Deep fluids in a petroliferous basin generally come from the deep crust or mantle beneath the basin basement,and they transport deep substances(gases and aqueous solutions)as well as heat to sedimentary strata through...Deep fluids in a petroliferous basin generally come from the deep crust or mantle beneath the basin basement,and they transport deep substances(gases and aqueous solutions)as well as heat to sedimentary strata through deep faults.These deep fluids not only lead to large-scale accumulations of CO_(2),CH4,H2,He and other gases,but also significantly impact hydrocarbon generation and accumulation through organic-inorganic interactions.With the development of deep faults and magmatic-volcanic activities in different periods,most Chinese petroliferous basins have experienced strong impacts associated with deep fluid activity.In the Songliao,Bohai Bay,Northern Jiangsu,Sanshui,Yinggehai and Pearl Mouth Basins in China,a series of CO_(2)reservoirs have been discovered.The CO_(2)content is up to 99%,withδ-(13)C(CO_(2))values ranging from-4.1‰to-0.37‰and-3He/-4He ratios of up to 5.5 Ra.The abiogenic hydrocarbon gas reservoirs with commercial reserves,such as the Changde,Wanjinta,Zhaozhou,and Chaoyanggou reservoirs,are mainly distributed in the Xujiaweizi faulted depression of the Songliao Basin.Theδ-(13)CCH4 values of the abiogenic alkane gases are generally-30‰and exhibit an inverse carbon isotope sequence ofδ-(13)C(CH4)δ-(13)C(C2H6)δ-(13)C(C3H8)δ-(13)C(C4H10).According to laboratory experiments,introducing external H2 can improve the rate of hydrocarbon generation by up to 147%through the kerogen hydrogenation process.During the migration from deep to shallow depth,CO_(2)can significantly alter reservoir rocks.In clastic reservoirs,feldspar is easily altered by CO_(2)-rich fluids,leading to the formation of dawsonite,a typical mineral in high CO_(2)partial pressure environments,as well as the creation of secondary porosity.In carbonate reservoirs,CO_(2)-rich fluids predominately cause dissolution or precipitation of carbonate minerals.The minerals,e.g.,calcite and dolomite,show some typical features,such as higher homogenization temperatures than the burial temperature,relatively high concentrations of Fe and Mn,positive Eu anomalies,depletion of 18 O and enrichment of radiogenic-(87)Sr.Due to CO_(2)-rich fluids,the development of high-quality carbonate reservoirs is extended to deep strata.For example,the Well TS1 in the northern Tarim Basin revealed a high-quality Cambrian dolomite reservoir with a porosity of 9.1%at 8408 m,and the Well ZS1 C in the central Tarim Basin revealed a large petroleum reserve in a Cambrian dolomite reservoir at-6900 m.During the upward migration from deep to shallow basin strata,large volumes of supercritical CO_(2)may extract petroleum components from hydrocarbon source rocks or deep reservoirs and facilitate their migration to shallow reservoirs,where the petroleum accumulates with the CO_(2).Many reservoirs containing both supercritical CO_(2)and petroleum have been discovered in the Songliao,Bohaiwan,Northern Jiangsu,Pearl River Mouth and Yinggehai Basins.The components of the petroleum trapped with CO_(2)are dominated by low molecular weight saturated hydrocarbons.展开更多
Songyuan is the most earthquake prone area in northeast China.Since 2006,earthquakes have occurred in the area in the form of swarms,with a maximum magnitude of M_L5.8.There is much controversy about the cause of the ...Songyuan is the most earthquake prone area in northeast China.Since 2006,earthquakes have occurred in the area in the form of swarms,with a maximum magnitude of M_L5.8.There is much controversy about the cause of the Songyuan earthquakes.We attempted to determine the cause using a three-dimensional electrical conductivity structure inverted from a regional network of magnetotelluric data in the Songyuan area.The L-BFGS inversion method was applied,with a fullimpedance tensor data set used as the inversion input.Combined with an evaluation of the earthquake locations,the resistivity model revealed a northeast-oriented hidden fault running through the Songyuan earthquake area(SEA),which was speculated to be the preexisting Fuyu-Zhaodong Fault(FZF).Our resistivity model also found an apparent lithospheric low-resistivity anomaly beneath the earthquake area,which breached the high-resistivity lithospheric mantle and stalled at the base of the crust.A petrophysical analysis showed that this lower crustal low-resistivity anomaly was most likely attributed to hydrated partial melting,which could release water into the lower crust during later magma emplacements.While weakening the strength of the FZF,these ascending fluids also increased the pore pressure in the fault,further reducing the shear strength of the fault.Shear stress action(a fault strike component of the east-west regional compress),together with possible near-surface disturbances,may drive the fault to slip and trigger the earthquakes in Songyuan.It is possible that the continuous replenishment of fluids from the deeper mantle forces the Songyuan earthquakes into the form of swarms.We infer that the Songyuan earthquakes could be attributed to a combination of preexisting faults,regional stress,and deep fluids associated with plate subduction,and near surface disturbances might induce the earthquakes in advance.The Songyuan earthquakes are inherently induced earthquakes,fed by deep fluids.展开更多
