IASPEI - Picture Gallery

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS016 Poster presentation 2355
Gas-hydrates: a future potential source of energy in India
Dr. Kalachand Sain
Marine Geophysical Group National Geophysical Research Institute
KALACHAND SAIN National Geophysical Research Institute, Uppal Road, Hyderabad - 500 007, India
The energy-demand in developing countries like is growing very fast compared to industrial countries of
the world. At present we import more than ~70% of our energy requirement and major discovery of
hydrocarbons have not taken place during the last couple of decades. Since the economic growth with
our huge population depends heavily on the energy security, we are desperately looking for an alternate
form of energy. Gas-hydrates seem to be the best alternative. Gas-hydrates are crystalline from of
water and low molecular weight hydrocarbons (mainly methane), and are formed at high pressure and
low temperature in the outer continental margins and permafrost regions. These have attracted the
global attention due to their wide-spread occurrences and potential as future major energy resources.
Parameters such as bathymetry, seafloor temperature, sedimentary thicknesses, rate of sedimentation,
total organic carbon content etc. indicate good prospects of gas-hydrates in the huge continental
margins of . The methane gas stored in the form of gas-hydrates and underlying free-gas within our
exclusive economic zone is estimated to be of the order of trillion meter cube, which can take care of
our energy requirements for several tens of decades. The National Gas Hydrates Programs under the
aegis of the Ministry of Petroleum & Natural Gas and the Ministry of Earth Sciences have initiated a lot
of scientific plans and technological advancement for the exploration and exploitation of gas-hydrates.
As a member of the national program, we are mainly involved in finding out the prospective zones and
evaluating the resource potential using geophysical (seismic) data. Gas-hydrates are mostly detected by
identifying an anomalous reflector, known as the bottom simulating reflectors or BSR on seismic data
based on its characteristic features. We identified BSRs on available seismic data in the Kerala-Konkon,
Krishna-Godavari andMahanadi basins and the Andaman region. The recent drilling expedition at the
identified locations of gas-hydrates occurrences delineated a rich gas-hydrates deposit in the Krishna-
Godavari basin. The Mahanadi basin and the Andaman region have been found very prospective for
gas-hydrates. Much of the deep-water regions are yet to be explored. New data sets with suitable
parameters are to be acquired to comprehend the lateral/areal extension of gas-hydrates, and assess
their resource potential along the margins of Indian continent. As gas-hydrates are not stable at NTP,
the existing technique, generally used for conventional hydrocarbons, cannot be used for exploitation. A
concerted effort is going on in this direction. With the growth of technology, it is expected that methane
from below the gas-hydrates can be exploited economically in near future. It may take a decade or so
to produce gas from gas-hydrates. Therefore, it is high time to map the prospective zones of gashydrates
and evaluate the resource potential. For this purpose, we have developed several seismic tools
like traveltime tomography; waveform inversion; AVO inversion; AVO attributes; quality factors, seismic
attributes etc. and will demonstrate their application to multi-channel marine seismic reflection data. We
will also show that studies of quality factor and proxies like pockmark and gas escape features (like
faulting or gas-chimney) offer indirect evidences for the identification of gas-hydrates in absence of
BSR. As pure gas-hydrates have much higher seismic velocities than that of host sediments, presence of
gas-hydrates increases seismic velocities, whereas free-gas below the hydrates-bearing sediments
reduces the seismic velocity. Thus estimating accurate velocities using waveform tomography followed
by rock physics modeling or invoking effective medium theory provide an excellent tool for quantifying
gas-hydrates and/or free-gas across a BSR.