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The Hibernia Project

The Dowell Drilling Fluids Team on the Hibernia project, off the coast of Newfoundland, faces some interesting challenges. Since the platform is located in an environmentally sensitive area, discharges to the sea had to be carefully monitored.

There are three major types of drilling fluids: water-based mud (WBM), oil-based mud (OBM) and synthetic-based mud (SBM). The drilled cuttings from WBMs are much less damaging to the environment than the other two and are normally discharged to the sea. However, water-based systems are not always as effective as oil- or synthetic-based fluids, especially for solving the problems associated with these particular wells.
 

In the most recent wells a combination of water-based and oil-based muds were used. WBM was used early in the drilling process. Then OBM was substituted as the well got deeper and reached the limit of the WBM, in terms of lubricity and well-bore stabilization.

Since OBMs can be toxic to marine plants and animals, their use is normally tightly controlled. For the Hibernia project , the cuttings from the mud were washed on the platform in order to remove the oil before these were discharged into the sea. This washing process took time and proved to be a factor limiting the rate of drilling.

In the future, government legislation may allow for the discharge of cuttings using SBM, which exhibits similar performance to the OBM, but has a better environmental profile. Although the initial cost of the fluid will be approximately double that of OBM, substantial time and dollar savings will be achieved owing to the fact that these cuttings do not have to be washed.