Underground Services Australia faced some tough environmental and technical challenges when it tackled a horizontal directional drilling project on Barrow Island in the state’s North West. USA’s success in dealing with those challenges was recently acknowledged when the company won a Civil Contractors Federation WA 2008 Earth Award for Category 2 (projects valued between $1 million and $5 million). The partners in the $20 billion Gorgon gas project contracted USA to drill a 480m-long exploratory pilot hole from the island to an exit point in the sea bed at a depth of 12m. Geological data collected by USA is being used by the Gorgon partners to plan for the pipelines that will carry gas to the liquefied natural gas plant to be built on the island. Three months of planning went into ensuring all issues were identified and assessed before work commenced at the site. Barrow Island is an A Class reserve, and the preparatory work required to meet quarantine restrictions was extensive. Core holes had to be drilled in the sub frames of machinery being sent to the site to ensure the equipment met quarantine standards. “A lot of machinery, including the drill rig, was shrink-wrapped before being transported by road to Dampier and then barged across to the island,” he said. “Everything had to be spotlessly prior to arriving on site.” Careful planning by the USA team resulted in a 50% reduction of expected land clearing at the HDD site. The path the team used to get from their camp to the worksite was also used by a population of sea turtles. Special mats were laid on the path, allowing the turtles to cross the path safely. HDD is traditionally used for the installation of underground infrastructure such as water and gas pipelines or underground cables. For this project, however, USA had to modify the set-up of the drill to allow for the gathering of data. The data captured needed to be very accurate as the information would provide an in-depth assessment of the geological formation beneath the ocean bed in the vicinity of the proposed future pipeline shore crossings. One of the advanced techniques used on the project was the use of biodegradable drilling fluids. The likely porous condition of the rock could have allowed drilling fluids to “frac out” and be released into the sea environment. Teaming with the Australian Mud Company, USA implemented the use of vegetable-gum based mud’s that turned out to be both effective in maintaining a high-performance drilling operation as well as an environmentally benign impact.
