The Southern Granulite Terrane(Dharwar Craton),South India,is a key unit for understanding the origin of charnockite.New U-Pb and Lu-Hf analyses in zircon crys-tals from 16 samples representing a wide variety of litho...The Southern Granulite Terrane(Dharwar Craton),South India,is a key unit for understanding the origin of charnockite.New U-Pb and Lu-Hf analyses in zircon crys-tals from 16 samples representing a wide variety of litho-types from the quarries in Kabbaldurga reveal a complex geological history in the Archean and early Paleoprotero-zoic.Magmatic protoliths predominantly record Paleoar-chean ages between 3.4 and 3.2 Ga.Combined U-Pb and Lu-Hf signatures indicate a history of recurrent crustal anatexis,juvenile magmatic input,and felsic injections.Mesoarchaean magmatic charnockites were generated mainly from hornblende-dehydration melting of Paleoar-chaean mafic rocks.In addition,Peninsular Gneissic Com-plex of the Dharwar Craton,commonly described as TTG suites,are likely generated by melting of hydrated basalt.The new data are consistent with the idea of a convecting magmatic cycle and also support the proposal that the southern Dharwar Craton comprises a tilted cross-sec-tion through the Archaean crust.Paleoproterozoic high-temperature event is documented here as a complex unit involving juvenile mafic magmatism,granulite facies imprints and crustal anatexis as well as felsic injections,occurring within a short time period around 2.5 Ga.展开更多
Conventional borehole image log interpretation of linear fractures on volcanic rocks,represented as sinusoids on unwrapped cylinder projections,is relatively straight-forward,however,interpreting non-linear rock struc...Conventional borehole image log interpretation of linear fractures on volcanic rocks,represented as sinusoids on unwrapped cylinder projections,is relatively straight-forward,however,interpreting non-linear rock structures and complex facies geometries can be more challenging.To characterize diverse volcanic paleoenvironments related to the formation of the South American continent,this study presents a new methodology based on image logs,petrography,seismic data,and outcrop analogues.The presented methodology used pseudo-boreholes images generated from outcrop photographs with typical igneous rock features worldwide simulating 2D unwrapped cylinder projections of a 31 cm(12.25 in)diameter well.These synthetic images and standard outcrop photographs were used to define morphological patterns of igneous structures and facies for comparison with wireline borehole image logs from subsurface volcanic and subvolcanic units,providing a“visual scale”for geological evaluation of volcanic facies,significantly enhancing the identification efficiency and reliability of complex geological structures.Our analysis focused on various scales of columnar jointing and pillow lava lobes with additional examples including pahoehoe lava,ignimbrite,hyaloclastite,and various intrusive features in Campos,Santos,and Parnaíba basins in Brazil.This approach increases confidence in the interpretation of subvolcanic,subaerial,and subaqueous deposits.The image log interpretation combined with regional geological knowledge has enabled paleoenvironmental insights into the rift magmatism system related to the breakup of Gondwana with associated implications for hydrocarbon exploration.展开更多
Geomechanical properties of rocks vary across different measurement scales,primarily due to heterogeneity.Micro-scale geomechanical tests,including micro-scale“scratch tests”and nano-scale nanoindentation tests,are ...Geomechanical properties of rocks vary across different measurement scales,primarily due to heterogeneity.Micro-scale geomechanical tests,including micro-scale“scratch tests”and nano-scale nanoindentation tests,are attractive at different scales.Each method requires minimal sample volume,is low cost,and includes a relatively rapid measurement turnaround time.However,recent micro-scale test results–including scratch test results and nanoindentation results–exhibit tangible variance and uncertainty,suggesting a need to correlate mineral composition mapping to elastic modulus mapping to isolate the relative impact of specific minerals.Different research labs often utilize different interpretation methods,and it is clear that future micro-mechanical tests may benefit from standardized testing and interpretation procedures.The objectives of this study are to seek options for standardized testing and interpretation procedures,through two specific objectives:(1)Quantify chemical and physical controls on micro-mechanical properties and(2)Quantify the source of uncertainties associated with nanoindentation measurements.To reach these goals,we conducted mechanical tests on three different scales:triaxial compression tests,scratch tests,and nanoindentation tests.We found that mineral phase weight percentage is highly correlated with nanoindentation elastic modulus distribution.Finally,we conclude that nanoindentation testing is a mineralogy and microstructure-based method and generally yields significant uncertainty and overestimation.The uncertainty of the testing method is largely associated with not mapping pore space a priori.Lastly,the uncertainty can be reduced by combining phase mapping and modulus mapping with substantial and random data sampling.展开更多
The Agulhas Current is a major western boundary current flowing polewards on the southeast coast of South Africa.This analysis assesses its characteristics and suitability to generate power as a source of clean renewa...The Agulhas Current is a major western boundary current flowing polewards on the southeast coast of South Africa.This analysis assesses its characteristics and suitability to generate power as a source of clean renewable energy.On a section of coastline some 400 km long,over a period spanning more than 5 years an extensive set of current measurements was obtained.These data confirmed that south-westward currents with a speed greater than 1.2 m s^(-1)occurred over more than 60%of the recorded time;such ocean current speeds compare very favourably to winds required for energy generation.These currents occurred at the continental shelf break in water depths around 100 m,in the upper 50 m of the water column.Occasional current slowdowns and reversals did occur,with the major influence coming from‘Natal Pulses’,which are large-scale meanders in the Current that temporarily reversed the currents at the measurement sites.However,because of the surface temperature structure of the relevant water masses,such meanders can be identified in satellite imagery giving a few days advance warning of such current reversals.The characteristics of western boundary currents have been known for many years,but at Present,there is no operational system where this source of power is being utilised.It has tremendous potential for renewable energy generation,but is symptomatic of the many engineering challenges that still have to be solved to make such generation economically viable.展开更多
