Gas Hydrates: Anomalous behavior of gas hydrates in Indian Exclusive Economic Zones

with Advances in Exploration and Exploitation Techniques – A Review

16th March, 2013.

Significance

History

Occurrence

Identification methods

Case study

Exploitation techniques

Challenges/problems

Conclusion

References

Presentation Outlay

Significance

+

1m3

164m3

0.8m3

STP

A REVIEW OF THE PAST First observed in 1810 in the laboratory of Sir

Humphrey Davy as Chlorine hydrate.

In 1930s, Hammerscgmidt discovered hydrates as “pipeline blockage”.

Later in 1970’s, Russian scientists made an allegation that gas hydrates can be entrapped in water and can have large reserves formed under natural environment.

Investigations were followed by the discovery of gas hydrates in: Siberian permafrost regions (Makogon et al. 1971) Mackenzie Delta, Canada (Bily and Dick 1974) Black sea and Caspian sea (Zhizhchenko and Yefremova, 1974)

Plausible Hydrate Formation Zones (jones et al., 2010)

Geophysical Proxies for Gas HydratePockmark DiapirWipeouts VAMPSGas chimney Mud volcanoSeafloor collapse VentingTransparent zone Fluid flow along faultsAmplitude reduction

(Wood et al., 2002)

LOGGING TOOLS Logging tools most commonly used for refinement of

estimates : Type of Log Response to

Hydrates

Mud Log Increase of gas in Drilling mud

SP Less negative compared to free gas zone

Acoustic Transit Time Decreases relative to water or free gas Resistivity Higher relative to free gas Density Very small decrease Neutron Porosity Nearly same as liquid water Caliper Oversized drill hole NMR Determine the amount of hydrates

QUANTIFICATION USING CORES Two common ways of identifying

hydrates in cores: IR imaging Pressurized core sampling systems

A third method of sensing hydrates

is by use of chlorinity

A fourth rapidly evolving method: CT scanning

Applies x-ray imaging techniques

Methane Hydrate Reserves in India

Gas hydrate stability thickness map (Sain et al, 2011).

CASE STUDY

KRISHNA GODAVARI BASIN

Area of about 28,000 sq. km onshore and 145,000 sq. km extending in the offshore.

National Geophysical Research Institute (NGRI) acquired 2-D multi channel seismic (MCS) data between 500 to 1500 m water depths.

Locations of seismic profiles (black lines) showing MCS data acquired in KG basin. The identified BSRs have been marked white. Red and green lines locate seismic sections that exhibit representative BSRs in next Figure (Journal Geological Society of India, 2012).

Distinct BSR on specimen seismic sections along the (a) red and (b) green lines, shown in above figure in KG basin. The CDP interval is 12.5 m (Journal Geological Society of India, 2012).

KRISHNA GODAVARI BASIN

The predicted GHSZ thickness below the seafloor is around 300m.

The BSR being the primary proxy, other proxies that have been identified in K-G basin: Polarity reversal Pockmarks Gas chimneys Crosscuts different lithological boundaries Amplitude blanking Pore water chemistry (To infer sulfate and chloride

anomalies)

KRISHNA GODAVARI BASIN

The gas hydrate occurrence in KG offshore is associated with fractured clay.

Microbiological studies (mainly enumeration of sulfate and nitrate reducing bacteria and nitrifiers) indicate the sediments are conducive for growth of different bacteria.

The good concentration of TOC in the cores adds value to the suitability for Gas hydrate exploration.

EXPLOITATION TECHNIQUES

Gas hydrate production techniques for marine deposits (Collett et al., 2009).

CHALLENGES/PROBLEMS•Some of the common challenges/problems

as recorded in history are:oAppropriate modeling of gas hydrates

response.oPipeline construction for their

transportation.oHigh water and sand production. oInstability of the surface hole during

hydrate dissociation.oSlugging and Liquid loading.oLack of proven conventional technology

world over.

CONCLUSIONLarge potential source of energy requires

proper identification. Understanding of the fluid behavior including

phase change, liquid accumulation, flow regime, velocity, temperature, and pressure profile to make that the proactive decisions regarding operation and management of the system.

Indian offshore has vast reserves of gas hydrates and the need is of potential recovery with the implication of the recovery methods.

Suitability of the recovery methods depends on proper understanding of the mechanism of their formation and proper treatments.

REFERENCES

Sloan, Koh (2008). Clathrate Hydrates of Natural Gases, third edition. CRC Press.

Carroll, J. (2009). Natural Gas Hydrates A Guide for Engineers, second edition. Elsevier.

Sanjeev Rajput*, M. K. (2009). Seismic indicators of gas hydrates and associated free gas, SEG International Exposition and Annual Meeting. Houston .

Muhammad Iqrar Qadir, M. A. (Nov. 2011). Gas Hydrates: A Fuel for Future but Wrapped in Drilling Challenges, SPE 156516.

Kalachand sain, M. o. (June 2012). Gas-hydrates in Krishna-Godavari and Mahanadi Basins. New Data, journal geological society of india.

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