Lime Content of Drilling Mud-Calculation Method

A method of determining the lime content of drilling muds proposed by Battleand Chaney has been examined both in the Field Research Laboratories ofMagnolia Petroleum Co. and in field drilling operations. This proposedanalytical method is condensed as follows: Titrate one ml of mud and one ml ofmud filtrate, each with 0.02 N H2SO4 to the end point with phenolphthalein. Thevolume of acid in ml required for the mud titration is recorded as Pm and thatof the mud filtrate titration as Pf. The analytical procedure outlined by Battle and Chaney was found to be quitesatisfactory when reasonable precautions are used in mud sampling technique.Calculation of lime concentration by the method proposed in the abovepublication, however, has given values that varied as much as 100 per cent fromthe known lime content, for muds of either high or low solidsconcentration. By use of a formula, based on chemical equivalents of acid required fortitration, both laboratory and field data have been satisfactorily correlatedwith the known amounts of lime present in the muds. In this formula acorrection, FL, or volume fraction of liquid in the mud, is made for the solidcontent of the mud. Pm and Pf have the same significance as in the Battle andChaney equation. Table I shows typical data employing both formulas incalculating the lime content of various lime muds. This suggested procedure ignores lime which is in solution in the mud. Thesolubility of lime in water, normally about 0.5 lb per bbl, is greatlydecreased by the addition of caustic soda, and, in a lime mud, it is probablethat the concentration of dissolved lime is of the order of 0.1 lb per bbl.Such an amount of lime can be ignored, since it is within the range of accuracyof the method. T.N. 58