Based on studies of petrography, mineralogy and mineral chemistry, deep mantle fluids and their products in kimberlites and diamonds can be assorted into the ultradeep fluid-transmitted minerals with an oxygen-free fe...Based on studies of petrography, mineralogy and mineral chemistry, deep mantle fluids and their products in kimberlites and diamonds can be assorted into the ultradeep fluid-transmitted minerals with an oxygen-free feature, the deep fluid metasomatized-minerals characterized by enrichment in TiO2, K2O, BaO, REE and Fe3+, and the deep fluid-reformed minerals. The three types show a successive descent in fluid origin depth and metasomatism strength, and they have brought forth a series of corresponding metasomatic products.展开更多
Based on the geochemical parameters and analytical data,the heat conservation equation,mass balance law,Rayleigh fractionation model and other methods were used to quantify the in-situ yield and external flux of crust...Based on the geochemical parameters and analytical data,the heat conservation equation,mass balance law,Rayleigh fractionation model and other methods were used to quantify the in-situ yield and external flux of crust-derived helium,and the initial He concentration and thermal driving mechanism of mantle-derived helium,in the Ledong Diapir area,the Yinggehai Basin,in order to understand the genetic source,migration and accumulation mechanisms of helium under deep thermal fluid activities.The average content of mantle-derived He is only 0.0014%,the ^(3)He/^(4)He value is(0.002–2.190)×10^(−6),and the R/Ra value ranges from 0.01 to 1.52,indicating the contribution of mantle-derived He is 0.09%–19.84%,while the proportion of crust-derived helium can reach over 80%.Quantitative analysis indicates that the crust-derived helium is dominated by external input,followed by in-situ production,in the Ledong diapir area.The crust-derived helium exhibits an in-situ 4 He yield rate of(7.66–7.95)×10^(−13)cm^(3)/(a·g),an in-situ 4 He yield of(4.10–4.25)×10^(−4)cm^(3)/g,and an external 4 He influx of(5.84–9.06)×10^(−2)cm^(3)/g.These results may be related to atmospheric recharge into formation fluid and deep rock-water interactions.The ratio of initial mole volume of 3 He to enthalpy(W)is(0.004–0.018)×10^(−11) cm^(3)/J,and the heat contribution from the deep mantle(X_(M))accounts for 7.63%–36.18%,indicating that deep hot fluid activities drive the migration of mantle-derived 3 He.The primary helium migration depends on advection,while the secondary migration is controlled by hydrothermal degassing and gas-liquid separation.From deep to shallow layers,the CO_(2/3) He value rises from 1.34×10^(9)to 486×10^(9),indicating large amount of CO_(2)has escaped.Under the influence of deep thermal fluid,helium migration and accumulation mechanisms include:deep heat driven diffusion,advection release,vertical hydrothermal degassing,shallow lateral migration,accumulation in traps far from faults,partial pressure balance and sealing capability.展开更多
Heat carried by deep fluid might greatly affect hydrocarbon generation and pore space in shale.Dyke intrusion carrying high levels of heat may be a means by which to explore the influence of deep fluid on shale reserv...Heat carried by deep fluid might greatly affect hydrocarbon generation and pore space in shale.Dyke intrusion carrying high levels of heat may be a means by which to explore the influence of deep fluid on shale reservoirs.This study evaluates hydrocarbon generation and analyzed the evolution of shale storage space in the third member of the Xiamaling Formation in the Zhaojiashan section,Hebei Province,based on experimental data such as TOC,SEM,VRo,low-temperature N_(2)adsorption and high-pressure mercury injection.The results show that the dyke intrusion reduced the shale TOC content drastically―by up to 77%―and also induced instantaneous hydrocarbon generation over a range about 1.4 times the thickness of the intrusion.Furthermore,the dyke intrusion might transform organic pores in surrounding shales into inorganic pores.There were two shale porosity peaks:one appeared when VRo=2.0%,caused by the increase of organic pores as thermal maturity increased,the other occurred when the VRo value was between 3%and 4%,caused by the increase of inorganic mineral pores.It can be concluded that dyke intrusion can be an effective tool with which to study how deep fluid affects instantaneous hydrocarbon generation and pore space in shale.展开更多
