Laser Scanning and Hyperspectral Imaging of Eagle Ford Formation, West Texas

Abstract

Vertical cliff faces of three outcrops of Eagle Ford Formation in west Texas are scanned using Hyperspectral imaging in visible-near-infrared and shortwave-infrared wavelengths and terrestrial laser scanner. Hyperspectral sensors record electromagnetic radiation reflecting off the outcrop in numerous contiguous bands, which are then used to generate a spectral signature for each pixel sampled. Comparison between the spectral signatures recorded from the outcrop and those of reference materials, enabled accurate mapping of composition and mineralogy of Eagle Ford Formation. Laser scanning data allowed mapping of geologically important surfaces, such as sequence boundaries and structural elements. Ground-based hyperspectral data were acquired by University of Houston's Specim Dual Camera Hyperspectral Imaging System. Several rock samples were also analyzed in the laboratory, where spectral reflectance of rocks was measured with 2.8–10 nm spectral resolutions. These samples were also scanned by Hyperspectral cameras at millimeter resolution. Two algorithms were implemented for the classification of hyperspectral data: Spectral Angle Mapper, and Spectral Feature Fitting. SAM is used to identify pixels from the image that have spectral signatures similar to already defined endmembers. This method treats both questioned and known spectra as vectors and calculates the spectral angle between them. The result of the SAM classification is an image showing the best match at each pixel. Spectral Feature Fitting is an absorption-feature based method for matching image spectra to reference endmembers, which are selected from either the image or a spectral library. In this technique user specifies a range of wavelengths within which a unique absorption feature exists for chosen targets. In Eagle Ford samples, calcite, dolomite, kaolinte and several other clay minerals provided main absorption features. Using these techniques rhythmic layers of marlstone, limestone and bentonite as well other lithological variations in Eagle Ford Formation were quantified. Laser scanning data were fused with classified hyperspectral data to produce three-dimensional photorealistic outcrop models with detailed compositional and mineralogical maps. The use of laser scanning and Hyperspectral data fusion allowed quantitative mapping of important reservoir characters, compositional variations and geotechnical properties of Eagle Ford Formation.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015