Esso’s Longford Gas Plant, south of Sale in Gippsland, Victoria, provides the majority of the state’s natural gas for domestic, commercial and industrial use.
Esso are further developing the facility with the construction of a new gas conditioning plant.
To power the expansion, two major substations, located 1km apart on opposite sides of the plant, needed to be connected by ducts to house high voltage and related cables.
However, major surface infrastructure – the gas and crude oil processing plants themselves – lie between the two substations. Esso wanted the cable ducts to go under the plants. It was a classic opportunity for Geotech Drilling to propose the use of Horizontal Directional Drilling.
Significantly, the project had to be completed with no disruption to any production operations. The whole plant remained live, which meant the site was extremely volatile and potentially very dangerous.
It was a complicated brief where safety was absolutely paramount, and where it was anticipated that the existing infrastructure would interfere with the magnetic signals that control the steering of the drill. Fastidious consideration had to be given to issues of general electrical safety. All equipment had to meet with the requirements of the strictest guidelines.
After exhaustive consideration and planning, Geotech Drilling developed an approach and were successful in winning this HDD project.
Work began in December 2012.
Geotech designed and built the Thrust Block to which the Gallagher 600 HDD drill rig was anchored, and managed the design of the bore profiles and cable duct selection.
The project scope consisted of the drilling of 5 x 1 km bores at a depth of 20-25m.
The first phase of the project was to drill an 18" diameter bore to house a 'mud return line', being a DN280 HDPE conduit which is used to transfer drilling fluid from the exit side of the bore to the recycling plant at the entry of the bore.
The other four bores, 26" in diameter, each 1km long, were drilled with a 3m separation at the entry point, running parallel along the alignment. Each bore hole was drilled in a number of passes, the first being a pilot hole which was then enlarged by subsequent reaming passes to a suitable size to facilitate the installation of a bundle of four DN160 HDPE conduits with a mass of 32t.
The accuracy of these boreholes needed to be precise (absolutely) given the significant infrastructure above the boreholes. This infrastructure and pipework created a number of challenges in drilling the pilot holes due to the interference it created to the steering system, as had been anticipated.
The project was successfully completed on time, with the final bundle installed on 8 May 2013.