Trenchless Technology

OCT 2018

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Page 22 of 91

W W W.T R E N C H L E S S T EC H N O LO GY.C O M 23 Cleaning System with a 300-bbl mix- ing tank and centrifuge — designed for the outfall execution offering full luids circulation and lower pressure for minimal environmental risk in the soft soil conditions beneath the Texas shoreline. This project necessitated tremen- dous planning , preparation and con- idence as project crews dealt with a variety of challenging factors, includ- ing the project 's remoteness, as well as a healthy hurricane season and a prolonged period of working in a con- ined space. VCP, owned by Enbridge and Val - ley Crossing Pipeline LLC , was con- structed to transport reliable sup - plies of clean burning natural gas to the Comisión Federal de Electricidad (CFE) — Mexico's state-owned utility, serving approximately 37 million cus- tomers — to provide natural gas trans- portation services to meet Mexico's growing electric generation needs, as well as to other shippers at delivery points in south Texas. This additional access to vital supplies of clean burn- ing natural gas will promote economic development along the project route and in the region. A portion of this project necessi- tated an installation solution to inter- face the onshore segment at the Texas border to the offshore segment in the Gulf of Mexico. Originally designed as a horizontal directional drilling (HDD) project , the decision by the project owners was made to, instead, use the Direct Pipe method. Using Di- rect Pipe, Laney crews tunneled 4,900 ft from Clark Island in Cameron Coun- ty, Texas, and then thrust an addition- al 1,350 ft of pipe offshore so that the 42-in. steel pipe could be picked up in the Gulf and connected to the Mexico project link. The product pipe for the project consisted of 42-in. OD, with 1,25-in. wall thickness and API-5L x70 steel pipe with fusion-bonded epoxy and an abrasion-resistant overlay. Exten- sive matting was required for the en- try setup and for the pipe to be strung out over the marshlands of south Texas. " With this distance and pipe size, it had never been done before," says Laney vice president of operations Rob Hotz . " We were learning as we were going . It was deinitely an inter- esting one." The Clark Island location is just a few miles north of the Mexico border and the jobsite was remote and extremely dificult to access. " There was no infrastructure in the area and we were right next to Boca Chica State Park and South Bay," says Hotz . " Everything had to be accessed each day through barges — all the equipment , materials and personnel — and transported over water to docks constructed on [Clark Island] where we worked from." With any installation that pushes the limits of what has previously been accomplished, there are numerous challenges throughout design, project planning and construction. The deci- sion to go with Direct Pipe vs. HDD was made early. With HDD, there were concerns with the geometry of the preliminary drill and the location of the breakthrough of the pipeline into the Gulf of Mexico. The option of us- ing the Direct Pipe method alleviated those concerns, as well provided a much more cost-eficient construc- tion method for project owners. Using Direct Pipe also lowers annular pres- sure acting on the surrounding sub - surface formation, thereby reducing the risk of inadvertent returns. Direct Pipe combines two proven trenchless methods: microtunneling and HDD. Unlike HDD, Direct Pipe uses a microtunneling boring ma- chine (MTBM) and instead of being a multi- step install process, it 's a single step. Among the beneits over micro - tunneling is that there are no deep shafts for launching and installing a pipe section. The pipe is welded prior to installation. For this particular project , using Direct Pipe was the right solution. " Direct Pipe beneited this project due to the minimum frac-out risk vs. HDD in these environmentally sensi- tive conditions," says Gerhard Lang , business development manager at Herrenknecht AG - Utility Tunneling Division. " The Direct Pipe technology is primarily considered when HDD is not applicable or the geological and hydrological conditions indicate too - high-of-a-risk for HDD." Hotz further explains that the ma- rine support used on the project would have been signiicantly more challeng- ing , costly and time-consuming using HDD. Laney worked extensively with Herrenknecht to implement an execu- tion plan with the correct equipment design. Laney utilized a custom-built Herrenknecht HK750PT thruster and clamp with a Herrenknecht AVN1000, along with its custom-built Derrick Direct Pipe Cleaning System that al - lowed crews to achieve proper returns throughout the project . Finally, the umbilical system was modiied to a longer length, along with the internal conined entry setup. Project mobilization started in mid- September 2017, delayed for a period after Hurricane Harvey made landfall the week that the project was initially scheduled to begin. Crews, working 24/7 for the entirety of the project , began tunneling in early November 2017, with the MTBM surfacing in the Gulf of Mexico on Dec. 2. Laney crews thrust the additional 1,350 ft of pipe through the tunnel to enable the off- shore barge to pick up and layaway through the Gulf. After demobiliza- tion, crews were off location in early January 2018. The project was completed on time and within budget . Challenges This was the irst project that Laney utilized its custom-built cleaning sys- tem. Hotz notes that one of the big- gest challenges on a tunneling project is removal of spoils, which are then recycled and reused. " We have to get the spoils out of the luid and recycle it , sending back downhole to keep [the Sections of the pipeline are loaded onto a barge for the Valley Crossing Project.

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