Hydrogen gas accelerates hydrocarbon generation, but little is known about its distribution and origin in petroliferous basins, which has hindered the further exploration.Taken the Jiyang Depression in eastern China a...Hydrogen gas accelerates hydrocarbon generation, but little is known about its distribution and origin in petroliferous basins, which has hindered the further exploration.Taken the Jiyang Depression in eastern China as an example, this study collected natural gas from different tectonic units, and analyzed various geochemical characters including gas contents, and carbon and hydrogen isotopic composition.The result shows that：（1） hydrogen gas is widespread distributed, but its content is very low, which typically ranges from 0.01% to 0.1% in this region;（2） the ratios of H2/3He, indicative of the origins of hydrogen gas, suggest that mantle-derived hydrogen is dominant.Even in tectonically stable areas absent with deep fluid activities, there is also mantle-derived;（3） the isotopic composition of hydrogen falls in the range of –798‰ to –628‰（relative to VSMOW standard）.In areas with deep-derived fluids, the hydrogen gas has a similar isotopic composition with the previously documented deep-sourced gas, with lighter isotopic composition.In contrast, hydrogen gas has a heavier isotopic composition in relatively stable areas.The isotopic signatures suggest that there is a mixture of mantle- and crust-derived hydrogen gas in the relatively stable area, which is consistent with the H2/3He ratios.Therefore, it is clear that the hydrogen gas has a much wider distribution than found in the deep-derived fluid area, resulting in a much broader area with hydrogenating effect for resource rock.This understanding will provide new insights for hydrocarbon generation research and resource assessment in petroliferous basins.展开更多
This study analyzed and summarized in detail the spatial and temporal distributions of earthquakes,tidal responses,focal mechanisms,and stress field characteristics for the M 7.3 Haicheng earthquake sequence in Februa...This study analyzed and summarized in detail the spatial and temporal distributions of earthquakes,tidal responses,focal mechanisms,and stress field characteristics for the M 7.3 Haicheng earthquake sequence in February 1975.The foreshocks are related to the main fault and the conjugate faults surrounding the extension step-over in the middle.The initiation timing of the foreshock clusters and the original time of the mainshock were clearly modulated by the Earth's tidal force and coincided with the peak of dilational volumetric tidal strain.As a plausible and testable hypothesis,we proposed a fluid-driven foreshock model,by which all observed seismicity features can be more reasonably interpreted with respect to the results of existing models.Together with some other known examples,the widely existing step-over along strike-slip faults and associated conjugate faults,especially for extensional ones in the presence of deep fluids,favor the occurrence of short-term foreshocks.Although clustered seismicity with characteristics similar to those of the studied case is not a sufficient and necessary condition for large earthquakes to occur under similar tectonic conditions,it undoubtedly has a warning significance for the criticality of the main fault.Subsequent testing would require quantification of true/false positives/negatives.展开更多
On February 3rd,2020,an isolated MS5.1 earthquake occurred in the northern section of the Longquanshan fault zone.This study aims at defining the geometry of seismogenic structures of this earthquake.In detail,centroi...On February 3rd,2020,an isolated MS5.1 earthquake occurred in the northern section of the Longquanshan fault zone.This study aims at defining the geometry of seismogenic structures of this earthquake.In detail,centroid moment tensor inversion results show that the earthquake is characterized by a focal depth of 3.8 km with no corresponding surface faults.The strike/dip/rake angles for the two nodal planes are 205°/54°/96°and 15°/36°/82°,respectively.With the analyses of coseismic deformation of the surface obtained from InSAR measurements,together with the information of relocated hypocenters for a small number of aftershocks,it is concluded that a northwest-dipping nodal plane corresponds well to the source fault.The fault is suggested to have a length of about 2.8 km and a depth range of 2-5 km,and the centroid of the earthquake is located at 104.48°E and 30.71°N.Furthermore,multiple pieces of evidence indicate that this earthquake is partly driven by the overpressure effect associated with the adjacent natural gas packets,which is similar to several other moderate natural earthquakes in Sichuan Basin.展开更多
Using hypocenter relocation,moment tensor inversion,stress field inversion,and fault slip tendency analysis,this study systematically investigated three M5.5-5.8 earthquake sequences that occurred after 2000 in the Yo...Using hypocenter relocation,moment tensor inversion,stress field inversion,and fault slip tendency analysis,this study systematically investigated three M5.5-5.8 earthquake sequences that occurred after 2000 in the Yongning-Luguhu faulted basin in the middle of the Lijiang-Xiaojinhe fault zone within the Sichuan-Yunnan block,Southwest China.Our results show that since the 2008 Wenchuan earthquake,the tectonic stress pattern in this area may have changed and that b-values estimated for the earthquake sequences show evidence of an increasing trend in stress in the study area.Seismicity in the small-scale faulted basin adjacent to the large-scale fault zone is a possible indicator of regional stress.We also note that the aftershocks of the M5.7 earthquake sequence in 2012 and the M5.5 earthquake sequence in 2022 show relatively clear fluid diffusion-triggering characteristics.Overpressure of deep fluids is still the main factor driving seismic activity in the region,and we propose that the background tectonic stresses have not yet reached critical levels.展开更多
