Unconventional Today… Conventional Tomorrow

Dr Aninda Mazumdar,
Associate Professor ACSIR, Gas Hydrate Research Group, CSIR-National Institute of Oceanography (NIO)
India's National Gas Hydrate Programme (NGHP) was initiated in 1997 with an intention of developing Gas Hydrate in India, which has significant potential as it represents a large amount of hydrocarbons trapped in the hydrate phase and has an important role to play in highly energy starved country like India. Dr Aninda Mazumdar, Associate Professor ACSIR, Gas Hydrate Research Group, CSIR-National Institute of Oceanography (NIO) - the government research institution which has been involved geoscientific & seismic data acquisition of gas hydrates reserves in India - discussed the potential, technology and environmental challenges of gas hydrates development in the country with an exclusive interaction with Rakesh Roy.

Please apprise us the worldwide potential and development of hydrocarbon from gas hydrates.
Methane gas hydrates, the unconventional natural gas source which is mostly found in marine environment, consist of more than 90 per cent of methane (CH4) and rest water (H2O). Gas hydrates are stable under specific high pressure - more than 1000 meter of water depth and low temperature - around 5 to 6 degree - condition. In a gas hydrate, the gas molecules are 'caged' within a crystal structure composed of water molecules. Normally in a crystal structure gas hydrate, there is one molecule of methane for every six molecules of water.

Per unit volume of gas hydrates contain large amount of gas. For example, if one meter cube of methane hydrate, which is present at the seabed condition at low temperature and high pressure, is brought to the normal room temperature, it will expand and around 164 meter cube of gas and approximately 1 meter cube of pure water will be produced.

So the potential of gas hydrates is huge and the reserve of gas hydrate worldwide is much more than all the fossil fuels like conventional petroleum and natural gas. It is estimated that the worldwide gas hydrates reserve is double the conventional hydrocarbon resources. But there are a lot of problems to monetise the gas hydrates.

The potential of gas hydrates depend on the availability of technology and economic feasibility to extract methane from the hydrate. The nature of the host sediment and the structural/stratigraphic control on hydrate accumulation dictates whether gas can be extracted or not.

Worldwide marine methane hydrates are commonly found in the fractures and fault zone, as disseminated thin layers in clay/silty sediments and as pore filling cement in the sand bodies. Mining of gas hydrates from stratigraphically controlled deposits like sand reservoir is apparently the method owing to high permeability. Mining of fracture controlled hydrate is an engineering and technological challenge.

Various studies have assumed that the total gas hydrates reserves worldwide are extremely large - around 100,000 TCF, but a very small section of such huge reserves is extractable. One of the first pilot scale experiments on exploiting gas hydrates was done in Mallik well in Northern Canada to find out whether the unconventional gas is economical sustainable or not. Subsequently, Japan has carried out pilot scale exploitation of gas hydrates in Nankai Trough for 7 days, but abounded the project due to the technical difficulties. So two things - the sustainability of gas production and the technical feasibility - are the major concerns while exploiting gas hydrates .

Can you please throw some lights on Indian context?
In 2015, under India's National Gas Hydrate Programme (NGHP-2), geologists discovered thick deposit of sand saturated with gas hydrates around 930 TCF in the Krishna-Godavari (K-G) Basin with the help of Japanese drilling vessel Chikyu. Earlier in 2006, as part NGHP-expedition-1, India discovered significant hydrate reserve in the fractured clay-silt sediments of K-G basin and Mahanadi basins. While the total conventional gas reserves of India is projected around 50-60 TCF, even if 10 percent of the estimated gas hydrate reserves can be exploited, it can power for the country for a century. Andaman and Mahanadi basins also have also great potential for gas hydrate reserves, however more exploratory work has to be carried out for proper assessment.

What are the technical and environmental challenges in monetising hydrocarbon potential of gas hydrates globally?
Basically, there are four technologies - 1) Thermal Stimulation, where the temperature is increased above the hydrate stability region; 2) Depressurisation, where the pressure is decreased below the hydrate stability region; as it was used in Mallik well; 3) Chemical Injection of Inhibitors, where the temperature and pressure conditions for hydrate stability are shifted; and 4) CO2 or mixed CO2 and N2 exchange, where CO2 and N2 replace CH4 in the hydrate structure.

