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Identification and Modelling of Natural Hydrocarbon Micro-Seepage Induced Alterations and Anomalies on Soil, Sediments and Vegetation in Ugwueme, with Remotely Sensed Data
 
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Department of Geoinformatics and Surveying, University of Nigeria, Nsukka - Onitsha Rd, Nsukka, Nigeria
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Department of Surveying and Geoinformatics, Federal University of Technology, 1526, PMB,Owerri, Ihiagwa, Nigeria
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Department of Surveying and Geoinformatics, Nnamdi Azikiwe University, Along Enugu-Onitsha Expressway, Ifite Road, 420110, Awka, Nigeria
CORRESPONDING AUTHOR
Mfoniso Asuquo Enoh   

Department of Geoinformatics and Surveying, University of Nigeria, Nsukka - Onitsha Rd, Nsukka, Nigeria
 
 
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ABSTRACT
The Earth’s underlying hydrocarbon bearing reservoirs often leak. These reservoirs leak, because they are poorly sealed and at high pressure, oil and gas escape vertically or in a near vertical direction to the Earth’s surface as seepage. Micro–seepages found on the Earth’s surface create oxidation–reduction reactions, resulting in anomalies such as red bed bleaching, ferrous iron enrichment, clay and carbonate concentration as well as geo-botanical anomalies in overlying soils, sediments and vegetation. Remote Sensing techniques have been successfully adopted to study surface alterations and anomalies of minerals. In this study, the Landsat 7 ETM+ and ASTER data were adopted to delineate the areas of hydrocarbon micro–seepage induced anomalies in Ugwueme. Spectral enhancements such as the Principal Component Analysis (PCA), Band Ratio (BR) and the False Color Composite (FCC) were used to depict areas of alterations. Utilizing the Landsat 7 ETM+ data, and for PCA analysis, the image highlighted that the principal components (PCs) of 1357–PC3, 1345–PC3 and 2357–PC3 indicate good spectral enhancement to depict alterations zones. The ASTER band ratios of 2/1, 4/3, (7 + 5)/6 and 1/2 also showed alterations zones in the study area. A vegetation anomaly was detected with the Landsat ETM+ data through NDVI to delineate the areas of anomalous vegetation in the vegetation cover. The study highlighted that PCA, BR and FCC are excellent spectral enhancement techniques for delineating the areas associated with hydrocarbon micro–seepage.