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Outcrop Analogs to the Offshore Sarawak Miocene Buildups, how effective can
they be? The Subis Limestone as an Example
AbderRahmane Dedeche
SE Asia Carbonate Research Laboratory
(SEACaRL)
Universiti Teknologi PETRONAS
Overview • Background
o Regional setting
o Motives behind this study
o Study area
o Previous studies
• The Subis Limestone o Architecture
o Depositional facies
o Depositional environments
o Depositional cycles
o Facies stacking patterns
o Growth history model
• Analogy Discussion
• Conclusions
Background • The Miocene carbonate buildups of Southeast Asia
are prominent for containing commercial amounts
of natural unassociated gas.
• Accurate depiction of reservoir heterogeneity is
crucial to realistic reservoir modeling.
• Grammer et al. (2004) emphasized the importance
of outcrop analogs in providing a proxy for the
subsurface.
• Published analog studies for the Southeast Asia
carbonates are relatively few (e.g. Noad, 2001;
Bassant et al., 2004)
4/2/2013 Abder Rahmane Dedeche 3
Sedimentary Basins in S.E.A.
BINTULU
MIRI
50 MILES
0 50 KM
0
>220 platforms were mapped
Age: Mid – L. Miocene
Size: Up to 7x12 km2
Suai
Subis
Sources : PETRONAS (1999), M. Yamin and Abolins (1999), Haile (1956) Courtesy: M. Yamin Ali/2009
CENTRAL LUCONIA
TINJAR PROVINCE
Niah Caves
Bukit Kasut
Debestone Quarry
Batu Niah
Niah National Park-HQ
to Miri
to
Bintulu
to Miri
Gunung Subis Peak 365m
Previous Work Shell Geologists:
Jordi (1953) Haak (1955)
Sleumer (1977)
Geological Survey
Department: Liechti et al. (1960)
Haile (1962)
Academics: Che Aziz (1993)
Roohi (1994)
4/2/2013 7
Subis Hill/Platform
4/2/2013 Abder Rahmane Dedeche 8
Batu Niah
Niah Caves Quarry
Structural Setting
4/2/2013 Abder Rahmane Dedeche 9
Trusan fault (Haile, 1962)
Stratigraphic setting
4/2/2013 Abder Rahmane Dedeche 10
4/2/2013 Footer Text 11 Nyalau Sands Fm. Tangap Fm.
Setap Shales Fm.
Subis Lst. Mb.
LOWER SEQUENCE
UPPER SEQUENCE Debestone quarry
Niah Caves
1 km
Well Subis-2
Depositional Facies Facies Texture Components Energy Depositional Environment
1 Algal, Miliolid
Wackestone to
Packstone
Wackestone to
packstone
red algae,
benthic foraminifera (lepidocyclina,
milliolids)
low shallow protected subtidal environment (shallow
lagoon)
2 Miogypsinid,
Rhodolith
Packstone to
Grainstone
Packstone,
occasional
localized
grainstones
red algae (rhodoliths),
benthic foraminifera (miogypsina),
gastropods
medium back-reef sand shoal/tidal channel
3 Coral
Framstone
Framestone hermatypic coral (e.g. acropora, faviida),
solitary corals (e.g. porites)
high reef front, reef crest
4 Coral Rubble
Floatstone
Floatstone, matrix:
wackestone to
packstone
coral fragments larger than 2mm,
carbonate mud and sand
medium back-reef
5 Coral Rubble
Rudstone
Rudstone more than 80% coral fragments larger than
2mm
high reef flat
6 Algal
grainstone
Grainstone fragments of articulated coralline red
algae,
benthic foraminifera (amphestigina,
lepidocyclina)
high back-reef sand shoal, beach
7 Algal
bindstone
Bindstone corals (mostly branching and encrusting),
encrusting coralline red algae, encrusting
foraminifera
high reef front, reef crest
8 Skeletal,
peloidal
Wackestone
Wackestone carbonate mud, pelloids,
fine skeletal fragments (mollusks, corals)
low deep protected subtidal environment (deeper
than 20m)
Algal, Miliolid Wackestone to Packstone
Miliolids, Austrotrillina,
Amphistegina, Alveolina,
Marginopora,
Miogypsina and
Lepidocyclina;
Coralline red algae;
Mollusk fragments;
Echinoderm fragments.
Interpretation: Shallow
lagoon.
Abder Rahmane Dedeche
1 mm
Miogypsinid, Rhodolith Packstone to Grainstone
Miogypsina, Amphistegina,
and Lepidocyclina;
Rhodoliths, Coralline red
algae; mollusk fragments;
Echinoderm fragments.
Interpretation: Backreef
sand/grain shoal
Coral Framstone
Massive and branching
corals in growth position,
interstitial material includes
carbonate mud and
foraminifera. (Reef crest)
Coral Rubble Floatstone Coral fragments,
coralline red algae,
foraminifera, and
carbonate mud.
Interpretation: Back-reef
Coral Rubble Rudstone Branching coral fragments,
massive coral fragments,
carbonate mud.
Interpretation: Reef-flat
Skeletal, peloidal Wackestone
Mollusks: specially bivalves
(Pecten sp.), peloids, bryozoa,
Echinoderm fragments, and
carbonate mud.
Interpretation: Deep lagoon
Depositional Environments 1. Reefal
1. Reef-front
2. Reef-crest
3. Reef-flat
4. Back-reef
2. Protected 1. Shallow lagoon
2. Deep lagoon
3. Sand/grain shoals
3. Shallow open marine
M. Yamin and Abolins (1999)
Depositional Cycles • The Debestone Quarry
exposes the lower part of
the outcropping Subis
Limestone which we
divided into three (4rd
order?) sequences.
