The heavy mineral sands of Senegal are exploited to extract titanium oxides and zircon. Mining is carried out first by means of a floating dredge and concentration plant which produce</span><span style="...The heavy mineral sands of Senegal are exploited to extract titanium oxides and zircon. Mining is carried out first by means of a floating dredge and concentration plant which produce</span><span style="font-family:Verdana;">s</span><span style="font-family:""><span style="font-family:Verdana;"> a heavy mineral concentrate (HMC) containing on average 78% titanium oxides, 11% zircon and a set of silicate and alumino-silicate minerals. This heavy mineral concentrate is then treated by gravity, magnetic and electrostatic separation to produce titanium oxide concentrates (ilmenite, leucoxene, rutile) and three varieties of zircon concentrates (Premium zircon, standard zircon and medium grade zircon standard). In this study, we describe the various mineral concentrates in terms of mineralogical assemblages, and textural variability within grains, using Qemscan and Scanning Electron Microscopy. The titanium oxide concentrates are differentiated by their TiO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> content and vary from ilmenite to rutile. The zircon concentrates are characterized by the presence of impurities in the zircons, which consist in numerous inclusions of titanium oxides and silicate minerals. The mineralogical characteristics determined by scanning electron microscopy and by Qemscan showed great variability within the grains themselves. Heavy minerals contain many mineral inclusions and show strong chemical zoning.展开更多
As a key factor restricting the fracturing effect of shale reservoir,the origin and content of quartz components have always been the focus of academic and industrial circles.Due to the great influence of diagenesis p...As a key factor restricting the fracturing effect of shale reservoir,the origin and content of quartz components have always been the focus of academic and industrial circles.Due to the great influence of diagenesis process,the accuracy of trace element determination to identify the origin of quartz is not good,which can not meet the increasingly accurate research requirements.In this paper,mineral quantitative analysis technology(QemScan)is used to identify quartz components by two-dimensional quantitative scanning,and the content data of quartz components with different grain sizes are extracted.The results show that the size of quartz particles is obviously controlled by the difference of sedimentary water and sedimentary environment,that is,quartz particles less than 30 mm are mainly concentrated in Long112 and Long114 layers,which is the normal oxygen environment under the background of medium retention in deep water environment;quartz particles larger than 20 mm are mainly concentrated in Long111 and Long113 layers,which is the poor oxygen environment under the background of strong retention in deep water environment.In shallow water environment,the stronger hydrodynamic conditions make the strata rich in terrigenous clastic quartz particles with larger grain size,and oxygen poor environment is conducive to the enrichment of authigenic quartz with smaller grain size.展开更多
The types and structures of inorganic pores are key factors in evaluations of the reservoir space and distribution characteristics of shale oil and gas.However,quantitative identification methods for pores of differen...The types and structures of inorganic pores are key factors in evaluations of the reservoir space and distribution characteristics of shale oil and gas.However,quantitative identification methods for pores of different inorganic components have not yet been fully developed.For this reason,a quantitative characterization method of inorganic pores using pixel information was proposed in this study.A machine learning algorithm was used to assist the field emission scanning electron microscopy(FE-SEM)image processing of shale to realize the accurate identification and quantitative characterization of inorganic pores on the surface of high-precision images of shale with a small view.Moreover,large-view image splicing technology,combined with quantitative evaluation of minerals by scanning electron microscopy(QEMSCAN)image joint characterization technology,was used to accurately analyze the distribution characteristics of inorganic pores under different mineral components.The quantitative methods of pore characteristics of different inorganic components under the pixel information of shale were studied.The results showed that(1)the Waikato Environment for Knowledge Analysis(WEKA)machine learning model can effectively identify and extract shale mineral components and inorganic pore distribution,and the large-view FE-SEM images are representative of samples at the 200μm×200μm view scale,meeting statistical requirements and eliminating the influence of heterogeneity;(2)the pores developed by different mineral components of shale had obvious differences,indicating that the development of inorganic pores is highly correlated with the properties of shale minerals themselves;and(3)the pore-forming ability of different mineral components is calculated by the quantitative method of single component pore-forming coefficient.Chlorite showed the highest pore-forming ability,followed by(in descending order)illite,pyrite,calcite,dolomite,albite,orthoclase,quartz,and apatite.This study contributes to advancing our understanding of inorganic pore characteristics in shale.展开更多
The pressure-sensitive effect on the pore structure of sandstone was investigated using X-ray computed micro-tomography and QEMSCAN quantitative mineral analysis. In a physical simulation study, we extracted the pore ...The pressure-sensitive effect on the pore structure of sandstone was investigated using X-ray computed micro-tomography and QEMSCAN quantitative mineral analysis. In a physical simulation study, we extracted the pore network model from digital cores at different confining pressures and evaluated the effect of pressure sensitivity on the multiphase displacement process. In both the pore network model and QEMSCAN scanning, the pore structure was observed to be damaged under a high confining pressure. Due to their different scales, the pores and throats exhibited inhomogeneous changes; further, the throats exhibited a significant variation compared to that exhibited by the pores. Meanwhile, the heterogeneity of the pore structure under the two aforementioned activities was aggravated by the elastic-plastic deformation of the pore structure.The pressure-sensitive effect increased the proportion of mineral particles, such as quartz(the main component of the core skeleton), and reduced the proportion of clay minerals. The clay minerals were originally attached to the pore walls or interspersed in the pores; however, as the pressure increased, the clay minerals accumulated in the pores resulting in blockage of the pores. While simulating the multiphase displacement process, increasing the confining pressure was observed to severely restrict the flowability of oil and water. This study promises to improve the efficiency of reservoir development in terms of oil and gas exploitation.展开更多
文摘The heavy mineral sands of Senegal are exploited to extract titanium oxides and zircon. Mining is carried out first by means of a floating dredge and concentration plant which produce</span><span style="font-family:Verdana;">s</span><span style="font-family:""><span style="font-family:Verdana;"> a heavy mineral concentrate (HMC) containing on average 78% titanium oxides, 11% zircon and a set of silicate and alumino-silicate minerals. This heavy mineral concentrate is then treated by gravity, magnetic and electrostatic separation to produce titanium oxide concentrates (ilmenite, leucoxene, rutile) and three varieties of zircon concentrates (Premium zircon, standard zircon and medium grade zircon standard). In this study, we describe the various mineral concentrates in terms of mineralogical assemblages, and textural variability within grains, using Qemscan and Scanning Electron Microscopy. The titanium oxide concentrates are differentiated by their TiO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> content and vary from ilmenite to rutile. The zircon concentrates are characterized by the presence of impurities in the zircons, which consist in numerous inclusions of titanium oxides and silicate minerals. The mineralogical characteristics determined by scanning electron microscopy and by Qemscan showed great variability within the grains themselves. Heavy minerals contain many mineral inclusions and show strong chemical zoning.
