Transverse DC Magnetic Treatment of Injection Water for Enhanced Oil Displacement in Clay-Bearing Sands

Magnetic treatment of injection water has been proposed as a low-cost, chemical-free means of improving waterflooding, but laboratory evidence that links field intensity, pressure, electrokinetic behaviour and oil displacement remains limited. This study investigates the effect of a constant transverse magnetic field (40–150 mT) applied to injection water upstream of a linear sand–clay (75:25) porous-medium model, 120.4 cm long and 4.2 cm in internal diameter. First, single-phase water flow was examined at 1.6–30.4 atm, recording the potential difference, electrical resistance and outflow rate. Second, three oils with kinematic viscosities of 24.9 mm²/s (paraffin oil), 47.49 mm²/s (machine oil) and 198 mm²/s (refined transformer oil) were displaced by untreated and magnetically treated water at pressures up to 35.2 atm. Magnetic treatment lowered the potential difference and resistance of the water-saturated medium and increased the water outflow rate. In oil displacement, the final oil displacement coefficient increased from 47.38% to 60.64% for machine oil, from 42.30% to 54.32% for paraffin oil and from 37.08% to 50.36% for transformer oil at the most effective intensity of 125 mT, while the water displacement coefficient decreased. Magnetic treatment also stabilised the electrokinetic response during displacement. A generalised filtration law that includes electromagnetic forces is presented.