查看更多>>摘要：An improved evaluation method for estimating gas content during the inversion process of deep-burial coal was established based on the on-site natural desorption curves.The accuracy of the US Bureau of Mines(USBM),Polynomial fitting,Amoco,and the improved evaluation methods in the predicting of lost gas volume in deep seams in the Mabidong Block of the Qinshui Basin were then compared.Furthermore,the calculation errors of these different methods in simulating lost gas content based on coring time were compared.A newly established nonlinear equation was developed to estimate the minimum error value,by controlling the lost time within 16 min,the related errors can be reduced.The improved evaluation was shown to accurately and rapidly predict the gas content in deep seams.The results show that the deep coal bed methane accumulation is influenced by various factors,including geological structure,hydrodynamic conditions,roof lithology,and coalification.Reverse faults and weak groundwater runoff can hinder the escape of methane,and these factors should be considered in the future exploration and development of coalbed methane.
查看更多>>摘要：It is crucial to investigate the characteristics of fire danger in the areas around Beijing to increase the accuracy of fire danger monitoring,forecasting,and management.Using meteorological data from 17 national meteorological stations in the areas around Beijing from 1981-2021,this study calculated the fire weather index(FWI)and analyzed its spatiotemporal characteristics.It was found that the high and low fire danger periods were in April-May and July-August,with spatial patterns of"decrease in the northwest-increase in the southeast"and a significant increase throughout the areas around Beijing,respectively.Next,the contributions of different meteorological factors were quantified by the multiple regression method.We found that during the high fire danger period,the northern and southern parts were affected by precipitation and minimum relative humidity,respectively.However,most areas were influenced by wind speed during the low fire danger period.Finally,comparing with the FWI characteristics under different SSP scenarios,we found that the FWI decreased during high fire danger period and increased during low fire danger period under different SSP scenarios(i.e.,SSP245,SSP585)for periods of 2021-2050,2071-2100,2021-2100,except for SSP245 in 2071-2100 with an increasing trend both in high and low fire danger periods.This study implies that there is a higher probability of FWI in the low fire danger period,threatening the ecological environment and human health.Therefore,it is necessary to enhance research on fire danger during the low fire danger period to improve the ability to predict summer fire danger.
查看更多>>摘要：The major controlling factors of organic matter and its enrichment model of the black shale from the Wufeng-Longmaxi Formation were explored by investigating the vertical variation characteristics,as well as major element and trace element abundances in the Wuxi Bailu section.The results show that the sedimentary tectonic setting of the Wufeng-Longmaxi Formation in the north-east margin of the upper Yangtze platform is located on the active continental margin,which is a passive continental margin and continental island arc.The parent rock in the source area is mainly felsic volcanic rocks mixed with small amounts of sedimentary recycling materials.Due to increased plate activity and a drop in sea levels,terrigenous pyroclastic input increased.The palaeoclimate was semi-humid,and a robust dysoxic-reduction environment and a high level of palaeoproduc-tivity,causing the formation of the organic-rich shale in the Wufeng Formation.At the base of the Longmaxi Formation,the sedimentary water body was affected by global transgression,showing a strong anoxic-reductive environment,and the paleoclimate was a warm and humid condition.The palaeoproductivity level was high,resulting in the formation of organic shale.Due to the sea level drop at the top of the Longmaxi Formation,the sedimentary water was in an oxic-reduced environment,but the input of terrigenous pyroclastic matter increased.Because the paleoclimate was warm and humid and the palaeoproduc-tivity level was high,organic-rich shale was formed.The findings demonstrate that terrigenous clastic input circumstances,palaeoproductivity conditions,and paleo-redox conditions had the greatest influence on the enrichment of organic matter in the Wufeng-Longmaxi Formation.Thus,organic matter enrichment was control-led by multiple paleoenvironmental factors.
查看更多>>摘要：A sandy,braided river is a typical type of river that exists in ancient and modem alluvial plains and is inherent with significant seasonal water discharge variations.The variations play an important role in the depositional process and the formation of the sediment-ary architecture of braided rivers.In this paper,a braided river outcrop along the Yellow River in Fugu is used to describe the effects of seasonal hydrodynamic variations on braided river sedimentary architecture.The results show that the braided channel network exhibits two different patterns during flood period and normal period.During flood periods,the main braided channels surrounding channel bars and the secondary braided channels distributed on the top of the channel bars coexist,forming a highly braided channel network.Migration of the main braided channels control the formation of middle channel bars and side bars.The generation and evolution of the secondary braided channels reformed the upper part of preexisting channel bars and produced affiliated bars along their flow path.During the normal period,water levels decrease,causing the secondary river channels to be abandoned and forming abandoned channels,and only the main braided channels stay active.In the long term sedimentation process,strong water flow during the flood period continuously erodes pre-existing sediments and forms new sediments,while weak water flow during the normal period can only reform the main braided channels and their adjacent channel bar sediments.Based on differences in sedimentary processes and associated hydrodynamic conditions,braided river sediments are divided into two combinations.The strong hydrodynamic combination includes main braided channels,middle channel bar,and side bar,while the weak hydrodynamic combination includes secondary braided channels,abandoned channels,and affiliated bars.The proportion of strong hydrodynamic combinations is much larger than that of weak hydrodynamic combinations.Based on this,we construct a braided river sedimentary architecture model that is helpful for the fine characterization of subsurface oil and gas reservoirs.
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