Geological CO_(2) storage is a promising strategy for reducing greenhouse gas emissions and has become a growing focus of research and deployment.This paper presents numerical simulations of CO_(2) injection and stora...Geological CO_(2) storage is a promising strategy for reducing greenhouse gas emissions and has become a growing focus of research and deployment.This paper presents numerical simulations of CO_(2) injection and storage in a depleted gas reservoir within the B Depression and evaluates associated CO_(2) trapping mechanisms.In the base case,a constant injection rate of 3500 m^(3)/d over fifteen years resulted in a cumulative injection of 19.2×10^(6) m^(3).The CO_(2) plume expanded radially during injection and subsequently migrated up-dip under buoyancy forces.The final stored mass of CO_(2) in the reservoir was 10.6 million tonnes(Mt),representing less than 10% of its theoretical capacity.The plume was projected to reach the entrapment crest and the top of the reservoir within a century,indicating secure long-term containment.Structural,stratigraphic,and residual trapping dominate in Reservoir A(approximately 90%).Anticlinal closures with thick overlying mudstones in the Zhujiang Formation provide effective seals,further enhancing storage security.Reservoir properties and heterogeneity play a crucial role in controlling CO_(2) storage.However,reservoir heterogeneity exerts only a limited influence when intrinsic properties are favorable.Overall,the study and implementation of CO_(2) capture,utilization,and storage(CCUS)in China's offshore basins show promising prospects.展开更多
Oilfield M currently has a comprehensive water cut of 73.2%after more than 20 years of development,the reservoir is experiencing both edge-bottom water flooding and injection water flooding,with diverse types of injec...Oilfield M currently has a comprehensive water cut of 73.2%after more than 20 years of development,the reservoir is experiencing both edge-bottom water flooding and injection water flooding,with diverse types of injected water and complex flooding patterns,necessitating the research on logging evaluation methods for water-flooded layers.By introducing the variable multiple injection water material balance theory and combining it with the rock-electric relationship,an analysis of the water flooding mechanism in the study area was conducted.This led to the establishment of the variation characteristics between formation resistivity,water production rate,and saturation under different reservoir types and different salinities of injected water in the area;using the semi-permeable membrane capillary pressure experiment,the relationship between the original formation resistivity and the oil column height was established,deriving the relationship between the water production rate and the formation resistivity drop rate,combining the analysis of the water flooding mechanism mentioned above,allowing for a quantitative assessment of the level of water flooding;optimizing the mixed formation water resistivity calculation model to accurately determine parameters such as remaining oil saturation and water production rate,a set of identification and quantitative evaluation methods for waterflooded layers in Oilfield M was formed.The interpretation accuracy reached 87.5%,providing strong technical support for selecting perforation layers in the oilfield and avoiding highly flooded layers.This is of significant application value for the remaining oil evaluation and efficient development of water-flooded layers in overseas clastic rock oilfields.展开更多
Based on the latest drilling, seismic and field outcrop data, the geological characteristics(e.g. strata, development and sedimentary evolution) of the southern segment of the Late Sinian–Early Cambrian Deyang–Anyue...Based on the latest drilling, seismic and field outcrop data, the geological characteristics(e.g. strata, development and sedimentary evolution) of the southern segment of the Late Sinian–Early Cambrian Deyang–Anyue rift trough in the Sichuan Basin are analyzed. First, the strata in the southern segment are complete. The first to second members of Dengying Formation(Deng 1 + Deng 2) are found with relatively stable thickness(400–550 m), and the third to fourth members(Deng 3+ Deng 4) show great thickness difference between the marginal trough and the inner trough, which is up to 250 m. The Cambrian Maidiping Formation and Qiongzhusi Formation in southern Sichuan Basin are relatively thin, with the thickness changing greatly and frequently. Second, the Deyang–Anyue rift trough extended southward during the Deng 4 period, affecting southern Sichuan Basin. Compared to the middle and northern segments of the rift trough, the southern segment is generally wide, gentle and shallow, with multiple steps, and alternating uplifts and sags, which are distributed in finger shape. Third, the Deng 1 + Deng 2 in southern Sichuan Basin records the dominance of carbonate platform and unobvious sedimentary differentiation, and the Deng 4 exhibits obvious sedimentary differentiation, namely, basin–slope–secondary slope–slope–secondary slope–platform margin–restricted platform, from the inner trough to the marginal trough. Fourth, the rift trough in southern Sichuan Basin has evolved in four stages: stabilization of Deng 1–Deng 2, initialization of Deng 3–Deng 4, filling of Maidiping–Qiongzhusi, and extinction of Canglangpu Formation.展开更多
Focusing on the Yangtze River economic zone,the previous geological researches are systematically summarized,resources and environment conditions and major geological problems which are needing to be concerned in land...Focusing on the Yangtze River economic zone,the previous geological researches are systematically summarized,resources and environment conditions and major geological problems which are needing to be concerned in land planning and construction are studied.The results show that the resource conditions of cultivated land,shale gas,geotherm,lithium and so on are superior in the Yangtze River economic zone,and the resources and environment conditions are conducive to develop the modern agriculture,clean energy industry and strategic emerging industries.3×1013 m^2 farmlands without heavy metal pollution are concentrated;there are three national level shale gas exploration and development bases with explored reserves of 5.441×1011 m^3;geothermal availability is 2.4×109 t of standard coal each year,equivalent to 19% of the amount of coal in 2014;Asia's largest energy lithium metal ore deposit is found.In some parts of Yangtze River economic zone,there are some major geological problems such as active faults,karst collapse,ground subsidence,landslide-collapse-debris flow,affecting the river-crossing channels,high-speed railway,urban agglomeration and green ecological corridor planning and construction.Those problems should be concerned,and the relevant suggestions and countermeasures are put forward.Meanwhile,the ideas to further support the development of the Yangtze River economic zone are put forward.展开更多
The chemistry and migration patterns of the mantle ichor are discussed on a globle scale followed by evaluations of the significance of HACONSfluid with respect to various geological processes of fundamental interest.
This paper discussed the direction of secondary migration of oil in the No. 6 area of the Melut Basin by making use of nitrogen compounds as secondary oil migration tracers. From the results, we have found that the oc...This paper discussed the direction of secondary migration of oil in the No. 6 area of the Melut Basin by making use of nitrogen compounds as secondary oil migration tracers. From the results, we have found that the occurrence and compositional characteristics of isomeric-nitrogen compounds in crude oil precisely manifest the fractionation effect of oil migration: with increasing secondary migration distance, the absolute concentrations tend to decrease, and the ratio of nitrogen-shielded isomers to nitrogen-exposed isomers tends to increase. It is considered that the main direction of oil migration in the No. 6 area of the Melut Basin is from north to south.展开更多
The Xing’an block (XB) is located in the eastern part of the Xingmeng orogenic belt, bounded by Erguna block (EB) to northwest and the Songnen block (SB) to the southeast (Fig. 1a).
