What is the difference between Shale oil and Crude oil?
Shale gas is known as 'Unconventional' as it is found abundant because it is found within the shales deep inside the Earth.
Conventional gas is found in sandstone, siltstone and limestone whereas Shale Gas is found in less permeable rock.
Shale rocks are porous fine-grained sedimentary rocks that allow the extraction of oil from within.
Energy Information Administration (EIA) in 2015 estimated that 214.6 trillion cubic metres of Shale gas reserves across 46 countries in the World.
What is Shale Gas?
It is a form of natural gas (mostly methane) which is found underground in shale rock. It does not flow easily. A large amount of water is required to extract Shale gas from the Shales. As per the London School of Economics and Political Science, Shale gas is expected to account for 30% of world natural gas production by 2040.
Prospects of Shale Gas in India
India has been investing in Shale Gas Exploration to reduce reliance on natural gas imports. In the process, several challenges arise and one of them is the Energy-water nexus. When shale fluid is mixed with groundwater then the problem of contamination arises and in water-scars countries like India and technical lacking of waste-water treatment are a matter of concern.
Currently, Shale Gas Reserves in India are located within the 7 states and exploring around 50 allocated blocks. Extraction of shale gas is much more difficult than conventional gas.
In 2018, the Hydrocarbon Exploration and Licensing Policy (HELP) was implemented by the Central government.
In 2012, the Ministry of Petroleum had released a "Draft Policy for the exploration of Shale oil and gas in India".
What is the future of Shale gas in India?
India consists of a vast quantity of Shale gas reserves. Shale gas was ignored for a long time due to the high cost and complex exploration process.
India has several basins where organic-rich shale gas is present like Cambay, Krishna-Godavari basins, Kaveri basins and Damodar basins. In India, shale gas basins are geographically very complex.
Also, the prospective areas of Shale gas are restricted in some sub-basins.
ONGC in 2013, had drilled its first well for extraction of Shale gas at Kolkata.
Currently, the extraction of Shale gas in India is at the research phase.
According to the policy guidelines notified by the Government of India for exploration and exploitation of shale gas and oil in India by Natural Oil Companies (NOCs), ONGC has identified 50 nomination Petroleum Mining Lease blocks under Phase-I.
This exploratory effort led to the invention 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.
22 assessment wells in 19 PML blocks have been drilled as of 31 March 2017. The required data are being generated or evaluated for Shale gas/oil assessment.
For Shale gas, ONGC has received environment clearance to drill five wells for Shale gas and oil in the Krishna-Godavari basin at an estimated cost of Rs 217 crore.
Difference between Shale oil and Crude oil
It is extracted from oil shale by means of pyrolysis. It is also extracted by the process of Hydraulic fracturing also known as fracking.
While extracting oil from oil shales, intense heat is required to break down a waxy organic matter known as kerogen that is contained within the shale. In the process, the liquid release and gaseous hydrocarbons are similar to those found in conventional petroleum. Such a type of synthetic crude is also known as kerogen oil.
Through two processes the oil is recovered as per the present technology. One consists of mining and crushing oil shale and then transporting the rock to a processing plant. Here, it is heated in special retorts to temperatures of about 500 degrees Celcius.
A large amount of heat releases oil vapours from the rock which liquefy in a series of condensers.
The other process is in situ extraction. In this process, an oil shale deposit is fractured with explosives. After this, a mixture of gas and air is pumped into the deposit and ignited to heat the rock.
The pyrolysis of the kerogen underground produces vapours of oil then upon condensing pumped out very similar to crude oil.
Mainly, crude oil is found in coarse-grained, permeable and porous sedimentary rocks like sandstone and limestone. From this, it can be drawn by using the natural formation pressure alone or if required some well-established technology is used like mechanically pumping the oil out or forcing gas or liquid into the reservoir.
Crude oil is a mixture of volatile liquid hydrocarbons and also contains nitrogen, sulphur and oxygen.
All crude oil almost ranges from 82 to 87 per cent by weight and 12 to 15 per cent hydrogen by weight.
They are also characterised by the type of hydrocarbon compounds that are most prevalent in them like paraffin, naphthenes, and aromatics.
The physical properties of crude oil also vary widely in appearance, it ranges from colourless to black. Specific gravity is also the most important physical property.
Depending on the level of sulphur, crude oil is also categorised as 'sweet' or 'sour'.
Crude oil occurs underground, at several pressures depending upon depth. The crude oil primary destination is the refinery.
Therefore, we can say that crude oil is often drilled via more straightforward methods than shale and natural gas. So, the primary difference between crude or conventional oil and shale oil is the way it collects.