Sept/Oct 2012

Citrus twist

A Calgary company opens up a new frontier in bitumen mining

By Graham Chandler

Tabbies 2013On the 9th floor of Calgary’s downtown Ford Tower, a company is at work planning a new bitumen venture. This is hardly unusual in Calgary. What sets the team at US Oil Sands Inc. apart from the crowd is that it is planning the first commercial oil sands production in the United States. And it will not be using the tried-and-true steam assisted gravity drainage or Clark methods to extract the bitumen.

“We have a technology that allows us to do things much more efficiently than they’ve been done before,” says Cameron Todd, CEO of US Oil Sands. “With less cost, less complexity and, at the same time, huge benefits environmentally – it’s a win-win-win thing.”

On the company’s 32,000-acre lease in Utah, just south of the town of Vernal, US Oil Sands will mechanically strip the ore using a Wirtgen surface miner. Marble-sized chunks, about two centimetres in diameter, will be trucked to a processing facility which de-lumps and heats the ore to loosen most of the bitumen. To complete the bitumen extraction from the sands, a bio-solvent will be used, which will be recovered and recycled. An important aspect of this process – no tailings ponds.

Todd, with five years’ experience in oil sands development and operations on his long energy-centric resume, explains how they ended up applying the US Oil Sands process in Utah. “We came up with the process first,” he says, but with no access to land in Canada, “we went to Utah.” To their surprise they found out no other process had worked in Utah, but theirs did.

Utah’s bitumen is unlike Alberta’s but similar to the rest of the world’s. “Athabasca is the unique place,” says Todd. “Most places on earth are the way it exists in Utah where oil preferentially sticks to the rock. When you go to Utah and heat up the rock the bitumen will flow out of the pores but also will stay stuck to the grain.” The Clark hot water process, where the sand comes out relatively clean, does not work in Utah. “The thin layer of bitumen on each grain supports very little water in the system.”

The difference is geology. “We sit on a plateau where we have a very thin overburden, about 20 feet (six metres) thick, then a layer of bitumen in sandstone below that,” explains Todd. “All around our lease we have deep eroded canyons and much of the water has run off so it’s undersaturated for water. What’s left behind is a slightly weathered oil.” The bitumen is in multiple layers, each up to 15 metres thick with rock in between.

Extracting with bio-solvent

Unlike the boot-sticking Athabasca oil sands, these ores are more solid than asphalt. Todd shows off a chunk; it is black, hard like sandstone and smells faintly of oil. He says it is between 0.3 per cent and 0.4 per cent sulphur, which makes a huge difference at the refinery; there is no need for the energy-intensive process of stripping that out.

Because the ore is relatively hard, the surface miner is ideal for ripping it up. The machine’s teeth can be adjusted to provide different-sized material. In US Oil Sands’ case, marble-size suits the processing with no need to crush it further. Instead it will go to a de-lumper, which consists of counter-rotating drums that break up the ore that may have compacted during hauling and reduce it back to the desired size. Todd displays a jar containing the conditioned ore as it will appear off the de-lumper; it feels much like Athabasca oil sands but drier and more crumbly.

During processing, unlike in Alberta, application of hot water removes only some of the bitumen and much remains stuck to the sand grains. “So you are left with low recoveries and an oily mess of sand that you can’t dispose of,” says Todd. “I would guess maybe 20 per cent sticks to the grains.”

This is where the company’s creative use of a bio-solvent comes in. Barclay Cuthbert, US Oil Sands’ vice-president of operations, describes it as a by-product of the global citrus industry. “Once the orange juice etcetera is out and you’re left with the pulp and peel, a naturally occurring chemical can be extracted; it’s produced in the thousands of tonnes annually. It breaks down readily, both in soil by aerobic bacteria and in the atmosphere by photochemical means.”

It is added into the initial extraction process with the hot water to make slurry. “The solvent dissolves into the bitumen, changing both its viscosity and its specific gravity,” says Cuthbert. “So it allows us to separate the oil from the sand and water.” Once that is done, a distillation process is used to recover the solvent for reuse, a bonus because “in its pure form it’s quite expensive,” according to Cuthbert.

The solvent ensures a 96 per cent bitumen recovery, leaving sand particles clean enough to put back in the mine right away. “So we can reclaim the mine as we go,” says Todd. “What you have is clean bitumen, clean water and clean sand.”

In the Athabasca sands, fine clays are problematic. Utah sands have much less, but content is variable, so different concentrations are tested in the company’s Grand Prairie pilot plant. They have brought in sands from all over the world to test the process, typically running about a tonne and a half of ore, about a barrel of bitumen per hour. “We have done a hundred different pilots in Grand Prairie where we can test a lot of different variables like temperature and flow rates, how much and what kinds of solvents, and low fines and high fines,” says Todd. “So we know to optimize the process for whatever ore deposit we have to work with. That makes the pilot really valuable.” In Utah, the company has run extraction pilots up to 500 barrels per day (bpd) and tested the continuous mining equipment up to 3,700 tonnes per day.

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