Using Borehole Electrical Images in Modeling a McMurray Formation Heavy Oil Reservoir in NE Alberta

T. Cupkovic, P. Fothergill, and B. Rahman
Schlumberger DCS, 525 – 3 Ave S.W., Calgary, AB, T2P 0G4

In the Athabasca Oil Sands, clastic deposition of the Lower Cretaceous McMurray Formation took place in a combination of fluvial, estuarine and coastal plain environments. In general, lower McMurray sands were fluvially deposited, within paleovalleys formed in the underlying Devonian carbonates. In the upper McMurray, however, reservoirs are typically found in estuarine channel, point-bar and tidal flat environments. Common sedimentary structures include: trough cross-bedding in the channel dominated environments; inclined hetereolithic stratification (IHS), associated with lateral accretion of estuarine point bars; and flaser or wavy bedding in the sand or mud flat facies. Reservoir quality can vary considerably over very short distances. Therefore, developing an in-depth understanding of lateral and vertical variations in lithofacies, at both a single-well and field-wide scale, is important for optimizing production operations and planning future well locations.

In this project, high resolution FMI images from a set of vertical wells were used to carry out a sedimentological interpretation of the McMurray Formation deposits. The texture of the FMI images, together with the dip and azimuth of the different sedimentary structures, were used to define a facies zonation, which could be applied across all the wells. Where possible, the results were compared and calibrated against the core, in order to produce the most reliable data. Correlations were then made between neighbouring wells to help interpret spatial variations in the subsurface geology. Finally, the facies from each of the studied wells were upscaled and used to produce a 3D static reservoir model over the area of interest.

This technique enables high resolution borehole image and dipmeter data to be used to construct more detailed and geologically accurate reservoir models. It can be used to help refine existing reservoir models, built predominantly using seismic data, or construct new models where no seismic is available. It is particularly applicable to many of the fields in the Athabasca Oil Sands, which have an abundance of closely spaced well data, but a relatively poorly defined reservoir model.

AAPG Search and Discovery Article #90075©2008 AAPG Hedberg Conference, Banff, Alberta, Canada