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Reservoir Characterization of Plover Lake Heavy-Oil Field*
By
Larry Lines1, Joan Embleton1, Mathew Fay1, Steve Larter1, Tony Settari1,
Bruce Palmiere2, Carl Reine2, and Douglas Schmitt3
Search and Discovery Article #40274 (2008)
Posted February 12, 2008
*Adapted from extended abstract prepared for AAPG Hedberg Conference, “Heavy Oil and Bitumen in Foreland Basins – From Processes to Products,” September 30 - October 3, 2007 – Banff, Alberta, Canada
1CHORUS, University of Calgary, Calgary, AB, Canada ( [email protected] )
2Nexen Inc., Calgary, AB, Canada
3CHORUS, University of Alberta, Edmonton, AB, Canada
Enhanced production of heavy oil from the Cretaceous sands of Eastern Alberta
and Western Saskatchewan presents many challenges – requiring a more complete
description of lithology, porosity, permeability, and changes in reservoir fluid
composition and physical properties. Our reservoir projects near Plover Lake,
Saskatchewan, seek to produce reservoir models that are consistent with all
available data, including well logs, cores, produced fluids, and seismic
data.
Thus far, we have effectively used dipole sonic data and multicomponent 3-D data
to delineate sand layers effectively. Core measurements suggest that interbedded
shale layers will impact vertical permeability and consequently oil production.
In order to map production and reservoir changes effectively, we propose to use
time-lapse (4-D)
seismic
surveys to update our reservoir models. These
seismic
measurements are coupled to laboratory measurements of Vp/Vs from core samples
and detailed oil-column profiling of fluid properties. Experience with 4-D
seismic
data at nearby Bodo field, near Provost, Alberta, has shown that
seismic
monitoring can effectively map the reservoir changes due to cold production.
Hence, we advocate a reservoir characterization strategy that involves the use
of logs, cores, and a base 3-D
seismic
survey to describe geology with repeated
multicomponent 3-D surveys being used to map reservoir changes. Our study shows
reservoir studies on models and real data from the Plover Lake area, along with
planned future research.
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This paper examines a combined geological and geophysical reservoir
analysis for a heavy oil field near Plover Lake, Saskatchewan
(Figure 1), where Nexen Inc. has applied both hot and cold
production methods. Oil sands of the Devonian-Missippian Bakken
Formation are found in NE-SW trending shelf-sand tidal ridges that
can be up to 30 m thick, 5 km wide, and 50 km long. Overlying Upper
Bakken shales are preferentially preserved between sand ridges. The
Bakken Formation is disconformably overlain by Lodgepole Formation
carbonates (Mississippian) and/or clastics of the Lower Cretaceous
Mannville Group. Since sandstones have larger S-wave velocities (and
hence lower VP/VS ratios) than shales,
VP/VS maps from multicomponent
For this study, the 3D-3C
The estimated Vp/Vs maps in this study are largely based on traveltime methods. However, a recent paper by Dumitrescu and Lines (2006) uses AVO analysis and simultaneous inversion to provide high-resolution images of the heavy oil formations. Finally, we examine cores from this area to provide a fine scale description of rock property variations in the field.
Methodology and Preliminary Results The traveltime method for creating Vp/Vs maps from multicomponent data that is both robust and straight-forward. Flat events on vertical stacks are predominantly PP reflections, but on radial stacks are mostly due to PS conversions. Hence, interval traveltimes from a radial component stack contain information about S-wave velocities and, together with the corresponding traveltimes from the vertical component stack, provide us with the necessary information to calculate Vp/Vs, the ratio of P-wave to S-wave velocities.
Figure 2 shows traveltime picks for the
vertical and radial components on The resulting Vp/Vs maps produced a very interesting and encouraging result for lithology discrimination. On the northern half of the map shown in Figure 3, we have marked enclosed features with dark lines to indicate an eroded Lodgepole Formation. In the same figure, we have also marked a boundary along the southeastern side of the map which defines the erosional edge of both the Bakken sand ridge and overlying Lodgepole Formation. Low Vp/Vs values in the middle of the map correspond to thicker Bakken and Lodgepole, while higher Vp/Vs on the southeastern side of the map correspond to a zone where the Bakken sand and Lodgepole Formation have both been eroded. In summary, when this Vp/Vs map is compared to previous interpretations based on well data and conventional (vertical component) data, the correlation of the map to other sources of lithology information is excellent. It should be mentioned that two other Vp/Vs maps based on different horizon picks are very similar to Figure 3 - suggesting that traveltime mapping of Vp/Vs is very robust and reliable. Another encouraging note is that this Vp/Vs map is very similar to those obtained by Dumitrescu and Lines (2006) using AVO analysis.
The complete reservoir characterization
involves going beyond analysis of logs and
By examining these core samples, we
realize the possibility of permeability barriers and the need for
more sophisticated reservoir models and the need for enhanced
Conclusions and Future Work
The computation of
Vp/Vs maps from a
3-D multicomponent
Acknowledgements
The authors thank the Consortium for
Heavy Oil Research by University Scientists (CHORUS) for support of
this project. We especially thank Nexen Inc., a CHORUS sponsor, for
permission to show results from their Plover Lake data. Finally, we
thank Sensor Geophysical for processing the ReferencesDumitrescu, C. and Lines, L., 2006, Vp/Vs ratio of a heavy oil field from Canada, paper submitted to the 2006 CSPG-CSEG convention. Lines, L., Zou, Y., Zhang, A., Hall, K., Embleton, J., Palmiere, B., Reine, C., Bessette, P., Cary, P. and Secord, D., 2005, Vp/Vs characterization of a heavy-oil reservoir; The Leading Edge, 1134-1136.
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