Surface Geochemical Imaging of the Tweed Lake Cambrian Field, Northwest Territories Canada

Robert O. Potter¹ and Paul Harrington^2
1GeoChemTech Inc., Calgary, AB, Canada.
²Gore Surveys, W. L. Gore & Associates, Inc.., Elkton, MD.

Gas/condensate and oil has been discovered in the Cambrian sandstones reservoirs of the Mount Clark Formation in the Northwest Territories of Canada. The Mount Clark reservoir occurs at a depth of 1000 to 1400m with net pays of 10 to 12m. Subsequent deposition of the Saline River Formation resulted in a thick section of evaporates and salt up to 500m thick.

It is estimated that the trend contains 84 structural prospects varying in area from 4 to 150 square kilometers. The undiscovered gas in place is estimate to be 5,791 Bcf contained in about 77 undiscovered fields (Natural Gas Potential in Canada 2001; Canadian Gas Potential Committee).

In the winter of 2007, a large surface Amplified Geochemical ImagingSM survey was conducted that included the Cambrian Tweed Lake pool as the geochemical model. A total of 48 modules were installed in the Tweed Lake area around two wells (M-47 and C-12) and along a northeast-southwest seismic line.

Once retrieved, all samples were analyzed by thermal desorption followed by gas chromatographic separation and mass selective detection. After signal to noise processing, statistical methods involving principle component analysis and discriminate analysis was applied to the data set to define the unique hydrocarbon signatures related to different hydrocarbon phases in the subsurface.

The geochemical model was developed using the M-47 and C-12 wells as the end-member set to collectively define their respective “gas/condensate-like” and “background-like” emanation signatures in two-way discriminant analysis.

The Tweed Lake C-12 dry well site defined the background in the Colville Hills area. This well is located ten kilometers from the Tweed Lake M-47 gas/condensate discovery well. Linear discriminant analysis was used to make a geochemical model of the gas/condensate.

The results for the Tweed lake M47 gas-like model in Colville Hills identified a geochemical feature at least 3.5 kilometers along the transect over the Tweed Lake field. The geochemical feature truncates along the transect 1.5 kilometers northeast of the Tweed Lake M-47 gas well and appears to closely correlate to the fault that defines the eastern edge of the Tweed Lake pool.

AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.