Logging data and its interpretation results are one of the most important basic data for understanding reservoirs and oilfield development. Standardized and unified logging interpretation results play a decisive role ...Logging data and its interpretation results are one of the most important basic data for understanding reservoirs and oilfield development. Standardized and unified logging interpretation results play a decisive role in fine reservoir description and reservoir development. Aiming at the problem of the conflict between the development effect and the initial interpretation result of Yan 9 reservoir in Hujianshan area of Ordos Basin, by combining the current well production performance, logging, oil test, production test and other data, on the basis of making full use of core, coring, logging, thin section analysis and high pressure mercury injection data, the four characteristics of reservoir are analyzed, a more scientific and reasonable calculation model of reservoir logging parameters is established, and the reserves are recalculated after the second interpretation standard of logging is determined. The research improves the accuracy of logging interpretation and provides an effective basis for subsequent production development and potential horizons.展开更多
1 Introduction Petroleum accumulations from the Earth's crust can be grouped into conventional and unconventional ones. The history of the world's petroleum exploration is a history from the exploration of conventio...1 Introduction Petroleum accumulations from the Earth's crust can be grouped into conventional and unconventional ones. The history of the world's petroleum exploration is a history from the exploration of conventional accumulations to that of unconventional ones.展开更多
Based on the analysis of a large number of core samples, logging results, logging interpretation data and dynamic data in the study area, the characteristics of Chang 6 reservoir in Zhouguan area of Baihe area are stu...Based on the analysis of a large number of core samples, logging results, logging interpretation data and dynamic data in the study area, the characteristics of Chang 6 reservoir in Zhouguan area of Baihe area are studied, and the favorable reservoir areas in the study area are predicted. The results show that the lithology of Chang 6 reservoir is mainly light gray and gray fine-grained to very fine-grained feldspar lithic sandstone. The pore types are mainly residual intergranular pores and feldspar dissolved pores, including debris dissolved pores and microfractures. The porosity and permeability values are low, which belongs to low porosity-low permeability and ultra-low permeability reservoirs. According to the reservoir distribution characteristics and related data, the Chang 6 reservoir in the study area is divided into two types, mainly Class II and Class III reservoirs. The comprehensive evaluation predicts that the spatial distribution of the favorable area of Chang 6 reservoir is not uniform, but the distribution area is large, which has broad exploration and development value, and provides the necessary conditions for the distribution study of the favorable oil-bearing zone in this area and the preparation for the next exploration and development.展开更多
Oil saturation was an important parameter of reservoir evaluation, which had important guiding significance for oilfield development. In this paper, the oil saturation of tight oil in G area was studied, and the origi...Oil saturation was an important parameter of reservoir evaluation, which had important guiding significance for oilfield development. In this paper, the oil saturation of tight oil in G area was studied, and the original oil saturation of the study area was studied by using the comprehensive experimental method. The original oil saturation of tight oil in the study area was determined by J function method, rock electricity method and oil-based mud coring method. The results showed that through the comparison of three experimental methods, it could be concluded that the J function method leads to the low value of oil saturation in the study area. The oil-based mud coring method was more suitable for the determination of oil saturation in this area than the other two methods because it needs to meet too many conditions and the calculation results were also low. G area was located in Qili Village, Ordos Basin.展开更多
A new classification of petroleum systems(PSs) based on reservoir qualities is proposed. We classify PSs into the following three basic types:(1) source-rock petroleum system(SPS);(2) tight-reservoir or tight petroleu...A new classification of petroleum systems(PSs) based on reservoir qualities is proposed. We classify PSs into the following three basic types:(1) source-rock petroleum system(SPS);(2) tight-reservoir or tight petroleum system(TPS);and(3) conventional-reservoir or conventional petroleum system(CPS). The CPS is a PS in which hydrocarbons accumulate in conventional reservoirs, and all the essential elements and processes are significant and indispensable. Oil and gas accumulations are geographically discrete and therefore exist as discontinuous accumulations. The TPS is a PS where hydrocarbons accumulate in tight reservoirs and the source rock, reservoir, seal, migration, and trap are also indispensable,but the traps are mostly non-anticlinal and the accumulations are primarily quasi-continuous and secondarily discontinuous. The SPS is a PS where both hydrocarbon generation and accumulation occurred in source rocks and traps and migration are unnecessary or inconsequential; the hydrocarbon distribution is extensive and continuous and has no distinct boundaries. The aforementioned three PSs can be derived from a common hydrocarbon source kitchen and are closely linked in terms of their formation and distribution. Therefore, to maximize the exploration efficiency, a comprehensive study and different strategies are needed by considering the SPS, TPS, and CPS as parts of a greater whole.展开更多
Carbonate concretions are conspicuous in organic-rich shales and are generally related to decomposition of organic matter.The black shales from the Chang 7 Member of the Upper Triassic Yanchang Formation of the southe...Carbonate concretions are conspicuous in organic-rich shales and are generally related to decomposition of organic matter.The black shales from the Chang 7 Member of the Upper Triassic Yanchang Formation of the southern Ordos Basin host abundant carbonate concretions,which provide a unique record of depositional and early diagenetic conditions of the paleo-lake sediments.However,little attention has been given to the genesis and growth processes of the concretions in these lacustrine petroleum source rocks.New petrographic observations and geochemical analysis show that the concretions are composed of calcite,phosphate fossil fragments,K-NH4-feldspar,quartz,bitumen,and minor Fe-dolomite.Phosphate minerals,mainly carbonate fluorapatite(CFA),show pervasive replacement by calcite,most of which contains phosphorus,ranging in concentration from 0.26 to 2.35 wt%.This suggests that the phosphate minerals are the precursors for concretion growth.Positiveδ13C(+5.6 to+12.4‰V-PDB)signatures and the absence of pyrite indicate that microbial methanogenesis was the dominant driver for concretion growth,rather than bacterial sulfate reduction.Quartz,bitumen,and Fe-dolomite are the last cements that occurred,at deep burial depths and high temperatures.The formation of phosphate minerals might have been induced by upwelling of phosphate-enriched deep water in the Late Triassic paleo-lake,which promoted phytoplankton blooms and further enrichment of organic matter.Extremely slow sedimentation rates of fine-grained detrital minerals,relative to dead organism accumulation,led to the high permeabilities of the organic-rich sediments and rapid concretion growth during shallow burial.The close association of phosphate-bearing carbonate concretions and organic-rich shales reflects that upwelling played a critical role in the formation of the high-quality petroleum source rocks in the Triassic paleo-Ordos lake.展开更多
