Classifying Digital Imagery of Modern Isolated Carbonate Platforms for Facies Conditioning of Reservoir Models: Alacran Reef, Gulf of Mexico
Jason J. Lodge, David
Leverington, and Peter Holterhoff
Department of Geosciences, Texas Tech University
Alacran Reef is a modern isolated carbonate platform located 75 miles north of the Yucatan Peninsula in the southernmost region of the Gulf of Mexico. The reef sits on the edge of the Campeche shelf and is a relatively large platform (~25 by 13 kilometers). This platform has been extensively studied and has been well characterized with regard to sediment distribution patterns, which allows for robust calibration and classification of facies using satellite imagery. Using a modern carbonate environment as an analog for the subsurface is common practice in the petroleum industry today. However, qualitative analysis of the scales of facies heterogeneity and spatial dimensions of these environments leaves much room for interpretation.
At Alacran Reef, each facies generally reflects incident radiation in a characteristic manner, and the diverse reflective properties of reef materials allow for the classification and statistical analysis of the platform. Alacran Reef was characterized in this study using a supervised classification method involving selection of training sites on the basis of previously published sample data. The utilized satellite image was generated by the Landsat Thematic Mapper sensor (30 meter pixel size, 7 separate spectral bands). Image bands of special interest in this study included those generated in the blue, green, red, and near-infrared regions of the electromagnetic spectrum. After classification, statistics were generated to produce facies frequency and uncertainty maps using bins of different scale.
The potential impact of image resolution on aspects of image analysis and the characterization of facies is of considerable interest in this study. Future work will involve empirical evaluation of resolution effects at Alacran Reef through additional analysis of high-resolution imagery generated by the Ikonos sensor (1 meter panchromatic and 4 meter multispectral pixels). Results generated using the Thematic Mapper and Ikonos images will be compared to determine if higher resolution imagery will yield a better statistical representation of the platform.
Statistics generated for four modern isolated carbonate platforms in Belize will follow the analysis of Alacran Reef, and will allow for comparisons of platforms with varying shapes and sizes.
AAPG Search and Discovery Article #90089©2009 AAPG Southwest Section Meeting, Midland, Texas, April 26-29, 2009