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Bulletin 2009-23

July 9, 2009

Shale Gas Development—Definition of Shale and Identification of Geological Strata

The purpose of this bulletin is to clarify the definition of shale for shale gas development and to identify the geological strata from which any gas production will be considered by the Energy Resources Conservation Board (ERCB) to be shale gas.  Each well producing gas from shale must have ERCB-designated control wells as specified in Sections 1.020, 7.025, and 11.145 of the Oil and Gas Conservation Regulations (OGCR).

Section 1.020(2)(27.1) of the OGCR defines shale as “a lithostratigraphic unit having less than 50% by weight organic matter, with less than 10% of the sedimentary clasts having a grain size greater than 62.5 micrometres and more than 10% of the sedimentary clasts having a grain size less than 4 micrometres.” Using this definition, the ERCB has categorized shale gas strata as follows:

1)  Shale Gas Strata
Gas produced from the organic marine shale formations, members, and informal strata listed in Table 1 is considered to be shale gas. These shales, formations, members, and informal strata are marked as Resources Occurrence—Shale Gas Potential in the ERCB Table of Formations, with the exception of the Doig Phosphates, which is not depicted. The Table of Formations is available on the ERCB Web site www.ercb.ca under Publications : Publications Available : Maps and Shapefiles.

In some instances, localized sandstones or porous carbonate units may be present within strata identified in Table 1. Any production from these units, where clearly identifiable, would be deemed conventional gas production.

Further updates are anticipated to Table 1 as more data become available and will be communicated in future bulletins.

2)  Southeast Alberta Colorado Group Strata
Within Townships 1 to 35 for all ranges between the 4th and 5th Meridian, all strata between the top of the Milk River Formation and the Base of Fish Scales marker are currently designated as conventional gas. While some of these zones meet the definition for shale, because of the long history of gas production in this area and for administrative efficiency, the gas produced from these strata will not be redesignated as shale gas.

3)  Mixed Lithology Strata
For strata where shale is not the primary lithology, a variety of information may be required to determine if the perforated interval falls within a shale zone. For example, core descriptions and analysis, detailed log evaluation, or other tests would assist in determining if the interval is producing shale gas.

The above three categories of shale gas strata may be modified (strata added or removed) as additional information becomes available.
 

Table 1.    Shale gas strata ¹

¹ The columns are arranged by listing the strata from youngest to oldest.
²  These names are used informally in Alberta.

For further information, contact Sharleen Ramos, Coal and Unconventional Gas Section, at 403-297-2190 or sharleen.ramos@ercb.ca.

<original signed by>

Cal Hill
Acting Executive Manager
Geology, Environmental Science, and Economics Branch