Securing offshore resources development:A mathematical investigation into gas leakage in long-distance flexible pipes  

作　　者：Xiang-An Lu Liang-Liang Jiang Jian-Sheng Zhang Min-Gui Wang 

机构地区：[1]Guangling College of Yangzhou University,Yangzhou,225131,Jiangsu,China [2]Department of Chemical and Petroleum Engineering,University of Calgary,Calgary,T2N 1N4,Alberta,Canada [3]Department of Energy and Power Engineering,Tsinghua University,Beijing,100084,China

出　　处：《Petroleum Science》2024年第4期2734-2744,共11页石油科学（英文版）

基　　金：supported by the Natural Science Research Project of Guangling College of Yangzhou University,China (ZKZD18004);General Program of Natural Science Research in Higher Education Institutions of Jiangsu Province,China (20KJD430006)。

摘　　要：Gas flexible pipes are critical multi-layered equipment for offshore oil and gas development.Under high pressure conditions,small molecular components of natural gas dissolve into the polymer inner liner of the flexible pipes and further diffuse into the annular space,incurring annular pressure build-up and/or production of acidic environment,which poses serious challenges to the structure and integrity of the flexible pipes.Gas permeation in pipes is a complex phenomenon governed by various factors such as internal pressure and temperature,annular structure,external temperature.In a long-distance gas flexible pipe,moreover,gas permeation exhibits non-uniform features,and the gas permeated into the annular space flows along the metal gap.To assess the complex gas transport behavior in long-distance gas flexible pipes,a mathematical model is established in this paper considering the multiphase flow phenomena inside the flexible pipes,the diffusion of gas in the inner liner,and the gas seepage in the annular space under varying permeable properties of the annulus.In addition,the effect of a variable temperature is accounted.A numerical calculation method is accordingly constructed to solve the coupling mathematical equations.The annular permeability was shown to significantly influence the distribution of annular pressure.As permeability increases,the annular pressure tends to become more uniform,and the annular pressure at the wellhead rises more rapidly.After annular pressure relief followed by shut-in,the pressure increase follows a convex function.By simulating the pressure recovery pattern after pressure relief and comparing it with test results,we deduce that the annular permeability lies between 123 and 512 m D.The results help shed light upon assessing the annular pressure in long distance gas flexible pipes and thus ensure the security of gas transport in the emerging development of offshore resources.

关 键 词：Offshore resources development Transport security Long-distance flexible pipes Gas leakage Heat and mass transfer model Finite difference calculation 

分 类 号：TE973[石油与天然气工程—石油机械设备]