A New Technique for Determining the Porosity of Drill Cuttings
- M.A. Westbrook (Shell Oil Company, Inc.) | J.F. Redmond (Shell Oil Company, Inc.)
- Document ID
- Society of Petroleum Engineers
- Transactions of the AIME
- Publication Date
- December 1946
- Document Type
- Journal Paper
- 219 - 222
- 1946. Original copyright American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Copyright has expired.
- 2.4.3 Sand/Solids Control, 1.6 Drilling Operations, 1.6.9 Coring, Fishing, 4.1.5 Processing Equipment, 4.1.2 Separation and Treating
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A method is presented for obtaining porosities of consolidated formationsfrom the drill returns. The method provides a means of determining the bulkvolume of a large number of particles, such as drill cuttings, by employing acapillary diaphragm for removal of surplus surface liquid from saturatedcuttings having pores of capillary size, which reduces the amount of errorpresent in former attempts to determine the porosity of drill cuttings. Themethod makes it possible to obtain a considerable amount of supplementary dataon consolidated formations.
Porosity is a direct measure of the volume of the voids in a formation. It maybe used for estimating the permeability of a formation provided that acorrelation of these two properties has been obtained from the analysis ofcores from the particular formation, and it forms a desirable aid ininterpreting electric logs. 1 These useful applications have emphasized theimportance of developing a method for determining the porosity of theformations penetrated by a well by some means other than coring, for even inexploration wells it is neither economical nor practical to core allformations. Also, in wells where at the outset the coring program appearscomprehensive, it is frequently found that, after certain layers are drilled,more complete information is required for evaluation. Porosity values, ifobtainable, would be of great assistance in such cases.
In soft formations it is usually possible to obtain porosities after drillingwith cores taken by side-wall coring devices. In hard consolidated formations,that coring procedure is not always practicable and other methods fordetermining porosities must be resorted to. A first choice is the examinationof drill cuttings, if an analytical procedure is available that is bothaccurate and reasonably rapid. Such a procedure has been devised and isapplicable to sand and limestone cuttings having pores of capillary size.Although improvements can yet be made, it is believed that the new technique issufficiently well developed to warrant description.
Preparation of Sample
The well samples containing the cuttings representative of the particularintervals are first washed through a No. 6 gauge screen. The cuttings remainingon the screen are large enough to use for the porosity measurements. From thesized sample, the cuttings to be examined are separated from the shale andother extraneous particles. It is recommended that 10 to 15 c.c. of theselected cuttings be used for measurements, although only 4 to 5 c c. were usedto make the comparative tests described later in this article. These cuttingsare extracted and dried by the same methods used for preparing core samples forporosity and other measurements.
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