摘要
盖层不封闭且胶结弱是海域天然气水合物储层开采面临的挑战之一。直接降压开采所得气水比低,还可能引发储层失稳。对此,一种基于水合物原理的储层改造方法被提出,即向水合物储层上方注入CO_(2)形成人工CO_(2)水合物盖层,从而构造出一个相对封闭的开采环境。在前期工作基础上,本文研究了注入CO_(2)+N_(2)混合气改造-开采CH_(4)水合物储层的可行性。研究结果表明注入混合气体能够形成渗透性低、稳定性好的CO_(2)水合物盖层,可以有效降低降压开采过程中的产水量及提高CH_(4)采收率。当注入的混合气中N_(2)比例较高时,过量的N_(2)对CH_(4)水合物的分解存在促进作用,但N_(2)随甲烷采出增加了后续的分离难度。当注入的混合气中CO_(2)的比例较高时,人工盖层阻水效果更强,但CO_(2)产出量也随之增加,且限制了CH_(4)采收率的进一步提高。后续研究需要进一步优化注-采工艺条件来提高开采效率和降低气体分离能耗。
It is a challenge for the exploitation of offshore gas hydrate reservoirs that the caprock is not closed and the cementation is weak.Direct depressurization always obtains high water yield and low gas to water ratios,which may also induce reservoir instability.Therefore,a reservoir reformation method based on hydrate principle was proposed,that is,CO_(2)was injected above the hydrate reservoir to form an artificial CO_(2)hydrate cap,so as to construct a relatively closed mining environment.Based on the previous works,this paper investigated the feasibility of injecting CO_(2)+N_(2)mixture to reform and exploit CH_(4)hydrate reservoir.Results show that a CO_(2)hydrate caprock with low permeability and good stability can form from the injected gas,which effectively reduces the water production and improves the recovery ratio of CH_(4)during depressurization.When the proportion of N_(2)in the injected is high,the presence of excess N_(2)can promote the decomposition of CH_(4)hydrate.However,N_(2)always is produced with CH_(4),increasing the difficulty of subsequent gas separation.When the proportion of CO_(2)in the injected gas is high,the water blocking effect of the formed artificial caprock is enhanced,but CO_(2)production also increases,and the further improvement of CH_(4)recovery is limited.The follow-up research needs to further optimize the injection-production process conditions to improve the production efficiency and reduce the energy consumption of gas separation.
作者
李楠
贾帅
孙振峰
孙长宇
陈光进
李璟明
LI Nan;JIA Shuai;SUN Zhenfeng;SUN Changyu;CHEN Guangjin;LI Jingming(Faculty of Engineering,China University of Petroleum-Beijing at Karamay,Karamay 834000,Xinjiang,China;State Key Laboratory of Heavy Oil Processing,China University of Petroleum,Beijing 102249,China)
出处
《化工进展》
EI
CAS
CSCD
北大核心
2022年第5期2356-2363,共8页
Chemical Industry and Engineering Progress
基金
新疆自治区“天山青年计划”项目(2019Q089)
新疆自治区教育厅高校科研计划(XJEDU2019Y069)。
关键词
甲烷水合物
二氧化碳
氮气
储层改造
降压开采
CH_(4)hydrate
carbon dioxide
nitrogen
reservoir reformation
depressurization
