and sedimentary facies belt result in reservoirs of different lithologies, including argillaceous and transition rocks, and tight siltstone, and complex source-reservoir combination types.(3) The heterogeneity of the source rock controls the differentiation of hydrocarbon generation and expulsion, the diverse reservoir types make reservoir performance different and the source-reservoir configurations complex, and these two factors ultimately make the shale oil enrichment patterns different. Among them, the hydrocarbon generation and expulsion capacity of high-quality source rocks affect the degree of shale oil enrichment. Freshwater hydrocarbon source rocks with TOC larger than 2.5% and saline hydrocarbon source rocks with TOC of 2% to 10% have a high content of retained hydrocarbons and are favorable.(4) High-abundance organic shale is the basis for the enrichment of shale oil inside the source. In addition to being retained in shale, liquid hydrocarbons migrate along laminae, diagenetic fractures, and thin sandy layers, and then accumulate in laminae of argillaceous siltstone, siltstone, and argillaceous dolomite, and dolomitic siltstone suites, etc. with low organic matter abundance in the shale strata, resulting in differences in enrichment pattern.展开更多
基金Supported by the Youth Science Foundation of National Natural Science Foundation of China(41502150)Petro China Science and Technology Project(2023ZZ21YJ04)。
文摘The shale of the Cambrian Qiongzhusi Formation in the Sichuan Basin is characterized by large burial depth and high maturity,but the shale gas enrichment pattern is still unclear.Based on the detailed characterization of Deyang-Anyue aulacogen,analysis of its depositional environments,together with reconstruction of shale gas generation and enrichment evolution against the background of the Leshan-Longnüsi paleouplift,the aulacogen-uplift enrichment pattern was elucidated.It is revealed that the Deyang-Anyue aulacogen controls the depositional environment of the Qiongzhusi Formation,where high-quality sedimentary facies and thick strata are observed.Meanwhile,the Leshan-Longnüsi paleouplift controls the maturity evolution of the shale in the Qiongzhusi Formation,with the uplift located in a high position and exhibiting a moderate degree of thermal evolution and a high resistivity.The aulacogen-uplift overlap area is conducive to the enrichment of shale gas during the deposition,oil generation,gas generation,and oil-gas adjustment stage,which also has a joint control on the development of reservoirs,resulting in multiple reservoirs of high quality and large thickness.Based on the aulacogen-uplift enrichment pattern and combination,four types of shale gas play are identified,and the sweet spot evaluation criteria for the Qiongzhusi Formation is established.Accordingly,a sweet spot area of 8200 km^(2)in the aulacogen is determined,successfully guiding the deployment of Well Zi 201 with a high-yield industrial gas flow of 73.88×10^(4) m^(3)/d.The new geological insights on the aulacogen-uplift enrichment pattern provide a significant theoretical basis for the exploration and breakthrough of deep to ultra-deep Cambrian shale gas,highlighting the promising exploration prospect in this domain.
基金Supported by the National Natural Fund Petrochemical Joint Fund Key Project(U1762217)Fundamental Scientific Research Operations Project of China Central Universities(19CX02009A)
文摘The Chang 73 sub-member of Triassic Yanchang Formation in the Ordos Basin was taken as an example and the lamina types and combinations,reservoir space features and shale oil enrichment patterns in organic-rich shale strata were investigated using core observation,thin section analysis,XRF element measurement,XRD analysis,SEM,high solution laser Raman spectroscopy analysis,and micro-FTIR spectroscopy analysis,etc.According to the mineral composition and thickness of the laminae,the Chang 73 organic-rich shales have four major types of laminae,tuff-rich lamina,organic-rich lamina,silt-grade feldspar-quartz lamina and clay lamina.They have two kinds of shale oil-bearing layers,"organic-rich lamina+silt-grade feldspar-quartz lamina"and"organic-rich lamina+tuff-rich lamina"layers.In the"organic-rich+silt-grade feldspar-quartz"laminae combination shale strata,oil was characterized by relative high maturation,and always filled in K-feldspar dissolution pores in the silt-grade feldspar-quartz laminae,forming oil generation,migration and accumulation process between laminae inside the organic shales.In the"organic-rich+tuff-rich lamina"binary laminae combination shale strata,however,the reservoir properties were poor in organic-rich shales,the oil maturation was relatively lower,and mainly accumulated in the intergranular pores of interbedded thin-layered sandstones.The oil generation,migration and accumulation mainly occurred between organic-rich shales and interbedded thin-layered sandstones.
基金Supported by the National Natural Science Foundation of China for Young Scientists Fund(No.42102158)the Jilin Province Science and Technology Development Plan Project(No.20240101065JC)+2 种基金the project of Education Department of Jilin Provincial(No.JJKH20241292KJ)the Natural Science Foundation of Sichuan Province(No.2024NSFSC0087)Supported by Graduate Innovation Fund of Jilin University(No.2024CX238).
