Abstract

In recent years, research activity to increase oil recovery from hydrocarbon reservoirs by smart water (SW) injection has risen sharply. Smart water injection is one of the most efficient and low-cost methods in the improved and enhanced oil recovery (IOR/EOR) process. One of the active mechanisms of smart water to increase the oil production is wettability alteration of the rock surface from oil-wet to water-wet conditions. Recently smart water injection into unconsolidated sandstone reservoirs due to disturbance of the rock surface equilibrium causes instability of formation particles and sand production. One of the main factors disturbing the equilibrium and sand production is the sandstone surface's wettability alteration mechanism caused by disjoining pressure and stresses on the rock surface. Reduction of the reservoir permeability and closure of fluid flow paths and consequent reduction of oil production are among the main damages of sand production. In this study, a complete study on optimum smart water design based on the least sedimentation due to mixing has been done by formation water compatibility tests and analysis on divalent ions through the Taguchi design. Then the water wet sandstones were converted to oil-wet condition by model oil (stearic acid + normal heptane) in different concentrations. The wettability effect of water wet, neutral wet oil-wet on the amount of sand production in the presence of smart water in the reservoir conditions was fully investigated. To prevent sand production, a very effective chemical method of nanoparticles was used. By stabilizing silica nanoparticles (SiO2) with an optimum concentration of 2000 ppm in smart water (pH = 8), according to the results of the zeta potential and Dynamic light scattering (DLS) test, the effect of wettability on sand production in the presence of smart nanofluid was fully investigated. The test results show a significant reduction in sand production and a rapid wettability alteration towards smart nanofluids' water-wet conditions. This indicates the improvement of fluid for enhanced oil recovery processes in unconsolidated sandstone reservoirs.

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