多孔介质中不同饱和度天然气水合物的分解特性研究  

Study on the decomposition characteristics of natural gas hydrate formed in porous media with different saturations

作　　者：谢崇宏 钟栋梁[1] 李明伟[2] XIE Chonghong;ZHONG Dongliang;LI Mingwei(State Key Laboratory of Coal Mine Disaster Dynamics and Control,Chongqing University,Chongqing,China;School of Energy and Power Engineering,Chongqing University,Chongqing,China)

机构地区：[1]煤矿灾害动力学与控制国家重点实验室,重庆大学,重庆400044 [2]重庆大学能源与动力工程学院,重庆400044

出　　处：《海洋地质前沿》2022年第3期19-26,共8页Marine Geology Frontiers

基　　金：国家自然科学基金(52076019);教育部创新团队项目(IRT_17R112)。

摘　　要：开采天然气水合物对缓解世界能源危机、解决中国天然气资源短缺问题具有重要现实意义。降压法是开采天然气水合物一种较为简单、安全、有效的方法,但是目前对水合物饱和度较高条件下的降压分解特性缺乏深入认识。在多孔介质(石英砂)体系开展了天然气水合物的生成与分解实验,研究了3种不同水合物饱和度(38.1%、42.1%、46.4%)条件下的水合物降压分解特性,分解压力分别为2 MPa和3 MPa。实验结果表明:2 MPa对应的产气速率较高,但是模拟储层温度会降至冰点以下,在实际水合物开采中会引起冰堵,阻碍水合物进一步分解。当分解压力为3 MPa时,在0~2 h内,随着水合物饱和度增加,产气速率减小;从2 h到水合物分解结束,水合物饱和度越高,产气速率越高;在降压阶段,不同饱和度水合物的储层温度(T_(1)、T_(2)、T_(3))快速下降且最低温度相似;在恒压阶段,不同饱和度水合物的储层温度开始回升,水合物饱和度越高,储层温度波动越大,并且恢复至实验设定温度需要的时间越长。研究结果将为水合物试采过程防止冰堵现象发生、提高气体回收率提供重要的理论参考。The exploitation of natural gas hydrate(NGH)is of great significance to alleviate the world energy crisis and solve the problem of natural gas resource shortage in China.Facts prove that depressurization method is a relatively simple,safe,and effective method for the exploitation of natural gas hydrates.However,there is a lack of in-depth understanding of the decomposition characteristics of hydrates with high hydrate saturation under depressurization.Therefore,the formation and decomposition experiments of NGH were carried out in the porous medium(quartz sand)system.The decomposed characteristics of NGH under three different saturation conditions(38.1%,42.1%,46.4%)were studied,and the decomposition pressures were 2 MPa and 3 MPa,respectively.The results show that the hydrate decomposition rate is quite high corresponding to 2 MPa,and the simulated reservoir temperature drops below the freezing point,that will cause ice blocking to stop further decomposition of hydrate in the actual production of NGH.When the decomposition pressure is 3 MPa,from 0 h to 2 h,the gas production rate decreases with the increase in hydrate saturation,and from 2 h to the end of the experiment,the gas production rate increases with the increase of hydrate saturation.In the depressuring stage,the reservoir temperature(T_(1),T_(2),T_(3))of NGH with different saturations drops rapidly to a similar minimum.In the constant pressure stage,the reservoir temperature of NGH with different saturations recovers to rise.The higher the saturation,the greater the reservoir temperature fluctuation and longer the time to return to the experimental temperature.In order to achieve high-efficiency exploitation,measures have to be taken to prevent ice blocking.The hydrate decomposition pressure should be set at 3 MPa,and the reservoir with a high hydrate saturation should be set for a longer decomposition time to increase CH4 recovery rate and ensure the efficiency of exploitation.

关 键 词：天然气水合物 非常规天然气 多孔介质 降压分解 水合物饱和度 

分 类 号：TE3[石油与天然气工程—油气田开发工程]