Due to the invisibility and complexity of the underground spaces,monitoring the propagation and filling characteristics of the grouting slurry post the water–sand mixture inrush in metal mines is challenging,which co...Due to the invisibility and complexity of the underground spaces,monitoring the propagation and filling characteristics of the grouting slurry post the water–sand mixture inrush in metal mines is challenging,which complicates engineering treatment.This research investigated the propagation law of cement-sodium silicate slurry under flowing water conditions within the caving mass of a metal mine.First,based on borehole packer test results and borehole TV images,the fractured strata before grouting were classified into four types:cavity,hidden,fissure,and complete.Second,an orthogonal experimental design was employed to evaluate the impact of four key factors—stratigraphic fragmentation,water flow rate,grouting flow rate,and water-cement ratio—on the efficacy of grouting within a caving mass at the site.The results indicate that the factors influencing grouting efficacy are ranked in the following order of importance:stratigraphic fragmentation>water flow rate>water–cement ratio>grouting flow rate.Ultimately,five propagation filling modes—pure slurry,big crack,small crack,small karst pore,and pore penetration—were identified by examining the propagation filling characteristics of slurry in rock samples,incorporating microscopic material structure analysis through scanning electron microscopy and energy spectrum analysis.The findings of this study provide valuable insights into selecting engineering treatment parameters and methodologies,serving as a reference for preventing and controlling water–sand mixture inrush in metal mines,thereby enhancing treatment efficacy and ensuring grouting success.展开更多
Successful textbooks educate generations, and in a way define generations of scientists. As science and technology advance, textbooks become old and outdated. Nevertheless, each textbook serves as a foundation for the...Successful textbooks educate generations, and in a way define generations of scientists. As science and technology advance, textbooks become old and outdated. Nevertheless, each textbook serves as a foundation for the next, and thus a series of textbooks on a particular subject reflects the evolution of concepts, methods and data on the subject. As I write this review, there are eight textbooks on petroleum geology on my bookshelf： D. Hager＇s Practical Oil Geology （1915） （the first textbook of its kind）; W.H. Emmons＇ Geology of Petroleum （1921）, Cecil Lalicker＇s Principles of Petroleum Geology （1949）; William Russell＇s Principles of Petroleum Geology （1951）; Kenneth Landes＇ Petroleum Geology （1951）; A. I. Levorsen＇s Geology of Petroleum （2nd ed., 1967）; F. K. North＇s Petroleum Geology （1985）; and Richard Selley＇s Elements of Petroleum Geology （2nd ed., 1998）. Petroleum Geoscience by Gluyas and Swarbrick is a welcome addition to this list although its authors do not mention their predecessors.展开更多
Brazilian pre-salt reservoirs are renowned for their intricate pore networks and vuggy nature,posing significant challenges in modeling and simulating fluid flow within these carbonate reservoirs.Despite possessing ex...Brazilian pre-salt reservoirs are renowned for their intricate pore networks and vuggy nature,posing significant challenges in modeling and simulating fluid flow within these carbonate reservoirs.Despite possessing excellent petrophysical properties,such as high porosity and permeability,these reservoirs typically exhibit a notably low recovery factor,sometimes falling below 10%.Previous research has indicated that various enhanced oil recovery(EOR)methods,such as water alternating gas(WAG),can substantially augment the recovery factor in pre-salt reservoirs,resulting in improvements of up to 20%.Nevertheless,the fluid flow mechanism within Brazilian carbonate reservoirs,characterized by complex pore geometry,remains unclear.Our study examines the behavior of fluid flow in a similar heterogeneous porous material,utilizing a plug sample obtained from a vugular segment of a Brazilian stromatolite outcrop,known to share analogies with certain pre-salt reservoirs.We conducted single-phase and multi-phase core flooding experiments,complemented by medical-CT scanning,to generate flow streamlines and evaluate the efficiency of water flooding.Subsequently,micro-CT scanning of the core sample was performed,and two cross-sections from horizontal and vertical plates were constructed.These cross-sections were then employed as geometries in a numerical simulator,enabling us to investigate the impact of pore geometry on fluid flow.Analysis of the pore-scale modeling and experimental data unveiled that the presence of dead-end pores and vugs results in a significant portion of the fluid remaining stagnant within these regions.Consequently,the injected fluid exhibits channeling-like behavior,leading to rapid breakthrough and low areal swept efficiency.Additionally,the numerical simulation results demonstrated that,irrespective of the size of the dead-end regions,the pressure variation within the dead-end vugs and pores is negligible.Despite the stromatolite's favorable petrophysical properties,including relatively high porosity and permeability,as well as the presence of interconnected large vugs,the recovery factor during water flooding remained low due to early breakthrough.These findings align with field data obtained from pre-salt reservoirs,providing an explanation for the observed low recovery factor during water flooding in such reservoirs.展开更多