Longling is characterized by a wide distribution of hydrothermal areas, among which the Banglazhang hydrothermal system is the most geothermally active. Banglazhang is marked by intensive hydrothermal activities inclu...Longling is characterized by a wide distribution of hydrothermal areas, among which the Banglazhang hydrothermal system is the most geothermally active. Banglazhang is marked by intensive hydrothermal activities including hot springs, geysers, fumaroles and hydrothermal explosions. The geothermal waters from the Longling region are mainly HCO3-Na type with low but comparable SO4 and Cl concentrations. Calculations based on a variety of chemical geothermometers and a K-Ca geobarometer indicate that the Banglazhang hydrothermal system has much higher subsurface temperature and CO2 pressure compared to the other systems such as Daheba, Dazhulin and Huangcaoba. However, geothermal water samples collected from all these alternative hydrothermal areas are either partially equilibrated with reservoir minerals or are immature. The silica-enthalpy relationships of Banglazhang geothermal waters indicate the presence of a deep geothermal fluid with an enthalpy value and silica concentration of 945 J/g（up to around 220 °C） and 339 mg/L. Our work indicates the Banglazhang area is a promising source in terms of long-term utilization of hydrothermal resources.展开更多
Based on the analysis of the natural gas samples of 146 wells from four major petroliferous basins of China,the source and distribution of mercury in natural gas in major petroliferous basins of China were identified....Based on the analysis of the natural gas samples of 146 wells from four major petroliferous basins of China,the source and distribution of mercury in natural gas in major petroliferous basins of China were identified.Studies have shown that the mercury concentration of natural gas in petroliferous basins of China varies widely,ranging from 0.01 to 4050μg/m^3.The gas well with the highest mercury concentration is in the Xushen gas field in the Songliao Basin.The mercury concentration in the craton basin is relatively low,and the secondary gas reservoir in the Tarim Basin has the lowest mercury concentration.In the rift basin,due to the presence of deep faults which cut the basement and mixing effects of deep fluids,the mercury concentration in natural gas may be abnormally high,e.g.the Xushen gas field in the Songliao Basin.In relatively stable basins where deep and large faults do not develop,mercury is primarily of organic origin.In rift basins where deep fluids are mixed with gas reservoirs,mercury in natural gas may mainly come from the deep fluids and is characterized by abnormally high mercury concentration and R/Ra values.展开更多
Five sequences of deep fluid injections at the Pohang Enhanced Geothermal System(EGS)triggered an ML 5.4 earthquake on November 15,2017.The foreshock-mainshock-aftershock sequence was monitored using dense seismic net...Five sequences of deep fluid injections at the Pohang Enhanced Geothermal System(EGS)triggered an ML 5.4 earthquake on November 15,2017.The foreshock-mainshock-aftershock sequence was monitored using dense seismic networks.Between November 14,2017,and May 31,2023,this study detected 5,169 earthquakes and determined the relative locations of 4,902 earthquakes,including seven foreshocks.A heterogeneous subsurface fault model is proposed,in which the fault is reactivated by induced and triggered earthquakes.The earthquake frequency decreased after the mainshock,with a temporary increase after the ML 4.6 event on February 10,2018.The magnitude-frequency b-values are significantly lower than those for the background seismicity in the Korean Peninsula and those for the 2016 Gyeongju earthquake sequence.The aftershock decay rate p-values are within the range of typical values,regardless of decreasing over time.The earthquake focal mechanisms exhibit a predominance of strike-slip components,whereas the slip tendency indicates a higher value in reverse faulting geometry,implying stress redistribution after the mainshock.The seismic landscape with ongoing aftershock activity after the 2017 Pohang earthquake underscores the importance of sustained,long-term seismic monitoring to comprehensively grasp the implications of the new seismic environment for seismic hazards in the area.展开更多
基金financially supported by the National Natural Science Foundation of China(grants No.41230312,U1663209,41372149 and 41625009)the Key Project of China National Program for Fundamental Research and Development(973 Program,grant No.2012CB214800)
