The Casino offshore pipeline required inspection to demonstrate the integrity of the pipeline and allow the operating life of the pipeline to be extended. There were numerous challenges in performing a conventional internal pipeline inspection which would have required diver operations to install and operate subsea pig launchers. Two alternative inspection methods were used to inspect the high priority sections of the pipeline, at the pipeline tees and in the horizontal directionally drilled (HDD) section of pipeline at the coastline crossing.The pipeline tees and well flowlines were inspected using an external magnetic flux inspection tool deployed by remotely operated vehicle (ROV), to test for top-of-line corrosion. Bi-directional pigging from the onshore valve station, offshore for 30 km using gas from the host gas plant and then return to the shore using gas from the offshore wells allowed for inspection of the HDD pipeline with a total of 10 bi-direction pig runs completed. The pig position was accurately predicted by monitoring the operating conditions of the pipeline and confirmed by displacement past the subsea well closest to shore (Casino 5). The novel pigging methods brought significant benefits for cost, schedule and reduced EHS exposure by avoiding diver operations. The cost of the overall inspection program was less than 25% of the conventional inspection methods and was achieved a year earlier than if a dive support vessel (DSV) had been mobilised. The bi-directional pigging campaign proved to be highly successful.
Australia's relative isolation and the harsh environment in Bass Strait have led to many innovations in offshore oil and gas developments. The initial developers were moving into frontier territory when Bass Strait was developed, with the harsh sea state and the water depths presenting major challenges. The original development of Bass Strait in the 1960s was tied to a wet gas pipeline philosophy, which was a novel step-out from normal industry practice. For example, the North Sea developments, which started shortly after Bass Strait, adopted dry gas export pipelines and required substantially larger platforms to process the gas for export. The cold waters of Bass Strait require an active hydrate management strategy and the success of hydrate inhibitors has been a key element in using wet gas pipelines. The initial development relied on methanol for hydrate inhibition, but this changed to a glycol-based hydrate inhibitor within 10 years of production start-up, due to challenges in the onshore production facilities. The use of mono-ethylene glycol for management of wet gas pipelines was demonstrated in Bass Strait. The success of the initial developments has given operators the confidence to pursue marginal field developments that rely on wet gas transport to the beach. The Minerva, Casino, Thylacine and Longtom gas field developments in Bass Strait have all adopted the same strategy, in part because of the confidence provided from operating the initial developments for many years.
2014 was the penultimate year for many of the massive multi-year LNG development projects. These projects will lift Australia’s LNG capacity by more than 250% from present levels. The first train of the Queensland Curtis LNG project came on-line in late 2014. Exports are expected to commence from a further three LNG projects (APLNG, Gladstone LNG and Gorgon) in 2015. The ramp-up in gas demand on the east coast of Australia is spurring secondary development. A pipeline link has been proposed from the NT’s gas transmission system to connect to the east coast gas transmission system to allow gas from the Timor Sea to be fed into the east coast market and to the Queensland LNG projects. 2014 was a quiet year for new oil developments. Offshore, the Balnaves FPSO development was brought on-line. Onshore, the operators of the Cooper western flank continued to discover and develop a series of small fields. These small developments and better performance from some existing fields were able to offset natural reservoir decline elsewhere, leading to an overall increase in crude oil production of approximately 4% from the previous year. The second half of 2014 was characterised by a decline in crude oil price from more than $100/BBL to under $60/BBL by year-end. For many LNG contracts, LNG price is linked to oil price; existing LNG developments are well progressed and are unlikely to be curtailed by the low commodity price, but future developments are already being slowed or stopped.
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