This study investigates the impact of pore network characteristics on fluid flow through complex and heterogeneous porous media,providing insights into the factors affecting fluid propagation in such systems.Specifica...This study investigates the impact of pore network characteristics on fluid flow through complex and heterogeneous porous media,providing insights into the factors affecting fluid propagation in such systems.Specifically,high-resolution or micro X-ray computed tomography(CT)imaging techniques were utilized to examine outcrop stromatolite samples of the Lagoa Salgada,considered flow analogous to the Brazilian Pre-salt carbonate reservoirs.The petrophysical results comprised two distinct stromatolite depositional facies,the columnar and the fine-grained facies.By generating pore network model(PNM),the study quantified the relationship between key features of the porous system,including pore and throat radius,throat length,coordination number,shape factor,and pore volume.The study found that the less dense pore network of the columnar sample is typically characterized by larger pores and wider and longer throats but with a weaker connection of throats to pores.Both facies exhibited less variability in the radius of the pores and throats in comparison to throat length.Additionally,a series of core flooding experiments coupled with medical CT scanning was designed and conducted in the plug samples to assess flow propagation and saturation fields.The study revealed that the heterogeneity and presence of disconnected or dead-end pores significantly impacted the flow patterns and saturation.Two-phase flow patterns and oil saturation distribution reveal a preferential and heterogeneous displacement that mainly swept displaced fluid in some regions of plugs and bypassed it in others.The relation between saturation profiles,porosity profiles,and the number of fluid flow patterns for the samples was evident.Only for the columnar plug sample was the enhancement in recovery factor after shifting to lower salinity water injection(SB)observed.展开更多
This study discussed the division of matrix- and fracture-type shale oils in the Jiyang Depression, and proposed the concept of fracture development coefficient. The fracture development coefficient is defined as the ...This study discussed the division of matrix- and fracture-type shale oils in the Jiyang Depression, and proposed the concept of fracture development coefficient. The fracture development coefficient is defined as the ratio of fault throw to the distance between a shale oil well and the nearest fault. Based on CO_2 content, state of water, oil production and logging response of shale oil formations, the classification of shale oils was established, i.e., a fracture-type shale oil well has a fracture development coefficient greater than 0.2, while a matrix-type one has a fracture development coefficient less than 0.2. Furthermore, the key control factors of matrix- and fracture-type shale oil enrichment were analyzed using typical anatomical and statistical methods. For matrix-type shale oil enrichment, these factors are lithofacies, total organic carbon（TOC）, shale porosity and abnormal pressure; for fracture-type shale oil enrichment, they are lithofacies, extent of fracture development, and abnormal pressure. This study also first described the differences between matrix- and fracture-type shale oils. The results provide reference for the exploration of terrestrial faulted basins in eastern China.展开更多
Organic-rich lacustrine shales are widely distributed in China and have significant potential for unconventional shale gas and oil production although the primary factors controlling the deposition of lacustrine shale...Organic-rich lacustrine shales are widely distributed in China and have significant potential for unconventional shale gas and oil production although the primary factors controlling the deposition of lacustrine shale are disputed. This work clarifies the different characteristics of tectonic evolution and shale among sub-basins in the Bohai Bay Basin in eastern China as a case study by studying basal subsidence, tectonic subsidence rate, basin extensional proportions and shale chemical characteristics. The paper summarizes the correlation between structure and shale deposition, and concludes that tectonic activity is the primary controlling factor for shale development. Episodic tectonic activity controls not only the timing of shale deposition（with the greatest shale deposition occurring primarily during the peak period of basin tectonic activity） but also the spatial distribution of shale（located mainly in areas of maximum subsidence）, the migration pattern of shale（conforming to that of the basin subsidence center）, and shale strata thickness. Tectonic activity also affects the total organic carbon content and organic matter type in shale. When the tectonic activity was the most active and basal subsidence was the maximum, the total organic carbon content of the shale reached its highest value with organic matter type mainly Type I. As tectonic activity weakened, the total organic carbon content decreased, and the organic matter type changed from Type I to Type I-III.展开更多
To investigate the mechanism of the organic-matter enrichment in the Lower Longmaxi Formation shale,the geochemistry and total organic carbon(TOC)of the Longmaxi Formation black shales in the Jiaoshiba,Zhaotong,and We...To investigate the mechanism of the organic-matter enrichment in the Lower Longmaxi Formation shale,the geochemistry and total organic carbon(TOC)of the Longmaxi Formation black shales in the Jiaoshiba,Zhaotong,and Weiyuan areas of the Sichuan Basin were analyzed.Paleoproductivity proxy parameters(Babio,Siex,and Ni/Al),clastic influx proxies(TiO2 and Ti/Al),redox indices(V/Cr,Ni/Co,V/(V+Ni),and U/Th),and hydrothermal indicators(Fe,Mn,and Y concentrations;Fe/Ti ratio and a Ni-Zn-Co diagram)were employed to decipher the paleoenvironment of the Lower Longmaxi Formation shales.TiO2 and Ti/Al indicated low terrigenous detrital influx in all three areas.However,Babio,Siex,and Ni/Al indicated high productivity in the Jiaoshiba area.V/Cr,Ni/Co,and U/Th indicated higher oxygen content with larger fluctuations in the Zhaotong and Weiyuan areas.Fe,Mn,and Y concentrations and the Fe/Ti ratio implied greater active hydrothermal activity in the Weiyuan area.These heterogeneities were considered to be closely related to the paleoenvironment and paleogeography,and the large basement faults that developed during the Chuanzhong paleo-uplift could have provided vents for deep-hydrothermal-fluid upwelling.The redox indices(V/Cr,Ni/Co,and U/Th)and a paleoproductivity proxy(Ni/Al)displayed a significant correlation with the TOC,suggesting that both excellent preservation conditions and high paleoproductivity were the controlling factors for the enrichment of organic matter in the Longmaxi Formation shale.There was no obvious correlation between the clastic influx proxy(Ti/Al)and the TOC due to the extremely low supply of terrigenous debris.The hydrothermal indicator(Fe/Ti)was negatively correlated with the TOC in the Weiyuan area,indicating that hydrothermal activity may have played a negative role in the accumulation of organic matter.This study suggests that the enrichment of organic matter in the Longmaxi Formation marine shale varied according to the paleogeography and sedimentary environment.展开更多
