In mining and oil sands, one of the biggest challenges faced by operators is dealing with slurries – complex mixtures of solids and liquids – which need to be sent via pipeline for processing, treatment and environmentally-safe disposal.
The way that fluid flows, influenced by factors such as rheology, velocity, temperature and pressure, can affect the size of the pipeline and the architecture of the system used to transport the ore and water slurry, or crude oil mixture running through it. The study of fluid mechanics is the specialty of the Saskatchewan Research Council’s (SRC) Pipe Flow Technology Centre, which has been working closely with oil and mining companies for more than 50 years, to engineer solutions to their slurry pipeline challenges. The 20,000-square-foot facility, owned and operated by SRC, features a series of pipe loops, tanks and mixers, all temperaturecontrolled to create the right environment to run experiments simulating real-world conditions.
Fifteen people, including eight technologists and five engineers, are employed at the Saskatoon site. The Centre’s manager, Lesley McGilp, spoke to Oil and Gas Product News recently about the Pipe Flow Technology Centre and how it works with industry.
OGPN: What is the main purpose of the Centre?
LM: We’ve been studying slurry fluid dynamics for over 50 years and so our main expertise is focused in that area: the transportation of complex mixtures. Slurries are very common in the mining sector and oil sands is one example where there are a lot of slurry applications. The oil sands industry is our biggest client, the surface mining side mainly. We have done work for conventional oil and gas applications as well but the big one is oil sands.
OGPN: How is the Centre funded?
LM: The vast majority of what we do is funded by industry. We have some projects where we go out into the industry and market something that we want to study that we think would be of value to them. But most of our work is client-directed, where a company will come to us with something that they want to study or a problem they’re having. We have the ability to set up pilots that can mimic field conditions or study the complex flow issues they’re having.
OGPN: Why is it important for companies to do research into how slurries behave?
LM: I think that the biggest benefit for industry is improved design and that helps them in a few different ways. You’re potentially reducing your capital costs because you’re picking the right equipment right from the beginning, the right size of pipe, the right size of pump. When companies don’t know for sure, equipment gets put in that’s incorrectly sized and then you end up trouble-shooting that equipment. So you have operational expenses associated with trying to work with a system that isn’t ideal. A system that is properly designed is more energy-efficient, so you’re saving electricity costs. There’s an environmental benefit to improved energy efficiency as well.
OGPN: What are some significant pipeline applications that the Centre has been involved in over the years?
LM: One of the big things that our group was involved in was developing hydrotransport technology for the oil sands industry. In the ‘80s and early ‘90s, all the oil sands ore was transported to the extraction plants via conveyor belts. You can imagine what that was like. Kilometres-long conveyor belts out in the open in the rain or the snow. They had a lot of struggles with run time, their equipment would go down, things would break or seize up. There was an interest in looking at whether this ore could be pipelined. They would mix the ore with water and then pipeline the slurry to the extraction plant. That’s what is done now. That technology was developed at our Centre, working with a leading oil sands operator, and now all oil sands operations use this technology. It was really a game changer for the industry and vastly improved their run times and lowered their operational costs.
It also has the added benefit that you start the extraction process in the pipeline. Now that process, of separating the bitumen from the sand, starts in the pipeline while it’s being transported so that’s one of the advantages of hydrotransport, in addition to being more reliable operationally and more efficient.
Another big innovation is SRC’s Pipe Flow Model. Slurry pipelines are, complex, hard to design and there’s no equations in your university textbooks that would allow you to design a slurry pipeline. Our researchers developed equations that represent the mechanics of the flow. They’ve incorporated this model into a spreadsheet format so designers can use it to make calculations for slurry pipelines. We offer training courses in how to use the model; we’ve trained over 800 engineers over the years. It’s an industry standard now, in particular for oil sands, but it’s used worldwide for a variety of slurry and mining applications.
“We have added a high-pressure, hightemperature pipe loop capable of handling flammable materials. Before the expansion, we could only test low pressure conditions and up to about 65 degrees Celsius, but there are a lot of applications, particularly in oil and gas, that are higher temperature or higher pressure.”- Lesley McGilp
OGPN: What is the data from that computer-based flow model telling the pipeline designer?
LM: There are two things that are really important about designing a slurry pipeline. One is the pressure drop. You need to know how big a pump you have to put on the line to get the material from A to B. In order to calculate that you need to know what the pressure drop would be over a given length of pipe. The other big thing is the settling velocity. With the mixture of solid and liquid in a line, if the fluid is moving too slowly the solids can start to drop out and they’ll settle on the bottom of the pipe. This isn’t good because eventually you can plug your line. When you’re out in the field and you plug your line, you won’t necessarily know where it’s plugged and you may have to dig it up to unplug it. It’s a real operational problem. The model tells you what the settling velocity will be for your slurry under different operating conditions so that you can design your system so that it operates above that velocity.
OGPN: Is the Centre doing any research into tailings disposal?
LM: Yes, we’ve been doing a great deal of research related to improving tailings management strategies for the oil sands industry. Our research has spanned projects involving pipeline transport, open channel flumes, thickeners, deposition experiments, and so on. Most of the work that we do is proprietary to our clients. But they are sharing it with one another through an innovation network for environmental research... That’s something that’s really exciting to see actually. What we’re working on for one oil sands company is being shared with other companies and then they’re all kind of moving forward on this technology in tandem, assisting one another with the research. It’s a big challenge, it’s a complex problem, but because it’s an environmentally-focused area, there’s more interest in collaborating.
OGPN: The Centre recently completed an expansion. What was involved there?
LM: We have added a high-pressure, high-temperature pipe loop capable of handling flammable materials. Before the expansion, we could only test low pressure conditions and up to about 65 degrees Celsius, but there are a lot of applications, particularly in oil and gas, that are higher temperature or higher pressure.
One potential market for this equipment is the SAGD industry. It’s a big percentage of oil sands production but there’s heavy oil production that is steam-based as well. There’s also some interest in looking at solvent extraction technology. The equipment could be used for that too. Those were some of the drivers behind why we thought it would be a good idea to build this facility and how we thought it could be used. The fluid mechanics at those temperatures and pressures are not as well understood and so I think there’s a lot of scope there for study and improved understanding.
OGPN: Anything else in the pipeline, so to speak?
LM: We are looking at incorporating laminar flow into SRC’s Pipe Flow Model. The model is currently only relevant for turbulent flow. You can think of turbulent flow like a fastmoving river where everything is mixing really well. Laminar flow is like a slow, meandering stream, it’s very calm on the surface. So when you have laminar flow in a slurry line, that’s when you’re more likely to see issues with deposition. When you have really thick material, say a thick slurry mixture with lots of clays, we use the term yield stress. It’s like toothpaste, you have to squeeze it out of the tube, or like ketchup. It doesn’t move on its own. That’s yield stress. It’s what holds the ketchup back.
When we’re talking about tailings challenges in the oil sands, one of the methods of improving the outcome in the pond is to thicken the material before it gets there so it’s more like toothpaste or ketchup when it reaches the pond; there’s less water content. But when you pump that, because it’s so thick and goopy, it’s likely that the system will be operating in the laminar flow regime, which is not nearly as well understood.
OGPN: It does sound like an interesting area to research. Thank you, Lesley, for taking the time to explain what the Centre is all about and its benefits to the industry, particularly in the oil sands area.
LM: You’re welcome.
by Andrew Topf