Title:Geological, geophysical, geochemical and microbial studies of the Indian continental margins to decipher gas hydrates

Vision:

To understand diverse geological environs in an attempt to decipher gas charged sediments and gas hydrates utilizing various geochemical, geophysical and microbial proxies

Objectives:

• Acquisition of high resolution seismic reflection data
• Collection of long (~ 20 m) cores to study of geological, geochemical and microbial parameters to infer proxies related to gas hydrates
• Identification of gas hydrates prone zones along the Indian continental margins through regional scale multidisciplinary investigations.
• To understand the process of generation and accumulation of hydrates in marine sediments
• To understand the impact of gas hydrates dissociation on geological environment and climate
• Study of ecological and economic aspects of gas hydrates
• To recommend suitable sites for deep drilling, ground truth validation and resource estimation.

Team Members:
Ramana, M.V.
Borole, D.V.
Karisiddaiah, S.M.
Naik, G.P
Rao, B.R.L.
Desa, M.
K. Muralidhar
DeSouza, M.J.B.D.
Dewangan, P.
Muzumdar Anida
Harkantra, S.N.
Charyulu, R.J.K.
Marathe, P.
Phadte, G.M.
Khalap, S.T.
Satelkar, P.S.
Fernandes, W.A.

General Description

Gas hydrates are naturally occurring solids comprised of water molecules forming a rigid lattice of cages, each containing a guest molecule of natural gas. Methane is the most abundant guest molecule in gas hydrates. Theoretically, 1 m³ of methane hydrate can contain up to 164 m³ of methane gas and 0.8 m³ of water at normal standard temperature and pressure conditions. The extent of worldwide gas hydrate occurrences has been evaluated for permafrost and offshore regions by seismic techniques and drilling. The estimate of total global carbon based on the inferences of gas hydrates and fossil fuels from both oceans and land deposits and atmosphere is of the order of 18 Trillion tonnes of which the gas hydrates alone amounts to 10 Trillion tonnes. Thus, the huge reservoirs of gas hydrates are perceived to be the future alternate energy resource.

Gas hydrates are stable under certain pressure and temperature conditions and usually occur in the continental slope regions of tropical oceans and permafrost regions at high latitudes. The gas hydrate stability thickness map (Fig.1) prepared by NIO scientists using the phase equilibrium curve of hydrate zone and free gas, hydrothermal profile and geothermal gradient, and has been used to predict the likely occurrence of gas hydrates under seismic contraints along the Indian continetal margins.

Indian Scenario

Realizing the potential of gas hydrates (new energy resource) and based on the preliminary indications from the existing multichannel seismic data, Secretary, Ministry of Petroleum and Natural Gas (MoP & NG), Government of India constituted an expert committee to examine the feasibility and its exploration. The National Gas Hydrate Programme (NGHP) was formulated based on the recommendations of the expert committee and is being monitored by a Steering Committee headed by Secretary, MOP & NG with Oil Industry Development Board (OIDB), ONGC, GAIL (India) Limited, OIL, DGH, NIO, NGRI, DOD, NIOT, EIL, RIL as members. The Director General of Directorate General of Hydrocarbons (Technical Coordinator) in consultation with other participating agencies has drawn up an ambitious plan and prepared Road Map to tap these gas hydrate resources from the Indian continental margins. As a first step, The Technical Committee evaluated the existing multichannel seismic reflection data.

Presence of gas hydrates world over in general has been inferred by mapping the anomalous acoustic indicator known as the BSR (Bottom Simulating Reflection) on seismic reflection data. The GHSZ map inconjucture with the MCS data (Fig.2)has been used and predicted the probable occurrences of gas hydrates in marine sediments in Indian offshore. Accordingly two offshore model laboratories, Goa and Krishna-Godavari offshores have been identified for detail investigations.

Collaboration:

NIO in collaboration with GAIL (India) Limited and Oil and Natural Gas Corporation Limited (ONGC) undertook multidisciplinary investigations under the aegis of National Gas Hydrate Programme conceived by the Ministry of Petroleum and Natural Gas, Government of India. According to the work plan, NIO acquired geological, geochemical geophysical, microbial and oceanographic data sets in the Goa offshore, West Coast and Krishna-Godavari (KG) offshore, East Coast of India respectively during 2002-03 onboard Research Vessels ORV Sagar Kanya and AA Sidorenko, and completed the analyses, inferred some proxies related to gas hydrates and the two technical reports were submitted to the DG of DGH. .

The quantum of data collected for the first time in the Indian offshore under gas hydrate exploration programme is given below :

Achievements: For the first time multidisciplinary data has been acquired in the Indian offshore areas and attempts were made independently to establish the methodology of data processing, analyses and interpretation, and inferred the proxies such as gas escape features (Figs 3-5), geochemical anomalies (Fig.6) related to gas hydrates.

Facilities created :
The following equipment and analytical and other ancillary facilities were added to the gas hydrate laboratory at NIO.

1. Gas Extraction Units
2. Gas Chromatograph
3. Ion Chromatograph
4. Alkalinity meter
5. Coulometer
6. Microbiological Laboratory with facility for investigation up to DNA level
7. Workstations with ProMax-2D and Geographic seismic interpretation software
8. Deep Tow Digital Side scan and chirp sonar system
9. CTD systems
10. Geological sampling devices
11. High precision Microscope
12. Planetary ball mill
13. Vacuum pumps & gauges
14. Air circulation oven
15. Belly Dancer
16. UV Tans illuminator
17. Ice flake machine
18. PCR machine
19. SS Shaking water bath with digital control
20. Laminar floor cabinet
21. Refrigerated laboratory table top centrifuge speed

Scientific results:

Implications of these studies:

Based on the results obtained from the integrated studies and critical reevaluation of the multichannel seismic reflection (both 2D and 3D data), the NGHP Technical Committee recommended for ground truth validation. As an outcome of the recommendations, the drill ship "JOIDES Resolution" was being utilized for R&D purposes through an agreement between Directorate-General of Hydrocarbons and a "US Consortium", which was currently involved in drilling Gas hydrates in the Indian offshore waters (May-Aug 2006).

Gas hydrate drilling programme