A new method is proposed to analyze the pore-scale mechanisms and characterization of light oil storage in shale nanopores,which is based on the Hydrocarbon Vapor Adsorption(HVA)and Pore Calculation Model(PCM).First,t...A new method is proposed to analyze the pore-scale mechanisms and characterization of light oil storage in shale nanopores,which is based on the Hydrocarbon Vapor Adsorption(HVA)and Pore Calculation Model(PCM).First,the basic principle of the HVA-PCM method is introduced,and the experimental/mathematical analysis processes are given.Then,the HVA-PCM method is applied to shale samples to analyze the mechanisms and characterization of light oil storage in shale nanopores.The results provide insights into the pore-scale oil storage mechanisms,oil storage structure,oil film thickness,oil distribution within different sized pores,and the oil storage state.Finally,the advantages and limitations of the HVA-PCM method are discussed,and suggestions for further improvement are proposed.Overall,the HVA-PCM method is a powerful tool for extracting quantitative information on the light oil storage in shale nanopores.展开更多
It is difficult to obtain reliable shear strength parameters for the stability analysis and evaluation of high loess slopes.Hence,this paper determines slope elements and physical parameter of 79 slopes with heights o...It is difficult to obtain reliable shear strength parameters for the stability analysis and evaluation of high loess slopes.Hence,this paper determines slope elements and physical parameter of 79 slopes with heights of[40,120]m based on the measured loess slopes in the Ganquan and Tonghuang subregions of northern Shaanxi Province,China.In the limit state of the loess slope(stability factor Fs is 1.0),a fitting equation for the slope height and width is established.Then,the model is developed by stability analysis software-SLOPE/W,and the comprehensive shear strength parameters corresponding to different slope heights of the high slope in the study area are obtained by inversion using the Morgenstern-Price method.The results show that when the height of the slope increases,the cohesion c increases in the soil,and the internal friction angle j decreases.This change is consistent with the characteristics reflected in the composition and physical properties of the slopes,and the comprehensive strength parametric curves are very similar between the Ganquan subregion and the Tonghuang subregion.A landslide that occurred in Miaodian-zaitou of Jingyang County,Shaanxi Province,is selected to verify this inversion method,and the results show that the calculated shear strength parameters of the inversion are consistent with the measured value of the actual slope.展开更多
The Triassic strata in the Turpan-Hami Basin potentially chronicled the missing sedimentary record of Indosinian tectonic evolution in the Eastern Tianshan.In this study,we conducted detrital zircon U-Pb geochronologi...The Triassic strata in the Turpan-Hami Basin potentially chronicled the missing sedimentary record of Indosinian tectonic evolution in the Eastern Tianshan.In this study,we conducted detrital zircon U-Pb geochronological analyses on subsurface Triassic samples collected from the Turpan-Hami Basin to unravel sedimentary response of Indosinian tectonic reactivation and its geodynamics.The detrital zircon age spectra of the Triassic samples are quite different,reflecting significant provenance variability.The zircon grains in the Lower Triassic sample were mainly from the Central Tianshan,while the Jueluotag acted as a minor provenance.By contrast,the Late Paleozoic rocks in Jueluotag act as the main provenance for the Middle-Upper Triassic samples,while the Central Tianshan acted as a minor provenance.Furthermore,zircon grains in the Middle Triassic sample were mainly from the Permian rocks in Jueluotag,while Indosinian strike-slipdriven rapid exhumation brought deeper Carboniferous rocks of Jueluotag as an important age population for the Upper Triassic sample.The inter-sample variability of age spectra of the Triassic samples provides sedimentary evidence for Indosinian tectonic reactivation in the Eastern Tianshan and its periphery,which could be attributed to differential exhumation of different sources driven by coeval strike-slip tectonics along deep faults.The Indosinian tectonic behavior in the Eastern Tianshan,which is characterized by partial melting of the pre-thickened crust and strike-slip deformation,acted as a far-field respond to the coeval continental accretion occurring along the southern Eurasian margin.Additionally,our new detrital zircon data,together with previously published data in the Turpan-Hami Basin,demonstrate that there are significant changes in source-to-sink system from the Permian to the Triassic,suggesting that the Permian-Triassic unconformity in the Eastern Tianshan and its periphery was generated by Late Permian-Early Triassic tectonic contraction and inversion rather than an increasingly arid climate.展开更多
The Shanxi Formation(Shan 1 and Shan 2 Members)shales show good prospects in shale gas development in the Yan'an area of Ordos Basin.Based on the simulation experiment of hydrocarbon generation of low maturity sha...The Shanxi Formation(Shan 1 and Shan 2 Members)shales show good prospects in shale gas development in the Yan'an area of Ordos Basin.Based on the simulation experiment of hydrocarbon generation of low maturity shale samples,the hydrocarbon generation characteristics of shale samples was studied systematically.Then,combined with the geochemical analysis of shale and gas generation simulation,shale gas potential was evaluated.The results reveal that Shan 1 and Shan 2 shale samples are favorable for shale gas enrichment by and large,with C_(1)-C_(5) maximum yields of 146.96-160.83 mg/g TOC and 148.48-148.67 mg/g TOC respectively at a heat rate of 20℃/h and 2℃/h.The Shan 1 and Shan 2 shales are basically the same in terms of organic carbon production potential of each unit.The carbon isotopic composition of alkane gas reveals that heteroatomic compounds(NSOs)cracking is an important mechanism for shale gas generation of Shanxi Formation shales,and conducive to gas generation at highto over-mature stages.Given thermal history and kinetic parameters of hydrocarbon generation,the shales of Shanxi Formation reached the maximum gas production potential in the Late Cretaceous,with a maximum yield of 160.3 mg/g TOC under present geological conditions.During geological history,the Shanxi Formation shales went through high-to over-maturity evolution,mainly producing dry gas,and their gas generation capacity was controlled by the organic matter abundance and cracking capacity.The gas generation potential of Shan 2 shale is higher than that of Shan 1,due to its higher TOC.展开更多
