查看更多>>摘要：Overmature continental shale is commonly developed,but few studies have given insight into its pore structure and sorption capacity.Various techniques,including SEM,helium porosity and permeability,N2/CO2 adsorption,MICP,and NMR,were used to detect the pore structure of shale from the Shahezi Formation,Xujiaweizi Fault,Songliao Basin.The excess methane adsorption volumes were measured by the volumetric method and modeled by the Langmuir model.Based on the findings,the most developed pores are intraparticle pores in clay minerals,followed by the dissolution pores in feldspar,but organic pores are uncommon.The selected shales have low helium porosity(mean 1.66％)and ultralow permeability(mean 0.0498 × 10-3μm2).The pore throats are at the nanoscale,and the pore-throat size distributions are unimodal,with most less than 50 nm.The studied shales are characterized by the lower specific surface area(SSA)and pore volume(PV)but the larger average pore diameter.The total SSA is contributed by the micro-and mesopores,while the PV is dominated by meso-and macropores.The pore structures are more complex and controlled by multiple factors,such as mineral compositions and diagenesis,but organic matter is not critical.The maximum absolute adsorption methane volume(VL)is 0.97-3.58 cm3/g(mean 1.90 cm3/g),correlating well with the total SSA,SSA,and pore volume of micropores,which indicates that methane is mainly adsorbed and stored in micropores,followed by mesopores.
查看更多>>摘要：Normal-pressure shale gas reservoirs are widely distributed in south-eastern Chongqing and show good potential for resource exploration.This paper reports the organic matter(OM),physical,and pore characteristics,mineral composition,and gas content of representative shale samples from the Upper Ordovician Wufeng Formation and Member 1 of the Lower Silurian Longmaxi Formation(Long 1 Member).Microscopic pores within different shale layers of the Long 1 Member were classified,quantitatively evaluated,and their development mechanisms were systematically studied.We found that OM characteristics,mineral composition,and pore type were the main factors affecting the enrichment and preservation of shale gas.The characteristics of the Long 1 Member are mainly controlled by changes in the sedimentary environment.There are evident differences in total organic carbon content and mineral composition vertically,leading to a variable distribution of pores across different layers.Organic matter abundance controls the degree of OM pore development,while clay minerals abundance control the development of clay mineral-related pores.Total organic carbon content generally controls the porosity of the Long 1 Member,but clay minerals also play a role in OM-poor layers.Pore connectivity and permeability are influenced by the development of pores associated with brittle minerals.We propose a microscopic pore development model for the different layers.Combining geochemical data and this pore development model,layers 1-4 are considered to be excellent shale gas preservation and enrichment reservoirs.Poor preservation conditions in layers 5-7 result in high levels of shale gas escape.Layers 8-9 possess a better sealing condition compared with layers 5-7 and are conducive to the enrichment and preservation of shale gas,and can thus be used as future potential target strata.This research provides a theoretical basis for exploring and evaluating shale gas potential in the studied region or other complex normal-pressure shale blocks.
查看更多>>摘要：It has always been challenging to determine the ancient sedimentary environment and associated energy in deep-buried marine carbonates.The energy represents the hydrodynamic conditions that existed when the carbonates were deposited.The energy includes light and chemical energies in compounds and kinetic energy in currents and mass flow.Deep-buried marine carbonates deposited during the Ordovician depositional period in the eastern Tarim Basin result from a complex interplay of tectonics,sedimentation,and diagenesis.As a result,determining the ancient sedimentary environment and associated energy is complex.The natural gamma-ray spectrometry(GRS)log(from 12 wells)is used in this paper to conduct studies on the sedimentary environment and associated energy in deep-buried marine carbonates.The findings show that the values of thorium(Th),uranium(U),potassium(K),and gamma-ray without uranium(KTh)in a natural GRS log can reveal lithological associations,mineral composition,diagenetic environment,stratigraphic water activity,and ancient climatic change.During the Ordovician,quantitative analysis and determination of sedimentary environment energy are carried out using a comprehensive calculation of natural GRS log parameters in typical wells(penetrating through the Ordovician with cores and thin sections)of well GC4,well GC6,well GC7,and well GC8.The results show that GRS log can determine different lithology associations in typical wells than a sieve residue log.Furthermore,cores and thin sections can be used to validate the determination of lithology associations.Based on the determination of lithology associations,the lithology associations that reflect the sedimentary environment and associated energy can be analyzed in a new approach.Furthermore,the sedimentary environment energy curve derived from a natural GRS log can reveal hydrodynamic fluctuations during depositional periods,which will aid in the discovery of carbonate reservoirs,establishing sequence stratigraphic frameworks,and the reconstruction of sea-level changes in the future.
