Earth Sciences Report 2007-04

Earth Sciences Report 2007-04

ESR 2007-04

Ardley Coal Zone Characterization and Coal-Sandstone Channels Architecture in Pembina Block

Author(s) Pana, C. Date 2007-03-01

A major area of economic interest motivated the study of Ardley coal zone characterization and coal-sandstone channels architecture in the Pembina Block. The economic importance of the coalbed methane (CBM) exploration and development in the Ardley coal zone and the emerging interest of CO2-ECBM in the Pembina CBM exploration block to release maximum exploration benefits, leads to better understanding of the relationship of the coal sequences and the reservoir characteristics.

The present study integrates the new detailed coal and stratigraphic picks for the Pembina CBM exploration block with the pressure and water chemistry data publicly available. As the result, the detailed interpretation of the Pembina exploration block indicates the areas with high CBM potential (coal thickness and continuity, coal quality, optimum depth, fracture pattern, etc.) and outlines the potential long term risk of the CO2 storage in the Ardley coal strata.

The report consists of three parts: the first part presents an overview of the Scollard-Paskapoo succession interpreted in response to the adjacent tectonic activity and climatic regime; the second part is focused on the Pembina CBM exploration block where the Ardley coal zone have been systematically analysed regarding the coal properties, coal zone internal structure, hydrogeology and fracture patterns; the last part of the report contains the definition of the channels intervals and the coal-channels architecture as potential paths of fluid migration.

As the result of this study, in the Pembina exploration block have been recognized five fluvial sequences and interpreted as dynamic responses to the cyclic slow thrusting tectonic stages followed by isostatic rebounding. The depositional environments favourable to coal accumulation migrated from the north-west during Mynheer to the central area during Silkstone depositional time and to the south-east in Arbour and Val D'Or time. Coal sub-zones can be considered individual reservoirs due to the particular geometry and sealing the coal packages. The examined drillcores have shown that banded coal category is the dominant type of coal in the Pembina block. Cleats free of calcitic infillings are dominant. Vitrinite reflectance is 0.54%-0.59% within the onset of hydrocarbon generation. Interpretation of the fracture system suggests two areas of potential two-face-cleats systems north-west and south-east of the North Saskatchewan River. In addition, differential compaction locally may amplify the existing cleats or generate additional fractures at the contact of coal seams with sandstone channels. Scollard-Paskapoo succession in the Pembina exploration block is considered an unconfined aquifer, based on the formation pressure and water salinity analyzed data. Gas-in-place shows for the Ardley coal zone a total of 323 *109m3 with the increase of gas estimative content from Val D'Or (62 *109m3 ) to Mynheer coal sub-zone to (104 *109m3). The sandstone channels and the underlying coal seams show a direct stratigraphic contact in some locations which may allowed to methane to migrate. Both types of reservoirs may inherent permeability. However, at geological time scale, they can be considered potential gas migration paths in the CO2-ECBM strategy. It consists of text, 96 figures (i.e., stratigraphic models, 62 maps, 10 cross-sections) and 12 plates with photgraphs of the lithological componens (sandstone, mudstone-siltsone, coal and tonstein).

Pana, C. (2007): Ardley Coal Zone characterization and coal-sandstone channels architecture, Pembina CBM exploration block, Alberta; Alberta Energy and Utilities Board, EUB/AGS Earth Sciences Report 2007-04, 152 p.