Freeport LNG’s existing regasification terminal needed a 9.6-mile long, 42-inch send-out pipeline to connect to customer gas lines at the Stratton Ridge meter station. The pipeline is now being reconfigured to carry feed gas from Stratton Ridge to the pretreatment and liquefaction facilities.
There will be a pair of new 42-inch connector pipelines tying in to the existing 42-inch line. One will feed untreated gas to the pretreatment facility for removal of elements that inhibit proper liquefaction, such as CO2, water and nitrogen. The second 42-inch connector will send the treated and compressed gas back to the existing 42-inch line and then on to the liquefaction facility. Each new interconnect represents about 2,100 linear feet of pipe that requires horizontal directional drills (HDD) for most of their length.
HDD is a method used to lay a pipe under a barrier in the pipeline's path, such as a road, body of water or levee. In this case, the new pipe will travel under both a United States Corps of Engineers storm levee, a road (County Road 690) and under the existing 42-inch pipeline before it ties into it. The new pipe will be laid 70 feet below the levee and road— a depth maintained for 300 feet on both sides of these structures to avoid hydro-fracturing that could damage the levee structure.
Before the three-step HDD process begins, the 42-inch pipe is welded together in a staging area just outside of the drilling point.
The first step is to drill a pilot hole, roughly 10 inches in diameter, along the path of the drill. Once that pilot hole is completed, the first ream to increase the diameter of the hole is made, which expands the diameter
Stratton Ridge Meter Station
42-inch Pipe Pull
Original 42-inch Pipeline Construction
to about 30 inches. The second ream achieves the final diameter desired, which is 54 inches—and larger than the pipe diameter in order to reduce friction during the pull.
The pipe is then pulled through the reamed hole using the drill pipe attached to a swab. The swab turns and injects drilling mud into the reamed hole ahead of the pipe to
remove remaining cuttings and to keep the path clear. During the pull back, a precise amount of water is also introduced into the 42-inch pipe to further reduce friction, as the pipe will float when it encounters the drilling mud. The goal of the water is to achieve neutral buoyancy of the pipe.
The HDD Process
Making the Tie-in
The final step will be the tie-ins at the existing 42-inch pipeline. "We are having to make the tie-in in essentially a very difficult spot just to the east of County Road 690 and the storm prevention levee," remarked Project Manager for Liquefaction Pipeline Expansion Mike Matranga. "As a result, we're going to have to probably sheet pile and dewater the area, and it's going to be a quite significant excavation project to be able to get in there to tie-in to two places into that line."
Shortly following the 42-inch HDD are several other pipeline installations, which include a boil-off gas pipeline, a nitrogen pipeline, a natural gas liquids pipeline and several miles of fiber optics cables for transmitting operational data, communications, internet, leak detection and security detection along the right of way between the pretreatment and liquefaction facilities.