BP stipulated the use of trenchless technology as part of the company’s Tangguh LNG facility expansion.
Tangguh LNG is comprised of six gas fields located in the Wiriagar, Berau and Muturi Production Sharing Contracts in Bintuni Bay, in the Papua Barat Province of Indonesia. The gas reserves were discovered in the mid-1990s by Atlantic Richfield.
As well as operating Tangguh, BP Berau owns a majority of the development (40.22 per cent) alongside partners, MI Berau B.V. (16.30 per cent), CNOOC Muturi (13.90 per cent), Nippon Oil Exploration (Berau) (12.23 per cent), KG Berau Petroleum (8.60 per cent), KG Wiriagar Overseas (1.40 per cent) and Indonesia Natural Gas Resources Muturi (7.35 per cent).
Tangguh started production in 2009, four years after it was sanctioned by the Indonesian Government, and has since operated at design capacity.
The Plan of Development was approved by the Government of Indonesia in 2012 and the final investment decision (FID) to expand Tangguh was made in 2016. The Tangguh Expansion project, worth an estimated US$12 billion, includes the addition of a third LNG train and 3.8 million tonnes per annum (mtpa) of production capacity to the existing facility, bringing total plant capacity to 11.4 mtpa.
In addition, the expansion also includes two offshore platforms, 13 new production wells, an expanded LNG loading facility and supporting infrastructure.
Engineering and construction
Soon after the FID had been announced, Saipem was awarded a contract for the engineering, procurement, construction and installation of offshore facilities, consisting of two unmanned platforms and subsea pipelines.
Another major contract – for the construction of the onshore LNG process train, utilities, offsites, an LNG jetty and associated infrastructure – was awarded to CSTS, a joint venture led by Indonesian contractor Tripatra with Chiyoda, Saipem and Suluh Ardhi Engineering. In accordance with the requirements of the institution that oversees Indonesia’s upstream oil and gas sector, SKK Migas, Saipem committed to contributing to local content enhancement, including through its own Karimun fabrication yard.
In mid-2017 Lucas Engineering & Construction was awarded a contract by Saipem for HDD as part of the expansion project. The contract included HDD installations on the approach to shore, under existing crossings installed more than a decade ago during the initial construction of the LNG facility by a subsidiary of Nacap, a pipeline and HDD contractor.
The new crossings, to be installed under the original pipeline and conduit alignment, bring a 24 inch (610 mm) gas pipeline and two
10 inch (254 mm) casing for the fibreoptic power and data cables to shore. The installations enable gas from two new platforms, ROA and WDA, to feed the development’s newest third LNG train.
Lucas’ Herrenknecht HK400 rig, equipped with 400 t pulling capacity, together with all ancillary gear was mobilised to Surabaya and Sorong in Indonesia for shipment to site from various parts of the world, including New Zealand, Australia, Singapore, Malaysia, China and the US.
An experienced HDD crew was assembled with an emphasis on local content in line with Saipem’s commitment to providing employment to locals.
The installation of the first fibreoptic cable casing commenced in early July 2018. The 2,065 m pilot drill exited in the pre-dredged trench on the seabed and was followed by the installation of casing. Unlike the previous project executed by Nacap, where welded casing was used, Lucas opted for threaded casing installed in single length on the rig with the support of a casing buck up unit. During drilling, pulling force was provided by a winch, located offshore. The winch was mounted onboard the Bayu Laut, the accommodation work barge that was moored close to the exit point.
Upon successful installation of the fibreoptic cable casing, the rig was moved 12 m across to commence the pilot drilling of the 24 inch gas pipeline.
Once the pilot bit exited on the seabed, it was winched onboard the Bayu Laut to allow for removal of the bottom hole assembly and installation of the first reamer. The reaming commenced in stages up to 32 inch (813 mm) diameter.
The hole was temporarily abandoned with a drillstring inside to allow for scheduling flexibility as around this time Saipem’s Derrick Lay Barge commenced work on the platform installations. With half of the 24 inch crossing complete, the second fibreoptic cable casing was installed in a manner identical to the first.
For the second phase of the pipeline installation the drill string inside the 32 inch hole was picked up again – after about three weeks – and worked free to continue the hole preparation for pull back. The 24 inch pipeline, with a polypropylene coating, also has a 30 mm outer coating made of high density concrete. The additional coating protects the pipe and guarantees it will not float once in water or in the drilling fluid.
Once the final 40 inch (1,016 mm) hole was reamed and cleaned to satisfaction, the pull back assembly was laid down on the seabed 320 m away from the exit. Bayu Laut was unmoored and moved to outer anchorage, while the Derrick Lay Barge was moved to its determined location and prepared for recovery of the pull back assembly from the seabed.
With the assembly now inside the barge, the pull head was connected and pull back commenced. A total of 104 double joints at 24.4 m each were welded together onboard the Derrick Lay Barge during the pull back, which took eight and a half days to complete. An average pull of less than 100 t was required to successfully and safely install the pipeline.
Preferencing trenchless technology
As Lucas’ Project Manager, Boris de Koning was responsible for the safe, timely and correct execution of the HDD works. He says BP stipulated the installation needed to use trenchless technology for a myriad of reasons.
“HDD was mandatory for BP,” he says.
“The pipeline had to cross existing lines installed by HDD. It also had to cross under a mangrove area, which the operator preferred was left intact.”
Mr de Koning says the pipeline installation – which was imperative to BP meeting gas supply targets – presented many challenges.
“A major challenge of the project was the remoteness of the site,” he says.
“This was managed by good planning, including contingency plans. In addition, we made sure we had good spares and equipment, and maintenance control, as well as using an experienced crew.”
“Obviously, the pipeline feeds into a new LNG train for BP and BP has a commitment under the sales and purchase agreement to supply gas to their clients in due course, when the project is completed. A failed HDD installation would have jeopardised that commitment.”
Lucas successfully completed the installation between June and November 2018. In August 2018, Lucas Engineering and Construction was acquired by Spiecapag and now operates as a new entity, HDI Lucas. The company draws on the resources and experience of Lucas but additionally will have the resources of sister company, HDI to call on.
HDI is an internationally recognised HDD contractor, headquartered in France but with divisions in Brazil, Mexico and now Australia. HDI Lucas covers the Oceanian and South East Asian markets and currently has projects ongoing in New Zealand, Singapore and Australia.
This article was featured in the Summer edition of Pipelines International. To view the magazine on your PC, Mac, tablet, or mobile device, click here.
For more information visit the HDI Lucas website.
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