Control of various factors, including mineral components, primary productivity and redox level, on the total organic carbon(TOC) in the lower Cambrian black shale from southeastern margin of Upper Yangtze(Taozichong, ...Control of various factors, including mineral components, primary productivity and redox level, on the total organic carbon(TOC) in the lower Cambrian black shale from southeastern margin of Upper Yangtze(Taozichong, Longbizui and Yanbei areas) is discussed in detail in this article. Mineral components in the study strata are dominated by quartz and clay minerals. Quartz in the Niutitang Formation is mainly of biogenic origin, and the content is in positive correlation with TOC, while the content of clay minerals is negatively correlated with TOC. Primary productivity, represented by the content of Mobio(biogenic molybdenum), Babio(biogenic barium) and phosphorus, is positively correlated with TOC. The main alkanes in studied samples are nCC, and odd–even priority values are closed to 1(0.73–1.13), which suggest the organic matter source was marine plankton. Element content ratios of U/Th and Ni/Co and compound ratio Pr/Ph indicate dysoxic–anoxic bottom water, with weak positive relative with TOC. In total, three main points can be drawn to explain the relationship between data and the factors affecting organic accumulation:(1) quartz-rich and clay-mineral-poor deep shelf–slope–basin environment was favorable for living organisms;(2) high productivity provided the material foundation for organic generation;(3) the redox conditions impact slightly on the content of organic matter under high productivity and dysoxic–anoxic condition.展开更多
Taking the shale of Shuijingtuo Formation of Lower Cambrian in Yichang area as the research object,the shale reservoir characteristics are comprehensively evaluated and classified by fitting regression and formula cal...Taking the shale of Shuijingtuo Formation of Lower Cambrian in Yichang area as the research object,the shale reservoir characteristics are comprehensively evaluated and classified by fitting regression and formula calculation method in this study,using laboratory testing and geophysical logging data.The results show that the interpretation data of ECS(elemental capture spectroscopy)logging has a high correlation with the measured minerals data,which can be a good method to evaluate the minerals component of the shale.The calculated content of brittle minerals at the lower part of Shuijingtuo Formation is the relatively highest,generally more than 40%,which is the most favorable segment for fracturing.The correlation coefficient between the interpretation data of CMR(combinable nuclear magnetic resonance)logging and the result of laboratory porosity test is 0.97,which can effectively and accurately evaluate the reservoir porosity.The evaluation results show that the porosity of the lower member of Shuijingtuo Formation is generally greater than 3%,while that of the upper member is generally less than 3%.The lower segment is with the relative optimal physical conditions.There is a good correlation between the acoustic logging data and the gas bearing content testing results.A gas bearing content evaluation model is established.The results show that the gas bearing content of the lower 20 m shale is generally more than 2%,indicating that the lower part is a shale gas enrichment segment.Mechanical parameters such as Young modulus,Poisson ratio and brittleness index of shale reservoir are evaluated by using the logging data of P-wave time difference and S-wave time difference.The continuous 15 m shale at the lower part is with the relatively optimal low Poisson ratio,high Young modulus and high brittleness index,developing the optimum brittle condition.Based on the evaluation and classification of above parameters,the shale is divided into three types.The TypeⅠis the optimal,mainly located at the bottom.Its thickness is 8.5 m in total.The TypeⅡmainly develops at the middle part.The TypeⅢis the worst,mainly at the upper part.展开更多
The mechanical properties such as Young's modulus, hardness and fracture toughness of Lower Silurian Longmaxi shale samples from Youyang area in southeast Chongqing, China were investigated using dot matrix nanoin...The mechanical properties such as Young's modulus, hardness and fracture toughness of Lower Silurian Longmaxi shale samples from Youyang area in southeast Chongqing, China were investigated using dot matrix nanoindentation measurements. With the help of field emission scanning electron microscope(FESEM) and energy dispersive X-ray fluorescence spectroscopy(EDS), the indentation morphology and mineral composition in indentation area were quantitatively analyzed. According to mechanical strength classification, a micromechanical model with three components was introduced and the Mori-Tanaka model was used to upscale mechanical parameters from nano-scale to centimeter-size scale, which were further compared with uniaxial compression results. The experimental results show that there is a positive linear correlation between Young's modulus and hardness and between the Young's modulus and the fracture toughness under nano-scale; the Young's modulus, hardness and fracture toughness perpendicular to the bedding are slightly lower than those parallel with the bedding. According to data statistics, the mechanical properties at the nano-scale follow Weibull distribution feature and the dispersion degree of hardness results is the highest, which is mainly due to shale anisotropy and nanoindentation projection uncertainty. Comparing the results from nanoindentation test, with those from upscaling model and uniaxial compression test shows that the mechanical parameters at the nano-scale are higher than those from upscaling model and uniaxial compression test, which proves mechanical parameters at different scales have differences. It's because the larger the core, the more pores and internal weakness it contains, the less accurate the interpreted results of mechanical parameters will be.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
基金funded by the India-Brazil bilateral co-operation Project:INT/BRAZIL/P-02/2013by Indian Statistical Institute,Geoscience Institute of São Paulo University,Brazil and Department of Geology,University of Calcutta.M.Hueck thanks FAPESP for a post-doctoral fellowship(grant 2019/06838-2).
