Abstract

Probe permeameters are preferred for making fast, high density and non-destructive permeability measurements on relatively smooth rock surfaces. Probe measurements can be conducted with both steady-state and unsteady-state flows. The technique relies on geometric factors to account for highly non-linear hemispherical flow. Previous studies have presented geometric factors for homogeneous porous media. Naturally occurring porous media are rarely homogeneous. Some heterogeneities are natural, others are created during drilling (formation damage) and some during subsequent core handling (slabbing). Unfortunately, our ability to deal analytically with heterogeneity is limited. Thus, it is necessary to use numerical methods to derive geometric factors for these complex, but realistic situations.

A finite element simulator was used to study effects of heterogeneity on probe permeability measurements and the differences between the geometric factors for steady and unsteady state flows. Simulation results show that geometric factors for unsteady-state flows are almost identical to the ones obtained for steady-state. Effects of a nearby flow barrier on a probe measurement are studied experimentally and numerically. Results are compared, and an excellent match is observed. From flow barrier studies, we concluded that the effect of a local flow barrier is unimportant when the barrier is located farther than one-half of the probe-tip diameter from the probe.

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