The characteristics, formation mechanisms, and influences on physical properties of carbonate minerals in shale reservoirs of Wufeng-Longmaxi formations in Sichuan Basin are systematically investigated by utilizing electron probe microscope with spectrometer and energy spectrometer, combined with physical properties and whole rock X-diffraction and organic carbon data. The research yielded the findings that follow: First, the main carbonate minerals are calcite, dolomite, and ferriferous dolomite. Calcite is a single mineral that fills the siliceous shell cavity of radiolarians and exists between mineral particles. Ferriferous dolomite always rings dolomite, which is a single mineral that is present among mineral particles and aggregates. Second, calcite is produced by microorganisms that secrete calcium carbonate in the surface of seawater. The siliceous skeleton cavity of radiolarian and seawater both precipitate calcite, which partially dissolves while settling in seawater before depositing on the seabed and being preserved by burial. Thirdly, the dolomite is a diagenetic mineral formed on the water–sediment interface with physiological activities of sulfate bacteria, and the ferriferous dolomite is produced by methanogenic metabolism during the initial burial of muddy sediments. Fourthly, organic carbon, pyrite, quartz, and clay minerals are closely related to reservoir physical properties, while carbonate has no effect on porosity and permeability as a whole. Future research on shale reservoir diagenesis should make use of the in-situ detection and element area scanning, in particular with the spectrogram from electron probe microscope technology, which provides typical petrological evidences for the study of characteristics, formation mechanism, and influence on physical properties of carbonate minerals in shale reservoirs.
{"title":"Characteristics, formation mechanism and influence on physical properties of carbonate minerals in shale reservoirs of Wufeng-Longmaxi formations, Sichuan Basin, China","authors":"Xiaofeng Zhou , Xizhe Li , Wei Guo , Xiaowei Zhang , Pingping Liang , Junmin Yu","doi":"10.1016/j.jnggs.2022.07.001","DOIUrl":"https://doi.org/10.1016/j.jnggs.2022.07.001","url":null,"abstract":"<div><p>The characteristics, formation mechanisms, and influences on physical properties of carbonate minerals in shale reservoirs of Wufeng-Longmaxi formations in Sichuan Basin are systematically investigated by utilizing electron probe microscope with spectrometer and energy spectrometer, combined with physical properties and whole rock X-diffraction and organic carbon data. The research yielded the findings that follow: First, the main carbonate minerals are calcite, dolomite, and ferriferous dolomite. Calcite is a single mineral that fills the siliceous shell cavity of radiolarians and exists between mineral particles. Ferriferous dolomite always rings dolomite, which is a single mineral that is present among mineral particles and aggregates. Second, calcite is produced by microorganisms that secrete calcium carbonate in the surface of seawater. The siliceous skeleton cavity of radiolarian and seawater both precipitate calcite, which partially dissolves while settling in seawater before depositing on the seabed and being preserved by burial. Thirdly, the dolomite is a diagenetic mineral formed on the water–sediment interface with physiological activities of sulfate bacteria, and the ferriferous dolomite is produced by methanogenic metabolism during the initial burial of muddy sediments. Fourthly, organic carbon, pyrite, quartz, and clay minerals are closely related to reservoir physical properties, while carbonate has no effect on porosity and permeability as a whole. Future research on shale reservoir diagenesis should make use of the in-situ detection and element area scanning, in particular with the spectrogram from electron probe microscope technology, which provides typical petrological evidences for the study of characteristics, formation mechanism, and influence on physical properties of carbonate minerals in shale reservoirs.</p></div>","PeriodicalId":100808,"journal":{"name":"Journal of Natural Gas Geoscience","volume":"7 3","pages":"Pages 133-146"},"PeriodicalIF":0.