化工进展 ›› 2022, Vol. 41 ›› Issue (5): 2356-2363.DOI: 10.16085/j.issn.1000-6613.2021-1895

• 能源加工与技术 • 上一篇    下一篇

注CO2+N2混合气改造-开采CH4水合物储层

李楠1,2(), 贾帅2, 孙振峰2, 孙长宇2, 陈光进2, 李璟明1()   

  1. 1.中国石油大学(北京)克拉玛依校区工学院,新疆 克拉玛依 834000
    2.中国石油大学(北京)重质油国家重点实验室,北京 102249
  • 收稿日期:2021-09-06 修回日期:2021-12-19 出版日期:2022-05-05 发布日期:2022-05-24
  • 通讯作者: 李璟明
  • 作者简介:李楠(1989—),男,副教授,研究方向为气体水合物开发与利用。E-mail:linan@cupk.edu.cn
  • 基金资助:
    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)

Exploitation of CH4 hydrate reservoir reformed by (CO2+N2) gas injection

LI Nan1,2(), JIA Shuai2, SUN Zhenfeng2, SUN Changyu2, CHEN Guangjin2, LI Jingming1()   

  1. 1.Faculty of Engineering, China University of Petroleum-Beijing at Karamay, Karamay 834000, Xinjiang, China
    2.State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, China
  • Received:2021-09-06 Revised:2021-12-19 Online:2022-05-05 Published:2022-05-24
  • Contact: LI Jingming

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CO2形成人工CO2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CO2+N2混合气改造-开采CH4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CO2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CH4采收率。当注入的混合气中N2比例较高时,过量的N2对CH4水合物的分解存在促进作用,但N2随甲烷采出增加了后续的分离难度。当注入的混合气中CO2的比例较高时,人工盖层阻水效果更强,但CO2产出量也随之增加,且限制了CH4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。

关键词: 甲烷水合物, 二氧化碳, 氮气, 储层改造, 降压开采

Abstract:

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, CO2 was injected above the hydrate reservoir to form an artificial CO2 hydrate cap, so as to construct a relatively closed mining environment. Based on the previous works, this paper investigated the feasibility of injecting CO2 + N2 mixture to reform and exploit CH4 hydrate reservoir. Results show that a CO2 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 CH4 during depressurization. When the proportion of N2 in the injected is high, the presence of excess N2 can promote the decomposition of CH4 hydrate. However, N2 always is produced with CH4, increasing the difficulty of subsequent gas separation. When the proportion of CO2 in the injected gas is high, the water blocking effect of the formed artificial caprock is enhanced, but CO2 production also increases, and the further improvement of CH4 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.

Key words: CH4 hydrate, carbon dioxide, nitrogen, reservoir reformation, depressurization

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