There are three major issues in terms of environmental concerns in exploiting methane from gas hydrates. One is leakage or emission of methane while exploiting gas hydrates, which will enhance the methane concentrations in the atmosphere. Being a strong greenhouse gas (~20 times stronger than CO2), enhanced methane flux to atmosphere can contribute to global warming. As our Arctic region is full of methane under the frozen soil cover (permafrost) and ice, there is a concern over uncontrolled release of methane from hydrate formations due to melting of ice prompted by global warming and further increase in atmospheric methane flux.

Other issue is that the thawing of hydrates during exploitation may release large amount of water destabilising the sediment reservoir. Destabilisation may cause damage to establishments as well as trigger slides or sediment massflow which may lead to Tsunami like situation.

Additional thing is that drilling and use of chemicals to exploit gas hydrates could impact the benthic biota or living organisms in the marine environment, which is a cause of worry among marine ecologists worldwide.

As the exploration & exploitation of gas hydrates is currently in nascent stage, what are the roles of R & D before going for that, especially in Indian context?
Potential ecological and environmental risks to develop & monetise gas hydrates are being flagged by many experts and geologists. The considerable rewards of releasing methane from gas hydrate fields must therefore be balanced with risks, and more research may be required to determine the likelihood of such risks materialising and whether there are ways of mitigating them.

Research & Development (R & D) for successfully monetising the unconventional hydrocarbon is going on worldwide. India has been involved in gas hydrates research since 1997. The CSIR-National Institute of Oceanography (NIO) is actively involved in the gas hydrate exploration programme from the inception of National Gas Hydrate Programmes (NGHP) under the aegis of Directorate of gas and hydrocarbon (DGH). NIO participated in the NGHP expedition I & II. Ministry of Earth Sciences has also funded NIO's hydrate research programme. NIO has also carried out extensive research on hydrate geology and geophysics in the K-G and Mahanadi basins and prepared the first hydrate stability zone thickness map.

CSIR-National Geophysical Research Institute (CSIR-NGRI) and National Institute of Ocean Technology (NIOT) are also actively involved in hydrate exploration programme in the geophysical studies and technology development .

India has the complete scientific know-how of gas hydrates reserves and their potential but we don't have the proven technology. Countries like USA, China and Japan with their current R & D capabilities have the position to develop viable, sustainable and economical feasible technology to explore gas hydrates but India has not reached to that level. Hence we may have to outsource the technology.

NGHP Expedition-I was more or less outsourced to US Geological Survey (USGS) and NGHP Expedition-II was completely outsourced to Japan Oil, Gas and Metals National Corporation (JOGMEC). The reason is that we don’t have the drilling ships like JOIDES resolution and Chikyu to fully explore the potential of gas hydrates in Indian Basins. In NGHP Expedition-I in 2006, we used JOIDES Resolution Drilling Ship and NGHP Expedition-II, we used Chikyu ship of JAMSTEC.

Can you brief us the policy framework and government's initiatives for developing gas hydrates in the country?
Unlike conventional gas & hydrocarbon, which has a very strong policy, the gas hydrates research & exploration in India is still at a nascent stage so we don't have the well-defined policy framework.

In National Gas Hydrates Program (NGHP) in 2015, the government spent around Rs 616 crore. Prior to that in NGHP leg 1 in 2006, the government spent almost Rs 150 crore. The cost escalated significantly. It will take some time before we enter into deepwater exploration like Mahanadi and Andaman for more detail analyses. The collaborations with USA and Japan were for the exploration part of gas hydrates. So far we have not carried out any pilot scale exploitation/production testing in our basins. Pilot scale of exploitation is necessary to find out whether the gas can be sustainably taken out from Indian basins or not. It is extremely important for the success of the hydrate programme to involve multiple research organisations and scientists with proven skill in hydrate research in the exploration programme. This will help India to become self-reliant and reduce the dependency on other countries for exploration programme.

With the current plunging global oil price, according to you is it the right time to invest in gas hydrates?
Yes, it is the right time to invest in gas hydrates to develop the right technology, know the reserves, economic feasibility, etc. For example, the current plunging oil price is due to the Shale gas revolution of USA and OPEC oil glut. But it will not be continued for ever and I am sure that in the next 30-40 years, the potential of global conventional hydrocarbon will certainly be going down. So countries like India, China and Japan - who have reduced substantially their oil & gas import bills due to the current plunging oil price, should invest in pilot scale of exploration & exploitation of gas hydrates.