SINTEF expands multi-phase test center
Nick Terdre
Contributing Editor
The SINTEF research group has added two laboratories to its facilities in Trondheim to investigate multi-phase flow – a medium-scale test loop and a security cell. The NKr35-million ($6-million) project, funded entirely by SINTEF, will allow more detailed studies and for actual hydrocarbons to be used in experiments, says Jon Harald Kaspersen, research director.
Its main experimental facility is a large-scale test loop which came into operation in the early 1980s. This consists of a 1-km (0.6-mi) loop of 8-in. (20.3-cm) pipe with a 58-m (190-ft) riser section. Experiments can be run with pressures to 90 bar (1,305 psi).
Experimental data generated on the large-scale loop helped create the basis for the Olga simulation program which, together with its successors, is used widely in the oil and gas industry. In recent years SINTEF realized it needed to expand its research capability.
There is also an economic benefit for clients, as the cost of working in the new, smaller laboratories will be less than in the large-scale loop. But the new facilities are essentially complementary, and some projects will make use of all three.
The medium-scale lab houses a 200-m (656-ft), 3-in. (7.6-cm) three-phase test loop which can be pressured to 10 bar (145 psi). By using SF6 as the gas phase, flow behavior can be simulated up to 60 bar (870 psi).
“Multi-phase flow is a very complex physical problem,” says Kaspersen. “This facility allows us to study it in much greater detail. For example, we can study the droplets of crude, see how much gas is entrained in the oil, and see how many of the droplets pass from the liquid phase into the gas phase. All this is required if we are to make more accurate models of multi-phase flow.”
While historically multi-phase flow studies are based mainly on fluid mechanics, Kaspersen says it is necessary to throw more light on the chemistry of what is happening. As fields on the Norwegian continental shelf and elsewhere begin to age, more and more water comes up with the hydrocarbons. Comprehending the interactions between the different phases requires an understanding of the chemistry of events.
The security cell is an explosion-proof laboratory with six separate cells designed to allow experiments with live crude and natural gas. Because these are inflammable materials, three of the lab walls are built from explosion-proof concrete, while the fourth is designed to be easily blown out. Personnel control the experiments from behind one of the explosion-proof walls.
Again, the use of actual hydrocarbons breaks down an important barrier. Previous research has always made use of model fluids, such as inert gases, but these do not behave in exactly the same way as real hydrocarbons. Live crude, for example, changes its properties both as it ages and in varying pressure and temperature conditions.
This lab also is designed for studies on high-pressure/high-temperature fluids. The largest cell houses a 50-m (164-ft), 1-in. (2.5-cm) flow loop which can be pressured up to 100 bar (1,450 psi) and is fully temperature-controlled from -10 ºC to +50 ºC (14-122 ºF). This loop is designed to study wax and hydrates.
The multi-phase facility has a permanent staff of 24, although some experiments involve personnel from other parts of the SINTEF organization.
Projects are under way in both the new labs. Some of the work for the SmoothPipe project is taking place in the medium-scale facility. This aims to identify coatings for the internal pipe wall which reduce resistance to the flow, in turn lessening the pressure drop. Nano technology is included – there are early indications from experimental work that the addition of nano particles to the coating can help reduce the rate of wax deposition, Kaspersen says. This could facilitate longer subsea tiebacks.
The medium-scale facility also will be the setting for experiments with viscous crude. SINTEF is putting together a joint industry project to study the behavior of viscous crudes and work should start this year.
Viscous crude is among the increasing challenges faced by the oil industry, and is characteristic to oil discoveries made in the Barents Sea, Kaspersen says. Little is known about the behavior of such crude, although it changes the character of the flow drastically. If gas becomes entrained in the crude, it is difficult to separate. Flow simulators are not able to model multi-phase flows containing viscous crude, so experimental data is required to enable this ability to be developed.
While the bulk of the work focuses on the behavior of pipeline flows, SINTEF’s facilities also have been applied to processes such as subsea separation.