Applicability of a New Device for Cementing Flushing Fluid Evaluation

To clarify the application scope of an innovative evaluation device for cementing flushing fluid, a calculation model for shear rates of Newtonian, Bingham and power-law fluids on external wall of the inner barrel was established in accordance with the Robertson-Stiff rheological model and with consideration to the equivalent shear rate on external wall of the inner barrel and on annular sidewall in cementing. In addition, errors between the shear rate of the external sidewall of inner barrel and that of cementing annual sidewall under different rheological modes was analyzed. Research results showed that the shear rate at the inner wall of the device is equal to that at the cementing interface with no theoretical error for Newtonian fluids, while the shear rate of the inner cylinder wall is higher than that on the cementing interface, and the increase in shear rates is related to the inner and outer cylinder gap and rheological properties of the flushing fluids for Bingham and the power-law fluids. When the diameter ratio between the outer and inner barrel is 1.04-1.20 and the flushing power-law fluid flow indexes over 0.6, or plastic viscosity below 1.0 Pa/(mPa·s) for Bingham fluid, their relative error in the shear rate can be maintained less than 10%. Research results show the smaller ratio between external and internal barrels diameter would cause less relative error, and the application scope of the device would be more extensive.