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2468256X22000311/pdfft?md5=e16b8a7e22b1e3eac8919e06b1eb6032&pid=1-s2.0-S2468256X22000311-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72246394","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Micro-pore structure and fractal characteristics of deep shale from Wufeng Formation to Longmaxi Formation in Jingmen exploration area, Hubei Province, China","authors":"Xiaoming Li, Yarong Wang, Wen Lin, Lihong Ma, Dexun Liu, Jirong Liu, Yu Zhang","doi":"10.1016/j.jnggs.2022.06.001","DOIUrl":"https://doi.org/10.1016/j.jnggs.2022.06.001","url":null,"abstract":"","PeriodicalId":100808,"journal":{"name":"Journal of Natural Gas Geoscience","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82414979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-06-01DOI: 10.1016/j.jnggs.2022.06.004
Qin Zhang , Zhen Qiu , Leifu Zhang , Yuman Wang , Yufeng Xiao , Dan Liu , Wen Liu , Shuxin Li , Xingtao Li
The shales in the 2nd Member of Permian Shanxi Formation (Shan2 Member) at the Daning-Jixian block at the eastern margin of the Ordos Basin were deposited in a marine–continental transitional environment. The Shan23 sub-member, which is the target interval for transitional shale gas exploration and development in China, is characterized by substantial shale thickness, few and thin interlayers. This interval, however, has been rarely investigated for reservoir characteristics, especially the controlling factors of high-quality reservoirs. In this paper, the reservoir characteristics and main controlling factors of high-quality reservoirs in Shan23 in the Daning-Jixian block were systematically discussed by organic geochemical analysis, mineral compositional analysis, and microscopic reservoir characterization. The results indicate that the lagoon facies shale interval in the upper part of the Shan23 sub-member has a high total organic carbon (TOC) content, a high brittle mineral content, and high BET surface area and BJH pore volume values, indicating that this is the sweet spot for shale gas exploration and development. Pore space in the Shan23 sub-member shale is dominated by clay mineral intercrystalline pores (76.9%), which also contains organic matter pores (18.7%). The SEM observations reveal that the mineral components are different in pore size distribution (PSD) and the organic matter pores and calcite dissolved pores are mainly in meso-scale, the pores in clay minerals and quartz are in meso- and macro-scale, while the pores in feldspar and pyrite exhibit a wide and uniform size distribution. The single-factor analysis shows that the clay mineral content is the dominant factor controlling pore development in the Shan23 sub-member transitional shales, the TOC content has a certain effect on pore development, and the kerogen type has no discernible effect on pore development.
{"title":"Characteristics and controlling factors of transitional shale gas reservoirs: An example from Permian Shanxi Formation, Daning-Jixian block, Ordos Basin, China","authors":"Qin Zhang , Zhen Qiu , Leifu Zhang , Yuman Wang , Yufeng Xiao , Dan Liu , Wen Liu , Shuxin Li , Xingtao Li","doi":"10.1016/j.jnggs.2022.06.004","DOIUrl":"https://doi.org/10.1016/j.jnggs.2022.06.004","url":null,"abstract":"<div><p>The shales in the 2<sup>nd</sup> Member of Permian Shanxi Formation (Shan2 Member) at the Daning-Jixian block at the eastern margin of the Ordos Basin were deposited in a marine–continental transitional environment. The Shan<sub>2</sub><sup>3</sup> sub-member, which is the target interval for transitional shale gas exploration and development in China, is characterized by substantial shale thickness, few and thin interlayers. This interval, however, has been rarely investigated for reservoir characteristics, especially the controlling factors of high-quality reservoirs. In this paper, the reservoir characteristics and main controlling factors of high-quality reservoirs in Shan<sub>2</sub><sup>3</sup> in the Daning-Jixian block were systematically discussed by organic geochemical analysis, mineral compositional analysis, and microscopic reservoir characterization. The results indicate that the lagoon facies shale interval in the upper part of the Shan<sub>2</sub><sup>3</sup> sub-member has a high total organic carbon (TOC) content, a high brittle mineral content, and