BAKER HUGHES - Drilling Fluids Reference Manual

Baker Hughes Drilling Fluids
Polymers
Several polymers now have application for use in oil-base drilling fluids. These polymers increase
fluid carrying capacity, in both diesel and mineral oil systems, and extend the viscosity temperature
stability to in excess of 500°F (260°C). Polymers used, include elastomeric viscosifiers
(CARBO-VIS TM HT), lightly sulfonated polystyrene polymers, fatty acids, and various dimer-trimer
acid combinations.
Asphalt / Gilsonite
Asphalt is a petroleum-derived colloidal gel composed of colloidal asphaltenes, polar aromatics
(resins), and oils (see Figure 5-20).
Figure 5-20
Macrostructure of Asphalt
The most commonly encountered are those that are naturally present in crude, gilsonite (a mined
product), and blown asphalt. The active components are the asphaltenes. Quality asphaltenes are
highly-associating and form micelles which are thermally stable.
The primary use of asphalt is for fluid loss control. The concentration used is 1 to 15 lb m /bbl (2.9 to
42.8 kg/m 3 ). Asphalt also functions as a shale stabilizer at 5 to 15 lb m /bbl (14.3 to 42.8 kg/m 3 ). When
used at higher concentrations, such as ≥ 40 lb m /bbl (114 kg/m 3 ), it functions as a viscosifier by
increasing the base fluid viscosity.
Quality asphalt is relatively cheap, resistant to electrolytes, alkaline hydrolysis, and is an excellent
fluid loss control material. Asphalt also has good thermal stability. The cake is soluble in most crude
oils, so is somewhat self-cleaning when producing the well.
Baker Hughes Drilling Fluids
Reference Manual
Revised 2006 5-25