Not all shales are created equal:
Shale Gas Production in Northeast B.C. and Alberta

April 5, 2011

Shales are the most common sedimentary rock, comprising about 75% – 80% of the sedimentary rock record within the WCSB.  So why is all the shale gas activity apparently taking place in Northeast B.C.? Why are we not seeing a similar level of activity in Alberta shales? There are a number of reasons for this but the main reason is that shales are not all created equally

In addition, land disposition and the fiscal/regulatory regime between Alberta and BC have also influenced the pace of shale development to date.

Northeast B.C. shales were deposited in a favourable environment of deep water at the edge of the paleo continental margin where large amounts of highly organic material accumulated in great thicknesses and were preserved in a quiet oxygen deficient environment. In addition, B.C. shale plays are “thermogenic” in nature, which means the hydrocarbons have been generated as the result of the organic source rock being exposed to elevated temperature and pressure regimes. 

In Alberta, the shales were generally deposited in shallower water environments, resulting in thinner shale deposits where much of the organic material that accumulated was not always preserved.

Land disposition differences

Land disposition, in the form of Petroleum and Natural Gas (P&NG) rights are significantly less contiguous in Alberta than in B.C.  This is the result of a variety of conventional plays over the years spanning the landscape from relatively shallow wells to deep wells resulting in a virtual “checkerboard” of available crown land mixed with land that is held by existing production or deemed capable of production. 

The Horn River Basin for example was an area where there has not been significant historical or existing production and as such, large contiguous tracts of land were available to industry. The same, although to a lesser extent, can also be said for the Montney play which extends from the east of the Alberta-B.C. border west towards the Groundbirch area and north to the area around the town of Hudsons Hope. The Montney Formation, which is actually a “hybrid” shale play with tight siltstones deposited as ”turbidites” (underwater debris flows) into the deeper marine environment forming the bulk of the gas productive reservoirs in Northeast B.C. are also present on the Alberta side of the border, however a more favourable royalty regime in BC encouraged the BC side to be developed first.  Recent gas royalty changes in Alberta have levelled the playing field and one would expect activity on the Alberta side to accelerate and catch up as a result.   

Although there are a number of other Alberta gas shales that have development potential, they are not expected to rise to the same level of prominence and development as the BC shales primarily because of geology and the land availability situation. 

Duvernay Shale

The gas potential surrounding the Duvernay shales has been in the news recently with respect to some large land sales in the general Kaybob area. The Duvernay is widely recognized as an extremely rich organic shale and is credited as being the source rock for the oil and gas accumulations associated with the prolific Leduc and Nisku oil and gas fields across central Alberta. The Duvernay shales appear somewhat like a wedge with thicknesses approaching 60 metres meters in the vicinity of Leduc reef build-ups, but can thin dramatically to 5 metres away from the reef build-ups.  This complicates the development of the shale play as it becomes a relatively narrow target, making horizontal drilling and hydraulic fracking more challenging.  Regionally the Duvernay Formation is distributed within both the gas and the oil generation window. 

Other Shale Plays

The gas bearing Colorado shales have an extensive regional distribution over a large part of Alberta, however the gas has been biogenically derived from micro-organisms which results in less gas in place and because of relatively shallow depths, at a much lower pressure.  There is minor gas production associated with the Colorado shales in the Wildmere area of  Alberta, but unfortunately on an individual basis the wells produce at very low rates. The poor productivity is the result of lower original gas in place at lower pressures and higher clay content which makes the shales less brittle than their B.C. counterparts resulting in less effective hydraulic fracking. Although the low production rates are offset by low well costs of approximately $250,000 to drill complete and tie in. The play has not attracted much attention from industry and its future contribution to overall gas supply remains doubtful.

The Exshaw shale is an extremely organic rich source bed and in fact its equivalent, the Bakken shale is the focus of large oil developments in Montana, North Dakota and Saskatchewan. Within Alberta, the Exshaw would have potential inside the gas window however it is relatively thin (3-18 meters) which may be a significant barrier to large scale development involving horizontal drilling and hydraulic fracking.  

The Jurassic aged Fernie Group has potential as a shale gas, however the thickness is very thin and has a very low organic carbon content.  As well the Nordegg shale in the same area has some potential but is generally considered more of an oil source rock.  It is not likely that any companies are pursuing the Fernie Group at the present time.

The Wilrich shales cover a large area across northern Alberta and are equivalent to Lower Mannville. Unfortunately their organic carbon content is not consistent. Recently there have been encouraging local reports of commercial success with the Wilrich Formation, however it is doubtful that the Wilrich shales will be commercially developed on a regional scale.

In summary, although there is definitely gas potential associated with Alberta’s shales, they do not have the same potential for the scope and scale of development as the Northeast BC shales primarily because of geology. Aside from the Upper and Lower Montney Formation that extends into Alberta, the Duvernay has probably the greatest potential to develop into a significant Alberta shale gas play.

Alberta’s potential gas shale distribution

Illustration Credits:
Shale Gas Potential of Selected Upper Cretaceous, Jurassic, Triassic, and Devonian Shale Formations, in the WCSB of Western  Canada: Implications for Shale Gas Production
GTI E&P Services Canada Inc. 2002

Further Information