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An accurate and easy to use procedure for measuring the potassium ion concentration in drilling and completion fluids has been developed and successfully used in Union Oil Company of California's drilling operations. This volumetric analysis is based on the quantitative conversion of soluble sodium tetraphenylboron to the insoluble potassium tetraphenylboron and back titration with a quaternary ammonium salt in the presence of Titan Yellow (Clayton Yellow) indicator which gives an easy to read color change endpoint from milky white to intense pink. The procedure described here is as fast as flame emission analysis and as accurate as the gravimetric analysis. That method has been used for several years in the fertilizer industry with success, but is new to drilling operations, at least in this revised form.

During drilling operations, drilling and completion fluids, containing potassium chloride or other potassium salts require constant monitoring potassium chloride or other potassium salts require constant monitoring of the potassium ion concentration to indicate possible depletion of the potassium in the mud system to maintain good drilling conditions and to potassium in the mud system to maintain good drilling conditions and to assure good subsequent well productivity. To minimize the detrimental effects of clay swelling and movement, certain inhibited muds include KCl at concentrations of 2-20%. The potassium concentration is the critical factor. Chloride analysis, which is a very simple analysis unfortunately is an incorrect measure of the material balance of the KCl concentration since chloride ions could originate from other sources. The current API listed method is too difficult to perform and flame emission analysis on a drilling site is not feasible. Laboratories which perform these analyses are not always accessible from the drilling site.

The proposed method is a volumetric analysis of potassium from drilling fluid filtrates, using sodium tetraphylboron (NaTPB) to precipitate the potassium and backtitrate the unused portion of NaTPB with a quaternary potassium and backtitrate the unused portion of NaTPB with a quaternary ammonium compound, like cetyltrimethyl ammonium bromide (CTAB). The indicator used in the titration is Titah Yellow (also called Clayton Yellow), which gives a very sharp and easily detectable endpoint from milky white to intensive pink. This method is rapid and accurate. In the back titration, the volume of titrant is read on a micro burette to the nearest hundreth of a ml. The two solutions used in the titrating procedure can be standardized in the laboratory prior to use in the procedure can be standardized in the laboratory prior to use in the field, and they are stable for prolonged periods of time thus preventing errors during their use under actual field conditions. After standardization, only a minimum of glassware is needed to perform the analysis and there is no need for electricity.

Volumetric Analysis for Potassium in Drilling Fluids

The reagents, glassware and supplies needed for the analysis are listed in the Appendix.