high BET surface area and BJH pore volume values, indicating that this is the sweet spot for shale gas exploration and development. Pore space in the Shan<sub>2</sub><sup>3</sup> sub-member shale is dominated by clay mineral intercrystalline pores (76.9%), which also contains organic matter pores (18.7%). The SEM observations reveal that the mineral components are different in pore size distribution (PSD) and the organic matter pores and calcite dissolved pores are mainly in meso-scale, the pores in clay minerals and quartz are in meso- and macro-scale, while the pores in feldspar and pyrite exhibit a wide and uniform size distribution. The single-factor analysis shows that the clay mineral content is the dominant factor controlling pore development in the Shan<sub>2</sub><sup>3</sup> sub-member transitional shales, the TOC content has a certain effect on pore development, and the kerogen type has no discernible effect on pore development.</p></div>","PeriodicalId":100808,"journal":{"name":"Journal of Natural Gas Geoscience","volume":"7 3","pages":"Pages 147-157"},"PeriodicalIF":0.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2468256X2200030X/pdfft?md5=9e40625180a2ad7e8d57fec99f85dce4&pid=1-s2.0-S2468256X2200030X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72246396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-06-01DOI: 10.1016/j.jnggs.2022.06.003
Lei Yan , Guoqi Wei , Guangyou Zhu , Yongquan Chen , Caiming Luo , Min Yang , Shan Wang , Dedao Du
Carbonate rock from the Late Proterozoic to the Early Paleozoic is an important field of oil and gas exploration. The Sinian carbonate rock series in Tarim Basin are old, deep buried, with few drilling wells and various geological problems are unclear that restrict the exploration of deep carbonate rock. Based on the analysis of Sinian geological structure, by means of stratigraphic correlation and seismic prediction, the distribution of Sinian favorable source rocks, deep reservoir facies belts, and reservoir forming assemblages are studied to comb the exploration fields and favorable zones of Sinian in Tarim Basin. The findings reveal that slope-basin facies source rocks developed in Sinian. In the upper part of the Qigebulake Formation, high-quality dolomite reservoirs evolved, and mudstone from the Yuertus Formation at the foot of Cambrian can form favorable reservoir cap assemblage. The south slope of Tabei Uplift and the north slope of Tazhong Uplift are the most favorable exploration zones for Sinian dolomite, favorable exploration area of approximately 31,000 km2. The findings can provide a certain reference for the Sinian carbonate oil and gas exploration in the Tarim Basin.
{"title":"Exploration field analysis and zone optimization of sinian, Tarim Basin, China","authors":"Lei Yan , Guoqi Wei , Guangyou Zhu , Yongquan Chen , Caiming Luo , Min Yang , Shan Wang , Dedao Du","doi":"10.1016/j.jnggs.2022.06.003","DOIUrl":"https://doi.org/10.1016/j.jnggs.2022.06.003","url":null,"abstract":"<div><p>Carbonate rock from the Late Proterozoic to the Early Paleozoic is an important field of oil and gas exploration. The Sinian carbonate rock series in Tarim Basin are old, deep buried, with few drilling wells and various geological problems are unclear that restrict the exploration of deep carbonate rock. Based on the analysis of Sinian geological structure, by means of stratigraphic correlation and seismic prediction, the distribution of Sinian favorable source rocks, deep reservoir facies belts, and reservoir forming assemblages are studied to comb the exploration fields and favorable zones of Sinian in Tarim Basin. The findings reveal that slope-basin facies source rocks developed in Sinian. In the upper part of the Qigebulake Formation, high-quality dolomite reservoirs evolved, and mudstone from the Yuertus Formation at the foot of Cambrian can form favorable reservoir cap assemblage. The south slope of Tabei Uplift and the north slope of Tazhong Uplift are the most favorable exploration zones for Sinian dolomite, favorable exploration area of approximately 31,000 km<sup>2</sup>. The findings can provide a certain reference for the Sinian carbonate oil and gas exploration in the Tarim Basin.</p></div>","PeriodicalId":100808,"journal":{"name":"Journal of Natural Gas Geoscience","volume":"7 3","pages":"Pages 171-179"},"PeriodicalIF":0.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2468256X22000293/pdfft?md5=0499eea96cea9f5aceb37e30db6bb82b&pid=1-s2.0-S2468256X22000293-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72245916","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-06-01DOI: 10.1016/j.jnggs.2022.06.001
