BAKER HUGHES - Drilling Fluids Reference Manual

RESERVOIR APPLICATION FLUIDS
Pre-Displacement
Once the well has reached TD, circulate a minimum of one bottoms-up and short trip into the
casing. Go back to bottom and circulate a minimum of one bottoms-up. If well conditions are
stable, clean the mud pits and surface equipment by flushing sufficiently with seawater/drillwater
to remove all residue of drilling mud.
Weighted Lead Spacer
This spacer is designed to push the mud out of the wellbore. The spacer density should be slightly
heavier (0.2 ppg) than the mud being displaced. YP = 1.5 times the YP of the mud. Spacer volume
is based on the wellbore geometry and sufficient to cover 500 to 1000 feet of the largest annular
diameter.
Circulating Rate
Pump at the maximum safe rate with the minimum rate determined by the wellbore configuration.
Pump by conventional (forward) circulation. Rotate and reciprocate the pipe while pumping but do
not reciprocate pipe while spacers or interface is near the end of the workstring. Do not shut down
during displacement.
Casing Cleanup Spacer
CASING-WASH TM 100 is used to chemically remove the mud and other materials from the metal
surfaces and carry them out of the wellbore. The volume is calculated at 0.5% to 1% of the casing
volume and is mixed in water or brine at 5-8% by volume. The highest concentration is
recommended when the fluid being displaced contains oil or other hydrocarbon additives.
Viscosified Spacer
This high yield point spacer will carry any remaining solids out to the casing or open hole and
prevent contamination of the completion fluid. The spacer volume is based on wellbore
configuration – usually filling 500 to 1000 feet of the largest annular volume.
Filtered Brine
Filtered completion brine should be circulated one full circulation or until cleanliness specifications
are met. Dispose of the spacers as per established procedures.
Oil Based System to Brine
Optional Lead Spacer
50 bbl of mineral or diesel oil can provide a good cleansing action on the casing and remove a
significant amount of debris. This is a cost effective procedure but is optional depending on
capabilities at the rig-site to recover and store the contaminated oil for future use.
Push Pill
Follow the base oil spacer with Spacer/Push Pill. Viscosify and weight up a seawater spacer to 0.2
ppg heavier than the mud. The yield point should be a higher (1.5 times greater) to promote a good
displacement without the commingling of the base oil or mud with the spacer. The volume should
cover at least 1000 feet of largest annular diameter. The density, viscosity and surfactant in the
spacer will help push oily debris out of the wellbore and initiate the water-wetting process. This pill
should contain FLOW-CLEAN TM .
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 6-87