Andaman Sea Basin

Hydrocarbon exploration in India’s
remaining frontier offshore regions:
West Coast India v Andaman Islands
Gary Scaife – Geological Advisor
SEAPEX London November 2012
Spectrum Worldwide data map
Focus Areas 2012
Spectrum Far East Current/Upcoming
Highlights
new acquisition, Q4 2012 Approx 5000km 2D
Joint new acquisition with cggv:
Savu Sumba 2011 1325 km 2D
West Timor 2012 Broadseis
3340km 2D PSDM.
Spectrum India Surveys
BANGLADESH
MYANMAR
INDIA
THAILAND
West
Coast
India
Andaman
Sea Basin
SRI LANKA
MALAYSIA
Spectrum Surveys
DEEP WATER
SHALLOW WATER
GS-DWN-2010/1
MB-DWN-2010/1
MB-DWN-2010/2
KK-DWN-2010/1
MB-OSN-2010/1
MB-OSN-2010/2
KK-OSN-2010/1
KK-OSN-2010/2
KK-OSN-2010/3
DEEP WATER
AN-DWN-2010/1
AN-DWN-2010/2
AN-DWN-2010/3
AN-DWN-2010/4
Results of NELP IX
West Coast India v Andaman Basin
West Coast India
Rifted volcanic continental margin as opposed to a simple passive margin. Formed initially by
the progressive breakup of the Gondwana supercontinent, starting approximately 150-180
my ago (i.e in Middle to Upper Jurassic time).
Andaman Basin
Cretaceous to Recent oblique convergence of Indian and Asian Plates with eastwards
subduction of the Indian Plate lead to the creation of a classic Island Arc system comprising
Both Areas Still considered Frontier in terms of Exploration
West Coast India
West Coast India
• 12,000 km of regional 2D seismic data.
• Original processing 2002.
• The survey area extends over:
•
•
•
•
•
Gujarat-Saurashtra Basin
Deep water basins Bombay High
Laxmi Basin
Kerala Konkan Basin
Laccadive basins in the south.
• Reprocessed 2008 2D seismic:
• PSTM
• PSDM
• Interpretation report available
• 2010/2011
• NELP IX Licence Round:
• Deep Mumbai Offshore
• Kerala Konkan Basin area
West Coast India Overview
Original Data
• Deeper Section obscured by volcanics-Late
Cretacaeous/ Early Tertiary (65my) Deccan Traps.
• Only delineate Tertiary prospectivity: To date Bombay
High discoveries in this Tertiary system.
Reprocessed Data
• First time see below volcanics.
• On this data interpreted new deeper hydrocarbon
system in Mesozoic section below the Deccan Trap
Volcanics.
Now can see
• Variety of potential traps and hydrocarbon play typesboth structrural and stratigraphic
• Plays in deepwater area are expected to include:
• Submarine fans
• Turbidites
• Carbonate reefs
• Horst & tilted fault blocks
West Coast India Structural Elements
Stratigraphy
The stratigraphy of the offshore
western margin of India can be
postulated
from
pre-drift
paleogeographic reconstructions
using well and outcrop data from
India, Madagascar and the
Seychelles.
The reprocessing of the 2002
seismic survey has revealed
significant sedimentary section
preserved below the Base
Tertiary
(Deccan
Trap
volcanics).This older section may
range from Triassic Karoo fluvial
sandstones and shales, through
Jurassic marine shales and sands,
to Early Cretaceous restricted
marine shales and sands which
persisted
into
the
Late
Cretaceous between India and
the Seychelles.
Hydrocarbon Potential
Mesozoic ? Gas chimney on a W-E line from the Kerala-Konkan area (Main Horizons: Dark Green:
Intra Tertiary event;Turquoise: Base Tertiary; Light Green: Top syn-rift
Hydrocarbon Seep Evidence
Petroleum seeps associated with the large platform margin fault seen on this line in the deep
offshore Mumbai area. The deepwater part of this line shows the presence of deep seated Mesozoic
grabens. PSDM Section width : 38 kms
Location ( )of high graded satellite seep on NW-SE seismic line in the Deep Offshore Mumbai area
(seep input courtesy of Fugro NPA)
Play Types
Potential plays include the following:
Pre-Rift:
Fault blocks (Horst/Grabens)
Fault related traps
Inverted grabens and other antiforms
Syn rift:
Fluvial channels
Fan deltas
Carbonate platforms
i.e Upper Cretaceous plays (shallow continental setting).