Shale porosity measurements have crucial scientific and economical applications in unconventionalpetroleum systems. As a standard technique, liquid saturation methods, including water saturation (WS)and oil saturation...Shale porosity measurements have crucial scientific and economical applications in unconventionalpetroleum systems. As a standard technique, liquid saturation methods, including water saturation (WS)and oil saturation (OS), have been widely used to measure the porosity of many rock types. For clay-richshale reservoirs with high organic matter content, it is well known that the WS method may cause clayswelling and induce structural changes in the pore system. The OS method affects the accuracy ofporosity measurements because of some of the oil being dissolved by kerogen within the shale;however,this has not received sufficient research attention. In this study, we compare the previously reported andnewly tested OS porosities with helium (He) expansion porosity. Results show that OS porosity generallyexceeds the He porosity. Furthermore, the higher the total organic carbon (TOC) content and lower thematurity of shale, the greater the difference between the OS and helium porosities. When using the OSmethod, the effect of kerogen-dissolved oil causes an overestimation of the shale porosity by ~30%. To thebest of our knowledge, this is the first time to note the kerogen-dissolve oil effects on OS porosity. Herein,we propose a new, simple, and effective correction method for estimating OS porosity that involvessubtracting the kerogen-dissolved oil content from raw OS porosity. In addition, the quantification modelof kerogen-dissolved oil capacity is established, taking into account the abundance and maturity oforganic matter. Taking the He porosity as the benchmark, the absolute error of the corrected OS porositydoes not exceed 1% and the average relative error is only ~10%. The obtained results can help improve theaccuracy of shale porosity evaluation methods.展开更多
The study of pore structure requires consideration of important factors including pore throat size,pore radius composition,and pore-throat configuration.As the nuclear magnetic resonance(NMR)experimental results conta...The study of pore structure requires consideration of important factors including pore throat size,pore radius composition,and pore-throat configuration.As the nuclear magnetic resonance(NMR)experimental results contain rich information about pore structures and fluid occurrence states,this study investigated the pore structures of the tight sandstone reservoirs of the Shanxi Formation in the Daning-Jixian area,eastern Ordos Basin.Firstly,by making the inverse cumulative curve of the NMR T2 spectrum coincide with the capillary pressure curves which were obtained by the mercury injection capillary pressure(MICP)technique,this study derived a conversion coefficient that can be used to convert the NMR T2 spectrum into the pore throat radius distribution curves based on the NMR experimental results.Subsequently,we determined the pore radius intervals corresponding to irreducible water distribution using the NMR-derived pore radius distribution curves.Finally,the NMR T2 distribution curves based on the fractal theory were analyzed and the relationships between fractal dimensions and parameters,including permeability,porosity,reservoir quality index(RQI),flow zone indicator(FZI),irreducible water saturation,RT35,and RT50,were also discussed.The NMR-derived pore throat radius distribution curves of the study area are mainly unimodal,with some curves showing slightly bimodal distributions.The irreducible water mainly occurs in small pores with a pore radius less than 100 nm.As the permeability decreases,the contribution rate of small pores to the irreducible water gradually increases.The NMR-based fractal dimensions of pores show a two-segment distribution.Small pores have small fractal dimensions and are evenly distributed,while large pores have large fractal dimensions and complex pore structures.The fractal dimension of large pores(Dmax)is poorly correlated with porosity but strongly correlated with FZI,RQI,RT35,and RT50.These results indicate that large pores are the main pore zones that determine the seepage capacity of the reservoirs.Additionally,there is a certain correlation between Dmax and the irreducible water saturation.展开更多
Based on the extensive studies of conventional and unconventional hydrocarbon accumulations,the concept,classification and formation as well as distribution of petroleum reservoirs are discussed.The revised concept de...Based on the extensive studies of conventional and unconventional hydrocarbon accumulations,the concept,classification and formation as well as distribution of petroleum reservoirs are discussed.The revised concept defined the petroleum reservoir as a continuous hydrocarbon accumulation in a single or a set of reservoirs with an independent or uniform pressure system.In terms of the pattern of hydrocarbon accumulation and distribution,the hydrocarbon accumulations are classified into three basic types,i.e.,the continuous accumulation,the quasi-continuous accumulation and the discontinuous accumulation.The hydrocarbon accumulation was demonstrated as a process from continuous accumulation to discontinuous accumulation,and therefore these three basic types of hydrocarbon accumulations were identified.The continuous hydrocarbon accumulation is principally formed in source rocks,and typical examples are shale hydrocarbon reservoirs and coal-bed methane reservoirs;it is mainly characterized by tight-ultra tight reservoirs with permeability of nanodarcy to millidarcy;the hydrocarbons occurred in free,adsorbed or dissolved state;a continuous accumulation comprises actually only a single reservoir,and hydrocarbons are extensively and continuously distributed within the scope of effective source rocks;the accumulation has neither defined boundaries nor bottom or edge water;oil and gas mainly accumulate in situ or near the generation of hydrocarbons with no prominent migration;this hydrocarbon accumulation process is basically not controlled by traps.The quasicontinuous hydrocarbon accumulation mostly occurs in the tight reservoirs adjacent to source rocks,and typical examples are most of tight hydrocarbon reservoirs;the hydrocarbons are distributed quasicontinuously in large areas,and each quasi-continuous hydrocarbon accumulation includes numerous adjacent small-to medium-size reservoirs;reservoirs of this kind of hydrocarbon accumulation have no defined boundaries,no or only local edge and bottom water distribution,and no regional oil-gas-water inversion;hydrocarbons are pervasively charged in large areas,and oil and gas accumulation is caused by primary migration and