This paper presents the morphologic,chemical and other typomorphic characteristics of native gold from four placer deposits(basins of the Lev.Nora,Skalistaya and Golysheva rivers,and Loginova brook),four placer occurr...This paper presents the morphologic,chemical and other typomorphic characteristics of native gold from four placer deposits(basins of the Lev.Nora,Skalistaya and Golysheva rivers,and Loginova brook),four placer occurrences(basins of the Lagernaya,Nizh.Litke and Prokhodimaya rivers,and Tikhiy brook),and the alluvial deposit of cape Mordovin on Bolshevik island of the Severnaya Zemlya archipelago(Russia).Optical microscopy,scanning electron microscopy and electron-probe microanalysis were used in this study.Placer gold from the Lagernaya,Golysheva,Nizh.Litke and Skalistaya rivers,Tikhiy brook and cape Mordovin is characterized by a very high fineness(>988‰)in the rims and a lower fineness(860‰–970‰)in the center.Gold particles from the placers of the Lev.Nora and Prokhodimaya rivers and Loginova brook are low fineness and widely vary in the center(from 647‰to 920‰)and are high fineness(950‰–980‰)in the rims.In some gold particles from the placers of the Lev.Nora and Skalistaya rivers,zones with Cu up to 1.2 wt.%and Hg up to 2.6 wt.%are observed.Titanite,monazite,cobaltite,ulmannite,brannerite,rutile,zircon,Y-xenotime,bismuthite,native bismuth and bismuthinite,garnet(almandine),Cu-or Ni-pyrrhotite were found in the native gold from the Skalistaya and Lev.Nora placers.Native gold from the Skalistaya river placer contains mineral micro-inclusions of cobaltite,Cu,Cd-bearing sphalerite and Fe,Cu-ullmannite.Native gold from the Lev.Nora river placer differs in the presence of brannerite and bismuth minerals.On the basis of the obtained results,available metallogenic characteristics of Bolshevik island and literature data,the following types of primary sources are predicted for these locations:(1)Lev.Nora river deposits of gold-copper rare metal and porphyry gold-copper formations;(2)Skalistaya river deposits of porphyry gold-copper and gold-quartz formation;(3)all the other locations:deposits of gold-quartz and gold-sulfide-quartz formations(hosted in terrigenous carbonaceous complexes).The presence of intermediate reservoirs near some of these locations is probable.展开更多
Pore structure directly affects the occurrence and migration of shale hydrocarbon,and the lack of research on the mechanism of the pore structure is an important reason for the hindrance of shale hydrocarbon explorati...Pore structure directly affects the occurrence and migration of shale hydrocarbon,and the lack of research on the mechanism of the pore structure is an important reason for the hindrance of shale hydrocarbon exploration.By analysing the geochemistry and reservoir characteristics of Jurassic lacustrine shales in Sichuan Basin,this study recovers their paleoenvironments and further discusses paleoenvironmental constraints on pore structure.The results show that the Lower Jurassic lacustrine shales in the Sichuan Basin are in a warm and humid semi-anoxic to anoxic lake environment with high productivity,a strong stagnant environment,and a rapid sedimentation rate,with water depths ranging from about 11.54-55.22 m,and a mixture of type Ⅱ/Ⅲ kerogen is developed.In terms of reservoir characteristics,they are dominated by open-slit pores,and the pores are relatively complex.The percentage of mesopores is the highest,while the percentage of macropores is the lowest.Further analysis shows that paleoclimate controls the overall pore complexity and surface relaxation of shales by influencing the weathering rate of mother rocks.Paleoredox conditions control the proportion and complexity of shale pores by influencing TOC content.The research results will provide theoretical basis for improving the exploration efficiency of lacustrine shale resources and expanding exploration target areas.展开更多
Understanding the historical development of civilization in the Western Regions of China necessitates a detailed chronology and an in-depth analysis of the developmental dynamics of Ancient Loulan City(LA).However,sys...Understanding the historical development of civilization in the Western Regions of China necessitates a detailed chronology and an in-depth analysis of the developmental dynamics of Ancient Loulan City(LA).However,systematic chronological investigations of specific archaeological sites within LA remain scarce,leaving the construction and occupation dates of many sites,along with the urban extent and development phases,unclear.To address these gaps,we established the Loulan Radiocarbon Dating Database and applied the summed probability distribution(SPD)method to reconstruct the chronology of individual sites and the urban development trajectory of LA.Our findings reveal the following:(1)Between~500 BC and~200 BC,only site units LA-Ⅰand LA-Ⅷexisted,representing a nascent village phase;(2)From~200 BC to~AD 100,the construction of LA-IV marked the transition to an urban phase,as evidenced by abundant plant and animal remains that indicate a blend of agricultural and pastoral practices;(3)From~AD 100 to~AD 400,the remaining site units were constructed,occupied,and utilized,signifying the urban phase.This period saw the emergence of complex social stratification,with roles such as monks,soldiers,officials,and blacksmiths shaping the city's structure.These chronological insights provide a new understanding of LA's urban evolution,offering critical evidence for its socio-economic transformation.展开更多
The timings and geodynamic controls of Mo,Au,and Au-Mo deposits in the Xiaoqinling Orogen(>630 t Au and 115,000 t Mo),a rare Au-Mo province globally,are addressed by a combination of mineral par-ageneses,crystallin...The timings and geodynamic controls of Mo,Au,and Au-Mo deposits in the Xiaoqinling Orogen(>630 t Au and 115,000 t Mo),a rare Au-Mo province globally,are addressed by a combination of mineral par-ageneses,crystalline mineralogy,geochemistry,and Re-Os and U-Pb geochronology in the Dahu,Qinnan,and Yangzhaiyu deposits.The Xiaoqinling Orogen comprises an E-W-trending fold and thrust system with repeated structural reactivation and the Mo or Au orebodies in these deposits are dominantly controlled by E-W-trending and NW-SE-trending shear zones.Molybdenum mineralization related to K-feldspar alteration comprises early molybdenite,pyrite,rutile,and monazite within gray quartz veins plus late molybdenite and pyrite within white quartz veins in the Dahu and Qinnan Au-Mo deposits.Early and late Au mineralization events have similar mineral assemblages of pyrite,native gold±Au-Ag-Te minerals,rutile,and monazite associated with quartz-sericite alteration at Yangzhaiyu.The early dissem-inated molybdenite is characterized by rhombohedral polytype and oscillatory Re zoning,in contrast to the late molybdenite with a coexistence of rhombohedral and hexagonal polytypes and irregularly distributed Re.The early molybdenite has a Re-Os isochron age of 222.5±1.3 Ma,compatible with a monazite U-Pb age of 224±6.1 Ma,whereas late molybdenite provides a Re-Os isochron age of 185.0±12 Ma,with the implication that the 3R-polytype molybdenite with oscillatory Re zoning is more suitable for high-precision dating.The early and late Au mineralization have a pyrite Re-Os age of 202.0±5.9 Ma and U-Pb age of 124.0±1.3 Ma,respectively.In accordance with its complex geodynamic setting,geological and geochronological studies record a complicated 100-million-year mineralization history with multiple magmatic-hydrothermal Mo and orogenic Au mineralization events that formed within a structural framework of multiply reactivated shear zones.展开更多
The phenomenon of'bamboo-like'thin interlayers developed in rock salt is one of the most prominent features of Paleogene salt-bearing strata in eastern China,where centimeter-thick rock salts appear separately...The phenomenon of'bamboo-like'thin interlayers developed in rock salt is one of the most prominent features of Paleogene salt-bearing strata in eastern China,where centimeter-thick rock salts appear separately,forming rhythmic units.At present,detailed analyses of these rhythms of rock salt are still limited,which directly affects the achievement of comprehensive and in-depth understanding of the developmental laws pertaining to this kind of saline lake.Therefore,we selected the typical rhythmic'bamboo-like'rock salts of the Shizhai Depression in Jiangsu Province as the research subject.Through careful observation of rock salts in hand samples and detailed petrographic and mineralogical analyses,we analyzed the hydrogen and oxygen isotopic compositions,homogenization temperatures and chemical compositions of individual fluid inclusions in halite crystals.Early-stage rhythmic deposition was a product of continental saline lake evolution in winter or spring,late-stage rhythmic deposition being the product of evolution in the summer.The seasonal evolution of the halite sequences was determined and two brine enrichment events were identified.In addition,the quiet saline lake environment with concentrated brine represented by rock salt was more likely to precipitate potassium.This study provides a new reference for the evolution of both Paleogene climate and saline lakes in eastern China.展开更多
