The Bunter Sandstone formation in the UK’s southern North Sea has been identified as having the potential to store large volumes of CO₂. Prior to injection, CO₂ is captured with certain amounts of impurities, usually less than 5%_vol. The dissolution of these impurities in formation water can cause chemical reactions between CO₂, brine, and rock, which can affect the reservoir quality by altering properties such as permeability. In this study, we explored the effect of CO₂ and impurities (NO₂, SO₂, H₂S) on reservoir permeability by measuring changes in grain size distributions after a prolonged period of 9 months, simulating in situ experimental conditions. It was found that the effects of pure CO₂ and CO₂-H₂S are relatively small, i.e., CO₂ increased permeability by 5.5% and CO₂-H₂S decreased it by 5.5%. Also, CO₂-SO₂ slightly decreased permeability by 6.25%, while CO₂-NO₂ showed the most pronounced effect, reducing permeability by 41.6%. The decrease in permeability showed a correlation with decreasing pH of the formation water and this equally correlates with a decrease in geometric mean of the grain diameter. The findings from this study are aimed to be used in future modelling studies on reservoir performance during injection and storage, which also should account for the shifts in boundaries in the CO₂ phase diagram, altering the reservoir properties and affecting the cost of storage.

英国南部北海的邦特砂岩地层已被确定具有储存大量CO ₂的潜力。在注入之前，CO ₂被捕获有一定数量的杂质，通常小于5％_vol。这些杂质在地层水中的溶解会引起CO ₂，盐水和岩石之间的化学反应，这可能会通过改变诸如渗透率之类的特性来影响储层质量。在这项研究中，我们通过测量长时间（9个月）后晶粒尺寸分布的变化，模拟了CO ₂和杂质（NO ₂，SO ₂，H ₂ S）对储层渗透率的影响，模拟原位实验条件。发现纯CO ₂和CO ₂ -H ₂ S的影响相对较小，即，CO _2的渗透率提高了5.5％，而CO ₂ -H ₂ S的渗透率降低了5.5％。另外，CO ₂ -SO _2的渗透率稍微降低了6.25％，而CO ₂ -NO ₂效果最明显，渗透率降低了41.6％。渗透率的降低显示出与地层水pH值降低相关，这同样与粒径的几何平均值降低相关。这项研究的结果旨在用于将来在注入和储存过程中对油藏性能的建模研究中，这也应考虑到CO ₂相图中边界的变化，改变油藏性质并影响储存成本。