As most Trenchless Australasia readers will know, HDD uses a drilling rig to drive and direct a string of drilling pipe down beneath an obstacle and up the other side. Using sophisticated position-locating technology and controls, a skilled driller can precisely control the position of the pipe. Once the pilot hole is complete, the hole is enlarged by reaming to the final size, usually about one and a half times the size of the product pipe being installed. Finally, the product pipe, typically steel or HDPE, is pulled or pushed into the hole by the drilling rig.
The first successful HDD river crossing was completed in 1974 in the USA. Australia’s first HDD project came later that decade, a landfall for one of Esso’s Bass Strait pipelines near Longford in Victoria. A drilling rig and crew were brought in from the USA for the job.
At the time, AJ Lucas was well-established as a pipeline contractor, so HDD was a natural adjunct to the company’s work. Andy Lukas had learned about HDD while working in the United States.
“I could see this technology had great potential in Australia and arranged joint ventures with US drilling contractors to bid on projects here. But the economics simply didn’t work – the costs of bringing a rig and crew to Australia were just too high.
“It was clear that there needed to be a rig in Australia. So we set about building it.”
This 70 tonne rig was completed in 1990 and had its first job in August that year, installing high pressure oil pipelines under Sydney Airport.
More work followed the success of this project – fuel lines at Brisbane Airport, sewer mains connections in the Blue Mountains and a variety of other crossings.
The value of HDD for pipelines was firmly established by the 1,375 km Moomba to Sydney Ethane Pipeline built in 1995-6. Higher environmental standards wouldn’t be met by older techniques for 18 crossings. With other crossings, successful contractors had the option of using HDD. In all, 28 crossings were done by HDD, taking the pipeline under Sydney Airport, Botany Wetlands, several major road junctions, rivers, railways, water catchments and gorges.
“The pipeline simply couldn’t have been built without HDD to cross these obstacles,” said Andy. “The diversity of the challenges we were able to meet really showed the pipeline industry what HDD could do. And the reliability and cost-effectiveness of the technique was solidly established with this series of crossings.”
Challenges continued to be met by the technology
“Another opportunity for HDD was developed through a number of drills in Sydney and the Blue Mountains for Sydney Water. HDD enabled them to completely rethink sewer installation. With its small site needs, HDD eliminated the traffic disruption caused by trenching. In many cases, HDD let them install a gravity sewer line rather than a conventional trenched line, eliminating regular pumping stations.”
The biggest challenge to date came in 2000 when Lucas won the job – against international competition – of installing a new water mains across Hong Kong Harbour. Taking two 820 mm pipelines through
1,369 m of granite, this was right at the edge of the technology.
Lucas succeeded with the crossing and quickly won an even larger project installing conduits to carry high voltage power mains under Hong Kong Harbour. This project, the largest HDD project ever, and the only one with up to four over-200 tonne rigs working simultaneously, was also a success and confirmed Australia’s position in the Asian HDD market.
A new challenge – coal seam gas
While HDD was becoming a well-established technology for installing utilities infrastructure, a different kind of drilling was going on underground.
“Coal seams are often loaded with methane gas, presenting an explosion and asphyxiation hazard for miners. To drain the gas, underground drilling rigs have been used for a number of years. These did the job, but held up mining and presented their own hazards. The gas also creates a greenhouse pollution problem as it is discharged to the atmosphere,” said Andy.
“We believed that HDD expertise could be applied to drill directly into coal seams from the surface to drain and capture the gas.”
Research to develop these new techniques was undertaken by CRC Mining, the cooperative research centre for mining technology and equipment, with Lucas as one of the commercial partners. These Australian-developed techniques have proven successful and the mining industry is taking advantage of this “surface to in-seam” or SIS
Longer, more accurate drills
According to Andy, “Australian HDD is among the world’s most advanced. Of the 75 over-1,000 m drills worldwide, 22 have been done by Australians. We’ve set almost all of the current records: for longest gravity sewer, longest pressure sewer, longest landfall. Many new guidance techniques, drill bit designs and mud formulations have been developed or refined here.
“And we are still extending our capabilities. We believe drills of 5,000 m and over are possible – based on careful engineering analysis, not wishful thinking.
“I’m looking forward to continuing development to see the capabilities of HDD continue to be extended. And I believe the pressures of environmental protection and cities’ need to install new infrastructure will ensure there’s a market for these capabilities.”