Krishna-Godavari A Sinking Basin

The extraction of oil and natural gas in the Krishna-Godavari basin may precipitate an environmental disaster in the region, says a scientific study. The area, which is barely five feet above sea level, has been found to be sinking. This could lead to flooding of the region by the two rivers.

The study by the geology department, Andhra University, Visakhapatnam, has found slow continuous creeping along claystones in some oil fields where the surface has sunk by a few millimetres. Continued exploitation of oil and gas may be contribute to the land surface sinking further, says the study by G Krishna Rao .

 

Quoted in the latest issue of the Indian Academy of Sciences Journal, Raos study says oil and gas occurs at a depth range of 3,000 to 8,000 feet. Probes into the recent blowouts in the East Godavari district have revealed that reservoir pressure is very high, with the free flow conditions putting the entire area at risk.

The study said that in the other areas of the world, like Venezuela and Texas, where over-exploitation of oil and gas has been reported, the land has sunk by as much as five to 25 feet, causing an environmental disaster.

The study says that the situation in the Krishna-Godavari basin has been showing early signs of sinking and that the Oil and Natural Gas Commission should take immediate preventive action. One solution was that water injections be used to make up for the vacuum caused by oil extraction so that the dynamics of the earths crust was not disturbed.

Rao says that besides an oil and gas zone, the basin is an important rice growing region and is thickly populated. Repeated oil field fires and land sinking can adversely affect the economy of the coastal region of Andhra Pradesh.

The Krishna-Godavari basin is located on the east coast bordering Andhra Pradesh. The total area of the basin is around 59,000 km 39,000 km offshore and 20,000 km onland. So far, 296 wells have been drilled both onland and offshore in the basin and more than 130 prospects probed. These prospects have yielded 22 gas and 12 oil fields including the Ravva oilfield, being developed by a consortium of Command Petroleum, Marubeni and Videocon.

According to V K Rao of the Directorate General of Hydrocarbons, who has done extensive work in the basin and has developed a novel hydrocarbon fairway system, the prospects occur at different stratigraphic levels and the reservoirs range in all ages. The prognosis shows that there could occur 575 million tonnes of hydrocarbons onland and 555 million tonnes offshore. Of the total estimated 1,130 million tonnes of hydrocarbons, only 15 per cent has so far been established.