新一代海域天然气水合物开采、固碳和地质修复三联开采技术

A new generation of triple mining technology of production,carbon sequestration,and geological restoration for natural gas hydrates in sea areas

海域中的天然气水合物(水合物)是储量巨大的清洁能源,可满足国家和地区能源和经济发展的重大需求。海域水合物藏的温度和压力条件(12~16℃)较高,呈泥质低渗,开发难度大,需要将常规的降压、注热/抑制剂和CO_(2)置换等开采方法进行联合并协同优化,以形成适合在海域特殊地质环境下水合物资源安全高效的开采技术。通过梳理目前已有的天然气水合物联合开采技术研究进展,按照“安全开采、绿色高效”的思路,以提高天然气采收率、CO_(2)温室气体封存效率以及修复水合物储层为目标,将降压与CO_(2)注入相结合,提出新一代海域天然气水合物开采、固碳和地质修复三联开采技术,即先采用降压法开采水合物,后注入CO_(2)混合气辅助刺激水合物开采并驱替天然气提高采收率,最后注入高压高CO_(2)组分混合气在孔隙中重新形成混合水合物,从而达到能源开采、碳封存和地层修复的目的。进一步通过分析该新技术提出的背景、技术原理、热动力学可行性分析、中小尺度试验验证结果以及未来发展方向等,以期为海域天然气水合物开采提供借鉴。

Natural gas hydrates in sea areas are clean energy with abundant reserves,which can meet the great demands from national and regional energy and economic development.Hydrate reservoirs in the sea areas occur under high temperature and pressure conditions(12℃-16℃),low argillaceous permeability,leading to a great difficulty in hydrocarbon development.Conventional mining methods such as depressurization,heat/inhibitor injection,and carbon dioxide replacement should be integrated and collaboratively optimized to form the safe and efficient exploitation technologies for natural gas hydrate resources in special geological environments in sea areas.By introducing the current research progress of existing combined mining technologies for natural gas hydrates,in accordance with the idea of“safe mining,being green and efficient”,with the goal of improving natural gas recovery efficiency and CO_(2) storage efficiency,and remediating hydrate reservoirs,a new generation of triple mining technology of production,carbon sequestration,and geological restoration for natural gas hydrates in sea areas is proposed by combining depressurization and CO_(2) injection.Specifically,hydrates are exploited by depressurization method at first,then CO_(2) mixture is injected to assist in stimulating hydrate production and displacing natural gas to improve recovery efficiency,and finally the high-pressure and high CO_(2) component gas mixture is injected to re-form mixed hydrates in the pores.This aims to achieve energy exploitation,carbon storage,and formation remediation.The paper elaborates the background,technical principle,thermodynamic feasibility analysis,verification results of medium-and small-scale tests,and future development direction of the new technology,aiming to provide reference for the production of natural gas hydrates in sea areas.