摘要：CO2 injection has been proposed as an efficient method for enhanced oil recovery in low‐permeability sandstone reservoirs. When CO2 is injected into such reservoirs, the petrophysical properties as well as the pore size distribution of tight formation can be altered due to the interactions between CO2 , water, and rock minerals. In this work, CO2 is introduced into the water‐saturated sandstone cores; nuclear magnetic resonance technique is then applied to obtain T 2 spectrum of the sandstone cores before and after CO2 injection. The effect of CO2 injection on the pore size distribution is analyzed by comparing the obtained T 2 spectrum. In addition, the change of petrophysical properties, that is, total porosity, porosity of the movable fluid, and permeability, are also discussed in this work. Test results show that after introducing CO2 , the total volume of small pores is significantly increased. On the contrary, the total volume of medium pores decreases. In addition, the immovable fluid porosity increases in the small pores, while it decreases in the medium pores after injecting CO2 . Based on the composition analysis, the concentration of the ions of Na + , K + , Ca 2+ , and Mg 2+ increases in the produced fluid due to the interactions between CO2 and albite, and potash feldspar. After CO2 injection, the total porosity, movable fluid porosity, and permeability of these tight cores are significantly improved. This study is expected to be significant for understanding the mechanisms of alterations of petrophysical properties and pore size distribution of tight sandstone cores due to the CO2 flooding.
关键词：CO2 injection;nuclear magnetic resonance technique;petrophysical properties;pore size distribution;tight sandstone
