Correlation of Capillary Number Relationships for Sandstone

TLDR

Capillary number relationships for displacing residual and continuous oil from water‑wet sandstones with permeabilities spanning two orders of magnitude are presented. The critical displacement ratio (ΔP/Lσ)cr and normalized reduced residual oil saturation both correlate with permeability and kwΔP/Lσ, respectively; continuous‑oil displacement requires lower capillary numbers than discontinuous oil up to 50 % waterflood residual, after which the relationships converge, and complete residual oil recovery occurs at kwΔP/Lσ ≈ 1.5 × 10⁻³ versus ≈ 2 × 10⁻⁵ for mobilization onset.

Abstract

Abstract Capillary number relationships are presented for displacement of both residual and initially continuous oil from water-wet consolidated sandstones having permeabilities that varied over about two orders of magnitude. It was found that the critical displacement ratio, (ΔP/Lσ)cr, for the onset of mobilization could be correlated with sample permeability. Relationships between normalized reduced residual oil saturation and capillary number (taken as kwΔP/Lσ) also were correlated satisfactorily. For sandstones, capillary numbers for displacement of continuous oil were lower than values for mobilization of discontinuous oil for down to 50% of normal waterflood residual. Thereafter, capillary number relationships for the two types of displacement were indistinguishable. Conditions for complete recovery of residual oil correspond to values of (kwΔP/Lσ) of about 1.5 × 10−3 as compared with about 2 × 10−5 for onset of mobilization.