查看更多>>摘要：Sedimentation is a key process affecting wetland sustainability and carbon burial flux.In context of sea level rise,climate change and human activities,further understanding about the sedimentary dynamic in wetland is critical in predicting the landscape evolution or the change in carbon burial flux.In this study,based on the field hydrological observation in a mangrove system in the Nanliu River estuary,we found the net flux of suspended sediment to mangrove is 39-72 kg/m in tidal cycles with Turbidity Maximum Zone(TMZ)forming in surface layer and only is 9-18 kg/m in tidal cycles without TMZ.The higher net flux of suspended sediment to mangrove in tidal cycles with TMZ forming in surface layer is attributed to high SSC in rising tide and intense flocculation in mangrove.The significant discrepancy in sedimentation rate in the mangrove patches also can be explained by the probability of TMZ forming in the surface layer of estuary.In future,rapid sea level rising may lead to the change of TMZ pattern in estuary,which will result in non-negligible variation in sedimentation rate in wetlands.According to the present data of sedimentation rate in wetlands,the fragility of wetlands in river estuary may be miscalculated.
查看更多>>摘要：Hydrocarbon exploration in the Dongying Sag is constrained by the development of many Cenozoic transtensional structures with complex patterns and dynamic mechanisms.This study uses seismic interpretation and analog modeling to investigate these transtensional structures.Significant results include dividing these transtensional structures into boundary fault,oblique rifting,and deep strike-slip fault controlled structures,according to the relationships between main and secondary faults.They developed in the steep slope zone,the central sag zone,and the slope zone,respectively.In profile,the transtensional structures formed appear to be semi-flower-like,step-like,or negative-flower-like.In plan-view,they appear to be broom-like,soft-linked,or en-echelon structures.Further,these transtensional struc-tures are controlled by the oblique normal slip of boundary faults,by the oblique extension of sub-sags,and by the later extension of deep strike-slip faults.The geometric deformation of these transtensional structures is controlled by the angles between the regional extension direction and the strike of boundary faults,deep faults,or sub-sags,where a larger angle corresponds to less developed transtensional structures.Further,the transtensional structures in the Dongying Sag were created by multi-phase and multi-directional extensions in the Cenozoic—which is also controlled by pre-existing structures.The strike of newborn secondary faults was determined by the regional extension direction and pre-existing structures.
查看更多>>摘要：Crop type mapping using remote sensing is critical for global agricultural monitoring and food security.However,the complexity of crop planting patterns and spatial heterogeneity pose significant challenges to field data collection,thereby limiting the accuracy of remotely sensed crop mapping.This study proposed a new approach for rapidly collecting field crop data by integrating unmanned aerial vehicle(UAV)images with the YOLOv3(You Only Look Once version 3)algorithm.The impacts of UAV flight altitude and the number of training samples on the accuracy of crop identification models were investigated using peanut,soybean,and maize as examples.The results showed that the average Fl-score for crop type detection accuracy reached 0.91 when utilizing UAV images captured at an altitude of 20 m.In addition,a positive correlation was observed between identification accuracy and the number of training samples.The model developed in this study can rapidly and automatically identify crop types from UAV images,which significantly improves the survey efficiency and provides an innovative solution for acquiring field crop data in large areas.
查看更多>>摘要：This study employs the regional Climate-Weather Research and Forecasting model(CWRF)to first investigate the primary physical mechanisms causing biases in simulating summer precipitation over the Yangtze River Basin(YRB),and then enhance its predictive ability through an optimal multi-physics ensemble approach.The CWRF 30-km simulations in China are compared among 28 combinations of varying physics parameterizations during 1980-2015.Long-term average summer biases in YRB precipitation are remotely correlated with those of large-scale circulations.These teleconnections of biases are highly consistent with the observed correlation patterns between interannual variations of precipitation and circulations,despite minor shifts in their primary action centers.Increased YRB precipitation aligns with a southward shifted East Asian westerly jet,an intensified low-level southerly flow south of YRB,and a south-eastward shifted South Asian high,alongside higher moisture availability over YRB.Conversely,decreased YRB precipitation corresponds to an opposite circulation pattern.The CWRF control con-figuration using the ensemble cumulus parameterization(ECP),compared to other cumulus schemes,best captures the observed YRB precipitation characteristics and associated circulation patterns.Coupling ECP with the Morrison or Morrison-aerosol microphysics and the CCCMA or CAML radiation schemes enhances the overall CWRF skills.Compared to the control CWRF,the ensem-ble average of these skill-enhanced physics configurations more accurately reproduces YRB summer precipitation's spatial distributions,interannual anomalies,and associated circulation patterns.The Bayesian Joint Probability calibra-tion to these configurations improves the ensemble's spatial distributions but compromises its interannual anomalies and teleconnection patterns.Our findings highlight substantial potential for refining the representa-tion of climate system physics to improve YRB precipita-tion prediction.This is notably achieved by realistically coupling cumulus,microphysics,and radiation processes to accurately capture circulation teleconnections.Further enhancements can be achieved by optimizing the multi-physics ensemble among skill-enhanced configurations.
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