Comparative
Analysis
of the Geologic Setting,
Sequence
Stratigraphy and Reservoir
Architecture of the Canadian
Suter, John R.,
ConocoPhillips,
The Athabasca
Tar Sands of Canada and the Faja Petrolifera del Orinoco, or Orinoco Heavy Oil
Belt, of well
production from the Oficina Formation (Petrozuata,
Hamaca). Despite some obvious differences, the McMurray and Oficina show many
similarities in their geologic setting,
sequence
stratigraphy, and reservoir
architecture. Both of these huge accumulations lie on the peripheral bulges of
foreland basins, with their principal sediment sources in granitic shield
terrains. Neither has been buried to substantially greater depths than present
day; consequently their unconsolidated, dominantly quartzose reservoir sands
have extremely good permeabilities and porosities. The hydrocarbons of the
respective deposits were generated from prolific shallow marine source rocks,
and emplaced as conventional oils into broad, low-amplitude traps with
significant or dominant stratigraphic components. Subsequent biodegradation
and/or water washing produced the present-day bitumen and heavy oils.
Sedimentologic, ichnologic, and biostratigraphic analyses of cores and
outcrops, coupled with interpretations of extensive
well
log
and 3D seismic
datasets, reveal that both formations comprise non-marine to marginal marine
deposits, with principal reservoir facies mainly channelized fluvial,
tidal-fluvial, and estuarine deposits within incised valley complexes.
Understanding and predicting reservoir heterogeneity and compartmentalization
within this overall framework is crucial to the ongoing and future success of
projects within both the Venezuelan Heavy Oil Belt and the Athabasca Tar Sands.