文摘The Southern Granulite Terrane(Dharwar Craton),South India,is a key unit for understanding the origin of charnockite.New U-Pb and Lu-Hf analyses in zircon crys-tals from 16 samples representing a wide variety of litho-types from the quarries in Kabbaldurga reveal a complex geological history in the Archean and early Paleoprotero-zoic.Magmatic protoliths predominantly record Paleoar-chean ages between 3.4 and 3.2 Ga.Combined U-Pb and Lu-Hf signatures indicate a history of recurrent crustal anatexis,juvenile magmatic input,and felsic injections.Mesoarchaean magmatic charnockites were generated mainly from hornblende-dehydration melting of Paleoar-chaean mafic rocks.In addition,Peninsular Gneissic Com-plex of the Dharwar Craton,commonly described as TTG suites,are likely generated by melting of hydrated basalt.The new data are consistent with the idea of a convecting magmatic cycle and also support the proposal that the southern Dharwar Craton comprises a tilted cross-sec-tion through the Archaean crust.Paleoproterozoic high-temperature event is documented here as a complex unit involving juvenile mafic magmatism,granulite facies imprints and crustal anatexis as well as felsic injections,occurring within a short time period around 2.5 Ga.
文摘Conventional borehole image log interpretation of linear fractures on volcanic rocks,represented as sinusoids on unwrapped cylinder projections,is relatively straight-forward,however,interpreting non-linear rock structures and complex facies geometries can be more challenging.To characterize diverse volcanic paleoenvironments related to the formation of the South American continent,this study presents a new methodology based on image logs,petrography,seismic data,and outcrop analogues.The presented methodology used pseudo-boreholes images generated from outcrop photographs with typical igneous rock features worldwide simulating 2D unwrapped cylinder projections of a 31 cm(12.25 in)diameter well.These synthetic images and standard outcrop photographs were used to define morphological patterns of igneous structures and facies for comparison with wireline borehole image logs from subsurface volcanic and subvolcanic units,providing a“visual scale”for geological evaluation of volcanic facies,significantly enhancing the identification efficiency and reliability of complex geological structures.Our analysis focused on various scales of columnar jointing and pillow lava lobes with additional examples including pahoehoe lava,ignimbrite,hyaloclastite,and various intrusive features in Campos,Santos,and Parnaíba basins in Brazil.This approach increases confidence in the interpretation of subvolcanic,subaerial,and subaqueous deposits.The image log interpretation combined with regional geological knowledge has enabled paleoenvironmental insights into the rift magmatism system related to the breakup of Gondwana with associated implications for hydrocarbon exploration.
基金support of this project through the Southwest Regional Partnership on Carbon Sequestration(Grant No.DE-FC26-05NT42591)Improving Production in the Emerging Paradox Oil Play(Grant No.DE-FE0031775).
文摘Geomechanical properties of rocks vary across different measurement scales,primarily due to heterogeneity.Micro-scale geomechanical tests,including micro-scale“scratch tests”and nano-scale nanoindentation tests,are attractive at different scales.Each method requires minimal sample volume,is low cost,and includes a relatively rapid measurement turnaround time.However,recent micro-scale test results–including scratch test results and nanoindentation results–exhibit tangible variance and uncertainty,suggesting a need to correlate mineral composition mapping to elastic modulus mapping to isolate the relative impact of specific minerals.Different research labs often utilize different interpretation methods,and it is clear that future micro-mechanical tests may benefit from standardized testing and interpretation procedures.The objectives of this study are to seek options for standardized testing and interpretation procedures,through two specific objectives:(1)Quantify chemical and physical controls on micro-mechanical properties and(2)Quantify the source of uncertainties associated with nanoindentation measurements.To reach these goals,we conducted mechanical tests on three different scales:triaxial compression tests,scratch tests,and nanoindentation tests.We found that mineral phase weight percentage is highly correlated with nanoindentation elastic modulus distribution.Finally,we conclude that nanoindentation testing is a mineralogy and microstructure-based method and generally yields significant uncertainty and overestimation.The uncertainty of the testing method is largely associated with not mapping pore space a priori.Lastly,the uncertainty can be reduced by combining phase mapping and modulus mapping with substantial and random data sampling.
文摘The Agulhas Current is a major western boundary current flowing polewards on the southeast coast of South Africa.This analysis assesses its characteristics and suitability to generate power as a source of clean renewable energy.On a section of coastline some 400 km long,over a period spanning more than 5 years an extensive set of current measurements was obtained.These data confirmed that south-westward currents with a speed greater than 1.2 m s^(-1)occurred over more than 60%of the recorded time;such ocean current speeds compare very favourably to winds required for energy generation.These currents occurred at the continental shelf break in water depths around 100 m,in the upper 50 m of the water column.Occasional current slowdowns and reversals did occur,with the major influence coming from‘Natal Pulses’,which are large-scale meanders in the Current that temporarily reversed the currents at the measurement sites.However,because of the surface temperature structure of the relevant water masses,such meanders can be identified in satellite imagery giving a few days advance warning of such current reversals.The characteristics of western boundary currents have been known for many years,but at Present,there is no operational system where this source of power is being utilised.It has tremendous potential for renewable energy generation,but is symptomatic of the many engineering challenges that still have to be solved to make such generation economically viable.
