HDD helps secure LNG supplies

The Queensland Curtis liquefied natural gas (QCLNG) and Australia Pacific LNG (APLNG) export pipeline crosses from the mainland to a liquefaction plant on Curtis Island at The Narrows, a waterway about 10 km north of Gladstone, Queensland.

Horizontal directional drilling (HDD) has been used on the creek section of The Narrows crossing. The drilling rig used for the two crossings was an American Augers DD1100RS.

The boreholes carried out along the proposed HDD section showed very soft to soft Quaternary sediments, overlying very stiff to hard or dense to very dense Quaternary-Tertiary silty sandy clays or silty sands with some gravels. This posed a challenge in selecting the right reaming tools for the variety of soils and formations.

The pilot holes on the project were drilled with a mud motor supplied from TRANSCO Mfg.

Selecting the right reaming tools for the variety of soils and formations proved difficult. For the two larger steps 58-inch and 62-inch project specific tools were designed and ordered in close cooperation with TRANSCO Mfg. from Adelaide. Due to the buoyant nature of these tools they were light enough in the borehole to prevent them from getting bogged and, equipped with hole opener-type milled tooth roller cone cutters, they had the capacity to work with all kinds of formations and soils.

McConnell Dowell and Consolidated Contracting Company Joint Venture (MCJV) are installing both pipelines. QGC are project managing MCJV on the construction.

QGC’s pipeline is laid along the same trench in The Narrows as the pipeline for another LNG proponent, the APLNG joint venture between Origin and ConocoPhillips.

Both projects extract coal seam gas from southern Queensland production wells, to be converted to LNG at Curtis Island for shipping overseas.

The project, which has been under construction since 2010, will provide cleaner hydrocarbon energy for export markets from 2014.

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