Impact of Reservoir Salinity on Oil Recovery Using Surface-Modified Silica Nanofluid for Offshore Oilfield Applications

Abstract

Abstract Hydrocarbons (oil and gas) contribute significantly to the total global energy requirement, thus, oil recovery improvement from the current reservoirs is key. Nanotechnology based enhanced oil recovery (EOR) is a potential technique that can considerably improve the oil recovery factor. However, complex reservoir fluids which are highly saline (specifically in offshore) affect the stability of nanofluids and limit their efficacy through pore blockage during flow through porous media and offer a reduction in oil recoveries. This study thus proposes a novel technique for nanofluid formulation using different additives and surface-active agents and investigated them for stability in different techniques. Moreover, the formulated nanofluid is then tested for EOR in sand-pack experiments. The sand-pack is fully saturated using a NaCl solution; providing a realistic high saline laboratory model during flooding similar to an offshore environment. Various studies involving the stability and viscosity of nanofluids, and efficiency for EOR for offshore reservoirs have been reported. The efficiency of the nanofluid systems for stability, rheologicalproperties, and EOR has also been compared with the conventional nanofluid and newly formulated nanofluid flood schemes. This study reports that the saline environment severely damage the nanofluid stability by reducing electrostatic repulsive forces (screening electrical charges of NPs), subsequently, quick settlement of NPs was observed. The agglomeration and sedimentation of NPs within the nanofluids generally reduces the cumulative oil production by permeability impairment. However, the inclusion of surface active agents (surfactant) re-establishes the physical stability of the surface coating mechanism which curtailed the effect of salinity, especially in offshore oilfields. The surface-coated NPs in the nanofluid enhanced stability for a prolonged duration by maintaining nanometer size which is crucial to avoid early particle aggregation thus demonstrating incremental oil recovery in offshore oilfield applications. This study discusses the novel fabrication methodology of stable nanofluids using colloidal aspects for offshore oilfield applications where formations salinity becomes a major challenge during flow through porous and permeable media.