Carbonate reservoirs exhibit strong heterogeneity in the distribution of pore types that can be quantitatively characterized by applying Xu–Payne multi-porosity model.However,there are some prerequisites to this mode...Carbonate reservoirs exhibit strong heterogeneity in the distribution of pore types that can be quantitatively characterized by applying Xu–Payne multi-porosity model.However,there are some prerequisites to this model the porosity and saturation need to be provided.In general,these application conditions are difficult to satisfy for seismic data.In order to overcome this problem,we present a two-step method to estimate the porosity and saturation and pore type of carbonate reservoirs from seismic data.In step one,the pore space of the carbonate reservoir is equivalent to a single-porosity system with an effective pore aspect ratio;then,a 3D rock-physics template(RPT)is established through the Gassmann’s equations and effective medium models;and then,the effective aspect ratio of pore,porosity and fluid saturation are simultaneously estimated from the seismic data based on 3D RPT.In step two,the pore space of the carbonate reservoir is equivalent to a triple-porosity system.Combined with the inverted porosity and saturation in the first step,the porosities of three pore types can be inverted from the seismic elastic properties.The application results indicate that our method can obtain accurate physical properties consistent with logging data and ensure the reliability of characterization of pore type.展开更多
Carbonate,tight sandstone,and shale reservoirs have many pore types,and the relationship between the porosity and elastic parameters is extremely discrete due to the complex pore shape.This paper presents a method for...Carbonate,tight sandstone,and shale reservoirs have many pore types,and the relationship between the porosity and elastic parameters is extremely discrete due to the complex pore shape.This paper presents a method for predicting reservoir pore types based on pore shape substitution.The pore shape substitution allows for accurately characterizing the changes in the elastic properties of the rock with the changes in pore shape,assuming there are no changes in terms of minerals,porosity,or fl uids.By employing a multiple-porosity variable critical porosity model,the eff ective pore aspect ratio could be inverted from the velocities of the rock.To perform pore shape substitution,we could replace the eff ective pore aspect ratio with another pore aspect ratio or increase/decrease the volume content of diff erent pore shapes.The reservoir pore types could be evaluated by comparing the differences in the reservoir velocities before and after the substitution of the pore shape.The test results pertaining to the theoretical model and the well logging data indicated that the pore shape substitution method could be applied to characterize pore types in terms of separating the eff ects of the pore shapes from the eff ects of the minerals,porosity,or fl uids on the velocities.展开更多
Carbonate reservoirs are known for their complex pore structures,which lead to variable elastic behaviors and seismic responses.These variations pose significant challenges for seismic interpretation of carbonate rese...Carbonate reservoirs are known for their complex pore structures,which lead to variable elastic behaviors and seismic responses.These variations pose significant challenges for seismic interpretation of carbonate reservoirs.Therefore,quantitative characterization of pore structure is crucial for accurate fluid detection and reservoir property estimation.To address the complexity of pore geometry and the uneven fluid distribution in tight carbonate reservoirs,we develop a triple-pore effective medium model by integrating the extended Keys-Xu model with the Gassmann-Hill equation.Comparison between the theoretical modeling results and an available laboratory data set verifies the effectiveness of this model in pore type quantification.Based on this calibrated model,we propose a novel two-step triple pore-type inversion strategy with varying pore aspect ratio via a grid-searching algorithm.We apply this method to well logs and 3D seismic data from the tight carbonate reservoirs of the Ordovician Majiagou formation in the Ordos Basin.The good agreement between pore-type estimates and logging interpretation results suggests that our method significantly improves the accuracy of porosity estimates for different pore types,outperforming the pore-type inversion method with fixed pore aspect ratios.The successful application to seismic data also demonstrates that the proposed method provides a reliable distribution of pore types in tight carbonate reservoirs,confirming its applicability and feasibility in seismic pore-type estimation.This method not only facilitates the recognition of complex pore geometries but also provides valuable insights for accurate detection of high-quality reservoirs.展开更多
