Deep saline aquifers for sequestration of carbon dioxide
|Location||International Geological Congress,oslo 2008|
|Holding Date||04 October 2008|
In India, carbon dioxide emissions have increased from 560 million tones (Mt) in 1990 to 668 Mt in 1994 to 1069 Mt in 2000 with thermal power plants contributing to about 85% of the total emissions. The reduction in the emission of greenhouse gases and their capture and storage in geological formations requires immediate attention (UN Climate Change Conference, 2007) to mitigate the impacts of climate change. Of all the CO2 storage options like depleted oil and gas fields, unminable coal seams or offshore areas, saline aquifers etc, the option of storages in deep saline aquifers having a considerable storage potential is proving to be cost effective option. In India, studies are being conducted to identify the possible geological storages which are preferably in proximity of the power plants, evidently reducing the transportation cost. The studies conducted so far of the saline aquifers of India indicates that they are mostly distributed in the arid regions, canal command areas and the geological formations of marine origin.
However, the exploration in Indo-Gangetic alluvial plains establish the presence of shallow and deep saline aquifers upto a depth of 1000 m and more in a stretch of 700 kms from Meerut to Ghazipur in Uttar Pradesh.
The earlier studies revealed that the deep saline aquifers occur below 700 m with some occasional lenticular lenses of saline aquifer zones. In order to comprehend the lateral and vertical presence of aquifer zones, a detailed study was conducted covering the western extent of the Ganga basin for a stretch of about 200 kms probing the depth upto 1000 m. The interpreted results indicate the presence of brackish water (EC > 2000 ppm) at depths of 700 - 920 m bgl within the upper Bhander sandstone of Vindhyan super group. The subsurface lithology and the deep aquifer systems fulfill the requisites of a storage site as it occurs at depths more than 800 m bgl and has a thick impervious layer in the form of compact bedrock.
Moreover, this pervious fractured zone is continuous and adequately separated from fresh water zones with thick intervening clay layers.
It is estimated that the pervious zone has a storage capacity of 0.28 Million m3 (approx) with assumptions on specific yield value. It is opined that the deep saline aquifers need to be further probed to study their extension beyond the study area.