Abstract
Lab-on-a-chip methods were used to visualize the pore-scale distribution of oil within a mixed-wet, quasi-monolayer of marble grains packed in a microfluidic channel as the oil was displaced by water. Water injection rates corresponding to microscopic capillary numbers between Ca = 5 × 10-8 and 2 × 10-4 (Darcy velocities between 0.3 and 1100 ft/d) were considered. As expected, early-time water invasion transitions from stable displacement to capillary fingering with decreasing Ca, with capillary fingering observed at Ca ≤ 10-5. End-point oil saturation decreases with Ca over the entire range of Ca considered, consistent with the canonical capillary desaturation curve. In contrast, Sor derived from approximate numerical simulations using reasonable Pc(Sw) do not display a strong dependence on Ca. These results suggest that the Ca dependence of end-point oil saturation is largely due to capillary end effects which, under conditions considered presently, affect the entire length of the packed bed.
Highlights
Invasion of a non-wetting phase into a porous medium saturated with a wetting phase has been studied extensively in numerical simulation (e.g., [1]) and experiments using idealized 2D or quasi-2D microfluidic devices [e.g., 2, 3, 4, 5, 6]
The significance of capillary end effects is assessed by comparing observed end-point saturations to residual oil saturation estimated from numerical simulations
Under conditions considered presently, capillary fingering occurs at Ca ≤ 10-5
Summary
Invasion of a non-wetting phase into a porous medium saturated with a wetting phase has been studied extensively in numerical simulation (e.g., [1]) and experiments using idealized 2D or quasi-2D microfluidic devices [e.g., 2, 3, 4, 5, 6]. Most of these studies have considered conditions characteristic of primary drainage that is, the invasion of the non-wetting phase occurs in a porous medium fully saturated with the wetting-phase, and pore-scale displacement mechanisms under these conditions have been stablished [1, 2, 7, 8]. The significance of capillary end effects is assessed by comparing observed end-point saturations to residual oil saturation estimated from numerical simulations
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call