Pipe Flow Rheometry: Rheological Analysis of A Turbulent Flow System Used for Cement Placement

Abstract

ABSTRACT Determination of the Theological behavior of cement slurries is essential for proper evaluation of flow rates required to achieve optimum mud removal. Rhe-ological characteristics of cement slurries and spacer fluids have been evaluated using pipe-flow rheometry. By this method, rheological measurements were obtained by monitoring the pressure required to pump a fluid through either a pipe or an annular gap. The results suggest that the rheological properties of cement slurries are modified by apparent "slip" at the pipe surface making the onset of turbulence more difficult to achieve. This wall "slip" is attributed to particle migration away from the pipe surface when the fluid is sheared. Due to this anomalous behavior, a three-parameter mathematical model is required to evaluate pump rates required for the onset of turbulence. Use of pipe-flow rheometry has resulted in the design of a turbulent flow fluid which is "rheology-con-trolled" to permit easy calculation of the critical pump rate. The value of turbulent flow in cement placement is demonstrated by field evaluation of several wells in which production liners and intermediate casings have been successfully cemented into place using a "rheology-controlled" spacer fluid ahead of the cement slurry. To insure "rheology-controlled" behavior, the spacer fluid exhibits excellent fluid-loss control to inhibit rheological changes detrimental to good mud removal. Pipe-flow rheometry has been instrumental in characterizing the factors responsible for turbulent flow behavior. Proper rheological evaluation coupled with fluid-loss control behavior will give the necessary information for optimizing cement placement.