文摘Deep fluids in a petroliferous basin generally come from the deep crust or mantle beneath the basin basement,and they transport deep substances(gases and aqueous solutions)as well as heat to sedimentary strata through deep faults.These deep fluids not only lead to large-scale accumulations of CO_(2),CH4,H2,He and other gases,but also significantly impact hydrocarbon generation and accumulation through organic-inorganic interactions.With the development of deep faults and magmatic-volcanic activities in different periods,most Chinese petroliferous basins have experienced strong impacts associated with deep fluid activity.In the Songliao,Bohai Bay,Northern Jiangsu,Sanshui,Yinggehai and Pearl Mouth Basins in China,a series of CO_(2)reservoirs have been discovered.The CO_(2)content is up to 99%,withδ-(13)C(CO_(2))values ranging from-4.1‰to-0.37‰and-3He/-4He ratios of up to 5.5 Ra.The abiogenic hydrocarbon gas reservoirs with commercial reserves,such as the Changde,Wanjinta,Zhaozhou,and Chaoyanggou reservoirs,are mainly distributed in the Xujiaweizi faulted depression of the Songliao Basin.Theδ-(13)CCH4 values of the abiogenic alkane gases are generally-30‰and exhibit an inverse carbon isotope sequence ofδ-(13)C(CH4)δ-(13)C(C2H6)δ-(13)C(C3H8)δ-(13)C(C4H10).According to laboratory experiments,introducing external H2 can improve the rate of hydrocarbon generation by up to 147%through the kerogen hydrogenation process.During the migration from deep to shallow depth,CO_(2)can significantly alter reservoir rocks.In clastic reservoirs,feldspar is easily altered by CO_(2)-rich fluids,leading to the formation of dawsonite,a typical mineral in high CO_(2)partial pressure environments,as well as the creation of secondary porosity.In carbonate reservoirs,CO_(2)-rich fluids predominately cause dissolution or precipitation of carbonate minerals.The minerals,e.g.,calcite and dolomite,show some typical features,such as higher homogenization temperatures than the burial temperature,relatively high concentrations of Fe and Mn,positive Eu anomalies,depletion of 18 O and enrichment of radiogenic-(87)Sr.Due to CO_(2)-rich fluids,the development of high-quality carbonate reservoirs is extended to deep strata.For example,the Well TS1 in the northern Tarim Basin revealed a high-quality Cambrian dolomite reservoir with a porosity of 9.1%at 8408 m,and the Well ZS1 C in the central Tarim Basin revealed a large petroleum reserve in a Cambrian dolomite reservoir at-6900 m.During the upward migration from deep to shallow basin strata,large volumes of supercritical CO_(2)may extract petroleum components from hydrocarbon source rocks or deep reservoirs and facilitate their migration to shallow reservoirs,where the petroleum accumulates with the CO_(2).Many reservoirs containing both supercritical CO_(2)and petroleum have been discovered in the Songliao,Bohaiwan,Northern Jiangsu,Pearl River Mouth and Yinggehai Basins.The components of the petroleum trapped with CO_(2)are dominated by low molecular weight saturated hydrocarbons.
基金supported by the National High Technology Research and Development Program of China(863 Program)(Grant No.2014AA06A601)the National Project for the Development of Major Scientific Instruments(Grant No.2011YQ05006010)。
文摘Songyuan is the most earthquake prone area in northeast China.Since 2006,earthquakes have occurred in the area in the form of swarms,with a maximum magnitude of M_L5.8.There is much controversy about the cause of the Songyuan earthquakes.We attempted to determine the cause using a three-dimensional electrical conductivity structure inverted from a regional network of magnetotelluric data in the Songyuan area.The L-BFGS inversion method was applied,with a fullimpedance tensor data set used as the inversion input.Combined with an evaluation of the earthquake locations,the resistivity model revealed a northeast-oriented hidden fault running through the Songyuan earthquake area(SEA),which was speculated to be the preexisting Fuyu-Zhaodong Fault(FZF).Our resistivity model also found an apparent lithospheric low-resistivity anomaly beneath the earthquake area,which breached the high-resistivity lithospheric mantle and stalled at the base of the crust.A petrophysical analysis showed that this lower crustal low-resistivity anomaly was most likely attributed to hydrated partial melting,which could release water into the lower crust during later magma emplacements.While weakening the strength of the FZF,these ascending fluids also increased the pore pressure in the fault,further reducing the shear strength of the fault.Shear stress action(a fault strike component of the east-west regional compress),together with possible near-surface disturbances,may drive the fault to slip and trigger the earthquakes in Songyuan.It is possible that the continuous replenishment of fluids from the deeper mantle forces the Songyuan earthquakes into the form of swarms.We infer that the Songyuan earthquakes could be attributed to a combination of preexisting faults,regional stress,and deep fluids associated with plate subduction,and near surface disturbances might induce the earthquakes in advance.The Songyuan earthquakes are inherently induced earthquakes,fed by deep fluids.
