双水平井连续注混合气吹扫—置换开采天然气水合物研究
Research on natural gas hydrate exploitation by mixed gas sweeping-replacement from dual horizontal wells
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- 引用格式:
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李中,庞维新.双水平井连续注混合气吹扫—置换开采天然气水合物研究[J].天然气与石油,2024,42(6):11-24.doi:10.3969/j.issn.1006-5539.2024.06.002
LI Zhong, PANG Weixin.Research on natural gas hydrate exploitation by mixed gas sweeping-replacement from dual horizontal wells[J].Natural Gas and Oil,2024,42(6):11-24.doi:10.3969/j.issn.1006-5539.2024.06.002
- DOI:
- 10.3969/j.issn.1006-5539.2024.06.002
- 作者:
- 李中1,2 庞维新1,2
LI Zhong1,2, PANG Weixin1,2
- 作者单位:
- 1. 海洋天然气水合物全国重点实验室, 北京 100028; 2. 中海油研究总院有限责任公司, 北京 100028
1. State Key Laboratory of Offshore Natural Gas Hydrates, Beijing, 100028, China; 2. CNOOC Research Institute Co., Ltd., Beijing, 100028, China
- 关键词:
- 天然气水合物开采;吹扫—置换;混合气注入;水平井;CH4采收率;CO2封存率
Natural gas hydrate exploitation; Sweeping-replacement; Mixed gas injection; Horizontal well; CH4 recovery rate; CO2 sequestration rate
- 摘要:
注CO2混合气开采天然气水合物兼具CH4采收,CO2原位封存和稳固储层的三重优势,已成为水合物开发技术的主要研究方向之一。首次利用中型三维反应器构建了双水平井注气开采水合物模拟场景,以此考察了CO2/N2和CO2/H2这2种混合气体系在吹扫—置换双原理驱动下的CH4采收和CO2封存效果。研究结果表明:降低注入气中CO2含量,能够提高CH4采收率,但同时会降低CO2封存率；当注入气CO2摩尔浓度大于54%时,相比CO2/N2,采用CO2/H2的CH4采收率提升12%~16%,但CO2封存率下降8%~17%；当注入气CO2摩尔浓度为33%时,CO2/H2和CO2/N2气体扩散路径出现显著差异,CO2/H2易集中向上扩散,存在较大泄漏风险,且注采前期CH4采收速率和采出浓度较CO2/N2更低。此外,基于净CH4采收率对2种混合气体系开采天然气水合物进行了经济性分析,为置换法开采天然气水合物提供了参考。
The injection of CO2-containing gas mixture has emerged as one of the main research directions in hydrate exploitation due to its triple advantages of high methane recovery, long-term CO2 storage and reservoir geo-mechanical stability, showing tremendous potential for future application. This study, for the first time, utilized a medium-sized three-dimensional reactor to develop a production simulation scenario for gas injection exploitation of hydrates via dual horizontal wells, to examine the CH4 recovery and CO2 sequestration effects of CO2/N2 and CO2/H2 injection under the dual principles of sweeping and replacement. The results indicate that reducing the CO2 content in the injected gas can increase CH4 recovery rate, while simultaneously decreasing CO2 sequestration rate. When the CO2 concentration exceeds 54% mole, compared to CO2/N2 system, using CO2/H2 can increase CH4 recovery rate by 12%~16%, but decrease CO2 sequestration rate by 8%~17%. When the CO2 concentration in the injected gas is 33% mole, there is a significant difference in the gas diffusion paths for CO2/H2 and CO2/N2. CO2/H2 tends to diffuse upward, posing a greater leakage risk and resulting in a lower CH4 recovery rate and concentration in produced gas during the early production stage. Additionally, an economic analysis for the two mixed gas systems is conducted based on the net CH4 recovery, providing reference for natural gas hydrates exploitation using replacement method.
