Enhancing heavy crude oil mobility at reservoir conditions by nanofluid injection in wells with previous steam stimulation cycles: Experimental evaluation and field trial implementation

Abstract

This study introduced a novel nanofluid injection method to enhance heavy crude oil recovery in steam-impacted wells, offering an alternative to traditional steam injection techniques. This research focuses on improving oil mobility by disrupting the viscoelastic network of asphaltenes through silica nanoparticle adsorption. Comprehensive experimental evaluations included nanoparticle characterization, reservoir fluid analysis, and dynamic core-flooding tests under reservoir conditions. Three carrier fluids, surfactant-based (SB), diesel-based (DT), and light hydrocarbon with surfactant (LHC + S), were tested with silica nanoparticles to identify the most effective combination. Key findings demonstrated that a concentration of 300 mg L⁻¹ of silica nanoparticles dispersed in LHC + S reduced oil viscosity by 57 % at 25 °C, lowered the contact angle from 47° to 15°, and decreased interfacial tension by 38.0 %. Core flooding revealed that nanofluid injection increased the recovery factor from 89 % to 92 %, confirming enhanced crude oil displacement. Field trials in two mature wells subjected to four prior steam cycles showed oil production increases of 32 % and 56 % during the first-month post-treatment, with cumulative gains of 11,148 Bbl and 2240 Bbl, respectively. Additionally, viscosity reductions of 60 % were sustained over 12 months, validating the long-term efficacy of nanofluid injection as a nonthermal Enhanced Oil Recovery (EOR) method. By eliminating the need for steam and significantly improving the oil displacement efficiency, this study demonstrates the potential of nanofluid injection to reduce the operational costs and environmental impact in heavy oil fields undergoing thermal depletion.