BAKER HUGHES - Drilling Fluids Reference Manual

Oil / Synthetic Fluids
returns may occur when drilled with an oil-base fluid. Oil-base fluids, because of their low leak-off
values, can act as efficient fracturing fluids.
6. Disposal Problems
Oil-base fluid cuttings may have to be cleaned before dumping. Some environments require that
cuttings be sent to proper disposal areas. Also, whole fluid cannot be dumped. Therefore, if solids
need to be reduced, dilution is the only answer. Oil-base fluid volumes only increase. Eventually the
oil-base fluid must be disposed of, possibly at considerable cost.
7. Solids Control Equipment
Oil-base fluids have inherently higher viscosities than water-base fluids. This increased viscosity,
combined with the need for oil to dilute during the centrifugation process, results in less than effective
solids removal. See Figure 5-22 thru for the recommended solids control equipment configuration.
8. Hole Cleaning
Hole cleaning is more difficult with oil-base fluids. Some reasons for this are – (1) no cuttings
disperse into the fluid as with water-base fluid, requiring larger cuttings to be removed; (2) oil fluids
are more Newtonian in behavior than water-base fluids; and (3) oil-base fluids have less thixotropic
behavior than water-base fluids.
9. Rig Cleanliness
Extra effort is required to keep a rig clean when oil-base fluids are used. Special dressing areas, steam
cleaners on the rig floor, etc., are required.
10. Special Skin Care for Personnel May be Required
Prolonged skin exposure to OBM and SBM results in oils being removed from the body, resulting in
dry and cracked skin. Proper hygiene and skin moisturizers are required to alleviate this situation.
11. Hazardous Vapors
As hot oil-base fluid flows across high-speed shaker screens and circulates in fluid pits, toxic
hydrocarbons may be released. Therefore, shaker and fluid pit areas must be adequately ventilated.
12. Effect on Rubber
Oil-base fluids can cause either shrinkage or swelling of normal rubber parts. Therefore, it may be
necessary to change out blowout preventer (BOP) rubber components, and the Hydril, etc., to oilresistant
rubber such as Nitrile. Diesel is worse than low-aromatic oils in this respect. Drill pipe
rubbers will also need to be replaced. Depending on the base fluid used, shaker bonding polymers
may also be negatively affected.
13. Fire Hazard
Since the oil used in oil-base fluid can burn, extra precautions are required to prevent a fire.
Additional gas, smoke, and fire detector and protection devices are necessary, including sealed electric
motors and sparkless switches and controls.
14. Special Logging Tools Required
Resistivity logs do not work in an oil-base fluid environment.
Baker Hughes Drilling Fluids
Reference Manual
5-4 Revised 2006