Reinjection of produced water is of increasing importance in the oil industry as water production continues to increase worldwide. It provides an environmentally acceptable solution to the disposal of produced water, and contributes to pressure maintenance. The performance of the injection wells and the distribution of the injected water are strongly influenced by water quality and the build-up of formation impairment around the wellbore.

Solid particles and small oil droplets present in the injected water can block the reservoir pores and cause rapid and severe permeability decline. Total removal of solids and oil may not be economically feasible or practically possible. Therefore, to minimize or slow the rate of impairment, it is important to understand the relationship between the impairment mechanism and water quality parameters, such as the total suspended solids and oil droplet.

This experimental study highlights the importance of water quality for the purpose of water injection. An online particle size analyzer was used to measure particle size distribution and coalesces in the injected water. Different concentrations of suspended solid, oil droplet, water salinity, and oil viscosity were used in this study. The effect of suspended solids on the stability of oil-in-water emulsion was investigated. Finally, coreflood system was used to measure permeability decline during water injection containing suspended particle.

The results showed that increasing suspended solid concentration did not affect particle coalesce, but increasing oil concentration resulted in an increase of oil droplets coalesces. However, when a combination of solid particles and oil droplets were suspended in water, newly solid-oil attachment particles were formed. Increasing water salinity did not affect solid-solid coalesce, but formed smaller oil droplets. Higher oil viscosity generated relatively in larger oil droplets than lower viscosity oil. Visual observation of emulsion containing suspended solids and oil droplets showed more stabilized emulsion with higher salinity water than at lower salinity water. However, weaker emulsion was seen when high oil viscosity concentration was used. Finally, permeability reduction of core samples caused by oil droplets alone was insignificant, but higher damage was seen by suspended solids, and severe damage was observed with combined solid and oil droplets.

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