Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
An Architecture-Based Classification for Marginal Marine Systems: Examples from the Ancient and Modern
(1) Australian School of Petroleum, Adelaide, SA, Australia.
Stratigraphic architecture at a sub-parasequence scale controls fluid flow in many reservoirs. However, this scale falls below the resolution of current sequence stratigraphic techniques and as such there is no rigorous methodology or classification to describe these deposits. New concepts have been developed for the classification of process dominance and stratigraphic architecture in both modern and ancient marginal marine systems. This methodology facilitates collation and cross-applicability of geometrical data from modern to ancient systems, and vice-versa. The new architectural classification system is hierarchical in nature and works on five spatial levels. The levels correspond to different scales of observation and are required to describe properly the stratigraphic variability in the subsurface. The first level in the classification (Level I) consists of ‘Elements (E)’ and ‘Element Sets (ES)’, which form the basic building blocks of stratigraphy. Level II is characterised by ‘Element Complexes (EC)’ and ‘Element Complex Sets (ECS)’. At Level III, Element Complexes are grouped into ‘Assemblages’ (Element Complex Assemblages; ECA). At the next level (Level IV), the ECAs can then form transgressive or regressive ‘Assemblage Sets’ (TECAS and RECAS respectively). The final level is Level V which is the equivalent of the existing T-R sequence.
Detailed field studies were conducted to calibrate the new concepts. The field areas were selected for their mixed-influence character and their excellent exposure. Two of these studies will be described; a modern system - the Mitchell River Delta, Gulf of Carpentaria, Australia, and an ancient system from Drumheller, Alberta, Canada. The tropical savannah setting of the Mitchell Delta allows remote sensing and mapping to an Element level of the architectural hierarchy. Ground-truthing was possible by augering and trenching of the system. Four cored and wireline logged wells close to the Drumheller outcrops also permitted the extrapolation of the new techniques from an outcrop area into the subsurface. This allowed testing of the architectural classification on an outcrop calibrated subsurface core and wireline dataset.
The application of these new classification concepts to the modern and ancient field areas has allowed refinement and calibration of the theoretical concepts and identification of avenues for further investigation.