Shale Gas

Shale is one of the most common sedimentary rocks in the world and it is primarily composed of clay and fragments of other minerals such as quartz and calcite.  Shale can be the source, reservoir and the seal for natural gas.  Shale formations normally have low permeability (limited ability for gas or fluids to flow easily through the shale formation) and normally require stimulation techniques (such as fracturing) to economically produce shale gas.  Shale gas is natural gas that is attached to, or "adsorbed" onto, organic matter or is contained in thin, porous silt or sand beds interbedded in the shale.

The following information sources provide a good introduction to shales:

National Energy Board:  A Primer for Understanding Canadian Shale Gas 

Energy Resources Conservation Board: 

U.S. Department of Energy:  Modern Shale Gas Development in the U.S. 

Shale gas is unconventional gas

Shale gas is considered an unconventional source as the gas is contained in difficult-to-produce reservoirs, which require special completion, stimulation and/or production techniques to achieve economic production.

Industry is interested in developing Alberta’s shale gas

As conventional gas plays in Alberta continue to mature, industry is looking towards other potential gas sources for development.  Shale has the potential to make a significant contribution to Alberta’s future natural gas supply as advancements in drilling and completion technologies allow the economic development of some shale gas resources.

Alberta’s shale gas and where it is found

The Alberta Geological Survey (AGS) has identified about 15 prospective shale gas formations.  The Gas Technology Institute estimates Alberta has approximately 850 trillion cubic feet (Tcf) of shale gas in place.  Given its very early stages of development in Alberta, it is not yet known what portion of these resources can be economically produced.  The ERCB is currently evaluating the shale gas resource potential of all prospective shale gas formations in Alberta.

Shale gas production

The same techniques used for conventional shallow gas development may also be used with shale gas drilling.  Shale gas can be produced from vertical and directional wells.  However, due to the low permeability that is characteristic of shale formations, stimulation techniques such as horizontal drilling and multi-stage hydraulic fracturing are often required to achieve economic production.  The majority of Alberta’s production is achieved using vertical wells along with a few horizontal wells.  Vertical and directional shale wells are commonly commingled with other production zones to yield economic production.

 In recent years, improvements in the use of horizontal drilling combined with multi-stage fracturing have resulted in some shale gas formations becoming some of the most attractive natural gas resources in North America.

Shale gas development in Alberta is still in its early stages.  The number of connections producing shale gas in Alberta (each well bore can have more than one connection) has only increased from 5 connections in 2000 to 142 connections in 2010. 

Determining the number of wells per section

Shale gas can be developed using various drilling and completion methods depending on the reservoir’s characteristics but generally, due to its low permeability, 8 to 16 subsurface drainage wells per section are required to effectively recover the underground gas in a shale play.  

Thermogenic shale gas, normally formed during deep burial where heat and pressure cook the organic matter releasing natural gas, is often developed using horizontal drilling and multi-stage hydraulic fracturing.  These techniques can be combined with multi-well pad drilling to reduce the number of well sites per section that are needed.  The production from one horizontal wellbore with 10 fracture stages may in some cases be equivalent to drilling 10 vertical wells with a single fracture each.

As of July 2011, shale gas production in Alberta has not used the horizontal drilling with multi-stage fracturing methodology commonly used in other jurisdictions.  Instead, shale gas development in Alberta has occurred primarily through the use of vertical wells as well as a few horizontal wells.

The Alberta Energy Resources Conservation Board (ERCB)  regulates well spacing.

Regulating shale gas development in Alberta

Alberta has extensive experience in the development of energy resources and has a strong regulatory framework already in place.  Shale gas is currently regulated under the same legislation, rules and policies as conventional natural gas.  Although shale gas development in Alberta has not been using horizontal multi-stage fracturing, Alberta does have extensive experience with hydraulic fracturing.  Approximately 167,000 wells have been hydraulically fractured in Alberta since the technology was introduced more than 50 years ago.

Most aspects of the oil and gas industry are regulated in Alberta by the Energy Resources Conservation Board.  The ERCB sets requirements for drilling and production operations.  The ERCB protects our fresh water aquifers (groundwater) with strict regulations that are designed to ensure that gas cannot migrate up a well bore to contaminate groundwater sources.  Well bores are required to have cemented casings in place that meet stringent requirements and which are also set to depths far below any fresh water aquifers.  This ensures there is an impenetrable barrier between the shale gas formation and the well bore so that gas and fluids are unable to use the well bore as a pathway to contaminate groundwater.

Alberta has strict requirements in place to manage the safe disposal of produced fluids (fluids that return to the well head as part of the hydraulic fracturing process) and does not allow produced fluids to be sent to municipal waste water treatment systems.  Fluids that cannot be treated and recycled must be disposed of in approved disposal wells where the fluids are injected deep underground for permanent disposal.

The ERCB has not documented any cases of groundwater being contaminated as a direct result of hydraulic fracturing.

Government Links:

Alberta Environment      www.environment.alberta.ca/

Alberta Geological Survey    www.ags.gov.ab.ca/

National Energy Board    www.neb-one.gc.ca/