--> Abstract: Basal Quartz Sandstone (Lower Cretaceous), South-Central Alberta: Non-Marine Deposition In An Accommodation Limited Basin, by R. W. C. Arnott, B. A. Zaitlin, and D. Potocki; #90928 (1999).

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ARNOTT, R. W. C.1, B. A. ZAITLIN2, and D. POTOCKI2
1Dept. of Geology, University of Ottawa, Ottawa
2Pancanadian Petroleum, Calgary

Abstract: Basal Quartz Sandstone (Lower Cretaceous), South-Central Alberta: Non-Marine Deposition in an Accommodation Limited Basin

In southern Alberta the "undifferentiated Basal Quartz", hereafter termed "BQ", consists of non-marine strata that although are generally <20 m thick represent ~35 my of geological time. Within the study area (~20 km2) "BQ" oil production is mostly from the Horsefly (6.4 x 103 m3 OOIP) and Chin Coulee (4.1 X 103 m3 OOIP) pools, with minor production from the Mannville D Pool. Significantly, although the stratal architecture of the "BQ" in each of the pools is similar, consisting of late lowstand braided fluvial deposits overlain conformably by transgressive systems tract meandering fluvial deposits, there are important differences in many other geological and production characteristics. For example, although both Horsefly and Chin Coulee pools form infinite reservoirs, the recovery factor in Horsefly Pool is significantly lower, 19% versus 27.3% Furthermore, Mannville D Pool forms a finite reservoir and consists of a mineralogical assemblage distinctly different from the other pools.

Within the study area, therefore, the "BQ" is interpreted to consist of a complex stratal succession of different-aged incised valley fills. Much of this complexity, however, is related to the long-term accommodation-limited nature of the basin. As a result valley terrace deposits are common along the margins of younger valley fills, which in this case consist of poorer reservoir quality strata forming finite- or non-reservoir units. Recognizing these strata and delineating their areal distribution, therefore, is essential in the planning of a successful in-fill drilling program.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas