南堡凹陷CO_2在咸水层中的矿化封存机理

Experimental study on mineralization storage mechanism of CO_2 in saline aquifers of Nanpu depression

为了探讨CO2注入咸水层后岩石及流体的变化,应用研制的高压釜实验装置,模拟地层条件下(109℃、33.1MPa)饱和CO2地层水—岩石相互作用,证明CO2矿化封存的可行性,并分析超临界CO2注入后岩样中矿物的溶蚀、沉淀及溶液的变化原因.实验前后岩心质量、扫描电镜及溶液检测资料对比结果表明:超临界的CO2溶于水使咸水层酸性增强,然后与碎屑岩储层砂岩相互作用改变砂岩的矿物组成,生成固碳新矿物,从而实现CO2的永久封存;在CO2—水—岩石相互作用的过程中,砂岩中的长石、黏土等可溶矿物发生溶蚀,同时也生成方解石、菱镁矿和菱铁矿等固碳矿物及高岭石、绿泥石等非固碳矿物,其中固碳矿物的生成表明该储层CO2封存的可行性和稳定性;模拟超临界CO2注入后,短时间内岩石中的长石溶蚀和黏土矿物的溶解过程及新矿物的沉淀,为CO2在咸水层中的封存机制提供地球化学依据.

In order to explore the short term changes of rock and fluid in saline aquifers after the CO2 injection,the interaction process between CO2-saturated rocks and saline water was simulated in detail through the self designed autoclave experiment carried out under the simulated reservoir conditions(109℃and 33.1MPa).The feasibility of CO2 mineralization storage was proved and the mineral corrosion,precipitation and changes in solution and its reason were analyzed.Changes in mass loss,scanning electron microscopic and reaction solution detection showed that the solution of supercritical CO2 enhanced the acid to interact with the clastic rock and change the mineral composition to produce carbon sequestration new mineral and make CO2 permanently sealed.During the interaction of CO2-water-rock,the feldspar and clay mineral were dissolved and produced carbon sequestration mineral like calcite,magnesite and siderite,as well as none carbon sequestration mineral like kaolinite and chlorite.The generation of carbon sequestration indicated the feasibility and stability of CO2 geological storage.The experiment simulated the short term process of corrosion of feldspar and dissolution of clay minerals as well as precipitation of new minerals after supercritical CO2 injection,and provided geochemical evidence for CO2 trapping mechanisms underground.