Petroleum exploration targets are extending gradually from the single conventional trap reservoirs to the large-scale unconventional continuous accumulations. Oil and gas reservoirs have been divided into two types ba...Petroleum exploration targets are extending gradually from the single conventional trap reservoirs to the large-scale unconventional continuous accumulations. Oil and gas reservoirs have been divided into two types based on the trapping mechanism and distribution of oil and gas： conven- tional single-trap reservoirs, such as the Daqing oil field in Songliao Basin and the Kela-2 gas field in Tarim Basin; and unconventional continuous petroleum accumulation, such as Upper Paleozoic tight gas and Mesozoic tight oil in Ordos Basin, and Upper Triassic tight gas in Sichuan Basin. Two typical geologic characteristics of continuous petroleum accumulation involve： （1） coexisting source and reser- voir, petroleum pervasive throughout a large area tight reservoirs, and no obvious traps or well-defined water-oil and gas contracts; （2） non-buoyancy accumulation, continuous petroleum charge, and no sig- nificant influence by buoyancy. Continuous petroleum accumulation generally have nm-scale pore throats, and the diameters range of 10-500 nm. The geometry and connectivity of these pore throats has significant impact on the migration and distribution of oil and gas in continuous petroleum accu- mulation. China has numerous continuous petroleum accumulation containing various petroleum de- posits, and the exploration of continuous resources is very promising. Unconventional petroleum geol- ogy will become an important new subject in petroleum geology in future, and the nano-technology will function greatly on research, exploration and development of the hydrocarbon accumulation in nano-pore-throats.展开更多
This study reports zircon U-Pb and Hf isotopes and whole-rock elemental data for granodiorites from the East Kunlun orogen. The zircon U-Pb dating defines their crystallization age of 235 Ma. The rocks are characteriz...This study reports zircon U-Pb and Hf isotopes and whole-rock elemental data for granodiorites from the East Kunlun orogen. The zircon U-Pb dating defines their crystallization age of 235 Ma. The rocks are characterized by high-K calc-alkaline, magnesian and metaluminous with（K2O＋Na2O）=6.38 wt.%–7.01 wt.%, Mg#=42–50 [Mg#=100×molar Mg/（Mg＋Fe OT）], A/CNK=0.92–0.98, coupled with high εHf（t） values from-0.65 to-1.80. The rocks were derived from partial melting of a juvenile mafic crustal source within normal crust thickness. The juvenile lower crust was generated by mixing lithospheric mantle-derived melt（55%–60%） and supracrustal melt（40%–45%） during the seafloor subduction. Together with available data from the East Kunlun, it is proposed that the studied Middle Triassic granodiorites were formed in post-collisional extension setting, in which melting of the juvenile lower crust in response to the basaltic magma underplating resulted in the production of high-K granodioritic melts.展开更多
The Qom Formation comprises Oligo-Miocene deposits from a marine succession distributed in the Central Basin of Iran. It is composed of five members designated as A-F. Little previous work exists on the sequence strat...The Qom Formation comprises Oligo-Miocene deposits from a marine succession distributed in the Central Basin of Iran. It is composed of five members designated as A-F. Little previous work exists on the sequence stratigraphy. Based on an integrated study of sequence stratigraphy with outcrop data, wells and regional seismic profiles, the Qom Formation is interpreted as a carbonate succession deposited in a mid.Tertiary back-arc basin. There are two second-order sequences （designated as SS1 and SS2） and five third-order sequences （designated as S1-S5）. Five distinct systems tracts including transgressive, highstand, forced regressive, slope margin and Iowstand have been recognized. The relationship between the sequences and lithologic sub-units has been collated and defined （S1 to S5 individually corresponding to A-C1, C2--C4, D-E, the lower and upper portions of F）; a relative sea level change curve and the sequence stratigraphic framework have been established and described in detail. The coincidence of relative sea level change between that of the determined back-arc basin and the world indicates that the sedimentary cycles of the Qom Formation are mainly controlled by eustatic cycles. The variable combination of the systems tracts and special tectonic-depositional setting causally underpin multiple sequence stratigraphic framework styles seen in the carbonates of the back-arc basin revealing： （1） a continental margin basin that developed some form of barrier, characterized by the development of multiple cycles of carbonate-evaporites; （2） a flat carbonate ramp, which occurred on the southern shelf formed by the lack of clastic supply from nearby magmatic islands plus mixed siliciclastics and carbonates that occurred on the northern shelf due to a sufficient clastics supply from the land; and （3） a forced regressive stratigraphic stacking pattern that occured on the southern shelf and in basin lows due to the uplifting of the southern shelf. Thick and widespread aggradational framework limestone usually occurs in the initial sequences （S1 and S3） of the supersequence, which led to preferential oil reservoir deposition but a lack of source and cap rocks, whereas the retrogradational and progradational framework limestone usually occurs in the later sequences （S2 and S4-S5） of the supersequence, which results in two perfect sets of source, reservoir and cap rock assemblies, so that the limestone in sub-member C2-C4 and the F-Member can be predicted as important objects for oil exploration.展开更多
During the development of hot dry rock,the research on thermal fatigue damage caused by thermal shock of cold and heat cycles is the basis that ensures the long-term utilization of geothermal resources,but there are n...During the development of hot dry rock,the research on thermal fatigue damage caused by thermal shock of cold and heat cycles is the basis that ensures the long-term utilization of geothermal resources,but there are not enough relevant studies at present.Based on this,the thermal damage tests of granite at different temperatures(250,350,450°C)and quenching cycles(1,5,10,15 cycles)were carried out.Preliminary reveals the damage mechanism and heat transfer law of the quenching cycle effect on hot dry rock.The results show that with the increase of temperature and cycles,the uneven thermal expansion of minerals and the thermal shock caused by quenching promote the crack development of granite,resulting in the decrease of P-wave velocity,thermal conductivity and uniaxial compressive strength of granite.Meanwhile,the COMSOL was used to simulate the heat transfer of hot dry rock under different heat treatment conditions.It concluded that the increase in the number of quenching cycles reduced the heat transfer capacity of the granite,especially more than 10 quenching cycles,which also reflects that the thermal fatigue damage leads to a longer time for the temperature recovery of the hot dry rock mass.In addition,the three-dimensional nonlinear fitting relationship among thermal conductivity,temperature and cycle number was established for the first time,which can better reveal the change rule of thermal conductivity after quenching thermal fatigue effect of hot dry rock.The research results provide theoretical support for hot dry rock reservoir reconstruction and production efficiency evaluation.展开更多