基金The National Natural Science Foundation of China,Grant/Award Number:42130706。
文摘Due to the invisibility and complexity of the underground spaces,monitoring the propagation and filling characteristics of the grouting slurry post the water–sand mixture inrush in metal mines is challenging,which complicates engineering treatment.This research investigated the propagation law of cement-sodium silicate slurry under flowing water conditions within the caving mass of a metal mine.First,based on borehole packer test results and borehole TV images,the fractured strata before grouting were classified into four types:cavity,hidden,fissure,and complete.Second,an orthogonal experimental design was employed to evaluate the impact of four key factors—stratigraphic fragmentation,water flow rate,grouting flow rate,and water-cement ratio—on the efficacy of grouting within a caving mass at the site.The results indicate that the factors influencing grouting efficacy are ranked in the following order of importance:stratigraphic fragmentation>water flow rate>water–cement ratio>grouting flow rate.Ultimately,five propagation filling modes—pure slurry,big crack,small crack,small karst pore,and pore penetration—were identified by examining the propagation filling characteristics of slurry in rock samples,incorporating microscopic material structure analysis through scanning electron microscopy and energy spectrum analysis.The findings of this study provide valuable insights into selecting engineering treatment parameters and methodologies,serving as a reference for preventing and controlling water–sand mixture inrush in metal mines,thereby enhancing treatment efficacy and ensuring grouting success.
文摘Successful textbooks educate generations, and in a way define generations of scientists. As science and technology advance, textbooks become old and outdated. Nevertheless, each textbook serves as a foundation for the next, and thus a series of textbooks on a particular subject reflects the evolution of concepts, methods and data on the subject. As I write this review, there are eight textbooks on petroleum geology on my bookshelf： D. Hager＇s Practical Oil Geology （1915） （the first textbook of its kind）; W.H. Emmons＇ Geology of Petroleum （1921）, Cecil Lalicker＇s Principles of Petroleum Geology （1949）; William Russell＇s Principles of Petroleum Geology （1951）; Kenneth Landes＇ Petroleum Geology （1951）; A. I. Levorsen＇s Geology of Petroleum （2nd ed., 1967）; F. K. North＇s Petroleum Geology （1985）; and Richard Selley＇s Elements of Petroleum Geology （2nd ed., 1998）. Petroleum Geoscience by Gluyas and Swarbrick is a welcome addition to this list although its authors do not mention their predecessors.
基金the support of EPIC-Energy Production Innovation Center,hosted by the University of Campinas(UNICAMP)sponsored by FAPESP-Sao Paulo Research Foundation(2017/15736e3 process).
文摘Brazilian pre-salt reservoirs are renowned for their intricate pore networks and vuggy nature,posing significant challenges in modeling and simulating fluid flow within these carbonate reservoirs.Despite possessing excellent petrophysical properties,such as high porosity and permeability,these reservoirs typically exhibit a notably low recovery factor,sometimes falling below 10%.Previous research has indicated that various enhanced oil recovery(EOR)methods,such as water alternating gas(WAG),can substantially augment the recovery factor in pre-salt reservoirs,resulting in improvements of up to 20%.Nevertheless,the fluid flow mechanism within Brazilian carbonate reservoirs,characterized by complex pore geometry,remains unclear.Our study examines the behavior of fluid flow in a similar heterogeneous porous material,utilizing a plug sample obtained from a vugular segment of a Brazilian stromatolite outcrop,known to share analogies with certain pre-salt reservoirs.We conducted single-phase and multi-phase core flooding experiments,complemented by medical-CT scanning,to generate flow streamlines and evaluate the efficiency of water flooding.Subsequently,micro-CT scanning of the core sample was performed,and two cross-sections from horizontal and vertical plates were constructed.These cross-sections were then employed as geometries in a numerical simulator,enabling us to investigate the impact of pore geometry on fluid flow.Analysis of the pore-scale modeling and experimental data unveiled that the presence of dead-end pores and vugs results in a significant portion of the fluid remaining stagnant within these regions.Consequently,the injected fluid exhibits channeling-like behavior,leading to rapid breakthrough and low areal swept efficiency.Additionally,the numerical simulation results demonstrated that,irrespective of the size of the dead-end regions,the pressure variation within the dead-end vugs and pores is negligible.Despite the stromatolite's favorable petrophysical properties,including relatively high porosity and permeability,as well as the presence of interconnected large vugs,the recovery factor during water flooding remained low due to early breakthrough.These findings align with field data obtained from pre-salt reservoirs,providing an explanation for the observed low recovery factor during water flooding in such reservoirs.
