Application of nanofluid to control fines migration to improve the performance of low salinity water flooding and alkaline flooding

Low salinity water (LSW) and alkaline flooding have been recognized as the two efficient improved oil recovery techniques to unlock residual oil. It has been widely reported that the efficiency of these methods critically improves with decreasing salinity and increasing pH of the slug injected during LSW and alkaline flooding respectively, and greater amount of oil can be recovered in these conditions. However, these chemical environments of low salinity and high pH are very unfavorable for in-situ particles retention and as a result, fines migration and subsequent formation damage is an accompanying phenomenon with these techniques. Therefore, one should choose the optimum salinity rather than the lower one to enhance the efficiency of a typical LSW project and also, the optimum pH for the injected slugs rather than the higher one to improve the efficiency of an alkaline flooding project. These limitations make the design of such flooding projects very difficult and challenging. This experimental work aims to probe nanoparticle (NP) treatment of colloidal particles migration occurred during the mentioned unfavorable conditions for particles retention. Zeta potential and turbidity analyses have been utilized as quantified tools to examine the effect of NPs on the interactions of colloidal particles with the medium surface. It was found that MgO NP can modify the zeta potential of the medium and in turn remarkably retain the colloidal fines in the presence of very low concentration of both monovalent and divalent salts; therefore, fines migration induced during low salinity conditions can be prevented. Furthermore, the presence of MgO NP on the beads surface significantly modifies/increases the point of zero charge (PZC) from around 3 to around 9 which in turn justifies the retention of particles in a wide range of alkaline conditions. It was found that the MgO NP-treated medium tends to retain around 97% of the in-situ fine particles at very alkaline conditions. Therefore, pre-flush of the medium with a slug of MgO nanofluid prior to alkaline flooding or LSW injection into the reservoir can serve as a promising remedy to counteract against the colloidal particles migration subsequently induced. This technique is of great interest in field application where improving oil recovery is desired; however, fines migration and subsequent formation damage should be avoided.