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HDD Underneath Choctawhatchee Bay Sets Record

Tue November 21, 2006 - Southeast Edition
CEG



Patterson & Wilder Construction Co. Inc. of Birmingham, Ala., and its subcontractor, Michels Directional Crossings of Brownsville, Wis., successfully completed a record breaking 8,400-ft. (2,560 m) horizontal directional drill of the Choctawhatchee Bay for the Okaloosa Gas District May 6.

As proposed and installed by P&W and Michels, this drill is a new record length for an intersect without coming up in the middle. The intersect drill was designed by Patterson & Wilder and Michels to eliminate any possible environmental disturbances to the delicate bay ecosystem. The bay crossing is an integral part of Phase I of the 22.8-mi. (36.7 km) Walton County Pipeline Expansion Project, which will provide natural gas services to Freeport, Fla., and surrounding areas.

Patterson & Wilder prepared the temporary work areas for Michels to set up its drilling rigs on the south and north sides of the bay. Due to the narrow right of way space available along the causeway, the high volume of fast moving highway traffic, and the proximity to the Bay Bridge, concrete barriers and crash barrels were needed to provide a safe work space. The drill pipe was to be strung on north side of the bay, but a second, yet significantly smaller, bridge crossing further complicated the limited work space. Patterson & Wilder crews had to string three separate 2,800-ft. (850 m) sections of 10-in. (25 cm) 0.365-in. (0.9 cm) wall steel pipe. The sections were then welded, visually inspected, x-rayed and coated to ensure the integrity of the line before its installation under the bay. Patterson & Wilder also successfully completed an 8 hour pre-test of the line to 2,950 psig.

To complete the intersect, Michels mobilized 15 employees and placed a 1.2-million-lb. (544,000 kg) rig on the south side of the bay and a 220,000-lb. (99,800 kg) rig on the north side of the bay. After four days of concurrent drilling from both sides of the bridge, Michels precisely hit one end of the pilot hole with the other pilot hole bit without any redundant overlap drilling required, a feat not previously achieved with past intersects. When the south side drill string became stuck, the north side rig was used to push across and assist in freeing the string. This resourceful solution saved valuable time and a potentially catastrophic loss of tools. Michels was able to maintain drilling fluid circulation over the entire length of the drill, another achievement unprecedented at this drill length.

The day of the pullback, Patterson & Wilder provided a 15 man support crew to guide the drill strings into the pilot hole and complete the final welding and coating. After 16 continuous hours, the 8,400 ft. of pipe successfully emerged on the south side of the bay.