MacDow gets creative with HDD in Thailand

Construction News

Approximately two hours south of Bangkok, the McConnell Dowell pipeline and horizontal directional drilling crews have been working on two gas pipeline projects for the PTT Public Co Ltd – the IRPC Pipeline and the Fourth Transmission Pipeline Interconnector Project.

McConnell Dowell began work for PTT Public Co Ltd early in 2010 on the two pipeline projects. The first of these to get underway was the IRPC Natural Gas Pipeline Project consisting of a 24 inch pipeline located primarily in the road easement beside Highway 36 in Rayong Province.

With most of the right-of-way in reclaimed land, shallow ground conditions were not favourable for conventional open-cut pipeline installation. Due to the existence of a number of existing parallel, large-bore pipelines in the 20 m wide easement, and with many sections of the alignment encompassing a roadside open-drain and canal system, horizontal directional drilling (HDD) was used extensively to complete the project.

Trenchless technology was used to install 11 km of the 20 km gas pipeline, and further ducts for the installation of fibre optic cable were also installed in separate parallel drilled crossings.

The McConnell Dowell HDD crew, using its American Augers DD625 rig, completed three major crossings, including a 1,907 m crossing, which required an intercept procedure to be used in the poor ground conditions.

One rig drilled an 1,800 m pilot hole from one side of the crossing. A second rig, located at the planned exit point, drilled the remaining distance and installed a casing pipe to allow the first rig to safely push out to exit.

Under the direction of HDD

Construction Superintendent Shayne Hicks, the McConnell Dowell crew also manned externally hired equipment and supervised subcontract HDD crews to complete works on the IRPC Project while the company’s 300 t capacity DD625 drilling rig moved to initiate works on the nearby Fourth Transmission Pipeline Interconnector (FTPI) Project.

The FTPI Project requires the installation of one 36 inch and two 42 inch pipelines in the same easement. The McConnell Dowell DD625 rig has now completed all 14 HDD crossings originally planned for this machine. A larger capacity rig has also been mobilised to site to commence three further 1,400 m long crossings.

At the time of writing, the DD625 rig was being relocated to work in tandem with a larger rig to complete the last of these crossings. This will result in 12.5 km of the total 30 km of large-bore pipe being installed by HDD methods on the FTPI project. Of this 12.5 km, eight 6 inch fibre optic ducts totalling 4,810 m, six 36 inch crossings totalling 3,530 m, and eight 42 inch crossings totalling 4,785 m are to be installed.

Continuous 24-hour drilling operations have been carried out over the past 12 months on these two projects, with up to four HDD rigs operating at the same time – an enormous effort by the HDD team. The success of both projects has, to a large extent, been due to the close co-operation from the McConnell Dowell pipeline construction crew to provide welded and pre-tested pipe strings at numerous locations to allow continuous drilling operations.

With the IRPC gas pipeline now successfully commissioned, the HDD crew is looking forward to a well-earned break as its equipment is mobilised to Queensland, Australia, later this year to tackle more 42 inch diameter crossings on recently awarded LNG projects.


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