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5,675-Foot x 72-Inch HDD Bore for 48-Inch Pipe Sets New Record
Throughout the project, the behaviour of the drilling fluid also caused problems. Since the bore was under water and between islands, salt water influx was a problem. Monitoring the drilling fluid showed that the viscosity was suffering because of the high gypsum content of the formation and the salt water influx entering the hole.
After several tests and remembering past experiences, the drilling fluid was changed to a mud that was based on salt water and salt resistant polymers. The use of available salt water also eliminated the need to haul fresh water to the site.
The pull operation for the last bore was completed on July 22. For both pulls the product pipes were filled with water to provide ballast, protect the cathodic protective coating and keep the pull forces at minimum. This and a very smooth and straight bore resulted in very low pull forces (60 to 70 tons) for this length and diameter of pipe. Each pull operation took about 16 hours, with the rate of the water pumped into the product pipe determining the pull speed.