- Use a cement stinger and cover cement and spacer lengths. This will minimize contamination and fluids intermixing.
- Always set base for off-bottom cement plugs, this can preferentially be a bridge plug (if cased hole) or alternatively a viscous pill. In case a viscous pill is used place a side jet diverter sub at the end of the stinger to avoid jetting flow downwards.
- Displace at maximum rate possible, ECD permitting. Cementing contractor should provide computer simulation for optimized placement.
- The maximum recommended cement plug length than can be placed in a single attempt is 200 meters (general “rule”)
- The main reason for failed cement plugs is cement slurry contamination:
- Reverse circulation is “preferred” to conventional direct circulation, since conventional (bottom up) circulation takes a longer interval of time
- Do not circulate out at the top of the cement plug. The drill pipe should be pulled back at least 20 to 50 meters above the expected top of cement before attempting to reverse or circulate out
- Beware of ECD when reversing out if there are open perforations, top of liner or exposed open-hole. Reverse circulation apply more pressure on the formation than direct circulation.
- Whenever reverse circulation is done, both the circulating pressure and the slurry thickening time must be considered and carefully monitored.
- In case of open hole cement plugs, the preferred method is direct circulation to avoid high ECD.
Please help me expand these guidelines. Any suggestion based on your experience?