The pore-throat systems and physical properties of tight sandstone reservoirs are complex,and deposition is thought to be a fundamental control for them.In this study,the impacts of the full ranges of rock types(from ...The pore-throat systems and physical properties of tight sandstone reservoirs are complex,and deposition is thought to be a fundamental control for them.In this study,the impacts of the full ranges of rock types(from pebbly coarse sandstone to fine sandstone) on the pore structures and physical properties of the Permian tight sandstone reservoir in the eastern Ordos Basin were investigated comprehensively through a series of experiments including conventional physical testing,thin-section analysis,scanning electron microscopy,nuclear magnetic resonance analysis and high-pressure mercury injection tests.The results showed that the coarser-grained sandstones tend to have higher feldspar content and lower percentage of cements,leading to strong dissolution,weak cementation and improved porosity and permeability.The medium sandstone has the highest level of quartz and the lowest average content of feldspar,resulting in strong heterogeneity of physical properties.Only those medium sandstone reservoirs with relatively high content of feldspars have better physical properties.Additionally,the coarser-grained sandstones contain relatively large dissolution pores(nearly 200 μm),whereas the finer-grained sandstones have more intercrystalline pores with a relatively more homogeneous pore structure.The pebbly coarse sandstone and coarse sandstone reservoirs are favorable targets with best physical properties.展开更多
Shale samples from the Ordovician Wulalike Formation at the western margin of the Ordos Basin are studied to define the types, microstructures and connectivity of pores as well as the relationships between the pore st...Shale samples from the Ordovician Wulalike Formation at the western margin of the Ordos Basin are studied to define the types, microstructures and connectivity of pores as well as the relationships between the pore structures and gas content of the samples by using experimental techniques such as high-resolution field emission scanning electron microscopy (FESEM), mercury injection capillary pressure (MICP), low-temperature nitrogen adsorption (LTNA), CO_(2) adsorption, and focused ion beam scanning electron microscopy (FIB-SEM). The results show that the shale has 10 different lithofacies, typical mixed sedimentary characteristics, and poorly developed pores. The reservoir space mainly consists of intercrystalline pores, dissolution pores, intergranular pores, and micro-fissures, with organic pores occasionally visible. The pore size is mostly within 0.4–250 nm range but dominated by micropores and mesopores less than 20 nm, with pore numbers peaking at pore sizes of 0.5 nm, 0.6 nm, 0.82 nm, 3 nm, and 10 nm, respectively. The pores are poorly connected and macropores are rarely seen, which may explain the low porosity and low permeability of the samples. Samples with high content of organic matter and felsic minerals are potential reservoirs for oil and gas with their favorable physical properties and high connectivity. The pores less than 5 nm contribute significantly to the specific surface area and serve as important storage space for adsorbed gas.展开更多
With the aim of better understanding the tight gas reservoirs in the Zizhou area of east Ordos Basin,a total of 222 samples were collected from 50 wells for a series of experiments.In this study,three pore-throat comb...With the aim of better understanding the tight gas reservoirs in the Zizhou area of east Ordos Basin,a total of 222 samples were collected from 50 wells for a series of experiments.In this study,three pore-throat combination types in sandstones were revealed and confirmed to play a controlling role in the distribution of throat size and the characteristics of gas-water relative permeability.The type-I sandstones are dominated by intercrystalline micropores connected by cluster throats,of which the distribution curves of throat size are narrow and have a strong single peak(peak ratio>30%).The pores in the type-II sandstones dominantly consist of secondary dissolution pores and intercrystalline micropores,and throats mainly occur as slice-shaped throats along cleavages between rigid grain margins and cluster throats in clay cement.The distribution curves of throat size for the type-II sandstones show a bimodal distribution with a substantial low-value region between the peaks(peak ratio<15%).Primary intergranular pores and secondary intergranular pores are mainly found in type-III samples,which are connected by various throats.The throat size distribution curves of type-III sandstones show a nearly normal distribution with low kurtosis(peak ratio<10%),and the micro-scale throat radii(>0.5μm)constitute a large proportion.From type-I to type-III sandstones,the irreducible water saturation(Swo)decreased;furthermore,the slope of the curves of Krw/Krg in two-phase saturation zone decreased and the two-phase saturation zone increased,indicating that the gas relative flow ability increased.Variations of the permeability exist in sandstones with different porethroat combination types,which indicate the type-III sandstones are better reservoirs,followed by type-II sandstones and type-I sandstones.As an important factor affecting the reservoir quality,the pore-throat combination type in sandstones is the cumulative expression of lithology and diagenetic modifications with strong heterogeneity.展开更多