short-distance secondary migration;the hydrocarbon migration and accumulation is principally driven by non-buoyant forces in non-Darcy flow;and the hydrocarbon accumulation is basically not controlled by anticline traps,but largely by non-anticline traps,especially lithological traps.The discontinuous hydrocarbon accumulation is also named as the hydrocarbon accumulation of the conventional-trap type,and typically occurs in conventional reservoirs,but some tight hydrocarbon reservoirs,coalbed methane reservoirs and even possible shale hydrocarbon reservoirs also belong to this kind of hydrocarbon accumulation;the hydrocarbon reservoirs are distributed discontinuously,and have clear boundaries and complete edge water or bottom water;the hydrocarbon migration and accumulation is mainly driven by buoyancy and secondary migration is usually indispensable;the hydrocarbon accumulation is strictly controlled by various traps,especially structural traps.In a petroliferous basin,above three types of hydrocarbon accumulation may coexist,andhydrocarbons are often derived from a common source kitchen(s).Therefore,these three types of hydrocarbon accumulation should be considered and studied as a whole to maximize hydrocarbon exploration efficiencvy.展开更多
There is promising indication of helium-rich natural gas in Weihe Basin.However,the lack of a detailed investigation on the origin and the spatial distribution of helium source rocks(mainly Yanshanian granites)limits ...There is promising indication of helium-rich natural gas in Weihe Basin.However,the lack of a detailed investigation on the origin and the spatial distribution of helium source rocks(mainly Yanshanian granites)limits the helium potentiality evaluation in Weihe Basin(WB).We performed three-dimensional(3 D)inversions of magnetic data in Weihe Basin and its adjacent areas to figure out the crustal thermal structure and the temporal-spatial distribution of deep granite in the basin.Based on this,we have proposed a geological model of helium accumulation and predicted the potential area of helium distribution.The results of 3 D magnetic inversion indicate that the granites in the deep Weihe Basin are mostly located at the central and southern parts of the basin,which are connected spatially with the granites in the North Qinling Orogenic Belt.These granites were all derived from largescale intra-continental orogeny in the Qinling area during the mid-Mesozoic,providing a good material basis for crust-derived helium in the basin.The local uplift of the Curie surface makes the thermal fluid more actively,which contributes to helium accumulation.The faults developed in the WB are the migration pathway of crust-derived helium and the upward migration of the mantle-derived helium.The wells with high percentage helium are mostly located near the Weihe fault and the areas on the south of it.The Wugong-Xi’an-Lantian area in the central and the Lintong-Weinan-Tongguan area in the eastern Weihe Basin are the most promising helium distribution areas.Furthermore,the region from the north of Taibai Mountain to Baoji City in the western Weihe Basin may also be another potential area of Helium resource.展开更多
Much progress in the studies on overpressuring mechanisms has been made during the past one to two decades.(1)The causes of overpressure are divided into five categories,namely,disequilibrium compaction,fluid expansio...Much progress in the studies on overpressuring mechanisms has been made during the past one to two decades.(1)The causes of overpressure are divided into five categories,namely,disequilibrium compaction,fluid expansion,diagenesis,tectonic compression and pressure transfer.The fluid expansion involves hydrocarbon generation,oil cracking to gas and hydrothermal expansion.The diagenesis includes smectite-to-illite transformation.(2)Six methods for identifying overpressure origin are proposed,including log curves combination analysis,Bowers method(loading-unloading diagram),velocitydensity crossplotting,correlation of porosities,pressure calculation and correlation,and comprehensive analyses.(3)With more and more application of empirical methods in the study of overpressure formation,almost all of the overpressure cases that are traditionally thought to be caused by disequilibrium compaction are denied totally or partly.Instead,the hydrocarbon generation is demonstrated to be the most significant mechanism for overpressure formation;the clay diagenesis(especially the smectiteillite transformation)as well as tectonic compression and pressure transfer are also important for overpressure formation.In addition,the overpressure formation in many basins is thought to be influenced by the combination of two or more overpressuring mechanisms.(4)Causes of overpressuring differ in lithology;for mudstones,the overpressure formation in source rocks is usually different from that of non-source rocks,the former of which is frequently related to hydrocarbon generation and sometimes also affected by diagenesis,while the later of which is commonly related to disequilibrium compaction,diagenesis and pressure transfer;for permeable rocks such as sandstones,overpressure is mainly caused by pressure transfer.(5)Because organic matter has an obvious influence on logging parameters such as density and acoustic velocity,an appropriate correction on the content of organic matter is needed when these logging data are used to analyze overpressure formation in organic-rich mudstones.It has been revealed that the cause of overpressuring based on the corrected log data can be quite different from that without correction.展开更多
The ongoing collision and continuous compression between the Indian and Eurasian plates began 55 Ma ago[1-3];this process created the magnificent Tibetan Plateau,the highest-elevation landform on the Earth today.Studi...The ongoing collision and continuous compression between the Indian and Eurasian plates began 55 Ma ago[1-3];this process created the magnificent Tibetan Plateau,the highest-elevation landform on the Earth today.Studies have shown that a continent-continent collision occurred not only south of the Tibetan Plateau but also north of the plateau[4].展开更多
文摘Logging data and its interpretation results are one of the most important basic data for understanding reservoirs and oilfield development. Standardized and unified logging interpretation results play a decisive role in fine reservoir description and reservoir development. Aiming at the problem of the conflict between the development effect and the initial interpretation result of Yan 9 reservoir in Hujianshan area of Ordos Basin, by combining the current well production performance, logging, oil test, production test and other data, on the basis of making full use of core, coring, logging, thin section analysis and high pressure mercury injection data, the four characteristics of reservoir are analyzed, a more scientific and reasonable calculation model of reservoir logging parameters is established, and the reserves are recalculated after the second interpretation standard of logging is determined. The research improves the accuracy of logging interpretation and provides an effective basis for subsequent production development and potential horizons.