Diagenetic traps in conglomerate in nearshore subaqueous fans in the steep slope zones of rift basins have been important exploration targets for subtle reservoirs in eastern China. However, the mechanism of how those...Diagenetic traps in conglomerate in nearshore subaqueous fans in the steep slope zones of rift basins have been important exploration targets for subtle reservoirs in eastern China. However, the mechanism of how those traps were formed is not clear, which inhibits further exploration for this type of reservoir. In order to solve the problem, we take as an example nearshore subaqueous fans in the upper part of the fourth member of the Shahejie Formation （Es4s） on the north slope of the Minfeng Subsag in the Dongying Sag. Combining different research methods, such as core observation, thin section examination, scanning electron microscope （SEM） observation, fluid-inclusion analysis, carbon and oxygen isotope analysis of carbonate cements, and analysis of core properties, we studied the genetic mechanisms of diagenetic traps on the basis of diagenetic environment evolution and diagenetic evolution sequence in different sub/micro-facies. Conglomerate in Es4s in the north Minfeng Subsag experienced several periods of transition between alkaline and acidic environments as ＂alkaline-acidic-alkaline-acidic-weak alkaline＂. As a result, dissolution and cementation are also very complex, and the sequence is ＂early pyrite cementation / siderite cementation / gypsum cementation / calcite and dolomite cementation- feldspar dissolution / quartz overgrowth quartz dissolution / ferroan calcite cementation / ankerite cementation / lime-mud matrix recrystallization / feldspar overgrowth carbonate dissolution / feldspar dissolution / quartz overgrowth / pyrite cementation＂. The difference in sedimentary characteristics between different sub/micro-facies of nearshore subaqueous fans controls diagenetic characteristics. Inner fan conglomerates mainly experienced compaction and lime-mud matrix recrystallization, with weak dissolution, which led to a reduction in the porosity and permeability crucial to reservoir formation. Lime-mud matrix recrystallization results in a rapid decrease in porosity and permeability in inner fan conglomerates in middle-to-deep layers. Because acid dissolution reworks reservoirs and hydrocarbon filling inhibits cementation, reservoirs far from mudstone layers in middle fan braided channels develop a great number of primary pores and secondary pores, and are good enough to be effective reservoirs of hydrocarbon. With the increase of burial depth, both the decrease of porosity and permeability of inner fan conglomerates and the increase of the physical property difference between inner fans and middle fans enhance the quality of seals in middle-to-deep layers. As a result, inner fan conglomerates can be sealing layers in middle-to-deep buried layers. Reservoirs adjacent to mudstones in middle fan braided channels and reservoirs in middle fan interdistributaries experienced extensive cementation, and tight cemented crusts formed at both the top and bottom of conglomerates, which can then act as cap rocks. In conclusion, diagenetic traps in conglomerates of nearshore subaqueous fans could be developed with inner fan conglomerates as lateral or vertical sealing layers, tight carbonate crusts near mudstone layers in middle fan braided channels as well as lacustrine mudstones as cap rocks, and conglomerates far from mudstone layers in middle fan braided channels as reservoirs. Lime-mud matrix recrystallization of inner fan conglomerates and carbonate cementation of conglomerates adjacent to mudstone layers in middle fan braided channels took place from 32 Ma B.R to 24.6 Ma B.P., thus the formation of diagenetic traps was from 32 Ma B.R to 24.6 Ma B.R and diagenetic traps have a better hydrocarbon sealing ability from 24 Ma B.P.. The sealing ability of inner fans gradually increases with the increase of burial depth and diagenetic traps buried more than 3,200 m have better seals.展开更多
Lacustrine shale from the Qingshankou Formatin of Songliao basin and the Shahejie Formation of Bohai Bay basin, and marine shale from the lower Cambrian Jinmenchong Formation of Qiannan depression were analysed by usi...Lacustrine shale from the Qingshankou Formatin of Songliao basin and the Shahejie Formation of Bohai Bay basin, and marine shale from the lower Cambrian Jinmenchong Formation of Qiannan depression were analysed by using rock pyrolysis, TOC （total organic carbon）, XRD （X-ray diffraction）, SEM （scanning electron microscope）, FE-SEM （field emission scanning electron microscope）, high pressure mercury intrusion, and low pressure N2 and CO2 gas adsorption experiments, in aim to reveal their reservoir features. The results show that： （1） the width of micro-pores of all the studied samples mainly ranges from 0.45 to 0.7 nm indicated by CO2 isotherms, and the width of meso-pores is less than 10 nm, with type IV adsorption isotherms and type H2 hysteresis loop, indicative of ＂ink-bottle＂-shaped pores. Good correlations exist among pore volume, surface area and averaged pore diameter, and a good positive correlation exists between micro-pore volume and TOC content; however, there is no obvious correlation between meso-pore volume and TOC content; （2） interparticle pores, pores among the edge of mineral grains and organic matter pores were all identified in marine and lacustrine shale, among which the interparticle pores may be influence by dissolution effect. Not all bitumen develops organic matter pore, and only high to over mature bitumen present pores. Now the description methods of micrometer scale pores developed in shale are very lack. Micro- fractures developed in Jiyang depression and dissolution interparticle pores developed in Songliao Basin should be the accumulation sites for shale oil in lacustrine shale, and can be as sweet spots.展开更多
An oil flow obtained from the Middle Ordovician Fengfeng Formation carbonate reservoir in the well KG-3, Kongxi burial-hill zone in 1993 marked a breakthrough in petroleum exploration of the high-mature Lower Palaeozo...An oil flow obtained from the Middle Ordovician Fengfeng Formation carbonate reservoir in the well KG-3, Kongxi burial-hill zone in 1993 marked a breakthrough in petroleum exploration of the high-mature Lower Palaeozoic strata, North China. Both the Lower member of the Fengfeng Formation and the Second Member of the Upper Majiagou Formation in the Middle Ordovician are supposed to be the main source beds. Oil generation peaks range from 1.0% to 1.6% in Ro, showing a “lag effect” of oil generation in high-mature carbonate source rocks under multicyclic tectonic movement conditions. The Kongxi burial-hill zone adjoins a potential Ordovician source kitchen. The KG-3 Ordovician burial-hill reservoir has undergone two oil filling events, i.e., an early event in the Late Carboniferous-Permian and a more significant late event in the early Eogene.展开更多
基金funded by the National Natural Science Foundation of China(Grant No.42102169)the Shaanxi Province key Research and Development Project(Grant No.2023-ZDLSF-64)+1 种基金the Scientific Research and Technological Development Project of China National Logging Corporation(Grant No.25ZYCJSG013-2504)the Youth Science and Technology Special Fund of PetroChina(Grant No.2024DQ03172)。
文摘Geological CO_(2) storage is a promising strategy for reducing greenhouse gas emissions and has become a growing focus of research and deployment.This paper presents numerical simulations of CO_(2) injection and storage in a depleted gas reservoir within the B Depression and evaluates associated CO_(2) trapping mechanisms.In the base case,a constant injection rate of 3500 m^(3)/d over fifteen years resulted in a cumulative injection of 19.2×10^(6) m^(3).The CO_(2) plume expanded radially during injection and subsequently migrated up-dip under buoyancy forces.The final stored mass of CO_(2) in the reservoir was 10.6 million tonnes(Mt),representing less than 10% of its theoretical capacity.The plume was projected to reach the entrapment crest and the top of the reservoir within a century,indicating secure long-term containment.Structural,stratigraphic,and residual trapping dominate in Reservoir A(approximately 90%).Anticlinal closures with thick overlying mudstones in the Zhujiang Formation provide effective seals,further enhancing storage security.Reservoir properties and heterogeneity play a crucial role in controlling CO_(2) storage.However,reservoir heterogeneity exerts only a limited influence when intrinsic properties are favorable.Overall,the study and implementation of CO_(2) capture,utilization,and storage(CCUS)in China's offshore basins show promising prospects.