Structure of porous media and fluid distribution in rocks can significantly affect the transport characteristics during the process of microscale tracer flow.To clarify the effect of micro heterogeneity on aqueous tra...Structure of porous media and fluid distribution in rocks can significantly affect the transport characteristics during the process of microscale tracer flow.To clarify the effect of micro heterogeneity on aqueous tracer transport,this paper demonstrates microscopic experiments at pore level and proposes an improved mathematical model for tracer transport.The visualization results show a faster tracer movement into movable water than it into bound water,and quicker occupancy in flowing pores than in storage pores caused by the difference of tracer velocity.Moreover,the proposed mathematical model includes the effects of bound water and flowing porosity by applying interstitial flow velocity expression.The new model also distinguishes flowing and storage pores,accounting for different tracer transport mechanisms(dispersion,diffusion and adsorption)in different types of pores.The resulting analytical solution better matches with tracer production data than the standard model.The residual sum of squares(RSS)from the new model is 0.0005,which is 100 times smaller than the RSS from the standard model.The sensitivity analysis indicates that the dispersion coefficient and flowing porosity shows a negative correlation with the tracer breakthrough time and the increasing slope,whereas the superficial velocity and bound water saturation show a positive correlation.展开更多
The aim of this work is to understand the effect of a thin coating on the compressive properties of the porous metal.In our work,the uniaxial compressive behavior and the energy absorption properties of the lotus-type...The aim of this work is to understand the effect of a thin coating on the compressive properties of the porous metal.In our work,the uniaxial compressive behavior and the energy absorption properties of the lotus-type porous copper deposited with Ni coatings with thickness from 3.9 to 4.8μm on pore walls were investigated.It is found that the Ni coating on pore walls shows a clear enhancement effect on compressive properties of the lotus-type porous copper,in which the specific yield strength and the energy absorption per unit mass at densification strain increase from 5.27 to 7.31 MPa cm3 g-1 and from 11.50 to 18.21 J g-1 with the Ni coating,respectively.Furthermore,the enhancement appears to be insensitive to the coating thickness.It is considered that the resistance of the interface between the nickel coating and the pore walls to the dislocation slip plays an important role in the improvement on compressive properties of the lotus-type porous copper.展开更多
In this work,the Permian Longtan marine-continental transitional shale in the southeast of Sichuan Basin was taken as study object.Through petrology and geochemical analysis,lithofacies types of the marine-continental...In this work,the Permian Longtan marine-continental transitional shale in the southeast of Sichuan Basin was taken as study object.Through petrology and geochemical analysis,lithofacies types of the marine-continental transitional shale were classified,key controlling factors of physical properties and gas content of the different shale lithofacies were analyzed.The research results show that the Longtan Formation marine-continental transitional shale in the study area has four types of lithofacies,namely,organic-lean calcareous shale,organic-lean mixed shale,organic-lean argillaceous shale,and organic-rich argillaceous shale,among which the organic-rich argillaceous shale is the most favorable lithofacies of the study area.The pore types of different lithofacies vary significantly and the clay mineral-related pore is the dominant type of the pore system in the study area.The main controlling factor of the physical properties is clay mineral content,and the most important factor affecting gas content is TOC content.Compared with marine shale,the marine-continental transitional shale has low average values,wide distribution range,and strong heterogeneity in TOC content,porosity,and pore structure parameters,but still contains some favorable layers with high physical properties and gas contents.The organic-rich clay shale deposited in tidal flat-lagoon system is most likely to form shale gas sweet spots,so it should be paid more attention in shale gas exploration.展开更多
