Relevance of Pentane- and Hexane-Utilizing Bacterial Indicators for Finding Hydrocarbon Microseepage: A Study from Jamna
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Relevance of Pentane- and Hexane-Utilizing Bacterial Indicators for Finding Hydrocarbon Microseepage: A Study from Jamnagar Sub-basin, Saurashtra, Gujarat, India Mohammed Abdul Rasheed,1,3,4 M. Lakshmi,1 P. L. S. Rao,1 D. J. Patil,1 A. M. Dayal,1 and V. Sudarshan2 Received 10 October 2011; accepted 27 September 2012 Published online: 30 October 2012
Mesozoic sediments are source rocks for nearly half the worldÕs hydrocarbon reserves. Hence, there is great interest in the oil industry to know the trap and sub-trappean sediment thickness and their extent in the trap covered regions of Jamnagar study area. The microbial prospecting method is applied in the Jamnagar sub-basin, Gujarat for evaluating the prospects for hydrocarbon exploration by investigating the anomalous abundance of n-pentane- and nhexane-oxidizing bacteria of this area. A total of 150 near-surface soil samples were collected in Jamnagar sub-basin, Gujarat for the evaluation of hydrocarbon resource potential of the basin. In this study, bacterial counts for n-pentane-utilizing bacteria range between 1.099102 and 9.899105 cfu/g and n-hexane-utilizing bacteria range between 1.099102 and 9.299105 cfu/g. The adsorbed hydrocarbon gases consisting of ethane plus hydrocarbons (RC2+) of 1–977 ppb and n-pentane (nC5) of 1–23 ppb. The integrated geomicrobial and adsorbed soil gas studies showed the anomalous hydrocarbon zones nearby Khandera, Haripur, and Laloi areas which could probably aid to assess the true potential of the basin. Integrated geophysical studies have shown that Jamnagar sub-basin of Saurashtra has significant sediment thickness below the Deccan Traps and can be considered for future hydrocarbon exploration. KEY WORDS: Hydrocarbon-utilizing bacteria, microbial prospecting, microseepage, petroleum exploration.
by the Directorate General of Hydrocarbons (DGH), India. However, the major part of the Jamnagar sub-basin is covered by Deccan Traps, hindering the exploration of Mesozoic hydrocarbon targets. Detection and mapping of Mesozoic sediments below the Deccan Trap has been a long-standing complex geophysical problem facing the oil industry. The vast sheet of volcanic cover which overlies the Mesozoic sediments acts as a geophysical shield and inhibits the effective use of conventional seismic techniques. With the increase in demand for petroleum products and diminishing indigenous production, it has become necessary to look for probable potential zones. Mesozoic sediments throughout the world are known for hydrocarbons and are potential source rocks for more than 50% of the worldÕs
INTRODUCTION The Jamnagar sub-basin of Saurashtra, Gujarat is considered geologically prospective for hydrocarbons 1
Microbiology Laboratory, Petroleum Geochemistry Group, National Geophysical Research Institute, Council of Scientific and Industrial Research (CSIR), Uppal Road, Hyderabad 500 007 Andhra Pradesh, India. 2 Department of Applied Geochemistry, Osmania University, Hyderabad, India. 3 C/O D. J. Patil, Microbiology Laboratory, National Geophysical Resea
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