Use of Centrifuge for Determining Connate Water, Residual Oil, and Capillary Pressure Curves of Small Core Samples
- R.L. Slobod (Atlantic Refining Co.) | Adele Chambers (Atlantic Refining Co.) | W.L. Prehn Jr. (Atlantic Refining Co.)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- April 1951
- Document Type
- Journal Paper
- 127 - 134
- 1951. Original copyright American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Copyright has expired.
- 1.6.9 Coring, Fishing, 2.4.3 Sand/Solids Control, 5.2.1 Phase Behavior and PVT Measurements, 4.1.2 Separation and Treating, 5.2 Reservoir Fluid Dynamics, 4.1.5 Processing Equipment
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The centrifuge has been found to be an extremely useful tool for determiningcapillary pressure curves and for establishing connate water and residual oilin small core plugs. The use of the centrifuge for determining the propertiesof small core plugs has been discussed in the literature, but practically noexperimental evidence has been presented justifying the use of this method inpreference to other methods (mainly disc method) now in use. Data have beenaccumulated and are now presented demonstrating the advantages of thecentrifugal method, some of which are: (1) rapid establishment of equilibrium,(2) excellent precision yielding very reproducible results, (3) availability ofhigh pressure differences between phases, (4) simple operational procedure, and(5) ability to establish connate water, residual oil, or to obtain completecapillary pressure curve in one day or less. A commercially availablecentrifuge capable of speeds up to 3,800 rpm, and a high speed attachmentproviding a maximum rate of rotation of 18,000 rpm were used in this work inconjunction with core holding tubes designed specifically for thisapplication.
In view of the outstanding advantages associated with the use of thecentrifuge the conclusion has been drawn that this method should be used inplace of the more tedious, slower, and less reliable disc method fordetermining capillary pressure curves and for establishing connate water andresidual oil in small core plugs.
The need for accurate values of connate water, residual oil, and capillarypressure curves in reservoir engineering has been recognized for many years,and the extent of the effort devoted toward solving these problems is reflectedin the large number of papers which have appeared in the literature during thepast decade. Most of the methods discussed in the recent literature employ aporous disc as a semi-permeable membrane to separate two immiscible phases andmake possible the application of an explicit difference in pressure between twophases in the core. Thus, in the determination of the capillary pressure curvethe wetting phase (water) is displaced by the non-wetting phase (air oroil).
Several investigators have used centrifugal forces to develop pressuredifferences between phases. As a result of the first work in this field theconclusion was reached that "the more rapid centrifugal method formeasuring irreducible saturation may have equal value, (compared to use ofdiscs) but more work is required to establish this point." This work wasfollowed in 1945 by a more detailed study in which the concepts of thisexperimental work were more clearly enunciated. A method for calculatingsaturation for any given speed of rotation based on the observed volume ofwater displaced was developed and a wider application of the method wassuggested.
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