Based on scanning electron microscopy and mercury porosimmetry,a large number of experimental data of pores and pore throats of tight sandstone reservoirs are obtained,and the characteristics of pore types,capillary p...Based on scanning electron microscopy and mercury porosimmetry,a large number of experimental data of pores and pore throats of tight sandstone reservoirs are obtained,and the characteristics of pore types,capillary pressure curves and quantitative parameters of pore throats of Yanchang Formation in Huangling mining area are studied.The results show that the main reservoir space types of Yanchang Formation sandstone are primary intergranular pores and feldspar dissolution pores.The pore-throat structure is medium-small pore and thin-small throat type,and the sorting is good to medium.The mercury porosimmetry curve shows a slightly coarse-thin skew.Combining the morphological characteristics of the mercury porosimmetry capillary pressure curve and the quantitative parameter characteristics of pore throats,the Yanchang Formation s micro pore structure is divided into types I,II,III,and IV.Tight oil reservoirs with type I and II pore structure characteristics are favorable.This study has reference significance for the later evaluation of tight sandstone reservoirs in Huangling mining area.展开更多
This study analyzed the characteristics and types of the Lower Silurian shale gas reservoirs in and around Sichuan Basin through field observations, slices, Ar-ion-beam milling, scanning electron microscopy, and x-ray...This study analyzed the characteristics and types of the Lower Silurian shale gas reservoirs in and around Sichuan Basin through field observations, slices, Ar-ion-beam milling, scanning electron microscopy, and x-ray diffraction analysis of 25 black shale outcrops and samples. Two main types of shale gas reservoirs were determined, i.e., fractures and pores. Fractures were classified into five categories, i.e., giant, large, medium, small, and micro, according to the features of the shale gas reservoirs, effect of fracture on gas accumulation, and fracture nature. Pore types include organic matter pores, mineral pores（mineral surface, intraparticle, interparticle, and corrosional pore）, and nanofractures. The various fracture types, fracture scales, pore types, and pore sizes exert different controls over the gas storage and production capacity. Pores serve as a reservoir for gas storage and, the gas storage capacity can be determined using pores; fractures serve as pathways for gas migration, and gas production capacity can be determined using them.展开更多
Aiming at the complicated problem of the genesis of high-quality hybrid sedimentary rocks,the pore-throat systems,controlling factors and fluid mobility of hybrid sedimentary rocks in the Permian Lucaogou Formation in...Aiming at the complicated problem of the genesis of high-quality hybrid sedimentary rocks,the pore-throat systems,controlling factors and fluid mobility of hybrid sedimentary rocks in the Permian Lucaogou Formation in Jimusar Sag were examined.The results show that the hybrid sedimentary rocks contain 5 types of pore-throat system,intergranular(Type A),mixed intergranular-dissolved-intercrystalline(Type B),dissolved(Type C),mixed dissolved-intercrystalline(Type D)and intercrystalline(Type E)ones.The pore-throat systems are controlled by 3 major factors,the component content and arrangement(CCA)of hybrid sedimentary rocks,sedimentary environment and diagenesis.CCA controls the matrix support mode of hybrid sedimentary rocks,and therefore controls the types and changes of pore-throat system.The sedimentary environment mainly controls the macroscopic distribution of pore-throat system,i.e.,hybrid sedimentary rocks deposited in the near source and high-energy environment are characterized by high content of coarse-grained component,granular/interbedded-support mode,and development of Type A and Type B pore-throat systems.Hybrid sedimentary rocks deposited in the medium-energy environment far from source are characterized by dolomitic/mud support mode and Type C and Type D pore-throat systems.Hybrid sedimentary rocks deposited in low-energy environment far from source have mainly Type E and Type D pore-throat systems.Diagenetic processes such as compaction and calcite cementation make the proportions of Type A and Type C pore-throat systems decrease further.In the hybrid sedimentary process of sandy-mud,pore-throat system types show a change of"A→B→C→D",in that of dolomite-sand,pore-throat system types show a change of"A→C→D→E"or"B→D→E",and in that of dolomite-mud,pore-throat system types show a change of"D→E",which are affected in details by the contents of coarse-grain component,feldspar and dolomite.The reservoir with Type A pore-throats has the best physical properties and fluid mobility,and the reservoirs with Type D and Type E pore-throats have the poorest.The movable fluid distribution is related to the matrix support mode,and the larger pores in hybrid sedimentary rocks of dolomite/mud support mode have no obvious advantage in fluid mobility.The findings of this study provide a geological basis for evaluating and building reasonable interpretation model of hybrid sedimentary rocks sweet spot.展开更多
页岩气储层的气水两相渗流能力对其产能有着重要影响,但尚无直接通过测井等地球物理手段评价页岩气流动能力的方法。目前已通过岩心聚焦离子束-扫描电镜(Focused Ion Beam-Scanning Electron Microscope,FIB-SEM)扫描建立页岩无机孔隙...页岩气储层的气水两相渗流能力对其产能有着重要影响,但尚无直接通过测井等地球物理手段评价页岩气流动能力的方法。目前已通过岩心聚焦离子束-扫描电镜(Focused Ion Beam-Scanning Electron Microscope,FIB-SEM)扫描建立页岩无机孔隙、有机孔隙和微裂缝的三维数字岩心模型,基于流体体积法(Volume of Fluid,VOF)开展了不同润湿条件下的页岩孔缝结构气驱水渗流模拟并得到了端点含水饱和度等特征。该文基于模拟结果得到的不同孔隙类型流动能力的认识,结合大面积拼接扫描电镜(Modular Automated Processing System,MAPS)中提取的不同类型的孔隙统计,获得了每块岩心的等效流动能力。将岩心的等效流动能力与岩石物理实验和测井响应进行综合分析,提出了无量纲渗流能力的概念,建立了基于测井资料评价流动能力的模型。实际测井资料处理结果表明,所提出的评价模型具有较高的准确度,可以获得连续的页岩气流动能力剖面,可用于指导页岩气勘探开发。展开更多
