Numerical studies of hydrate dissociation and gas production behavior in porous media during depressurization process

作     者：Xuke Ruan Mingjun Yang Yongchen Song Haifeng Liang Yanghui Li 

作者机构：Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of EducationDalian University of TechnologyDalian 116023LiaoningChina College of Chemistry and Chemical EngineeringTaiyuan University of TechnologyTaiyuan 030024ShanxiChina 

出 版 物：《Journal of Natural Gas Chemistry》 (天然气化学杂志（英文版）)

年 卷 期：2012年第21卷第4期

页      面：381-392页

核心收录：

学科分类：0820[工学-石油与天然气工程] 08[工学] 0824[工学-船舶与海洋工程] 082002[工学-油气田开发工程] 

基　　金：supported by the National Science and Technology Major Project,China (Grant No. 2011ZX05026-004-07) the National High Technology Research and Development Program of China (863 Program,Grant No. 2006AA09209-5) Major State Basic Research Development Program of China (973 Program,Grant No. 2009CB219507) 

主　　题：gas hydrate numerical simulation permeability dissociation gas production depressurization 

摘      要：In this study, a numerical model is developed to investigate the hydrate dissociation and gas production in porous media by depressurization. A series of simulation runs are conducted to study the impacts of permeability characteristics, including permeability reduction exponent, absolute permeability, hydrate accumulation habits and hydrate saturation, sand average grain size and irreducible water saturation. The effects of the distribution of hydrate in porous media are examined by adapting conceptual models of hydrate accumulation habits into simulations to govern the evolution of permeability with hydrate decomposition, which is also compared with the conventional reservoir permeability model, i.e. Corey model. The simulations show that the hydrate dissociation rate increases with the decrease of permeability reduction exponent, hydrate saturation and the sand average grain size. Compared with the conceptual models of hydrate accumulation habits, our simulations indicate that Corey model overpredicts the gas production and the performance of hydrate coating models is superior to that of hydrate filling models in gas production, which behavior does follow by the order of capillary coating〉pore coating〉pore filling〉capillary filling. From the analysis of tl/2, some interesting results are suggested as follows： （1） there is a ＂switch＂ value （the ＂switch＂ absolute permeability） for laboratory-scale hydrate dissociation in porous media, the absolute permeability has almost no influence on the gas production behavior when the permeability exceeds the ＂switch＂ value. In this study, the ＂switch＂ value of absolute permeability can be estimated to be between 10 and 50 md. （2） An optimum value of initial effective water saturation Sw,e exists where hydrate dissociation rate reaches the maximum and the optimum value largely coincides with the value of irreducible water saturation Swr,e. For the case of Sw,e〈,Swr,e, or Sw,e〉Swr,e, there are different control mechanisms domin