BAKER HUGHES - Drilling Fluids Reference Manual

RESERVOIR APPLICATION FLUIDS
Run the workstring to bottom and condition the mud.
Displace the OBM/SBM out of the casing with seawater/drill water
Pump a 50 bbl spacer of base oil or synthetic fluid before the seawater. This spacer is optional but
can be recovered in the OBM/SBM.
Push Pill
Follow the base oil spacer with a Spacer/Push Pill. Viscosify and weight up a seawater spacer to
0.2 ppg heavier than the mud. The spacer viscosity should be 1 to 2 times the mud viscosity. The
volume should cover at least 1000 feet of largest annular diameter. The density, viscosity and
surfactant (FLOW-CLEAN TM ) in the spacer will help push oily debris out of the wellbore and
initiate the water-wetting process.
Seawater Flush
Follow the spacer with seawater for two wellbore volumes.
Water-Wetting Spacer
FLOW-SURF TM or FLOW-SURF TM PLUS will chemically detach, dissolve and remove the mud
residue from all casing surfaces, out of the wellbore and finalize the water-wetting process. Typical
concentration of solvent is 5-10%.
Volume is determined and optimized based on surface area of tubulars, saturation volume,
Reynolds number, annular velocity, contact time and pump rate. Normally spacer volume is 1000
to 2000 ft of the largest annular volume. Contact time required is normally 2.5 to 10 minutes.
Viscous Spacer
Viscous Xanthan Gum / Seawater spacer between FLOW-SURF TM spacer and filtered brine.
Volume = ± 1000 feet of largest annular diameter.
Clean Brine
Follow the viscous spacer with clean brine and filter to operator’s turbidity requirements.
Direct Displacement
A direct displacement may be defined as one that uses a series of relatively small spacers between
the original drilling fluid and the next fluid system, i.e. drill-in fluid or clear brine. This method is
often favored because the rig time (cost) is reduced. Improved procedures and solvents have
advanced significantly, reducing the number of spacers required to clean the open-hole and casing
effectively.
A direct displacement differs from an indirect displacement, primarily by omitting the
displacement to seawater step. The direct displacement utilizes very effective solvent and
surfactant spacers to clean and water-wet the casing so that you can “directly” displace the
wellbore to the final displacement fluid in a single operation.
Water-Base System to Brine
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 6-86