BAKER HUGHES - Drilling Fluids Reference Manual

RESERVOIR APPLICATION FLUIDS
Water-Wetting Spacer
FLOW-SURF TM or FLOW-SURF TM PLUS will chemically detach, dissolve and remove the mud
residue from all casing surfaces, flush 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
ft of the largest annular volume. Contact time required is normally 2.5 to 10 minutes.
Viscous Spacer
Viscous Xanthan Gum / Seawater spacer between A-312N spacer and filtered brine.
Volume = ±1000 feet of largest annular diameter.
Clean Brine
Circulate the filtered completion brine for one circulation or until cleanliness specifications are
met. Dispose of all spacers as per regulations.
General Displacement Considerations
The displacement of mud from an annulus is a complex physical phenomenon. The main driving
forces, which can be used to enhance the displacement, are:
• fluid viscosity and density
• pump rate and frictional forces
• circulation of fluid
High pump rates will nearly always be better (even in laminar flow); they reduce the boundary
layer thickness on the casing wall. Turbulence is best to ensure 100% access of the clean up pills. It
is recommended to use circulating sub to allow higher flow rates.
In deviated wells the eccentricity of the displacement string reduces displacement efficiency and
rotation and/or reciprocation is crucial for effective displacement. As steel surface is getting water
wet, the effectiveness of pipe rotation may be diminished. If Advantage Torque and Drag
simulation indicates high torque, it should be programmed to use friction reducer additive in the
displacement fluid.
Displacement must not stop once pills are in the annulus. Even very short stoppages will allow
fluids to mix and increase the interface. Interfaces between fluids also increase with hole angle.
Circulate to warm mud and use fine shakers when possible. At low temperature (