超临界CO_2注入煤岩地球化学效应研究评述

Study and review on geochemical effect of coal and rock injected with super-critical CO_2

综合国内外超临界CO_2(称scCO_2)注入煤层的试验研究及理论分析,发现scCO_2注入煤储层后必对其物质组成、物理结构产生影响,进而重塑其孔裂隙系统,主要原因是scCO_2-H_2O分别与煤中矿物和煤基质发生地球化学反应。在scCO_2-H_2O-煤岩反应体系中,煤中的矿物会发生溶解—沉淀,其中最敏感的是碳酸盐矿物,其次是长石和黏土矿物,而硫化物矿物(黄铁矿)与石英则相对稳定;scCO_2对煤基质中的小分子有一定萃取作用,进而改变煤大分子结构。影响scCO_2-H_2O-煤岩反应的主要因素有煤中矿物成分、煤岩组分与煤阶、煤储层压力与地温条件以及地层水的矿化度等。由于试验模拟与数值模拟的局限性,对于scCO_2-H_2O-煤岩地球化学响应机制有待深入探索,同时对煤岩孔裂隙网络变化的实时观测与定位研究更为重要。

Based on the comprehensive experiment study and the theoretical analysis on the super-critical CO_2 injection in the seam at home and abroad,it was found that the super-critical CO_2 injection in the seam would be affected to the material composition and the physical structure and could reconstruct the pore cracking system.The major causes could be that the super-critical CO_2 injection individually would have the geochemical reaction with the minerals in the coal and the coal matrix.In the reaction system of the super-critical CO_2 injection-H_2O-coal and rock,the minerals in the coal would have erosion dissolution-sediment. Among them,the most sensitivity would be the carbonate minerals and then would be the feldspar and clay mineral.The sulfide mineral（ pyrites） and quartz would be stable relatively.The super-critical CO_2 injection would have a certain extraction role to the small molecule in the coal matrix and thus could change the molecular structure of the coal.The major factors affected to the super-critical CO_2 injection-H_2O-coal and rock reaction would be the coal mineral composition,macerals and coal grade,coal reservoir pressure and ground temperature condition as well as the formation water salinity and others.Due to the limitation of the test simulation and numerical simulation,the response mechanism of the super-critical CO_2 injection-H_2O-coal and rock geochemistry would be needed to be discussed in detail and meanwhile a real time observation and position study on the pore cracking network variation of the coal and rock would be more important.