Studies on Gas Hydrate Exploration

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Studies on Gas Hydrate Exploration Science
Component
Dept. of Ocean Development EFC Meeting 24 July,
2003
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• Hydrates discovered first in 1810 by Sir Humphrey
  Davy
• GAS-HYDRATESAlso known as clatherate-
• BSR (Bottom Simulating Reflector) interface
  between hydrate bearing sediments above and
  free-gas or water bearing sediments below
• Methane trapped as solid within hydrates and as
  free-gas below BSR

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Gas hydrates estimated potential 2 times the
fossil fuels globally  
Known or inferred occurrences of gas hydrates
in offshore sediments
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• Why Gas Hydrate research?
• Economic
• rising oil import
• Societal Need for
• alternate sources
• Uniqueness of the
• deposits
• 4. Environmental
• Global warming
• Gas hydrates-global
• thermostat.
• Tsunamis
• Bermuda Triangle
• 6. Slope stability

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Gas Hydrate
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Sizes of Organic Carbon reservoir Carbon bound in
GH around 10000 gigaton
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How Much Gas is trapped in Gas Hydrates 80
possible fields in the world. Speculative-3114 to
7624 thousand trillion cubic meters(oceanic) 14-34
thousand TCM in Permafrost regions. Estimates
of the amount of gas hydrates and associated
gas. Messovakh field West Siberia, Russia 37
bcm Blake Ridge range from about 70 tcm to 80
tcm of gas
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• Volume of Gas in Gas Hydrate depends on
• Spatial extent of the gas-hydrate occurrence,
• "reservoir" thickness,
• sediment porosity,
• degree of gas-hydrate saturation, and
• the hydrate gas yield volumetric parameter which
  defines how much free-gas (at STP) is stored
  within a gas hydrate (also known as the hydrate
  number).

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Left Velocity increase in the hydrated
sediments above the BSR and drop in free-gas
bearing sediments below, Right BSR showing
large amplitude, opposite polarity seismic event
w.r.t seafloor reflection.
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The ratio of P-wave velocity above the BSR to
that below the BSR (red line), and of S-wave
velocity above the BSR to that below the BSR
(blue line) versus gas-hydrates saturation, and
for two (left contact and right non-contact)
end member deposition models (Ecker et al., 1998).
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Angle (Degree)
Computed reflection coefficients from BSR for
various concentrations of gas-hydrates of three
fixed saturations of free-gas for contact (left)
and non-contact models (Carcione and Tinivella.,
2000).
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• Objectives of the Study
•  Understand the process of generation and
  accumulation of hydrates in marine sediments
• Undertake regional scale investigation to
  identify promising sites and estimate resource
  potential
• Establish geophysical techniques for detection
  and quantification of gas hydrates 
• Recommendation of suitable sites for drilling
  and ground truth validation.
•    Understand the impact of gas hydrates
  dissociation on geological environment and
  climate
• Demonstrate existence of methane hydrate by
  ground truth sampling/ drilling

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Tools for Science component 1. Geophysical and
Geological Methods 2. Characteristics of
BSRs 3. Manifestations pock marks, gas escape
features 4. Geothermal studies measurement of
geothermal gradient (Inverse relation)
5. Wireline logs wireline well logs valuable
in detection of gas hydrate intervals. 6.
Geochemical proxies to comprehend genesis of gas
hydrates. surface indications. 7.
Microbiological proxies.
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Multibeam system
A 3-Dimensional view of the seafloor
from Multibeam swath bathymetry data (ORV
Sagarkanya)
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Pock Marks on a sides-scan record
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Cruise tracks- LCS Program
AN11
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Seismic sections along line E6 showing 850 and
900 East ridge.
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A Typical OBS
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Geo-chemical Studies 1. Surface sediment cores-
up to 20 m length (ORV SK)- In phase II
integrated studies using new Automatic corer and
Support submersible 2. Chemical analysis for
proxies. 3. Physical properties of sediments-
Gas Hydrates generally occur in coarse sediment
and fractured zones 4. Gas hydrates are
distributed within a broad depth range within
the GHSZ. 5. Lithology influences hydrate
concentration. 6. Different physical and chemical
proxies for hydrate distribution and
concentration give generally consistent
results. Continued
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Geo-chemical studies (continued) 7. Fractionation
and mixing signals provide important constraints
on gas hydrate dynamics. 8. Very high chloride
concentration 9. Gas hydrate concentration is
significantly greater beneath the ridge than
beneath the adjacent slope basin.
10.Microbiological analysis of sediments and
near bottom waters.
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TECHNOLOGY COMPONENT

