title: Characterization of light gaseous hydrocarbons of the surface soils of Krishna-Godavari basin, India.
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. Asurvey was carried out to characterize the light gaseous hydrocarbons seeping in oil and gas fields of Krishna-Godavari basin ofAndhra Pradesh. Aset 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 10(2) to 6.0 x 10(6) cfu g(-1), propane 1x10(2) to 8.0 x 10(6) 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 per hundred 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.
authors.affiliation: Microbiology Laboratory, National Geophysical Research Institute (CSIR), Uppal Road, Hyderabad - 500 007, India. lakshmi.kirla1220@gmail.com
authors.forename: M
authors.initials: M
authors.lastname: Lakshmi
authors.forename: M A
authors.initials: MA
authors.lastname: Rasheed
authors.forename: T
authors.initials: T
authors.lastname: Madhavi
authors.forename: M S
authors.initials: MS
authors.lastname: Kalpana
authors.forename: D J
authors.initials: DJ
authors.lastname: Patil
authors.forename: A M
authors.initials: AM
authors.lastname: Dayal
mesh_terms: D002247:Carbon Isotopes; D004784:Environmental Monitoring; D005740:Gases / Q000737:chemistry*; D055593:Geological Phenomena; D006838:Hydrocarbons / Q000737:chemistry*; D007194:India; D010578:Petroleum; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D005740:Gases; D006838:Hydrocarbons; D010578:Petroleum; D012989:Soil Pollutants