BAKER HUGHES - Drilling Fluids Reference Manual

Baker Hughes Drilling Fluids
meet cuttings discharge criteria in the North Sea. The lower oil/water ratio CARBO-DRILL S.E.A.
system is widely used in the North Sea.
In addition to decreasing the amount of oil associated with drill cuttings, the increase in brine content
has also been shown to reduce the cost of the oil fluid, since less oil is necessary.
Because of the large volume of water present, the fluid system is composed of specifically designed
products. These CARBO-DRILL systems have been designed to cope with the high water content and
to exhibit rheology comparable to more conventional oil-base fluid systems. The proper emulsifiers
and oil wetting agents result in a stable system with no water in the high-temperature/high-pressure
(HT/HP) filtrate. Field and laboratory evidence has shown that the CARBO-DRILL systems can
incorporate additional water contamination with minimal increase in rheological properties and little
or no water wetting of solids, even when water may be temporarily present in the HT/HP filtrate.
The principal emulsifiers used in the North Sea high water content CARBO-DRILL S.E.A. are
CARBO-MUL HT and CARBO-MIX. Field evidence has shown that CARBO-MUL HT/CARBO-
MIX emulsifier’s combinations are synergistic. The ratio of these products is dependent upon the
oil/water ratio, temperature, and fluid density.
System Maintenance
To achieve optimum economics when using emulsifiers and changing oil content, as well as to
minimize the plastic viscosity of the fluid, the oil/water ratio is varied with the fluid density.
The CARBO-DRILL systems are more tolerant of water content than most conventional oil-mud
systems; however, they become less tolerant to large quantities of low-gravity solids as water content
increases. Therefore, drill solids must be controlled. The use of linear motion shale shakers,
preferably with the fluid cascaded from coarse mesh shakers (often referred to as scalping shakers) is
recommended. Field experience has shown that solids contents up to 120 lb m /bbl (348 kg/m 3 or 13.2%
by volume) can be tolerated. However, fluids containing above 120 lb m /bbl (348 kg/m 3 ) low-gravity
solids should be diluted with the non to low solid laden CARBO-DRILL SYSTEM. Ideally, the lowgravity
solids content should be less than 80 lb m /bbl (232 g/m 3 or 8.8% by volume).
The base formulations contain emulsifiers to start a system. However, as drilling commences, drill
solids accumulation and removal, and increases in fluid density, requires increased additions of
emulsifiers and wetting agents. Therefore, the CARBO-DRILL systems must be engineered so that
each system is maintained without it becoming an expensive, over-treated fluid system. Water
breakout and/or HT/HP increases are direct indicators that additional emulsifiers/wetting agents are
required. It is recommended that the HT/HP checks be run every eight hours so that a trend can be
developed. Any increases in HT/HP filtrate or detections of water in the filtrate must be treated
immediately.
MAGMA-TEQ HTHP Non-Aqueous Drilling Fluid System
Increasing demand for drilling deviated HTHP wells in the North Sea area has resulted in the
development of a HTHP oil based drilling fluid with unique suspension properties to avoid commonly
observed density differentiations under extreme conditions. The stringent environmental and
occupational hygiene regulations in the North Sea area also limit the use of commonly used
chemistries for oil based HTHP applications. Baker Hughes Drilling Fluid’s HTHP oil-based drilling
fluid, MAGMA-TEQ is a state of the art response to this need.
During the development of this system several new products were created which include a specialized
high temperature emulsifier; MAGMA-VERT, improved fluid loss chemistry and suspension
stabilizer; MAGMA-TROL and MAGMA-GEL, a high temperature viscosifier which also acts as
a barite sag preventative additive.
Baker Hughes Drilling Fluids
Reference Manual
Revised 2006 5-27