In News
- Recently, Cairn Oil & Gas has announced that it is partnering US-based Halliburton to start shale exploration in the Lower Barmer Hill formation, Western Rajasthan.
About
- The company is looking to increase the recoverable reserves at its offshore assets by 10 times via enhanced use of technology, in partnership with Halliburton.
Image Courtesy: Geology
Shale Oil
- Definition:
- Shale gas is natural gas, one of several forms of unconventional gas (also known as methane or CH4).
- It is trapped within shale formations with low permeability, which is fine-grained sedimentary rock which acts as its source as well as reservoir.
- It is an unconventional oil produced from oil shale rock fragments by pyrolysis, hydrogenation, or thermal dissolution.
- These processes convert the organic matter within the rock into synthetic oil and gas.
- Difference from crude oil:
- The key difference between shale oil and conventional crude is that the former, also called ‘tight oil’, is found in smaller batches, and deeper than conventional crude deposits.
- Its extraction requires creation of fractures in oil and gas rich shale to release hydrocarbons through a process called hydraulic fracking.
- Largest producers:
- Russia and the US are among the largest shale oil producers in the world, with a surge in shale oil production in the US having played a key role in turning the country from an importer of crude to a net exporter in 2019.
- A number of US shale exploration firms, including Halliburton, have faced litigation from citizens living in areas adjacent to shale production sites who have claimed that hydraulic fracking has contributed to groundwater contamination .
- Shale oil extraction methods:
- Mined shale oils are transported to the processing plants, heated to 500OC, and oil comes out from these rocks.
- Situ technique: Oil shale is broken by explosion and Kerogen comes out like crude oil from these rocks.
Prospects of Shale oil exploration in India
- Currently, there is no large-scale commercial production of shale oil and gas in India.
- Limited success: State-owned ONGC had, in 2013, started exploration and, by the end of FY21, assessed shale oil and gas potential in 25 nomination blocks, but has reduced investments over the past few years after only getting limited success in shale exploration efforts.
- Basins: While ONGC’s assessment found prospects of shale oil at the Cambay basin in Gujarat and the Krishna Godavari basin in Andhra Pradesh, the company concluded that the quantity of oil flow observed in these basins did not indicate “commerciality” and that the general characteristics of Indian shales are quite different from North American ones.
- GoI Policy Guidelines: As per the policy guidelines notified by Government of India (GoI) for exploration and exploitation of shale gas and oil in India by National Oil Companies (NOCs), ONGC has identified 50 nomination PML (Petroleum Mining Lease) blocks under Phase-I.
- The exploratory efforts so far have led to the discovery of 65 small-to-medium sized hydrocarbon fields with about 356 million tonnes (oil and oil equivalent gas) of initial in-place on-land reserves.
- The current production of oil and gas is 750-800 tonnes per day and 2.5-3 million cubic metres of gas, respectively.
Policy Guidelines by Government of India
- Exploration for assessing the Shale gas/oil prospectivity has been initiated in 4 basins of the country viz.,
- Cambay,
- KG,
- Cauvery and
- A&AA Basins.
- Since the KG basin holds significant promise for additional reserve accretion, the petroleum ministry is keen to continue the exploratory activity.
- In August 2018, the Central government approved a far-reaching policy that allows private and government players to explore and exploit unconventional hydrocarbons (including shale gas) in contract areas that were primarily allocated for extracting conventional hydrocarbons.
- Unlike conventional hydrocarbons that can be sponged out of permeable rocks easily, shale gas is trapped under low permeable rocks.
- Therefore, a mixture of ‘pressurised water, chemicals, and sand’ (shale fluid) is required to break low permeable rocks in order to unlock the shale gas reserves.
- The process requires around 5 to 9 million litres of water per extraction activity, posing a daunting challenge to India’s fresh water resources.
Tight Oil
- Definition:
- Tight oil is light crude oil contained in petroleum-bearing formations of low permeability, often shale or tight sandstone.
- Production:
- Economic production from tight oil formations requires the same hydraulic fracturing and often uses the same horizontal well technology used in the production of shale gas.
- Found:
- It is found in impermeable shale and limestone rock deposits. Also known as “shale oil,” tight oil is processed into gasoline, diesel, and jet fuels—just like conventional oil—but is extracted using hydraulic fracturing, or “fracking.”
Image Courtesy: Tight Oil
Challenges
- Massive water requirements for fracking
- Potential for groundwater contamination.
- The fracking process poses another challenge of recycling and leakage issues associated with the flowback water which is usually methane-contaminated.
- Excessive methane emission
- Inadequate treatment of drill cuttings
- Waste water disposal techniques not upto the mark
- Relative to conventional sources, shale oil typically produces more pollution to extract, though the extent depends on whether or not the operators avoid wasteful and unnecessary emissions.
Way Ahead
- Using less oil—and transitioning to cleaner transportation technologies—would help decrease the need for unconventional energy sources like tight oil or tar sands.
- More efficient cars and trucks and clean fuel alternatives can cut our oil use, with huge benefits for drivers, the economy, and the country.
- As others make progress toward a cleaner transportation system, oil companies should ensure that the oil we do use doesn’t get worse.
- Avoiding unnecessary flaring, reducing fugitive emissions, and avoiding the dirtiest sources altogether would help minimize shale oil’s emissions.
Source: IE