文摘The quest for enrichment model of continental shale oil in the Zhanhua Sag of the JiyangDepression in the Bohai Bay Basin to provide reference for exploration and development requires acomprehensive approach. Therefore, this study employs rock pyrolysis, Scanning Electron Microscopy(SEM), X-Ray diffraction analysis (XRD), Nuclear Magnetic Resonance (NMR), and other experiments toanalyze the conditions for shale oil enrichment and establish its patterns. The results show that favorablehydrocarbon generation potential and appropriate thermal maturation degree control “in situ enrichment”;while the storage capacity and the mobility of shale oil determine “migration enrichment.” In the process,the TOC governs the oil-generating capacity of shale with medium to large pores and microfractures servingas the main enrichment spaces and migration pathways for shale oil. Based on the deposition model, thestudy area can be divided into five lithofacies stages (I-algal limestone, II-laminated marl, III-laminatedrecrystallized limestone, IV-laminated mudstones, and IV-blocky calcareous mudstones). Integrating thegeochemical parameters into the sedimentary patterns makes it clear that the study area underwent two phasesof hydrocarbon expulsion during the thermal evolution of source rocks (Stage II: 3 060–3 120 m and StageIV: 3 020–3 040 m). However, judging by the observed TOC (2% to 5.6%), thermal maturity (Ro>0.8%),S1 (>2 mg/g) and OSI (>100 mg/g) as well as moderate basin size, climate, and quantity of terrestrial input,the blocky calcareous mudstones (Stage IV) have better oil-prone characteristics and potential to generate asubstantial quantity of hydrocarbons at this stage. More so, with a brittleness index exceeding 60%, it exhibitsfavorable fracturability accounting for the main controlling factors and enrichment patterns of shale oil in thearea. Hence, this study further enriches and develops the theoretical understanding of shale oil enrichment inthe area, provides valuable insights for future exploration of continental shale oil in eastern China and othersimilar basin around the world.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41172310 & 41472322)the National Basic Research Program of China (Grant No. 2014CB238906)
文摘The distribution and enrichment patterns of selenium(Se) in the E-?1 strata in the Yangtze Gorges area of South China were obtained. The geochemical characteristics of the significantly and non-significantly enriched strata of Se were analyzed.The observed enrichment factor(EF, relative to the upper continental crust) and concentration coefficient(CC, relative to the similar lithology in Eastern China) both suggest that Se is the most enriched/concentrated(SeEF=26.97, SeCC=48.04) among the analyzed23 trace elements the E-?1 strata. The normalized enrichment factor(EF′, EF after Al or Th normalized) shows Se is secondly enriched(SeEF′=218.73), which is slightly lower than cadmium(CdEF′=288.46) but significantly higher than the third enriched trace element arsenic(AsEF′=97.49). Se concentrations in the E-?1 strata vary from <10.5 to 30.08 ppm with an arithmetic mean value of 1.35 ppm. Compared to the Nantuo Formation, Se increased 11.78 times in the whole E-?1 strata and the average EF values are displayed as Shuijingtuo(92.58)>Yanjiahe(54.45)>Doushantuo(24.72)>Dengying(2.48)>Shipai(1.95)>lower Tianheban(1.24)Formations. Se concentrations in the E-?1 strata are best displayed on natural logarithm normal quantile-quantile(Q-Q) plots and shown as a positive-skewed distribution pattern. The Se significantly enriched(EF>10) strata sequences mainly include the lower and upper Doushantuo member II(DST-II), top DST-III, DST-IV, the basal and upper Yanjiahe Formation, and lower and upper Shuijingtuo Formation. Geochemical characteristics indicate that Se concentrations in the significantly enriched strata were generally influenced by terrigenous detrital as well as the combined action of single or multiple factors, such as hydrotherm,volcanic debris and deep source. Moreover, pyrite and organic matter promoted the enrichment of Se in the upper DST-II, DST-IV,upper Shuijingtuo Formation and lower DST-II, upper Shuijingtuo Formation, respectively. The Se concentrations in the not significantly enriched strata(except for DST-I, middle Shuijingtuo Formation, Shipai Formation and lower Tianheban Formation)were also influenced by terrigenous detrital, but other enrichment activities(e.g., hydrothermal, volcanic debris, and deep source)were generally insignificant.
基金Supported by the National Natural Science Foundation of China (42072186)China National Oil and Gas Major Project (2016ZX05046-001)PetroChina Scientific Research and Technology Project (2021-DJ2203)。
文摘Based on the comparison of basic geological conditions and enrichment characteristics of shale oil plays, the heterogeneity of source and reservoir conditions and differential enrichment of medium-high maturity continental shale oil plays in China have been confirmed.(1) Compared with the homogeneous geological settings and wide distribution of marine shale oil strata in North America, the continental medium and high maturity shale oil plays in China are significantly different in geological conditions generally;continental multi-cyclic tectonic evolution forms multiple types of lake basins in multi-stages, providing sites for large-scale development of continental shale oil, and giving rise to large scale high-quality source rocks, multiple types of reservoirs, and diverse source-reservoir combinations with significant heterogeneity.(2) The differences in sedimentary water environments lead to the heterogeneity in lithology, lithofacies, and organic material types of source rocks;the differences in material source supply and sedimentary facies belt result in reservoirs of different lithologies, including argillaceous and transition rocks, and tight siltstone, and complex source-reservoir combination types.(3) The heterogeneity of the source rock controls the differentiation of hydrocarbon generation and expulsion, the diverse reservoir types make reservoir performance different and the source-reservoir configurations complex, and these two factors ultimately make the shale oil enrichment patterns different. Among them, the hydrocarbon generation and expulsion capacity of high-quality source rocks affect the degree of shale oil enrichment. Freshwater hydrocarbon source rocks with TOC larger than 2.5% and saline hydrocarbon source rocks with TOC of 2% to 10% have a high content of retained hydrocarbons and are favorable.(4) High-abundance organic shale is the basis for the enrichment of shale oil inside the source. In addition to being retained in shale, liquid hydrocarbons migrate along laminae, diagenetic fractures, and thin sandy layers, and then accumulate in laminae of argillaceous siltstone, siltstone, and argillaceous dolomite, and dolomitic siltstone suites, etc. with low organic matter abundance in the shale strata, resulting in differences in enrichment pattern.