Xiaoming Li , Yarong Wang , Wen Lin , Lihong Ma , Dexun Liu , Jirong Liu , Yu Zhang
To explore the pore structure and fractal characteristics of shale reservoirs in the Jingmen exploration area and quantitatively evaluate the heterogeneity and complexity of pores, taking Wufeng-Longmaxi formations of Well YT3 as the research object, the pore structure characteristics of shale reservoirs are analyzed by low-pressure nitrogen adsorption experiments, total organic carbon (TOC) content testing, X-ray diffraction analysis, etc., and the FHH fractal model is established based on the low-temperature nitrogen adsorption fractal geometry method. The relationship between fractal dimension and shale composition, pore structure, physical property, gas-bearing property, and burial depth is discussed. The results show that (1) The lower section of Longmaxi Formation and Wufeng Formation have significantly higher TOC concentrations than the upper section of Longmaxi Formation. With the increase of burial depth, the silicate minerals increase gradually, while clay minerals decrease. (2) The on-site desorption gas content of shale shows that the gas content of the upper section of Longmaxi Formation with low TOC abundance is lower than the lower section of Longmaxi Formation and Wufeng Formation. In terms of shale gas composition, nitrogen dominates the upper section of Longmaxi Formation, whereas methane dominates the Wufeng Formation and lower section of Longmaxi Formation. (3) The isothermal curve of shale under low-pressure nitrogen is identical to IUPAC type IV, while the adsorption hysteresis loop is similar to types H3 and H4. The pores are mainly micro medium pores distributed below 50 nm, and they are flat and slit. The lower section of Longmaxi Formation and Wufeng Formation have significantly larger adsorption volumes than the upper section of Longmaxi Formation, and the abundance of organic matter provides a large amount of organic pore storage space. (4) The BET specific surface area and BJH total pore volume in the lower section of Longmaxi Formation and Wufeng Formation with rich organic matter are significantly larger than in the upper section of Longmaxi Formation with low organic matter, whereas the average pore size is significantly smaller. (5) Shale pores have obvious fractal characteristics, with D2 being higher than D1, indicating that the pore structure is more complicated than that of the pore surface. Fractal dimension has a significant positive correlation with TOC content, BET-specific surface area, and burial depth, a weak positive correlation with quartz content and BJH total pore volume, a significant negative correlation with clay mineral content and average pore diameter, and almost no correlation with porosity and permeability. Many factors that affect the fractal dimension. Correlation analysis reveals that the mass fraction of TOC and clay mineral, specific surface area, average pore diameter, and burial depth are the main controlling factor
{"title":"Micro-pore structure and fractal characteristics of deep shale from Wufeng Formation to Longmaxi Formation in Jingmen exploration area, Hubei Province, China","authors":"Xiaoming Li , Yarong Wang , Wen Lin , Lihong Ma , Dexun Liu , Jirong Liu , Yu Zhang","doi":"10.1016/j.jnggs.2022.06.001","DOIUrl":"https://doi.org/10.1016/j.jnggs.2022.06.001","url":null,"abstract":"<div><p>To explore the pore structure and fractal characteristics of shale reservoirs in the Jingmen exploration area and quantitatively evaluate the heterogeneity and complexity of pores, taking Wufeng-Longmaxi formations of Well YT3 as the research object, the pore structure characteristics of shale reservoirs are analyzed by low-pressure nitrogen adsorption experiments, total organic carbon (TOC) content testing, X-ray diffraction analysis, etc., and the FHH fractal model is established based on the low-temperature nitrogen adsorption fractal geometry