Effect of Temperature on Plastering Properties and Viscosity of Rotary Drilling Muds

Abstract

The plastering properties of six representative California drilling mudswere studied over a temperature range of 700 to 1750 F. at several mud weights, using a high-pressure circulating filter press with full size consolidatedcores. In all tests, with untreated as well as with chemically treated muds, the filtration rates at elevated temperature were higher than at lowtemperatures and in nearly every case this increased filtration rate wasnotably larger than could be attributed alone to the decreased viscosity ofwater-the flowing medium-at elevated temperatures. It is concluded that no existing method will permit even an approximatedetermination of the filtration rate at high temperature from data at roomtemperature. It is necessary to measure filtration at the temperature actuallyanticipated in the well, or to make a sufficient number of tests at variouslower temperatures so that a small extrapolation of these data to theanticipated well temperature may be applied. Such tests should be carried outon the mud as actually used in the well. The viscosity of each of the muds was determined over the same temperaturerange. While no relationship was observed between mud viscosity and plasteringproperties, it was found that chemical treatment of the muds for viscosityreduction shifted the temperature of minimum viscosity to appreciably highervalues than for untreated muds. Importance of Plastering Properties A survey of the literature on rotary drilling muds clearly shows the growingrealization of theDDDD importance of plastering properties, not only from thepoint of view of the successful completion of the mechanical operation ofdrilling the well but also from the point of view of minimum impairment of thenatural flow possibilities of a given well. T.P. 1116