Water/Oil Relative Permeability Endpoints of Intermediate-Wet, Low-Permeability Rocks

Abstract

The relative permeability endpoints oflow-permeability, intermediate-wet mudstones increased with flow rate. This was because of both a decrease in capillary end effect and an increase in capillary number. Hence, conventional analysis will incorrectly describe field behavior. We recommend an improved methodology.We imaged steady-state saturation profiles at the end of different rate floods on one sample. We analyzed these profiles, which were axially nonuniform, to obtain capillary-end-effect-corrected data for each flow rate. The saturation distributions were also radially nonuniform. We characterized core-scale heterogeneity using a miscible flow test and examined the influence of heterogeneity.We conducted long-term tests on three short samples to study the higher-capillary-number regime. These tests displayed the existence of a critical capillary number. where the water relative permeability endpoint increased dramatically. The corresponding rate was over a magnitude smaller than flow rates traditionally recommended to eliminate capillary end effects.

Relative permeabilities of gas and water for different rank coals

“…The centrifuging method cannot be gained from the production data at low mobility ratio as it cannot provide information of coal permeability in the low saturation region (Hirasaki and Rohan, 1995). Steady-state methods offer disadvantages, especially in the case of low permeability rocks where it is laborious to reach multiple steady states, and capillary forces and capillary end effects are significant (Firoozabadi and Aziz, 1988;Kamath et al, 1993). J.M.…”

Estimation of Dynamic Relative Permeability and Capillary Pressure from Countercurrent Imbibition Experiments

“…Steady-state methods require both phases to approach local equilibrium. This requirement results in time-consuming measurements for lowpermeability porous media because it is laborious to reach multiple steady states that are free of capillary-end effects (Firoozabadi and Aziz, 1991;Kamath et al, 1995). Capillary forces have a significant effect on multiphase flow, saturation distribution as a function of time, and recovery history in low-permeability rocks.…”

Scaling of Counter-Current Imbibition Process in Low-Permeability Porous Media, TR-121

“…Experience has shown that pressure gradients of more than 4500 kPdm (2OOpdft) are needed for conducting laboratory forced displacement experiments (Kamath et al 1995). The reservoir pressure gradient cannot be more than 110 kPdm (5 pdft), in practice, considering reservoir depth and injectivity.…”