The Indonesian Sedimentologists Forum (FOSI)

Transcription

Berita Sedimentologi
MARINE GEOLOGY OF INDONESIA
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Published by
The Indonesian Sedimentologists Forum (FOSI)
The Sedimentology Commission - The Indonesian Association of Geologists (IAGI)
Number 32 – April 2015
Page 1 of 34
Editorial Board
Advisory Board
Minarwan
Prof. Yahdi Zaim
Chief Editor
Bangkok, Thailand
E-mail: [email protected]
Quaternary Geology
Institute of Technology, Bandung
Prof. R. P. Koesoemadinata
Herman Darman
Deputy Chief Editor
Shell International EP
Kuala Lumpur, Malaysia
Fatrial Bahesti
PT. Pertamina E&P
NAD-North Sumatra Assets
Standard Chartered Building 23rd Floor
Jl Prof Dr Satrio No 164, Jakarta 12950 - Indonesia
Wayan Heru Young
University Link coordinator
Legian Kaja, Kuta, Bali 80361, Indonesia
Visitasi Femant
Treasurer
Pertamina Hulu Energi
Kwarnas Building 6th Floor
Jl. Medan Merdeka Timur No.6, Jakarta 10110
Rahmat Utomo
Bangkok, Thailand
Farid Ferdian
Saka Energi Indonesia
Jakarta, Indonesia
Guest Editors
Emeritus Professor
Institute of Technology, Bandung
Ir. Wartono Rahardjo
University of Gajah Mada, Yogyakarta, Indonesia
Dr. Ukat Sukanta
ENI Indonesia
Mohammad Syaiful
Exploration Think Tank Indonesia
F. Hasan Sidi
Woodside, Perth, Australia
Prof. Dr. Harry Doust
Faculty of Earth and Life Sciences, Vrije Universiteit
De Boelelaan 1085
1081 HV Amsterdam, The Netherlands
E-mails: [email protected];
[email protected]
Dr. J.T. (Han) van Gorsel
6516 Minola St., HOUSTON, TX 77007, USA
www.vangorselslist.com
Dr. T.J.A. Reijers
Geo-Training & Travel
Gevelakkers 11, 9465TV Anderen, The Netherlands
Dr. Andy Wight
formerly IIAPCO-Maxus-Repsol, latterly consultant
for Mitra Energy Ltd, KL
Dr. Susilohadi
Pusat Penelitian dan Pengembangan Geologi Kelautan,
(Marine Geological Institute)
Bandung, Indonesia
Dr. Udrekh Al Hanif
BPPT (Agency for the Assessment and Application of
Technology)
Jakarta, Indonesia
Cover Photograph:
A 3D model of Indonesian seafloor, taken from the
proceedings of a scientific meeting to commemorate
the 10th anniversary of the French-Indonesian
cooperation in oceanography (1993).
•
•
Published 3 times a year by the Indonesian Sedimentologists Forum (Forum Sedimentologiwan Indonesia, FOSI), a commission of the
Indonesian Association of Geologists (Ikatan Ahli Geologi Indonesia, IAGI).
Cover topics related to sedimentary geology, includes their depositional processes, deformation, minerals, basin fill, etc.
Page 2 of 34
A sedimentological Journal of the Indonesia Sedimentologists Forum
(FOSI), a commission of the Indonesian Association of Geologist (IAGI)
From the Editor
particular theme. In this issue, we
present you 2 full articles on
seismic stratigraphy and heat
flow estimation from bottom
simulating
reflectors
of
gas
hydrates; an extended abstract on
integrated multibeam, drop core
and seismic interpretation of
North Banggai-Sula seafloor and
a
short
article
on
marine
expeditions in Indonesia during
the Colonial years.
Dear readers,
Welcome to the first volume of
Berita Sedimentologi in 2015!
Berita Sedimentologi publications
in 2015 are dedicated to topics
related to Marine Geology of
Indonesia and are supported by
Dr.
Susilohadi
of
Marine
Geological
Institute
(Pusat
Penelitian dan Pengembangan
Geologi Kelautan) and Dr. Udrekh
Al Hanif of Agency for Assessment
and Application of Technology
(Badan
Pengkajian
dan
Penerapan Teknologi) as guest
editors. This volume, Berita
Sedimentologi No. 32, will be the
first of 3 volumes on the
We also welcome Dr. Andy Wight
who recently agreed to become
one
of
our
International
Reviewers. Dr. Wight is a highly
experienced Petroleum Geologist
who has spent most of his
professional career in SE Asia,
therefore he knows the geology of
the region pretty well. He replaces
Dr. Peter Barber, who has been
very helpful to FOSI in the past.
On behalf of FOSI, I would like to
express our gratitude and thanks
to both Drs. Andy Wight and
Peter Barber.
