Regina – One of the most significant new diagnostic tools in oilpatch research and development is a new computerized tomography (CT) scanner put in place at the Saskatchewan Research Council (SRC) facilities in Regina.
The Petroleum Technology Research Centre (PTRC) provided much of the funding for the CT scanner, and SRC is the organization employing it.
“The acquisition of this unit was a joint collaboration between Western Economic Diversification Canada, SRC, PTRC, and the University of Regina. All of those parties put funds into it,” said Mike Crabtree, Saskatchewan Research Council’s vice president for their energy division.
“When we’re looking at enhanced oil recovery, whether its bitumen or in the Bakken, what the CT scanner allows us to do is look inside the rock at very, very high resolution, and understand what is actually going on during these processes,” he added.
An operator might cut a four-inch core several metres long. “We would take a section of that core and inject some water and surfactant. Before the CT scanner, we would inject at one end, and see what comes out at the other end. And we might tap the core along the top for pressure, but you would characterize the performance of it by looking at what goes in and what comes out, and maybe when you’re finished, you might excavate the core, to have a look inside to see what changes may have occurred.”
“What the CT scanner allows us to do is visualize the rock and the fluid as it is moving through the core. We can see things like how is the actual water and surfactant interacting with the oil at various points in the core. Is there any fingering? How that fingering works? We can then look at different temperatures and pressures and how that performs in realtime. It’s a really big step forward. It’s the only one of its type used in this application in Canada. There’s only two or three machines of this power and scale in Canada, and probably only about a half dozen across all of North America. We’re only one of two used in this area.”
“It will be very important in looking at post-CHOPS technologies.”
Dr. Peng (“Mars”) Luo is a professional engineer with the SRC. He is the lead of four people who operate the CT scanner. He works on the reconstruction and image analysis.
The $1.6 million scanner is a large metal box, which encloses the apparatus with thick walls. There’s a heavy, shielded door on one side. At the end are the multiple screens for the computer controls.
Luo explained that other labs have medical CT scanners. They are fast, but have coarse resolution. This one is industrial-grade.
“The advantage of this is higher penetration, because it has much higher energy than a medical scanner. So, it can penetrate steel,” he said.
Inside the box is a rotating stage which can be positioned and rotated as needed. The scanner has two X-ray tubes, one 225 kilovolt (kV) micro-focus tube with higher resolution and less penetration power, and the other 450 kV mini-focus tube with lower resolution and more penetration power. The tube with a matching detector on the opposite side can move up and down for scanning long objects.
In a medical scanner, the object (usually a person) is stationary and the X-ray tube rotates. This setup has a stationary tube and detector while the object rotates 360 degrees. The higher resolution tube can scan down the micrometre resolution. The other one is higher power, and it can penetrate very dense material such as metal several inches in thickness or core five inches in diameter.
The item is placed on a few pieces of Styrofoam insulation which is invisible to the X-rays, effectively suspending the object in space as far as the scanner is concerned.
One of the uses is creating a “digital rock” of the core. He pulled up an example of core from the Viking formation in west central Saskatchewan. At a resolution of 40 micrometers, it was possible to see the natural fractures within the core, as well as tell the clays from the sandy zones. The darker the colour in the image, the lower the density.
“This is the way we determine the mineralogy of the rock, as well as the porosity and fractures of the rock,” Luo said.
Looking at core under a microscope or scanning electron microscope (SEM) allows essentially only two dimensions of analysis. These CT scans allow a third dimension of the entire core.
“Once we scan this core plug, I can slice this core plug from any angle I like at resolution of scores of micrometres.”
Another Viking core showed horizontal fractures. “You can see laminations and sedimentations this way,” he said, showing the horizontal plane.
They are able to work with core plugs and full-sized 3.5-inch core.
A synthetic diamond that was 850 microns in size was scanned at a six micron resolution. A scanning electron microscope can get much higher resolution, but can only see the surface. Core plugs of 1.5-inch diameter are usually scanned at a 30 to 40 micron resolution.
“To petroleum engineers, the things they want to know first are the rock structures and mineralogies. You can know the distribution or proportions of different minerals like quartz or clays, which are very important from the production process,” Luo said.
“The second important thing for petroleum engineers is you are able to determine the fluid distribution within the pore space, with some manipulation in image analysis,” he said.
If you did a core flood, you can see what is happening within the core without opening it up.
They acquired an aluminum core holder that can conduct a coreflood at reservoir conditions and can scan on the go.
In addition to reservoir cores, other items such as metal tools, diamonds, fossils and potash have been scanned.
Around 60 to 70 per cent of the scanner time is dedicated to reservoir rocks. After almost a year of technique development and optimization, SRC has recently released a price list for its usage, as they are now ready for commercial operation.
While geomaterial is a key focus, the CT scanner is not limited to that. It is a non-destructive testing technique and therefore can be used for many areas such as defect analysis or weld scans and manufacturing. SRC intends on offering this service to various Saskatchewan manufacturers.
