Techniques to handle limitations in dynamic relative permeability measurements

The objective of this work was to understand the limitations of the conventional methods of calculating relative permeabilities from data obtained from displacement experiments.; The Johnson, Bossler and Neumann (JBN) method is the industry standard for measuring relative permeabilities from field cores. It is known that the relative permeabilities calculated by the JBN method from low rate displacements are often in error due to the capillary forces. Sometimes history matching methods are used to calculate the relative permeabilities. Generally 1-D numerical models, that assume uniform initial saturation distribution, are used for this purpose.; The pressure drop and recovery data generated from 2-D, r-z numerical simulations were used to study the errors introduced in the calculated relative permeability curves when using the JBN method. The results indicate that, because of the saturation gradients in the core, the relative permeabilities obtained from the JBN method show large errors at low water saturations.; In this study, using the CT scanner to measure in situ saturations, it was observed that even at relatively high rates there are saturation gradients in the core after the drainage displacements. These saturation gradients cause additional pressure drop through the core. It is therefore recommended that control experiments should be conducted using some in situ saturation measurement technique to determine the extent of the end effects and the saturation gradients in the cores.; The Berea sandstone cores, used in this study even after baking to deactivate the clays, were found to be sensitive to the brine used in the experiments. It is therefore necessary to conduct the laboratory experiments using fluids, which are compatible with the rock.; From the analysis of the experimental data using both the JBN and the history matching methods, it was observed that both the imbibition and drainage relative permeability curves and the end point saturations are functions of rate. It is therefore necessary to conduct relative permeability experiments at rates comparable to the expected reservoir flow conditions.; Results from the history matching technique have shown that it is necessary to start the simulations with the correct saturation distribution in the core. The imbibition permeabilities determined by the history matching method are poorly defined because of the piston like displacement in the strongly water wet system. The relative permeabilities obtained from the history matching method have also shown a strong dependency on the rate.; The comparison of the relative permeabilities obtained by the two methods have shown that the relative permeabilities of the non-wetting phase obtained by JBN were consistently lower that those obtained by the history matching method. This trend is even observed at the high rate displacements. The relative permeability curves for the wetting phase were almost identical, except that the JBN method only defines the curves for saturation values higher than that at the time of breakthrough.