Natural Gas Facts
GOVERNMENT OF ALBERTA
What is shale gas?
Shale gas is natural gas stored in organic rich rocks such as dark-colored shale, interbedded with layers of shaley siltstone and sandstone. Shale can be the source, reservoir and the seal for the gas. Shale gas plays are classified as a “continuous” type gas accumulations extending throughout large areas, typically with low permeability and perhaps natural fractures. Shale gas plays in Canada are expected to have low production rates over a production life of perhaps 20 to 30 years.
Why is shale gas considered unconventional gas?
Shale gas is considered an unconventional source as the gas may be attached to or "adsorbed" onto organic matter. The gas is contained in difficult-to-produce reservoirs that require special completion, stimulation and/or production techniques to achieve economic production. Shale gas may also be contained in thin, porous silt, sand and beds interbedded in the shale. In this case, the gas is classified as ‘free gas’ and is produced along with the adsorbed gas.
Why is Alberta seeing increased industry interest in shale gas development?
As conventional gas plays in Alberta continue to mature, industry looks towards other potential gas sources for development. The United States is currently utilizing technology to economically develop sources of unconventional gas such as shale.
Estimates of shale gas within the Western Canada Sedimentary Basin resource vary from 86 trillion cubic feet (Tcf) to over 1000 Tcf. While there is huge potential in Alberta, shale gas production is in very early stages and commercial development is not likely to occur in Alberta for a number of years. This energy source has the potential to make a significant contribution to Alberta’s future natural gas supply.
How much shale gas is there in Alberta and where will it be found?
Shale makes up the majority of the sedimentary section in the Western Canada Sedimentary Basin (WCSB) with potential targets in the Cretaceous, Jurassic, Triassic, Mississippian and Devonian shales. Alberta Geological Survey (AGS) has identified about 15 prospective shale gas formations.
While it is not known how much of the shale gas can be economically produced, current experience regarding the development of unconventional gas sources suggests recoverable reserves are about five to ten per cent of the resource potential.
How are shale gas wells drilled?
The same techniques used for conventional shallow gas development may also be used with shale gas drilling. Some shale gas development can be horizontally drilled which will help reduce the surface impact. However, not all areas may be conducive to horizontal drilling. Drilling pads, from which multiple wells are drilled, can also be used to reduce the area of surface impact.
How will shale gas be produced in Alberta?
In order to produce economic quantities of gas, shale gas wells need to be stimulated by artificially fracturing the formation. Some wells will be fractured multiple times during their production history. The initial flow after each fracturing may be elevated to near the initial rate of flow. However, this is typically followed by a steep decline in production.
How is shale gas regulated in Alberta?
Alberta has extensive experience in the development of energy resources and has a strong regulatory framework already in place. Shale gas is regulated under the same legislation, rules and policies required for conventional natural gas. The Energy Resources Conservation Board (ERCB) regulates exploration, production, processing, transmission and distribution of natural gas within the province.
How many wells per section will have to be drilled?
It is predicted that about two to eight shale wells will be drilled per section to effectively produce shale gas in Alberta. There can be multiple zones of potential in Alberta within a shale gas play, both from conventional and unconventional gas production. This could result either in commingling of gas zones or more than two to eight wells per section being drilled, subject to Energy Resources Conservation Board regulations.
How much water will be produced with the shale gas?
In Alberta, there is limited shale gas production and, to date, most shale gas activity has focused on research and development. Thus far, there has been no water production from Alberta shale gas wells.
The United States has had more experience and development in shale gas. In most areas of the United States, shale gas is typically “dry” with little or no water associated with the gas production.