P.L. Crenshaw, Dowell Division of The Dow Chemical Company
Cement plugs are one of the most important types of cement jobs ever performed. Therefore, they deserve the very best effort we can give to a problem. A successful plug job requires more attention to detail than most other cement jobs; the reason most of them fail is because they do not get this attention. The following guidelines will not guarantee success but they will provide a higher ratio of successes if used every time! Plugs need properties different from most other cement systems because they are intended for a different application entirely. Failure of cement plugs is most often due to a lack of hardness in the set cement. This lack of hardness usually can be traced to one or more of these common mistakes: 1. Mud contamination of the cement during placement 2. Drilling out too soon 3. Cement not initially designed for enough strength 4. Strong tendency of all people involved to want extra pumping time, so slurry is overretarded 5. Inaccurate BHT information - well is colder than expected because circulation effect isn"t considered and temperature is guessed rather than measured 6. Not enough cement volume used. Proper planning can eliminate these errors. Do all possible to eliminate these problems.