Where is shale gas found?
There are five major shale basins in the United States from which shale gas is produced. To date, more than 40,000 wells have been drilled. There are seven other shale basins from which there has been no production.
Shale gas in Canada
Although there is currently very little commercial shale gas production in Canada, there is active exploration and resource evaluation in seven provinces and one territory.
| Province/Territory | Location |
Gas in Place billion cubic metres) |
|---|---|---|
| Alberta | southern two-thirds of province and along Rock Mountains and foothills | 28,328 |
| Saskatchewan | southern one-third of province | Not Available |
| Ontario | southwest tip of province | 6 |
| Quebec | St. Lawrence Lowlands between Montreal and Quebec City | 40 to 1,150 |
| New Brunswick | southeast part of province | Not Available |
| Nova Scotia | northern part of province from New Brunswick border through Cap Breton Island | Not Available |
| Northwest Territories | southwest tip of territory | Not Available |
Most of the current shale gas production in Canada is from the Horn River Basin and Cordova Embayment areas of British Columbia, and from northwest Alberta.
How is shale gas produced?
Because shale makes up the largest proportion of sediments in the Western Canada Sedimentary Basin, gas shales are thick and laterally extensive. Although production rates are generally low, gas shales tend to have low decline rates once production has stabilized and long production lives. Drilling and production of gas shales in many cases is very similar to that for conventional natural gas reservoirs; however, due to a lack of permeability, gas shales almost always require fracture stimulation and often require higher well densities. Some shales, such as those in the Michigan Basin (Antrim), contain water which must be produced first to depressure the shale, similar to many NGC reservoirs.
A wide range of fracturing technologies have been used to allow the gas to flow through the reservoir, including:
- gelatinated nitroglycerine
- high-energy gas
- nitrogen and carbon dioxide foam
- liquid carbon dioxide
- cryogenic nitrogen
As well, horizontal drilling has been used to expose more of the formation to the well bore. Recovery rates for gas shales average approximately 20 per cent compared to up to 75 per cent for conventional reservoirs.
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