Determination of Graphite in Drilling Mud

A field procedure for determining graphite in drilling mud is presentedwhich is sensitive to 0.25 lbs/bbl and accurate to 20 per cent. The method, utilizing oil flotation principles, is suitable for use in all oil-free waterbase muds except those containing lignosulfonates, lignites, or surface activeagents. Introduction Graphite was proposed as a drilling lubricant as early as 1940, but has notbeen used extensively until recently. Graphite has been substituted for oil incertain instances to avoid oil contamination of core samples since it has beenfound that graphite does not interfere with routine core analysis. A major difficulty in using graphite is the lack of a satisfactory field testfor determining the concentration of graphite in mud. Discussion of Method Several possible methods of analysis were investigated, including chemicalseparation, density fractionation, radioactive tracers, and oil flotation. Theinvestigation indicated that a satisfactory method for field use could bedevised using an oil flotation method. It was found that toluene shaken with ahighly diluted mud sample would recover sufficient graphite to be apparent inthe oil phase. Refinement and standardization of technique made it possible todetect as little as 0.25 lb/bbl graphite and to estimate graphite content towithin 20 per cent by using a visual comparison method. The test is limited to oil-free water base muds. Quebracho, phosphates, orbarytes in the mud do not interfere with the test but surface active agents, lignosulfonates, and lignites evidently render the graphite water-wet so thatnone may be recovered by oil-flotation. T.N. 185