文摘1 Introduction Petroleum accumulations from the Earth's crust can be grouped into conventional and unconventional ones. The history of the world's petroleum exploration is a history from the exploration of conventional accumulations to that of unconventional ones.
文摘Based on the analysis of a large number of core samples, logging results, logging interpretation data and dynamic data in the study area, the characteristics of Chang 6 reservoir in Zhouguan area of Baihe area are studied, and the favorable reservoir areas in the study area are predicted. The results show that the lithology of Chang 6 reservoir is mainly light gray and gray fine-grained to very fine-grained feldspar lithic sandstone. The pore types are mainly residual intergranular pores and feldspar dissolved pores, including debris dissolved pores and microfractures. The porosity and permeability values are low, which belongs to low porosity-low permeability and ultra-low permeability reservoirs. According to the reservoir distribution characteristics and related data, the Chang 6 reservoir in the study area is divided into two types, mainly Class II and Class III reservoirs. The comprehensive evaluation predicts that the spatial distribution of the favorable area of Chang 6 reservoir is not uniform, but the distribution area is large, which has broad exploration and development value, and provides the necessary conditions for the distribution study of the favorable oil-bearing zone in this area and the preparation for the next exploration and development.
文摘Oil saturation was an important parameter of reservoir evaluation, which had important guiding significance for oilfield development. In this paper, the oil saturation of tight oil in G area was studied, and the original oil saturation of the study area was studied by using the comprehensive experimental method. The original oil saturation of tight oil in the study area was determined by J function method, rock electricity method and oil-based mud coring method. The results showed that through the comparison of three experimental methods, it could be concluded that the J function method leads to the low value of oil saturation in the study area. The oil-based mud coring method was more suitable for the determination of oil saturation in this area than the other two methods because it needs to meet too many conditions and the calculation results were also low. G area was located in Qili Village, Ordos Basin.
基金supported by National Science and Technology Major Project of China (Project No. 2016ZX05050, 2011ZX05018001-004)National Natural Science Foundation Project of China (No. 41402121 and 41502132)
文摘A new classification of petroleum systems(PSs) based on reservoir qualities is proposed. We classify PSs into the following three basic types:(1) source-rock petroleum system(SPS);(2) tight-reservoir or tight petroleum system(TPS);and(3) conventional-reservoir or conventional petroleum system(CPS). The CPS is a PS in which hydrocarbons accumulate in conventional reservoirs, and all the essential elements and processes are significant and indispensable. Oil and gas accumulations are geographically discrete and therefore exist as discontinuous accumulations. The TPS is a PS where hydrocarbons accumulate in tight reservoirs and the source rock, reservoir, seal, migration, and trap are also indispensable,but the traps are mostly non-anticlinal and the accumulations are primarily quasi-continuous and secondarily discontinuous. The SPS is a PS where both hydrocarbon generation and accumulation occurred in source rocks and traps and migration are unnecessary or inconsequential; the hydrocarbon distribution is extensive and continuous and has no distinct boundaries. The aforementioned three PSs can be derived from a common hydrocarbon source kitchen and are closely linked in terms of their formation and distribution. Therefore, to maximize the exploration efficiency, a comprehensive study and different strategies are needed by considering the SPS, TPS, and CPS as parts of a greater whole.
基金This work was supported by the National Natural Science Foundation of China(Program No.41330315)the Natural Science Foundation of Shaanxi Province(Program No.2020JQ-766)+1 种基金the Scientific Research Program Funded by Shaanxi Provincial Education Department(Program No.20JK0838)the Opening Foundation of Shandong Key Laboratory of Depositional Mineralization&Sedimentary Mineral,Shandong University of Science and Technology(Program No.DMSM20190034).
文摘Carbonate concretions are conspicuous in organic-rich shales and are generally related to decomposition of organic matter.The black shales from the Chang 7 Member of the Upper Triassic Yanchang Formation of the southern Ordos Basin host abundant carbonate concretions,which provide a unique record of depositional and early diagenetic conditions of the paleo-lake sediments.However,little attention has been given to the genesis and growth processes of the concretions in these lacustrine petroleum source rocks.New petrographic observations and geochemical analysis show that the concretions are composed of calcite,phosphate fossil fragments,K-NH4-feldspar,quartz,bitumen,and minor Fe-dolomite.Phosphate minerals,mainly carbonate fluorapatite(CFA),show pervasive replacement by calcite,most of which contains phosphorus,ranging in concentration from 0.26 to 2.35 wt%.This suggests that the phosphate minerals are the precursors for concretion growth.Positiveδ13C(+5.6 to+12.4‰V-PDB)signatures and the absence of pyrite indicate that microbial methanogenesis was the dominant driver for concretion growth,rather than bacterial sulfate reduction.Quartz,bitumen,and Fe-dolomite are the last cements that occurred,at deep burial depths and high temperatures.The formation of phosphate minerals might have been induced by upwelling of phosphate-enriched deep water in the Late Triassic paleo-lake,which promoted phytoplankton blooms and further enrichment of organic matter.Extremely slow sedimentation rates of fine-grained detrital minerals,relative to dead organism accumulation,led to the high permeabilities of the organic-rich sediments and rapid concretion growth during shallow burial.The close association of phosphate-bearing carbonate concretions and organic-rich shales reflects that upwelling played a critical role in the formation of the high-quality petroleum source rocks in the Triassic paleo-Ordos lake.
