Subsequent work, however, has shown that adsorption of surfactants can either increase or decrease the hardness of crystalline surfaces, depending on the nature and amount of the surfactant and on the particular crystalline substance.22, 23, 24' 25, 26, 27 Moreover, surfactants that decreased the hardness, or decreased the triaxial yield strength only when the failure was ductile, increased the penetration rate of drag bits, but decreased that of roller and diamond bits. On the other hand, surfactants that increased the hardness of the rock, decreased the penetration rate of drag bits, but increased that of roller and diamond bits. For example, Robinson23 found that when the pore fluids of Indiana limestone contained salts of dicarboxylic acids with an odd

Figure 7-17. Variation in rate of drilling quartz, microcline and Westerly granite with a diamond core bit In aqueous DTAB environments (2200 rpm). (From Jackson, etal.26)

Log Cone. DTAB, Mol/L

Figure 7-17. Variation in rate of drilling quartz, microcline and Westerly granite with a diamond core bit In aqueous DTAB environments (2200 rpm). (From Jackson, etal.26)

number of carbon atoms, such as sodium azelate, the yield strength under conditions of ductile failure was reduced to 13 x 103 psi (from 16 x 103 for water) and the drilling rate with a micro drag bit increased as shown in Figure 7-14, but the drilling rate with a micro roller bit decreased as shown in Figure 7-15. Salts of dicarboxylic acids with an even number of carbon atoms, such as sodium adipate, slightly increased the yield strength from 16 to. 16.9 x 103 psi, and decreased the penetration rate of a micro drag bit, but slightly increased that of a micro roller bit.

Other workers used a sclerometer to observe the influence of electrochemical environment on the surface hardness of materials.21' 22' 24, 25, 26 This instrument measures the hardness by the damping of a pendulum which causes a diamond to scratch the surface of the test material. The electrochemical environment is controlled by a layer of liquid spread over the surface. By this means it was shown that the surface hardness of many materials was maximum when the liquid reduced the zeta potential (see

bit is necessary to relieve stresses. On the other hand, because of the high negative rake angle of diamond bits, chips are formed by the coalescence of cracks, which would be inhibited by plastic behavior. A similar explanation would hold for chip formation by roller bits.


Surface free energy of a solid

Surface free energy of a liquid

Surface free energy at a solid/liquid boundary

Gravitational constant

Height of liquid rise in a capillary

Capillary radius

Work of cohesion

Work of adhesion

Surface tension


Contact angle


1. Bikerman, J.J., Surface Chemistry; Theory and Applications, second edition. Academic Press, New York, 1958. pp. 8-13.

3. Sharpe, L.H., Schohorn, H., and Lynch, C.J., "Adhesives," InternationaI Science and Technology (April, 1964). pp. 26r37.

4. Burdyn, R.F., and Wiener, L.D., "Calcium Surfactant Drilling Fluids," World Oil (Nov., 1957). pp. 101-108.

5. Foster, W.R., and Waite, J.M., "Adsorption of Polyoxyethylated Phenols on Some Clay Minerals," Amer. Chem. Soc. Symp. on "Chemistry in the Exploration and Production of Petroleum," Dallas (April, 1956). pp. 8-13.

6. Griffin, W.C., "Calculation of HLB Values of Non-Ionic Surfactants," J. Soc. Cosmetic Chem., vol. 5, No. 4 (Dec., 1954). pp. 1-8.

7. Mallory, H.E., Holman, W.E., and Duran, R.J., "Low-Solids Mud Resists Contamination," Petrol. Eng. (July, 1960). pp. B25-B30.

8. Browning, W.C., "Lignosulfonate Stabilized Emulsions in Oil Well Drilling Fluids," J. Petrol. Technoi (June, 1955). pp. 9-15.

9. Simpson, J.P., Cowan, J.C., and Beasley, A.E., "The New Look in Oil-Mud Technology," J. Petrol. Technoi. (Dec., 1961). pp. 1177-1183.

10. Darley, H.C.H., "Chalk Emulsion—A New Completion Fluid," Petrol. Eng. (July, 1972). pp. 45-51.

11. David, A., and Marsden, S.S., "The Rheolegy of Foam," SPE Paper No. 2544, Annual meeting, Denver, Sept. 1, 1969.

12. Beyer, A.H., Millhone, R.S., and Foote, R.W., "Flow Behavior of Foam as a Well Circulating Fluid," SPE Paper No. 3986, Annual meeting, San Antonio. Oct. 8-11, 1972.

14. Anderson, G.W., Harrison, T.F., and Hutchison, S.O., "The Use of Stable Foam as a Low-Pressure Completion and Sand-Cleanout Fluid," A pi Drill, and Prod. Pract. (1966). pp. 4-13.

15. Anderson, G. W., "Near-Gauge Hole Through Permafrost," Oil Gas J, (Sept. 20, 1971). pp. 129 -142.

16. Mitchell, B,J„ "Test Data Fill Theory Gap on Using Foam as a Drilling Fluid," Oil Gas J. (Sept. 6, 1971). pp. 96-100.

17. Krug, J.A., and Mitchell, B.J., "Charts Help Find Volume, Pressure Needed for Foam Drilling," Oil Gas J. (Feb. 7, 1972). pp. 61 64.

[g.Millhone, R.S., Haskin, C.A., and Beyer, A.H., "Factors Affecting Foam Circulation in Oil Wells " SPE Paper 4001. Annual meeting, San Antonio, Oct. 8, W72,

19. Hutchison, S.O., and Anderson, G.W., "Preformed Stable Foam Aids Workover Drilling," Oil Gas J. (May 15, 1972). pp. 74-79.

20. Rehhindcr, P.A., "On the Effects of Changes of Surface Energy on Cleavability, Hardness and Other Properties of Crystals," Proc. 6th Conf. of Physics, Moscow, 1928. p. 29.

21. Rehbinder, P.A., Shreiner, L.A., and Zhigach, K.F., "Hardness Reducers in Drilling," Academy of Science, USSR; Translation by Council for Sei. & Indust. Research, Melbourne, Australia, 1948. p. 163.

22. Heins, R.W., and Street, N., "An Evaluation to the Rehbinder-Kugnetsov Pendulum Technique in Hardness Measurements," Soc. Petrol. Eng. J. (June, 1965), pp. 177-183; Trans AI ME, vol. 234.

23. Robinson, L.H., "Effect of Hardness Reducers on Failure Characteristics of Rock," Sue. Petrol. Eng. J. (Sept., 1967). pp. 295-300; Trans AIME, vol. 240.

24. Engelmann, W.H., Terichow, O., and Selim, A.A., "Zeta Potential and Pendulum Sclerometer Studies of Granite in a Solution Environment," U.S. Bureau of Mines, Report of Investigations, No. 7048, Washington, D.C. (Nov., 1967).

25. Westwood, A.R.C., Macmillan, N.M., and Kalyoncu, R.S., "Chemomechanical Phenomena in Hard Rock Drilling," Trans AIME, vol. 256 (June, 1974). pp. 106-111.

26. Jackson, R.E., Macmillan, N.H., and Westwood, A.R.C., "Chemical Enhancement of Rock Drilling," Proc. 3rd Cong. Internat. Soc. Rock Mechanics, Denver, Spet. 1-7, 1974.

27. Mills, J.J., "Environment-Enhanced Disintegration of Hard Rocks," Martin Marietta Lab. Report No. Tr 78-10C to Nat. Sei. Foundation, Washington, D.C. (Feb.. 1978).

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