Clays have considerable influence on the electrical properties of hydrate-bearing sediments.It is desirable to understand the electrical properties of hydrate-bearing clayey sediments and to build hydrate saturation(S...Clays have considerable influence on the electrical properties of hydrate-bearing sediments.It is desirable to understand the electrical properties of hydrate-bearing clayey sediments and to build hydrate saturation(S_(h))models for reservoir evaluation and monitoring.The electrical properties of tetrahydrofuran-hydrate-bearing sediments with montmorillonite are characterized by complex conductivity at frequencies from 0.01 Hz to 1 kHz.The effects of clay and Sh on the complex conductivity were analyzed.A decrease and increase in electrical conductance result from the clay-swelling-induced blockage and ion migration in the electrical double layer(EDL),respectively.The quadrature conductivity increases with the clay content up to 10%because of the increased surface site density of counterions in EDL.Both the in-phase conductivity and quadrature conductivity decrease consistently with increasing Sh from 0.50 to 0.90.Three sets of models for Sh evaluation were developed.The model based on the Simandoux equation outperforms Archie’s formula,with a root-mean-square error(E_(RMS))of 1.8%and 3.9%,respectively,highlighting the clay effects on the in-phase conductivity.The fre-quency effect correlations based on in-phase and quadrature conductivities exhibit inferior performance(E_(RMS)=11.6%and 13.2%,re-spectively)due to the challenge of choosing an appropriate pair of frequencies and intrinsic uncertainties from two measurements.The second-order Cole-Cole formula can be used to fit the complex-conductivity spectra.One pair of inverted Cole-Cole parameters,i.e.,characteristic time and chargeability,is employed to predict S_(h) with an E_(RMS) of 5.05%and 9.05%,respectively.展开更多
The safe and efficient development of natural gas hydrate requires a deep understanding of the deformation behaviors of reservoirs.In this study,a series of triaxial shearing tests are carried out to investigate the d...The safe and efficient development of natural gas hydrate requires a deep understanding of the deformation behaviors of reservoirs.In this study,a series of triaxial shearing tests are carried out to investigate the deformation properties of hydrate-bearing sediments.Variations of volumetric and lateral strains versus hydrate saturation are analyzed comprehensively.Results indicate that the sediments with high hydrate saturation show dilative behaviors,which lead to strain-softening characteristics during shearing.The volumetric strain curves have a tendency to transform gradually from dilatation to compression with the increase in effective confining pressure.An easy prediction model is proposed to describe the relationship between volumetric and axial strains.The model coefficientβis the key dominating factor for the shape of volumetric strain curves and can be determined by the hydrate saturation and stress state.Moreover,a modified model is established for the calculation of lateral strain.The corresponding determination method is provided for the easy estimation of model coefficients for medium sand sediments containing hydrate.This study provides a theoretical and experimental reference for deformation estimation in natural gas hydrate development.展开更多
Scallop culture is an important way of bottom-seeding marine ranching,which is of great significance to improve the current situation of fishery resources.However,there are some problems in site-selection evaluation o...Scallop culture is an important way of bottom-seeding marine ranching,which is of great significance to improve the current situation of fishery resources.However,there are some problems in site-selection evaluation of marine ranching,such as imperfect criteria system,complex structure,untargeted criteria quantification,etc.In addition,no site-selection evaluation method of bottom-seeding culture areas for scallops is available.Therefore,we established a hierarchy structure model according to the analytic hierarchy process(AHP)theory,in which social,physical,chemical,and biological environments are used as main criteria,and marine functional zonation,water depth,current,water temperature,salinity,substrate type,water quality,sediment quality,red tide,phytoplankton,and zooplankton are used as sub-criteria,on which a multi-parameter evaluation system is set up.Meanwhile,the dualism method,assignment method,and membership function method were used to quantify sub-criteria,and a quantitative evaluation for the entire criteria was added,including the evaluation and analysis of two types of unsuitable environmental situations.By overall consideration in scallop yield,quality,and marine ranching construction objectives,the weight of the main criteria could be determined.Five grades in the suitability corresponding to the evaluation result were divided,and the Python language was used to create an evaluation system for efficient calculation and intuitive presentation of the evaluation outcome.Eight marine cases were simulated based on existing survey data,and the results prove that the method is feasible for evaluating and analyzing the site selection of bottom-seeding culture areas for scallops under various environmental situations.The proposed evaluation method can be promoted for the site selection of bottom-seeding marine ranching.This study provided theoretical and methodological references for the site selection evaluation of other types of marine ranching.展开更多
Objective A succession with well-developed soft-sediment deformation structures and well-exposed gravity-flow deposits in the Early Cretaceous Lingshandao Formation has caused considerable controversy on whether the n...Objective A succession with well-developed soft-sediment deformation structures and well-exposed gravity-flow deposits in the Early Cretaceous Lingshandao Formation has caused considerable controversy on whether the nondisputed deltaic environment was marine or continental.This dispute cannot be solved by mere sedimentological analysis and,moreover,too few fossils are present to be decisive.The main objective of the present contribution展开更多
When used with large energy sparkers, marine multichannel small-scale high-resolution seismic detection technology has a high resolution, high-detection precision, a wide applicable range, and is very flexible. Positi...When used with large energy sparkers, marine multichannel small-scale high-resolution seismic detection technology has a high resolution, high-detection precision, a wide applicable range, and is very flexible. Positive results have been achieved in submarine geological research, particularly in the investigation of marine gas hydrates. However, the amount of traveltime difference information is reduced for the velocity analysis under conditions of a shorter spread length, thus leading to poorer focusing of the velocity spectrum energy group and a lower accuracy of the velocity analysis. It is thus currently debatable whether the velocity analysis accuracy of short-arrangement multichannel seismic detection technology is able to meet the requirements of practical application in natural gas hydrate exploration. Therefore, in this study the bottom boundary of gas hydrates(Bottom Simulating Reflector, BSR) is used to conduct numerical simulation to discuss the accuracy of the velocity analysis related to such technology. Results show that a higher dominant frequency and smaller sampling interval are not only able to improve the seismic resolution, but they also compensate for the defects of the short-arrangement, thereby improving the accuracy of the velocity analysis. In conclusion, the accuracy of the velocity analysis in this small-scale, high-resolution, multi-channel seismic detection technology meets the requirements of natural gas hydrate exploration.展开更多
Grain-displacing hydrate deposits exist at many marine sites,which constitute an important part of methane hydrate resources worldwide.Attributed to the difficulties in acquiring field data and synthesizing experiment...Grain-displacing hydrate deposits exist at many marine sites,which constitute an important part of methane hydrate resources worldwide.Attributed to the difficulties in acquiring field data and synthesizing experimental samples,the formation and property characterization of grain-displacing hydrate remains less understood and characterized than the pore-filling hydrate in current literature.This study reviews the formation mechanisms of grain-displacing hydrate from the perspective of geological accumulation and microscale sedimentary property.The experimental methods of synthesizing grain-displacing hydrate in the laboratory and the current knowledge on the property of grain-displacing hydrate sediment are also introduced.Shortcomings in current theories and suggestions for future study are proposed.The work is hoped to provide valuable insights for the research into the hydrate accumulation,geophysics,and hydrate exploitation targeted at the grain-displacing hydrate in the marine sediments.展开更多
