Based on multiple types of data, the topographical features of the Okinawa Trough(OT) have been characterized and a computation method has been proposed to determine the break point of continental shelf(BOS), foot poi...Based on multiple types of data, the topographical features of the Okinawa Trough(OT) have been characterized and a computation method has been proposed to determine the break point of continental shelf(BOS), foot point of the continental slope(FOS), the central axial point, and the maximum depth point. A total of 48 topographical profiles that crosscut the continental slope have been used to determine the trends of the BOS and FOS(the BOS and FOS lines) in the East China Sea(ECS). The trend of central axial points in the OT has been similarly determined by analyzing 39 topographical profiles across the axis of the trough. The BOS line forms the boundary between the continental shelf and slope. In the ECS, the BOS line roughly follows the 200 m isobath, continuously in the northern and middle parts of the OT, but jumping about somewhat in the south. The FOS line is the boundary between the continental slope and the bottom of the trough. The depth of the FOS increases gradually from north to south in the OT. Intense incisions by canyons into the slope in the southern part of the trough have led to the complex distribution of FOS. Topographical profiles crosscutting the northern, middle, and southern parts of the OT exhibit features that include: a single W-shape, a composite W-shape, and a U-shape, respectively, which suggests that in the middle and northern parts of the trough the central axial points are always located on seamount peaks or ridges associated with linear seamounts, whereas in the south they are found in the center of en echelon depressions. The line formed by the central axial points is the east-west dividing line of the OT, which indicates that the trough is a natural gap that prevents the extension of ECS continental shelf to the east. The distributions of the BOS and FOS lines are influenced by fluctuation of sea levels and submarine canyons, whereas the distribution of axis lines is controlled by tectonics and deposition.展开更多
The soil freezing and thawing process affects soil physical properties,such as heat conductivity,heat capacity,and hydraulic conductivity in frozen ground regions,and further affects the processes of soil energy,hydro...The soil freezing and thawing process affects soil physical properties,such as heat conductivity,heat capacity,and hydraulic conductivity in frozen ground regions,and further affects the processes of soil energy,hydrology,and carbon and nitrogen cycles.In this study,the calculation of freezing and thawing front parameterization was implemented into the earth system model of the Chinese Academy of Sciences(CAS-ESM)and its land component,the Common Land Model(CoLM),to investigate the dynamic change of freezing and thawing fronts and their effects.Our results showed that the developed models could reproduce the soil freezing and thawing process and the dynamic change of freezing and thawing fronts.The regionally averaged value of active layer thickness in the permafrost regions was 1.92 m,and the regionally averaged trend value was 0.35 cm yr–1.The regionally averaged value of maximum freezing depth in the seasonally frozen ground regions was 2.15 m,and the regionally averaged trend value was–0.48 cm yr–1.The active layer thickness increased while the maximum freezing depth decreased year by year.These results contribute to a better understanding of the freezing and thawing cycle process.展开更多
Local scour around bridge piers and abutments is one of the most significant causes of bridge failure.Despite a plethora of studies on scour around individual bridge piers or abutments,few studies have focused on the ...Local scour around bridge piers and abutments is one of the most significant causes of bridge failure.Despite a plethora of studies on scour around individual bridge piers or abutments,few studies have focused on the joint impact of a pier and an abutment in proximity to one another on scour.This study conducted laboratory experiments and flow analyses to examine the interaction of piers and abutments and their effect on clear-water scour.The experiments were conducted in a rectangular laboratory flume.They included 18 main tests(with a combination of different types of piers and abutments)and five control tests(with individual piers or abutments).Three pier types(a rectangular pier with a rounded edge,a group of three cylindrical piers,and a single cylindrical pier)and two abutment types(a wingewall abutment and a semicircular abutment)were used.An acoustic Doppler velocimeter was used to measure the three-dimensional flow velocity for analyses of streamline,velocity magnitude,vertical velocity,and bed shear stress.The results showed that the velocity near the pier and abutment increased by up to 80%.The maximum scour depth around the abutment increased by up to 19%.In contrast,the maximum scour depth around the pier increased significantly by up to l71%.The presence of the pier in the vicinity of the abutment led to an increase in the scour hole volume by up to 87%relative to the case with a solitary abutment.Empirical equations were also derived to accurately estimate the maximum scour depth at the pier adjacent to the abutment.展开更多