基金supported by Research on Reservoir Formation Patterns and Risk Exploration in Key Overseas Basins(25ZYGJCJ011)。
文摘Oilfield M currently has a comprehensive water cut of 73.2%after more than 20 years of development,the reservoir is experiencing both edge-bottom water flooding and injection water flooding,with diverse types of injected water and complex flooding patterns,necessitating the research on logging evaluation methods for water-flooded layers.By introducing the variable multiple injection water material balance theory and combining it with the rock-electric relationship,an analysis of the water flooding mechanism in the study area was conducted.This led to the establishment of the variation characteristics between formation resistivity,water production rate,and saturation under different reservoir types and different salinities of injected water in the area;using the semi-permeable membrane capillary pressure experiment,the relationship between the original formation resistivity and the oil column height was established,deriving the relationship between the water production rate and the formation resistivity drop rate,combining the analysis of the water flooding mechanism mentioned above,allowing for a quantitative assessment of the level of water flooding;optimizing the mixed formation water resistivity calculation model to accurately determine parameters such as remaining oil saturation and water production rate,a set of identification and quantitative evaluation methods for waterflooded layers in Oilfield M was formed.The interpretation accuracy reached 87.5%,providing strong technical support for selecting perforation layers in the oilfield and avoiding highly flooded layers.This is of significant application value for the remaining oil evaluation and efficient development of water-flooded layers in overseas clastic rock oilfields.
基金Supported by the PetroChina Science and Technology Project (2021DJ0605,2022KT0101)the CNPC Major Science and Technology Project (2021DJ0501)。
文摘Based on the latest drilling, seismic and field outcrop data, the geological characteristics(e.g. strata, development and sedimentary evolution) of the southern segment of the Late Sinian–Early Cambrian Deyang–Anyue rift trough in the Sichuan Basin are analyzed. First, the strata in the southern segment are complete. The first to second members of Dengying Formation(Deng 1 + Deng 2) are found with relatively stable thickness(400–550 m), and the third to fourth members(Deng 3+ Deng 4) show great thickness difference between the marginal trough and the inner trough, which is up to 250 m. The Cambrian Maidiping Formation and Qiongzhusi Formation in southern Sichuan Basin are relatively thin, with the thickness changing greatly and frequently. Second, the Deyang–Anyue rift trough extended southward during the Deng 4 period, affecting southern Sichuan Basin. Compared to the middle and northern segments of the rift trough, the southern segment is generally wide, gentle and shallow, with multiple steps, and alternating uplifts and sags, which are distributed in finger shape. Third, the Deng 1 + Deng 2 in southern Sichuan Basin records the dominance of carbonate platform and unobvious sedimentary differentiation, and the Deng 4 exhibits obvious sedimentary differentiation, namely, basin–slope–secondary slope–slope–secondary slope–platform margin–restricted platform, from the inner trough to the marginal trough. Fourth, the rift trough in southern Sichuan Basin has evolved in four stages: stabilization of Deng 1–Deng 2, initialization of Deng 3–Deng 4, filling of Maidiping–Qiongzhusi, and extinction of Canglangpu Formation.
文摘Focusing on the Yangtze River economic zone,the previous geological researches are systematically summarized,resources and environment conditions and major geological problems which are needing to be concerned in land planning and construction are studied.The results show that the resource conditions of cultivated land,shale gas,geotherm,lithium and so on are superior in the Yangtze River economic zone,and the resources and environment conditions are conducive to develop the modern agriculture,clean energy industry and strategic emerging industries.3×1013 m^2 farmlands without heavy metal pollution are concentrated;there are three national level shale gas exploration and development bases with explored reserves of 5.441×1011 m^3;geothermal availability is 2.4×109 t of standard coal each year,equivalent to 19% of the amount of coal in 2014;Asia's largest energy lithium metal ore deposit is found.In some parts of Yangtze River economic zone,there are some major geological problems such as active faults,karst collapse,ground subsidence,landslide-collapse-debris flow,affecting the river-crossing channels,high-speed railway,urban agglomeration and green ecological corridor planning and construction.Those problems should be concerned,and the relevant suggestions and countermeasures are put forward.Meanwhile,the ideas to further support the development of the Yangtze River economic zone are put forward.
文摘The chemistry and migration patterns of the mantle ichor are discussed on a globle scale followed by evaluations of the significance of HACONSfluid with respect to various geological processes of fundamental interest.
文摘This paper discussed the direction of secondary migration of oil in the No. 6 area of the Melut Basin by making use of nitrogen compounds as secondary oil migration tracers. From the results, we have found that the occurrence and compositional characteristics of isomeric-nitrogen compounds in crude oil precisely manifest the fractionation effect of oil migration: with increasing secondary migration distance, the absolute concentrations tend to decrease, and the ratio of nitrogen-shielded isomers to nitrogen-exposed isomers tends to increase. It is considered that the main direction of oil migration in the No. 6 area of the Melut Basin is from north to south.
文摘The Xing’an block (XB) is located in the eastern part of the Xingmeng orogenic belt, bounded by Erguna block (EB) to northwest and the Songnen block (SB) to the southeast (Fig. 1a).
基金The work was carried out within the framework the State assignment of the Federal Agency for Subsoil Use of 27.12.2023№049-00003-24-00a State Assignment of the Sobolev Institute of Geology and Mineralogy,Russian Academy of Sciences(project no.122041400237-8).
