Abstract: Huge natural gas reserves was proven in China, but its long-term stable production faces a series of challenges owing to unknown technologies to dramatically improve the recovery factor of complicated gas reservoirs. The main mechanisms for CO2 flooding to improve the gas recovery (EGR) from gas reservoirs include gas reservoir energy supplement, substitution of dominant CO2 absorption, continuous convective displacement and gravity differentiation. Research on CCUS (carbon capture, utilization and storage) is of great importance to maximizing hydrocarbon gas recovery, using deep geological space for gas storage and reducing carbon emission on a large scale. Under the background of carbon neutrality, the CCUS-EGR technology has a broad prospect for application. After nearly 20 years of CCUS-EOR technology research, key engineering technologies, such as carbon capture, CO2 flooding injection and production, CO2 flooding fluid gathering and processing, and long-distance CO2 pipeline construction have matured, thus providing the necessary technical conditions for carrying out the full-process CCUS-EGR development experiments. At present, the key task of CCUS-EGR research is to verify the actual technical effect of CO2 flooding, identify the laws for CO2 flooding development of gas reservoirs, and establish an extensively-adapted CO2 flooding engineering method for gas reservoirs. To make a breakthrough in PetroChina’s CCUS-EGR technology, it is proposed to carry out major CCUS-EGR development experiments on a variety of gas reservoirs with good seal and storage conditions, such as gas reservoirs of special lithological characters, tight sandstone gas reservoirs, volcanic rock gas reservoirs, shale gas reservoirs and coal rock gas reservoirs, thus developing the theory and technology concerning aggressive improvement of gas recovery factor and carbon storage in gas reservoirs by CO2 flooding. Of those technologies, the experiments should be focused on testing the synergistic displacement effect of flue gas components and verifying the technology of expanding the CO2 sweeping volume, while the key theoretical research should be focused on establishing a perfect prediction method for CO2 emergence time and improving the calculation methods for the key production indicators like natural gas recovery factor and establishing the accounting methods for CCUS-EGR reduction of carbon emission.

Key words: CO2 displacing gas mechanism, aggressively improve recovery factor of gas reservoirs, carbon storage, CCUSEGR, major development experiments

摘要： 中国天然气探明储量巨大，但其长期规模稳产面临复杂气藏大幅度提高采收率技术不明等系列挑战。补充气藏能量、优势吸附置换、连续对流排驱和重力分异作用是CO2驱提高气藏采收率的主要机理；开展CCUS-EGR（碳捕集、驱气利用与埋存）工作对于烃类气的最大化采出、深部储气地质空间的利用和规模碳减排意义重大。碳中和背景下，CCUS-EGR技术具有广阔应用前景。经过近20年CCUS-EOR技术攻关研究，碳捕集、CO2驱注采、CO2驱流体集输与处理、长距离CO2管道建设等关键性硬工程技术已经成熟配套，为成功开展全流程CCUS-EGR重大开发试验提供了必要技术条件；当前，CCUS-EGR技术研究核心任务是检验CO2驱气实际技术效果，认识CO2驱气开发规律，建立普适性CO2驱气藏工程方法。为突破中国石油CCUS-EGR 技术，建议针对具有较好碳封存条件的特殊岩性气藏、致密砂岩气藏、火山岩气藏、页岩气藏和煤岩气藏，开展多类型气藏CCUS-EGR 重大开发试验，形成CO2驱进攻性提高气藏采收率与储碳科学理论与技术；其中，检验烟气组分协同驱替效果和验证扩大CO2驱气波及体积技术是两大试验内容，建立完善CO2驱见气时间预报方法、提高天然气采收率值等关键生产指标计算方法和CCUSEGR碳减排量核算方法是重点研究内容。

关键词: CO2驱气机理, 进攻性提高气藏采收率, 储碳, CCUS-EGR, 重大开发试验