Open AccessInfluence of CO 2 injection on the pore size distribution and petrophysical properties of tight sandstone cores using nuclear magnetic resonance
Author(s) -
Zhao Jinsheng,
Wang Pengfei,
Zhang Yanming,
Ye Liang,
Shi Yu
Publication year - 2020
Publication title -
energy science and engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.638
H-Index - 29
ISSN - 2050-0505
DOI - 10.1002/ese3.663
Subject(s) - petrophysics , porosity , permeability (electromagnetism) , albite , feldspar , mineralogy , volume (thermodynamics) , geology , materials science , chemistry , composite material , geotechnical engineering , thermodynamics , membrane , biochemistry , quartz , physics
CO 2 injection has been proposed as an efficient method for enhanced oil recovery in low‐permeability sandstone reservoirs. When CO 2 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 CO 2 , water, and rock minerals. In this work, CO 2 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 CO 2 injection. The effect of CO 2 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 CO 2 , 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 CO 2 . 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 CO 2 and albite, and potash feldspar. After CO 2 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 CO 2 flooding.