Post Rift:
Pinchout/wedgeout plays
Onlap and drapeover of palaeohighs
Turbidite fans
Carbonate buildups
Reefs
Mumbai Basin
Approx 5km of Paleocene to
recent sediments. Potential
deep water Mesozoic section.
Carbonates & Clastics of shelfal
sequences shown to have good
reservoir facies.
Main source rocks Paleocene to
Mid Miocene age. Potential
Mezozoic shale sources.
Eocene to Mid Miocene
carbonate build ups, Paleogene
wedge outs and fault traps
assumed to be principle targets.
Additional canyon-channel
deposits in deep water along
with Mesozoic potential.
Generalized stratigraphy
Pre Basalt plays recognised from the
Reprocessed dataset
Original Processing (Post Stack Time Migration) on W-E Line from Northern part of survey area
Reprocessing: PSTM
Mesozoic section now seen under the Basalts
Reprocessing (Pre Stack Time Migration – PSTM) of the same line.
PSDM
Pre Stack Depth Migration displayed in Depth. Here the ‘timing’ lines are in depth and shown every 2000
metres. In the centre of the line, the top of the basalt is around 3600m from sea surface (we are in 2400m of
water here) and that it is around 400m in thickness.
Deep Water Mumbai Basin
PSDM Width 140 km
Top Basalt
Base Basalt
Intra
Mesozoic
MB-DWN-2010/1
Deep Water Mumbai Basin
PSDM (in Time) Width 125 km
Miocene
U.Oligocene
L.Oligocene
L. Eocene
Basement
MB-DWN-2010/2
Play: Deep basin with onlaps onto basement highs
Reefal build up on Basement highs
Kerala-Konkan Basin
Deep water block offered over Laxmi
Ridge. Three shallow water blocks over
Shelfal Horst & Graben Province
PSDM (in Time) Width Approx 95 km
Still Frontier basin – only 20 wells drilledmany with gas shows.
Upto 5km of sediments- Cretaceous to
recent.
Main source rocks Jurassic to Paleocene
(and possible Eocene shales).
Deep water targets include
Miocene carbonate build ups, PaleoceneEocene wedge outs, Eocene-Oligocene
channel sands and Miocene turbidite &
distal fan systems. Mesozoic Structural/
Stratigraphic potential
Shallow water targets include carbonate
buildups/banks over basement highs and
cretaceous stratigraphic traps
KK-DWN-2010/1
Reef development
Possible mud diapirism and gas escape
structures
Laccadive Ridge and Cannanore Canyon
system
Section width: 220 kms
Laccadive Ridge and Cannanore Canyon
system - Zoom
Reefal play
Onlap plays
Mesozoic source ?
Section width: 45 kms
Laccadive Ridge - Mesozoic play - Zoom
Andaman Sea Basin
Introduction
Andaman Sea Basin
• Frontier
• Only 13 (now 15) wells
drilled
• All in shallow water close to
Islands
• Only 10,600 Line kms nonproprietary seismic, all 2D
Reprocessing
• All 10,600 line km has been
reprocessed in 2010. PSTM
and PSDM versions
• Interpretation report is also
available.
Andaman Project Size
Very Large Study Area!!!
380kms - west to east
840kms - north to south
Only 10,600 km of Seismic Coverage.
Example of size: North- South Line AN-95-6
is over 600 Km long, which is equal to the
distance from New Delhi to Kathmandu
!!!!!!!
Andaman Project Size
Superimposed on the UK North Sea It
would incorporate the entire Dutch,
German, Danish, Norwegian and UK
Central Grabens plus the UK and
Norwegian Viking Grabens as well as the
Outer Moray Firth Basin.
These North Sea basins together contain
Billion
boe
recoverable
multi
hydrocarbon reserves.
