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UBC Theses and Dissertations

Reservoir characterization of the Duvernay Formation, Alberta : a pore- to basin-scale investigation Munson, Erik Ole


The reservoir properties of the Duvernay Formation mudrock gas and oil (“shale gas”) reservoir in Alberta were investigated. The investigation included an assessment of current methodologies utilized to study mudrocks, development of new methodologies, pore- to basin-scale characterization and integration of core data with wireline logs. The Duvernay exists over multiple thermal maturity boundaries and provides a laboratory to investigate numerous pertinent research questions. Deposition of organic-rich Duvernay mudrocks was controlled by the spatial relationship to Leduc reef complexes. Greater thicknesses (> 70 m) of Duvernay mudrocks are found within embayments where oxygenated water circulation was most restricted. The Duvernay progressively thins (< 5 m) to the basin center where organic-lean lime mudstones were deposited instead of Duvernay mudrocks. Core samples were taken from eight wells to form a high-resolution database of rock properties including mineralogy, total organic carbon (TOC) content, and total porosity. Duvernay mudrocks average between 2.4 % and 5.6 % total porosity and between 3.0 % and 4.4 % TOC per well. A regional lime mudstone within the Duvernay averages less than 2 % porosity and 0.5 % TOC and therefore is considered to be of poor reservoir quality. Artificial neural network models were used to successfully integrate laboratory data with wireline logs to predict rock properties in wells without laboratory data, providing enhanced correlation coefficients over linear regressions (R=0.82 versus R=0.67). The pore structure of Duvernay mudrocks varies systematically with thermal maturity. Fine pore sizes (micro- and fine mesopores) hosted within organic matter progressively increase in volume as thermal maturity increases. Coarse pore sizes (coarse meso- to macropores) progressively decrease in volume with increasing burial depth due to compaction. Wet and dry gas window samples have average pulse-decay permeabilities (PDP) an order of magnitude higher (1.8 x 10-⁴ mD) than oil window samples (1.6 x 10-⁵ mD), despite the shift in pore modality to finer sizes. The network of fine pores developed with maturity and associated with organic matter is sufficiently connected to contribute to higher PDP values. Gas expansion permeability experiments further indicate fine pores are connected and yield increased matrix permeabilities.

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