Chemical tracers have long been used to keep tabs on what is going on in a reservoir, such as characterizing injection water flow through the reservoir, and to determine what type of fluid is flowing from a certain location along the well. Jennifer Pallanich checks out a plastic tool from Scandinavia that can trigger the release of its tracer when it comes in contact with oil or water.
Developed by Resman, a Norwegian company founded almost five years ago, the plastic tracers are hand inserted into sand screens or slotted liners, and the assembly is installed downhole, often in offshore wells. The plastic can be formed into any shape needed, and different tracers can be put in different places.
‘The chemical tracer inside here is either a water tracer or an oil tracer. If it's a water tracer and the water wets the plastic, the chemical breaks the weak chemical bond that it has with the plastic and goes with the flow. If it's an oil tracer, it's the same story, just with oil,' says Oddvar Solemsli, who joined the company in 2007 as CEO and is now VP of sales. Resman's offerings are for clean-up monitoring, water breakthrough monitoring and long-term production monitoring.
In general, chemical tracers are placed in a well to report what is flowing in which portion of the well. ‘Where do I have oil and where do I have water? If I know, I can do something about it,' Solemsli says.
When the tracer material shows up topside, it can be sent to the lab and analyzed. The lab can detect the tracer material down to parts per trillion, equivalent to a lump of sugar in two Olympic swimming pools, he says.
Resman can design its system to respond to different criteria. The chemistry wizards at Resman, Solemsli says, ‘understand and change the relationship between different plastics and different tracers.' The tracer system, consisting of the polymer carrier and the unique tracer, can be designed to leak at different rates.
‘We can control how this is leaked out, so it can last a long time,' Solemsli says. The wireless tracer goes down with the completion and can serve for the life of the well if need be, Solemsli says. ‘We have focused on oil and water, but we could also have focused on pH, pressure or temperature,' Solemsli says. ‘Chemistry isn't magic, but it is very, very close.'
The tracers have been used in the Siri field offshore Denmanrk, and the Volund and Tyrihans fields offshore Norway.
Resman's tracers were inserted into the Tyrihans B-1AHT2 horizontal well to monitor contribution of oil production along the wellbore, and results from the initial test production verified that oil production occurred from the toe, or outer part, of the well.
A heel of 700m and a toe of 1100m was cleaned.
The Resman wireless well inflow monitoring technology was used in this case for the first time to characterize initial oil production along a wellbore. In this well, the results confirmed the chosen well design was efficient, according to the company, allowing the operator to drill subsequent wells in the same design. Resman says the Tyrihans results showed a successful use of the oil-soluble tracers together with oil-based mud and that the tracer could survive a reservoir temperature of 137°C.
What distinguishes Resman's tracers from its competitors, Solemsli says, is that they are the first to use chemical tracers to characterize long term production of oil. The Resman tracers are embedded in polymers and integrated with the completion, a method that allows a more controlled release of the tracer molecules than competing technologies, he says. The result is better data for shortterm events and data for long-term events, which other technologies cannot provide at all, he adds. Finally, as an embed into the completion, the tracer differs from wire-based tracing technologies, he says.
In developing the technology, Resman's scientists talked to engineers around the world to understand what they wanted and needed in downhole tracer systems for oil and water. One such interview, Solemsli recalls, included a reservoir engineer saying ‘any data you can give us is better than what we have, which is nothing.' A lack of data can make it difficult – if not impossible – to optimize production. ‘The only thing our technology needs to function is flow – which is exactly what oil companies need as well,' Solemsli says, adding the technology adds no risk or downside.
Factors like viscosity, temperature, salinity, acidity and flow rates all come into play. As well, it's important to know what completion fluids are being used so they don't affect the tracer. The chemicals are non-toxic and stable, otherwise they wouldn't be effective as tracers, Solemsli says.
The company's roots stretch back to its founding in 2005 with two scientists working on the technology. It landed the order for the first installation in 2006. That pilot project in the Norwegian Sea, in 380m water depth, was for water breakthrough monitoring on Statoil's Urd field, and success there led to a larger R&D program. Additional orders followed in the North Sea, Gulf of Mexico, offshore Australia and offshore Canada, as well as some onshore placements in Europe and the US. By 2009, 20 people were on staff.
As of April 2010, Resman had installed its tracer technology in 25 locations, from Australia to the North Sea to the Gulf of Mexico and other offshore spots. Some were only intended to function at the start of the well, and some are ‘dormant, and waiting for the water', Solemsli says. He says the tracer is ‘a strategic tool to reduce the amount of produced water'. It can be used to optimize production, he added.
Solemsli says while Resman's technology may be less mature than other tracers on the market, the Resman tracer can work less expensively in locations too hostile for the competitors. The temperature range for Resman's projects to date is from 23°C to 162°C.
He's one of the few in the industry who can easily carry around a sample of his technology: a clear plastic rod about 6in long and thinner than a pencil. But its simple appearance is deceptive; Solemsli is fond of calling the tracer ‘talking plastic'.
Resman is investing in chemicals, analysis methods and interpretive tools. The company is also working to add gas tracers to its monitoring arsenal. That may be commercial as early as next year. Solemsli expects testing to begin on the gas tracing later this year. OE
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