Journal of Environmental Biology

Characterization of light gaseous hydrocarbons of the

surface soils of Krishna-Godavari basin, India

Author Details

M. Lakshmi

(Corresponding author)

Microbiology Laboratory, National Geophysical Research Institute (CSIR), Uppal Road,

Hyderabad - 500 007, India

e-mail: lakshmi.kirla1220@gmail.com

M.A. Rasheed

Microbiology Laboratory, National Geophysical Research Institute (CSIR), Uppal Road,

Hyderabad - 500 007, India

T. Madhavi

Microbiology Laboratory, National Geophysical Research Institute (CSIR), Uppal Road,

Hyderabad - 500 007, India

M. S. Kalpana

Microbiology Laboratory, National Geophysical Research Institute (CSIR), Uppal Road,

Hyderabad - 500 007, India

D.J. Patil

Microbiology Laboratory, National Geophysical Research Institute (CSIR), Uppal Road,

Hyderabad - 500 007, India

A.M. Dayal

Microbiology Laboratory, National Geophysical Research Institute (CSIR), Uppal Road,

Hyderabad - 500 007, India

Publication Data

Paper received:

25 September 2010

Revised received:

13 January 2011

Accepted:

05 February 2011

Abstract

Several techniques are used for the exploration of hydrocarbons, of which; the geochemical techniques involving the microbiological technique use the principle of detecting the light hydrocarbon seepage activities for indication of sub-surface petroleum accumulations. A survey was carried out to characterize the light gaseous hydrocarbons seeping in oil and gas fields of Krishna-Godavari basin of Andhra Pradesh. A set of 50 sub-soil samples were collected at depths of about 3 m for geochemical analyses and 1m for microbiological analysis. The microbial prospecting studies showed the presence of high bacterial population for methane 2.5 x 10² to 6.0 x 10⁶ cfu g^-1, propane 1x10² to 8.0 x 10⁶ cfu g^-1 in soil samples. The adsorbed soil gas analysis showed the presence of moderate to low concentrations of methane (26? to 139 ppb), ethane (0 to 17 ppb), propane (0 to 8 ppb),? butane (0 to 5 ppb) and pentane (0 to 2 ppb) in the soil samples of the study area. Carbon isotope analysis for methane (?¹³C₁) ranging from -36.6 to -22.7?? Pee Dee Belemnite (PDB) suggests these gases are of thermogenic origin. Geo-microbial prospecting method coupled with adsorbed soil gas and carbon isotope ratio analysis have thus shown good correlation with existing oil/ gas fields of? Krishna-Godavari basin.

Key words

Light gaseous hydrocarbons, Adsorbed soil gas, Carbon isotope analysis, Hydrocarbon oxidizing bacteria, Thermogenic

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