封存过程中CO2流体与煤中矿物作用关系研究进展

利用深部煤层封存二氧化碳(CO2),既能减排主要人为温室气体CO2,又能同步开采煤层气(主要成分为甲烷,即CH4)。在适宜CO2封存的含煤储层条件下,CO2属于超临界流体,其易与煤中部分无机矿物发生作用,进而改变煤的理化性质,最终影响煤层的CO2封存效果。为此,归纳了煤中易与CO2发生作用的矿物分布特征,分析了CO2与矿物间的作用规律及其对煤理化性质的影响,并指出了后续研究方向。结果表明,煤中易与CO2流体发生作用的无机矿物主要包括碳酸盐矿物和黏土矿物。上述矿物的分布与煤变质程度和沉积环境有关。在封存过程中,超临界CO2流体与煤中矿物间的作用会改变煤体孔隙结构、煤的CO2吸附能力和含煤储层渗透率。针对CO2与煤中矿物的作用关系,后续需开展以下研究:CO2流体与煤中矿物之间的微观作用机理;CO2流体与煤层顶底板中主要无机矿物的作用规律;实际储层条件(温度、压力和地应力等)对CO2与矿物之间作用关系的影响;CO2与矿物之间的相互作用对同步采收CH4的影响。

Research review on the interaction of CO2 fluid with the minerals in the process of CO2 sequestration in coal seams

The given paper is aimed at making a research review on the interaction of CO2 fluid with minerals in the process of carbon dioxide(CO2)sequestration in the deep coal seams,which is a kind of viable option for storing the main anthropogenic greenhouse gas.Thus,CO2 is present as a kind of supercritical fluid,which is prone to interact with the inorganic minerals existing in coals via dissolution and precipitation effects.The aforementioned interacted products can help to change the physicochemical properties of coals and further affect CO2 sequestration in the target coal seams.Thus,the occurrence rule of minerals capable of interacting with CO2 in coals,the interactions between CO2 fluid and minerals and their further influence on CO2 sequestration are elucidated.Furthermore,the future trend is also pointed out.Specifically speaking,the carbonate mineral includes calcite and dolomite,whereas the clay mineral contains kaolinite,illite and chlorite.The appearance of the above-mentioned minerals should be highly dependent both on the coal rank and the sedimentary environment.As to CO2 sequestration in the deep coal seams,the interactions between the supercritical CO2 fluid and the minerals should be able to significantly affect the pore morphology,including the pore surface area,the pore volume and size,in addition to CO2 adsorption performance of the coal,as well as the permeability of the coal reservoirs.Therefore,in the future,further studies should also address the microscopic interaction between CO2 and minerals in coals,and that between CO2 and minerals in the roof and the floor of coal seams,the effects of the coal reservoir conditions,including the effects of the temperature,pressure and geostress on the interaction process between CO2 and minerals and their influences on the CH4 recovery.