BAKER HUGHES - Drilling Fluids Reference Manual

Baker Hughes Drilling Fluids
Standard chemical analyses (pH, alkalinity, salinity, total hardness) must be closely monitored
because at elevated bottomhole temperatures (350°F and above) chemical reactions are occurring
much more rapidly. Physical properties can change radically in a fairly short time.
Rheological parameters need to be closely watched because they affect hole cleaning and
hydraulic parameters. Rheological properties must be checked in a thermal heat cup at 120°F so a
standardized record can be maintained at the rig site. Hot-rolling and static aging of samples
should be done at current bottom hole temperatures to observe thermal stability characteristics.
Pilot testing and thermal testing of fluid samples at projected bottom hole temperatures should be
done weekly to establish responses to possible problems. Fann 70 Viscometer tests can be used to
observe thermal stability trends and formulate responses to problems that will help the engineer at
the well site.
API and HT/HP filtrate trends should be closely observed to see if properties are stable or
degrading from temperature increases and/or contaminants. Dynamic filtration studies can be
performed to simulate dynamic down hole conditions at the rig site. Filter cake formation and
erosion studied under these conditions are more representative of the drilling operation than static
tests. Cake compressibility tests can supplement the aforementioned tests by observing how
different products will affect filter cake quality and change filtration rates.
Advantages and Limitations of the PYRO-DRILL System
There are many advantages to the PYRO-DRILL system. Almost all drilling fluids can be easily
and economically conditioned with the appropriate PYRO-DRILL additives for enhanced thermal
stability. The base fluid should be in good condition prior to treatment.
Listed below are some of the advantages of the PYRO-DRILL system.
• Properly maintained systems are thermally stable to 600°F+.
• PYRO-DRILL fluids are not adversely affected by carbonates, salt water influxes, anhydrite,
or cement provided low-gravity solids values are in the proper ranges for the respective fluid
density.
• The PYRO-DRILL system can provide excellent borehole stability.
• Properly maintained systems do not cause excessive pump pressures to break circulation.
This is especially significant for high-density and high-temperature, deep wells.
• No excessive torque or drag is exhibited with a properly maintained system.
• Properties are easy to maintain with the PYRO-DRILL system.
• PYRO-DRILL systems typically exhibit low corrosion rates. This is due to the reduction in
oxygen content of the fluid by the organic additives acting as oxygen scavengers.
• Well costs can be significantly reduced while drilling in hostile environments because of
previously mentioned advantages.
One component of the PYRO-DRILL system has some minor limitations. PYRO-TROL should
not be used in high hardness fluids (where Ca ++ and Mg ++ ≥ 5000 mg/L) or in lime-base systems
(pH ≥ 11.0 are not recommended because of shrinkage/hydrolysis of monomer chains).
Baker Hughes Drilling Fluids
Reference Manual
Revised 2006 3-65