Shale gas resources have been regarded as a viable energy source, and it is of great significance to characterize the shale composition of different cements, such as quartz and dolomite. In this research, chemical ana...Shale gas resources have been regarded as a viable energy source, and it is of great significance to characterize the shale composition of different cements, such as quartz and dolomite. In this research, chemical analysis and the multifractal method have been used to study the mineral compositions and petrophysical structures of cements in shale samples from the Longmaxi Formation, China. X-ray diffraction, electron microprobe, field emission scanning electron microscopy, cathodoluminescence microscopy and C-O isotope analyses confirmed that cements in the Longmaxi Formation shales are mainly composed of Fe-bearing dolomite and quartz. Fe-bearing dolomite cements concentrate around dolomite as annuli, filling micron-sized inorganic primary pores. Quartz cements in the form of nanoparicles fill primary inter-crystalline pores among clay minerals. Theoretical calculation shows that the Fe-bearing dolomite cements formed slightly earlier than the quartz cements, but both were related to diagenetic illitization of smectite. Moreover, multifractal analysis reveals that the quartz cements are more irregularly distributed in pores than the Fe-bearing dolomite cements. These results suggest that the plugging effect of the quartz cements on the primary inoraganic pore structures is the dominant factor resulting in low interconnected porosity of shales, which are unfavorable for the enrichment of shale gas.展开更多
Ziyang County, Shaanxi Province, China is a world known selenium（Se）-enriched area, and a severe selenosis incident was reported in Naore Village during the 1990 s. This study investigated the geochemical characteri...Ziyang County, Shaanxi Province, China is a world known selenium（Se）-enriched area, and a severe selenosis incident was reported in Naore Village during the 1990 s. This study investigated the geochemical characteristics of Se and its fractions in Se-enriched rocks from Ziyang. Se distribution is uneven, ranging from 0.23 to 57.00 μg/g（17.29±15.52 μg/g）. Se content is higher in slate than chert, and even lower in carbonate rocks. Cd, As and V are enriched but Pb is depleted in Se-enriched strata. Se has different correlations both with TS（total sulfur）（R^2=0.59 for chert） and TC（total carbon）（R^2=0.77 for slate, R^2=0.87 for carbonate）. Se has significant positive correlations with V（r=0.65）, As（r=0.485）, Cd（r=0.459） and Pb（r=0.405）. The Se level correlates with mineral content, positively with pyrite, chlorite and illite, negatively with albite. Se associated with sulfide/selenide and elemental Se are the predominant fractions of total recovered Se, suggesting that a reducing environment and the formation of sulfides were significant to Se deposition during its geochemical cycle. Although low concentration of bio-available Se（average 5.62%±3.69%） may reduce the risk of Se poisoning in the target area, utilization of Se-rich rock as natural fertilizer should be restricted.展开更多
The aim of this study is to quantify the geochemical elements distribution patterns analyzed from stream sediment data and then to delineate favorable areas for mineral exploration. A total of 7 270 stream sediment sa...The aim of this study is to quantify the geochemical elements distribution patterns analyzed from stream sediment data and then to delineate favorable areas for mineral exploration. A total of 7 270 stream sediment samples were collected from four subareas and 37 rock（ore） chip samples from five different locations in the Bange region, northern Tibet（China）. The multifractal spectra of 12 elements including Au, Ag, As, Cu, Mo, Pb, Zn, W, Sn, Bi, Sb and Hg are represented by the method of moments, and characterized by five quantitative multifractal parameters. The results show that the multifractality for Cu and Bi in the Gongma area is much stronger than those in other subareas. Both the asymmetry index of multifractal spectra and the variance coefficients of Cu and Bi in this area are the highest, which imply that the distribution pattern of Cu and Bi in the Gongma area is the most heterogeneous. These multifractal parameters indicate that the Gongma area is the most favorable for prospecting Cu and Bi. The results obtained by the method of moments are in agreement with petrochemical analysis and field observation. It is suggested that multifractal analysis can be used as an effective tool to evaluate the ore-forming potential in the study area and to provide new approaches for geochemical exploration.展开更多
The microscopic pore structure of sand-conglomerate rocks plays a decisive role in its exploration and development of such reservoirs.Due to complex gravels-cements configurations and resultant high heterogeneity in s...The microscopic pore structure of sand-conglomerate rocks plays a decisive role in its exploration and development of such reservoirs.Due to complex gravels-cements configurations and resultant high heterogeneity in sand-conglomerate rocks,the conventional fractal dimensions are inadequate to fully characterize the pore space.Based on the Pia Intermingled Fractal Units(IFU)model,this paper presents a new variable-ratio factor IFU model,which takes tortuosity and boundary layer thickness into consideration,to characterize the Triassic Karamay Formation conglomerate reservoirs in the Mahu region of the Junggar Basin,Northwest China.The modified model has a more powerful and flexible ability to simulate pore structures of porous media,and the simulation results are closer to the real conditions of pore space in low-porosity and low-permeability reservoirs than the conventional Pia IFU model.The geometric construction of the model is simplified to allow for an easing of computation.Porosity and spectral distribution of pore diameter,constructed using the modified model,are generally consistent with actual core data.Also,the model-computed permeability correlates well with experimental results,with a relative error of less than 15%.The modified IFU model performs well in quantitatively characterizing the heterogeneity of sand-conglomerate pore structures,and provides a methodology for the study of other similar types of heterogeneous reservoirs.展开更多
