Effects of Temperature and Pressure on Rheological Properties of Cement Slurries

Abstract

A thorough knowledge of the behavior of cement slurries under elevatedtemperatures and pressures is necessary in order to solve properly the manyproblems presented in deep-well cementing operations. In the earlier days ofthe petroleum industry the depths of wells were shallow as compared to those oftoday, and the subsurface temperatures and pressures were not of sufficientmagnitude to affect seriously the problem of proper control of cement-slurryproperties. Today, however, the search for new reserves has extended drillingto such depths that bottom-hole temperatures of more than 200?F. andbottom-hole pressures of 3000 to 5000 lb. are not uncommon. Moreover, there isevery indication that within the next few years wells will be drilled to evengreater depths and bottom-hole temperatures and pressures will becorrespondingly higher than those with which we are concerned today. It has been realized for some time that the behavior of cement slurries at hightemperatures and pressures might be very different from that at atmospherictemperature-pressure conditions, but while the temperature effects have beeninvestigated with a reasonable degree of thoroughness, the pressure effectshave received little public attention. While the trend toward deeper drilling may make changes in cementing techniqueand the choice of cements imperative, it was the purpose of this investigationto consider factors having a bearing on the latter, only secondaryconsideration being given, for the present, to details of technique andequipment for oil-field use. More specifically, the purpose of this work was toconsider the effect of temperature and pressure upon the behavior of cementslurries. Although it has long been recognized that cements thicken and set rapidly withincreasing temperatures, practical methods for the quantitative determinationof these effects are comparatively recent developments. In 1935 Silcox and Rulepresented such a method, describing apparatus designed to measure theconsistency-time relationship of cement slurries at relatively hightemperatures. The practical importance of this apparatus in furnishing usefuldata for the evaluation of cement slurries for cementing operations has beenemphasized in various technical publications by such writers as E. L. Davis, F.Bingham, and J. E. Weiler. A paper describing the numerous tests now used toevaluate cements for oil wells was presented in 1939 by W. W. Robinson."Robinson describes the Consistometer and the ThickeningTime Tester, showingsimilarity of data from the two devices, and points out that the purpose ofeach apparatus is to determine the allowable time that a cement may be pumpedat a given temperature. T.P. 1207