USA has announced that with successful exploration and ongoing exploitation of shale gas will make America energy independent in the coming decade. This announcement has triggered rat race for shale gas exploration by other energy dependent countries like India and China and a few European countries. Several research institutes have started investigation on formation conditions, occurrences, accumulation mechanism, resources potential and areas suitable for exploitation together with associated geological and tectonic conditions and groundwater quality conditions. If one browse through the literature published between 2011 and now, USA has published 16 number of publications followed by China (11) and Europe (4). These publications have appeared in top peer reviewed international journals. India has not even seen anywhere over the horizon in this regard. Research findings from research institutes and academicians give support and confidence to oil and gas exploration and production industries to take the findings on a commercial basis. Base data on shale gas is important to assess its commercial viability. The hydrocarbon content in the shale gas depends on environment of deposition of shale beds, provenance, mineralogical composition, maturity conditions and organic content. There are other inherent problems associated with the exploitation of shale gas compared to conventional oil and gas deposits. Shale is compact, and its porosity and permeability low. The conservative-estimated recoverable reserves of shale gas in US, is anywhere between 14 and 28 trillion cubic meters. Recovery technologies included hydro fracturing and horizontal drilling. Since shale formations are homogeneous, the technologies are site specific. Exploration for shale has started in US as early as in 2006 when about 35000 wells were drilled through out the country where ever shale formations are present. With the advancement made in hydraulic fracturing technology way back in 1995, today these Shales are producing 2% of the gas consumed daily in US. The first discovery was made in Barnett Shale in FortWorth Basin.
The first stage of shale gas exploration is the discovery and planning stage where the entire scientific data published is gathered and analysed to understand the characteristics of the shale, environmental issues, economic viability and most importantly, the type of technology to be used to extract the gas. India has large shale formations in all the sedimentary basins: yet our institutes have not focused its research on shale gas resources. For example, our focus is more on “pure academics” on shale rather than “commercial”. Out of the 11 papers published by the Chinese academicians, the focus of investigation is on estimation of shale reserves, environmental problems related to shale gas extraction, methods and key parameters for shale gas resources evaluation, strategic development of shale gas resources and collective impact on water resources etc. The focus is commercial: it is needed and is the way the research should be focused under the current research and development scenario. One has to really struggle to pull out good scientific paper on shale gas resources of India.
China is looking at framework policy of shale gas extraction that safeguards the safety of surface and subsurface events: a policy to distinguish between surface and subsurface events, deterministic events and probable events etc. The data collection, analyses, models have been worked out by research and academic institutes. These investigations are great help to oil and gas exploration and production companies.
Public sector oil companies are conducting R&D work on sedimentary basins of India, targeting the shale formations in the Gondwana and Tertiary sedimentary basins and exploratory drilling has also been carried out for assessing the resources in certain areas. This work has just started now and will take a long way to come out with results leading to exploitation. At least the scientific work being carried out by USA and China research institutes will help our Oil and Gas E & P companies to plan their exploitation strategies. The main concerns surrounding the shale gas extraction are leak of GHG in to the atmosphere, establishment of hydraulic connectivity between shale gas formation and shallow aquifers, water availability for hydro-fracturing shale formations and finally quantity of water needed for hydro-fracturing of shale formation.
These concerns are based on facts: for example wells within a radius of less than 1 km near shale gas extraction facility in Pennsylvania, registered elevated levels of methane in groundwater. Similarly the groundwater registered high Br/Cl and 87Sr/86Sr ratio similar to that of brines from shale formations. These problems will not arise if the extraction site is located off shore. But several shale formations are located on shore. Other issues are related radioactivity and high salinity of the brines produces from these shales.
Indian shale gas estimates vary any where from 8 to 57 TCM, locked in six major sedimentary basins. All these onshore basins are loci of people of all kinds……entomologists to environmentalist. Geological formations do not follow political boundaries. The Assam-Arakan Basin continues into the Sichuan Basin in China. These basins contain shales of different origin…..marine to terrigenous. The marine shale ( continental shelf deposit) have a high TOC of 5.5%, over matured (5%) with a gas content of 6 m3/t. The Paleozoic formation of southern China ( Sichuan Basin) over lies the Mesozoic formations of Assam-Arakan basin thus forming a contiguous stratigraphic unit with shale formation ranging from shelf to marine. Assam, Arunachal Pradesh, Nagaland and Manipur states are convenient regions to exploit shale gas with less environmental problems. However, controlling the GHG escape into the atmosphere is not in our hands. The amount of GHG emissions will certainly be less than conventional fossil fuels but will be more than geothermal source. With sufficient non-conventional sources like geothermal and unconventional hydrocarbon sources like shale gas, India’s energy security is in place and with proper management of these sources it should be possible to be energy independent like other countries.