基金This work was supported in part by National Natural Science Foundation of China(No.51804038)PetroChina Innovation Foundation(No.2018D-5007-0210)+1 种基金Innovation and entrepreneurship training program for college students in Hubei Province(S202010489032)Innovation and entrepreneurship project for college students of Yangtze University(2019026).
文摘As a key factor restricting the fracturing effect of shale reservoir,the origin and content of quartz components have always been the focus of academic and industrial circles.Due to the great influence of diagenesis process,the accuracy of trace element determination to identify the origin of quartz is not good,which can not meet the increasingly accurate research requirements.In this paper,mineral quantitative analysis technology(QemScan)is used to identify quartz components by two-dimensional quantitative scanning,and the content data of quartz components with different grain sizes are extracted.The results show that the size of quartz particles is obviously controlled by the difference of sedimentary water and sedimentary environment,that is,quartz particles less than 30 mm are mainly concentrated in Long112 and Long114 layers,which is the normal oxygen environment under the background of medium retention in deep water environment;quartz particles larger than 20 mm are mainly concentrated in Long111 and Long113 layers,which is the poor oxygen environment under the background of strong retention in deep water environment.In shallow water environment,the stronger hydrodynamic conditions make the strata rich in terrigenous clastic quartz particles with larger grain size,and oxygen poor environment is conducive to the enrichment of authigenic quartz with smaller grain size.
基金supported by the National Natural Science Foundation of China(42372144)the Natural Science Foundation of Xinjiang Uygur Autonomous Region(2024D01E09)the Strategic Cooperation Technology Projects of CNPC and CUPB(ZLZX2020-01-05).
文摘The types and structures of inorganic pores are key factors in evaluations of the reservoir space and distribution characteristics of shale oil and gas.However,quantitative identification methods for pores of different inorganic components have not yet been fully developed.For this reason,a quantitative characterization method of inorganic pores using pixel information was proposed in this study.A machine learning algorithm was used to assist the field emission scanning electron microscopy(FE-SEM)image processing of shale to realize the accurate identification and quantitative characterization of inorganic pores on the surface of high-precision images of shale with a small view.Moreover,large-view image splicing technology,combined with quantitative evaluation of minerals by scanning electron microscopy(QEMSCAN)image joint characterization technology,was used to accurately analyze the distribution characteristics of inorganic pores under different mineral components.The quantitative methods of pore characteristics of different inorganic components under the pixel information of shale were studied.The results showed that(1)the Waikato Environment for Knowledge Analysis(WEKA)machine learning model can effectively identify and extract shale mineral components and inorganic pore distribution,and the large-view FE-SEM images are representative of samples at the 200μm×200μm view scale,meeting statistical requirements and eliminating the influence of heterogeneity;(2)the pores developed by different mineral components of shale had obvious differences,indicating that the development of inorganic pores is highly correlated with the properties of shale minerals themselves;and(3)the pore-forming ability of different mineral components is calculated by the quantitative method of single component pore-forming coefficient.Chlorite showed the highest pore-forming ability,followed by(in descending order)illite,pyrite,calcite,dolomite,albite,orthoclase,quartz,and apatite.This study contributes to advancing our understanding of inorganic pore characteristics in shale.
文摘The pressure-sensitive effect on the pore structure of sandstone was investigated using X-ray computed micro-tomography and QEMSCAN quantitative mineral analysis. In a physical simulation study, we extracted the pore network model from digital cores at different confining pressures and evaluated the effect of pressure sensitivity on the multiphase displacement process. In both the pore network model and QEMSCAN scanning, the pore structure was observed to be damaged under a high confining pressure. Due to their different scales, the pores and throats exhibited inhomogeneous changes; further, the throats exhibited a significant variation compared to that exhibited by the pores. Meanwhile, the heterogeneity of the pore structure under the two aforementioned activities was aggravated by the elastic-plastic deformation of the pore structure.The pressure-sensitive effect increased the proportion of mineral particles, such as quartz(the main component of the core skeleton), and reduced the proportion of clay minerals. The clay minerals were originally attached to the pore walls or interspersed in the pores; however, as the pressure increased, the clay minerals accumulated in the pores resulting in blockage of the pores. While simulating the multiphase displacement process, increasing the confining pressure was observed to severely restrict the flowability of oil and water. This study promises to improve the efficiency of reservoir development in terms of oil and gas exploitation.
