INNOVATION May-June 2012

Fort St. John

“ Water is critically important for development of tight and shale reservoirs, as huge volumes

Dawson Creek

of water are required to execute frac jobs ”

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Alberta

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clf-nsi/rnrgynfmtn/nrgyrprt/ntrlgs/hrnrvr/hrnrvrm-eng.pdf). Both gas-in-place and marketable gas are reported on a probabilistic basis (to address the necessary assumptions), with marketable gas estimates ranging between 61 and 96 trillion cubic feet (TCF) . These are huge numbers, and are subject to upward revision in the future as more information is gathered. A similar study on the Montney Play fairway is currently being undertaken by these agencies. Water and Unconventional Oil and Gas Development Water is critically important for development of tight and shale reservoirs, as huge volumes of water are required to execute frac jobs—up to tens of thousands of cubic metres per well in the Horn River Basin. Water’s role is to transmit pressure downhole to break the reservoir rock open (frac it), then to carry proppant (high-grade sand grains) into the fractures to prop them open and maintain flow fairways once the well begins producing gas or oil. Some of the water remains in the formation, while some flows back with the gas. This flowback water retains some of the chemicals added to the frac job and picks up traces of various rock materials underground, and so it must be captured and recycled or safely disposed to avoid contamination of fresh waters at surface. Different reservoirs require different completion methods, and operators spend considerable time and money optimizing their completion procedures. In general, however, shale gas reservoirs, as in the Horn River Basin, require very large water volumes for completions, while lesser volumes energized with gaseous nitrogen or carbon dioxide are optimal for many tight gas reservoirs, including much of the Montney. There are three primary water sources available to make up frac fluids: • Surface waters such as lakes and streams; • Shallow aquifers carrying fresh water, either bedrock or buried river channels or glacial stream channels; and • Deeply buried bedrock aquifers, which generally contain naturally occurring saline waters that are not suitable for human consumption or agriculture.

Figure 2. Map showing net thickness (in metres) of porous Cadomin Formation aquifer in the eastern Montney play fairway.

Although fresh surface waters are usually most easily accessible, some producers now prefer to utilize deep saline waters if technically and economically feasible in order to avoid real or perceived conflicts over fresh water use with other stakeholders. Disposal of flowback and produced waters must be to deep saline aquifers as they cannot be safely released into freshwater environments. British Columbia is a world leader in assessment of aquifers and water resources associated with unconventional gas plays. Geoscience BC, a government-funded, not-for-profit organization charged with undertaking geoscience work to support exploration in BC (www.geosciencebc.com), has completed two major assessments. A comprehensive study of deep saline subsurface aquifers in the Horn River Basin, undertaken in cooperation with the Horn River Basin Producers Group, identified the Debolt Formation (buried at a depth of several hundred metres) as an excellent saline water source and disposal zone (Figure 1). The Encana/Apache partnership has completed a major water treatment facility which draws water from the Debolt, and supplies almost all the water used for drilling and completions by those operators. It also facilitates the disposal of flowback and produced waters that are too saline to recycle into the Debolt Formation. Follow- up work in defining shallow subsurface aquifers (as water sources in areas where the Debolt aquifer is poorly developed) is now being sponsored by Geoscience BC. In addition, Geoscience BC and the Horn River Basin Producers Group have initiated a three- year surface water monitoring study, which will collect baseline climatic, hydrometric and water quality information from locations throughout the Horn River Basin. Members of the Fort Nelson First Nations and Echo Dene Kho are participating in the project

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