Effect of flow rate on imbibition three-phase relative permeabilities and capillary pressures

Effects of displacement pressure, pressure gradient, and flow rate on the s hape of relative permeability curves have long been a controversial subject in petroleum literature. For drainage experiments it has been reported tha t the relative permeabilities are independent of flow rate. However for imb ibition experiments the rare literature, mainly concerned with oil-water ph ases, does not agree on this point. Three-phase, unsteady state CT scanned displacement tests were conducted us ing fired Berea sandstone to obtain relative permeability and capillary pre ssure data. Eight percent Potassium Bromide eloped brine hexane, and nitrog en gas was used. Relative permeabilities and capillary pressures were then estimated simultaneously after minimizing a least squares objective functio n containing all available and reliable experimental data obtained from thr ee phase imbibition experiments using an automated history matching code wh ere simulated annealing was utilized. It has been found that brine and hexane relative permeability curves were a ffected much more compared to the gas relative permeability curve, especial ly near the endpoints. Moreover gas relative permeabilities decreased,vith increase inflow rate. Capillary pressure curves were affected in a similar manner. Finally, in order to confirm the above results an approach consisti ng of matching, at the same time, the fastest, the slowest, and a medium ra te experimental data were tested. The algorithm failed to find a set of flo w function curves which could fit both experimental data; therefore the con clusion was that for three-phase imbibition the flow functions depend on th e flow rate.