OPERATORS of subsea fields on the Norwegian Continental Shelf – indeed any offshore province where there is deep water – spend vast amounts of money on keeping harmful ice-like crystals under control.
However, scientists at Scandinavia’s largest research institute, SINTEF of Norway, are now looking for a cheaper solution to the problem.
They are trying to solve the mystery of what happens when hydrates are formed. These ice-like crystals can accumulate in offshore export pipelines, and eventually block them, unless there is systematic, regular intervention of some kind or extensive, expensive insulation.
Senior scientist Sylvi Hoiland, of SINTEF Petroleum Research, is the leader of the SINTEF project known as Hyades, which is supported by the Research Council of Norway, the University of Bergen, Statoil’s research centre in Bergen and Chevron.
“Our final goal is that it will become possible to take a sample of oil into a laboratory, where simple analyses of the composition of the oil can produce results such as that the hydrates found in oil A are very likely to block the pipeline, while oil B will not be a problem at all,” says Hoiland.
“However, the Hyades project on its own will not be enough to bring us to that point, but it should take the offshore industry an important step further towards the goal.”
In any case, the international petroleum industry has long been aware of this SINTEF project, and Shell pronounced some time ago at a conference that the company regards the method being developed for characterising different types of oil as promising.
The background for this project is oil&gas recovery from subsea fields from which the well flow is carried in pipelines either to neighbouring platforms or directly to shore, in the latter case over increasingly long distances – which is not always a simple matter.
This is because it is not often that a flow of pure oil or pure gas emerges from the well. The product flow is nearly always a mixture of oil, natural gas and water – a potential seeding ground for hydrates formation if temperatures are low enough.
The longer the pipeline, the greater the challenge of flow assurance becomes.
Similarly, when maintenance work or other circumstances make it necessary to shut down production on a field for some time, the pipeline temperature may fall so low that it creates ideal conditions for the formation of hydrates.
The SINTEF team’s hope is due to the fact that certain types of oil possess properties that prevent hydrates from becoming sticky “snowballs”.
When such oils are present, the hydrates stay in the form of a fine powder that can easily be carried along the pipeline.
But which components of the “unproblematic” oil actually make it unproblematic? That is the key question being studied by the Hyades group.
Some types of hydrate crystals are worse than others. Certain hydrates have properties that make the crystals resemble a sticky slush. These are capable of growing into large plugs that can completely block the pipeline.
In order to prevent hydrate formation, the oil companies pump large volumes of methanol or glycol into many of their wells, pipelines and process systems.
Similarly, during both planned and unforeseen production shutdowns, large amounts of chemicals are added to production systems to keep hydrates from forming, all of which is expensive.
Not only are the chemicals themselves expensive, but when shutdowns are ordered, production losses are prolonged by the time needed to pump large volumes of chemicals down the pipelines, and on the shelf, lost time means lost income.
According to Statoil, the oil analysis tool that the Hyades project aims to develop is an important prerequisite for the development of predictive methodologies and processes.
The Hyades project is a continuation of work that was initiated by the former Hydro in 2000. Since then, the company has been merged with Statoil and the hybrid brand, StatoilHydro, used over the past few years has only just disappeared.