Open File Report 2009-16

Preliminary Investigation of Potential Natural Hydraulic Pathways Between the Scollard and Paskapoo Formations in Alberta: Implications for Coalbed Methane Production

Authors: Parks, K.; Andriashek, L.D.

Executive Summary

This report presents the preliminary results of an investigation to assess risk to groundwater in the Paskapoo Formation from potential hazards associated with future coalbed methane (CBM) production in the Ardley Coal Zone of the Scollard Formation.

The investigation focused on two key hydrogeological components:

1) the degree of hydraulic connectivity between the Ardley coals and the Paskapoo Formation, and

2) the degree of hydraulic connectivity and hydraulic continuity within the Paskapoo Formation itself.

If there is connectivity between the Ardley Coal Zone and the Paskapoo Formation, the probability of it affecting the groundwater depends on

1) the degree of regional interconnectivity of the sandstones in the Paskapoo Formation, and

2) the degree of hydraulic continuity between a given Ardley CBM development and users of Paskapoo groundwater over the time scale of that CBM production.

We can estimate the degree of regional interconnectivity from sandstone-abundance maps using concepts of percolation theory. Percolation concepts suggest that, when regional sandstone abundances are less than 40%, sandstone bodies in the Paskapoo Formation may be locally connected but probably not regionally connected. When regional sandstone concentrations are greater than 60%, the Paskapoo sandstone bodies probably interconnect at the regional scale as well as the local scale. The threshold marking the change from local-only to local-plus-regional interconnectivity occurs somewhere between 40% and 60% sandstone.

As in all geological investigations that rely on sparse data from wells, there is uncertainty in the conceptual model developed in this report. Further studies can reduce but not eliminate this scientific uncertainty. Studies that would probably advance our understanding of the Ardley-Scollard-Paskapoo system include

- investigating the role of fractures at depth;

- investigating the reservoir qualities and internal hydraulic continuity of coal beds in the Ardley Coal Zone; and

- testing the robustness of the conceptual model through more sensitivity analysis of the parameters chosen to map the internal architecture of the Paskapoo Formation, including petrophysical cut-offs and slice-thickness magnitudes and orientations.

Place Keywords: 82i; 82j; 82n; 82o; 82p; 83a; 83b; 83c; 83d; 83e; 83f; 83g; 83h; 83i; 83j; 83k; 83l; 83m; 83n; 83o; 83p; 84a; 84b; 84c; 84d; alberta foothills; alberta plains; canada

Theme Keywords: ardley coal zone; coalbed methane; geology; groundwater quality; hydrogeology; paskapoo formation; scollard formation