It is of great significance to study the spatial distribution patterns and petrophysical complexity of volcanic vesicles which determine whether the reservoir spaces of the volcanic rocks can accumulate oil and gas an...It is of great significance to study the spatial distribution patterns and petrophysical complexity of volcanic vesicles which determine whether the reservoir spaces of the volcanic rocks can accumulate oil and gas and enrich high yields or not.In this paper,the digital images of three different textures of vesicular andesite samples,including spherical vesicular andesite,shear deformation vesicular andesite,and secondary filling vesicular andesite,are obtained by microscopic morphology X-CT imaging technology.The spatial micro-vesicle heterogeneity of vesicular andesite samples with different textures is quantitatively analyzed by fractal and multifractal methods such as box-counting dimension and the moment method.It is found that the shear stress weakens the spatial homogeneity since vesicles rupture are accelerated,elongated directionally,and connected with one another under the strain;the secondary filling breaks the vesicles,which significantly enhances the spatial heterogeneity.In addition,shear stress and secondary filling increase the complexity of vesicle microstructures characterized by different fractal and multifractal parameters.These conclusions will provide important theoretical and practical insights into understanding the degassing of volcanic rocks and prediction of high-quality volcanic reservoirs.展开更多
Summary What is already known about this topic?Pneumococcal diseases(PDs)pose a serious health threat to children.Vaccination is the most costeffective intervention to prevent PDs,but pneumococcal vaccines coverage am...Summary What is already known about this topic?Pneumococcal diseases(PDs)pose a serious health threat to children.Vaccination is the most costeffective intervention to prevent PDs,but pneumococcal vaccines coverage among children is low in China.What is added by this report?This study investigated the willingness of children’s caregivers to have their children vaccinated with pneumococcal vaccines under an innovative policy to offer 1-dose of the 13-valent pneumococcal conjugate vaccines at no charge to families.The research found that 70.51%of caregivers were willing to have their infants receive pneumococcal vaccines and that reducing the cost of vaccines may increase caregivers’willingness.What are the implications for public health practice?This is the first evaluation in China of acceptance of pneumococcal vaccines among children under a 1-dose,cost-free policy.The results provide scientific evidence for updating local and national pneumococcal immunization strategies to promote the use of the pneumococcal vaccine.展开更多
Summary What is already known on this topic?Pneumococcal diseases(PDs)are serious threats to child health.Although vaccination is one of the most effective ways to prevent these diseases,the pneumococcal vaccination c...Summary What is already known on this topic?Pneumococcal diseases(PDs)are serious threats to child health.Although vaccination is one of the most effective ways to prevent these diseases,the pneumococcal vaccination coverage rate is still relatively low in China.What is added by this report?This study investigated the factors associated with 13-valent pneumococcal conjugate vaccine(PCV13)vaccine hesitancy in parents under an innovative immunization strategy.展开更多
基金financially funded by the National Key R&D Program of China(No.2016YFC0600501)the Natural Science Foundation of China(Nos.41572315,41872250)the Fundamental Research Funds for the Central Universities,China University of Geosciences(Wuhan)(No.CUG170104)
文摘Shale gas resources have been regarded as a viable energy source, and it is of great significance to characterize the shale composition of different cements, such as quartz and dolomite. In this research, chemical analysis and the multifractal method have been used to study the mineral compositions and petrophysical structures of cements in shale samples from the Longmaxi Formation, China. X-ray diffraction, electron microprobe, field emission scanning electron microscopy, cathodoluminescence microscopy and C-O isotope analyses confirmed that cements in the Longmaxi Formation shales are mainly composed of Fe-bearing dolomite and quartz. Fe-bearing dolomite cements concentrate around dolomite as annuli, filling micron-sized inorganic primary pores. Quartz cements in the form of nanoparicles fill primary inter-crystalline pores among clay minerals. Theoretical calculation shows that the Fe-bearing dolomite cements formed slightly earlier than the quartz cements, but both were related to diagenetic illitization of smectite. Moreover, multifractal analysis reveals that the quartz cements are more irregularly distributed in pores than the Fe-bearing dolomite cements. These results suggest that the plugging effect of the quartz cements on the primary inoraganic pore structures is the dominant factor resulting in low interconnected porosity of shales, which are unfavorable for the enrichment of shale gas.