1.Objectives As about 99% of the natural gas hydrate (NGH)resources are stored on the seafloor,it is inevitable that in its process of exploration and production,there will be geohazards such as methane leakage,seabed...1.Objectives As about 99% of the natural gas hydrate (NGH)resources are stored on the seafloor,it is inevitable that in its process of exploration and production,there will be geohazards such as methane leakage,seabed subsidence,ecosystem damage and even landslide.Therefore,a set of integrated systems for environmental monitoring in the process of NGH production has been proposed in the consideration of environmental disasters that may arise in the process of hydrate production.展开更多
Notable differences in the structural characteristics and evolution of three adjacent sub-sags,i.e.,the Wenchang sub-sags A,B,and C,on the downthrown side of the Zhu IlI South Fault in the Wenchang Sag,are significant...Notable differences in the structural characteristics and evolution of three adjacent sub-sags,i.e.,the Wenchang sub-sags A,B,and C,on the downthrown side of the Zhu IlI South Fault in the Wenchang Sag,are significant as they affect the formation and distribution of the oil and gas in these three sub-sags.However,the differences in their tectonic evolutions and formation mechanisms have not yet been adequately explained.In this paper,stress analysis,equilibrium profiles,and paleogeomorphic restora-tion,are used to investigate the dynamic settings,formation mechanisms,and influencing factors of the structural deformation related to the formation of the Wenchang Sag based on interpretation of seismic data.The results of the stress analysis suggest clockwise deflection of the regional tensile stress direction from a WNW-ESE trend during the Early Paleocene to NW-SE and NNW-SSE trends during the Eocene,to a nearly N-S trend during the Oligocene,and finally to a NNE-SSW trend during the Miocene.This clockwise rotation of the regional tensile stress direction led to the formation of a dextral strike-slip stress component parallel to the NE-trending Zhu I South Fault.This strike-slip stress component formed a releasing bend in sub-sag A,and may be associated with the continuous subsidence of a thick sedimentary layer in sub-sag A.It also created a restraining bend in sub-sag B,which underwent multiple structural inversions during its extension and subsidence and has a relatively s mall sedimentary thick-ness.The double restraining bend in sub-sag C is considered to have been strongly uplifted and eroded in response to this strike-slip stress component.Four obvious structural inversions in sub-sag B are iden-tified in this paper.These structural inversions correspond to the last four regional tectonic movements.This interpretation suggests that the formation of the structural inversions was likely related to the strong tensile stress and the small intersection angle between the direction of the regional tensile stress and the pre-existing boundary fault.The rotation of the tensile stress direction was responsible for the strike-slip movement on the pre-existing boundary fault and the formation of the releasing bend and restraining bend,which controlled the structural evolutions of the sub-sags.This reasonably explains the differential tectonic evolution of these three sub-sags in the Wenchang Sag,and provides a crucial idea forstructuralanalysisof similarbasins.展开更多
Core samples from the deeply buried Ordovician Majiagou Formation below the Huainan Coalfield(E China) have been investigated for their carbonate types,major and trace elements(including rare earth elements) and C and...Core samples from the deeply buried Ordovician Majiagou Formation below the Huainan Coalfield(E China) have been investigated for their carbonate types,major and trace elements(including rare earth elements) and C and O isotopes,The objective was to get a better insight into the possible occurrences of gas(and possibly oil) derived from Carboniferous coals.It was found that the carbonates are dolomites with strongly varying amounts of CaO and MgO.The low concentrations of SiO_(2),Al_(2)O_(3),and Fe_(2)O_(3)indicate deposition in a normal marine environment with little terrigenous input,The Na_(2)O/K_(2)O,Fe/Mn and Sr/Ba ratios,as well as the Ga values indicate mainly a marine salinity and a hot and humid climate.The slight depletion of Ce and Eu,the depletion of heavy rare earth elements(HREE) and the enrichment of light rare earth elements(LREE) indicate deposition in a reducing environment.It thus appears that the Majiagou Formation below the Huainan Coalfield closely resembles that in the eastern part of the Ordos Basin,where several gas reservoirs are present,so that the Majiagou Formation under the Huainan Coalfield represents a promising target for hydrocarbon exploration.展开更多
Organic-inorganic interactions between hydrocarbons and most minerals in deeply buried reservoirs remain unclear.In this study,gold capsules and fused silica capillary capsules(FSCCs)with different com-binations of nC...Organic-inorganic interactions between hydrocarbons and most minerals in deeply buried reservoirs remain unclear.In this study,gold capsules and fused silica capillary capsules(FSCCs)with different com-binations of nC_(16)H_(34),water(distilled water,CaCl_(2) water)and minerals(quartz,feldspar,calcite,kaolinite,smectite,and illite)were heated at 340℃ for 3-10 d,to investigate the evolution and reaction pathways of the organic-inorganic interactions in different hot systems.After heating,minerals exhibited little alteration in the anhydrous systems.Mineral alterations,how-ever,occurred obviously in the hydrous systems.Different inorganic components affected nC_(16)H_(34) degra-dation differently.Overall,water promoted the free-radical thermal-cracking reaction and step oxidation reaction but suppressed the free-radical cross-linking reaction.The impact of CaCl_(2) water on the nC_(16)H_(34) degradation was weaker than the distilled water as high Ca^(2+)concentration suppressed the formation of free radicals.The presence of different waters also affects the impact of different minerals on nC_(16)H_(34) degradation,via its impact on mineral alterations.In the anhydrous nC_(16)H_(34)-mineral systems,calcite and clays catalyzed generation of low-molecular-weight(LMW)alkanes,particularly the clays.Quartz,feldspar,and calcite catalyzed generation of high-molecular-weight(HMW)alkanes and PAHs,whereas clays catalyzed the generation of LMW alkanes and mono-bicyclic aromatic hydrocarbons(M-BAHs).In the hydrous nC_(16)H_(34)-distilled water-mineral systems,all minerals but quartz promoted nC_(16)H_(34) degra-dation to generate more LMW alkanes,less HMW alkanes and PAHs.In the nC_(16)H_(34)-CaCl_(2) water-mineral systems,the promotion impact of minerals was weaker than that in the systems with distilled water.This study demonstrated the generation of different hydrocarbons with different fluorescence colors in the different nC_(16)H_(34)-water-mineral systems after heating for the same time,implying that fluorescence colors need to be interpreted carefully in investigation of hydrocarbon charging histories and oil origins in deeply buried reservoirs.Besides,the organic-inorganic interactions in different nC_(16)H_(34)-water-mineral systems proceeded in different pathways at different rates,which likely led to preservation of liquid hydrocarbons at different depth(temperature).Thus,quantitative investigations of the reaction kinetics in different hydrocarbon-water-rock systems are required to improve the prediction of hydrocar-bon evolution in deeply buried hydrocarbon reservoirs.展开更多
Laboratory visual detection on the hydrate accumulation process provides an effective and low-cost method to uncover hydrate accumulation mechanisms in nature.However,the spatial hydrate distribution and its dynamic e...Laboratory visual detection on the hydrate accumulation process provides an effective and low-cost method to uncover hydrate accumulation mechanisms in nature.However,the spatial hydrate distribution and its dynamic evolutionary behaviors are still not fully understood due to the lack of methods and experimental systems.Toward this goal,we built a two-dimensional electrical resistivity tomography(ERT)apparatus capable of measuring spatial and temporal characteristics of hydrate-bearing porous media.Beach sand(0.05–0.85 mm)was used to form artificial methane hydrate-bearing sediment.The experiments were conducted at 1°C under excess water conditions and the ERT data were acquired and analyzed.This study demonstrates the utility of the ERT method for hydrate mapping in laboratory-scale.The results indicate that the average electrical conductivity decreases nonlinearly with the formation of the hydrate.At some special time-intervals,the average conductivity fluctuates within a certain scope.The plane conductivity fields evolve heterogeneously and the local preferential hydrate-forming positions alternate throughout the experimental duration.We speculate that the combination of hydrate formation itself and salt-removal effect plays a dominant role in the spatial and temporal hydrate distribution,as well as geophysical parameters changing behaviors during hydrate accumulation.展开更多
