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Over the past decade horizontal directional drilling (HDD) has played a prominent role in Australia’s oil and gas sector, with many blue chip resource projects utilising HDD for construction or installation of upstream assets. However, the use of HDD in the oil and gas sector can differ significantly between utility and civil infrastructure counterparts. One individual who has worked on both upstream HDD projects and utility projects is Charles Stockton of Stockton Drilling Services. Specialising in HDD engineering and project management, Mr Stockton’s company has provided services such as QC inspection, risk management, feasibility studies and HDD supervision for Chevron’s Gorgon Project, ExxonMobil’s Longford Gas Conditioning Project, BG Group’s QCLNG project and Arrow Energy’s Curtis Island LNG and Bowen Pipeline Projects. Upstream vs. utility Working for both clients and contractors alike, Mr Stockton regularly engages with both sides of the HDD upstream industry. Comparing HDD’s use between the oil and gas and utilities sectors, Mr Stockton told Trenchless Australasia that oil and gas projects tend to be more complex in size, scale and environment. “For example, the pipeline for the Gorgon shore approach was 86 cm in diameter with a wall thickness of 42.5 mm and the complete string weighing over 700 tonnes,” he said. “Lifting and creating the overbend can be both complex and challenging – even more so if the pipeline has to be pulled from an offshore environment.” As the pipeline diameter increases, so do the buoyancy forces created by the pipe as it displaces the drilling fluid during insertion, continued Mr Stockton. “This adds an additional process of water ballasting to the pullback, that must be well planned and coordinated.” The nature of steel pipelines – a favoured asset material in the oil and gas sector – means it is also essential for the pilot hole to be accurately drilled and the bore well-conditioned, said Mr Stockton. “A 106 cm pipeline will require a radius of approximately 1,000 times the pipe diameter to be drilled, whereas a polyethylene pipe may be closer to 35 times the pipe diameter. “As the radius becomes larger, the profile effectively straightens and thereby reduces the acceptable deviation of the drill bit. This makes accurate surveying and experienced drillers essential for meeting oil and gas specifications.” Taking a risk or paying the price Another key point of difference for HDD in oil and gas projects can be found in the design process, which is often driven by a risk-based approach compared to a utility project’s focus on price, said Mr Stockton. “Oil and gas projects proceed through a number of development phases that allow all risks to be fully evaluated both before and after tender. At each step of the process, a diverse group of experts will review and challenge the design to ensure all risks, including package interfaces, are correctly identified and managed. This ensures the tender evaluation process is driven by project outcomes and not price.” By contrast, a recent utility project had as much as 90 per cent of the tender evaluation criteria fixated on price – something that would not normally be seen on a major oil and gas project, said Mr Stockton. “Utility owners must start to realise that technical capability, quality, safety and environment are far more important than 10 per cent of the bid. For HDD to confirm its position as a reliable, safe and controlled process, more value and scrutiny should be placed on the engineering, design and contractor performance.” To help cement HDD’s position, Mr Stockton has developed an HDD QC package in response to industry needs. “Although HDD is often the most technical and challenging part of installing a pipeline, there are no inspection and quality controls,” said Mr Stockton. “The process is often left solely to the contractor or Client Superintendent who has limited HDD experience.” By incorporating risk management into all phases of a project, the key risks will drive the project’s ongoing design and construction methodology, concluded Mr Stockton. “In the feasibility stage, for example, the key project risks are identified and are the primary drivers for determining project feasibility and further studies. As the projects progress through further stages, the risk assessment – which is a live document – becomes more refined and detailed.”

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