基金supported by the Foundation of China Geological Survey(Nos.12120113087100,12120113022600)the Basic Scientific Research of the Institute of Geophysical Geochemical Exploration,Chinese Academy of Geological Sciences(No.WHS201302)
文摘Ziyang County, Shaanxi Province, China is a world known selenium（Se）-enriched area, and a severe selenosis incident was reported in Naore Village during the 1990 s. This study investigated the geochemical characteristics of Se and its fractions in Se-enriched rocks from Ziyang. Se distribution is uneven, ranging from 0.23 to 57.00 μg/g（17.29±15.52 μg/g）. Se content is higher in slate than chert, and even lower in carbonate rocks. Cd, As and V are enriched but Pb is depleted in Se-enriched strata. Se has different correlations both with TS（total sulfur）（R^2=0.59 for chert） and TC（total carbon）（R^2=0.77 for slate, R^2=0.87 for carbonate）. Se has significant positive correlations with V（r=0.65）, As（r=0.485）, Cd（r=0.459） and Pb（r=0.405）. The Se level correlates with mineral content, positively with pyrite, chlorite and illite, negatively with albite. Se associated with sulfide/selenide and elemental Se are the predominant fractions of total recovered Se, suggesting that a reducing environment and the formation of sulfides were significant to Se deposition during its geochemical cycle. Although low concentration of bio-available Se（average 5.62%±3.69%） may reduce the risk of Se poisoning in the target area, utilization of Se-rich rock as natural fertilizer should be restricted.
基金financially supported by the Special Project on Mineral Exploration and Assessment in Tibetan Plateau (No. 1212010818038)the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China (No. IRT1083)the National Natural Science Foundation of China (No. 41272362)
文摘The aim of this study is to quantify the geochemical elements distribution patterns analyzed from stream sediment data and then to delineate favorable areas for mineral exploration. A total of 7 270 stream sediment samples were collected from four subareas and 37 rock（ore） chip samples from five different locations in the Bange region, northern Tibet（China）. The multifractal spectra of 12 elements including Au, Ag, As, Cu, Mo, Pb, Zn, W, Sn, Bi, Sb and Hg are represented by the method of moments, and characterized by five quantitative multifractal parameters. The results show that the multifractality for Cu and Bi in the Gongma area is much stronger than those in other subareas. Both the asymmetry index of multifractal spectra and the variance coefficients of Cu and Bi in this area are the highest, which imply that the distribution pattern of Cu and Bi in the Gongma area is the most heterogeneous. These multifractal parameters indicate that the Gongma area is the most favorable for prospecting Cu and Bi. The results obtained by the method of moments are in agreement with petrochemical analysis and field observation. It is suggested that multifractal analysis can be used as an effective tool to evaluate the ore-forming potential in the study area and to provide new approaches for geochemical exploration.
基金supported by the National Key Basic Research and Development Program(973 Program)of China(No.2014CB239000)the China National Science and Technology Major Projects(No.2017ZX05001)the Petrochina Science and Technology Major Projects(No.2016B-0304).