To investigate the nature of gas hydrates in the Makran area,new high-resolution geophysical data were acquired between 2018-2019.The data collected comprise multibeam and two-dimensional multi-channel seismic reflect...To investigate the nature of gas hydrates in the Makran area,new high-resolution geophysical data were acquired between 2018-2019.The data collected comprise multibeam and two-dimensional multi-channel seismic reflection data.The multibeam bathymetry data show East-North-East(ENE)ridges,piggy-back basins,canyon and channel systems,and the morphology of the abyssal plain.Continuous and discontinuous bottom simulating reflectors(BSRs)occur in the piggy-back basins on most of the seismic profiles available.The BSRs cut the dipping layers with strong amplitude and reversed polarity.Discontinuous BSRs indicate a transition along a dipping high-permeable sand layers from gas-rich segment to the gas hydrate-bearing segment and sugge st alternating sediments of fine and relatively coarse grain size.Double BSRs are highly dynamic and attributed to slumps occurring in the study area.The BSRs induced by slumps are located both at deep and shallow depths,responding to the temperature or pressure variation.For the first time,BSRs are observed in the abyssal plain of the Makran area,being associated with anticline structures,which do not show large spatial continuity and are strongly conditioned by structural conditions such as anticlines and fluid migration pathways,including deep fault,gas chimney,and high-permeable sedimentary layer.Our results may help to assess the gas hydrate potential within the piggy-back basins and to determine the most promising target areas.Moreover,results about the abyssal plain BSR may help to locate hydrocarbon reservoirs in the deep ocean.展开更多
Fractured hydrate-bearing reservoirs show significantly anisotropic geophysical properties. The joint application of seismic and electromagnetic explorations is expected to accurately assess hydrate resources in the f...Fractured hydrate-bearing reservoirs show significantly anisotropic geophysical properties. The joint application of seismic and electromagnetic explorations is expected to accurately assess hydrate resources in the fractured reservoirs. However, the anisotropic joint elastic-electrical properties in such reservoirs that are the key to the successful application of the joint explorations, remain poorly understood. To obtain such knowledge, we designed and implemented dedicated laboratory experiments to study the anisotropic joint elastic-electrical properties in fractured artificial silica sandstones (with fracture density of about 6.2%, porosity of approximately 25.7%, and mean grainsize of 0.089 mm) with evolving methane hydrate. The experimental results showed that the anisotropic compressional wave velocities respectively increased and decreased with the forming and dissociating hydrate, and the variation in the increasing trend and the decreasing extent of the velocity perpendicular to the fractures were more significant than that parallel to the fractures, respectively. The experimental results also showed that the overall decreasing trend of the electrical conductivity parallel to the fractures was steeper than that perpendicular to the fractures during hydrate formation, and the general variations of the two conductivities with complex trend were similar during hydrate dissociation. The variations in the elastic and electrical anisotropic parameters with forming and dissociating hydrate were also found to be distinct. Interpretation of the experimental results suggested that the hydrate binding to the grains evolved to bridge the surfaces of fractures when saturation exceeded 10% during hydrate formation, and the bridging hydrate gradually evolved to floating in fractures during dissociation. The experimental results further showed that the anisotropic velocities and electrical conductivities were correlated with approximately consistent trends of different slopes during hydrate formation, and the joint elastic-electrical anisotropic parameters exhibited a sharp peak at the hydrate saturation of about 10%. The results suggested that the anisotropic joint properties can be employed not only to accurately estimate hydrate saturation but also possibly to identify hydrate distribution in the fractures.展开更多
Sand production is one of the main obstacles restricting gas extraction efficiency and safety from marine natural gas hydrate(NGH)reservoirs.Particle migration within the NGH reservoir dominates sand production behavi...Sand production is one of the main obstacles restricting gas extraction efficiency and safety from marine natural gas hydrate(NGH)reservoirs.Particle migration within the NGH reservoir dominates sand production behaviors,while their relationships were rarely reported,severely constrains quantitative evaluation of sand production risks.This paper reports the optical observations of solid particle migration and production from micrometer to mesoscopic scales conditioned to gravel packing during depressurization-induced NGH dissociation for the first time.Theoretical evolutionary modes of sand migration are established based on experimental observations,and its implications on field NGH are comprehensively discussed.Five particle migration regimes of local borehole failure,continuous collapse,wormhole expansion,extensive slow deformation,and pore-wall fluidization are proved to occur during depressurization.The types of particle migration regimes and their transmission modes during depressurization are predominantly determined by initial hydrate saturation.In contrast,the depressurization mainly dominates the transmission rate of the particle migration regimes.Furthermore,both the cumulative mass and the medium grain size of the produced sand decrease linearly with increasing initial methane hydrate(MH)saturation.Discontinuous gas bubble emission,expansion,and explosion during MH dissociation delay sand migration into the wellbore.At the same time,continuous water flow is a requirement for sand production during hydrate dissociation by depressurization.The experiments enlighten us that a constitutive model that can illustrate visible particle migration regimes and their transmission modes is urgently needed to bridge numerical simulation and field applications.Optimizing wellbore layout positions or special reservoir treatment shall be important for mitigating sand production tendency during NGH exploitation.展开更多
Submarine seep plumes are a natural phenomenon in which different types of gases migrate through deep or shallow subsurface sediments and leak into seawater in pressure gradient.When detected using acoustic data,the l...Submarine seep plumes are a natural phenomenon in which different types of gases migrate through deep or shallow subsurface sediments and leak into seawater in pressure gradient.When detected using acoustic data,the leaked gases frequently exhibit a flame-like structure.We numerically modelled the relationship between the seismic response characteristic and bubble volume fraction to establish the bubble volume fraction in the submarine seep plume.Results show that our models are able to invert and predict the bubble volume fraction from field seismic oceanography data,by which synthetic seismic sections in different dominant frequencies could be numerically simulated,seismic attribute sections(e.g.,instantaneous amplitude,instantaneous frequency,and instantaneous phase)extracted,and the correlation between the seismic attributes and bubble volume fraction be quantitatively determined with functional equations.The instantaneous amplitude is positively correlated with bubble volume fraction,while the instantaneous frequency and bubble volume fraction are negatively correlated.In addition,information entropy is introduced as a proxy to quantify the relationship between the instantaneous phase and bubble volume fraction.As the bubble volume fraction increases,the information entropy of the instantaneous phase increases rapidly at the beginning,followed by a slight upward trend,and finally stabilizes.Therefore,under optimal noise conditions,the bubble volume fraction of submarine seep plumes can be inverted and predicted based on seismic response characteristics in terms of seismic attributes.展开更多
The element geochemical characteristics and diagenetic alteration products of tuffaceous components in sandstone reservoirs of Paleogene Wenchang Formation in typical subsags of the Huizhou-Lufeng area of the Zhu I De...The element geochemical characteristics and diagenetic alteration products of tuffaceous components in sandstone reservoirs of Paleogene Wenchang Formation in typical subsags of the Huizhou-Lufeng area of the Zhu I Depression,Pearl River Mouth Basin,were identified through microscopic analysis and quantitative analysis of main and trace elements.The impacts of dissolution of different tuffaceous components on physical properties of reservoirs were discussed through quantitative characterization of reservoir physical properties.The results show that there are mainly four types of tuffaceous components in the study area,which are acidic,intermediate,basic and alkaline tuffaceous components.The acidic tuffaceous components evolved in a process of strong alteration and weak dissolution of alteration products,with a large amount of kaolinite precipitated during alteration to disenable the improvement of porosity and permeability.The intermediate and alkaline tuffaceous components evolved in a process of strong dissolution of tuffaceous components and strong alteration of residual tuffaceous components;the dissolution of tuffaceous components created intergranular pores,but the alteration products such as autogenic quartz,apatite and illite deteriorated the pore structure;ultimately,the dissolution of tuffaceous components resulted in the increase of porosity but no increase of permeability of the reservoir.The basic tuffaceous components dominantly evolved in a process of dissolution of tuffaceous components to strong dissolution of alteration products;both tuffaceous components between particles and laumontite generated from alteration can be strongly dissolved to create pores;thus,the dissolution of tuffaceous components can significantly increase the physical properties of the reservoir.展开更多
