BAKER HUGHES - Drilling Fluids Reference Manual

RESERVOIR APPLICATION FLUIDS
of 5% to 10%, depending upon the type of shale and/or cores being drilled, the system should be
displaced, diluted, or converted to a standard controlled activity CARBO-DRILL ® system.
Mixing Procedures
Because water content is contrary to the design of the CARBO-CORE system, special care must
be taken when mixing and displacing the system.
The mixing tank should be clean and all lines flushed with diesel or a used CARBO-DRILL
system which is then discarded. Pump the required amount of base oil, add the emulsifier and add
the required amount of viscosifiers. The application of heat, up to 180°F (82°C), will increase
dispersion of product, evaporate water, decrease mixing time, and result in a more stable system
overall. The calculated amount of CARBO-TROL ® HT should be added as quickly as possible,
based upon the mixing system available.
After a satisfactory dispersion, with adequate viscosity, has been made, weight material may be
added to obtain the desired density. If additional viscosity is necessary, small additions of
viscosifiers may be used.
Displacement
Because a low to zero water content is desired in this system, the displacement procedure can have
a tremendous effect upon the overall system performance. Ideally, casing should be run and the
cement plug be pumped with the CARBO-CORE fluid.
If this is not possible, displacement prior to drilling out of casing is highly recommended.
Displacement at high flow rates while rotating and reciprocating the drillpipe will minimize water
contamination. In situations where water content must be maintained near zero, displacements have
been made using a standard CARBO-DRILL oil-base fluid to displace the water-base fluid,
followed by the CARBO-CORE system.
Water Contamination
The CARBO-CORE system has proven to be temperature stable even after contamination with
water, as indicated in the figure below. Because the rate of osmotic transfer of water from the fluid
to the shale increases as the water content increases, small quantities of water should not greatly
affect the stability of the shale.
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 6-40