文摘This paper presents the morphologic,chemical and other typomorphic characteristics of native gold from four placer deposits(basins of the Lev.Nora,Skalistaya and Golysheva rivers,and Loginova brook),four placer occurrences(basins of the Lagernaya,Nizh.Litke and Prokhodimaya rivers,and Tikhiy brook),and the alluvial deposit of cape Mordovin on Bolshevik island of the Severnaya Zemlya archipelago(Russia).Optical microscopy,scanning electron microscopy and electron-probe microanalysis were used in this study.Placer gold from the Lagernaya,Golysheva,Nizh.Litke and Skalistaya rivers,Tikhiy brook and cape Mordovin is characterized by a very high fineness(>988‰)in the rims and a lower fineness(860‰–970‰)in the center.Gold particles from the placers of the Lev.Nora and Prokhodimaya rivers and Loginova brook are low fineness and widely vary in the center(from 647‰to 920‰)and are high fineness(950‰–980‰)in the rims.In some gold particles from the placers of the Lev.Nora and Skalistaya rivers,zones with Cu up to 1.2 wt.%and Hg up to 2.6 wt.%are observed.Titanite,monazite,cobaltite,ulmannite,brannerite,rutile,zircon,Y-xenotime,bismuthite,native bismuth and bismuthinite,garnet(almandine),Cu-or Ni-pyrrhotite were found in the native gold from the Skalistaya and Lev.Nora placers.Native gold from the Skalistaya river placer contains mineral micro-inclusions of cobaltite,Cu,Cd-bearing sphalerite and Fe,Cu-ullmannite.Native gold from the Lev.Nora river placer differs in the presence of brannerite and bismuth minerals.On the basis of the obtained results,available metallogenic characteristics of Bolshevik island and literature data,the following types of primary sources are predicted for these locations:(1)Lev.Nora river deposits of gold-copper rare metal and porphyry gold-copper formations;(2)Skalistaya river deposits of porphyry gold-copper and gold-quartz formation;(3)all the other locations:deposits of gold-quartz and gold-sulfide-quartz formations(hosted in terrigenous carbonaceous complexes).The presence of intermediate reservoirs near some of these locations is probable.
基金supported from the Opening fund of State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development(33550000-22-ZC0613-0297)National Natural Science Foundation of China(42102196)the Natural Science Basis Research Plan in Shaanxi Province of China(2022JM-147).
文摘Pore structure directly affects the occurrence and migration of shale hydrocarbon,and the lack of research on the mechanism of the pore structure is an important reason for the hindrance of shale hydrocarbon exploration.By analysing the geochemistry and reservoir characteristics of Jurassic lacustrine shales in Sichuan Basin,this study recovers their paleoenvironments and further discusses paleoenvironmental constraints on pore structure.The results show that the Lower Jurassic lacustrine shales in the Sichuan Basin are in a warm and humid semi-anoxic to anoxic lake environment with high productivity,a strong stagnant environment,and a rapid sedimentation rate,with water depths ranging from about 11.54-55.22 m,and a mixture of type Ⅱ/Ⅲ kerogen is developed.In terms of reservoir characteristics,they are dominated by open-slit pores,and the pores are relatively complex.The percentage of mesopores is the highest,while the percentage of macropores is the lowest.Further analysis shows that paleoclimate controls the overall pore complexity and surface relaxation of shales by influencing the weathering rate of mother rocks.Paleoredox conditions control the proportion and complexity of shale pores by influencing TOC content.The research results will provide theoretical basis for improving the exploration efficiency of lacustrine shale resources and expanding exploration target areas.
基金Strategy Priority Research Program(Category B)of Chinese Academy of Sciences No.XDB0710000National Key Research and Development Program of China,No.2022YFF0801502National Natural Science Foundation of China,No.42071103,No.42471175,No.42242104。
文摘Understanding the historical development of civilization in the Western Regions of China necessitates a detailed chronology and an in-depth analysis of the developmental dynamics of Ancient Loulan City(LA).However,systematic chronological investigations of specific archaeological sites within LA remain scarce,leaving the construction and occupation dates of many sites,along with the urban extent and development phases,unclear.To address these gaps,we established the Loulan Radiocarbon Dating Database and applied the summed probability distribution(SPD)method to reconstruct the chronology of individual sites and the urban development trajectory of LA.Our findings reveal the following:(1)Between~500 BC and~200 BC,only site units LA-Ⅰand LA-Ⅷexisted,representing a nascent village phase;(2)From~200 BC to~AD 100,the construction of LA-IV marked the transition to an urban phase,as evidenced by abundant plant and animal remains that indicate a blend of agricultural and pastoral practices;(3)From~AD 100 to~AD 400,the remaining site units were constructed,occupied,and utilized,signifying the urban phase.This period saw the emergence of complex social stratification,with roles such as monks,soldiers,officials,and blacksmiths shaping the city's structure.These chronological insights provide a new understanding of LA's urban evolution,offering critical evidence for its socio-economic transformation.
基金supported by the National Key Research and Development Project of China(2020YFA0714802)the National Natural Science Foundation of China(42330809)the 111 Project of the Ministry of Science and Technology(BP0719021).
文摘The timings and geodynamic controls of Mo,Au,and Au-Mo deposits in the Xiaoqinling Orogen(>630 t Au and 115,000 t Mo),a rare Au-Mo province globally,are addressed by a combination of mineral par-ageneses,crystalline mineralogy,geochemistry,and Re-Os and U-Pb geochronology in the Dahu,Qinnan,and Yangzhaiyu deposits.The Xiaoqinling Orogen comprises an E-W-trending fold and thrust system with repeated structural reactivation and the Mo or Au orebodies in these deposits are dominantly controlled by E-W-trending and NW-SE-trending shear zones.Molybdenum mineralization related to K-feldspar alteration comprises early molybdenite,pyrite,rutile,and monazite within gray quartz veins plus late molybdenite and pyrite within white quartz veins in the Dahu and Qinnan Au-Mo deposits.Early and late Au mineralization events have similar mineral assemblages of pyrite,native gold±Au-Ag-Te minerals,rutile,and monazite associated with quartz-sericite alteration at Yangzhaiyu.The early dissem-inated molybdenite is characterized by rhombohedral polytype and oscillatory Re zoning,in contrast to the late molybdenite with a coexistence of rhombohedral and hexagonal polytypes and irregularly distributed Re.The early molybdenite has a Re-Os isochron age of 222.5±1.3 Ma,compatible with a monazite U-Pb age of 224±6.1 Ma,whereas late molybdenite provides a Re-Os isochron age of 185.0±12 Ma,with the implication that the 3R-polytype molybdenite with oscillatory Re zoning is more suitable for high-precision dating.The early and late Au mineralization have a pyrite Re-Os age of 202.0±5.9 Ma and U-Pb age of 124.0±1.3 Ma,respectively.In accordance with its complex geodynamic setting,geological and geochronological studies record a complicated 100-million-year mineralization history with multiple magmatic-hydrothermal Mo and orogenic Au mineralization events that formed within a structural framework of multiply reactivated shear zones.