文摘The microscopic pore structure of sand-conglomerate rocks plays a decisive role in its exploration and development of such reservoirs.Due to complex gravels-cements configurations and resultant high heterogeneity in sand-conglomerate rocks,the conventional fractal dimensions are inadequate to fully characterize the pore space.Based on the Pia Intermingled Fractal Units(IFU)model,this paper presents a new variable-ratio factor IFU model,which takes tortuosity and boundary layer thickness into consideration,to characterize the Triassic Karamay Formation conglomerate reservoirs in the Mahu region of the Junggar Basin,Northwest China.The modified model has a more powerful and flexible ability to simulate pore structures of porous media,and the simulation results are closer to the real conditions of pore space in low-porosity and low-permeability reservoirs than the conventional Pia IFU model.The geometric construction of the model is simplified to allow for an easing of computation.Porosity and spectral distribution of pore diameter,constructed using the modified model,are generally consistent with actual core data.Also,the model-computed permeability correlates well with experimental results,with a relative error of less than 15%.The modified IFU model performs well in quantitatively characterizing the heterogeneity of sand-conglomerate pore structures,and provides a methodology for the study of other similar types of heterogeneous reservoirs.
基金supported by the Natural Science Foundation of China(No.41872250)supported by PetroChina Dagang Oilfield Company“Study on Igneous Rock Distribution and Reservoir Prediction in Dagang Exploration Area”(No.DGTY-2018-JS-408)China National Petroleum Corporation Major Science and Technology Program“Research and Application of Key Technologies for Increasing Efficiency,Storing and Stabilizing Production in Dagang Oilfield”(No.2018E-11).
文摘It is of great significance to study the spatial distribution patterns and petrophysical complexity of volcanic vesicles which determine whether the reservoir spaces of the volcanic rocks can accumulate oil and gas and enrich high yields or not.In this paper,the digital images of three different textures of vesicular andesite samples,including spherical vesicular andesite,shear deformation vesicular andesite,and secondary filling vesicular andesite,are obtained by microscopic morphology X-CT imaging technology.The spatial micro-vesicle heterogeneity of vesicular andesite samples with different textures is quantitatively analyzed by fractal and multifractal methods such as box-counting dimension and the moment method.It is found that the shear stress weakens the spatial homogeneity since vesicles rupture are accelerated,elongated directionally,and connected with one another under the strain;the secondary filling breaks the vesicles,which significantly enhances the spatial heterogeneity.In addition,shear stress and secondary filling increase the complexity of vesicle microstructures characterized by different fractal and multifractal parameters.These conclusions will provide important theoretical and practical insights into understanding the degassing of volcanic rocks and prediction of high-quality volcanic reservoirs.
基金Supported by Education Foundation of Peking Union Medical College and funded by Bill&Melinda Gates Foundation Donation Project(OPP1216666)the discipline construction funds of Population Medicine from Peking Union Medical College(WH10022021145).
文摘Summary What is already known about this topic?Pneumococcal diseases(PDs)pose a serious health threat to children.Vaccination is the most costeffective intervention to prevent PDs,but pneumococcal vaccines coverage among children is low in China.What is added by this report?This study investigated the willingness of children’s caregivers to have their children vaccinated with pneumococcal vaccines under an innovative policy to offer 1-dose of the 13-valent pneumococcal conjugate vaccines at no charge to families.The research found that 70.51%of caregivers were willing to have their infants receive pneumococcal vaccines and that reducing the cost of vaccines may increase caregivers’willingness.What are the implications for public health practice?This is the first evaluation in China of acceptance of pneumococcal vaccines among children under a 1-dose,cost-free policy.The results provide scientific evidence for updating local and national pneumococcal immunization strategies to promote the use of the pneumococcal vaccine.
基金Supported by Education Foundation of Peking Union Medical College(WH10022021145)Bill&Melinda Gates Foundation(OPP1216666).
文摘Summary What is already known on this topic?Pneumococcal diseases(PDs)are serious threats to child health.Although vaccination is one of the most effective ways to prevent these diseases,the pneumococcal vaccination coverage rate is still relatively low in China.What is added by this report?This study investigated the factors associated with 13-valent pneumococcal conjugate vaccine(PCV13)vaccine hesitancy in parents under an innovative immunization strategy.