The composition,provenance,and genetic mechanism of sediment on different sedimentary units of the East China Sea(ECS)shelf are essential for understanding the depositional dynamics environment in the ECS.The sediment...The composition,provenance,and genetic mechanism of sediment on different sedimentary units of the East China Sea(ECS)shelf are essential for understanding the depositional dynamics environment in the ECS.The sediments in the northern ECS shelf are distributed in a ring-shaped distribution centered on the southwestern Cheju Island Mud.From the inside to the outside,the grain size goes from fine to coarse.Aside from the“grain size effect”,hydrodynamic sorting and mineral composition are important restrictions on the content of rare earth elements(REEs).Based on the grain size,REEs,and clay mineral composition of 300 surface sediments,as well as the sedimentary genesis,the northern ECS shelf is divided into three geochemical zones:southwestern Cheju Island Mud Area(ZoneⅠ),Changjiang Shoal Sand Ridges(ZoneⅡ-1),Sand Ridges of the East China Sea shelf(ZoneⅡ-2).The northern ECS shelf is mostly impacted by Chinese mainland rivers(the Changjiang River and Huanghe River),and the provenance and transport mechanism of sediments of different grain sizes is diverse.The bulk sediments come primarily from the Changjiang River,with some material from the Huanghe River carried by the Yellow Sea Coastal Current and the North Jiangsu Coastal Current,and less from Korean rivers.Among them,surface sediments in the southwestern Cheju Island Mud Area(ZoneⅠ)come mostly from the Changjiang River and partly from the Huanghe River.It was formed by the counterclockwise rotating cold eddies in the northern ECS shelf,which caused the sedimentation and accumulation of the fine-grained sediments of the Changjiang River and the Huanghe River.The Changjiang Shoal Sand Ridges(ZoneⅡ-1)were developed during the early-middle Holocene sea-level highstand.It is the modern tidal sand ridge sediment formed by intense hydrodynamic action under the influence of the Yellow Sea Coastal Current,North Jiangsu Coastal Current,and Changjiang Diluted Water.The surface sediments mainly originate from the Changjiang River and Huanghe River,with the Changjiang River dominating,and the Korean River(Hanjiang River)influencing just a few stations.Sand Ridges of the East China Sea shelf(ZoneⅡ-2)are the relict sediments of the paleo-Changjiang River created by sea invasion at the end of the Last Deglaciation in the Epipleistocene.The clay mineral composition of the surface sediments in the study area is just dominated by the Changjiang River,with the North Jiangsu Coastal Current and the Changjiang Diluted Water as the main transporting currents.展开更多
There is a vast upwelling area induced by the southeast monsoon in the waters off South Java,making the region an important fishing ground.Climate events can affect the variation of upwelling,but oceanographers have d...There is a vast upwelling area induced by the southeast monsoon in the waters off South Java,making the region an important fishing ground.Climate events can affect the variation of upwelling,but oceanographers have different understandings on the extent to which climate events control upwelling in this area,which leads to a lack of basis for studies on the evaluation and mechanisms of the variability of fishery resources in the region.The correlation between environmental parameters,including surface temperature(SST),chlorophyll-a(Chl-a)concentration,and climate event indices in South Java from 2003 to 2020 was analyzed.Results show that the Indian Ocean Dipole(IOD)has a greater influence on the interannual variability of upwelling intensity than ENSO.During the IOD,variations in equatorial latitudinal winds excite different types of Kelvin waves that anomalously deepen or shallow the thermocline,which is the main cause of anomalous variations in upwelling,independent of variations in the local wind field.A correlation between the interannual variability in upwelling and the annual catches was revealed,showing that climatic events indirectly affect fishery resources through upwelling effects.During positive IOD/El Niño periods,strong upwelling delivers more nutrients to the surface layer,which favors fish growth and reproduction,resulting in higher annual catches.A negative IOD/La Niña,on the other hand,leads to weaker upwelling and fewer nutrients into the surface waters.Fish tend to move in deeper waters,making traditional fishing methods less efficient and consequently lower annual catches.展开更多
Submarine canyon-channel systems have been documented in the Parece Vela Basin,West Mariana Ridge;however,the mechanism of the formation and controlling factors remain poorly understood.Based on high-resolution multib...Submarine canyon-channel systems have been documented in the Parece Vela Basin,West Mariana Ridge;however,the mechanism of the formation and controlling factors remain poorly understood.Based on high-resolution multibeam bathymetric data and two-dimensional(2D)seismic profiles,we identified and mapped the submarine canyon-channel system along the middle segment of West Mariana Ridge in the Philippine Sea.These submarine canyon-channels show a main W-E orientation at depth of 2000–4500 m.They are approximately 72–128 km in length and 1.3–15 km in width,and their canyon heads are adjacent to the seamounts with several branches.The upper reaches of submarine canyon-channels are characterized by deeply incised,narrow,V-shaped thalwegs,suggesting the powerful erosion of gravity flows.The distinguished sediment waves are suggested to be resulted from the interaction of turbidity currents and seafloor.Our observations demonstrate that gravity flows originated from the collapses of seamount flanks plays a vital role in developing the submarine canyonchannel system along the West Mariana Ridge.This work provides better understanding of erosion,transport,and deposition of sediments from subducting ridges to deep-water basins,and also new insights into the origin and evolution of submarine canyon-channel systems along subducting ridges.展开更多
Based on the petrology,isotope geochemistry and fluid inclusions analysis,we established the evolutionary mode of the diagenetic fluid of dawsonite-bearing sandstone in the Jiyang Depression.Dawsonite-bearing sandston...Based on the petrology,isotope geochemistry and fluid inclusions analysis,we established the evolutionary mode of the diagenetic fluid of dawsonite-bearing sandstone in the Jiyang Depression.Dawsonite-bearing sandstone is characterized by double injection of CO_(2)and oil-gas in the Jiyang Depression that have experienced a relatively complex diagenetic fluid evolution process.The diagenetic sequence of secondary minerals involves secondary enlargement of quartz,kaolinite,first-stage calcite,dawsonite,second-stage calcite,ferrocalcite,dolomite and ankerite.Hydrocarbon charging in the dawsonite-bearing sandstone occurred at around 2.6–0 Myr.The CO_(2)charging event occurred during Dongying tectonism,forming the Pingfangwang CO_(2)gas reservoir,which provided an abundant carbon source for dawsonite precipitation.Carbon and oxygen isotopic compositions of dawsonite demonstrate that CO_(2)forming the dawsonite was of an inorganic origin derived from the mantle,and that water mediating the proc-ess during dawsonite precipitation was sequestered brine with a fluid temperature of 82℃.The evolutionary sequence of the diagenetic fluid in the dawsonite-bearing sandstone was:alkaline syngenetic fluids,weak alkaline fluids during organic acid forma-tion,acidic fluids in the early stage of CO_(2)injection,alkaline fluids in the late stage of CO_(2)injection,and weak alkaline fluids during oil and gas charging.The mode indicates an increase in-HCO_(3)because of the CO_(2)injection,and the loss of Ca^(2+)and Mg^(2+)due to the precipitation of carbonate minerals.Therefore,the evolutionary mode of diagenetic fluids is in good agreement with high HCO_(3)^(-),low Ca^(2+)and low Mg^(2+)composition of the present formation water in the dawsonite-bearing sandstone.展开更多
基金supported by the Fundamental Research Funds for the Central Universities(No.20CX05005A)the Major Scientific and Technological Projects of CNPC(No.ZD2019-184-001)+2 种基金the PetroChina Innovation Foundation(No.2018D-5007-0214)the Shandong Provincial Natural Science Foundation(No.ZR2019MEE095)the National Natural Science Foundation of China(No.42174141).