基金supported by the China National Key R D plan(2019YFC0605504)Scientific Research&Technology Development Project of China National Petroleum Corporation(Grant Nos.2017D-3504 and 2018D-4305)
文摘Carbonate reservoirs exhibit strong heterogeneity in the distribution of pore types that can be quantitatively characterized by applying Xu–Payne multi-porosity model.However,there are some prerequisites to this model the porosity and saturation need to be provided.In general,these application conditions are difficult to satisfy for seismic data.In order to overcome this problem,we present a two-step method to estimate the porosity and saturation and pore type of carbonate reservoirs from seismic data.In step one,the pore space of the carbonate reservoir is equivalent to a single-porosity system with an effective pore aspect ratio;then,a 3D rock-physics template(RPT)is established through the Gassmann’s equations and effective medium models;and then,the effective aspect ratio of pore,porosity and fluid saturation are simultaneously estimated from the seismic data based on 3D RPT.In step two,the pore space of the carbonate reservoir is equivalent to a triple-porosity system.Combined with the inverted porosity and saturation in the first step,the porosities of three pore types can be inverted from the seismic elastic properties.The application results indicate that our method can obtain accurate physical properties consistent with logging data and ensure the reliability of characterization of pore type.
基金the National Natural Science Foundation of China(Nos.42074136,41674130)National Key S&T Special Project of China(No.2016ZX05027-004-001)the Fundamental Research Funds for the Central University(No.18CX02061A).
文摘Carbonate,tight sandstone,and shale reservoirs have many pore types,and the relationship between the porosity and elastic parameters is extremely discrete due to the complex pore shape.This paper presents a method for predicting reservoir pore types based on pore shape substitution.The pore shape substitution allows for accurately characterizing the changes in the elastic properties of the rock with the changes in pore shape,assuming there are no changes in terms of minerals,porosity,or fl uids.By employing a multiple-porosity variable critical porosity model,the eff ective pore aspect ratio could be inverted from the velocities of the rock.To perform pore shape substitution,we could replace the eff ective pore aspect ratio with another pore aspect ratio or increase/decrease the volume content of diff erent pore shapes.The reservoir pore types could be evaluated by comparing the differences in the reservoir velocities before and after the substitution of the pore shape.The test results pertaining to the theoretical model and the well logging data indicated that the pore shape substitution method could be applied to characterize pore types in terms of separating the eff ects of the pore shapes from the eff ects of the minerals,porosity,or fl uids on the velocities.
基金supported by the National Engineering Laboratory for Exploration and Development of Low-Permeability Oil and Gas Fields(KFKT2023-20)the National Natural Science Foundation of China(42104121)。
文摘Carbonate reservoirs are known for their complex pore structures,which lead to variable elastic behaviors and seismic responses.These variations pose significant challenges for seismic interpretation of carbonate reservoirs.Therefore,quantitative characterization of pore structure is crucial for accurate fluid detection and reservoir property estimation.To address the complexity of pore geometry and the uneven fluid distribution in tight carbonate reservoirs,we develop a triple-pore effective medium model by integrating the extended Keys-Xu model with the Gassmann-Hill equation.Comparison between the theoretical modeling results and an available laboratory data set verifies the effectiveness of this model in pore type quantification.Based on this calibrated model,we propose a novel two-step triple pore-type inversion strategy with varying pore aspect ratio via a grid-searching algorithm.We apply this method to well logs and 3D seismic data from the tight carbonate reservoirs of the Ordovician Majiagou formation in the Ordos Basin.The good agreement between pore-type estimates and logging interpretation results suggests that our method significantly improves the accuracy of porosity estimates for different pore types,outperforming the pore-type inversion method with fixed pore aspect ratios.The successful application to seismic data also demonstrates that the proposed method provides a reliable distribution of pore types in tight carbonate reservoirs,confirming its applicability and feasibility in seismic pore-type estimation.This method not only facilitates the recognition of complex pore geometries but also provides valuable insights for accurate detection of high-quality reservoirs.
