Nanofluids are proven to be efficient agents for wettability alteration in subsurface applications including enhanced oil recovery (EOR). Nanofluids can also be used for CO₂-storage applications where the CO₂-wet rocks can be rendered strongly water-wet, however no attention has been given to this aspect in the past. Thus in this work we presents contact angle (θ) measurements for CO₂/brine/calcite system as function of pressure (0.1 MPa, 5 MPa, 10 MPa, 15 MPa, and 20 MPa), temperature (23 °C, 50 °C and 70 °C), and salinity (0, 5, 10, 15, and 20% NaCl) before and after nano-treatment to address the wettability alteration efficiency. Moreover, the effect of treatment pressure and temperature, treatment fluid concentration (SiO₂ wt%) and the period of nano-treatment on the wettability of calcite is examined. We find that nano-treatment alters the wettability significantly i.e. intermediate-wet calcite turns strongly water-wet after treatment (e.g. at 20 MPa and 50 °C, θ = 64° for intermediate-wet calcite, and θ = 28° for nano-treated calcite). Consequently, pre-injection of nanofluids will significantly enhanced the storage potential. It was also found that the permanent shift in wettability after nano-treatment is a function of treatment conditions including temperature, pressure, and treatment duration time and that surfaces treated under high pressure and low temperature yield better wettability alteration efficiency. We point out that the change in wettability is attributed to the changes in surface properties of the nano-treated sample. The results of the study thus depict that nanoparticles can significantly enhance storage potential and de-risk storage projects.

事实证明，纳米流体是改善地下采油率（包括提高采油率）的润湿性的有效剂。纳米流体还可以用于CO ₂储存应用，其中可以使CO ₂湿润的岩石具有很强的水润湿性，但是过去没有对此方面给予任何关注。因此，在这项工作中，我们提出了与压力（0.1 MPa，5 MPa，10 MPa，15 MPa和20 MPa），温度（23°C，50°C ）有关的CO ₂ /盐水/方解石系统的接触角（θ）测量值。C和70°C）和盐度（0、5、10、15和20％NaCl）在纳米处理之前和之后进行处理，以解决润湿性改变的效率。而且，处理压力和温度，处理液浓度（SiO ₂重量％）和纳米处理的时间对方解石的润湿性进行了检查。我们发现，纳米处理显着改变了润湿性，即中湿方解石在处理后变成了很强的水润湿性（例如，在20 MPa和50°C下，中湿方解石的θ= 64°，对于纳米方解石的θ= 28°处理的方解石）。因此，纳米流体的预注射将大大提高储存潜力。还发现纳米处理后润湿性的永久性变化是包括温度，压力和处理持续时间的处理条件的函数，并且在高压和低温下处理的表面产生更好的润湿性改变效率。我们指出，润湿性的变化归因于纳米处理样品的表面性质的变化。