The Influence Law of Shear Rate on the Thickening Time of Cement Slurry

Shear rate is an important influence on the thickening time of cement slurry, and the determination of the real thickening time is significant for safety in cementing engineering. By establishing mathematical models for the shear rate of cement slurry under two thickening statuses in the borehole and in the lab, the thickening test was conducted under different shear rates (at 30℃ and 80℃) to identify the influence law of shearing rate on the thickening time of cement slurry. At 30℃, the deviation of thickening time is more than 2 h with shear rate of 22-652/s, and the thickening time is shorter at a low shear rate. At 80℃, the deviation of thickening time is less than 1 h with shear rates of 177-885/s, and the thickening time is shorter at a high shear rate. Research results showed that the thickening test at a rotation speed of 150 r/min could effectively simulate the thickening time in most cementing operations. As for cementing operations involving large-sized surface casing and small annulus, suitable shear rates should be used in accordance with specific conditions to perform thickening tests of cement slurry, so as to determine the thickening time in cementing operations accurately and ensure the safety of cementing operations.