A mechanistic study of smart water injection in the presence of nanoparticles for sand production control in unconsolidated sandstone reservoirs

Abstract

In unconsolidated sandstone formations, fine sand particles movement as a result of contact between low salinity water (LSW) and rock surface minerals/interparticle cement disturbing the ionic equilibrium in the medium is recognized as the most common issue. Such unstable particles can obstruct some fluid paths and consequently, reduce the reservoir permeability and cause a type of formation damage. In this regard, adding nanoparticles (NPs) into the injected water may obviate shortcomings associated with sand production (SP). Charged NPs could easily adsorb onto the rock surface oppositely charged because of their ultra-small specific surface area and partially cover the rock surface. It can be as a protective layer for unstable minerals against the LSW as the destabilizer element. At these conditions, the solidity of the interparticle cement could stabilize the fine sand particles and impedes subsequent problems. In this study, a new approach has been introduced to optimize the composition of the SW using a statistical method. Moreover, the role of NPs in SP control during the SWI process has been surveyed here. The results obtained here reveal that adding silica NPs into the optimized injected water to unconsolidated sandstone samples not only enhances the oil recovery up to 10% but reduces about 81% of produced sand. NPs partial surface coating as a promising mechanism for stabilizing the fine sand particles has been proposed. The influence of SP on rock compressive strength has also been investigated and 46% improvement in rock strength was observed as a result of the presence of NPs in the injected fluid. Besides, for unconsolidated sandstones, an exponential trend of the weight of produced sand was observed and two empirical correlations have obtained to estimate the total mass of produced sand based on the type and the volume of the injected fluid. It is expected that this study could be helpful for a better understanding of acting mechanisms in the molecular scale behind the nano-assisted smart water injection (NSWI) for SP control in unconsolidated sandstone formations.