中国海域盆地CO2地质封存选址方案与构造力学分析

本文围绕“碳达峰、碳中和”国家战略目标,从断裂活动、盆地压力、构造沉降特征、地震活动性和地温梯度等角度综合分析中国海域盆地适宜大规模CO₂地质封存的条件与目标,在宏观上认为东海陆架盆地、珠江口盆地、琼东南盆地东部以及南海中央海盆是最佳CO₂地质封存区域,但这并不排除其他盆地内部存在适宜的CO₂地质封存点,因为具体某个地质封存工程目标的范围相对较小.东海陆架盆地、珠江口盆地和琼东南盆地内适用于CO₂地质封存的地层包括盆地晚期快速沉降期沉积层的底部咸水层和热沉降沉积层内的含油气单元,在适宜的海底之下800～4000 m深度范围内,孔隙度大于10%,静水压力约在8～40 MPa之间、静岩压力约在13～83 MPa之间变化.在此压力范围和合适的地温梯度范围内, CO₂以超临界状态存在,其密度随温压变化相对稳定,有利于CO₂的流动和渗透.另外,盆地内的基性岩浆岩建造的规模和数量也为CO₂地质封存和永久矿化提供了很好的条件.虽然工程难度大和代价高...

STRATEGIC AND GEODYNAMIC ANALYSES OF GEO-SEQUESTRATION OF CO2 IN CHINA OFFSHORE SEDIMENTARY BASINS

Focusing on the national strategic goal of "Carbon Peaking and Carbon Neutrality", this paper comprehensively analyzes the strategic conditions and targets suitable for large-scale CO₂ geo-storage in the China offshore basins, from the perspectives of fault activity, basin pressure, tectonic subsidence, seismicity, and geothermal gradient. It is considered that the East China Sea Shelf Basin, Pearl River Mouth Basin, eastern Qiongdongnan Basin, and the central South China Sea basin are the best geological storage areas for CO₂, although this does not exclude suitable targets in other unfavorable sedimentary basins since a specific geo-sequestration target is small in area. The suitable CO₂ storage strata in the East China Sea Shelf, Pearl River Mouth, and Qiongdongnan Basins include the bottom salt-water layer of the late rapid subsidence sediments in the open-sea environment and the hydrocarbon-bearing units in the thermal subsidence sedimentary sequences. Between 800 and 4000 m depths beneath the seafloor, the porosity is greater than 10%, and the hydrostatic and lithostatic pressures vary from ~ 8 to ~ 40 MPa and from ~ 13 to ~ 83 MPa, respectively. In this pressure and suitable geothermal gradient ranges, CO₂ exists in a supercritical state, and its density is relatively stable with temperature and pressure changes, which is beneficial to the flow and permeation of CO₂. The scale and number of mafic magmatic rock formations in the basins also provide good conditions for CO₂ geological sequestration and permanent mineralization. Although operationally difficult and expensive, CO₂ storage in the central South China Sea basin is very safe. CO₂ injected deep into the oceanic basalt can undergo basalt mineralization, but if CO₂ is escaped as the mineralization process is relatively slow, escaped CO₂ can be further trapped by multiple other storage processes, including pyroclastic rock mineralization, seafloor sediment sequestration, seabed sediment CO₂ hydrate storage, carbonate neutralization reaction, seabed carbon lake, ocean dissolution, etc. The existing six International Oceanic Discovery Program (IODP) boreholes that have encountered basement basalt in the central basin of the South China Sea can provide a good scientific and engineering foundation for the pilot CO₂ storage experiment in the South China Sea basin.