基金supported by the Natural Science Foundation of Jiangxi Province,China(Grant No.20242BAB20130)the Basic Research Funds Program of the Chinese Academy of Geological Sciences(Grant No.YYWF201607)the National Natural Science Foundation of China(Grant No.41902064)。
文摘The phenomenon of'bamboo-like'thin interlayers developed in rock salt is one of the most prominent features of Paleogene salt-bearing strata in eastern China,where centimeter-thick rock salts appear separately,forming rhythmic units.At present,detailed analyses of these rhythms of rock salt are still limited,which directly affects the achievement of comprehensive and in-depth understanding of the developmental laws pertaining to this kind of saline lake.Therefore,we selected the typical rhythmic'bamboo-like'rock salts of the Shizhai Depression in Jiangsu Province as the research subject.Through careful observation of rock salts in hand samples and detailed petrographic and mineralogical analyses,we analyzed the hydrogen and oxygen isotopic compositions,homogenization temperatures and chemical compositions of individual fluid inclusions in halite crystals.Early-stage rhythmic deposition was a product of continental saline lake evolution in winter or spring,late-stage rhythmic deposition being the product of evolution in the summer.The seasonal evolution of the halite sequences was determined and two brine enrichment events were identified.In addition,the quiet saline lake environment with concentrated brine represented by rock salt was more likely to precipitate potassium.This study provides a new reference for the evolution of both Paleogene climate and saline lakes in eastern China.
基金supported by the China Major National Scientific and Technological Project(No.2011ZX05001)
文摘Petroleum exploration targets are extending gradually from the single conventional trap reservoirs to the large-scale unconventional continuous accumulations. Oil and gas reservoirs have been divided into two types based on the trapping mechanism and distribution of oil and gas： conven- tional single-trap reservoirs, such as the Daqing oil field in Songliao Basin and the Kela-2 gas field in Tarim Basin; and unconventional continuous petroleum accumulation, such as Upper Paleozoic tight gas and Mesozoic tight oil in Ordos Basin, and Upper Triassic tight gas in Sichuan Basin. Two typical geologic characteristics of continuous petroleum accumulation involve： （1） coexisting source and reser- voir, petroleum pervasive throughout a large area tight reservoirs, and no obvious traps or well-defined water-oil and gas contracts; （2） non-buoyancy accumulation, continuous petroleum charge, and no sig- nificant influence by buoyancy. Continuous petroleum accumulation generally have nm-scale pore throats, and the diameters range of 10-500 nm. The geometry and connectivity of these pore throats has significant impact on the migration and distribution of oil and gas in continuous petroleum accu- mulation. China has numerous continuous petroleum accumulation containing various petroleum de- posits, and the exploration of continuous resources is very promising. Unconventional petroleum geol- ogy will become an important new subject in petroleum geology in future, and the nano-technology will function greatly on research, exploration and development of the hydrocarbon accumulation in nano-pore-throats.
基金financially supported by the China Geological Survey(Nos.12120115069701,12120113095700 and 1212011220391)the National Natural Science Foundation of China(No.41272079)+2 种基金the China Postdoctoral Science Foundation-China(No.2015M582529)the State Key Laborato-ry of Continental Tectonics and Dynamics(No.K201508)the Special Financial Support Program of Central Government for Local Universities(No.80000-14Z019)
文摘This study reports zircon U-Pb and Hf isotopes and whole-rock elemental data for granodiorites from the East Kunlun orogen. The zircon U-Pb dating defines their crystallization age of 235 Ma. The rocks are characterized by high-K calc-alkaline, magnesian and metaluminous with（K2O＋Na2O）=6.38 wt.%–7.01 wt.%, Mg#=42–50 [Mg#=100×molar Mg/（Mg＋Fe OT）], A/CNK=0.92–0.98, coupled with high εHf（t） values from-0.65 to-1.80. The rocks were derived from partial melting of a juvenile mafic crustal source within normal crust thickness. The juvenile lower crust was generated by mixing lithospheric mantle-derived melt（55%–60%） and supracrustal melt（40%–45%） during the seafloor subduction. Together with available data from the East Kunlun, it is proposed that the studied Middle Triassic granodiorites were formed in post-collisional extension setting, in which melting of the juvenile lower crust in response to the basaltic magma underplating resulted in the production of high-K granodioritic melts.
文摘The Qom Formation comprises Oligo-Miocene deposits from a marine succession distributed in the Central Basin of Iran. It is composed of five members designated as A-F. Little previous work exists on the sequence stratigraphy. Based on an integrated study of sequence stratigraphy with outcrop data, wells and regional seismic profiles, the Qom Formation is interpreted as a carbonate succession deposited in a mid.Tertiary back-arc basin. There are two second-order sequences （designated as SS1 and SS2） and five third-order sequences （designated as S1-S5）. Five distinct systems tracts including transgressive, highstand, forced regressive, slope margin and Iowstand have been recognized. The relationship between the sequences and lithologic sub-units has been collated and defined （S1 to S5 individually corresponding to A-C1, C2--C4, D-E, the lower and upper portions of F）; a relative sea level change curve and the sequence stratigraphic framework have been established and described in detail. The coincidence of relative sea level change between that of the determined back-arc basin and the world indicates that the sedimentary cycles of the Qom Formation are mainly controlled by eustatic cycles. The variable combination of the systems tracts and special tectonic-depositional setting causally underpin multiple sequence stratigraphic framework styles seen in the carbonates of the back-arc basin revealing： （1） a continental margin basin that developed some form of barrier, characterized by the development of multiple cycles of carbonate-evaporites; （2） a flat carbonate ramp, which occurred on the southern shelf formed by the lack of clastic supply from nearby magmatic islands plus mixed siliciclastics and carbonates that occurred on the northern shelf due to a sufficient clastics supply from the land; and （3） a forced regressive stratigraphic stacking pattern that occured on the southern shelf and in basin lows due to the uplifting of the southern shelf. Thick and widespread aggradational framework limestone usually occurs in the initial sequences （S1 and S3） of the supersequence, which led to preferential oil reservoir deposition but a lack of source and cap rocks, whereas the retrogradational and progradational framework limestone usually occurs in the later sequences （S2 and S4-S5） of the supersequence, which results in two perfect sets of source, reservoir and cap rock assemblies, so that the limestone in sub-member C2-C4 and the F-Member can be predicted as important objects for oil exploration.
