Shale oil or gas extraction by hydraulic fracturing (fracking) could intensify pressure on water resources in some of the shale reservoirs in India that are located in water-stressed and groundwater-depleted areas, according to a global study that analysed the impact of shale oil and gas extraction on water resources.
Although it is of strategic importance for India to tap into alternative/ unconventional energy sources like shale gas to meet its rapidly growing demand for energy, exploration and production of shale oil/gas is also fraught with risks, experts said. This is especially so in already groundwater-depleted areas such as the Cambay Shale Formation.
The controversial drilling procedure (fracking) relies on pumping water laced with sand and chemicals at high pressure into shale deposits deep underground to create fractures in the rocks, unleashing the gas/oil.
Fracking remains a hotly debated issue given environmental and health concerns, so much so that the Matt Damon-starrer Promised Land, that explores the social impacts of fracking, came under intense fire from the United States’s oil and gas industry.
In the study, an international group of scientists has presented a global analysis of the impact of shale oil and gas extraction on water resources, particularly on irrigated crop production.
In stressed areas, where water is consumed at greater rates than local renewable water availability, the extraction of shale oil and gas is expected to compete with irrigated food production and other human water demands.
“Pressure on water resources in India is already high and in some regions unsustainable. Irrigation water is mainly mined from ancient aquifers in northern India,” Lorenzo Rosa, first author of the study, told Mongabay-India. “In the case of additional freshwater demand (for example from hydraulic fracturing) the situation can only be exacerbated, unless water management and water savings strategies are implemented.”
In the study, researchers focused on shale areas (or “shale plays”) that offer the most profitable opportunities for oil and natural gas extraction in the near future, while lower quality and less explored deposits, which likely hold additional shale resources, are not included in the assessment.
The analysis mapped Barren Measures (East India), Cambay Shale (Gujarat in West India), Permian-Triassic (North India) and Sattapadi/Andimadam in the Cauvery basin (South India) in the country.
The study also comes at a time when the Composite Water Management Index report from the National Institution for Transforming India-Aayog (or NITI Aayog) has said that the country is facing its “worst” water crisis in history and critical groundwater resources – which account for 40% of India’s water supply – are being depleted at unsustainable rates.
Shale gas is a natural gas (predominantly methane) and is known as an unconventional natural gas because it is tapped from “unconventional” reservoirs or deposits that are low in permeability.
Unlike conventional natural gas that is in interconnected pore spaces (much like a kitchen sponge) in permeable rocks, such as sandstone, shale gas is found deep underground in fine-grained sedimentary rocks (shale).
To free the gas for collection, the reservoirs need to be mechanically stimulated. Hydraulic fracturing (fracking) is the preferred technology for shale and it has been in use for six decades.
Fracking an unconventional shale gas or oil well requires much more water than drilling a conventional oil or gas well, from few thousands to 20 thousand cubic metres per well.
Water demand
The analysis reveals that globally about 31% to 44% of the world’s shale deposits are located in areas where water stress would either emerge or could worsen as a result of shale oil or gas extraction.
Twenty percent of shale deposits are in areas affected by groundwater depletion and 30% in irrigated land.
Deposits in currently water stressed areas include those occurring in the south-central United States, Canada, Argentina, South Africa, northern Africa, China, India and Australia.
In the assessment, the Permian-Triassic and the Cambay Formations make it to the top 15 global shale areas ranked with the highest demand for irrigation water.
“Some deposits in northern India are located in water-stressed and groundwater depleted areas where irrigation is critical for crop production,” Rosa said.
Globally, seven percent (65 cubic km per year) of total annual irrigation water is consumed on croplands overlying shale deposits.
The Cambay deposit in the Indo-Gangetic Basin is an example of agricultural basket overlaying shale deposits where Rosa and colleagues predict the “occurrence of future competition” between water for shale resource extraction and food production.
“Although global water use for shale deposit extraction is dwarfed by the local volumes used in agriculture and other activities, water consumption by the shale industry would compete with other sectors (for example], agriculture) in areas with limited water resources,” Rosa explained.
Map of water stress within shale deposits. Pixels with water stress indexes greater than one are subjected to unsustainable water consumptions (that is, water consumption for human activities exceeds the limit imposed by environmental flow requirements). Sourced from Lorenzo Rosa.
Depending on future water consumption by hydraulic fracturing, the majority (51% to 74%) of global shale areas will require less than one percent of the locally available water availability for the extraction of natural gas or oil, the researchers said.
