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A Brief Note on Shale Gas
Background:
Conventionally, Oil & Gas are generated in source rock
(generally shales and occasionally
limestones) and after migration gets trapped in Reservoir Rocks
(generally sandstone &limestone). Vertical & Horizontal
wells are drilled to produce these oil & gas reserves.
Shale gas is a natural gas that could not migrate out of shale
into reservoir and remainsentrapped within shale in pore space and
fractures. These gases get produced from shale in
an unconventional way. Generally, Shales have insufficient
permeability (in Nano Darcy i.e.10
-9D) to allow fluid flow to a well bore. Shale has low matrix
permeability, so gas production
in commercial quantities requires fractures to provide
permeability.
Schematic Geology of Shale Gas Resource
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Shales, that host economic quantities of gas, are rich in
organic material (0.5% to 2.5%) andare usually mature petroleum
source rocks falling in the thermogenic gas window.
Shale gas has become an increasingly important source of natural
gas in the United Statesover the past decade. In USA, shale gas
production contributes to nearly 17% of the total gasproduction in
USA. Shale gas resources in different parts of the world are as
shown below:
Shale gas has been produced for years from shales with natural
fractures. The shale gasboom in recent years has been due to modern
technology in hydraulic fracturing in horizontalwells.
Challenges & Issues related to Shale Gas:
Shale Gas is found in very low permeable shales and requires
drilling of Horizontal wells and
completion through Hydraulic fracturing.
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Hydraulic fracturing requires large amount of water. There may
be environmental issuesrelated to water requirement and water
disposal.
Shale Gas is a cost intensive venture and productivity of Shale
gas well is generally low.Recovery factor of Shale gas resource is
also low and varying.
Shale Gas requires drilling of large number of wells compared to
conventional development ofOil/Gas Fields.
The Shale Gas exploration in India requires formulation of
policy and amendment to P&NGrules.
Status of Shale Gas in India:
Based on the data available from conventional oil/gas
exploration in the country for the last somany years, it appears
that following sedimentary basins may be prospective from Shale
gaspoint of view:
o Cambay Basino Gondwana Basino Krishna-Godavari Basino Cauvery
Basino
Indo-Gangetic Basin
o Assam-Arakan Basin
However, detailed analysis of geo-scientific data gathered
during conventional exploration ofOil/Gas is being carried out to
identify areas/basins prospective for shale gas.
Directorate General of Hydrocarbons (DGH) under Ministry of
Petroleum & Natural Gas(MoPNG) has initiated steps to:
o Identify prospective areas for Shale Gas exploration and
acquisition of additional geo-scientific data
o Formulation of Policy for Shale Gas explorationo Launch First
Shale Gas round by end 2011.
MoPNG, GoI has granted permission to Oil and Natural Gas
Corporation Ltd. (ONGC) for an
R&D project in Gondwana Basin in the existing two CBM Blocks
for exploration of Shale Gas.ONGC plans to drill 4 Pilot wells to
gather data relevant to Shale Gas. Drilling of the first wellhas
commenced.
A Multi Organizational Team (MOT) of DGH, ONGC, OIL, GAIL has
been formed by MoPNGto analyse the existing data set and suggest
methodology for Shale Gas development inIndia.
At the invitation from Department of State (DOS), an Indian
technical delegation (DGH,ONGC, GAIL) attended the Global Shale Gas
Initiative (GSGI) conference at Washington, DCand visited to Shale
Gas site on August 23-25, 2010.
A draft MoU between Department of State, USA and {through DGH)
has been signed onOctober 6, 2010 for the following:
o Assessment of Shale Gas Resources in Indiao Imparting training
to Indian nationalso Assistance in regulatory frameworks
A Technical Workshop is being planned on January 5-7, 2010 for
training on Resourceassessment by USGS team at Delhi.
Way Forward:
After Resource assessment & identification of prospective
areas in the Indian sedimentarybasins, blocks will be carved out
for offer after Mid 2011.
Shale Gas policy is to be formulated and necessary amendments
have to be incorporated inthe P&NG Rules in Mid 2011.
Possible environmental issues to be deliberated with Ministry of
Environment.
