ABSTRACT

Although the relationship between geological framework and reservoir performance has long been recognized, it has only been in the last decade or so that detailed geological models have become an integral part of any reservoir maintenance plan. In a case study of the conglomeratic Cardium (Turonian-Coniacian) Carrot Creek "K" Pool (Twp. 51-52, Rge. 13W5M), it was recognized that the areal distribution of reservoir quality (porosity/permeability) was directly related to a predictable depositional framework -- a wave-reworked distributary mouth-bar complex.

The Carrot Creek "K" Pool is a narrow, elongate, northwest-southeast trending conglomeratic reservoir unit. Detailed core and log analyses indicate that the reservoir consists of two lithostratigraphic units: an underlying, fine grained regressive unit (with little or no reservoir quality), and an overlying conglomeratic transgressive unit (representing the main reservoir). Separating the two units is a regional unconformity, or sequence boundary; remnant topography on this surface was an important factor controlling the areal distribution of gravel deposition during development of the reservoir-bearing transgressive unit. In addition, conglomerate of the transgressive unit consists of both matrix-supported and clast-supported types; reservoir quality is highest in the clast-supported type. Matrix-supported conglomerates are confined to the western (paleolandward) side of the "K" Pool area and are interpreted as braided distributary stream deposits associated with a conglomeratic distributary mouth-bar complex. Clast-supported conglomerates occur eastward (paleoseaward) of the matrix-supported conglomerates and are interpreted as having been deposited on an open marine shoreface/beachface. They are the result of wave reworking and redistribution of sediment sourced principally from the distributary mouth-bar complex. Knowledge of lithofacies distribution within the Carrot Creek "K" Pool is essential to an understanding of reservoir quality distribution and prediction of permeability pathways within the reservoir. This can be of benefit in the design and implementation of pressure maintenance programs or enhanced recovery techniques.

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