gas hydrates anomalies and identifications
TRANSCRIPT
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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