Reprocessing Challenges
• Large area incorporating very varied geological
terrains.
• Different vintages of acquisition/parameters and
sparse grid.
• Big bathymetric range, from very shallow water to
3.6kms water depth.
• Structural /Tectonic complexity:
• numerous steep dips, with the angle and direction of
dip varying dramatically within small distances, very
complicated ray paths and out-of-plane data which:
• Cannot be correctly imaged in 2D processing: is not
positioned correctly by the migration and complicates the
velocity analysis.
300 km
• Contaminate the multiples, reducing the effectiveness of
the demultiple processing.
• Shallow reefs cause scattering of seismic energy; not
conducive to deeper imaging.
Proven Hydrocarbons
Giant producing fields within other parts of the SumatraAndaman-Myanmar belt indicate that the Andaman Sea Basin
could hold substantial gas reserves
North Sumatran Basin: large fields,
e.g Arun, Kuala Langsa and NSO. 28TCF of gas & 3.2Bbbl of
liquids discovered. All in Miocene carbonate reef structures.
Myanmar: large gas fields
Yadana (5 TCF in Miocene carbonates)
Yetagun (3.5 TCF in Miocene clastics).
First well in Andaman Sea Basin (An-01-1) drilled in 1980 was a
discovery in Miocene Limestones. Flowed 6.3mmscfgd on test.
There is a working hydrocarbon system, there is a source,
there are reservoirs, and there are viable sealed structures.
Regional Tectonic Elements of the Andaman area
Andaman Regional Geology
Andaman Islands and basin lie between, and on trend with,
North Sumatra and Myanmar
Basin forms part of an Island arc
Different parts of the Basin have been subjected to different
stratigraphic and tectonic histories in the Cenozoic.
Basin associated with converging plates
•Foredeep (Andaman Trench)
•Inner Slope/Accretionary Prism
•Island arc/Outer Structural High
•Fore- arc
•Volcanic arc
•Back arc
Basin fill can exceed 5000-6000m of thick, deep marine to
shallow marine sediments: ranging from late Cretaceous to
Recent.
Neogene spreading centre separates northern from southern
areas
Regional Tectonic Elements of the Andaman area
Andaman Regional Geology
Spreading centre is opening in a NNW-SSE direction although it comprises a series of segments separated
by NNW-SSE trending transform faults. Currently the spreading rate is reported in the published literature
to be an average of 3.7cm/yr with the total opening since the mid Miocene being approximately 400kms.
In the Back-arc area evidence of active sea-floor spreading can be clearly seen.
Petroleum Systems Overview
From seismic data, the Andaman Sea
Basin Fore-arc area can be shown to
contain a thick succession of sediments
(locally in excess of 7,000 metres thick),
ranging from late Cretaceous to Recent.
Only a part of this succession has been
penetrated by the existing exploration
wells.
The sediment pile is very much thinner
across the spreading centre and the
volcanic arc; however the seismic
interpretation indicates that the
sedimentary section exceeds 4,000
metres in the back-arc basin.
On trend with giant producing gas
fields in Myanmar
On trend with giant producing gas
fields in Indonesia
A geo-seismic cross section from the northern part of the basin
Andaman Basin Drilling History
• Frontier Basin with only 13 (now 15) wells
drilled.
• All drilled between 1980 and 1987.
• The first well was a discovery
• All targeted structural traps.
• Many wells encountered Miocene limestone
reservoir, up to 250+ metres thick.
• Otherwise well sections are shale dominated.
BUT
• Wells were drilled in the shallow water part of
the fore-arc area close to the Andaman Islands
on a high terrace where the sedimentary section
is thinned; out of the Fore arc basin proper.
• No wells in the volcanic arc or back arc regions;
nor in the thicker/axial part of the fore arc basin.
So large parts of the area have no wells!
Therefore, large parts of the sedimentary
basins and sedimentary section have not been
penetrated!
2011 ONGC Drilling Campaign
ONGC ANDW-05 PA Dry
ONGC ANDW-1 Well was drilled to explore the
hydrocarbon potential of shallow Mio-Pliocene and
deeper Oligocene reservoirs on a large structure.