method. The relationship between fractal dimension and shale composition, pore structure, physical property, gas-bearing property, and burial depth is discussed. The results show that (1) The lower section of Longmaxi Formation and Wufeng Formation have significantly higher TOC concentrations than the upper section of Longmaxi Formation. With the increase of burial depth, the silicate minerals increase gradually, while clay minerals decrease. (2) The on-site desorption gas content of shale shows that the gas content of the upper section of Longmaxi Formation with low TOC abundance is lower than the lower section of Longmaxi Formation and Wufeng Formation. In terms of shale gas composition, nitrogen dominates the upper section of Longmaxi Formation, whereas methane dominates the Wufeng Formation and lower section of Longmaxi Formation. (3) The isothermal curve of shale under low-pressure nitrogen is identical to IUPAC type IV, while the adsorption hysteresis loop is similar to types H<sub>3</sub> and H<sub>4</sub>. The pores are mainly micro medium pores distributed below 50 nm, and they are flat and slit. The lower section of Longmaxi Formation and Wufeng Formation have significantly larger adsorption volumes than the upper section of Longmaxi Formation, and the abundance of organic matter provides a large amount of organic pore storage space. (4) The BET specific surface area and BJH total pore volume in the lower section of Longmaxi Formation and Wufeng Formation with rich organic matter are significantly larger than in the upper section of Longmaxi Formation with low organic matter, whereas the average pore size is significantly smaller. (5) Shale pores have obvious fractal characteristics, with <em>D</em><sub>2</sub> being higher than <em>D</em><sub>1</sub>, indicating that the pore structure is more complicated than that of the pore surface. Fractal dimension has a significant positive correlation with TOC content, BET-specific surface area, and burial depth, a weak positive correlation with quartz content and BJH total pore volume, a significant negative correlation with clay mineral content and average pore diameter, and almost no correlation with porosity and permeability. Many factors that affect the fractal dimension. Correlation analysis reveals that the mass fraction of TOC and clay mineral, specific surface area, average pore diameter, and burial depth are the main controlling factor","PeriodicalId":100808,"journal":{"name":"Journal of Natural Gas Geoscience","volume":"7 3","pages":"Pages 121-132"},"PeriodicalIF":0.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2468256X2200027X/pdfft?md5=7d5089eb7569497737380cc238d6197c&pid=1-s2.0-S2468256X2200027X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72245917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-01DOI: 10.1016/j.jnggs.2022.04.002
Ke Xu , Jun Tian , Haijun Yang , Hui Zhang , Wei Ju , Xinyu Liu , Zhimin Wang , Lu Fang
There is a significant relationship between in-situ stress and reservoir quality, to reinvent the theoretical understanding and technical methods of reservoir evaluation from the perspective of in-situ stress. Based on rock mechanical test and logging data, combined with regional evolution and structural deformation, this study carried out systematic geomechanics research, proposing the quantitative characterization of stress concentration parameters to realize the optimization of favorable zones. The results show that in-situ stress and fracture permeability under its control are important factors in determining the productivity in the ultra-deep reservoir. It is preferable to choose a location with low stress and good fracture activity, rather than an adverse location such as a local stress concentration area characterized by frequent borehole breakouts. The imbalance between in-situ stress and rock strength causes high stress. Moreover, the accuracy of reservoir classification is improved by incorporating the relevant parameters under the influence of in-situ stress into the evaluation method of reservoir quality. It is vital to fully utilize the multiple advantages of highly deviated wells with various favorable areas and multiple vertical fractures to address complex problems and improve the efficiency of exploration and development.