基金the National Natural Foundation of China grants 40273016 , 49973013
文摘Based on studies of petrography, mineralogy and mineral chemistry, deep mantle fluids and their products in kimberlites and diamonds can be assorted into the ultradeep fluid-transmitted minerals with an oxygen-free feature, the deep fluid metasomatized-minerals characterized by enrichment in TiO2, K2O, BaO, REE and Fe3+, and the deep fluid-reformed minerals. The three types show a successive descent in fluid origin depth and metasomatism strength, and they have brought forth a series of corresponding metasomatic products.
基金Supported by the National Natural Science Foundation of China(41821002,42272163,42072167)Laoshan Laboratory Science and Technology Innovation Project(LSKJ202203403)Hainan Branch Project of CNOOC(KJZH-2021-0003-00).
文摘Based on the geochemical parameters and analytical data,the heat conservation equation,mass balance law,Rayleigh fractionation model and other methods were used to quantify the in-situ yield and external flux of crust-derived helium,and the initial He concentration and thermal driving mechanism of mantle-derived helium,in the Ledong Diapir area,the Yinggehai Basin,in order to understand the genetic source,migration and accumulation mechanisms of helium under deep thermal fluid activities.The average content of mantle-derived He is only 0.0014%,the ^(3)He/^(4)He value is(0.002–2.190)×10^(−6),and the R/Ra value ranges from 0.01 to 1.52,indicating the contribution of mantle-derived He is 0.09%–19.84%,while the proportion of crust-derived helium can reach over 80%.Quantitative analysis indicates that the crust-derived helium is dominated by external input,followed by in-situ production,in the Ledong diapir area.The crust-derived helium exhibits an in-situ 4 He yield rate of(7.66–7.95)×10^(−13)cm^(3)/(a·g),an in-situ 4 He yield of(4.10–4.25)×10^(−4)cm^(3)/g,and an external 4 He influx of(5.84–9.06)×10^(−2)cm^(3)/g.These results may be related to atmospheric recharge into formation fluid and deep rock-water interactions.The ratio of initial mole volume of 3 He to enthalpy(W)is(0.004–0.018)×10^(−11) cm^(3)/J,and the heat contribution from the deep mantle(X_(M))accounts for 7.63%–36.18%,indicating that deep hot fluid activities drive the migration of mantle-derived 3 He.The primary helium migration depends on advection,while the secondary migration is controlled by hydrothermal degassing and gas-liquid separation.From deep to shallow layers,the CO_(2/3) He value rises from 1.34×10^(9)to 486×10^(9),indicating large amount of CO_(2)has escaped.Under the influence of deep thermal fluid,helium migration and accumulation mechanisms include:deep heat driven diffusion,advection release,vertical hydrothermal degassing,shallow lateral migration,accumulation in traps far from faults,partial pressure balance and sealing capability.
基金funded by the National Key R&D Program(2017YFC060302)the National Natural Science Foundation of China(41872155,41872164 and 42172168)。
文摘Heat carried by deep fluid might greatly affect hydrocarbon generation and pore space in shale.Dyke intrusion carrying high levels of heat may be a means by which to explore the influence of deep fluid on shale reservoirs.This study evaluates hydrocarbon generation and analyzed the evolution of shale storage space in the third member of the Xiamaling Formation in the Zhaojiashan section,Hebei Province,based on experimental data such as TOC,SEM,VRo,low-temperature N_(2)adsorption and high-pressure mercury injection.The results show that the dyke intrusion reduced the shale TOC content drastically―by up to 77%―and also induced instantaneous hydrocarbon generation over a range about 1.4 times the thickness of the intrusion.Furthermore,the dyke intrusion might transform organic pores in surrounding shales into inorganic pores.There were two shale porosity peaks:one appeared when VRo=2.0%,caused by the increase of organic pores as thermal maturity increased,the other occurred when the VRo value was between 3%and 4%,caused by the increase of inorganic mineral pores.It can be concluded that dyke intrusion can be an effective tool with which to study how deep fluid affects instantaneous hydrocarbon generation and pore space in shale.
