Zhun Zhang , Fulong Ning , Wanjun Lu , Jiazuo Zhou , Lele Liu , Yunkai Ji , Changfu Wei , Changling Liu
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引用次数: 1
Abstract
Water retention curves play a critical role in numerical simulations for predicting fluid production and sediment deformation behaviors in gas hydrate-bearing sediments (GHBSs). This study uses a new testing assembly that combines gas drainage and low-field nuclear magnetic resonance (NMR) tests to determine the water retention curves of artificially synthesized clay silty specimens. The effect of hydrate on the pore size distributions and water retention curves is analyzed via NMR transverse relaxation time curve distributions, and the mechanism of changes in the water retention curve parameters is further discussed. The results show that hydrate formation decreases the proportion of pores with sizes greater than 15 μm and increases the proportion of pores with sizes less than 3.5 μm in clay silty sediments. Hydrate formation increases capillary pressure and prevents available water migration. The presence of hydrate exponentially increases the normalized capillary pressure but exponentially decreases the normalized curve shape factor, yielding narrower curve distributions. The gas entry pressure and curve shape factor exhibit linear correlations with the pore size distribution parameters. The results imply that the changes in the water retention curves are strongly related to the initial pore size distributions. This study offers a deep understanding of capillary effects-related water retention characteristics and their underlying links with the pore size distributions, and demonstrates that low-field NMR has great potential for characterizing water retention curves of GHBSs.
期刊介绍:
The objective of the Journal of Natural Gas Science & Engineering is to bridge the gap between the engineering and the science of natural gas by publishing explicitly written articles intelligible to scientists and engineers working in any field of natural gas science and engineering from the reservoir to the market.
An attempt is made in all issues to balance the subject matter and to appeal to a broad readership. The Journal of Natural Gas Science & Engineering covers the fields of natural gas exploration, production, processing and transmission in its broadest possible sense. Topics include: origin and accumulation of natural gas; natural gas geochemistry; gas-reservoir engineering; well logging, testing and evaluation; mathematical modelling; enhanced gas recovery; thermodynamics and phase behaviour, gas-reservoir modelling and simulation; natural gas production engineering; primary and enhanced production from unconventional gas resources, subsurface issues related to coalbed methane, tight gas, shale gas, and hydrate production, formation evaluation; exploration methods, multiphase flow and flow assurance issues, novel processing (e.g., subsea) techniques, raw gas transmission methods, gas processing/LNG technologies, sales gas transmission and storage. The Journal of Natural Gas Science & Engineering will also focus on economical, environmental, management and safety issues related to natural gas production, processing and transportation.