AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Digital Image Analysis of Conglomeratic Outcrops: A Novel Quantitative Approach to Detailing and Predicting the Temporal and Spatial Evolution of Slope Channel Systems
(1) Geology and Petroleum Geology, University of Aberdeen, Aberdeen, United Kingdom.
The building blocks of a sedimentary system are essential inputs into studies of reservoir character and comparisons with other sedimentary systems. Yet, our current knowledge of the building blocks of deep water slope channel deposits is still largely speculative. A quantitative approach has been utilised in order to analyse a host of lithological data and objectively identify these sedimentary components. The laterally-extensive and gently-dipping continental slope deposits of the San Fernando Channel System, Baja California, provide the required control on sub-seismic-scale temporal and lateral variations of lithofacies and 3D architecture. High resolution photo-panoramas (better than 2cm accuracy) of this dominantly conglomeratic succession were collected from various key parts of the outcrop.
Modern image processing techniques have largely been focused around biomedical research, from which freely-available algorithms offer a range of particle detection methods which can be combined to compute reproducible clast dimensions. Image analysis of segments extracted from the photo-panoramas generates key parameters for comparison of texture and fabric of conglomerates, such as clast to matrix ratio, major axis length and orientation. Statistical analysis of these data enables the erection of an objective lithofacies scheme, the grouping of lithofacies into objectively-defined assemblages, and the establishment of models for the lateral and stratigraphic arrangement of these assemblages. Preliminary analyses indicate differences in the lithofacies assemblages between the early and later parts of a channel complex set (sensu Sprague, 2002), and between marginal and axial parts of the system. These can be related to spatial differences and temporal changes in the nature of the turbidity currents flowing through the channel system. This quantitative approach to sedimentary analysis can be applied to other coarse grained deposits, particularly where accessibility prohibits efficient logging. Quantitative results will be integrated with more conventional interpretations of 3D architecture from outcrop photo-panoramas in a digital outcrop model, the ultimate input for a robust reservoir model.