A Note on the Application of the Capillary Pressure Method for the Determination of Oil Recovery
- Walter Rose (Gulf Research and Development Co.)
- Document ID
- Society of Petroleum Engineers
- Transactions of the AIME
- Publication Date
- December 1949
- Document Type
- Journal Paper
- 325 - 327
- 1949. Original copyright American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Copyright has expired.
- 4.1.2 Separation and Treating
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Experimentation which measures differences in pressure across the interfacesof immiscible fluids in the interstitial spaces of porous media may be termed"capillary pressure experimentation". In the literature of petroleumtechnology since 1941 there have appeared twelve papers popularizing capillarypressure concepts and developing applications of these concepts for thesolution of problems of practical reservoir engineering importance, such as thedetermination of connate water, fluid distribution in transition zones,reservoir rock textural properties, and oil recovery from petroleumreservoirs.
Although a review of the literature would be justified at this time in order toreconcile the conflicting viewpoints which are contained in the cited papers,the object of this note will be of more limited scope. It is believed that therecent paper of Muskat calls sufficient attention to many of the uncertaintieswhich arise upon examination of the published literature, such that untilsatisfactory counter-proposals can be made it will serve our purpose only tomention some other like uncertainties. This will emphasize further the needconfronting petroleum technologists to reconsider and reformulate theapplication possibilities of capillary pressure experimentation. In particular,I suggest that we examine the thesis that capillary pressure experimentation asabove defined can lead to measurements reflecting the recovery of oil frompetroleum reservoirs, as was proposed first by Amyx and Yuster and was firstreduced to practice by the experimentation of Welge. In fact, I shall dealexclusively with the Welge papers since it is the principle one on this subjectwhich has appeared to date. I shall attempt to show that the possibility ofdescribing oil recovery features in terms of capillary pressure phenomena hasnot been established entirely.
The Welge paper was a pioneering effort to evaluate this recovery applicationpossibility. P. P. Reichertz comments on the Welge paper state that non-wettingphase discontinuities are developed occasionally in the Welge experiment, andrestate Muskat?s argument that discontinuous fluid elements (partiallysaturating the interstices of porous media which are elsewhere saturated withsome other immiscible phase or phases) are not subject to the requirements ofhydrostatic equilibrium. It is the purpose of my comment to show that it isunnecessary to make Reichertz' postulation regarding nonwetting phasediscontinuities (however valid) when it is desired to criticize Welge'stheoretical treatment of his problem. It can be shown that Welge's method ofmeasuring values for "capillary pressure" is invalid in many instancesof application, such that his reported curves of capillary pressure versusfluid saturation often have no physical meaning, even throughout the intervalof fluid saturation where it might be otherwise suspected that no phasediscontinuities occur.
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