An overview of Canadian shale gas production and environmental concerns Christine Rivard a, ⁎, Denis Lavoie a , René Lefebvre b , Stephan Séjourné c , Charles Lamontagne d , Mathieu Duchesne a a Geological Survey of Canada, Natural Resources Canada, 490 rue de la Couronne, Québec, QC G1K 9A9, Canada b Institut national de la recherche scientifique, Centre Eau Terre Environnement (INRS-ETE), 490 rue de la Couronne, Québec, QC G1K 9A9, Canada c Consulting geologist, 5725 rue Jeanne-Mance, Montréal, QC H2V 4K7, Canada d Ministère du Développement durable, de l'Environnement, de la Faune et des Parc du Québec (MDDEFP), 675 boul René Lévesque Est, 8e étage, boîte 03, Québec, QC G1R 5V7, Canada abstract article info Article history: Received 14 June 2013 Received in revised form 20 November 2013 Accepted 1 December 2013 Available online xxxx Keywords: Canadian unconventional resources Shale gas Overview Utica Shale Production of hydrocarbons from Canadian shales started slowly in 2005 and has significantly increased since. Natural gas is mainly being produced from Devonian shales in the Horn River Basin and from the Triassic Montney shales and siltstones, both located in northeastern British Columbia and, to a lesser extent, in the Devonian Duvernay Formation in Alberta (western Canada). Other shales with natural gas potential are currently being evaluated, including the Upper Ordovician Utica Shale in southern Quebec and the Mississippian Frederick Brook Shale in New Brunswick (eastern Canada). This paper describes the status of shale gas exploration and production in Canada, including discussions on geological contexts of the main shale formations containing natural gas, water use for hydraulic fracturing, the types of hydraulic fracturing, public concerns and on-going research efforts. As the environmental debate concerning the shale gas industry is rather intense in Quebec, the Utica Shale context is presented in more detail. © 2013 Published by Elsevier B.V. 1. Introduction Natural gas is often considered a transition fuel for a low-carbon economy because it is abundant, efficient, and cleaner burning than other fossil fuels. Over the past decade, shale has been heralded as the new abundant source of natural gas in North America. The combination of technological advancements in horizontal drilling and in multi-stage hydraulic fracturing (“fracking” in industry jargon) techniques, as well as the progressive decline in conventional oil and gas reserves in North America, made shale gas the “energy game changer” over the last years. In addition, the fact that recoverable reserves of natural gas and oil in shales have been estimated to be large enough to potentially free the United States from a decade-long dependence on oil imports, and replace nearly all coal-generated electricity (Soeder, 2013), has probably largely contributed to making shale gas exploration and production increasingly appealing in this country. The United States was the first to economically produce shale gas from the Barnett Shale more than a decade ago; in 2013, there are over 40 000 producing shale gas wells spread across 20 states. However, natural gas prices have significantly decreased over the past several years, so that many shale dry gas plays (without liquid hydrocarbon production) are currently at the lower limit of economic profitability. Shale gas formations targeted by industry are generally located more than 1 km deep and under pressures sufficient to allow natural flow. Vertical wells must progressively be deviated to the horizontal to reach the target zone because the latter is typically relatively thin (50–100 m). Therefore, the horizontal part (termed a “lateral”) opti- mizes natural gas recovery by allowing the borehole to be in contact with the producing shale interval over significantly longer distances (and thus over a much larger surface area) compared to a vertical bore- hole. Almost all shale reservoirs must be fractured to extract economic amounts of gas because their permeability is extremely low, which impedes gas flow towards the production well. To increase their perme- ability, shales are typically fractured with fluids injected under high pressure, usually through a cemented liner or production casing that was selectively perforated. The fracking fluid used is specific to each operator and differs from one shale formation to another, depending, among other things, on the pressure gradient, brittleness (Poisson ratio and Young's modulus), clay content and overall mineralogy, hori- zontal stresses, and gas to oil ratio (GOR). Historically, the most com- mon fracking fluid used by the shale gas industry has been slickwater (a simple mixture of water, proppants (usually sand), friction reducers and other chemical additives) due to its low cost and effectiveness. More recently, shale reservoirs appear to be increasingly stimulated with a hybrid treatment consisting of slickwater used in alternation with a cross-linked gel purposely designed for a specific viscosity, with hybrid slickwater energized with N 2 or CO 2 , or with hydrocarbons such as gelled propane. International Journal of Coal Geology xxx (2013) xxx–xxx ⁎ Corresponding author. Tel.:+1 418 654 3173. E-mail address: crivard@nrcan.gc.ca (C. Rivard). COGEL-02241; No of Pages 13 0166-5162/$ – see front matter © 2013 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.coal.2013.12.004 Contents lists available at ScienceDirect International Journal of Coal Geology journal homepage: www.elsevier.com/locate/ijcoalgeo Please cite this article as: Rivard, C., et al., An overview of Canadian shale gas production and environmental concerns, Int. J. Coal Geol. (2013), http://dx.doi.org/10.1016/j.coal.2013.12.004