基金supported by the Department of Science&Technology of Guangdong Province(No.2019ZT08G315)the open foundation of Key Laboratory of Deep Earth Science and Engineering(Sichuan University)+3 种基金Ministry of Education(No.DESE202102)National Natural Science Foundation of China(Nos.41972288,51804203,and 51827901)Applied Basic Research Programs of Sichuan Province(No.2021YJ0411)Shenzhen City Clean Energy Research Institute。
文摘During the development of hot dry rock,the research on thermal fatigue damage caused by thermal shock of cold and heat cycles is the basis that ensures the long-term utilization of geothermal resources,but there are not enough relevant studies at present.Based on this,the thermal damage tests of granite at different temperatures(250,350,450°C)and quenching cycles(1,5,10,15 cycles)were carried out.Preliminary reveals the damage mechanism and heat transfer law of the quenching cycle effect on hot dry rock.The results show that with the increase of temperature and cycles,the uneven thermal expansion of minerals and the thermal shock caused by quenching promote the crack development of granite,resulting in the decrease of P-wave velocity,thermal conductivity and uniaxial compressive strength of granite.Meanwhile,the COMSOL was used to simulate the heat transfer of hot dry rock under different heat treatment conditions.It concluded that the increase in the number of quenching cycles reduced the heat transfer capacity of the granite,especially more than 10 quenching cycles,which also reflects that the thermal fatigue damage leads to a longer time for the temperature recovery of the hot dry rock mass.In addition,the three-dimensional nonlinear fitting relationship among thermal conductivity,temperature and cycle number was established for the first time,which can better reveal the change rule of thermal conductivity after quenching thermal fatigue effect of hot dry rock.The research results provide theoretical support for hot dry rock reservoir reconstruction and production efficiency evaluation.
基金co-funded by the National Natural Science Foundation of China (41102058)the National Science and Technology Special Grant (2011ZX05006-003)the Fundamental Research Funds for the Central Universities (12CX04001A)
文摘Diagenetic traps in conglomerate in nearshore subaqueous fans in the steep slope zones of rift basins have been important exploration targets for subtle reservoirs in eastern China. However, the mechanism of how those traps were formed is not clear, which inhibits further exploration for this type of reservoir. In order to solve the problem, we take as an example nearshore subaqueous fans in the upper part of the fourth member of the Shahejie Formation （Es4s） on the north slope of the Minfeng Subsag in the Dongying Sag. Combining different research methods, such as core observation, thin section examination, scanning electron microscope （SEM） observation, fluid-inclusion analysis, carbon and oxygen isotope analysis of carbonate cements, and analysis of core properties, we studied the genetic mechanisms of diagenetic traps on the basis of diagenetic environment evolution and diagenetic evolution sequence in different sub/micro-facies. Conglomerate in Es4s in the north Minfeng Subsag experienced several periods of transition between alkaline and acidic environments as ＂alkaline-acidic-alkaline-acidic-weak alkaline＂. As a result, dissolution and cementation are also very complex, and the sequence is ＂early pyrite cementation / siderite cementation / gypsum cementation / calcite and dolomite cementation- feldspar dissolution / quartz overgrowth quartz dissolution / ferroan calcite cementation / ankerite cementation / lime-mud matrix recrystallization / feldspar overgrowth carbonate dissolution / feldspar dissolution / quartz overgrowth / pyrite cementation＂. The difference in sedimentary characteristics between different sub/micro-facies of nearshore subaqueous fans controls diagenetic characteristics. Inner fan conglomerates mainly experienced compaction and lime-mud matrix recrystallization, with weak dissolution, which led to a reduction in the porosity and permeability crucial to reservoir formation. Lime-mud matrix recrystallization results in a rapid decrease in porosity and permeability in inner fan conglomerates in middle-to-deep layers. Because acid dissolution reworks reservoirs and hydrocarbon filling inhibits cementation, reservoirs far from mudstone layers in middle fan braided channels develop a great number of primary pores and secondary pores, and are good enough to be effective reservoirs of hydrocarbon. With the increase of burial depth, both the decrease of porosity and permeability of inner fan conglomerates and the increase of the physical property difference between inner fans and middle fans enhance the quality of seals in middle-to-deep layers. As a result, inner fan conglomerates can be sealing layers in middle-to-deep buried layers. Reservoirs adjacent to mudstones in middle fan braided channels and reservoirs in middle fan interdistributaries experienced extensive cementation, and tight cemented crusts formed at both the top and bottom of conglomerates, which can then act as cap rocks. In conclusion, diagenetic traps in conglomerates of nearshore subaqueous fans could be developed with inner fan conglomerates as lateral or vertical sealing layers, tight carbonate crusts near mudstone layers in middle fan braided channels as well as lacustrine mudstones as cap rocks, and conglomerates far from mudstone layers in middle fan braided channels as reservoirs. Lime-mud matrix recrystallization of inner fan conglomerates and carbonate cementation of conglomerates adjacent to mudstone layers in middle fan braided channels took place from 32 Ma B.R to 24.6 Ma B.P., thus the formation of diagenetic traps was from 32 Ma B.R to 24.6 Ma B.R and diagenetic traps have a better hydrocarbon sealing ability from 24 Ma B.P.. The sealing ability of inner fans gradually increases with the increase of burial depth and diagenetic traps buried more than 3,200 m have better seals.
基金jointly supported by grants from the Natural Science Foundation of China(grants No.41402110 and 41330313)“Fundamental Research Funds for the Central Universities”(grants No.14CX05017A and 13CX05013A)
文摘Lacustrine shale from the Qingshankou Formatin of Songliao basin and the Shahejie Formation of Bohai Bay basin, and marine shale from the lower Cambrian Jinmenchong Formation of Qiannan depression were analysed by using rock pyrolysis, TOC （total organic carbon）, XRD （X-ray diffraction）, SEM （scanning electron microscope）, FE-SEM （field emission scanning electron microscope）, high pressure mercury intrusion, and low pressure N2 and CO2 gas adsorption experiments, in aim to reveal their reservoir features. The results show that： （1） the width of micro-pores of all the studied samples mainly ranges from 0.45 to 0.7 nm indicated by CO2 isotherms, and the width of meso-pores is less than 10 nm, with type IV adsorption isotherms and type H2 hysteresis loop, indicative of ＂ink-bottle＂-shaped pores. Good correlations exist among pore volume, surface area and averaged pore diameter, and a good positive correlation exists between micro-pore volume and TOC content; however, there is no obvious correlation between meso-pore volume and TOC content; （2） interparticle pores, pores among the edge of mineral grains and organic matter pores were all identified in marine and lacustrine shale, among which the interparticle pores may be influence by dissolution effect. Not all bitumen develops organic matter pore, and only high to over mature bitumen present pores. Now the description methods of micrometer scale pores developed in shale are very lack. Micro- fractures developed in Jiyang depression and dissolution interparticle pores developed in Songliao Basin should be the accumulation sites for shale oil in lacustrine shale, and can be as sweet spots.
文摘An oil flow obtained from the Middle Ordovician Fengfeng Formation carbonate reservoir in the well KG-3, Kongxi burial-hill zone in 1993 marked a breakthrough in petroleum exploration of the high-mature Lower Palaeozoic strata, North China. Both the Lower member of the Fengfeng Formation and the Second Member of the Upper Majiagou Formation in the Middle Ordovician are supposed to be the main source beds. Oil generation peaks range from 1.0% to 1.6% in Ro, showing a “lag effect” of oil generation in high-mature carbonate source rocks under multicyclic tectonic movement conditions. The Kongxi burial-hill zone adjoins a potential Ordovician source kitchen. The KG-3 Ordovician burial-hill reservoir has undergone two oil filling events, i.e., an early event in the Late Carboniferous-Permian and a more significant late event in the early Eogene.
