Shale Inhibition Efficiency of Commonly Used Mud Additives

by
Juan P. Luzardo, (M.S.E.)

University of Texas at Austin, 1994
Supervisors: Martin E. Chenevert
Steven L. Morriss

A recent method developed by Du Pont to evaluate shale inhibition properties of drilling fluids, has been improved and adapted for use with artificial shale samples made of calcium bentonite and silica sand. This method has been applied to the analysis of shale inhibition properties of several fluids, which include pure brines of different potassium and sodium salts, and combinations of those brines with commercial drilling fluid additives. It has been proven that the method is reproducible, relatively easy to perform, useful in terms of data generation capacity, and the results obtained are comparable to previous results obtained in the field. The results obtained show that potassium salts are, in general, more efficient in terms of shale inhibition capacity than sodium salts, as has been observed in the field. In addition, it has been possible to determine that the drilling fluid additive mechanisms for shale inhibition include at least four different types, depending on the physical and chemical nature of the additive. Finally, a list of the different drilling fluid systems tested, in order of performance, has been provided.

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