Determination of Oil/Water Saturation Functions of Chalk Core Plugs From Two-Phase Flow Experiments

Abstract

A new procedure for obtaining oil/water saturation functions, i.e., capillary pressure and relative permeability, of tight core samples uses the pronounced end effect present in flooding experiments on such material. In core material with high capillary pressure, the end effect may allow determination of the saturation functions for a broad saturation interval. A complex coreflooding scheme provides the fluid distributions and production data from which the saturation functions are computed for both drainage and imbibition by a least-squares technique. A chemical shift NMR technique is used for fluid distribution determination. An undesirable interdependency of the saturation functions is avoided by their calculation from different data sets. Killough's method is employed to account for the scanning effect in hysteresis situations for both capillary pressure and relative permeability. The procedure is demonstrated on chalk samples from the North Sea. The experimental time is intermediate between the centrifuge and porous plate methods. ᭹ Step 1: Threshold pressure experiment. ᭹ Step 2: Transient flow drainage experiment. ᭹ Step 3: Stationary flow drainage experiment. ᭹ Step 4: Stationary flow internal imbibition experiment. ᭹ Step 5: Forced flow imbibition experiment.