Relative Permeabilities of Homogeneous and Heterogeneous Laminated Rock Samples under Hydrostatic and Triaxial Stresses

Abstract

Production performance of a hydrocarbon-bearing reservoir is vital and largely controlled by certain reservoir rock and fluids intrinsic properties. Therefore, realistic measurements of reservoir rock properties under simulated in-situ stress-state are necessary. This work is aimed at investigating the integrated effect of rock geomechanics and fluid flow by measuring oil-water relative permeability of homogeneous and heterogeneously laminated rock samples at hydrostatic and triaxial stresses. Homogeneous samples show a trend of decreasing oil relative permeability and slight increase in water relative permeability as mean effective stress increases either with the increase of radial confining pressure at constant axial stress or with the increase of axial stress at constant radial confining pressure. The significant increase of axial stress way above the radial confining pressure tends to reverse the trend of oil relative permeability due to microcracks initiation.Heterogeneous laminated samples with lamination parallel to flow direction show a decrease in oil relative permeability with no major effect in water relative permeability as axial stress increases up to the radial confining pressure. This is believed to be due to the increases of oil trapping. As radial confining pressure increases above the axial stress, oil relative permeability increases and no change was observed for water relative permeability. This behavior is attributed to the decrease in oil trapping due to the lamina close up with the increase of the radial confining pressure. When heterogeneous sample is subjected to constant low confining pressure and different increasing axial stresses above the confining pressure, an increase in oil relative permeability and minor change on water relative permeability was observed. This is believed to be due to the lamina opening with the increase of the axial stress overriding the radial confining pressure acting in the rock. In conclusion, it has been found that opposite consistent trends of relative permeability values can take place due to lamina opening and closure as a result of loading magnitude and orientation.