Reservoir Geometry of a Confined Fluvial Meander Belt Deposit, Early Cretaceous Grand Rapids Formation, Alberta

Abstract

Deposits of a confined single storey fluvial meander belt 650 to 2000 m wide and 15 to 21 m deep are analyzed from the Early Cretaceous Grand Rapids Formation in the subsurface in northeastern Alberta, Canada. These deposits constitute a portion of the approximately 100 billion barrel Cold Lake heavy oil sands area. A section of the meander belt covering approximately 4 sections (10 km²) in area containing 68 wells with varying core control and 5 km² of seismic is studied in detail to constrain the stratigraphic architecture and facies distribution of the bar forms composing the meander belt. Seismic time slices reveal evidence of downstream accreting point bars in narrower reaches of the meander belt in addition to point bars dominated by lateral accretion in wider portions. Sediment distribution along the meander belt was determined by using gamma radiation contour mapping, a technique whereby gamma ray values from wireline logs are averaged over three metre intervals down from a datum at the overlying flooding surface to the base of the meander belt that are then plotted as a succession of maps. Trends in gamma ray values on the resulting maps demonstrate upward fining and downstream fining of sediments within point bar deposits associated with downstream and lateral accretion. An abrupt increase in gamma ray values downstream of the bend apex demonstrates deposits associated with a counter point bar. Narrow, deeper portions of the meander belt with relatively low gamma ray values may be associated with eddy accretion. Given the breadth of scale and composition of these point bars and counter point bars, the impact on pore volume and fluid flow is highly varied along the meander belt.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016