Application of Physical Tank Experiments to the Interpretation of Deep Water Outcrop, ‘Fan 3’, Tanqua Karoo, South Africa
David C. Hoyal1, Chris Edwards1, Anthony Sprague1, Darren Box1, Benjamin Sheets2, Roger Bloch1, Kirt Campion1, and Shauna K. Oppert1
1ExxonMobil Upstream Research, Houston, TX
2ExxonMobil Production, Houston, TX
Constraining the physical processes that deposit and shape deep-water strata provides a basis for linking stratigraphy to models of lithofacies distribution and enables disparate architectural observations at different scales to be placed within a common predictive framework. A physical model of deep water fan evolution derived from tank experiments is compared with outcrop observations from the Karoo Basin, South Africa (‘Fan 3’). Specific outcrop observations that can be explained within the context of the experimental models include: 1. Large-scale (complex to complex set): ‘Fan 3’, a thick progradational succession, is made up of smaller-scale progradational and retrogradational elements (storey sets). 2. Meso-scale (storey to storey set): Variations in channel relief and fill character with position along the depositional profile are consistent with the experimental model. 3. Small-scale (bed to bed set): Vertical successions of bedforms might indicate a transition from super-critical to critical flow with the growth of depositional topography and variations in flow confinement. Experiments show that deep water fan stratigraphy is strongly controlled by avulsion cycles associated with the extending distributive channel system, including stages of channel initiation, channel extension, and reaction to the growing downstream topography. Mapping channels (storey - storey set scale) is difficult because of their sparse nature, limited lateral extent and variable orientation in relation to the outcrop. These problems were mitigated by using process models to link several lines of evidence from the large and small scales to support the interpretation of the channel behavior. This approach enables the refinement of submarine fan depositional models and provides a link between the observed hierarchical arrangement of strata and depositional map patterns.
AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery