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Contact time in cementing
Contact time is the period of time that a fluid flows past a particular point in the annular space during displacement. Contact time is an important consideration for successful cementing.
Estimation of contact time
Studies indicate that a contact time of 10 minutes or longer provides excellent removal of most drilling fluids. The volume of fluid needed to provide a specific contact time is
Vt = volume of fluid (turbulent flow), ft3 ;
tc = contact time, min;
qd = displacement rate, bbl/min;
5.615 = conversion between ft3 and bbl.
The calculation is simple, because only two readily available factors are required, and the calculation is independent of casing and hole size. The equation holds, as long as all of the fluid passes the point of interest.
- Brice JR., J.W. and Holmes, B.C. 1964. Engineered Casing Cementing Programs Using Turbulent Flow Techniques. J Pet Technol 16 (5): 503-508. SPE-742-PA. http://dx.doi.org/10.2118/742-PA.