{"title":"Effects and practical applications of present-day in-situ stress on reservoir quality in ultra-deep layers of Kuqa Depression, Tarim Basin, China","authors":"Ke Xu , Jun Tian , Haijun Yang , Hui Zhang , Wei Ju , Xinyu Liu , Zhimin Wang , Lu Fang","doi":"10.1016/j.jnggs.2022.04.002","DOIUrl":"https://doi.org/10.1016/j.jnggs.2022.04.002","url":null,"abstract":"<div><p>There is a significant relationship between in-situ stress and reservoir quality, to reinvent the theoretical understanding and technical methods of reservoir evaluation from the perspective of in-situ stress. Based on rock mechanical test and logging data, combined with regional evolution and structural deformation, this study carried out systematic geomechanics research, proposing the quantitative characterization of stress concentration parameters to realize the optimization of favorable zones. The results show that in-situ stress and fracture permeability under its control are important factors in determining the productivity in the ultra-deep reservoir. It is preferable to choose a location with low stress and good fracture activity, rather than an adverse location such as a local stress concentration area characterized by frequent borehole breakouts. The imbalance between in-situ stress and rock strength causes high stress. Moreover, the accuracy of reservoir classification is improved by incorporating the relevant parameters under the influence of in-situ stress into the evaluation method of reservoir quality. It is vital to fully utilize the multiple advantages of highly deviated wells with various favorable areas and multiple vertical fractures to address complex problems and improve the efficiency of exploration and development.</p></div>","PeriodicalId":100808,"journal":{"name":"Journal of Natural Gas Geoscience","volume":"7 2","pages":"Pages 85-94"},"PeriodicalIF":0.0,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2468256X22000074/pdfft?md5=7364477c2583d7eff55847dbe00592c9&pid=1-s2.0-S2468256X22000074-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"137392206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-01DOI: 10.1016/j.jnggs.2022.04.004
Ziyun Zhang, Lianhua Hou, Xia Luo, Kun He, Yan Zhang
In-situ conversion technology has been more popular lately as an effective way to realize the industrial development of extensive medium- and low-mature shale oil/oil shale resources in China. The Ordos Basin has been recognized as the main basin containing the largest in-situ conversion recoverable resources of China. Researchers have revealed the hydrocarbon generation kinetics of low mature oil shales in the 7th Member of the Yanchang Formation (Chang 7 Member). However, the kinetics of medium mature shales may be different from those of low mature shales, and they can also be used as potential targets for in-situ conversion. At present, there is a lack of research on the in-situ hydrocarbon generation kinetics of medium- and low-mature shale oil/oil shale. In this paper, open system pyrolysis experiments were carried out on natural shales and shale samples derived from semi-open system pyrolysis with different maturities in the Chang 7 Member of the Ordos Basin respectively. Using the parallel first-order reaction theory, the frequency factor of low-mature shale was calculated to be 5.47 × 1010 s−1, and the distribution of activation energy ranged from 38 kcal/mol to 61 kcal/mol. The main peak of activation energy was 49 kcal/mol, and accounted for 66.91% of all shales. With the increase in maturity, the average activation energy becomes higher, and therefore more in-situ conversion energy is needed. At the same time, the hydrocarbon generation potential characterized by S2 peak of pyrolysis decreases during the maturation process. The activation energy is divided into three groups according to its distribution characteristics: low, main peak and high activation energy groups, representing <47 kcal/mol, ranging from 47 kcal/mol to 52 kcal/mol and >52 kcal/mol respectively. The proportion of low and high activation energy groups increased with the increase in maturity, while the proportion of main peak activation energy groups decreased. When the kinetic parameters are extrapolated to the condition of in-situ conversion, it is better to choose shales with low maturity (RO <1 .0%) and fully transform them by rapid heating to the main hydrocarbon generation stage, and different conversion temperature ranges should be set for different maturity samples.
