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Two Platforms, Two Shore Approaches, Two Lines And A Hurricane
Platform drilling equipment was reset by Corman Marine, using tugs, barges and cranes to position a 140-drill spread on the north platform and a 330-drill spread on the south platform, along with two 21,000-gallon holding tanks, air compressors, pipe racks, excavator and all the other equipment needed for a project of this scale. Corman also set new 'goalposts'; two pairs of 14-inch steel pilings were set at each platform, with heavy chain draped between each pair to support casings during drilling. The casing pipe was needed to support drill pipe, and to maintain circulation of used drilling fluid without spills into the York River.
With platforms set and goalposts in place, Mears began the water-to-water crossings by installing 220-foot and 130-foot casings of 12-inch welded pipe, installed at the north and south platforms respectively. The casings were set at angles calculated to attain the designed entry angles of the drilling profiles. After drill bits were advanced 600 feet past the casings, specialized casing driver adaptors were used to add an additional 300 feet of wash-over casing to each platform's casing string.
On the Line A platform-to-platform crossing, gyro guidance was again used to get the drill bits within a few feet of each other. But GSTs can't detect other GSTs; therefore, the south platform drilling was put on hold while the north platform drill head was equipped with a Para-Track II guidance system. After a few 'pass byes,' passive magnetic ranging was used to touch bits and achieve a successful intersect.
The drill strings were now tripped back and advanced to the south platform in order to create a continuous drill string. But the north platform drill string was not able to negotiate the angle of the south platform casing. To flatten the angle and make it traversable, the south platform crew installed another 300 feet of 12-inch casing.
With a continuous, 7,300-foot drill string now created, the pilot hole could be expanded to final dimensions. The existing 12-inch casings were used as guides for the placement of new 24-inch wash-over casings, and then removed. Twenty-two-inch reamers (which expand the hole), and swabs (which clean the hole) were used successively to expand the pilot hole and prepare it for product pullback. The swab pass was timed to conclude shortly before product pullback to ensure the best possible pullback conditions.