柔性软管是海洋资源开发的关键性装备,在油气输送过程中,内管中的甲烷、二氧化碳、硫化氢、水蒸气等气体小分子可逐渐渗透内压密封层,严重危害软管服役安全。为保证软管安全稳定运行,探究甲烷渗透规律,对常温条件下高密度聚乙烯(High De...柔性软管是海洋资源开发的关键性装备,在油气输送过程中,内管中的甲烷、二氧化碳、硫化氢、水蒸气等气体小分子可逐渐渗透内压密封层,严重危害软管服役安全。为保证软管安全稳定运行,探究甲烷渗透规律,对常温条件下高密度聚乙烯(High Density Polyethylene,HDPE)原型软管进行了渗透试验。结果表明:(1)甲烷在HDPE管材中的渗透行为可大致分为溶解扩散期、缓慢解吸期及快速解吸期3个阶段,时间比例为1:6:5,第2阶段的均值气体透过率是第3阶段的1/3。(2)HDPE聚合物材料饱和溶解甲烷分子后,环空压力与气体透过率呈负指数函数关系。(3)发现了甲烷的超临界渗透特性,即试验压力在甲烷的临界压力附近时,气体透过率达到峰值;试验压力小于临界压力时,试验压力越大,气体透过率越大;反之,试验压力越大,气体透过率越小。研究成果可为柔性软管在海洋油气开发工程中的应用及新材料研发提供参考。(图7,表1,参20)展开更多
The study of formation and dissociation of CO 2 hydrate in porous media was characterized by magnetic resonance imaging (MRI) system in in situ conditions. This work simulated porous media by using glass beads of unif...The study of formation and dissociation of CO 2 hydrate in porous media was characterized by magnetic resonance imaging (MRI) system in in situ conditions. This work simulated porous media by using glass beads of uniform size. The growth and dissociation habit of CO2 hydrate was observed under different temperature and pressure conditions. The induction time and the hydrate saturation during the growth and dissociation process in different sizes of porous media were obtained by using the MRI signal intensity. The results indicate that hydrate growth rate and the induction time are affected by the size of porous media, pressure, and degree of supercooling. There are three hydrate growth stages, i.e., initial growth stage, rapid growth stage and steady stage. In this study,the CO2 hydrate forms preferentially at the surface of vessel and then gradually grows inward. The hydrate tends to cement the glass beads together and occupies the pore gradually. As the hydrate decomposes gradually, the dissociation rate increases to the maximum and then decreases to zero.展开更多
Gas hydrate decomposition in sediments involves complicated multiphase flow and heat and mass transfer processes because of heat absorption by solid hydrates. Factors affecting gas hydrate decomposition in sediments i...Gas hydrate decomposition in sediments involves complicated multiphase flow and heat and mass transfer processes because of heat absorption by solid hydrates. Factors affecting gas hydrate decomposition in sediments include sediment type, mineral composition, pore size distribution, particle size, pore water composition, hydrate saturation distribution, initial formation pressure and temperature and cement characteristics. In this paper, experimental simulations of gas hydrate decomposition are carried out on an artificial core to investigate the effects of initial pressure and temperature, particle size and pore size. The experiments show that the characteristics of gas hydrate decomposition in sediments differ completely from those in a pure water system. The decomposition rate of hydrate sediments increases with the initial pressure increasing and decreasing temperatures. Furthermore, the decomposition rate of hydrate sediments decreases with decreasing particle size and increasing pore size.展开更多
文摘柔性软管是海洋资源开发的关键性装备,在油气输送过程中,内管中的甲烷、二氧化碳、硫化氢、水蒸气等气体小分子可逐渐渗透内压密封层,严重危害软管服役安全。为保证软管安全稳定运行,探究甲烷渗透规律,对常温条件下高密度聚乙烯(High Density Polyethylene,HDPE)原型软管进行了渗透试验。结果表明:(1)甲烷在HDPE管材中的渗透行为可大致分为溶解扩散期、缓慢解吸期及快速解吸期3个阶段,时间比例为1:6:5,第2阶段的均值气体透过率是第3阶段的1/3。(2)HDPE聚合物材料饱和溶解甲烷分子后,环空压力与气体透过率呈负指数函数关系。(3)发现了甲烷的超临界渗透特性,即试验压力在甲烷的临界压力附近时,气体透过率达到峰值;试验压力小于临界压力时,试验压力越大,气体透过率越大;反之,试验压力越大,气体透过率越小。研究成果可为柔性软管在海洋油气开发工程中的应用及新材料研发提供参考。(图7,表1,参20)
基金supported by the State Key Development Program for Basic Research of China (Grant No. 2009CB219507)National Natural Science Foundation of China (Grant Nos. 51006017 & 50736001)National Science and Technology Major Project (Grant No. 2011ZX05026-004)
文摘The study of formation and dissociation of CO 2 hydrate in porous media was characterized by magnetic resonance imaging (MRI) system in in situ conditions. This work simulated porous media by using glass beads of uniform size. The growth and dissociation habit of CO2 hydrate was observed under different temperature and pressure conditions. The induction time and the hydrate saturation during the growth and dissociation process in different sizes of porous media were obtained by using the MRI signal intensity. The results indicate that hydrate growth rate and the induction time are affected by the size of porous media, pressure, and degree of supercooling. There are three hydrate growth stages, i.e., initial growth stage, rapid growth stage and steady stage. In this study,the CO2 hydrate forms preferentially at the surface of vessel and then gradually grows inward. The hydrate tends to cement the glass beads together and occupies the pore gradually. As the hydrate decomposes gradually, the dissociation rate increases to the maximum and then decreases to zero.
基金supported by the National Basic Research Program of China (Grant No. 2009CB219507)
文摘Gas hydrate decomposition in sediments involves complicated multiphase flow and heat and mass transfer processes because of heat absorption by solid hydrates. Factors affecting gas hydrate decomposition in sediments include sediment type, mineral composition, pore size distribution, particle size, pore water composition, hydrate saturation distribution, initial formation pressure and temperature and cement characteristics. In this paper, experimental simulations of gas hydrate decomposition are carried out on an artificial core to investigate the effects of initial pressure and temperature, particle size and pore size. The experiments show that the characteristics of gas hydrate decomposition in sediments differ completely from those in a pure water system. The decomposition rate of hydrate sediments increases with the initial pressure increasing and decreasing temperatures. Furthermore, the decomposition rate of hydrate sediments decreases with decreasing particle size and increasing pore size.