基金funded by the National Science and Technology Major Project (2016ZX05061-003-001)Major Project of CNOOC (CNOOC-KJ135ZDXMLTD14)National Natural Science Foundation of China (41672116, 41672125)。
文摘The pore-throat systems and physical properties of tight sandstone reservoirs are complex,and deposition is thought to be a fundamental control for them.In this study,the impacts of the full ranges of rock types(from pebbly coarse sandstone to fine sandstone) on the pore structures and physical properties of the Permian tight sandstone reservoir in the eastern Ordos Basin were investigated comprehensively through a series of experiments including conventional physical testing,thin-section analysis,scanning electron microscopy,nuclear magnetic resonance analysis and high-pressure mercury injection tests.The results showed that the coarser-grained sandstones tend to have higher feldspar content and lower percentage of cements,leading to strong dissolution,weak cementation and improved porosity and permeability.The medium sandstone has the highest level of quartz and the lowest average content of feldspar,resulting in strong heterogeneity of physical properties.Only those medium sandstone reservoirs with relatively high content of feldspars have better physical properties.Additionally,the coarser-grained sandstones contain relatively large dissolution pores(nearly 200 μm),whereas the finer-grained sandstones have more intercrystalline pores with a relatively more homogeneous pore structure.The pebbly coarse sandstone and coarse sandstone reservoirs are favorable targets with best physical properties.
基金funded by a National Science and Technology Major Project(No.2016ZX05007)Chinese Academy of Sciences(CAS)Strategic Leading Science&Technology Program(No.XDA14010000)CNPC's"Fourteenth Five-Year Plan"forward-looking basic strategic major scientific and technological project(No.2021DJ3102).
文摘Shale samples from the Ordovician Wulalike Formation at the western margin of the Ordos Basin are studied to define the types, microstructures and connectivity of pores as well as the relationships between the pore structures and gas content of the samples by using experimental techniques such as high-resolution field emission scanning electron microscopy (FESEM), mercury injection capillary pressure (MICP), low-temperature nitrogen adsorption (LTNA), CO_(2) adsorption, and focused ion beam scanning electron microscopy (FIB-SEM). The results show that the shale has 10 different lithofacies, typical mixed sedimentary characteristics, and poorly developed pores. The reservoir space mainly consists of intercrystalline pores, dissolution pores, intergranular pores, and micro-fissures, with organic pores occasionally visible. The pore size is mostly within 0.4–250 nm range but dominated by micropores and mesopores less than 20 nm, with pore numbers peaking at pore sizes of 0.5 nm, 0.6 nm, 0.82 nm, 3 nm, and 10 nm, respectively. The pores are poorly connected and macropores are rarely seen, which may explain the low porosity and low permeability of the samples. Samples with high content of organic matter and felsic minerals are potential reservoirs for oil and gas with their favorable physical properties and high connectivity. The pores less than 5 nm contribute significantly to the specific surface area and serve as important storage space for adsorbed gas.
基金supported by the Natural Science Foundation of China (grant No. 41772130)
文摘With the aim of better understanding the tight gas reservoirs in the Zizhou area of east Ordos Basin,a total of 222 samples were collected from 50 wells for a series of experiments.In this study,three pore-throat combination types in sandstones were revealed and confirmed to play a controlling role in the distribution of throat size and the characteristics of gas-water relative permeability.The type-I sandstones are dominated by intercrystalline micropores connected by cluster throats,of which the distribution curves of throat size are narrow and have a strong single peak(peak ratio>30%).The pores in the type-II sandstones dominantly consist of secondary dissolution pores and intercrystalline micropores,and throats mainly occur as slice-shaped throats along cleavages between rigid grain margins and cluster throats in clay cement.The distribution curves of throat size for the type-II sandstones show a bimodal distribution with a substantial low-value region between the peaks(peak ratio<15%).Primary intergranular pores and secondary intergranular pores are mainly found in type-III samples,which are connected by various throats.The throat size distribution curves of type-III sandstones show a nearly normal distribution with low kurtosis(peak ratio<10%),and the micro-scale throat radii(>0.5μm)constitute a large proportion.From type-I to type-III sandstones,the irreducible water saturation(Swo)decreased;furthermore,the slope of the curves of Krw/Krg in two-phase saturation zone decreased and the two-phase saturation zone increased,indicating that the gas relative flow ability increased.Variations of the permeability exist in sandstones with different porethroat combination types,which indicate the type-III sandstones are better reservoirs,followed by type-II sandstones and type-I sandstones.As an important factor affecting the reservoir quality,the pore-throat combination type in sandstones is the cumulative expression of lithology and diagenetic modifications with strong heterogeneity.