We continue to seek high quality
articles to be included in Berita
Sedimentologi, so please contact
one of the editors if you are
interested to contribute to our
society. In the meantime, we hope
you enjoy reading this volume.
Chief Editor
Minarwan
Regards,
Minarwan
Chief Editor
INSIDE THIS ISSUE
Plio-Pleistocene Seismic Stratigraphy of
the Java Sea between Bawean Island and
East Java – S. Susilohadi and T.A. Soeprapto
Merits and Shortcomings of Heat Flow
Estimates from Bottom Simulating
Reflectors – Minarwan and R. Utomo
Frontier Exploration Using an Integrated
Approach of Seafloor Multibeam, Drop
Core and Seismic Interpretation – A Study
Case from North Banggai Sula – F. Ferdian
Marine Expeditions in Indonesia during the
Colonial Years – H. Darman
5
Book Review : The SE Asian : History and
Tectonic of the Australian-Asia
Collision, editor: Robert Hall et J.A.
Reijers
17
Book Review - Biodiversity,
Biogeography and Nature Conservation
in Wallacea and New Guinea (Volume 1),
Edited by D. Telnov, Ph.D. – H. Darman
56
58
27
30
Call for paper BS #33 –
to be published in August 2015
Page 3 of 34
About FOSI
T
he forum was founded in
1995 as the Indonesian
Sedimentologists
Forum
(FOSI). This organization is a
communication and discussion
forum for geologists, especially for
those dealing with sedimentology
and sedimentary geology in
Indonesia.
The forum was accepted as the
sedimentological commission of
the Indonesian Association of
Geologists (IAGI) in 1996. About
300 members were registered in
1999, including industrial and
academic fellows, as well as
students.
FOSI has close international
relations with the Society of
Sedimentary Geology (SEPM) and
the International Association of
Sedimentologists (IAS).
Fellowship is open to those
holding a recognized degree in
geology or a cognate subject and
non-graduates who have at least
two years relevant experience.
FOSI
has
organized
2
international conferences in 1999
and 2001, attended by more than
150 inter-national participants.
team. IAGI office in Jakarta will
help if necessary.
The official website of FOSI is:
http://www.iagi.or.id/fosi/
Most of FOSI administrative work
will be handled by the editorial
FOSI Membership
Any person who has a background in geoscience and/or is engaged in the practising or teaching of geoscience
or its related business may apply for general membership. As the organization has just been restarted, we use
LinkedIn (www.linkedin.com) as the main data base platform. We realize that it is not the ideal solution,
and we may look for other alternative in the near future. Having said that, for the current situation, LinkedIn
is fit for purpose. International members and students are welcome to join the organization.
FOSI Group Member
as of APRIL 2015
Page 4 of 34
Plio-Pleistocene Seismic Stratigraphy of the Java Sea
between Bawean Island and East Java
Susilohadi Susilohadi and Tjoek Azis Soeprapto
Pusat Penelitian dan Pengembangan Geologi Kelautan, (Marine Geological Institute), Bandung, Indonesia
Corresponding author: Jalan Dr. Junjunan 236, Bandung-40174, Indonesia; Tel.:+62-22-603-2020;
Fax:+62-22-601-7887; E-mail address: [email protected] (S.Susilohadi)
ABSTRACT
The southeast Java Sea forms a submerged part of the Sunda Shelf and lies on a relatively stable
continental shelf, which reached its final form during the Quaternary. Marine geological investigations in
this area have mostly been carried out as part of regional studies on the Sunda Shelf. Detailed studies,
particularly for younger sequences, are lacking and, as a result, the neo-tectonics and response of the
shelf area to extreme sea level fluctuations during Plio-Quaternary times are poorly known.
A set of high resolution reflection seismic profiles totalling some 3750 line km has been studied. All data
were acquired by the Marine Geological Institute of Indonesia, which ran the survey in the southeast
Java Sea in 1989-1990. The data show that the Late Tertiary sedimentation in the study area partly
occurred in half graben basins, mostly bounded by northeastward trending faults which may be related
to the regional suture belts running from central Java to south Kalimantan. Towards Pliocene time, the
sedimentation occurred in east-trending synclinal basins, which indicate the dominance of a northward
tectonic compressional stress. This continued until the Early Pleistocene, as indicated by some local
thickening of the Early Pleistocene deposits. Since then, further basin development appears to have
ceased, and a tectonically stable condition may have been reached. Quaternary sedimentation
gradually changed the basin morphology into a relatively flat plain characterised by multiple erosional
features resulting from extreme sea level fluctuations.
Keywords: Seismic Stratigraphy, Pliocene, Pleistocene, Java Sea.
