Assessment method for flushing efficiency of flushing liquid in cementing

Innovative devices and test methods have been developed for assessment of flushing efficiency to compensate insufficiencies of existing methods in repeatability and accuracy. Newtonian fluids are used to highlight distribution of shearing rates in circular zones between 2 coaxial cylinders. By changing diameters of cylinders and rotation speeds of rotors, shearing rate of flushing liquid on internal wall of cylinders can be matched with the shearing rate on site. According to changes in drilling fluid attached to internal wall of the cylinder before and after flushing, flushing efficiency can be determined effectively. The newly-developed technique has been used to assess flushing efficiencies of three different flushing liquids. In accordance with relevant assessment conclusions, optimal flushing liquid type and volume can be identified. Research results show the innovative method may effectively simulate shearing rate and flushing time of flushing liquid to borehole sidewalls during cementing operation. In the same test, changes in results of flushing efficiency can be controlled within 5%. With relatively high repeatability, the method can be used to assess flushing efficiencies.