文摘Clays have considerable influence on the electrical properties of hydrate-bearing sediments.It is desirable to understand the electrical properties of hydrate-bearing clayey sediments and to build hydrate saturation(S_(h))models for reservoir evaluation and monitoring.The electrical properties of tetrahydrofuran-hydrate-bearing sediments with montmorillonite are characterized by complex conductivity at frequencies from 0.01 Hz to 1 kHz.The effects of clay and Sh on the complex conductivity were analyzed.A decrease and increase in electrical conductance result from the clay-swelling-induced blockage and ion migration in the electrical double layer(EDL),respectively.The quadrature conductivity increases with the clay content up to 10%because of the increased surface site density of counterions in EDL.Both the in-phase conductivity and quadrature conductivity decrease consistently with increasing Sh from 0.50 to 0.90.Three sets of models for Sh evaluation were developed.The model based on the Simandoux equation outperforms Archie’s formula,with a root-mean-square error(E_(RMS))of 1.8%and 3.9%,respectively,highlighting the clay effects on the in-phase conductivity.The fre-quency effect correlations based on in-phase and quadrature conductivities exhibit inferior performance(E_(RMS)=11.6%and 13.2%,re-spectively)due to the challenge of choosing an appropriate pair of frequencies and intrinsic uncertainties from two measurements.The second-order Cole-Cole formula can be used to fit the complex-conductivity spectra.One pair of inverted Cole-Cole parameters,i.e.,characteristic time and chargeability,is employed to predict S_(h) with an E_(RMS) of 5.05%and 9.05%,respectively.
基金supported by the Qingdao Natural Science Foundation(No.23-2-1-54-zyyd-jch)the National Natural Science Foundation of China(Nos.42076217,41976074)+1 种基金the Laoshan Laboratory(No.LSKJ202203506)the Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education,Tongji University(No.KLE-TJGE-G2202).
文摘The safe and efficient development of natural gas hydrate requires a deep understanding of the deformation behaviors of reservoirs.In this study,a series of triaxial shearing tests are carried out to investigate the deformation properties of hydrate-bearing sediments.Variations of volumetric and lateral strains versus hydrate saturation are analyzed comprehensively.Results indicate that the sediments with high hydrate saturation show dilative behaviors,which lead to strain-softening characteristics during shearing.The volumetric strain curves have a tendency to transform gradually from dilatation to compression with the increase in effective confining pressure.An easy prediction model is proposed to describe the relationship between volumetric and axial strains.The model coefficientβis the key dominating factor for the shape of volumetric strain curves and can be determined by the hydrate saturation and stress state.Moreover,a modified model is established for the calculation of lateral strain.The corresponding determination method is provided for the easy estimation of model coefficients for medium sand sediments containing hydrate.This study provides a theoretical and experimental reference for deformation estimation in natural gas hydrate development.
基金Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB 42010203)the National Natural Science Foundation of China(No.42176090)。
文摘Scallop culture is an important way of bottom-seeding marine ranching,which is of great significance to improve the current situation of fishery resources.However,there are some problems in site-selection evaluation of marine ranching,such as imperfect criteria system,complex structure,untargeted criteria quantification,etc.In addition,no site-selection evaluation method of bottom-seeding culture areas for scallops is available.Therefore,we established a hierarchy structure model according to the analytic hierarchy process(AHP)theory,in which social,physical,chemical,and biological environments are used as main criteria,and marine functional zonation,water depth,current,water temperature,salinity,substrate type,water quality,sediment quality,red tide,phytoplankton,and zooplankton are used as sub-criteria,on which a multi-parameter evaluation system is set up.Meanwhile,the dualism method,assignment method,and membership function method were used to quantify sub-criteria,and a quantitative evaluation for the entire criteria was added,including the evaluation and analysis of two types of unsuitable environmental situations.By overall consideration in scallop yield,quality,and marine ranching construction objectives,the weight of the main criteria could be determined.Five grades in the suitability corresponding to the evaluation result were divided,and the Python language was used to create an evaluation system for efficient calculation and intuitive presentation of the evaluation outcome.Eight marine cases were simulated based on existing survey data,and the results prove that the method is feasible for evaluating and analyzing the site selection of bottom-seeding culture areas for scallops under various environmental situations.The proposed evaluation method can be promoted for the site selection of bottom-seeding marine ranching.This study provided theoretical and methodological references for the site selection evaluation of other types of marine ranching.
基金supported by the National Natural Science Foundation of China (grants No.41372135 and 41672120)Shandong University of Science and Technology Research Fund (grant No.2015TDJH101)
文摘Objective A succession with well-developed soft-sediment deformation structures and well-exposed gravity-flow deposits in the Early Cretaceous Lingshandao Formation has caused considerable controversy on whether the nondisputed deltaic environment was marine or continental.This dispute cannot be solved by mere sedimentological analysis and,moreover,too few fossils are present to be decisive.The main objective of the present contribution
基金supported by the National Scientific Foundation of China (Grant no. 41506085)the Open Foundation of the Key Laboratory of Gas Hydrate, Ministry of Land and Resources, China (Grant no. SHW [2014]-DX-12)the China Geological Survey Project (Grant no. DD20160213)
文摘When used with large energy sparkers, marine multichannel small-scale high-resolution seismic detection technology has a high resolution, high-detection precision, a wide applicable range, and is very flexible. Positive results have been achieved in submarine geological research, particularly in the investigation of marine gas hydrates. However, the amount of traveltime difference information is reduced for the velocity analysis under conditions of a shorter spread length, thus leading to poorer focusing of the velocity spectrum energy group and a lower accuracy of the velocity analysis. It is thus currently debatable whether the velocity analysis accuracy of short-arrangement multichannel seismic detection technology is able to meet the requirements of practical application in natural gas hydrate exploration. Therefore, in this study the bottom boundary of gas hydrates(Bottom Simulating Reflector, BSR) is used to conduct numerical simulation to discuss the accuracy of the velocity analysis related to such technology. Results show that a higher dominant frequency and smaller sampling interval are not only able to improve the seismic resolution, but they also compensate for the defects of the short-arrangement, thereby improving the accuracy of the velocity analysis. In conclusion, the accuracy of the velocity analysis in this small-scale, high-resolution, multi-channel seismic detection technology meets the requirements of natural gas hydrate exploration.
基金supported by the National Natural Science Foundation of China(42006181,42176212,41976205,41876051)the Youth Foundation of Natural Science Foundation of Shandong Province(ZR2020QE109)+1 种基金the National Key Research and Development Project(2018YFE0126400)the Marine S&T Fund of Shandong Province for Pilot National Laboratory for Marine Science and Technology(Qingdao)(2021QNLM020002).
文摘Grain-displacing hydrate deposits exist at many marine sites,which constitute an important part of methane hydrate resources worldwide.Attributed to the difficulties in acquiring field data and synthesizing experimental samples,the formation and property characterization of grain-displacing hydrate remains less understood and characterized than the pore-filling hydrate in current literature.This study reviews the formation mechanisms of grain-displacing hydrate from the perspective of geological accumulation and microscale sedimentary property.The experimental methods of synthesizing grain-displacing hydrate in the laboratory and the current knowledge on the property of grain-displacing hydrate sediment are also introduced.Shortcomings in current theories and suggestions for future study are proposed.The work is hoped to provide valuable insights for the research into the hydrate accumulation,geophysics,and hydrate exploitation targeted at the grain-displacing hydrate in the marine sediments.
基金the Natural Science Foundation of China (41606086 and 91858208)National Key Research and Development Program (2017YFC0307704)the Marine Geological Survey project of China Geological Survey (DD20160218).
文摘1.Objectives As about 99% of the natural gas hydrate (NGH)resources are stored on the seafloor,it is inevitable that in its process of exploration and production,there will be geohazards such as methane leakage,seabed subsidence,ecosystem damage and even landslide.Therefore,a set of integrated systems for environmental monitoring in the process of NGH production has been proposed in the consideration of environmental disasters that may arise in the process of hydrate production.
