Some Factors Controlling the Pumping Time of Oil-well Cements

Abstract

High subsurface temperatures and pressures are making cementing operationsmore difficult as deeper producing horizons are being sought. Recordedbottom-hole temperatures above 200?F and pressures in excess of 12,000 lb. persq. in., obtained by combining hydrostatic and pump pressures, are notuncommon. Insufficient time is available for proper placement of standardPortland cement, because of the shortened setting time produced by theseexcessive temperatures and pressures, therefore special types of cements havebeen developed to overcome these difficulties. From the standpoint ofplacement, the ideal slurry would be one that would remain fluid long enough tobe placed, then harden rapidly, so that there would be a limited amount ofcontamination and the well could be placed on production in a minimum of time.It is highly desirable, therefore, that some method be devised to measureaccurately the time that any slurry will remain in a fluid state while beingpumped into the well. To study the effect of elevated temperature and pressure on fluidity, theauthors have developed the pressure-type consistometer (Figs. 1 and 2)described below, and are presenting data obtained with it, using slurries ofboth quick-setting and slow-setting cements. Studies were made over atemperature range from 110? to 270?F., and a pressure range from atmospheric to3000 lb. per sq. inch. Apparatus The fluidity of cement slurries at atmospheric pressure is usuallydetermined with the Halliburton consistometer or the Thickening Time Tester.These instruments are similar, in many respects, to an ordinary ice-creamfreezer. The slurry to be tested is placed in a container that is rotated at aconstant speed with an electric motor. Constant temperature is maintained bysurrounding the container with a thermostatically controlled bath. The torqueon the paddles, which is proportional to the force needed to shear the slurry, is indicated on a scale. The Halliburton instrument is calibrated from 0 to 100poises against fluids of known viscosity. T.P. 1399