基金supported by the National Natural Science Foundation of China(Grant Nos.41872124,1972132,42072174,41730421,and 41972132)the Open Foundation of provincial and ministerial Key Laboratory of China University of Geosciences(Beijing)(Grant No.20210104)。
文摘A new method is proposed to analyze the pore-scale mechanisms and characterization of light oil storage in shale nanopores,which is based on the Hydrocarbon Vapor Adsorption(HVA)and Pore Calculation Model(PCM).First,the basic principle of the HVA-PCM method is introduced,and the experimental/mathematical analysis processes are given.Then,the HVA-PCM method is applied to shale samples to analyze the mechanisms and characterization of light oil storage in shale nanopores.The results provide insights into the pore-scale oil storage mechanisms,oil storage structure,oil film thickness,oil distribution within different sized pores,and the oil storage state.Finally,the advantages and limitations of the HVA-PCM method are discussed,and suggestions for further improvement are proposed.Overall,the HVA-PCM method is a powerful tool for extracting quantitative information on the light oil storage in shale nanopores.
基金supported by National Natural Science Foundation of China(Grant No.41402274,41877242)。
文摘It is difficult to obtain reliable shear strength parameters for the stability analysis and evaluation of high loess slopes.Hence,this paper determines slope elements and physical parameter of 79 slopes with heights of[40,120]m based on the measured loess slopes in the Ganquan and Tonghuang subregions of northern Shaanxi Province,China.In the limit state of the loess slope(stability factor Fs is 1.0),a fitting equation for the slope height and width is established.Then,the model is developed by stability analysis software-SLOPE/W,and the comprehensive shear strength parameters corresponding to different slope heights of the high slope in the study area are obtained by inversion using the Morgenstern-Price method.The results show that when the height of the slope increases,the cohesion c increases in the soil,and the internal friction angle j decreases.This change is consistent with the characteristics reflected in the composition and physical properties of the slopes,and the comprehensive strength parametric curves are very similar between the Ganquan subregion and the Tonghuang subregion.A landslide that occurred in Miaodian-zaitou of Jingyang County,Shaanxi Province,is selected to verify this inversion method,and the results show that the calculated shear strength parameters of the inversion are consistent with the measured value of the actual slope.
基金supported by the Science and Technology Program of Shaanxi Province (Grants No. 2019KJXX-078)the National Natural Science Foundation of China (Grants No. 41330315, 41572102, and 41202077)+1 种基金Natural Science Foundation of Shaanxi Province (Grants No. 2018JM4001)China Geological Survey project (Grants No. 121201011000161111-02)
文摘The Triassic strata in the Turpan-Hami Basin potentially chronicled the missing sedimentary record of Indosinian tectonic evolution in the Eastern Tianshan.In this study,we conducted detrital zircon U-Pb geochronological analyses on subsurface Triassic samples collected from the Turpan-Hami Basin to unravel sedimentary response of Indosinian tectonic reactivation and its geodynamics.The detrital zircon age spectra of the Triassic samples are quite different,reflecting significant provenance variability.The zircon grains in the Lower Triassic sample were mainly from the Central Tianshan,while the Jueluotag acted as a minor provenance.By contrast,the Late Paleozoic rocks in Jueluotag act as the main provenance for the Middle-Upper Triassic samples,while the Central Tianshan acted as a minor provenance.Furthermore,zircon grains in the Middle Triassic sample were mainly from the Permian rocks in Jueluotag,while Indosinian strike-slipdriven rapid exhumation brought deeper Carboniferous rocks of Jueluotag as an important age population for the Upper Triassic sample.The inter-sample variability of age spectra of the Triassic samples provides sedimentary evidence for Indosinian tectonic reactivation in the Eastern Tianshan and its periphery,which could be attributed to differential exhumation of different sources driven by coeval strike-slip tectonics along deep faults.The Indosinian tectonic behavior in the Eastern Tianshan,which is characterized by partial melting of the pre-thickened crust and strike-slip deformation,acted as a far-field respond to the coeval continental accretion occurring along the southern Eurasian margin.Additionally,our new detrital zircon data,together with previously published data in the Turpan-Hami Basin,demonstrate that there are significant changes in source-to-sink system from the Permian to the Triassic,suggesting that the Permian-Triassic unconformity in the Eastern Tianshan and its periphery was generated by Late Permian-Early Triassic tectonic contraction and inversion rather than an increasingly arid climate.
基金sponsored by the National Natural Science Foundation of China(No.41702127,41372148)the National Science and Technology Major Project of China(No.2017ZX05039001)+1 种基金Natural Science Foundation of Shaanxi Province(No.2017JQ4004)Science and Technology Innovation Foundation of Xi’an Shiyou University(No.2016BS19).
文摘The Shanxi Formation(Shan 1 and Shan 2 Members)shales show good prospects in shale gas development in the Yan'an area of Ordos Basin.Based on the simulation experiment of hydrocarbon generation of low maturity shale samples,the hydrocarbon generation characteristics of shale samples was studied systematically.Then,combined with the geochemical analysis of shale and gas generation simulation,shale gas potential was evaluated.The results reveal that Shan 1 and Shan 2 shale samples are favorable for shale gas enrichment by and large,with C_(1)-C_(5) maximum yields of 146.96-160.83 mg/g TOC and 148.48-148.67 mg/g TOC respectively at a heat rate of 20℃/h and 2℃/h.The Shan 1 and Shan 2 shales are basically the same in terms of organic carbon production potential of each unit.The carbon isotopic composition of alkane gas reveals that heteroatomic compounds(NSOs)cracking is an important mechanism for shale gas generation of Shanxi Formation shales,and conducive to gas generation at highto over-mature stages.Given thermal history and kinetic parameters of hydrocarbon generation,the shales of Shanxi Formation reached the maximum gas production potential in the Late Cretaceous,with a maximum yield of 160.3 mg/g TOC under present geological conditions.During geological history,the Shanxi Formation shales went through high-to over-maturity evolution,mainly producing dry gas,and their gas generation capacity was controlled by the organic matter abundance and cracking capacity.The gas generation potential of Shan 2 shale is higher than that of Shan 1,due to its higher TOC.