基金supported by the National Natural Science Foundation of China(Grant No.9132820142006068)Shandong Special Fund of Qingdao National Laboratory of Marine Science and Technology(No.2021QNLM020001-1).
文摘Notable differences in the structural characteristics and evolution of three adjacent sub-sags,i.e.,the Wenchang sub-sags A,B,and C,on the downthrown side of the Zhu IlI South Fault in the Wenchang Sag,are significant as they affect the formation and distribution of the oil and gas in these three sub-sags.However,the differences in their tectonic evolutions and formation mechanisms have not yet been adequately explained.In this paper,stress analysis,equilibrium profiles,and paleogeomorphic restora-tion,are used to investigate the dynamic settings,formation mechanisms,and influencing factors of the structural deformation related to the formation of the Wenchang Sag based on interpretation of seismic data.The results of the stress analysis suggest clockwise deflection of the regional tensile stress direction from a WNW-ESE trend during the Early Paleocene to NW-SE and NNW-SSE trends during the Eocene,to a nearly N-S trend during the Oligocene,and finally to a NNE-SSW trend during the Miocene.This clockwise rotation of the regional tensile stress direction led to the formation of a dextral strike-slip stress component parallel to the NE-trending Zhu I South Fault.This strike-slip stress component formed a releasing bend in sub-sag A,and may be associated with the continuous subsidence of a thick sedimentary layer in sub-sag A.It also created a restraining bend in sub-sag B,which underwent multiple structural inversions during its extension and subsidence and has a relatively s mall sedimentary thick-ness.The double restraining bend in sub-sag C is considered to have been strongly uplifted and eroded in response to this strike-slip stress component.Four obvious structural inversions in sub-sag B are iden-tified in this paper.These structural inversions correspond to the last four regional tectonic movements.This interpretation suggests that the formation of the structural inversions was likely related to the strong tensile stress and the small intersection angle between the direction of the regional tensile stress and the pre-existing boundary fault.The rotation of the tensile stress direction was responsible for the strike-slip movement on the pre-existing boundary fault and the formation of the releasing bend and restraining bend,which controlled the structural evolutions of the sub-sags.This reasonably explains the differential tectonic evolution of these three sub-sags in the Wenchang Sag,and provides a crucial idea forstructuralanalysisof similarbasins.
基金financially supported by the National Key R&D Plan of China (Grant No. 2017YFC0601405)the National Natural Science Foundation of China (Grant No. 41772096)+1 种基金the Youth Innovation Team Development Plan of Universities in Shandong Province, the Shandong Province Key Research and Development Plan (Grant No. 2019GGX103021)the SDUST Research Fund (Grant No.2018TDJH101)
文摘Core samples from the deeply buried Ordovician Majiagou Formation below the Huainan Coalfield(E China) have been investigated for their carbonate types,major and trace elements(including rare earth elements) and C and O isotopes,The objective was to get a better insight into the possible occurrences of gas(and possibly oil) derived from Carboniferous coals.It was found that the carbonates are dolomites with strongly varying amounts of CaO and MgO.The low concentrations of SiO_(2),Al_(2)O_(3),and Fe_(2)O_(3)indicate deposition in a normal marine environment with little terrigenous input,The Na_(2)O/K_(2)O,Fe/Mn and Sr/Ba ratios,as well as the Ga values indicate mainly a marine salinity and a hot and humid climate.The slight depletion of Ce and Eu,the depletion of heavy rare earth elements(HREE) and the enrichment of light rare earth elements(LREE) indicate deposition in a reducing environment.It thus appears that the Majiagou Formation below the Huainan Coalfield closely resembles that in the eastern part of the Ordos Basin,where several gas reservoirs are present,so that the Majiagou Formation under the Huainan Coalfield represents a promising target for hydrocarbon exploration.
基金funded by the Natural Science Foundation of China Project(Grant Nos.41821002,41872140)the Special fund for Taishan Scholar Project(Grant No.tsqn201909061)the Fundamental Research Funds for the Central Universities(Grant No.20CX06067A)。
文摘Organic-inorganic interactions between hydrocarbons and most minerals in deeply buried reservoirs remain unclear.In this study,gold capsules and fused silica capillary capsules(FSCCs)with different com-binations of nC_(16)H_(34),water(distilled water,CaCl_(2) water)and minerals(quartz,feldspar,calcite,kaolinite,smectite,and illite)were heated at 340℃ for 3-10 d,to investigate the evolution and reaction pathways of the organic-inorganic interactions in different hot systems.After heating,minerals exhibited little alteration in the anhydrous systems.Mineral alterations,how-ever,occurred obviously in the hydrous systems.Different inorganic components affected nC_(16)H_(34) degra-dation differently.Overall,water promoted the free-radical thermal-cracking reaction and step oxidation reaction but suppressed the free-radical cross-linking reaction.The impact of CaCl_(2) water on the nC_(16)H_(34) degradation was weaker than the distilled water as high Ca^(2+)concentration suppressed the formation of free radicals.The presence of different waters also affects the impact of different minerals on nC_(16)H_(34) degradation,via its impact on mineral alterations.In the anhydrous nC_(16)H_(34)-mineral systems,calcite and clays catalyzed generation of low-molecular-weight(LMW)alkanes,particularly the clays.Quartz,feldspar,and calcite catalyzed generation of high-molecular-weight(HMW)alkanes and PAHs,whereas clays catalyzed the generation of LMW alkanes and mono-bicyclic aromatic hydrocarbons(M-BAHs).In the hydrous nC_(16)H_(34)-distilled water-mineral systems,all minerals but quartz promoted nC_(16)H_(34) degra-dation to generate more LMW alkanes,less HMW alkanes and PAHs.In the nC_(16)H_(34)-CaCl_(2) water-mineral systems,the promotion impact of minerals was weaker than that in the systems with distilled water.This study demonstrated the generation of different hydrocarbons with different fluorescence colors in the different nC_(16)H_(34)-water-mineral systems after heating for the same time,implying that fluorescence colors need to be interpreted carefully in investigation of hydrocarbon charging histories and oil origins in deeply buried reservoirs.Besides,the organic-inorganic interactions in different nC_(16)H_(34)-water-mineral systems proceeded in different pathways at different rates,which likely led to preservation of liquid hydrocarbons at different depth(temperature).Thus,quantitative investigations of the reaction kinetics in different hydrocarbon-water-rock systems are required to improve the prediction of hydrocar-bon evolution in deeply buried hydrocarbon reservoirs.
基金The Taishan Scholar Special Experts Project of Shandong Province under contract No.ts201712079the National Natural Science Foundation of China under contract No.41976074the National Key Research and Development Program of China under contract No.2018YFE0126400。
文摘Laboratory visual detection on the hydrate accumulation process provides an effective and low-cost method to uncover hydrate accumulation mechanisms in nature.However,the spatial hydrate distribution and its dynamic evolutionary behaviors are still not fully understood due to the lack of methods and experimental systems.Toward this goal,we built a two-dimensional electrical resistivity tomography(ERT)apparatus capable of measuring spatial and temporal characteristics of hydrate-bearing porous media.Beach sand(0.05–0.85 mm)was used to form artificial methane hydrate-bearing sediment.The experiments were conducted at 1°C under excess water conditions and the ERT data were acquired and analyzed.This study demonstrates the utility of the ERT method for hydrate mapping in laboratory-scale.The results indicate that the average electrical conductivity decreases nonlinearly with the formation of the hydrate.At some special time-intervals,the average conductivity fluctuates within a certain scope.The plane conductivity fields evolve heterogeneously and the local preferential hydrate-forming positions alternate throughout the experimental duration.We speculate that the combination of hydrate formation itself and salt-removal effect plays a dominant role in the spatial and temporal hydrate distribution,as well as geophysical parameters changing behaviors during hydrate accumulation.
