Bangalore: As the hunt for hydrocarbons intensifies with soaring demand, and prices, of oil and gas, even incremental technology for exploration is becoming important. Using one such technology, a low-cost one, a group of researchers at the National Geophysical Research Institute (NGRI) in Hyderabad has discovered for the first time hydrocarbon reserves in Andhra Pradesh’s Cuddapah district.
Applying a so-called geo-microbial method, along with existing biochemical techniques, A.M. Dayal and colleagues have reported in the Indian Academy of Sciences journal, Current Science, that the Cuddapah basin has high reserves of hydrocarbons and is suitable for conventional petroleum exploration. “Whether it’s oil, or gas can be said only after a month when we complete our analysis, but we are sure there are significant reserves in Vengannapalli village in Cuddapah basin,” says Dayal, a senior NGRI scientist.
This is the first time, Dayal claims, that results from geo-microbial prospecting in India are being reported, and that too from a basin dating back to the Proterozoic age (geological age, 2,500-570 million years ago), which is unexplored in India. The most explored basins, in India and the world over, are from the Mesozoic age (1,500-600 million years ago). About 54% of oil and 44% of gas in the world are derived from sediments from this age, according to an NGRI paper.
“Since there’s been no exploration activity in that basin, we believe it’s an important finding,” says S.V. Raju, senior adviser at the government’s directorate general of hydrocarbons, New Delhi, which entrusts NGRI most of its prospecting studies, based on which it auctions the blocks for exploration.
There’s still work to be done, says Raju, as only drilling can prove whether the basin is commercially important, or not, but he agrees that the method and the new data open opportunities for exploration in areas that have been ignored due to poor logistics. “This can now allow us to explore frontier basins in category IV (potentially prospective basins),” adds Raju.
Discovering New Sources (Graphic)
Geo-microbial prospecting is an exploration method that detects hydrocarbon-oxidizing bacteria in the sediments. That is, populations of bacteria that consume methane, ethane, propane and butane are identified and tested for the gaseous concentrations. But even though it gives direct evidence of hydrocarbons, it is not a stand-alone technique. So, NGRI researchers used it with other geo-chemical tools, including adsorbed soil gas and carbon isotope analysis.
Researchers say the tool has given encouraging results even in the Ganges basin, where the hydrocarbon deposit is very deep owing to thick sediments in the region, which impedes the popular geo-physical method of explorations. “Using microbial method, we have solid indications of hydrocarbon reserves near Purnia in Bihar and around Meerut in Uttar Pradesh,” says Dayal.
Even though the microbial method, which forms a part of geo-chemical tools, has been known for some time, geo-physical methods are popular with the industry as they are non-invasive and don’t require sophisticated biology labs. There are only two geo-chemical laboratories in the country today, at NGRI, and Oil and Natural Gas Corp. Ltd (ONGC) says Dayal.
“This method gives a direct test of hydrocarbon, but it’s not quantitative,” says a senior official at ONGC’s Institute of Biotechnology and Geotectonics Studies at Jorhat in Assam, justifying its lack of popularity with the industry. The official doesn’t want to be named as he’s not authorized to speak to the media.
But Dayal believes with this published data, industry will be encouraged to invest in this method, even as he’s begun to conduct research for companies such as ONGC, GAIL (India) Ltd, Gujarat State Petroleum Corp. Ltd and Cairn India Ltd. “Since this is a low-cost method, we can survey a larger area in a given budget.”
Bolstered by the new findings, NGRI now plans to take up prospecting in other Proterozoic basins—Vindhyan in central India, and Bhima and Kaladgi in Karnataka. “When the domestic need is so compelling, even small reserves, particularly of gas, can serve the society,” says Dayal.