Abstract

Regional surface and subsurface correlation of the upper Belly River Group clastic wedge confirms that the Dinosaur Park Formation is present throughout most of southern and central Alberta. The Dinosaur Park Formation, part of a relatively distal and primarily transgressive third-order succession, is dominated by thick multistoried sandstone units in its lower portion and siltstone to coal in its upper portion. The Dinosaur Park generally thins to zero to the south due to depositional thinning. Within that framework, thickness variation of the Dinosaur Park in southern Alberta is characterized by relatively narrow, linear trends, generally oriented WNW/ESE, which fan out from locii near Rocky Mountain House, Sundre and Calgary, and result primarily from localized erosional geometry at the base of the formation. Linear trends are sharp-based, and are overlain by multistoried, fining-upward channel sandstone units, interpreted as composite incised valley fills. Corresponding clean sandstone trends (potential reservoir rock), are up to 40 m thick. Based on abundant outcrop paleocurrent data from this and other studies, the sediments of the Dinosaur Park were derived from the northwest and dispersed toward the southeast. The regionally consistent upward succession of facies from erosional base, to sandstone-dominated deposits (derived from the northwest), to sandstone/mudstone-dominated strata, to Lethbridge Coal Zone, to Bearpaw marine shale (transgression from the southeast) is interpreted to represent a fundamental reorientation of paleogeography related to an overall increasing rate of basin subsidence, and consequent transgressive pressure, in southern Alberta. An interpreted initial, rapid and extensive base level fall, due to tectonic quiescence, resulted in basinwide rebound and erosion, and was followed by deposition of an overall transgressive succession during increasing base level rise related to widespread subsidence during a phase of renewed tectonic thrust loading. The formation encloses 137 discovered gas pools with discovered in-place reserves of 4,686X10 6 m 3 , but the presence of large areas of thick, clean sandstone with no designated pools, suggests further exploration possibilities. The Dinosaur Park Formation play is ranked first in expected potential among post-Colorado gas plays with an expected potential in-place volume of 25,283X10 6 m 3 . More detailed mapping of individual sandstone bodies in high potential areas is necessary to exploit these resources.

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