ABSTRACT

The Triassic Charlie Lake Formation of west-central Alberta represents a geologically complicated and underexploited sequence. Stratigraphic complexities within the formation necessitate detailed lithostratigraphic analysis for successful exploration. The complexities observed are a result of three

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intra-Charlie Lake unconformity surfaces, identified as the Coplin, Boundary, and Worsley and by post-Triassic erosion at the base of the Jurassic Nordegg Formation. These unconformity surfaces bound four depositional sequences, the Lower Charlie Lake, Boundary, Upper Charlie Lake, and Worsley intervals. Erosional removal of each interval occurs as the unconformity surfaces converge toward an eastern Charlie Lake subcrop.

Recently, several significant oil pools within the Charlie Lake have been found in a fairway paralleling its subcrop edge (Manir, Kakut, Rycroft, Cecil). Production from reservoir quality dolomite and dolomitic sandstone along the subcrop edge is found within each of the four depositional sequences. The development of reservoir facies is controlled mainly by original depositional facies, whereas the present distribution of reservoir facies is primarily unconformity related. Three unconformity related play types are recognized: the regional updip subcrop edge of porous units, erosional remnants or outliers, and erosional inliers. Successful exploration for these play types requires continued detailed analysis of the depositional, erosional, and structural history of the Charlie Lake Formation.

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