Underground Construction - June 2019 - 32

Directional Drilling
Jeff Griffin | Senior Editor

Three Parallel Crossings in Corpus Christi
Hard Rock Directional Drilling has completed three 3,100-foot
directionally drilled crossings of the deep-water navigable ship
channel in Corpus Christi, Texas. The channel extends from the
Gulf of Mexico, through the jetties in Port Aransas and across the
Corpus Christi Bay.
The 12 steel pipelines installed in the three crossings were
needed to carry crude oil to connect the Pin Oak station to its dock
station. The project owner is Pin Oak Terminals, a pipeline and
storage terminal operator. The company's Corpus Christi facilities
currently are under expansion.
The primary contractor for the improvements that included the
channel crossings project was Strike LLC. Hard Rock contracted
for the horizontal directional drilling (HDD) work.
"Although our contract for the bores was with Strike, Hard
Rock worked directly with Pin Oak and Oso Development on
the design, drill plan and consultation to obtain all necessary
permits before the project was ever awarded," said Cory Baker,
Hard Rock general manager.
Baker explained that the project was made in three bores so
the bundles would be manageable for pullback. Each of the three
bundles consisted of four pipes: two 16 inches in diameter and one
each of 20- and 4-inch diameters. The bores were made side-byside, one after the other.
"We used our Vermeer D1000x900 drill rig with 1 million
pounds of pullback and 96,000 foot-pounds of rotary torque," said
Baker. "Strike had to bring several loads of fill to build the pad up
in order for us to be able to set up.
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JUNE 2019 | UConOnline.com

"We made the first bore, moved the rig 15 feet, made the second
bore and moved another 15 feet for the final installation. The pipes
had to be within a designated right-of-way."

Drill parameters
Pipes were installed 100 feet below the channel floor. Water was
60-feet deep, making the bores about 180 feet from the elevation
of the drilling rig. Soil conditions included sand, shell and clay. An
81⁄4-inch mud motor and 8-inch mill-tooth bits were used to drill
the pilot holes.
"Because there were 'S' curves in the horizontal plane in the
underwater bore paths," Baker said, "we needed a steering tool that
had a high percentage of accuracy without a coil. With the three
crossings side by side, accuracy was even more important to ensure
we did not fall into one of the already drilled crossings while making
these turns. We used a gyro steering system supplied by Brownline."
The contract allowed 35 days to complete each pilot bore,
but Baker's team was able to average about 28 days per bore
and completed work ahead of schedule. Pipes were laid out in
a narrow right-of-way and mid-welds were made on all four pipes
in each bundle.
"The exit points," he continued, "were in a very tight and
congested area which caused us to have to design the crossings to
exit at 15 degrees. That presented a challenge for pulling pipe and
getting the proper break over for all the pipes. Strike had to bring
in cranes in order to keep all the pipes separated and at the proper
breakover to correctly enter the hole."
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