基金funded by the National Natural Science Foundation of China(42102154,41922015,42072147)Postdoctoral Research Foundation of China(2021M690168)+4 种基金Postdoctoral Innovative Talent Support Program of Shandong Province(SDBX2021004)Open Fund of Shaanxi Key Laboratory of Petroleum Accumulation Geology(PAG-2021-02)Open Funds of the Key Laboratory of Tectonics and Petroleum Resources(China University of Geosciences)(TPR-2021-02)Fundamental Research Funds for the Central Universities(20CX06085A)Qingdao Postdoctoral(ZX20210070).
文摘Shale porosity measurements have crucial scientific and economical applications in unconventionalpetroleum systems. As a standard technique, liquid saturation methods, including water saturation (WS)and oil saturation (OS), have been widely used to measure the porosity of many rock types. For clay-richshale reservoirs with high organic matter content, it is well known that the WS method may cause clayswelling and induce structural changes in the pore system. The OS method affects the accuracy ofporosity measurements because of some of the oil being dissolved by kerogen within the shale;however,this has not received sufficient research attention. In this study, we compare the previously reported andnewly tested OS porosities with helium (He) expansion porosity. Results show that OS porosity generallyexceeds the He porosity. Furthermore, the higher the total organic carbon (TOC) content and lower thematurity of shale, the greater the difference between the OS and helium porosities. When using the OSmethod, the effect of kerogen-dissolved oil causes an overestimation of the shale porosity by ~30%. To thebest of our knowledge, this is the first time to note the kerogen-dissolve oil effects on OS porosity. Herein,we propose a new, simple, and effective correction method for estimating OS porosity that involvessubtracting the kerogen-dissolved oil content from raw OS porosity. In addition, the quantification modelof kerogen-dissolved oil capacity is established, taking into account the abundance and maturity oforganic matter. Taking the He porosity as the benchmark, the absolute error of the corrected OS porositydoes not exceed 1% and the average relative error is only ~10%. The obtained results can help improve theaccuracy of shale porosity evaluation methods.
基金supported by the National Natural Science Foundation of China(41702132).
文摘The study of pore structure requires consideration of important factors including pore throat size,pore radius composition,and pore-throat configuration.As the nuclear magnetic resonance(NMR)experimental results contain rich information about pore structures and fluid occurrence states,this study investigated the pore structures of the tight sandstone reservoirs of the Shanxi Formation in the Daning-Jixian area,eastern Ordos Basin.Firstly,by making the inverse cumulative curve of the NMR T2 spectrum coincide with the capillary pressure curves which were obtained by the mercury injection capillary pressure(MICP)technique,this study derived a conversion coefficient that can be used to convert the NMR T2 spectrum into the pore throat radius distribution curves based on the NMR experimental results.Subsequently,we determined the pore radius intervals corresponding to irreducible water distribution using the NMR-derived pore radius distribution curves.Finally,the NMR T2 distribution curves based on the fractal theory were analyzed and the relationships between fractal dimensions and parameters,including permeability,porosity,reservoir quality index(RQI),flow zone indicator(FZI),irreducible water saturation,RT35,and RT50,were also discussed.The NMR-derived pore throat radius distribution curves of the study area are mainly unimodal,with some curves showing slightly bimodal distributions.The irreducible water mainly occurs in small pores with a pore radius less than 100 nm.As the permeability decreases,the contribution rate of small pores to the irreducible water gradually increases.The NMR-based fractal dimensions of pores show a two-segment distribution.Small pores have small fractal dimensions and are evenly distributed,while large pores have large fractal dimensions and complex pore structures.The fractal dimension of large pores(Dmax)is poorly correlated with porosity but strongly correlated with FZI,RQI,RT35,and RT50.These results indicate that large pores are the main pore zones that determine the seepage capacity of the reservoirs.Additionally,there is a certain correlation between Dmax and the irreducible water saturation.
基金Project (2011ZX05007-004) supported by the National Sciences and Technologies,ChinaProject (41502132) supported by the National Natural Science Foundation of China
基金This work was supported by National Science and Technology Major Project of China(Grant No.2011ZX05007-004 and Grant No.2011ZX05018001-004)National Natural Science Foundation of China(Grant No.41402121 and Grant No.41502132)+1 种基金Natural Science Basic Research Plan in Shaanxi Province of China(Grant No.2013JM5007)Shaanxi Provincial Natural Science Foundation of China(Grant No.2013JQ503).