基金the support of EPIC—Energy Production Innovation Center,hosted by the University of Campinas(UNICAMP)sponsored by FAPESP—Sao Paulo Research Foundation(2017/15736—3 process)+2 种基金the support and funding from Equinor Brazil and the support of ANP(Brazil's National Oil,Natural Gas and Biofuels Agency)through the R&D levy regulationthe Center of Energy and Petroleum Studies(CEPETRO)the School of Mechanical Engineering(FEM)。
文摘This study investigates the impact of pore network characteristics on fluid flow through complex and heterogeneous porous media,providing insights into the factors affecting fluid propagation in such systems.Specifically,high-resolution or micro X-ray computed tomography(CT)imaging techniques were utilized to examine outcrop stromatolite samples of the Lagoa Salgada,considered flow analogous to the Brazilian Pre-salt carbonate reservoirs.The petrophysical results comprised two distinct stromatolite depositional facies,the columnar and the fine-grained facies.By generating pore network model(PNM),the study quantified the relationship between key features of the porous system,including pore and throat radius,throat length,coordination number,shape factor,and pore volume.The study found that the less dense pore network of the columnar sample is typically characterized by larger pores and wider and longer throats but with a weaker connection of throats to pores.Both facies exhibited less variability in the radius of the pores and throats in comparison to throat length.Additionally,a series of core flooding experiments coupled with medical CT scanning was designed and conducted in the plug samples to assess flow propagation and saturation fields.The study revealed that the heterogeneity and presence of disconnected or dead-end pores significantly impacted the flow patterns and saturation.Two-phase flow patterns and oil saturation distribution reveal a preferential and heterogeneous displacement that mainly swept displaced fluid in some regions of plugs and bypassed it in others.The relation between saturation profiles,porosity profiles,and the number of fluid flow patterns for the samples was evident.Only for the columnar plug sample was the enhancement in recovery factor after shifting to lower salinity water injection(SB)observed.
基金supported by the National Basic Research Program of China(973 Program)(Grant No2014CB239104)
文摘This study discussed the division of matrix- and fracture-type shale oils in the Jiyang Depression, and proposed the concept of fracture development coefficient. The fracture development coefficient is defined as the ratio of fault throw to the distance between a shale oil well and the nearest fault. Based on CO_2 content, state of water, oil production and logging response of shale oil formations, the classification of shale oils was established, i.e., a fracture-type shale oil well has a fracture development coefficient greater than 0.2, while a matrix-type one has a fracture development coefficient less than 0.2. Furthermore, the key control factors of matrix- and fracture-type shale oil enrichment were analyzed using typical anatomical and statistical methods. For matrix-type shale oil enrichment, these factors are lithofacies, total organic carbon（TOC）, shale porosity and abnormal pressure; for fracture-type shale oil enrichment, they are lithofacies, extent of fracture development, and abnormal pressure. This study also first described the differences between matrix- and fracture-type shale oils. The results provide reference for the exploration of terrestrial faulted basins in eastern China.
基金supported by China Postdoctoral Science Foundation (No. 2013M530680)the foundation of the Key Laboratory of Tectonics and Petroleum Resources (China University of Geosciences, Wuhan) of the Ministry of Education (No.TPR-2010-12)
文摘Organic-rich lacustrine shales are widely distributed in China and have significant potential for unconventional shale gas and oil production although the primary factors controlling the deposition of lacustrine shale are disputed. This work clarifies the different characteristics of tectonic evolution and shale among sub-basins in the Bohai Bay Basin in eastern China as a case study by studying basal subsidence, tectonic subsidence rate, basin extensional proportions and shale chemical characteristics. The paper summarizes the correlation between structure and shale deposition, and concludes that tectonic activity is the primary controlling factor for shale development. Episodic tectonic activity controls not only the timing of shale deposition（with the greatest shale deposition occurring primarily during the peak period of basin tectonic activity） but also the spatial distribution of shale（located mainly in areas of maximum subsidence）, the migration pattern of shale（conforming to that of the basin subsidence center）, and shale strata thickness. Tectonic activity also affects the total organic carbon content and organic matter type in shale. When the tectonic activity was the most active and basal subsidence was the maximum, the total organic carbon content of the shale reached its highest value with organic matter type mainly Type I. As tectonic activity weakened, the total organic carbon content decreased, and the organic matter type changed from Type I to Type I-III.
基金supported by U.S. National Science Foundation (No. 1661733)the National Science and Technology Major Project of China (No. 2017ZX05005002-008)+3 种基金the National Natural Science Foundation of China (No. 41772121)the National Natural Science Foundation of China (No. 41630312)the Open Fund of the Sinopec Key Laboratory of Shale Oil/Gas Exploration and Production Technology and the State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development (No. GSYKY-B09-33)Department of Geology, Northwest University, China, for the financial support given to the first author
文摘To investigate the mechanism of the organic-matter enrichment in the Lower Longmaxi Formation shale,the geochemistry and total organic carbon(TOC)of the Longmaxi Formation black shales in the Jiaoshiba,Zhaotong,and Weiyuan areas of the Sichuan Basin were analyzed.Paleoproductivity proxy parameters(Babio,Siex,and Ni/Al),clastic influx proxies(TiO2 and Ti/Al),redox indices(V/Cr,Ni/Co,V/(V+Ni),and U/Th),and hydrothermal indicators(Fe,Mn,and Y concentrations;Fe/Ti ratio and a Ni-Zn-Co diagram)were employed to decipher the paleoenvironment of the Lower Longmaxi Formation shales.TiO2 and Ti/Al indicated low terrigenous detrital influx in all three areas.However,Babio,Siex,and Ni/Al indicated high productivity in the Jiaoshiba area.V/Cr,Ni/Co,and U/Th indicated higher oxygen content with larger fluctuations in the Zhaotong and Weiyuan areas.Fe,Mn,and Y concentrations and the Fe/Ti ratio implied greater active hydrothermal activity in the Weiyuan area.These heterogeneities were considered to be closely related to the paleoenvironment and paleogeography,and the large basement faults that developed during the Chuanzhong paleo-uplift could have provided vents for deep-hydrothermal-fluid upwelling.The redox indices(V/Cr,Ni/Co,and U/Th)and a paleoproductivity proxy(Ni/Al)displayed a significant correlation with the TOC,suggesting that both excellent preservation conditions and high paleoproductivity were the controlling factors for the enrichment of organic matter in the Longmaxi Formation shale.There was no obvious correlation between the clastic influx proxy(Ti/Al)and the TOC due to the extremely low supply of terrigenous debris.The hydrothermal indicator(Fe/Ti)was negatively correlated with the TOC in the Weiyuan area,indicating that hydrothermal activity may have played a negative role in the accumulation of organic matter.This study suggests that the enrichment of organic matter in the Longmaxi Formation marine shale varied according to the paleogeography and sedimentary environment.
