Two Platforms, Two Shore Approaches, Two Lines And A Hurricane

By Angus W. Stocking | December 2013, Vol. 68 No. 12

Meanwhile, after the 12-inch casing was established for the south shore approach, Mears moved an American Augers rig with 140,000 pounds of pullback force and supporting equipment into location on the north shore. The north shore-to-platform crossings were 5,845 feet long with a 32-degree bend in the ROW. These were drilled as intersect crossings with the intersection point about 3,500-feet north of the platform, just on the platform side of the horizontal curve. A duel guidance system was used to achieve intersection on the north shore Line A crossing. Working from shore, Para-Track II was again used with a surface steering coil.

But passive magnetic ranging wasn't a good solution in the York River's main shipping channel, since large ships and barges could cause magnetic anomalies. A gyro steering tool (GST) was used instead. This system combines optical gyroscopic sensors and sensors with World Geodetic System (WGS) latitude and longitude. The two methods successfully brought the two drill bits within a few feet of each other and passive magnetic ranging was used to close the gap. With connection achieved, the drill strings were pulled back and advanced to the platform until a continuous drill string stretched from shore to platform. Two American Augers 140,000 pounds/pullback spreads then worked together to ream the desired 22-inch hole and pull the product bundle.

This completed the shore-to-platform Line A crossings. Equipment was then shifted 20-feet laterally and essentially the same procedures were implemented for the Line B crossings, except that GST wasn't needed for the north shore intersection. Instead, a 10-gauge steering wire was run through the already installed, Line A’s, three-inch HDPE, off which Para-Track II was able to track and offset precisely.

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Long crossings
Though difficult, all four shore-to-platform crossings were achieved as planned. But the 7,300 foot platform-to-platform intersect crossings were even more challenging. Not only were they extremely long for HDD water-to-water crossings, but Mears Group also had to contend with installation difficulties, an abrasive river bottom and a tropical storm that forced evacuation mid-project. But 'unexpected' difficulties actually are expected in projects of this size; Mears Group's project team was well aware that challenges would arise and when they did, they reacted calmly and rose to the occasion.