基金funded by the National Natural Science Foundation of China (Grant Nos.:41102075 and 41230312)the Open Fund of Key Laboratory of Tectonics and Petroleum Resources (China University of Geosciences), Ministry of Education (Grant No.: TPR-2012-24)
文摘Hydrogen gas accelerates hydrocarbon generation, but little is known about its distribution and origin in petroliferous basins, which has hindered the further exploration.Taken the Jiyang Depression in eastern China as an example, this study collected natural gas from different tectonic units, and analyzed various geochemical characters including gas contents, and carbon and hydrogen isotopic composition.The result shows that：（1） hydrogen gas is widespread distributed, but its content is very low, which typically ranges from 0.01% to 0.1% in this region;（2） the ratios of H2/3He, indicative of the origins of hydrogen gas, suggest that mantle-derived hydrogen is dominant.Even in tectonically stable areas absent with deep fluid activities, there is also mantle-derived;（3） the isotopic composition of hydrogen falls in the range of –798‰ to –628‰（relative to VSMOW standard）.In areas with deep-derived fluids, the hydrogen gas has a similar isotopic composition with the previously documented deep-sourced gas, with lighter isotopic composition.In contrast, hydrogen gas has a heavier isotopic composition in relatively stable areas.The isotopic signatures suggest that there is a mixture of mantle- and crust-derived hydrogen gas in the relatively stable area, which is consistent with the H2/3He ratios.Therefore, it is clear that the hydrogen gas has a much wider distribution than found in the deep-derived fluid area, resulting in a much broader area with hydrogenating effect for resource rock.This understanding will provide new insights for hydrocarbon generation research and resource assessment in petroliferous basins.
基金jointly funded by the National Key Research and Development Project(2018YFC1503301)the National Natural Sciences Foundation of China(NSFC)(U1839211)the fundamental scientific research project of the Institute of Geology,China Earthquake Administration(IGCEA2123)。
文摘This study analyzed and summarized in detail the spatial and temporal distributions of earthquakes,tidal responses,focal mechanisms,and stress field characteristics for the M 7.3 Haicheng earthquake sequence in February 1975.The foreshocks are related to the main fault and the conjugate faults surrounding the extension step-over in the middle.The initiation timing of the foreshock clusters and the original time of the mainshock were clearly modulated by the Earth's tidal force and coincided with the peak of dilational volumetric tidal strain.As a plausible and testable hypothesis,we proposed a fluid-driven foreshock model,by which all observed seismicity features can be more reasonably interpreted with respect to the results of existing models.Together with some other known examples,the widely existing step-over along strike-slip faults and associated conjugate faults,especially for extensional ones in the presence of deep fluids,favor the occurrence of short-term foreshocks.Although clustered seismicity with characteristics similar to those of the studied case is not a sufficient and necessary condition for large earthquakes to occur under similar tectonic conditions,it undoubtedly has a warning significance for the criticality of the main fault.Subsequent testing would require quantification of true/false positives/negatives.
基金We thank editor board members for the encouragement and recom-mendation,and thank the two anonymous reviewers for the detailed constructive comments.Jinrong Su acknowledge the support of China National Key R&D Project(2018YFC1504501-02).
文摘On February 3rd,2020,an isolated MS5.1 earthquake occurred in the northern section of the Longquanshan fault zone.This study aims at defining the geometry of seismogenic structures of this earthquake.In detail,centroid moment tensor inversion results show that the earthquake is characterized by a focal depth of 3.8 km with no corresponding surface faults.The strike/dip/rake angles for the two nodal planes are 205°/54°/96°and 15°/36°/82°,respectively.With the analyses of coseismic deformation of the surface obtained from InSAR measurements,together with the information of relocated hypocenters for a small number of aftershocks,it is concluded that a northwest-dipping nodal plane corresponds well to the source fault.The fault is suggested to have a length of about 2.8 km and a depth range of 2-5 km,and the centroid of the earthquake is located at 104.48°E and 30.71°N.Furthermore,multiple pieces of evidence indicate that this earthquake is partly driven by the overpressure effect associated with the adjacent natural gas packets,which is similar to several other moderate natural earthquakes in Sichuan Basin.
