Petrol and Natural Gas in Kadapa: National Geophysical Research Institute finds hydrocarbon reserves in Kadapa (Cuddapah) basin
Syed Akbar Hyderabad: Kadapa, notorious for bombs and bloodshed, will soon become the newestdestination for exploration of oil and natural gas in the country with the NationalGeophysical Research Institute discovering hydrocarbons in the Kadapa (Cuddapah) basin. Joint studies by the city-based NGRI and the Directorate-General of Hydrocarbons, Noida,have established the hydrocarbon resource potential of the Kadapa basin. Kadapa basin isan ancient geological structure with rich resources of oil and natural gas, and it couldwell become the next destination for hydrocarbon exploration in the State afterKrishna-Godavari basin. Presence of natural gas and oil is detected by several methods. The NGRI employed"adsorbed soil gas" methods as well as the presence of bacteria to find out hiddenhydrocarbon resources. Light hydrocarbons like methane, propane, ethane and butane comeout of the soil either in large or minute proportions. If the leakage is in large quantities it can be identified easily. But in most of thecases the gases coming out are in small quantities which cannot be identified. However,in such cases certain bacterial groups live there eating these gases. The presence ofthese bacteria in large groups signifies that hydrocarbons are hidden underneath theearth. The NGRI studied the soil samples and took up adsorbed soil gas and microbialstudies in Kadapa basin to establish the presence of oil and natural gas. "The adsorbed soil gas studies and the inferences from geological, geophysical and othergeochemical data, suggest that the demarcated areas around Nandyal and Koilakuntla may bepotential for future hydrocarbon research and exploration. The Kadapa basin hashydrocarbon resource potential and efforts are on to conduct close sampling in theanomalous hydrocarbon zones," said Dr AM Dayal, head of the department of Stable Isotopeand Surface Geochemical Prospecting for Hydrocarbon, NGRI. Kadapa is an epicratonic Proterozoic basin situated over a length of 440 km and a widthranging from 150 km to 200 km. The Kadapa basin covers an area of 44,500 sq km extendinginto the districts of Kadapa, Kurnool, Anantapur, Prakasam and even Raichur in Karnataka. The NGRI-DGHC teams collected 304 soil samples with spacing of four to five km alongcertain roads in the basin. Analysis showed 87 per cent of soil samples fall in the oilzone and remaining in the gas-condensate zone, Dr Dayal said. Sample points with higher concentration of methane (more than 35 ppb) are clusterednorth-northwest and southwest of Nandyal and south-southwest of Koilakuntla with a fewscattered anomalies all over the study area. The hydrocarbon anomalies obtained in thesoil samples near Nandyal correlate with the good sediment thickness in the range of 6000to 9000 metres for the Nandyal shale, which is considered as an ideal cap rock andpotential target for petroleum exploration. Frequently occurring carbonaceous shales with strong microbiotic content at differentstratigraphic levels like Vempalle, Tadipatri, Cumbum and Pullempet formations alsoindicate petroleum source rock potential of the basin, Dr Dayal said. The structures likesynclines, anticlines, fault closures in the Kadapa basin play an important role inhydrocarbon generation and entrapment.