Influence of CO2 injection on the pore size distribution and petrophysical properties of tight sandstone cores using nuclear magnetic resonance,Energy Science & Engineering

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Influence of CO2 injection on the pore size distribution and petrophysical properties of tight sandstone cores using nuclear magnetic resonance
Energy Science & Engineering ( IF 3.5 ) Pub Date : 2020-03-06 , DOI: 10.1002/ese3.663
Jinsheng Zhao _{1,

2} , Pengfei Wang _{1,

2} , Yanming Zhang _{3,

4} , Liang Ye _{3,

4} , Yu Shi _{1,

2}

Affiliation

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 T₂ 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 T₂ 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⁺, Ca²⁺, and Mg²⁺ 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.

中文翻译：

核磁共振注CO2对致密砂岩岩心孔径分布和岩石物性的影响

有人建议采用CO ₂注入作为提高低渗透率砂岩油藏采收率的有效方法。当将CO ₂注入这样的储层中时，由于CO ₂，水和岩石矿物之间的相互作用，可以改变岩石的物性以及致密地层的孔径分布。在这项工作中，CO ₂被引入到水饱和的砂岩岩心中。然后应用核磁共振技术获得CO ₂注入前后砂岩岩心的T ₂光谱。通过比较获得的T分析CO ₂注入对孔径分布的影响₂光谱。此外，在这项工作中还讨论了岩石物理性质的变化，即总孔隙度，活动流体的孔隙度和渗透率。试验结果表明，引入CO _2后，小孔的总体积显着增加。相反，中孔的总体积减少。另外，注入CO ₂后，不可移动的流体孔隙率在小孔中增加，而在中孔中降低。基于组成分析，由于CO ₂之间的相互作用，产出液中Na ⁺，K ⁺，Ca ²⁺和Mg ²⁺的离子浓度增加。钠长石和钾长石。注入CO ₂后，这些致密岩心的总孔隙率，活动流体孔隙率和渗透率得到了显着改善。预期该研究对于理解由于CO ₂驱替导致的岩石物理性质和致密砂岩岩心的孔径分布变化的机制具有重要意义。

更新日期：2020-03-06

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