The thermal state of frozen ground and its changes are important for understanding environmental change and supporting related applications to the Earth’s Third Pole,which is a hotspot area for science research.Howev...The thermal state of frozen ground and its changes are important for understanding environmental change and supporting related applications to the Earth’s Third Pole,which is a hotspot area for science research.However,challenges remain in data and modelling,meaning that much information is unavailable,especially for the entire Third Pole region.Here,we provided basic statistical data regarding the current state of frozen ground and its changes over the 1960s–2010s across the entire Third Pole by integrating nearly all currently available ground observation data and high-quality spatial data using machine learning models and existing high-quality frozen ground data products.The results show that the current(2000–2018)areal extents of permafrost and seasonally frozen ground in the Third Pole are approximately 1.27×10^(6)km^(2)(1.15×10^(6)to 1.39×10^(6)km^(2))and 2.59×10^(6)km^(2),accounting for 28%and 58%,respectively.The areal extent of permafrost region is approximately 50%(23%–93%)larger than that of permafrost area(land underlain by permafrost),especially in some early maps.The corresponding regional average of the mean annual ground temperature is approximately−1.51℃(−1.75 to−1.27℃)in the permafrost area.The regional average of active layer thickness overlying the permafrost and the maximum frost depth for regions of seasonally frozen ground are 235 cm(233–237 cm)and 92 cm,respectively.From the 1960s to the 2010s,on average,permafrost in the Third Pole warmed at a rate of 0.17℃per decade,which was associated with increases in the maximum thaw depth at a rate of 4.42 cm per decade.The regional average of the maximum frost depth declined at a rate of 2.34 cm per decade over the same period.This synthesis highlights the differences between the two terms(permafrost region and permafrost area)and provides crucial information for frozen ground in the Third Pole with higher accuracy for the scientific community and the public.展开更多
How long the ultra deep well can extend and what is the ultra deep well's maximum hydraulic extension depth are always concerned and studied by drilling engineers. The well's maximum hydraulic extension depth ...How long the ultra deep well can extend and what is the ultra deep well's maximum hydraulic extension depth are always concerned and studied by drilling engineers. The well's maximum hydraulic extension depth can be predicted by the maximum hydraulic extension depth prediction model. To overcome the disadvantage that previous prediction model did not consider the effects of temperature and only applies to horizontal wells, a prediction model of maximum hydraulic extension depth for ultra deep wells considering effects of temperature is established. Considering the effects of temperature coupled with the constraints of drilling pump rated pressure and rated power, the prediction result of ultra deep well's maximum hydraulic extension depth is modified. An ultra deep well developed by Sinopec in Shunbei oilfield, China, is analyzed, and its wellbore temperature profile and maximum hydraulic extension depth are analyzed and predicted. Results show that the maximum hydraulic extension depth with considering temperature is larger than that without considering temperature. With the identical depth, the higher inlet temperature and the greater geothermal gradient mean the higher drilling fluid temperatures in the drill string and annulus as well as the larger maximum hydraulic extension depth. Besides, the maximum depth decreases with the increase in drilling fluid flow rate and density, while it increases with the increase in drilling pump rated pressure and rated power. To ensure the designed depth can be reached, there exists the maximum drilling fluid flow rate and density, as well as the minimum drilling pump rated pressure and rated power. This study is important for accurately predicting the ultra deep well's maximum depth within the limit capacity of drilling pump. In addition, it also plays a major role in avoiding drilling hazards.展开更多
对埕岛油田已建成的水下基盘结构形式进行归纳总结,依据API RP 2A-WSD规范对井口基盘海洋环境荷载进行分析计算,基于SACS程序建立了9口井、12口井形式基盘的有限元计算模型,对水下基盘的适应水深进行静力分析,计算出了相应水深下结构的...对埕岛油田已建成的水下基盘结构形式进行归纳总结,依据API RP 2A-WSD规范对井口基盘海洋环境荷载进行分析计算,基于SACS程序建立了9口井、12口井形式基盘的有限元计算模型,对水下基盘的适应水深进行静力分析,计算出了相应水深下结构的强度,确定水深变化对井口结构安全性的影响,得出了所研究井口基盘的极限水深。展开更多
基金supported by Public Science and Technology Research Funds Project of Ocean(Grant No.201105001)Fundamental Project of Science and Technology(Grant No.2013FY112900)National Natural Science Foundation of China(Grant Nos.40506017,41206046)