基金the Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology(No.MMRKF201810)the China Geological Survey(Nos.DD20190582,DD20191009,DD20160214)funded by the Shandong Province"Taishan Scholar"Construction Project。
文摘To investigate the nature of gas hydrates in the Makran area,new high-resolution geophysical data were acquired between 2018-2019.The data collected comprise multibeam and two-dimensional multi-channel seismic reflection data.The multibeam bathymetry data show East-North-East(ENE)ridges,piggy-back basins,canyon and channel systems,and the morphology of the abyssal plain.Continuous and discontinuous bottom simulating reflectors(BSRs)occur in the piggy-back basins on most of the seismic profiles available.The BSRs cut the dipping layers with strong amplitude and reversed polarity.Discontinuous BSRs indicate a transition along a dipping high-permeable sand layers from gas-rich segment to the gas hydrate-bearing segment and sugge st alternating sediments of fine and relatively coarse grain size.Double BSRs are highly dynamic and attributed to slumps occurring in the study area.The BSRs induced by slumps are located both at deep and shallow depths,responding to the temperature or pressure variation.For the first time,BSRs are observed in the abyssal plain of the Makran area,being associated with anticline structures,which do not show large spatial continuity and are strongly conditioned by structural conditions such as anticlines and fluid migration pathways,including deep fault,gas chimney,and high-permeable sedimentary layer.Our results may help to assess the gas hydrate potential within the piggy-back basins and to determine the most promising target areas.Moreover,results about the abyssal plain BSR may help to locate hydrocarbon reservoirs in the deep ocean.
基金financial supports received from the National Natural Science Foundation of China(42174136,41821002 and 41874151)the Shandong Provincial Natural Science Foundation,China(ZR2021JQ14).
文摘Fractured hydrate-bearing reservoirs show significantly anisotropic geophysical properties. The joint application of seismic and electromagnetic explorations is expected to accurately assess hydrate resources in the fractured reservoirs. However, the anisotropic joint elastic-electrical properties in such reservoirs that are the key to the successful application of the joint explorations, remain poorly understood. To obtain such knowledge, we designed and implemented dedicated laboratory experiments to study the anisotropic joint elastic-electrical properties in fractured artificial silica sandstones (with fracture density of about 6.2%, porosity of approximately 25.7%, and mean grainsize of 0.089 mm) with evolving methane hydrate. The experimental results showed that the anisotropic compressional wave velocities respectively increased and decreased with the forming and dissociating hydrate, and the variation in the increasing trend and the decreasing extent of the velocity perpendicular to the fractures were more significant than that parallel to the fractures, respectively. The experimental results also showed that the overall decreasing trend of the electrical conductivity parallel to the fractures was steeper than that perpendicular to the fractures during hydrate formation, and the general variations of the two conductivities with complex trend were similar during hydrate dissociation. The variations in the elastic and electrical anisotropic parameters with forming and dissociating hydrate were also found to be distinct. Interpretation of the experimental results suggested that the hydrate binding to the grains evolved to bridge the surfaces of fractures when saturation exceeded 10% during hydrate formation, and the bridging hydrate gradually evolved to floating in fractures during dissociation. The experimental results further showed that the anisotropic velocities and electrical conductivities were correlated with approximately consistent trends of different slopes during hydrate formation, and the joint elastic-electrical anisotropic parameters exhibited a sharp peak at the hydrate saturation of about 10%. The results suggested that the anisotropic joint properties can be employed not only to accurately estimate hydrate saturation but also possibly to identify hydrate distribution in the fractures.
基金supported by the Laoshan Laboratory(No.LSKJ LSKJ202203506)the Taishan Scholars Program,and the National Natural Science Foundation of China(Grant No.41976074).
文摘Sand production is one of the main obstacles restricting gas extraction efficiency and safety from marine natural gas hydrate(NGH)reservoirs.Particle migration within the NGH reservoir dominates sand production behaviors,while their relationships were rarely reported,severely constrains quantitative evaluation of sand production risks.This paper reports the optical observations of solid particle migration and production from micrometer to mesoscopic scales conditioned to gravel packing during depressurization-induced NGH dissociation for the first time.Theoretical evolutionary modes of sand migration are established based on experimental observations,and its implications on field NGH are comprehensively discussed.Five particle migration regimes of local borehole failure,continuous collapse,wormhole expansion,extensive slow deformation,and pore-wall fluidization are proved to occur during depressurization.The types of particle migration regimes and their transmission modes during depressurization are predominantly determined by initial hydrate saturation.In contrast,the depressurization mainly dominates the transmission rate of the particle migration regimes.Furthermore,both the cumulative mass and the medium grain size of the produced sand decrease linearly with increasing initial methane hydrate(MH)saturation.Discontinuous gas bubble emission,expansion,and explosion during MH dissociation delay sand migration into the wellbore.At the same time,continuous water flow is a requirement for sand production during hydrate dissociation by depressurization.The experiments enlighten us that a constitutive model that can illustrate visible particle migration regimes and their transmission modes is urgently needed to bridge numerical simulation and field applications.Optimizing wellbore layout positions or special reservoir treatment shall be important for mitigating sand production tendency during NGH exploitation.
基金Supported by the Natural Science Foundation of Shandong Province(No.ZR2022MD074)the Laboratory for Marine Mineral Resources+3 种基金Qingdao National Laboratory for Marine Science and Technology(No.MMRKF201810)the National Natural Science Foundation of China(No.41606077)the National Key R&D Program of China:HighPrecision Characterization Technology of Gas Hydrate Reservoir(No.2017YFC0307406-03)supported by the Shandong Province Taishan Scholar Construction Project。
文摘Submarine seep plumes are a natural phenomenon in which different types of gases migrate through deep or shallow subsurface sediments and leak into seawater in pressure gradient.When detected using acoustic data,the leaked gases frequently exhibit a flame-like structure.We numerically modelled the relationship between the seismic response characteristic and bubble volume fraction to establish the bubble volume fraction in the submarine seep plume.Results show that our models are able to invert and predict the bubble volume fraction from field seismic oceanography data,by which synthetic seismic sections in different dominant frequencies could be numerically simulated,seismic attribute sections(e.g.,instantaneous amplitude,instantaneous frequency,and instantaneous phase)extracted,and the correlation between the seismic attributes and bubble volume fraction be quantitatively determined with functional equations.The instantaneous amplitude is positively correlated with bubble volume fraction,while the instantaneous frequency and bubble volume fraction are negatively correlated.In addition,information entropy is introduced as a proxy to quantify the relationship between the instantaneous phase and bubble volume fraction.As the bubble volume fraction increases,the information entropy of the instantaneous phase increases rapidly at the beginning,followed by a slight upward trend,and finally stabilizes.Therefore,under optimal noise conditions,the bubble volume fraction of submarine seep plumes can be inverted and predicted based on seismic response characteristics in terms of seismic attributes.
基金Supported by the China National Natural Science Foundation(41872140)Taishan Scholars and Young Experts Project(201909061)+1 种基金Qingdao Marine Science and Technology Pilot Special Fund for National Laboratory in Shandong Province(2021QNLM020001)Central University Innovation Fund(20CX06067A).
文摘The element geochemical characteristics and diagenetic alteration products of tuffaceous components in sandstone reservoirs of Paleogene Wenchang Formation in typical subsags of the Huizhou-Lufeng area of the Zhu I Depression,Pearl River Mouth Basin,were identified through microscopic analysis and quantitative analysis of main and trace elements.The impacts of dissolution of different tuffaceous components on physical properties of reservoirs were discussed through quantitative characterization of reservoir physical properties.The results show that there are mainly four types of tuffaceous components in the study area,which are acidic,intermediate,basic and alkaline tuffaceous components.The acidic tuffaceous components evolved in a process of strong alteration and weak dissolution of alteration products,with a large amount of kaolinite precipitated during alteration to disenable the improvement of porosity and permeability.The intermediate and alkaline tuffaceous components evolved in a process of strong dissolution of tuffaceous components and strong alteration of residual tuffaceous components;the dissolution of tuffaceous components created intergranular pores,but the alteration products such as autogenic quartz,apatite and illite deteriorated the pore structure;ultimately,the dissolution of tuffaceous components resulted in the increase of porosity but no increase of permeability of the reservoir.The basic tuffaceous components dominantly evolved in a process of dissolution of tuffaceous components to strong dissolution of alteration products;both tuffaceous components between particles and laumontite generated from alteration can be strongly dissolved to create pores;thus,the dissolution of tuffaceous components can significantly increase the physical properties of the reservoir.
