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Abstract: Sequence Stratigraphy and Reservoir Geology of the Glauconitic Sandstone Member and Adjacent Strata, Mannville Group, Central Alberta

OKARO, PATRICK I.

The lower Cretaceous Mannville Group constitutes part of a wedge of siliciclastic strata which was deposited in the foreland basin of the Cordilleran orogen in Western Canada. Enormous gas reserves are hosted within the Glauconitic sandstone in progradational shoreline successions informally called the Hoadley complex. Continued development of the reservoir using previously established stratigraphic models has revealed poorly understood trends, not predicted by current sequence stratigraphy.

Specific goals of this study are to: (i) Build a sequence stratigraphic framework for the unit integrating the stratal discontinuities (flooding surfaces etc.), lithofacies and ichnofacies recognized in core with wireline log stacking patterns, glaucony facies, clay and sandstone mineralogy, palynomorph trends and isotope data; (ii) Document the dimensions, orientations and internal heterogeneities of reservoir facies and determine controls on reservoir quality; and (iii) Predict reservoir trends and determine controls on sequence development.

My initial mapping indicates that parasequences within the Glauconitic are readily mappable and bounded by flooding and ravinement surfaces. Sandstones of progressively younger parasequences clinoform and downlap on older parasequences. Within the previously defined allomembers, readily identifiable and correlatable stratal discontinuities (ravinement surfaces etc.) exist. At the parasequence scale, sandstones with dominant detrital quartz (66 - 75%) have permeability's ( 10 200 mD) one to three orders of magnitude higher than units with significant detrital dolomite and rock fragments (0.1 - 5 mD). Within each parasequence, preferentially permeable facies coincide with the foreshore facies. It is obvious that the best well deliverability is found some distance seaward (NW) of the updip termination of a parasequence. 

AAPG Search and Discovery Article #90940©1997 AAPG Foundation Grants-in-Aid