I currently live in Calgary, and thinking about moving to Doha. Please see my latest post in the "Cost of Living" section. I have attached a spreadsheet that compares budgets in Calgary vs Doha.

Some points to consider:
1. Calgary is more expensive than Edmonton, so the 85K will get u much further in Edmonton than in Calgary (or in Fort Mac) - main reason is housing is slightly cheaper in Edm than in CGY or Fort Mac.
2. If its just you + wife, 85K may be OK (in a small town like Lethbridge but not in the big city). But if you have any kids, well, tougher.
3. Overall, I agree with the above posts - for someone with your experience, getting into the 90's or low 100's should not be a stretch.
4. The job market here in oil and gas is heating up. Lots of companies are starting to hire again. Meaning you could pass up on this offer and try to find something better..