CO2 sequestration with limited sealing capability: A new injection and storage strategy in the Pearl River Mouth Basin (China)

Storing CO2 for geological timescales is crucial to delivering decarbonisation of industrial economies aligned with global climate change mitigation objectives. This requires CO2 injection into a large subsurface pore space overlain by a high capillary entry pressure seal rock to prevent CO2 escape. Such formations occur abundantly in productive hydrocarbon basins such as the North Sea. However, these geological conditions for CO2 storage are unavailable close to some large CO2 emitting economic areas in China. We identify this problem and innovate a solution for the example of the Pearl River Mouth Basin (China). This offshore basin has an estimated effective storage capacity of hundreds of Gt CO2 based on reservoir pore volumes. Production and geological data of three oil fields of the Huizhou hydrocarbon cluster are analysed as analogues for large-scale aquifer storage of CO2. Results suggest the injection and storage of CO2 in individual trap structures will perform poorly, due to thin reservoir layers, small structural traps, and indications that the cap rocks may have only limited sealing capability. To address this a novel alternative CO2 sequestration strategy, based on multi reservoir layer injection and dispersion trapping, is recommended to exploit the vast available pore space for CO2 storage.