基金funded by National Science and Technology Major Projects(2017ZX05009004,2016ZX05058003)Beijing Natural Science Foundation(2173061)and State Energy Center for Shale Oil Research and Development(G5800-16-ZS-KFNY005).
文摘Structure of porous media and fluid distribution in rocks can significantly affect the transport characteristics during the process of microscale tracer flow.To clarify the effect of micro heterogeneity on aqueous tracer transport,this paper demonstrates microscopic experiments at pore level and proposes an improved mathematical model for tracer transport.The visualization results show a faster tracer movement into movable water than it into bound water,and quicker occupancy in flowing pores than in storage pores caused by the difference of tracer velocity.Moreover,the proposed mathematical model includes the effects of bound water and flowing porosity by applying interstitial flow velocity expression.The new model also distinguishes flowing and storage pores,accounting for different tracer transport mechanisms(dispersion,diffusion and adsorption)in different types of pores.The resulting analytical solution better matches with tracer production data than the standard model.The residual sum of squares(RSS)from the new model is 0.0005,which is 100 times smaller than the RSS from the standard model.The sensitivity analysis indicates that the dispersion coefficient and flowing porosity shows a negative correlation with the tracer breakthrough time and the increasing slope,whereas the superficial velocity and bound water saturation show a positive correlation.
基金supported financially by the National Science and Technology Project(No.2017ZX02201001)the National Natural Science Foundation of China(No.51772193).
文摘The aim of this work is to understand the effect of a thin coating on the compressive properties of the porous metal.In our work,the uniaxial compressive behavior and the energy absorption properties of the lotus-type porous copper deposited with Ni coatings with thickness from 3.9 to 4.8μm on pore walls were investigated.It is found that the Ni coating on pore walls shows a clear enhancement effect on compressive properties of the lotus-type porous copper,in which the specific yield strength and the energy absorption per unit mass at densification strain increase from 5.27 to 7.31 MPa cm3 g-1 and from 11.50 to 18.21 J g-1 with the Ni coating,respectively.Furthermore,the enhancement appears to be insensitive to the coating thickness.It is considered that the resistance of the interface between the nickel coating and the pore walls to the dislocation slip plays an important role in the improvement on compressive properties of the lotus-type porous copper.
基金Supported by the National Natural Science Foundation (U19B6003).
文摘In this work,the Permian Longtan marine-continental transitional shale in the southeast of Sichuan Basin was taken as study object.Through petrology and geochemical analysis,lithofacies types of the marine-continental transitional shale were classified,key controlling factors of physical properties and gas content of the different shale lithofacies were analyzed.The research results show that the Longtan Formation marine-continental transitional shale in the study area has four types of lithofacies,namely,organic-lean calcareous shale,organic-lean mixed shale,organic-lean argillaceous shale,and organic-rich argillaceous shale,among which the organic-rich argillaceous shale is the most favorable lithofacies of the study area.The pore types of different lithofacies vary significantly and the clay mineral-related pore is the dominant type of the pore system in the study area.The main controlling factor of the physical properties is clay mineral content,and the most important factor affecting gas content is TOC content.Compared with marine shale,the marine-continental transitional shale has low average values,wide distribution range,and strong heterogeneity in TOC content,porosity,and pore structure parameters,but still contains some favorable layers with high physical properties and gas contents.The organic-rich clay shale deposited in tidal flat-lagoon system is most likely to form shale gas sweet spots,so it should be paid more attention in shale gas exploration.
文摘Based on scanning electron microscopy and mercury porosimmetry,a large number of experimental data of pores and pore throats of tight sandstone reservoirs are obtained,and the characteristics of pore types,capillary pressure curves and quantitative parameters of pore throats of Yanchang Formation in Huangling mining area are studied.The results show that the main reservoir space types of Yanchang Formation sandstone are primary intergranular pores and feldspar dissolution pores.The pore-throat structure is medium-small pore and thin-small throat type,and the sorting is good to medium.The mercury porosimmetry curve shows a slightly coarse-thin skew.Combining the morphological characteristics of the mercury porosimmetry capillary pressure curve and the quantitative parameter characteristics of pore throats,the Yanchang Formation s micro pore structure is divided into types I,II,III,and IV.Tight oil reservoirs with type I and II pore structure characteristics are favorable.This study has reference significance for the later evaluation of tight sandstone reservoirs in Huangling mining area.
