Experimental Studies of Low Salinity Water Flooding in Sandstone Porous Media: Effects of the Presence of Silica and Kaolinite

Abstract

In recent years, many studies have been conducted on the method of low-salinity water (LSW) injection and its effect on enhanced oil recovery (EOR) of oil reservoirs. The lower operating cost of this method has led many researchers to study this method on reservoirs that are in the second half of their natural production life. Different mechanisms have been proposed depending on the study of sandstone and carbonate samples, but to date, no broad consensus has been reached on a single mechanism. Among these mechanisms, fine migration has been widely reported as the important factor leading to EOR. In this study, focusing on the type of minerals (different percentages of silica and kaolinite) and creating artificial cores, the effect of water injection with different salinity levels was investigated on fine migration in sandstone samples using core flooding. Three sets of different laboratory tests were performed. In the first set, the effect of type and percentage of minerals was investigated; in the second set the effect of soaking time was evaluated; and in the third set the impact of aging was examined. In all implemented tests, parameters of increase in enhanced recovery, differential pressure, pH, turbidity, conductivity, and permeability were measured to understand the governing mechanisms as well as the influence of the presence of minerals in the process. The results show that unlike previous studies, the presence of kaolinite is not necessary for enhanced recovery, where damage to the formation is irreversible due to the closure of the pores affected by this mineral. Also, by adding the factor of time, the performance of this method can be improved and the parameter of aging exerting a significant effect on tertiary-enhanced recovery. The results of this study can provide a better understanding of fine migration mechanism in the LSW flooding. Based on the results, the effect of the clay particle interactions in sandstone samples can be identified in LSW process as well.