文摘Based on multiple types of data, the topographical features of the Okinawa Trough(OT) have been characterized and a computation method has been proposed to determine the break point of continental shelf(BOS), foot point of the continental slope(FOS), the central axial point, and the maximum depth point. A total of 48 topographical profiles that crosscut the continental slope have been used to determine the trends of the BOS and FOS(the BOS and FOS lines) in the East China Sea(ECS). The trend of central axial points in the OT has been similarly determined by analyzing 39 topographical profiles across the axis of the trough. The BOS line forms the boundary between the continental shelf and slope. In the ECS, the BOS line roughly follows the 200 m isobath, continuously in the northern and middle parts of the OT, but jumping about somewhat in the south. The FOS line is the boundary between the continental slope and the bottom of the trough. The depth of the FOS increases gradually from north to south in the OT. Intense incisions by canyons into the slope in the southern part of the trough have led to the complex distribution of FOS. Topographical profiles crosscutting the northern, middle, and southern parts of the OT exhibit features that include: a single W-shape, a composite W-shape, and a U-shape, respectively, which suggests that in the middle and northern parts of the trough the central axial points are always located on seamount peaks or ridges associated with linear seamounts, whereas in the south they are found in the center of en echelon depressions. The line formed by the central axial points is the east-west dividing line of the OT, which indicates that the trough is a natural gap that prevents the extension of ECS continental shelf to the east. The distributions of the BOS and FOS lines are influenced by fluctuation of sea levels and submarine canyons, whereas the distribution of axis lines is controlled by tectonics and deposition.
基金This work was jointly funded by the National Natural Science Foundation of China(Grant Nos.42205168,41830967,and 42175163)the Youth Innovation Promotion Association CAS(2021073)the National Key Scientific and Technological Infrastructure project“Earth System Science Numerical Simulator Facility”(EarthLab).
文摘The soil freezing and thawing process affects soil physical properties,such as heat conductivity,heat capacity,and hydraulic conductivity in frozen ground regions,and further affects the processes of soil energy,hydrology,and carbon and nitrogen cycles.In this study,the calculation of freezing and thawing front parameterization was implemented into the earth system model of the Chinese Academy of Sciences(CAS-ESM)and its land component,the Common Land Model(CoLM),to investigate the dynamic change of freezing and thawing fronts and their effects.Our results showed that the developed models could reproduce the soil freezing and thawing process and the dynamic change of freezing and thawing fronts.The regionally averaged value of active layer thickness in the permafrost regions was 1.92 m,and the regionally averaged trend value was 0.35 cm yr–1.The regionally averaged value of maximum freezing depth in the seasonally frozen ground regions was 2.15 m,and the regionally averaged trend value was–0.48 cm yr–1.The active layer thickness increased while the maximum freezing depth decreased year by year.These results contribute to a better understanding of the freezing and thawing cycle process.
文摘Local scour around bridge piers and abutments is one of the most significant causes of bridge failure.Despite a plethora of studies on scour around individual bridge piers or abutments,few studies have focused on the joint impact of a pier and an abutment in proximity to one another on scour.This study conducted laboratory experiments and flow analyses to examine the interaction of piers and abutments and their effect on clear-water scour.The experiments were conducted in a rectangular laboratory flume.They included 18 main tests(with a combination of different types of piers and abutments)and five control tests(with individual piers or abutments).Three pier types(a rectangular pier with a rounded edge,a group of three cylindrical piers,and a single cylindrical pier)and two abutment types(a wingewall abutment and a semicircular abutment)were used.An acoustic Doppler velocimeter was used to measure the three-dimensional flow velocity for analyses of streamline,velocity magnitude,vertical velocity,and bed shear stress.The results showed that the velocity near the pier and abutment increased by up to 80%.The maximum scour depth around the abutment increased by up to 19%.In contrast,the maximum scour depth around the pier increased significantly by up to l71%.The presence of the pier in the vicinity of the abutment led to an increase in the scour hole volume by up to 87%relative to the case with a solitary abutment.Empirical equations were also derived to accurately estimate the maximum scour depth at the pier adjacent to the abutment.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA19070204)the National Natural Science Foundation of China(42071421).