基金supported by the National Natural Science Foundation of China(Grant No.41202103)
文摘This study analyzed the characteristics and types of the Lower Silurian shale gas reservoirs in and around Sichuan Basin through field observations, slices, Ar-ion-beam milling, scanning electron microscopy, and x-ray diffraction analysis of 25 black shale outcrops and samples. Two main types of shale gas reservoirs were determined, i.e., fractures and pores. Fractures were classified into five categories, i.e., giant, large, medium, small, and micro, according to the features of the shale gas reservoirs, effect of fracture on gas accumulation, and fracture nature. Pore types include organic matter pores, mineral pores（mineral surface, intraparticle, interparticle, and corrosional pore）, and nanofractures. The various fracture types, fracture scales, pore types, and pore sizes exert different controls over the gas storage and production capacity. Pores serve as a reservoir for gas storage and, the gas storage capacity can be determined using pores; fractures serve as pathways for gas migration, and gas production capacity can be determined using them.
基金Supported by the National Key Basic Research and Development Program(2015CB250906)National Natural Science Foundation of China(41972139,41922015)Special Funds for Basic Scientific Research in Central Universities(18CX02069A)。
文摘Aiming at the complicated problem of the genesis of high-quality hybrid sedimentary rocks,the pore-throat systems,controlling factors and fluid mobility of hybrid sedimentary rocks in the Permian Lucaogou Formation in Jimusar Sag were examined.The results show that the hybrid sedimentary rocks contain 5 types of pore-throat system,intergranular(Type A),mixed intergranular-dissolved-intercrystalline(Type B),dissolved(Type C),mixed dissolved-intercrystalline(Type D)and intercrystalline(Type E)ones.The pore-throat systems are controlled by 3 major factors,the component content and arrangement(CCA)of hybrid sedimentary rocks,sedimentary environment and diagenesis.CCA controls the matrix support mode of hybrid sedimentary rocks,and therefore controls the types and changes of pore-throat system.The sedimentary environment mainly controls the macroscopic distribution of pore-throat system,i.e.,hybrid sedimentary rocks deposited in the near source and high-energy environment are characterized by high content of coarse-grained component,granular/interbedded-support mode,and development of Type A and Type B pore-throat systems.Hybrid sedimentary rocks deposited in the medium-energy environment far from source are characterized by dolomitic/mud support mode and Type C and Type D pore-throat systems.Hybrid sedimentary rocks deposited in low-energy environment far from source have mainly Type E and Type D pore-throat systems.Diagenetic processes such as compaction and calcite cementation make the proportions of Type A and Type C pore-throat systems decrease further.In the hybrid sedimentary process of sandy-mud,pore-throat system types show a change of"A→B→C→D",in that of dolomite-sand,pore-throat system types show a change of"A→C→D→E"or"B→D→E",and in that of dolomite-mud,pore-throat system types show a change of"D→E",which are affected in details by the contents of coarse-grain component,feldspar and dolomite.The reservoir with Type A pore-throats has the best physical properties and fluid mobility,and the reservoirs with Type D and Type E pore-throats have the poorest.The movable fluid distribution is related to the matrix support mode,and the larger pores in hybrid sedimentary rocks of dolomite/mud support mode have no obvious advantage in fluid mobility.The findings of this study provide a geological basis for evaluating and building reasonable interpretation model of hybrid sedimentary rocks sweet spot.
文摘页岩气储层的气水两相渗流能力对其产能有着重要影响,但尚无直接通过测井等地球物理手段评价页岩气流动能力的方法。目前已通过岩心聚焦离子束-扫描电镜(Focused Ion Beam-Scanning Electron Microscope,FIB-SEM)扫描建立页岩无机孔隙、有机孔隙和微裂缝的三维数字岩心模型,基于流体体积法(Volume of Fluid,VOF)开展了不同润湿条件下的页岩孔缝结构气驱水渗流模拟并得到了端点含水饱和度等特征。该文基于模拟结果得到的不同孔隙类型流动能力的认识,结合大面积拼接扫描电镜(Modular Automated Processing System,MAPS)中提取的不同类型的孔隙统计,获得了每块岩心的等效流动能力。将岩心的等效流动能力与岩石物理实验和测井响应进行综合分析,提出了无量纲渗流能力的概念,建立了基于测井资料评价流动能力的模型。实际测井资料处理结果表明,所提出的评价模型具有较高的准确度,可以获得连续的页岩气流动能力剖面,可用于指导页岩气勘探开发。
