A novel expandable conductor was designed and applied in deep-water drilling to improve the vertical and lateral bearing capacity with a significant reduction of conductor jetting depth and soaking time. The vertical ...A novel expandable conductor was designed and applied in deep-water drilling to improve the vertical and lateral bearing capacity with a significant reduction of conductor jetting depth and soaking time. The vertical and lateral bearing capability of expandable conductors was depicted based on the ultimate subgrade reaction method and pile foundation bearing theory. The load-bearing characteristics of a laboratory-scale expandable conductor were analyzed through laboratory experiments. The serial simulation experiments are accomplished to study the bearing characteristics(vertical ultimate bearing capacity, lateral soil pressure, and lateral displacement) during the conductor soaking process. The laboratory experimental results show that the larger the length and thickness of expandable materials are,the higher the bearing capacity of the wellhead will be. During the conductor soaking process, the soil pressure around the three expandable conductors increases faster, strings representing a stronger squeezing effect and resulting in higher vertical bearing capacity. Furthermore, the lateral displacement of novel expandable conductor is smaller than that of the conventional conductor. All the advantages mentioned above contributed to the reduction of conductor’s jetting depth and soaking time. Lastly, the application workflow of a novel expandable deep-water drilling conductor was established and the autonomous expandable conductor was successfully applied in the South China Sea with a significant reduction of conductor’s jetting depth and soaking time. According to the soil properties and designed installation depth of the surface conductor, the arrangement of expandable materials should be designed reasonably to meet the safety condition and reduce the construction cost of the subsea wellhead.展开更多
As the transmission line corridors become more and more rare in China,it is now inevitable for people to construct HVAC-HVDC hybrid transmission lines.The research on the electric field around the transmission lines p...As the transmission line corridors become more and more rare in China,it is now inevitable for people to construct HVAC-HVDC hybrid transmission lines.The research on the electric field around the transmission lines plays an important role in evaluating the electromagnetic environment nearby.However,few existing research now considered the mutual effect of HVAC-HVDC hybrid transmission lines.Thus,this research designed a program based on windows,which calculated the surface voltage gradient on the transmission lines and the electric field at ground level respectively.This research calculated the surface voltage gradient on the transmission lines by applying the improved method of successive images.For the electric field at ground level under AC transmission line,simulation charge method is used,while for the electric field at the ground level under DC transmission lines,deutsch assumption method is used.Comparing the results generated by the calculation with those in published literature,the program is reliable.Taking 500 kV transmission lines as an example,when considering the mutual effect of the HVAC-HVDC lines,the amplitude of the surface voltage gradient will increase by about 10%and the amplitude of the electric field at ground level will increase by about 8%,making the mutual effect of the AC and DC lines unneglectable. Larger part of the electric field at ground level under hybrid lines is produced by the DC line.Thus,in order to control the electric field at ground level under hybrid lines,it should pay more attention on that produced by the DC line.展开更多
基金financially supported by the National Natural Science Foundation of China (Grant Nos.51434009 and 51221003)。
文摘A novel expandable conductor was designed and applied in deep-water drilling to improve the vertical and lateral bearing capacity with a significant reduction of conductor jetting depth and soaking time. The vertical and lateral bearing capability of expandable conductors was depicted based on the ultimate subgrade reaction method and pile foundation bearing theory. The load-bearing characteristics of a laboratory-scale expandable conductor were analyzed through laboratory experiments. The serial simulation experiments are accomplished to study the bearing characteristics(vertical ultimate bearing capacity, lateral soil pressure, and lateral displacement) during the conductor soaking process. The laboratory experimental results show that the larger the length and thickness of expandable materials are,the higher the bearing capacity of the wellhead will be. During the conductor soaking process, the soil pressure around the three expandable conductors increases faster, strings representing a stronger squeezing effect and resulting in higher vertical bearing capacity. Furthermore, the lateral displacement of novel expandable conductor is smaller than that of the conventional conductor. All the advantages mentioned above contributed to the reduction of conductor’s jetting depth and soaking time. Lastly, the application workflow of a novel expandable deep-water drilling conductor was established and the autonomous expandable conductor was successfully applied in the South China Sea with a significant reduction of conductor’s jetting depth and soaking time. According to the soil properties and designed installation depth of the surface conductor, the arrangement of expandable materials should be designed reasonably to meet the safety condition and reduce the construction cost of the subsea wellhead.
文摘As the transmission line corridors become more and more rare in China,it is now inevitable for people to construct HVAC-HVDC hybrid transmission lines.The research on the electric field around the transmission lines plays an important role in evaluating the electromagnetic environment nearby.However,few existing research now considered the mutual effect of HVAC-HVDC hybrid transmission lines.Thus,this research designed a program based on windows,which calculated the surface voltage gradient on the transmission lines and the electric field at ground level respectively.This research calculated the surface voltage gradient on the transmission lines by applying the improved method of successive images.For the electric field at ground level under AC transmission line,simulation charge method is used,while for the electric field at the ground level under DC transmission lines,deutsch assumption method is used.Comparing the results generated by the calculation with those in published literature,the program is reliable.Taking 500 kV transmission lines as an example,when considering the mutual effect of the HVAC-HVDC lines,the amplitude of the surface voltage gradient will increase by about 10%and the amplitude of the electric field at ground level will increase by about 8%,making the mutual effect of the AC and DC lines unneglectable. Larger part of the electric field at ground level under hybrid lines is produced by the DC line.Thus,in order to control the electric field at ground level under hybrid lines,it should pay more attention on that produced by the DC line.
