Evidence of Hydrocarbon Seepage Using Multispectral Satellite Imagery, Kurdistan, Iraq
The petroleum system in northern Iraq has reached a maximum expulsion phase, characterized by tectonic uplift, beveled fold and thrust structures, and active surface oil seeps. While conducting photogeologic interpretation in the region, it was observed that well exposed dip slopes exhibit spectral changes along strike, especially notable along producing antiforms near Kirkuk, Irbil, and Mosul. The majority of these altered outcrops are carbonate composition, as modeled from ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) shortwave-infrared (SWIR) multispectral bands. The spatial pattern of alteration may not reflect diagenesis but appears closely coincident with structure, manifested along thrusted fold fronts and eroded symmetric folds. In addition, many altered exposures correspond with known oil seeps, sour (sulfurous) water locations, and bitumenous sites identified throughout the region. Predicting and mapping rock and soil alteration from satellite imagery is an accepted practice for mineral exploration, where heat and chemical changes from intrusions alter country rocks in phases that can be spectrally characterized and associated with ore. During the mid-80s, several oil and gas test cases were investigated, documenting geochemical changes in rocks associated with changing pH and hydrocarbon microseepage. It is proposed that hydrocarbon migration has altered surface rocks in Kurdistan as evidenced by digital image analysis of Landsat and ASTER satellite imagery and spectroscopy of hand samples. In addition, satellite imagery proved successful for enhancing oil films on the Tigris River reservoir and in identifying sulfurous drainage. Image analysis is shown to be a key exploration tool for this geologically complex and rugged terrain.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009