{"title":"Hydrocarbon generation kinetics and in-situ conversion temperature conditions of Chang 7 Member shale in the Ordos Basin, China","authors":"Ziyun Zhang, Lianhua Hou, Xia Luo, Kun He, Yan Zhang","doi":"10.1016/j.jnggs.2022.04.004","DOIUrl":"10.1016/j.jnggs.2022.04.004","url":null,"abstract":"<div><p><em>In-situ</em> conversion technology has been more popular lately as an effective way to realize the industrial development of extensive medium- and low-mature shale oil/oil shale resources in China. The Ordos Basin has been recognized as the main basin containing the largest <em>in-situ</em> conversion recoverable resources of China. Researchers have revealed the hydrocarbon generation kinetics of low mature oil shales in the 7th Member of the Yanchang Formation (Chang 7 Member). However, the kinetics of medium mature shales may be different from those of low mature shales, and they can also be used as potential targets for <em>in-situ</em> conversion. At present, there is a lack of research on the <em>in-situ</em> hydrocarbon generation kinetics of medium- and low-mature shale oil/oil shale. In this paper, open system pyrolysis experiments were carried out on natural shales and shale samples derived from semi-open system pyrolysis with different maturities in the Chang 7 Member of the Ordos Basin respectively. Using the parallel first-order reaction theory, the frequency factor of low-mature shale was calculated to be 5.47 × 10<sup>10</sup> s<sup>−1</sup>, and the distribution of activation energy ranged from 38 kcal/mol to 61 kcal/mol. The main peak of activation energy was 49 kcal/mol, and accounted for 66.91% of all shales. With the increase in maturity, the average activation energy becomes higher, and therefore more <em>in-situ</em> conversion energy is needed. At the same time, the hydrocarbon generation potential characterized by <em>S</em><sub>2</sub> peak of pyrolysis decreases during the maturation process. The activation energy is divided into three groups according to its distribution characteristics: low, main peak and high activation energy groups, representing <47 kcal/mol, ranging from 47 kcal/mol to 52 kcal/mol and >52 kcal/mol respectively. The proportion of low and high activation energy groups increased with the increase in maturity, while the proportion of main peak activation energy groups decreased. When the kinetic parameters are extrapolated to the condition of <em>in-situ</em> conversion, it is better to choose shales with low maturity (<em>R</em><sub>O</sub> <1 .0%) and fully transform them by rapid heating to the main hydrocarbon generation stage, and different conversion temperature ranges should be set for different maturity samples.</p></div>","PeriodicalId":100808,"journal":{"name":"Journal of Natural Gas Geoscience","volume":"7 2","pages":"Pages 111-119"},"PeriodicalIF":0.0,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2468256X22000177/pdfft?md5=8cf7c308d1b079ea27f0f78b480ebfb3&pid=1-s2.0-S2468256X22000177-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77934443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-01DOI: 10.1016/j.jnggs.2022.04.001
Xuewen Shi , Wei Wu , Shangwen Zhou , Chong Tian , Du Li , Dingyuan Li , Yi Li , Changhong Cai , Yulong Chen
Deep shale gas (3500–4500 m) is the important replacement field of shale gas production growth in the future China. The research on key parameters of deep shale-gas reservoir is critical to determine its basic geological characteristics and establish a suitable development mode. In order to clarify the adsorption characteristics and controlling factors of deep shale gas in Longmaxi Formation, the main tests such as high-pressure methane adsorption, low-temperature nitrogen and carbon dioxide adsorption coupled with the adsorption fitting model and comparative analysis were conducted. The results show that the adsorption isotherms of deep shale gas also have a downward trend in spite of the higher pressure, and there is no obvious difference in adsorption characteristics, which is mainly due to the similar characteristics of microscopic pore-structure between deep shale and shallower shale. It is found that different adsorption models can well fit the experimental adsorption curve of deep shale gas, but the absolute adsorption capacity converted from excess adsorption capacity shows the same fitting result, i.e., DA-LF model > DR model > Langmuir model. Furthermore, DR model based on micropore filling theory is more suitable for characterizing the adsorption law of deep shale gas combined with the correlation analysis between pore structure and adsorbed-gas capacity. In addition, TOC is the key material factor controlling the adsorption capacity, and specific surface area of micropore is the key spatial factor. Compared to shallower shale, the deep shale shows higher siliceous content, lower calcite content, lower TOC content and lower adsorbed-gas content (the proportion of adsorbed-gas is about 30%).