文摘Based on the extensive studies of conventional and unconventional hydrocarbon accumulations,the concept,classification and formation as well as distribution of petroleum reservoirs are discussed.The revised concept defined the petroleum reservoir as a continuous hydrocarbon accumulation in a single or a set of reservoirs with an independent or uniform pressure system.In terms of the pattern of hydrocarbon accumulation and distribution,the hydrocarbon accumulations are classified into three basic types,i.e.,the continuous accumulation,the quasi-continuous accumulation and the discontinuous accumulation.The hydrocarbon accumulation was demonstrated as a process from continuous accumulation to discontinuous accumulation,and therefore these three basic types of hydrocarbon accumulations were identified.The continuous hydrocarbon accumulation is principally formed in source rocks,and typical examples are shale hydrocarbon reservoirs and coal-bed methane reservoirs;it is mainly characterized by tight-ultra tight reservoirs with permeability of nanodarcy to millidarcy;the hydrocarbons occurred in free,adsorbed or dissolved state;a continuous accumulation comprises actually only a single reservoir,and hydrocarbons are extensively and continuously distributed within the scope of effective source rocks;the accumulation has neither defined boundaries nor bottom or edge water;oil and gas mainly accumulate in situ or near the generation of hydrocarbons with no prominent migration;this hydrocarbon accumulation process is basically not controlled by traps.The quasicontinuous hydrocarbon accumulation mostly occurs in the tight reservoirs adjacent to source rocks,and typical examples are most of tight hydrocarbon reservoirs;the hydrocarbons are distributed quasicontinuously in large areas,and each quasi-continuous hydrocarbon accumulation includes numerous adjacent small-to medium-size reservoirs;reservoirs of this kind of hydrocarbon accumulation have no defined boundaries,no or only local edge and bottom water distribution,and no regional oil-gas-water inversion;hydrocarbons are pervasively charged in large areas,and oil and gas accumulation is caused by primary migration and short-distance secondary migration;the hydrocarbon migration and accumulation is principally driven by non-buoyant forces in non-Darcy flow;and the hydrocarbon accumulation is basically not controlled by anticline traps,but largely by non-anticline traps,especially lithological traps.The discontinuous hydrocarbon accumulation is also named as the hydrocarbon accumulation of the conventional-trap type,and typically occurs in conventional reservoirs,but some tight hydrocarbon reservoirs,coalbed methane reservoirs and even possible shale hydrocarbon reservoirs also belong to this kind of hydrocarbon accumulation;the hydrocarbon reservoirs are distributed discontinuously,and have clear boundaries and complete edge water or bottom water;the hydrocarbon migration and accumulation is mainly driven by buoyancy and secondary migration is usually indispensable;the hydrocarbon accumulation is strictly controlled by various traps,especially structural traps.In a petroliferous basin,above three types of hydrocarbon accumulation may coexist,andhydrocarbons are often derived from a common source kitchen(s).Therefore,these three types of hydrocarbon accumulation should be considered and studied as a whole to maximize hydrocarbon exploration efficiencvy.
基金supported by the National Natural Science Foundation of China(No.41904115)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2018JQ4034)。
文摘There is promising indication of helium-rich natural gas in Weihe Basin.However,the lack of a detailed investigation on the origin and the spatial distribution of helium source rocks(mainly Yanshanian granites)limits the helium potentiality evaluation in Weihe Basin(WB).We performed three-dimensional(3 D)inversions of magnetic data in Weihe Basin and its adjacent areas to figure out the crustal thermal structure and the temporal-spatial distribution of deep granite in the basin.Based on this,we have proposed a geological model of helium accumulation and predicted the potential area of helium distribution.The results of 3 D magnetic inversion indicate that the granites in the deep Weihe Basin are mostly located at the central and southern parts of the basin,which are connected spatially with the granites in the North Qinling Orogenic Belt.These granites were all derived from largescale intra-continental orogeny in the Qinling area during the mid-Mesozoic,providing a good material basis for crust-derived helium in the basin.The local uplift of the Curie surface makes the thermal fluid more actively,which contributes to helium accumulation.The faults developed in the WB are the migration pathway of crust-derived helium and the upward migration of the mantle-derived helium.The wells with high percentage helium are mostly located near the Weihe fault and the areas on the south of it.The Wugong-Xi’an-Lantian area in the central and the Lintong-Weinan-Tongguan area in the eastern Weihe Basin are the most promising helium distribution areas.Furthermore,the region from the north of Taibai Mountain to Baoji City in the western Weihe Basin may also be another potential area of Helium resource.
基金The work is supported by the National Science and Technology Major Project of China(No.2016ZX05044,2011ZX05007-004)the National Natural Science Foundation of China(No.41502132).
文摘Much progress in the studies on overpressuring mechanisms has been made during the past one to two decades.(1)The causes of overpressure are divided into five categories,namely,disequilibrium compaction,fluid expansion,diagenesis,tectonic compression and pressure transfer.The fluid expansion involves hydrocarbon generation,oil cracking to gas and hydrothermal expansion.The diagenesis includes smectite-to-illite transformation.(2)Six methods for identifying overpressure origin are proposed,including log curves combination analysis,Bowers method(loading-unloading diagram),velocitydensity crossplotting,correlation of porosities,pressure calculation and correlation,and comprehensive analyses.(3)With more and more application of empirical methods in the study of overpressure formation,almost all of the overpressure cases that are traditionally thought to be caused by disequilibrium compaction are denied totally or partly.Instead,the hydrocarbon generation is demonstrated to be the most significant mechanism for overpressure formation;the clay diagenesis(especially the smectiteillite transformation)as well as tectonic compression and pressure transfer are also important for overpressure formation.In addition,the overpressure formation in many basins is thought to be influenced by the combination of two or more overpressuring mechanisms.(4)Causes of overpressuring differ in lithology;for mudstones,the overpressure formation in source rocks is usually different from that of non-source rocks,the former of which is frequently related to hydrocarbon generation and sometimes also affected by diagenesis,while the later of which is commonly related to disequilibrium compaction,diagenesis and pressure transfer;for permeable rocks such as sandstones,overpressure is mainly caused by pressure transfer.(5)Because organic matter has an obvious influence on logging parameters such as density and acoustic velocity,an appropriate correction on the content of organic matter is needed when these logging data are used to analyze overpressure formation in organic-rich mudstones.It has been revealed that the cause of overpressuring based on the corrected log data can be quite different from that without correction.
基金supported by the National Natural Science Foundation of China(41874123 and 42004110)PetroChina Innovation Foundation(2010D-5006-0303 and 2014D-5006-0303)Shaanxi Provincial Natural Science Basic Research Project(2011JQ5006,2017JZ007 and 2022GY-148)。
文摘The ongoing collision and continuous compression between the Indian and Eurasian plates began 55 Ma ago[1-3];this process created the magnificent Tibetan Plateau,the highest-elevation landform on the Earth today.Studies have shown that a continent-continent collision occurred not only south of the Tibetan Plateau but also north of the plateau[4].