基金The National Natural Science Foundation of China under contract Nos 42276084 and 42176078the Special survey items of the China Geological Survey under contract Nos DD20190205 and DD20221710。
文摘The composition,provenance,and genetic mechanism of sediment on different sedimentary units of the East China Sea(ECS)shelf are essential for understanding the depositional dynamics environment in the ECS.The sediments in the northern ECS shelf are distributed in a ring-shaped distribution centered on the southwestern Cheju Island Mud.From the inside to the outside,the grain size goes from fine to coarse.Aside from the“grain size effect”,hydrodynamic sorting and mineral composition are important restrictions on the content of rare earth elements(REEs).Based on the grain size,REEs,and clay mineral composition of 300 surface sediments,as well as the sedimentary genesis,the northern ECS shelf is divided into three geochemical zones:southwestern Cheju Island Mud Area(ZoneⅠ),Changjiang Shoal Sand Ridges(ZoneⅡ-1),Sand Ridges of the East China Sea shelf(ZoneⅡ-2).The northern ECS shelf is mostly impacted by Chinese mainland rivers(the Changjiang River and Huanghe River),and the provenance and transport mechanism of sediments of different grain sizes is diverse.The bulk sediments come primarily from the Changjiang River,with some material from the Huanghe River carried by the Yellow Sea Coastal Current and the North Jiangsu Coastal Current,and less from Korean rivers.Among them,surface sediments in the southwestern Cheju Island Mud Area(ZoneⅠ)come mostly from the Changjiang River and partly from the Huanghe River.It was formed by the counterclockwise rotating cold eddies in the northern ECS shelf,which caused the sedimentation and accumulation of the fine-grained sediments of the Changjiang River and the Huanghe River.The Changjiang Shoal Sand Ridges(ZoneⅡ-1)were developed during the early-middle Holocene sea-level highstand.It is the modern tidal sand ridge sediment formed by intense hydrodynamic action under the influence of the Yellow Sea Coastal Current,North Jiangsu Coastal Current,and Changjiang Diluted Water.The surface sediments mainly originate from the Changjiang River and Huanghe River,with the Changjiang River dominating,and the Korean River(Hanjiang River)influencing just a few stations.Sand Ridges of the East China Sea shelf(ZoneⅡ-2)are the relict sediments of the paleo-Changjiang River created by sea invasion at the end of the Last Deglaciation in the Epipleistocene.The clay mineral composition of the surface sediments in the study area is just dominated by the Changjiang River,with the North Jiangsu Coastal Current and the Changjiang Diluted Water as the main transporting currents.
基金Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Nos.XDB42010203,XDA19060401)the National Natural Science Foundation of China(Nos.42176090,41776011)。
文摘There is a vast upwelling area induced by the southeast monsoon in the waters off South Java,making the region an important fishing ground.Climate events can affect the variation of upwelling,but oceanographers have different understandings on the extent to which climate events control upwelling in this area,which leads to a lack of basis for studies on the evaluation and mechanisms of the variability of fishery resources in the region.The correlation between environmental parameters,including surface temperature(SST),chlorophyll-a(Chl-a)concentration,and climate event indices in South Java from 2003 to 2020 was analyzed.Results show that the Indian Ocean Dipole(IOD)has a greater influence on the interannual variability of upwelling intensity than ENSO.During the IOD,variations in equatorial latitudinal winds excite different types of Kelvin waves that anomalously deepen or shallow the thermocline,which is the main cause of anomalous variations in upwelling,independent of variations in the local wind field.A correlation between the interannual variability in upwelling and the annual catches was revealed,showing that climatic events indirectly affect fishery resources through upwelling effects.During positive IOD/El Niño periods,strong upwelling delivers more nutrients to the surface layer,which favors fish growth and reproduction,resulting in higher annual catches.A negative IOD/La Niña,on the other hand,leads to weaker upwelling and fewer nutrients into the surface waters.Fish tend to move in deeper waters,making traditional fishing methods less efficient and consequently lower annual catches.
基金Supported by the National Natural Science Foundation of China(No.91958211)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB42020000)+1 种基金the Laoshan Laboratory Project(No.LSKJ202203503)the Key Deployment Project of Center for Ocean Mega-Research of Science,Chinese Academy of Sciences(No.COMS2019Q10).Dr.Wei LI is funded by the CAS Pioneer Hundred-Talents Program。
文摘Submarine canyon-channel systems have been documented in the Parece Vela Basin,West Mariana Ridge;however,the mechanism of the formation and controlling factors remain poorly understood.Based on high-resolution multibeam bathymetric data and two-dimensional(2D)seismic profiles,we identified and mapped the submarine canyon-channel system along the middle segment of West Mariana Ridge in the Philippine Sea.These submarine canyon-channels show a main W-E orientation at depth of 2000–4500 m.They are approximately 72–128 km in length and 1.3–15 km in width,and their canyon heads are adjacent to the seamounts with several branches.The upper reaches of submarine canyon-channels are characterized by deeply incised,narrow,V-shaped thalwegs,suggesting the powerful erosion of gravity flows.The distinguished sediment waves are suggested to be resulted from the interaction of turbidity currents and seafloor.Our observations demonstrate that gravity flows originated from the collapses of seamount flanks plays a vital role in developing the submarine canyonchannel system along the West Mariana Ridge.This work provides better understanding of erosion,transport,and deposition of sediments from subducting ridges to deep-water basins,and also new insights into the origin and evolution of submarine canyon-channel systems along subducting ridges.
基金supported by the National Natural Science Foundation of China(Nos.42072130,41872152).
文摘Based on the petrology,isotope geochemistry and fluid inclusions analysis,we established the evolutionary mode of the diagenetic fluid of dawsonite-bearing sandstone in the Jiyang Depression.Dawsonite-bearing sandstone is characterized by double injection of CO_(2)and oil-gas in the Jiyang Depression that have experienced a relatively complex diagenetic fluid evolution process.The diagenetic sequence of secondary minerals involves secondary enlargement of quartz,kaolinite,first-stage calcite,dawsonite,second-stage calcite,ferrocalcite,dolomite and ankerite.Hydrocarbon charging in the dawsonite-bearing sandstone occurred at around 2.6–0 Myr.The CO_(2)charging event occurred during Dongying tectonism,forming the Pingfangwang CO_(2)gas reservoir,which provided an abundant carbon source for dawsonite precipitation.Carbon and oxygen isotopic compositions of dawsonite demonstrate that CO_(2)forming the dawsonite was of an inorganic origin derived from the mantle,and that water mediating the proc-ess during dawsonite precipitation was sequestered brine with a fluid temperature of 82℃.The evolutionary sequence of the diagenetic fluid in the dawsonite-bearing sandstone was:alkaline syngenetic fluids,weak alkaline fluids during organic acid forma-tion,acidic fluids in the early stage of CO_(2)injection,alkaline fluids in the late stage of CO_(2)injection,and weak alkaline fluids during oil and gas charging.The mode indicates an increase in-HCO_(3)because of the CO_(2)injection,and the loss of Ca^(2+)and Mg^(2+)due to the precipitation of carbonate minerals.Therefore,the evolutionary mode of diagenetic fluids is in good agreement with high HCO_(3)^(-),low Ca^(2+)and low Mg^(2+)composition of the present formation water in the dawsonite-bearing sandstone.
