Deepwater Slope Channel Stacking Architecture in Outcrop: High Resolution Geologic Data Capture Methods and Modeling, Cretaceous Tres Pasos Formation, Southern Chile

High-resolution data collection methods are used to map and characterize coarse-grained lower slope deposits of the Cretaceous Tres Pasos Formation that crop-out in the Magallanes Basin, Chilean Patagonia. A robust approach has been developed to convey outcrop data to geomodel through the utilization of real time differential-GPS, which provides an accurate (~10 cm resolution) and efficient data collection method for channel architectural reconstruction through the surveying of key channel bounding surfaces. A sedimentological evaluation characterizes internal channel fill architecture along the outcrop belt and provides detailed controls for 3D model construction. >3000 m of detailed stratigraphic section and hundreds of paleocurrent measurements are used to establish channel flow direction and delineate channel margins, which are used to project channel bodies beyond the outcrop. The method utilized in this study provides an efficient means to improve understanding of slope channel stratigraphy, channel architecture, and stacking patterns, ultimately providing a realistic analogue for hydrocarbon reservoir characterization.

The Tres Pasos Formation consists of slope to basin-floor deposits associated with a high-relief slope clinoform system dominated by mudstone- and siltstone deposits; the focus of this study are sandstone-rich lower slope channel deposits. The outcrop belt of interest is 6 km in length, 1.5 km wide and ~350 m high, with architectural mapping encompassing multiple hierarchical scales (i.e., channel elements, channel complexes and channel complex sets). Individual channel elements range from 11-15 m thick in the lower portion of the stratigraphic column and are up to 26 m thick upwards; sedimentary body aspect ratios decrease upwards as relatively thin tabular, laterally extensive sandstone units >500 m wide transition to incised channels 300-400 m wide, in conjunction with overall slope progradation. Channel element stacking trajectories are well-organized, with laterally constrained, aggradational stacked complexes common. Systematic lateral offset trajectories are also important in the outcrop belt. The quantification of channel architecture, including the lateral extent and connectivity of channel elements and complexes, provides reservoir-scale insight into analogous seismically imaged fills of major channel-levee systems, slope valleys, and other confined conduits from continental margins around the world.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California