Presence of Heterogeneities in Rocks during Laboratory Waterfloods: A Case Study Highlighting Differences in Relative Permeabilities between Homogeneous and Heterogeneous 1D Approaches

In Special Core Analysis, relative permeabilities Kr are obtained from laboratory coreflooding tests usingunsteady-state, steady-state, or semi-dynamic methods. To better represent the reservoir conditions, thesetests are performed at the reservoir conditions with live fluids. While restoring a representative wettabilitystate is crucial, a significant challenge remains in accurately selecting representative rock samples.It is always preferred to perform the coreflooding tests on homogeneous samples. For selecting the mosthomogeneous rock samples, several methods are used: CT imaging, minipermeametry, miscible tracer tests,x-ray attenuation technique (porosity distribution and saturation profiles), nonlinear differential pressurebefore breakthrough during primary drainage.When dealing with carbonate rocks, selecting homogeneous samples becomes a challenge: it is sometimesimpossible to find a homogeneous rock without small-scale heterogeneity features. Moreover, somecompanies even prefer selecting samples containing small-scale heterogeneities (along or/and across coreaxis heterogeneities), because they are a true representation of their reservoir quality, with respect todirectional injection scenario.Pairoys et al. published a paper at the 2024 Society of Core Analysts symposium discussing differentmethods to account for rock heterogeneity when interpreting the waterflooding lab results. Using theheterogeneous approach called the Egermann method, they successfully history-matched the noisysaturation profiles obtained during a steady-state waterflooding test performed on a heterogeneous rock. Itwas also shown that there were no significant Kr differences between the classical homogeneous methodand the Egermann method. It raised the question of the need to use the Egermann method, just for the sakeof a better history-match quality. In the case study presented in this paper, we demonstrate that differencesin Kr curves can be observed: not using the Egermann method when interpreting waterflooding tests onheterogeneous rocks may lead to overly optimistic Kr curves.