• Each of these sequences
is composed of several
thinner higher-order
shallowing-upward
cycles(in terms of
depositional environment)
wac
kest
on
e p
acks
ton
e gr
ain
sto
ne
flo
atst
on
e ru
dst
on
e fr
ames
ton
e
Max. flooding surface
sequence boundary
deep lagoon
shallow lagoon
reef flat
back reef
lagoon/shallow open marine
back reef
0m
5m
10m
15m
Shallowing-upward
(Cycle I)
Shallowing-upward
(Cycle II)
Facies Stack. Patterns
Reef-front
Reef-flat
Back-reef
Reef-apron/sand shoal
Shallow lagoon
Deep lagoon
Gr’, Gp’ < A’ Gr’ > A’ Gp’ < A’
Gr’: Growth/Rim Gp’: Growth/Interior A’: Accommodation
4/2/2013 Footer Text 22 Nyalau Sands Fm. Tangap Fm.
Setap Shales Fm.
Subis Lst. Mb.
BUILD-OUT
BUILD-UP
Niah Caves
1 km
BUILD-IN (?)
Well Subis-2
Growth History
4/2/2013 23
100 m 500 m
N N
Niah Caves
Bukit Kasut
Quarries
Reef Back-reef Lagoon Deep lagoon Island samples
Church Reef Platform, Celebes Sea Gunung Subis or Subis Hill (reconstruction)
Namoluk Atoll, Federated States of Micronesia, Pacific Ocean
500 m
N
Bukit Kasut
Quarries
Niah Caves
Reef Back-reef Lagoon Deep lagoon Sand shoal samples
N
Gunung Subis or Subis Hill (reconstruction)
Growth History
Growth History
4/2/2013 25
100 m 500 m
N N
Niah Caves
Bukit Kasut
Quarries
Reef Back-reef Lagoon Deep lagoon Island samples
Church Reef Platform, Celebes Sea Gunung Subis or Subis Hill (reconstruction)
Growth History
500 m
N
Bukit Kasut
Quarries
Niah Caves
Reef Back-reef Lagoon Deep lagoon Sand shoal Karst surface samples
Little Inagua, The Caribbean
N
Gunung Subis or Subis Hill (reconstruction)
Analogy to producing buildups
4/2/2013 27
Epting, 1980
Selley, 1998
Conclusions • The Gunung Subis represents an ancient tropical
isolated carbonate platform, rimmed by a coral-
algal reef, enclosing a vast restricted lagoon.
• Eight depositional facies compose the Subis
Limestone in the sampled locations; the most
common components are corals, coralline algae
and benthic foraminifera.
• The Debestone Quarry section is predominantly of
lagoonal and back-reef facies; other reef related
facies also occur towards the top of the outcrop.
4/2/2013 Abder Rahmane Dedeche 28
Conclusions • This study supports the division of the Subis
Limestone into two major sequences.
• The quarry outcrop features the building blocks of
the Subis Limestone: the shallowing-upward
depositional cycles.
• The Subis Limestone is characterized by a dominant
aggradational to backstepping growth patterns.
• The Subis Limestone is proven a good architectural
and depositional analog to the Sarawak offshore
buildups. However, digenetically speaking it is likely
of a radical contrast to the former.
4/2/2013 Abder Rahmane Dedeche 29
References Bassant, P., F. Van Buchem, A. Strasser, and A. Lomando, 2004. A comparison of two early Miocene carbonate
margins: The Zhujiang carbonate platform (subsurface, South China Sea) and the Pirinç Platform
(outcrop, southern Turkey), in Integration of outcrop and modern analogs in reservoir modeling: AAPG Memoir 80, p. 153-170.
Che Aziz bin Ali, 1993. Sedimentology and Diagenesis of the E11 Carbonate Builup and the Subis Limestone (Miocene), Sarawak, Malaysia. University of Reading. Unpublished PhD thesis.
Epting, M., 1980. Sedimentology of Miocene carbonate build-ups, Central Luconia, offshore Sarawak. Geological Society of Malaysia Bulletin, 12, 17-30.
Grammer, G. M., P. M. Harris, and G. P. Eberli, 2004. Integration of outcrop and modern analogs in reservoir modeling: Overview with examples from the Bahamas, inIntegration of outcrop and modern analogs in reservoir
modeling: AAPG Memoir 80, p. 1-22.
Haile, N.S., 1962. The Geology and Mineral Resources of the Suai-Baram Area, North Sarawak. Geological Survey Department, British Territories in Borneo.
Hutchison, E.S. 2005. Geology of North West Borneo, Sarawak, Brunei and Sabah. Elsevier B.V. pp131-158.
James, N. P., 1983. Reefs, in: Carbonate Depositional Environments. P. A. Scholle, D. G. Bebout and C. H. Moore (eds.). AAPG Memoir 33, Tulsa, p. 345-462.
Mazlan b. Haji Madon, 1999. North Luconia Province. In: The Petroleum Geology and Resources of Malaysia.
PETRONAS, Kuala Lumpur, pp. 443–454.
Noad, J., 2001. The Gomantong Limestone of eastern Borneo: a sedimentological comparison with the near-contemporaneous Luconai Province. Palaeogeography, Palaeoclimatology, Palaeoecology 175, 273-302.
Roohi, G., 1994. Biostratigraphy of the Subis Limestone, Sarawak. Unpublished thesis. University Malaya.
Selley, Richard C., 1998. Elements of Petroleum Geology. Academic Press. Plate 3.
Sleumer, B. H. G., 1977. Paleoecology and internal architecture of the Subis Limestone complex (Sarawak). Unpublished internal report. Shell Sarawak Bhd. Exp. R. 50108. The Hague 2076. 22p.
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