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Hyperspectral surface scan of core
Every pixel has single spectral signature indicating mineralization; system offers ultra-high spectral and spatial resolution Steve Sutherlin Petroleum News
Perth, Australia-based Corescan’s hyperspectral core imaging system integrates reflectance spectroscopy, visual imagery and 3-D laser profiling to map the mineralogy and geochemistry of drill core, rock chips and other geological samples, according to the company. The proprietary designed in-house system offers ultra-high spectral and spatial resolution.
Dr. Brigette Martini, Corescan chief geologist, presented May 31 at a technical breakout session at the state Geological Materials Center in Anchorage. The session focused on the potential for new investigative technologies and machine learning systems to better assist geoscientists and resource companies to meet the challenges of interpreting Alaska geology.
“We have very extensive surface coverage, but no penetration into the core itself,” Martini said.
“The mineralogy and the log that we give you, we call it semi-quantitative; it is not whole rock - it is surface, but it’s a lot of surface.”
Every pixel has a single spectral signature.
“Every one of those 200,000 pixels has a spectrum that we then interpret based on our own internal software; we use USGS libraries that are highly validated,” Martini said. “From that we’ve introduced these beautiful surface maps, so we show you spatially where all of your mineralogy is.”
Why hyperspectral? “I’m going to really encourage everyone in oil and gas in particular to pivot a bit here - we love our nanoscale, really fine resolution,” Martini said. “I encourage you to be thinking about how we take fine nanoscale type information, and we can use this type of continuous mineralogy, that is, a micron scale to help scale up a lot of our smaller limited interval-type measurements.
“There are minerals and there are types of minerals that you can do with infrared better than you can in other types of technologies, some of the main ones I always like to point out is the hydrated silicas, amorphous silicas, opal, calcinite, those actually have beautiful spectral signatures,” she said, adding, “It can be very difficult to impossible to do in other types of techniques.
“One of the technical integration specialists that works with a lot of our clients calls Corescan a lifestyle; it’s not just a single instrument, but it’s the logging, it’s the building of the instrumentation, it’s the bringing them in to facilities, but it’s also very importantly the interpretation,” Martini said. “We are not asking you to interpret this data, we do all of that.
“What you get when you scan with Corescan is all the images and the full mineral map as well as drive lithology” she said. “It’s the interpretation of it, then followed on by the visualization of it, within either your own software or with coreshed.com which is how we serve up our data.”
High resolution “The important number that you can see is our spectral resolution is about 3.5 nanometers, that’s how wide our bands are and that’s really important if you’re trying to do compositional data and do identification of very fine scale mineralogy and compositional mineralogy,” Martini said. “We’re doing digital photography at 50 microns, we’re doing the hyperspectral at 500 microns, and we do run a laser profiler over the tops of the core to do technical work - fracture orientations, joint spacing, et cetera. Those three are all happening at the same time.
“Currently the vertical resolution is 20 microns vertical, so that’s going to help a lot with very fine formational boundaries and structure.” she said. “Depending on what we’re doing we do scan slower than the other system on the market. We’re only doing about 500 meters per day.”
The system is mobile, in containers for easy transport, and to keep spectrometers clean, dry and at a constant temperature.
“We do not touch the core unless it needs to be slightly cleaned; we do not pull the core out of the box, the box moves back and forth on the scan table, the scan head stays stationary,” she said.
Corescan processes data on site and is capable of analyzing data on site “if that needs to happen,” Martini said. It takes between 7 minutes and 12 minutes per box for scanning.
“We can scan anything; we’re in the process of scanning a lot of oils, so long as they’re viscous enough,” she said.
“We can also scan liquids, but dominantly we’re scanning a lot of core - whole core, slab, hand samples, and of course, cuttings - the vastly ignored resource of not just oil and gas but mining as well,” Martini said. “Cuttings are wonderful; they’re quick to scan, they’re cheap and you get a lot of mineralogical information.”
In Alaska Corescan has, in a study with the U.S. Geological Survey, made scans of the Inigok No. 1 well, the Ikpikpuk No. 1 well, and the Phoenix No. 1 well, each penetrating the Shublik formation on the western North Slope. Martini displayed those results to illustrate capabilities of the technology.
Infrared spectroscopy is very good at identifying carbonates, she said.
“It’s not just calcites, dolomites, but I can also tell you spiderite or anchorite or rhodocrocite, you see all the different types of carbonates listed off here and it’s all based off of a combination of that absorption feature ... which is due to a carbonate molecule, as well as some other features that show up, particularly in the visible when you start getting iron coming onto the system.
“You could say, ‘I’m a geologist; I can tell the difference between calcite and dolomite when I’m looking at core,’” she said. “But we can do it very rapidly and non-destructively - no acid bottles.
“Shublik is kind of most dominantly all calcites, there is some dolomite in it but it is ... very dominantly calcite,” she said. “We see with the red colors (in the display) it’s more strongly calcite, and with yellow, it’s still calcite - a little bit less, probably mixing with other things. We can also do things like grain size; right now this is relative grain size.
“We do this based off some simple calculations looking at the absorption feature, the shape of it and the depth of it.”
“In the Kingak shale we have kaolinite, and so not only are we telling you, you have kaolinite, but we’re showing you exactly how it’s distributed spatially, which could be really important, particularly looking at biological indicators, et cetera,” she said.
Martini said Corescan’s coreshed.com holds data that can be combined with a client’s data to more finely understand scan results.
“Coreshed.com doesn’t have just Corescan data in it; we pull in people’s huge historic photo collections all the time. We can also do some really simple enhancement of old core photos to help bring out really cool information,” she said.
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