“However, certain arid regions (17 to 33 percent of world shale areas) will require more than 50 percent of regional water resources for complete shale extraction. Shale deposits in such arid regions also include the Cambay shale (India),” Rosa added.
Although their extraction requires a small percentage of the annual local water resources available for human needs, in the long term the development of shale resources in these water-scarce areas could generate a depletion of water resources if water is consumed at rates exceeding those of replenishment by hydrological processes.
The study also highlights that an increasing recycling volume of fracturing water could make an important contribution to alleviating the depletion of local freshwater resources.
Shale exploration of strategic importance but fraught with risks
The International Energy Agency in its annual World Energy Outlook report in 2017 forecast that the United States will dominate oil and gas following its shale boom.
Developments in the US have spurred a massive interest in unconventional gas sources globally.
The International Energy Agency also emphasised that shale oil and shale gas are poised to play a fundamental role in meeting energy demand in the near future.
It is of strategic importance for India to tap into alternative/ unconventional energy sources like shale gas to meet its rapidly growing demand for energy and to reduce dependence on oil and gas import, observed Samrat Basak of the World Resources Institute, who was not involved in the study.
But, Basak said, various risks associated with its production have made it difficult to adopt large-scale exploration and production (E and P) of shale gas.
Beside its water demand, fracking produces enormous volumes of wastewater, which are either injected back into the ground or processed by wastewater treatment plants.
“The key water related risks associated with shale gas E and P are primarily extremely high requirement of water during hydraulic fracturing and contamination risk of surface water and groundwater aquifer due to issues associated with management and discharge of huge volume of produced water that typically contains fracturing fluids,” Basak said.
World Resources Institute’s Aqueduct global water risk mapping tool also draws attention to potential shale gas bearing sites of India such as Cambay, Gondwana, Krishna-Godavari, Cauvery and the Indo-Gangetic plains as areas that are currently experiencing, as well as will be experiencing, high to extreme water stress.
Shale also demands vast swathes of land, a challenge for countries like India.
Currently, there is no commercial production of shale gas in India, according to the Ministry of Petroleum and Natural Gas. The ministry maintains that the “country holds promising reserves of shale gas and oil resources.”
Sedimentary basins such as the Cambay Basin, Gondwana Basin, KG Basin, Cauvery Basin, Indo-Gangetic Basin, Assam and Assam-Arakan Basin are considered prospective from the shale oil and gas point of view.
There are no firm estimates of shale oil/gas in the country. Several agencies have provided different estimates.
In 2013 India launched a policy granting permission for shale gas and oil exploration and exploitation initially only by state-owned Oil & Natural Gas Corporation and Oil India. Private players are not allowed to explore the gas.
As per media reports, the oil ministry plans to change the definition of “petroleum” to let oil and gas exploration firms explore shale reserves in the country.
A report titled “Shale Gas in India: Prospects and Challenges” notes while many challenges to shale gas exploitation (the nature of hydraulic fluids, threat of seismic activity, contamination of water, methane emissions) can be addressed by greater transparency in the operations of this industry, these threats are not unique to shale gas exploitation.
The report is co-authored by Anil Kumar Jain, former advisor (energy), NITI Aayog and currently an additional secretary in the Ministry of Environment Forests and Climate Change.
“Even in coal bed methane exploration where a lot of water activity takes place at a shallow depth (which is more risk prone than shale gas), a decade long experience in India has not been negative,” the report said.
India needs to pay special attention to the environmental safeguard issues of the shale gas programme, he said.
Debanjan Guha Roy, a research scholar with the IITB-Monash Research Academy, believes key to tapping this energy is the proper and efficient use of hydraulic fracturing.
“This paper rightly points out the problem of fresh-water scarcity in the case of implementing conventional hydraulic fracturing to extract shale oil and gas. This is why efforts are now being made to develop alternatives that do not use water,” Guha Roy told Mongabay-India.
Some of them are supercritical carbon dioxide based fracking, cryogenic fracturing, shockwave fracturing and microwave assisted fracturing.
“Among these four methods, I believe in the next 15 to 20 years, cryo-fracking is best poised to replace conventional hydraulic fracturing in India and other countries. Unfortunately none of the national oil companies or government research institutions in India are working on it. So, when cryo-fracking technology will become commercially available to the international market, India would still need many years to adapt it to its own shale oil and gas reservoirs,” Guha Roy added.
This article first appeared on Mongabay.