基金supported by the National Natural Science Foundation Research (Grant 41672130, 41728004)the National Key S&T Special Projects (Grant 2016ZX05061-003-001)+1 种基金the National Postdoctoral Innovative Talent Support Program (Grant BX201700289)China Postdoctoral Science Foundation (Grant 2017M620296)
文摘Control of various factors, including mineral components, primary productivity and redox level, on the total organic carbon(TOC) in the lower Cambrian black shale from southeastern margin of Upper Yangtze(Taozichong, Longbizui and Yanbei areas) is discussed in detail in this article. Mineral components in the study strata are dominated by quartz and clay minerals. Quartz in the Niutitang Formation is mainly of biogenic origin, and the content is in positive correlation with TOC, while the content of clay minerals is negatively correlated with TOC. Primary productivity, represented by the content of Mobio(biogenic molybdenum), Babio(biogenic barium) and phosphorus, is positively correlated with TOC. The main alkanes in studied samples are nCC, and odd–even priority values are closed to 1(0.73–1.13), which suggest the organic matter source was marine plankton. Element content ratios of U/Th and Ni/Co and compound ratio Pr/Ph indicate dysoxic–anoxic bottom water, with weak positive relative with TOC. In total, three main points can be drawn to explain the relationship between data and the factors affecting organic accumulation:(1) quartz-rich and clay-mineral-poor deep shelf–slope–basin environment was favorable for living organisms;(2) high productivity provided the material foundation for organic generation;(3) the redox conditions impact slightly on the content of organic matter under high productivity and dysoxic–anoxic condition.
基金supported by the Fundamental and Commonweal Geological Survey of Oil and Gas of China(Nos.DD20179615 and DD20160194)the National Science and Technology Major Project of China(No.2016ZX05034001‐002).
文摘Taking the shale of Shuijingtuo Formation of Lower Cambrian in Yichang area as the research object,the shale reservoir characteristics are comprehensively evaluated and classified by fitting regression and formula calculation method in this study,using laboratory testing and geophysical logging data.The results show that the interpretation data of ECS(elemental capture spectroscopy)logging has a high correlation with the measured minerals data,which can be a good method to evaluate the minerals component of the shale.The calculated content of brittle minerals at the lower part of Shuijingtuo Formation is the relatively highest,generally more than 40%,which is the most favorable segment for fracturing.The correlation coefficient between the interpretation data of CMR(combinable nuclear magnetic resonance)logging and the result of laboratory porosity test is 0.97,which can effectively and accurately evaluate the reservoir porosity.The evaluation results show that the porosity of the lower member of Shuijingtuo Formation is generally greater than 3%,while that of the upper member is generally less than 3%.The lower segment is with the relative optimal physical conditions.There is a good correlation between the acoustic logging data and the gas bearing content testing results.A gas bearing content evaluation model is established.The results show that the gas bearing content of the lower 20 m shale is generally more than 2%,indicating that the lower part is a shale gas enrichment segment.Mechanical parameters such as Young modulus,Poisson ratio and brittleness index of shale reservoir are evaluated by using the logging data of P-wave time difference and S-wave time difference.The continuous 15 m shale at the lower part is with the relatively optimal low Poisson ratio,high Young modulus and high brittleness index,developing the optimum brittle condition.Based on the evaluation and classification of above parameters,the shale is divided into three types.The TypeⅠis the optimal,mainly located at the bottom.Its thickness is 8.5 m in total.The TypeⅡmainly develops at the middle part.The TypeⅢis the worst,mainly at the upper part.
基金Supported by the National Natural Science Foundation of China(51704324,41728004,U1762213)China National Science and Technology Major Project(2016ZX05061)
文摘The mechanical properties such as Young's modulus, hardness and fracture toughness of Lower Silurian Longmaxi shale samples from Youyang area in southeast Chongqing, China were investigated using dot matrix nanoindentation measurements. With the help of field emission scanning electron microscope(FESEM) and energy dispersive X-ray fluorescence spectroscopy(EDS), the indentation morphology and mineral composition in indentation area were quantitatively analyzed. According to mechanical strength classification, a micromechanical model with three components was introduced and the Mori-Tanaka model was used to upscale mechanical parameters from nano-scale to centimeter-size scale, which were further compared with uniaxial compression results. The experimental results show that there is a positive linear correlation between Young's modulus and hardness and between the Young's modulus and the fracture toughness under nano-scale; the Young's modulus, hardness and fracture toughness perpendicular to the bedding are slightly lower than those parallel with the bedding. According to data statistics, the mechanical properties at the nano-scale follow Weibull distribution feature and the dispersion degree of hardness results is the highest, which is mainly due to shale anisotropy and nanoindentation projection uncertainty. Comparing the results from nanoindentation test, with those from upscaling model and uniaxial compression test shows that the mechanical parameters at the nano-scale are higher than those from upscaling model and uniaxial compression test, which proves mechanical parameters at different scales have differences. It's because the larger the core, the more pores and internal weakness it contains, the less accurate the interpreted results of mechanical parameters will be.
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.