{"title":"Adsorption characteristics and controlling factors of marine deep shale gas in southern Sichuan Basin, China","authors":"Xuewen Shi , Wei Wu , Shangwen Zhou , Chong Tian , Du Li , Dingyuan Li , Yi Li , Changhong Cai , Yulong Chen","doi":"10.1016/j.jnggs.2022.04.001","DOIUrl":"10.1016/j.jnggs.2022.04.001","url":null,"abstract":"<div><p>Deep shale gas (3500–4500 m) is the important replacement field of shale gas production growth in the future China. The research on key parameters of deep shale-gas reservoir is critical to determine its basic geological characteristics and establish a suitable development mode. In order to clarify the adsorption characteristics and controlling factors of deep shale gas in Longmaxi Formation, the main tests such as high-pressure methane adsorption, low-temperature nitrogen and carbon dioxide adsorption coupled with the adsorption fitting model and comparative analysis were conducted. The results show that the adsorption isotherms of deep shale gas also have a downward trend in spite of the higher pressure, and there is no obvious difference in adsorption characteristics, which is mainly due to the similar characteristics of microscopic pore-structure between deep shale and shallower shale. It is found that different adsorption models can well fit the experimental adsorption curve of deep shale gas, but the absolute adsorption capacity converted from excess adsorption capacity shows the same fitting result, i.e., DA-LF model > DR model > Langmuir model. Furthermore, DR model based on micropore filling theory is more suitable for characterizing the adsorption law of deep shale gas combined with the correlation analysis between pore structure and adsorbed-gas capacity. In addition, TOC is the key material factor controlling the adsorption capacity, and specific surface area of micropore is the key spatial factor. Compared to shallower shale, the deep shale shows higher siliceous content, lower calcite content, lower TOC content and lower adsorbed-gas content (the proportion of adsorbed-gas is about 30%).</p></div>","PeriodicalId":100808,"journal":{"name":"Journal of Natural Gas Geoscience","volume":"7 2","pages":"Pages 61-72"},"PeriodicalIF":0.0,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2468256X22000062/pdfft?md5=0293c550db33f379afedaba766569cc9&pid=1-s2.0-S2468256X22000062-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89391121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Study on temperature distribution prediction of horizontal wells during fracturing treatment","authors":"Haitao Li, Yuxing Xiang, Hongwen Luo, Hao Yu, Q. Zhang, Ying Li, Beibei Jiang, Naiyan Zhang","doi":"10.1016/j.jnggs.2022.03.004","DOIUrl":"https://doi.org/10.1016/j.jnggs.2022.03.004","url":null,"abstract":"","PeriodicalId":100808,"journal":{"name":"Journal of Natural Gas Geoscience","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79506884","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-01DOI: 10.1016/j.jnggs.2022.03.003
Shutong Li, Shixiang Li, Jiangyan Liu, Mingyi Yang, Junlin Chen, Shanshan Zhang, D. Cui, Jiacheng Li
{"title":"Some issues and thoughts on the study of pure shale-type shale oil in the 7th Member of Yanchang Formation in Ordos Basin, China","authors":"Shutong Li, Shixiang Li, Jiangyan Liu, Mingyi Yang, Junlin Chen, Shanshan Zhang, D. Cui, Jiacheng Li","doi":"10.1016/j.jnggs.2022.03.003","DOIUrl":"https://doi.org/10.1016/j.jnggs.2022.03.003","url":null,"abstract":"","PeriodicalId":100808,"journal":{"name":"Journal of Natural Gas Geoscience","volume":"99 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74179760","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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