Expanding SAGD cogeneration could help environment, public grid

Oilsands cogeneration. Source: MEG Energy

Expanding the use of combined heat and power technology (called cogeneration) at oilsands SAGD projects would cut more greenhouse gas (GHG) emissions from Alberta’s electrical grid — and at a lower cost — than simply replacing coal with stand alone natural gas-fired power, researchers at the University of Calgary say.

Two papers recently released by the U of C’s Canadian Energy Systems Analysis Research Initiative (CESAR), conclude cogeneration at SAGD facilities would reduce more GHG emission from Alberta’s public electrical grid — and at a lower cost — than simply replacing coal with standalone natural gas combined cycle (NGCC) power.

The Alberta government plans on retiring most of the 33-per-cent efficient coal-fired generation plants in the province with 50-per-cent efficient NGCC generation.

While this is an improvement, it will still mean that power generation throws away 50 per cent of the fuel energy as waste heat, says David Layzell, professor and director of CESAR, who is scheduled to speak at the Canadian Energy Research Institute (CERI) Oil & Gas Symposium scheduled for March 6-7, 2017, in Calgary.

“When you actually look at our thermal power generation, the very nature of thermal power generation is it throws away a huge amount of waste heat. Even the best technology, which is NGCC, discards about 50 per cent of the heat energy in the fuel, if you like,” he said.

“So we said, ‘That doesn’t make any sense.’ In most jurisdictions around the world that have thermal power generation, they don’t have any industries that could possibly use that much heat. But in Alberta we have very large heat demands, none larger than SAGD operations, and given that we’re talking about phasing out coal in the next 13 or 14 years, we thought why not be sensible and increase the overall efficiency.”

Cogeneration with gas turbines and heat recovery steam generators using natural gas is a commercial technology. It has been installed in several SAGD projects ranging in size from 80 megawatts to 400 megawatts and proven to be reliable and easy to operate.

The CESAR studies show how larger scale SAGD cogeneration — two 85 megawatt gas turbines on every 33,000 bbl-per-day facility — could result in the earlier retirement of coal plants than envisaged by the Alberta government, achieving additional greenhouse gas emission reductions of up to 142 million tonnes of CO2 between now and 2030.

“The actual cost of cogeneration is easily the lowest cost of all thermal power generation technologies and we can actually benefit the oilsands if we reduce our carbon footprint. We can get [ourselves] off coal earlier than planned and help in the transition and we can get a GHG benefit, as well,” Layzell said.

The researchers also suggest that by assigning oilsands companies temporary GHG credits for investing in cogeneration and reducing the province’s overall GHG emissions would also reduce the GHG intensity of SAGD production to be equivalent to, or lower than conventional oil.

Another benefit, according to Layzell, is that SAGD cogeneration would stabilize electricity prices and could provide a reliable source of baseload and backup power for the expanded renewable energy that the Alberta government wants to incorporate into the electrical grid.

“What we’re doing is just putting the gas turbines on and then the steam that’s produced we actually use duct burning to increase the amount of steam, because the heat demand even with all those gas turbines … is huge,” Layzell said.

“That, with duct burning on a typical steam-to-oil ratio of three SAGD facility, can provide all of the steam requirement and power requirements for the facility, plus export up to 150 megawatts to the public grid,” he added.

“So for each 33,000 barrel-per-day SAGD facility, it could provide about two per cent of the needs to the public grid. And we have 20-odd of them [SAGD facilities] in the province now, so you’re got an opportunity to provide base power.

For more information on the CERI conference, click here .

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