Throughout the world, different
types of sedimentary rocks contain
natural gas deposits, for example
sandstones, limestones and shales.
Sandstone rocks often have high
permeability, which means that the
tiny pores within the rock are well
connected and gas can flow easily
through the rock.
In contrast, shale rocks where gas is trapped as a continuous accumulation throughout a large area usually have very low permeability, making gas production more complex and costly.
The shale gas boom in recent years has been due to modern advancement in technology in hydraulic fracturing (fracking) to create extensive artificial fractures around well bores.
Shale exists in sedimentary basins and typically forms about 80 per cent of what a well will drill through. As a result, the main organic rich shales have already been identified in most regions of the world. Often, enough is known about the geological history to infer which shales are likely to contain gas or oil or a mixture of both. However, the potential zone within shale sequence, the amounts of gas present and what proportion of it can be recovered technically and economically, cannot be known until a number of wells have been drilled and tested. The amount of condensate present in the gas can also vary considerably with important implications of economic production, as condensates command a high price in energy markets. Three factors have come together in recent years to make shale gas production economically viable: z Technological advances in horizontal drilling; z Hydraulic fracturing; and z Increase in natural gas prices in the global market. Horizontal drilling and hydraulic fracturing have dramatically improved daily production rates in USA and also increased the total ultimate recovery potential of individual wells to as high as 54 per cent.
Shale Gas Resource in India :
Having understood that shale rocks, which are the original source rock, have now also become a reservoir or a producing formation, it naturally follows that in every hydrocarbon producing country, there is every likelihood of shales holding hydrocarbons in varying degrees. It is interesting to note, that shales even in non-producing basins could be holding hydrocarbons, opening up a potential in not only the 7 producing sedimentary basins, but in all the 26 basins. It has already been mentioned earlier that the task before exploration and production companies is basically to visualize/learn geological properties of shales to be able to produce oil/gas from them. India, too, has a long experience of exploring and producing oil and gas from on-land sources, and the presence in-depth of shale rocks is largely known more in the 7 producing basins, basically due to the vast exploration already done in these basins. There are no firm estimates of Shale oil/gas in the country
In India, the national oil companies had undertaken a large scale of on land exploration during the last several decades, which has now been supplemented both by them and private companies after the launch of the Production Sharing Contracts (PSC) regime. It is believed that they have drilled several thousand wells, particularly in Cambay, KG and Cauvery basins. These wells had yielded a wealth of data regarding the extent, depth and nature of shale formations in the different sedimentary basins. However, in most other on-land basins, the details of the shale deposits are yet to be fully ascertained. Even the cores of the wells may not have been preserved properly for an analysis of kerogen content. It is also wellknown that under the New Exploration Licensing Regime (NELP) and preNELP contracts, a large number of onland wells have been drilled whose data is available with Directorate General of Hydrocarbons (DGH) for unhindered usage in promotion of the nation’s acreage. This data has to be suitably scrutinized and a full picture developed on the prospectivity of shale gas in the country. We are also aware that the EPINET, the corporate data repository of ONGC (and similar one of Oil India Ltd.) has already hosted a large amount of data on their respective networks. The above data banks need to be networked with active involvement of the NOCs for the shale gas exploitation programme to be implemented on fast track basis.
In contrast, shale rocks where gas is trapped as a continuous accumulation throughout a large area usually have very low permeability, making gas production more complex and costly.
The shale gas boom in recent years has been due to modern advancement in technology in hydraulic fracturing (fracking) to create extensive artificial fractures around well bores.
Shale exists in sedimentary basins and typically forms about 80 per cent of what a well will drill through. As a result, the main organic rich shales have already been identified in most regions of the world. Often, enough is known about the geological history to infer which shales are likely to contain gas or oil or a mixture of both. However, the potential zone within shale sequence, the amounts of gas present and what proportion of it can be recovered technically and economically, cannot be known until a number of wells have been drilled and tested. The amount of condensate present in the gas can also vary considerably with important implications of economic production, as condensates command a high price in energy markets. Three factors have come together in recent years to make shale gas production economically viable: z Technological advances in horizontal drilling; z Hydraulic fracturing; and z Increase in natural gas prices in the global market. Horizontal drilling and hydraulic fracturing have dramatically improved daily production rates in USA and also increased the total ultimate recovery potential of individual wells to as high as 54 per cent.
Shale Gas Resource in India :
Having understood that shale rocks, which are the original source rock, have now also become a reservoir or a producing formation, it naturally follows that in every hydrocarbon producing country, there is every likelihood of shales holding hydrocarbons in varying degrees. It is interesting to note, that shales even in non-producing basins could be holding hydrocarbons, opening up a potential in not only the 7 producing sedimentary basins, but in all the 26 basins. It has already been mentioned earlier that the task before exploration and production companies is basically to visualize/learn geological properties of shales to be able to produce oil/gas from them. India, too, has a long experience of exploring and producing oil and gas from on-land sources, and the presence in-depth of shale rocks is largely known more in the 7 producing basins, basically due to the vast exploration already done in these basins. There are no firm estimates of Shale oil/gas in the country
In India, the national oil companies had undertaken a large scale of on land exploration during the last several decades, which has now been supplemented both by them and private companies after the launch of the Production Sharing Contracts (PSC) regime. It is believed that they have drilled several thousand wells, particularly in Cambay, KG and Cauvery basins. These wells had yielded a wealth of data regarding the extent, depth and nature of shale formations in the different sedimentary basins. However, in most other on-land basins, the details of the shale deposits are yet to be fully ascertained. Even the cores of the wells may not have been preserved properly for an analysis of kerogen content. It is also wellknown that under the New Exploration Licensing Regime (NELP) and preNELP contracts, a large number of onland wells have been drilled whose data is available with Directorate General of Hydrocarbons (DGH) for unhindered usage in promotion of the nation’s acreage. This data has to be suitably scrutinized and a full picture developed on the prospectivity of shale gas in the country. We are also aware that the EPINET, the corporate data repository of ONGC (and similar one of Oil India Ltd.) has already hosted a large amount of data on their respective networks. The above data banks need to be networked with active involvement of the NOCs for the shale gas exploitation programme to be implemented on fast track basis.
