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Another HDD Intersect Record Set
A horizontal directional drilling (HDD) installation completed last summer under the Sabine River and nearby swamplands is believed to be the longest ever made at 11,065 feet.
“We have been unable to find record of a longer HDD project,” said Boyd Simon, P.E., division manager for Digco Utility Construction d/b/a Ranger Field Services, subcontractor responsible for the HDD segment.
The crossing was a segment of a new 12-inch diameter steel natural gas transmission line running 139-miles from Liberty, TX, to Eunice, LA. WHC Inc. was the pipeline contractor; project owner is Crosstex Energy Services.
The installation was made by the intersect method with two HDD units: one on the entry side, the other at the exit end. Intersection was completed on the first attempt.
Simon said pilot holes were drilled with a Mears 1.2 million-pound pullback machine from the entry side and a Vermeer D330x500 with 330,000 pounds of pullback working from the exit end. The entry rig pilot hole was 6,308 feet and the exit side pilot hole was 4,757. True vertical depth of the installation was 92 feet from rig elevation, 71-feet below the river bottom.
“Surface conditions consisted of mostly sandy ground on the exit side and swampy/soft ground on entry side,” Simon continued. “WHC cleared wooded areas and constructed 200-by-200-foot pads at entry and exit locations. Mats were necessary for a board road at the entry location due to the long distance to the nearest roadway.”
Pilot holes and the intersect were completed in 12 days, plus four days for the entry-side rig to push the drill bit to the exit side, Simon said. Pilot holes were drilled with 11 3/4-inch bits and Adtech eight-inch mud motors were used. Twenty-two inch split-bit hole openers made one pass followed by one 18-inch swab pass. Reaming was completed in seven days operating both drill rigs 24 hours a day with two crews on each rig, working 12-hour shifts.
To install casing, complete the intersect and remove the drill bit from the ground required 19 days.
“To make the intersect of the two bores, the larger entry rig drilled as far as possible without losing steering capabilities,” Simon explained. “We had an island to lay out 1,500 feet of coil. Surveying was time consuming and at times difficult due to the heavily-wooded lands and swampy areas. Still, we were able to layout five coils.”
Although there was space to lay out and weld the entire section of pipe for pullback, it could not be laid out straight because of large trees and swampy areas.