Two drilling mud base fluids are reviewed - the semisynthetic PureDrill HT-40 and the fully synthetic fluid PureDrill IA-35. The former is targeted for on-shore applications whereas the latter is used in the more environmentally sensitive offshore and on-shore areas.
PureDrill HT-40 is an environmentally superior alternative to diesel; it is non toxic to animals and plants and degrades at a much faster rate than diesel using standard land farming practices. At the same time, despite the radical difference in composition, it is possible to formulate drilling muds for on-shore applications using the same additives as those used to formulate diesel based muds. Additionally, it has been shown that it is possible to drill just as fast with muds based PureDrill HT-40 as it is with diesel mud.
Because PureDrill HT-40 has extremely low levels of aromatics and does not possess the very light C7 - C10 hydrocarbons it is far superior to diesel in term of human health and safety. In further contrast to diesel, PureDrill HT-40 is essentially free of carcinogenic polynuclear aromatics.
Petro Canada manufactures two drilling mud base fluids - PureDrill HT-40 is a semi-synthetic fluid and is designed for on-shore use while the synthetic PureDrill IA-35 is targeted for offshore drilling applications. The latter fluid is more compositionally pure so as to accommodate the more stringent offshore regulatory requirements.
PureDrill HT-40 is composed of a blend of severely hydrocracked low tox mineral oil and a synthesized isoparaffin fluid while PureDrill IA-35 is exclusively composed of the synthesized isoparaffins. Severe hydrocracking serves to eliminate the aromatic molecules along with other undesirables such as sulphur and nitrogen containing molecules. The synthetic portion of the PureDrill HT-40 is manufactured through a process known as hydroisomerization and deep hydrogenation.
The resulting PureDrill HT-40 and PureDrill IA-35 fluids are highly enriched in paraffins. In the case of PureDrill HT-40 polynuclear aromatic levels are <100 ppm. Furthermore, PureDrill HT-40 has an inherent low pour point of < -33 ° C, which is important for drilling in cold weather conditions. The typical physical and compositional properties of the two drilling fluids are shown in Table 1.
PureDrill HT-40 is compositionally distinct from diesel; it has significantly lower aromatics content than the oils that were traditionally used for drilling in Western Canada. The preference for diesel-like drilling fluids stemmed from the low product cost of diesel and the preconception that diesel offers the ultimate in drilling performance. It was assumed that other types of drilling fluids could not achieve the penetration rates observed with diesel. We have developed data which very convincingly shows that this is not the case.
As far as the economics are concerned, it is true that the unit price of diesel is less expensive than a product as compositionally pure as PureDrill HT-40. At the same time a holistic analysis reveals that PureDrill HT-40 is indeed cost effective and rivals the total costs incurred through the use of diesel based mud systems.
