Three-Dimensional Outcrop Modeling of Late Cretaceous Point Bar and Channel Fill Deposits in the Horseshoe Canyon Formation, Alberta, Canada
Investigation of intra-point bar deposit heterogeneity in the subsurface is often limited to 1-D wellbore or 3-D seismic data, with neither capable of resolving correlations of individual accretion or erosion surfaces. This problem makes development well planning difficult for numerous fluvial reservoirs, including those of the bitumen-bearing Athabasca Oil Sands in northern Alberta. The Horseshoe Canyon Formation, exposed at the confluence of the Red Deer River and Willow Creek, Alberta, provides an excellent opportunity to investigate point bar distribution and internal heterogeneity at the outcrop scale. The objectives of this study are to: (1) create a 3-D model of laterally and vertically accreted facies within a tidally influenced meandering channel system; and (2) provide insight into the link between 1-D (well) and 3-D stratigraphic architecture within analogous hydrocarbon bearing-units (e.g., Cretaceous McMurray Fm.).
A series of lateral tributaries along the north flank of the Red Deer River valley provide continuous outcrop exposure along a 3 km long transect through the 12-16 m thick channel deposit, which erosively overlies marine shales of the Bearpaw Formation. The stratigraphic package is capped by organic rich shale and coal layers. The dataset consists of ~20,000 data points collected with a high resolution (10 cm) differential GPS unit that record the architecture of intra-point bar stratal surfaces and channel fills. >120 individual inclined heterolithic strata (IHS) surfaces were surveyed, as were a series of mudstone-dominated, vertically accreted channel fills. At least three distinct point bar packages are present, distinguished by sharp facies transitions from IHS-dominated units to more homogenous, sand-dominated units. All of these point bars contain basal trough-cross-bedded or massive sandstone units.
3-D projection of the laterally and vertically accreted surfaces within each depositional unit characterizes point bar migration patterns. Detailed sedimentology and facies analysis, accomplished through a series of measured sections, are used to populate the lithologic parameters within the 3-D model. Widespread trough-cross-stratification is measured in order to resolve paleoflow and hone projections of paleo-channel evolution. The dataset provides quantitative insight into the distribution of reservoir quality sandstone bodies and the lateral extent of mudstone layers in fluvial units dominated by IHS.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California