文摘Using hypocenter relocation,moment tensor inversion,stress field inversion,and fault slip tendency analysis,this study systematically investigated three M5.5-5.8 earthquake sequences that occurred after 2000 in the Yongning-Luguhu faulted basin in the middle of the Lijiang-Xiaojinhe fault zone within the Sichuan-Yunnan block,Southwest China.Our results show that since the 2008 Wenchuan earthquake,the tectonic stress pattern in this area may have changed and that b-values estimated for the earthquake sequences show evidence of an increasing trend in stress in the study area.Seismicity in the small-scale faulted basin adjacent to the large-scale fault zone is a possible indicator of regional stress.We also note that the aftershocks of the M5.7 earthquake sequence in 2012 and the M5.5 earthquake sequence in 2022 show relatively clear fluid diffusion-triggering characteristics.Overpressure of deep fluids is still the main factor driving seismic activity in the region,and we propose that the background tectonic stresses have not yet reached critical levels.
基金financially supported by the National Natural Science Foundation of China (No. 41120124003, 41572335 and 41521001)the research program of China Power Investment Corporation (2015-138-HHS-KJ-X)the research program of State Key Laboratory of Biogeology and Environmental Geology of China
文摘Longling is characterized by a wide distribution of hydrothermal areas, among which the Banglazhang hydrothermal system is the most geothermally active. Banglazhang is marked by intensive hydrothermal activities including hot springs, geysers, fumaroles and hydrothermal explosions. The geothermal waters from the Longling region are mainly HCO3-Na type with low but comparable SO4 and Cl concentrations. Calculations based on a variety of chemical geothermometers and a K-Ca geobarometer indicate that the Banglazhang hydrothermal system has much higher subsurface temperature and CO2 pressure compared to the other systems such as Daheba, Dazhulin and Huangcaoba. However, geothermal water samples collected from all these alternative hydrothermal areas are either partially equilibrated with reservoir minerals or are immature. The silica-enthalpy relationships of Banglazhang geothermal waters indicate the presence of a deep geothermal fluid with an enthalpy value and silica concentration of 945 J/g（up to around 220 °C） and 339 mg/L. Our work indicates the Banglazhang area is a promising source in terms of long-term utilization of hydrothermal resources.
基金supported by the National Natural Science Foundation of China(Grant Nos.41625009,41872122 and 41902160)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA14010404)+1 种基金the National Key Foundational Research and Development Project(Grant No.2017YFC0603102)the China Postdoctoral Science Foundation(Grant No.2019M650967).
文摘Based on the analysis of the natural gas samples of 146 wells from four major petroliferous basins of China,the source and distribution of mercury in natural gas in major petroliferous basins of China were identified.Studies have shown that the mercury concentration of natural gas in petroliferous basins of China varies widely,ranging from 0.01 to 4050μg/m^3.The gas well with the highest mercury concentration is in the Xushen gas field in the Songliao Basin.The mercury concentration in the craton basin is relatively low,and the secondary gas reservoir in the Tarim Basin has the lowest mercury concentration.In the rift basin,due to the presence of deep faults which cut the basement and mixing effects of deep fluids,the mercury concentration in natural gas may be abnormally high,e.g.the Xushen gas field in the Songliao Basin.In relatively stable basins where deep and large faults do not develop,mercury is primarily of organic origin.In rift basins where deep fluids are mixed with gas reservoirs,mercury in natural gas may mainly come from the deep fluids and is characterized by abnormally high mercury concentration and R/Ra values.
基金funded by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)grant from the Ministry of Trade,Industry and Energy(MOTIE)(No.20198210100030,20208310100020)the Nuclear Safety Research Program through the Korea Foundation of Nuclear Safety(KoFONS)grant from the Nuclear Safety and Security Commission(NSSC)(No.071610)of the Republic of Korea.
文摘Five sequences of deep fluid injections at the Pohang Enhanced Geothermal System(EGS)triggered an ML 5.4 earthquake on November 15,2017.The foreshock-mainshock-aftershock sequence was monitored using dense seismic networks.Between November 14,2017,and May 31,2023,this study detected 5,169 earthquakes and determined the relative locations of 4,902 earthquakes,including seven foreshocks.A heterogeneous subsurface fault model is proposed,in which the fault is reactivated by induced and triggered earthquakes.The earthquake frequency decreased after the mainshock,with a temporary increase after the ML 4.6 event on February 10,2018.The magnitude-frequency b-values are significantly lower than those for the background seismicity in the Korean Peninsula and those for the 2016 Gyeongju earthquake sequence.The aftershock decay rate p-values are within the range of typical values,regardless of decreasing over time.The earthquake focal mechanisms exhibit a predominance of strike-slip components,whereas the slip tendency indicates a higher value in reverse faulting geometry,implying stress redistribution after the mainshock.The seismic landscape with ongoing aftershock activity after the 2017 Pohang earthquake underscores the importance of sustained,long-term seismic monitoring to comprehensively grasp the implications of the new seismic environment for seismic hazards in the area.