文摘The thermal state of frozen ground and its changes are important for understanding environmental change and supporting related applications to the Earth’s Third Pole,which is a hotspot area for science research.However,challenges remain in data and modelling,meaning that much information is unavailable,especially for the entire Third Pole region.Here,we provided basic statistical data regarding the current state of frozen ground and its changes over the 1960s–2010s across the entire Third Pole by integrating nearly all currently available ground observation data and high-quality spatial data using machine learning models and existing high-quality frozen ground data products.The results show that the current(2000–2018)areal extents of permafrost and seasonally frozen ground in the Third Pole are approximately 1.27×10^(6)km^(2)(1.15×10^(6)to 1.39×10^(6)km^(2))and 2.59×10^(6)km^(2),accounting for 28%and 58%,respectively.The areal extent of permafrost region is approximately 50%(23%–93%)larger than that of permafrost area(land underlain by permafrost),especially in some early maps.The corresponding regional average of the mean annual ground temperature is approximately−1.51℃(−1.75 to−1.27℃)in the permafrost area.The regional average of active layer thickness overlying the permafrost and the maximum frost depth for regions of seasonally frozen ground are 235 cm(233–237 cm)and 92 cm,respectively.From the 1960s to the 2010s,on average,permafrost in the Third Pole warmed at a rate of 0.17℃per decade,which was associated with increases in the maximum thaw depth at a rate of 4.42 cm per decade.The regional average of the maximum frost depth declined at a rate of 2.34 cm per decade over the same period.This synthesis highlights the differences between the two terms(permafrost region and permafrost area)and provides crucial information for frozen ground in the Third Pole with higher accuracy for the scientific community and the public.
基金supported by Sinopec Research Institute of Petroleum Engineering,Beijing,Chinathe National Natural Science Foundation of China (Grant No. 51821092)+1 种基金the New Technology for Design and Control of Complex Well and Cluster Well (Grant No. 2017ZX05009-003)the Key Technology of Drilling Technology and Wellbore Working Fluid(Grant No. 2016YFC0303303)。
文摘How long the ultra deep well can extend and what is the ultra deep well's maximum hydraulic extension depth are always concerned and studied by drilling engineers. The well's maximum hydraulic extension depth can be predicted by the maximum hydraulic extension depth prediction model. To overcome the disadvantage that previous prediction model did not consider the effects of temperature and only applies to horizontal wells, a prediction model of maximum hydraulic extension depth for ultra deep wells considering effects of temperature is established. Considering the effects of temperature coupled with the constraints of drilling pump rated pressure and rated power, the prediction result of ultra deep well's maximum hydraulic extension depth is modified. An ultra deep well developed by Sinopec in Shunbei oilfield, China, is analyzed, and its wellbore temperature profile and maximum hydraulic extension depth are analyzed and predicted. Results show that the maximum hydraulic extension depth with considering temperature is larger than that without considering temperature. With the identical depth, the higher inlet temperature and the greater geothermal gradient mean the higher drilling fluid temperatures in the drill string and annulus as well as the larger maximum hydraulic extension depth. Besides, the maximum depth decreases with the increase in drilling fluid flow rate and density, while it increases with the increase in drilling pump rated pressure and rated power. To ensure the designed depth can be reached, there exists the maximum drilling fluid flow rate and density, as well as the minimum drilling pump rated pressure and rated power. This study is important for accurately predicting the ultra deep well's maximum depth within the limit capacity of drilling pump. In addition, it also plays a major role in avoiding drilling hazards.
文摘对埕岛油田已建成的水下基盘结构形式进行归纳总结,依据API RP 2A-WSD规范对井口基盘海洋环境荷载进行分析计算,基于SACS程序建立了9口井、12口井形式基盘的有限元计算模型,对水下基盘的适应水深进行静力分析,计算出了相应水深下结构的强度,确定水深变化对井口结构安全性的影响,得出了所研究井口基盘的极限水深。
