BAKER HUGHES - Drilling Fluids Reference Manual

Oil / Synthetic Fluids
8. Do not use plastic or phenolic resin type materials for lost circulation.
9. Steam cleaners may be needed for general rig clean up. MIL-CLEAN ® diluted in water is an
excellent cleaner for oil mud coated equipment.
10. Volume control and dilution should be conducted with virgin drilling fluid whenever possible.
Displacement procedures
Displacement can occur either in casing or open hole with cased hole preferred. Prior to displacement,
the drilling fluids engineer should make certain all pits and lines are as clean as possible. It is not
uncommon to run a slug of base oil through the lines to clean and oil wet them. The trap doors on the
pits can be packed with barite if necessary to help prevent leakage.
The water-base fluid to be displaced should be diluted back to reduce yield point and gel strengths.
This will help prevent contamination of the oil-base fluid. A water spacer of sufficient volume to
occupy 500 to 1000 feet of annular volume should be used to chase the water-base fluid up the hole.
This will thin the water-base fluid and thicken the oil-base fluid to help hole cleaning and removal of
the water-base filter cake. During displacement, the drill pipe should be rotated and reciprocated
along with a high pump rate to help prevent channeling. Once displacement commences, the pumps
should not be shut down.
The total strokes should be calculated for the spacer to come around to the shaker. This will help
locate the interface. The shakers should be bypassed to remove the water-base fluid to a reserve or
waste pit. Contaminated oil-base fluid found at the interface should also be discarded (see Table 5-26
Troubleshooting).
Baker Hughes Drilling Fluids
Reference Manual
5-44 Revised 2006