• NATIONAL INSTITUTE OF OCEAN TECHNOLOGY

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Why Science and Technology ?
GAS HYDRATE

• Term Usage - long repetitive
• Science of Gas Hydrate evolution and occurrence
• Inexpensive technology
• Define methodology for successful location of
  suitable sites for production

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Path to exploration
GAS HYDRATE

• Initial survey
• Location
• Qualify
• Quantify
• Qualification and Quantification (QQ)
• Time consuming
• Elaborative process
• Expert opinions stress on
• Establishing ground truth
• Coring at precise locations
• Joint engagement of NIOT, NIO NGRI

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Unique Tools for GH exploration
GAS HYDRATE

• A multi-sensor multi-activity survey tool
• An Automated Portable Coring System

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Interaction with Russian Scientists
GAS HYDRATE

• ILTP Workshop on Gas Hydrate
• Visits by the Indian scientists under ILTP
• Interaction with Russian Experts
• Visit to Lake Baikal as part of multinational
  expedition for Gas Hydrate sampling

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SS-2500 - a multi-sensor multi-activity
platform for GH exploration
GAS HYDRATE

• Features
• Cameras with strobe and laser TV
• Methane sensors like METS
• Chirp based Sub-bottom profiler
• Side Scan and Chirp Sonar
• Gamma Spectrometer Acoustic-Optical Spectrometer
• Sample collector and Storage
• Chlorine depletion / Oxygen isotope sensor
• Thermal sensors
• To monitor and help in the coring activities

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Automated Coring System (ACS) a
Portable,Inexpensive, multi-sensor tool for
quantification and qualification of GH
GAS HYDRATE

• Features
• Resistivity Log
• Porosity log
• Density log
• Acoustic sonic Log
• Temperature Log
• Dielectric property log
• Automated Stacker and re-claimer system
• Retractable and portable
• Rated 2500m depth coring up to 150m

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Support Submersible (SS-2500)
GAS HYDRATE

• Expected Tasks
• Survey target areas with required sensors to
  facilitate analysis of
• Sub-bottom layers
• Mud volcanoes
• Gas seepages pockmarks
• Sea bottom activities w.r.t. flora fauna
• Water quality
• Shallow coring and water sample collection
• Analysis of collected samples and data
• Identify locations for Coring
• Monitoring the coring activity and intervening
  during drill string re-entry, etc.

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Automated Coring System
GAS HYDRATE

• Multiple coring on target area
• Generate data regarding the sub-bottom layers
• Generate data regarding geophysical properties
• Monitoring of environmental impact and
  parameters
• Videography of the activities
• Storage of core samples
• Analysis of collected samples and data

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What will the present scheme lead to ?
GAS HYDRATE

• Better knowledge of environment, sub-bottom
  characteristics, geophysical parameters, etc.
• Finding suitable sites
• Avoiding ecological unbalance
• Evolution of GH
• Indigenous technology for survey and coring
• Less dependence on outside expertise
• Technical and Scientific skill pool and expertise
• Long Term solution
• Usage in other deep sea explorations

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• Approach strategy and methodology
• Phase-1
• Process and interpret MCS/OBS data to look for
  BSR like features.
• Identify two most promising areas of 100 X 100 km
  in size for
• detailed surveys
• In each prospective area, collect additional
  data.
• Phase II
• Detailed grid pattern MCS/high resolution
  seismics
• Processing interpretation, inversion and
  modelling seismic data
• for possible locations and probable
  quantification
• OBS Surveys to derive both P and S wave 3D
  velocity structure
• Detailed Sampling geochemical studies Support
  submersible/ACS
• rock physics based modelling
• Phase III
• Integration of all results selection of sites for
  drilling for
• ground truth validation

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"a knowledge of where and how far gas hydrates
are extended, what the way of their formation and
dissociation is, what hydrate accumulations look
like is the most significant and topical problem
of the scientific deep sea research" Ginsberg,
1998