China began to build its national shale gas demonstration area in 2012.The central exploration,drilling,and development technologies for medium and shallow marine shale reservoirs with less than 3,500m of buried depth...China began to build its national shale gas demonstration area in 2012.The central exploration,drilling,and development technologies for medium and shallow marine shale reservoirs with less than 3,500m of buried depth in Changning-Weiyuan,Zhaotong,and other regions had matured.In this study,we macroscopically investigated the development history of shale gas in the United States and China and compared the physical and mechanical conditions of deep and shallow reservoirs.The comparative results revealed that themain reasons for the order-ofmagnitude difference between China’s annual shale gas output and the United States could be attributed to three aspects:reservoir buried depth,reservoir physical and mechanical properties,and engineering technology level.The current engineering technology level of China could not meet the requirements of increasing production and reducing costs for deep shale gas reservoirs;they had reached the beneficial threshold development stage and lacked the capacity for large-scale commercial production.We identified several physical and mechanical reasons for this threshold development stage.Deep shale reservoirs were affected by the bedding fracture,low brittleness index,low clay mineral content,and significant areal differences,as well as by the transformation from elasticity to plasticity,difficulty in sanding,and high mechanical and strength parameters.Simultaneously,they were accompanied by six high values of formation temperature,horizontal principal stress difference,pore pressure,fracture pressure,extension pressure,and closure pressure.The key to deep shale gas horizontal well fracturing was to improve the complexity of the hydraulic fracture network,formadequate proppant support of fracture surface,and increase the practical stimulated reservoir volume(SRV),which accompanied visual hydraulic discrete network monitoring.On this basis,we proposed several ideas to improve China’s deep shale gas development involving advanced technology systems,developing tools,and supporting technologies in shale gas exploration and development in the United States.These ideas primarily involved stimulation technologies,such as vertically integrated dessert identification and optimization,horizontal well multistage/multicluster fracturing,staged tools development for horizontal wells,fractures network morphology monitoring by microseismic and distributed optical fiber,shale hydration expansion,soak well,and fracturing fluid flow back.China initially developed the critical technology of horizontal well large-scale and high-strength volume fracturing with a core of“staged fracturing with dense cutting+shorter cluster spacing+fracture reorientation by pitching+forced-sand addition+increasing diameter perforating+proppant combination by high strength and small particle size particles”.We concluded that China should continue to conduct critical research on theories and technical methods of horizontal well fracturing,suitable for domestic deep and ultra-deep marine and marine-continental sedimentary shale,to support and promote the efficient development of shale gas in China in the future.It is essential to balance the relationship between the overall utilization degree of the gas reservoir and associated economic benefits and to localize some essential tools and supporting technologies.These findings can contribute to the flourishing developments of China’s deep shale gas.展开更多
西尼罗病毒(West Nile virus,WNV)是重要的虫媒病毒之一。美国自1999年首次在纽约市发现WNV以来,在WNV感染风险监测和管理方面进行了大量的研究和实践。建立的以蚊子、鸟类为基础的环境监测系统,不仅起到了对WNV感染早期预警的关键作用...西尼罗病毒(West Nile virus,WNV)是重要的虫媒病毒之一。美国自1999年首次在纽约市发现WNV以来,在WNV感染风险监测和管理方面进行了大量的研究和实践。建立的以蚊子、鸟类为基础的环境监测系统,不仅起到了对WNV感染早期预警的关键作用,同时还为下一步制定防控措施提供了依据;采取的虫媒综合管理和分阶段风险响应管理等措施,成功控制了WNV的传染源和传播途径,为减轻其对公共卫生的影响起到了关键作用。本文介绍了美国WNV流行情况、风险监测方法及风险管理措施,以期对我国WNV感染等虫媒传播人兽共患病的流行病学研究、早期预警、口岸风险分析以及科学防控提供依据。展开更多
The concern about the role of aerosols as to their effect in the Earth-Atmosphere system requires observation at multiple temporal and spatial scales. The Moderate Resolution Imaging Spectroradiameters （MODIS） is th...The concern about the role of aerosols as to their effect in the Earth-Atmosphere system requires observation at multiple temporal and spatial scales. The Moderate Resolution Imaging Spectroradiameters （MODIS） is the main aerosol optical depth （AOD） monitoring satellite instrument, and its accuracy and uncertainty need to be validated against ground based measurements routinely. The comparison between two ground AOD measurement programs, the United States Department of Agriculture （USDA） Ultmviolet-B Monitoring and Research Program （UVMRP） and the Aerosol Robotic Network （AERONET） program, confirms the consistency between them. The intercomparison between the MODIS AOD, the AERONET AOD, and the UVMRP AOD suggests that the UVMRP AOD measurements are suited to be an alternative ground-based validation source for satellite AOD products. The experiments show that the spatial-temporal dependency between the MODIS AOD and the UVMRP AOD is positive in the sense that the MODIS AOD compare more favorably with the UVMRP AOD as the spatial and temporal intervals are increased. However, the analysis shows that the optimal spatial interval for all time windows is defined by an angular subtense of around 1° to 1.25°, while the optimal time window is around 423 to 483 minutes at most spatial intervals. The spatial-temporal approach around 1.25° ＆ 423 minutes shows better agreement than the prevalent strategy of 0.25° ＆ 60 minutes found in other similar investigations.展开更多
基金funded by the National Key Research and Development Program of China under Grant No.2020YFC1808102the National Natural Science Foundation of China(Grant Nos.51874328,U1762215)the Strategic Cooperation Technology Projects of CNPC and CUPB(Grant No.ZLZX2020-02).