Continuous gas shows were observed during drilling.
Open Hole Dual Packer MDT samples collected at three
points (3084.01 3291.5 and 3292.5m) have established
the presence of gas in Pliocene section. The test carried
out at 3084.01m indicates an absolute open flow
potential (AOFP) of 55 mmscfgpd. The other two tests
also showed good AOFP of gas. The gas discovery at
well ANDW-1 is a big boost to exploratory efforts in the
Andaman Offshore Basin
ENI Spudding of the first well in the
block was delayed from Feb 2011 to
April 2011due to non-grant of
permission from the Department of
Space (DoS). According to DoS the
location fell under the impact zone of
rocket launches.
Petroleum Systems
Two main petroleum source systems have been identified:
Deeply buried thermogenic system.
Mature type III kerogen in wells and in excess of 6000metres
sediment seen on reprocessed seismic
Biogenic/shallow gas system.
Gas samples from AN-01-1 discovery well.
The proven, prolific reservoir, thick, early to mid Miocene
limestones can be directly mapped from the reprocessed seismic
data throughout much of the Fore arc and Back arc basins.
Reservoir in Yadana, NSO, Arun.
Sand deposition, from the Irrawaddy and highlands in Malayan
Peninsular and Sumatra, can be anticipated in the deeper and
axial parts of the basins; these have not yet been penetrated by
wells. Reservoir in Yetagun.
The current understanding is based on the wells in the flanks of
the Fore-arc basin where the current exploration wells have been
drilled.
Generalised Stratigraphies in the Andaman Sea Region
Source & Seal
The shales of the Neogene are expected to provide a
thick, regional seal for the Miocene limestone
reservoir
SP:
Potential source rocks including shales and
mudstones of Late Cretaceous to Oligocene age with
TOC (Total Organic Content) up to 5.2% have been
reported onshore in the Andaman
Well AN-1-1 is reported to have encountered mature
organic type III Kerogen sediments in the preNeogene section.
Thick intervals (in excess of 6,000 metres) of
Cretaceous and Palaeogene sediments have been
interpreted within the project area.
The lower and deeper parts of these areas of thick
Palaeogene to Cretaceous sediments are considered
to be thermally mature source kitchens.
Younger Neogene to Recent sediments could be the
source of biogenic gas, which has been reported as
the source for the gas discovered by the AN-01-1
well.
1300.0
1400.0
1500.0
1600.0
1700.0
1800.0
1900.0
2.500
2.500
3.000
3.000
Seismic Line AN-JV-95-05 Showing Bland/Transparent/Diffuse Seismic Character
Reservoirs
The only proven productive reservoir within the project area
is the Miocene limestone in well AN-1-1.
Limestones of a similar age are the reservoirs to the north
and the south.
Myanmar Yetagun Field is producing from Miocene deltaic
sands: Miocene to Recent sands in the north of the area
brought in by the Irrawaddy Delta.
Neogene aged sand shed from northern Sumatra could be
transported into the southern end of the Fore-arc basin,
near the Nicobar Islands. Also into Southern Back arc
There are also potential reservoirs in the sands of the
Cretaceous to Palaeogene Baratang and Port Blair
Formations; however, these have only been reported from
the outcrops on the Andaman Islands.
Regional Location Map Showing Potential Sediment Input Routes in Red
Hydrocarbon Indications
• Onshore
Andaman
Islands
mud
volcanoes with associated oil & gas
shows
• Reported evidence from satellite seep
surveys
• Seismic features interpreted as gas
clouds/chimneys, sea-floor pock marks
and mounds, bright spots and flat spots
are probable DHI’s.
• Presence of gas hydrates
• Bottom Simulating Reflectors (BSRs) are
observed on many seismic sections.
Pock Marks
and
Vent Mounds
BSR
Flat/Bright Spot
Examples: Trapping Geometries
Possible
Miocene
Reefs
Possible analogues of
successful
producing
multi-TCF
Miocene
limestone
fields
in
Myanmar
and
North
Sumatra
Further Information
gary.scaife@spectrumasa.com
debbie.sewell@spectrumasa.com