Detection of mineral alteration induced by hydrocarbon microseepages by using remotely sensed data in the Fateh Jang area of the Northern Potwar region of Pakistan

Abstract

Mineral alteration can be induced by the hydrocarbon seepages at the earth surface that can be detected by the use of earth observation data. The long-term seepage of hydrocarbons in the subsurface can induce different types of chemical and mineralogical alterations in the rosk and soil. Mapping of these mineral alterion is important to explore hydrocarbon. In this study, satellite images were used to identify the surface mineral alterations due to hydrocarbon microseepages in the Fateh Jang area of the Northern Potwar region, Islamabad, Pakistan. Landsat TM band ratios of 7/5, 3/1, and 5/4 are used to detect ferric minerals, clay minerals, and ferrous iron minerals bearing sedimentary rocks, respectively, which are applied to distinguish the altered and unaltered rocks. Such rocks have specific spectral responses in various bands of the electromagnetic spectrum and thus give rise to a number of anomalies indicating the presence of hydrocarbons. This study uses enhancement techniques of principal component analysis (PCA), band ratio, false color composite (FCC), and thermal anomaly composition for surface expressions caused by microseeps. It is revealed that spectral reflectance signify that the ferrous iron and red bed bleaching have reflection band and absorption band in TM bands 1, 3, and 4, respectively. Clay minerals and kaolinite have enormous reflection in band 5 and absorption capacity in TM band 7. These results can be used as a model to identify the alteration induced by hydrocarbon seepages. The study area is categorized into northern, eastern, southern, and western zones on the basis mineral alteration. The northern zone is characterized by strong anomalies and is relatively rich in clay alteration and ferrous as compared to other zones. Two types of hydrocarbon microseepages were observed in the Fateh Jang area which includes active seepages (gas microseepages and oil seepage) and passive seepage (bleaching effects).