文摘China began to build its national shale gas demonstration area in 2012.The central exploration,drilling,and development technologies for medium and shallow marine shale reservoirs with less than 3,500m of buried depth in Changning-Weiyuan,Zhaotong,and other regions had matured.In this study,we macroscopically investigated the development history of shale gas in the United States and China and compared the physical and mechanical conditions of deep and shallow reservoirs.The comparative results revealed that themain reasons for the order-ofmagnitude difference between China’s annual shale gas output and the United States could be attributed to three aspects:reservoir buried depth,reservoir physical and mechanical properties,and engineering technology level.The current engineering technology level of China could not meet the requirements of increasing production and reducing costs for deep shale gas reservoirs;they had reached the beneficial threshold development stage and lacked the capacity for large-scale commercial production.We identified several physical and mechanical reasons for this threshold development stage.Deep shale reservoirs were affected by the bedding fracture,low brittleness index,low clay mineral content,and significant areal differences,as well as by the transformation from elasticity to plasticity,difficulty in sanding,and high mechanical and strength parameters.Simultaneously,they were accompanied by six high values of formation temperature,horizontal principal stress difference,pore pressure,fracture pressure,extension pressure,and closure pressure.The key to deep shale gas horizontal well fracturing was to improve the complexity of the hydraulic fracture network,formadequate proppant support of fracture surface,and increase the practical stimulated reservoir volume(SRV),which accompanied visual hydraulic discrete network monitoring.On this basis,we proposed several ideas to improve China’s deep shale gas development involving advanced technology systems,developing tools,and supporting technologies in shale gas exploration and development in the United States.These ideas primarily involved stimulation technologies,such as vertically integrated dessert identification and optimization,horizontal well multistage/multicluster fracturing,staged tools development for horizontal wells,fractures network morphology monitoring by microseismic and distributed optical fiber,shale hydration expansion,soak well,and fracturing fluid flow back.China initially developed the critical technology of horizontal well large-scale and high-strength volume fracturing with a core of“staged fracturing with dense cutting+shorter cluster spacing+fracture reorientation by pitching+forced-sand addition+increasing diameter perforating+proppant combination by high strength and small particle size particles”.We concluded that China should continue to conduct critical research on theories and technical methods of horizontal well fracturing,suitable for domestic deep and ultra-deep marine and marine-continental sedimentary shale,to support and promote the efficient development of shale gas in China in the future.It is essential to balance the relationship between the overall utilization degree of the gas reservoir and associated economic benefits and to localize some essential tools and supporting technologies.These findings can contribute to the flourishing developments of China’s deep shale gas.
文摘西尼罗病毒(West Nile virus,WNV)是重要的虫媒病毒之一。美国自1999年首次在纽约市发现WNV以来,在WNV感染风险监测和管理方面进行了大量的研究和实践。建立的以蚊子、鸟类为基础的环境监测系统,不仅起到了对WNV感染早期预警的关键作用,同时还为下一步制定防控措施提供了依据;采取的虫媒综合管理和分阶段风险响应管理等措施,成功控制了WNV的传染源和传播途径,为减轻其对公共卫生的影响起到了关键作用。本文介绍了美国WNV流行情况、风险监测方法及风险管理措施,以期对我国WNV感染等虫媒传播人兽共患病的流行病学研究、早期预警、口岸风险分析以及科学防控提供依据。
文摘The concern about the role of aerosols as to their effect in the Earth-Atmosphere system requires observation at multiple temporal and spatial scales. The Moderate Resolution Imaging Spectroradiameters （MODIS） is the main aerosol optical depth （AOD） monitoring satellite instrument, and its accuracy and uncertainty need to be validated against ground based measurements routinely. The comparison between two ground AOD measurement programs, the United States Department of Agriculture （USDA） Ultmviolet-B Monitoring and Research Program （UVMRP） and the Aerosol Robotic Network （AERONET） program, confirms the consistency between them. The intercomparison between the MODIS AOD, the AERONET AOD, and the UVMRP AOD suggests that the UVMRP AOD measurements are suited to be an alternative ground-based validation source for satellite AOD products. The experiments show that the spatial-temporal dependency between the MODIS AOD and the UVMRP AOD is positive in the sense that the MODIS AOD compare more favorably with the UVMRP AOD as the spatial and temporal intervals are increased. However, the analysis shows that the optimal spatial interval for all time windows is defined by an angular subtense of around 1° to 1.25°, while the optimal time window is around 423 to 483 minutes at most spatial intervals. The spatial-temporal approach around 1.25° ＆ 423 minutes shows better agreement than the prevalent strategy of 0.25° ＆ 60 minutes found in other similar investigations.