INTRODUCTION
The southeast Java Sea forms the submerged part
of the Sunda Shelf and lies on a relatively stable
continental shelf (Figure 1). Marine geological
investigations in the southeast Java Sea have
mostly been carried out as part of regional studies
on the Sunda Shelf (e.g. Emery et al., 1972; Voris,
2000; Ben-Avraham & Emery, 1973). Detailed and
published studies, particularly for the PlioPleistocene periods, are rare, although such studies
are necessary in order to understand the tectonic
and response of the shelf area to extreme sea level
fluctuations during these times.
The present study discusses the sedimentary facies
distribution, chronology and the related tectonism
in the southeast Java Sea during the Late Tertiary
and Quaternary. The discussion relies heavily on
sparker single channel seismic data (Figure 2),
which have been interpreted by applying the
sequence stratigraphic concepts developed by Vail
et al. (1977) and Posamentier and Vail (1988).
However,
this
study
lacks
reliable
age
determinations, as well as other published
geological studies. In addition, problems inherent
from the equipment include: (1) the limited
penetration, (2) and the presence of strong multiple
reflections, particularly in the area where surficial
reflections are strong.
REGIONAL GEOLOGY
Based on regional geophysical data, Ben-Avraham
and Emery (1973) noted that Tertiary sedimentation
in the southeast Java Sea occurred in basins which
were bounded mostly by northeastward trending
faults (Figure 1). Many of these structures are half
grabens that formed on the pre-Tertiary shelf
(Kenyon, 1977; Bishop, 1980). These major features
were interpreted by Ben-Avraham and Emery (1973)
as resulting from past interaction between the
Eurasian and Indian-Australian lithospheric plates,
the principal ridges probably representing part of an
island arc system that was active during the Late
Cretaceous-earliest Tertiary (Bishop, 1980). Such
an island arc complex has been deduced from the
occurrence of pre-Tertiary ophiolites cropping out in
Central Java and in Southeast Kalimantan (van
Bemmelen, 1949) possibly representing a previous
subduction complex (Katili, 1989).
The Karimunjawa Arch is the dominant ridge in the
eastern Java Sea. It extends into the offshore area
of southern Kalimantan as a broad positive feature
(Bishop, 1980).
Page 5 of 34
Figure 1. Location of the study area and the generalized Tertiary basement configuration according to Kenyon
(1977). Superimposed on the Java Sea is Molengraaff river system of the last glacial period,which has been
deduced from the first Snellius expedition (Molengraaff, 1921; Kuenen, 1950).
It is capped by the Karimunjawa Islands on which
pre-Tertiary quartzite and phyllitic shale, cut by
basic dykes, and probable Quaternary fissureeruptive sheets crop out. This arch is separated by
the narrow, northeast trending Muria Basin (West
Florence Deep) from the Bawean Arch. The Bawean
Arch is characterised by alkaline volcanism of the
latest Neogene or Quaternary and steeply dipping
Miocene marine strata (van Bemmelen, 1949).
DATA
The data base for this study is drawn from seismic
profiles of about 3750 line km in the Java Sea
(Figure 2). All geophysical data were obtained from
the Marine Geological Institute of Indonesia which
ran the survey in 1989/1990. The seismic system
used is a single channel 600 Joule sparker system,
fired every 1 second. These setting have allowed of
about 400 milliseconds penetration below the
seabed. The seismic signals were not tape recorded,
but were directly band pass filtered (200-2000 Hz)
and graphically recorded in analog format during
the survey. Due to this technique, no further data
processing was carried out. The ship positions
during the survey relied mostly on GPS navigation
system, and by the time the acquisition was
conducted, the horizontal accuracy was not less
than 100m. The profiles were mostly oriented northsouth and spaced 5 to 10 km apart.
Stratigraphic control for calibration of the seismic
data was provided by six petroleum exploratory
wells, JS1-1, JS2-1, JS3-1, JS8-1, JS10-1 and
JS16-1. However, these data cannot provide a
reliable stratigraphic timing resolution as the
biostratigraphic and lithofacies analyses done were
based on well cuttings which were commonly
sampled every 30 ft penetration. Even so, they have
narrowed the age estimation of the stratigraphic
time markers.
SEISMIC STRATIGRAPHY
Seismic analysis indicates that the Late Tertiary
and Quaternary sediments in the study area can be
subdivided into three major seismic units. These
units correspond to the Miocene, Pliocene and
Quaternary and are referred to as Units 1, 2 and 3
respectively.
Page 6 of 34
Figure 2. Tracklines of single channel sparker seismic records used in this study superimposed on the
bathymetric map of the study area. Thicker lines are parts of seismic lines presented in this paper for
discussion. Dots in the Java Sea represent the oil exploration wells.
Unit 1
This Miocene unit can only be observed on the
structurally high areas, such as near the Bawean
and Karimunjawa Arches, and on Madura Island.
The age of Unit 1 is confirmed by well data of JS8-1
and JS3-1. The internal seismic reflection patterns
and areal distribution are poorly defined,
particularly because of the limited penetration of
the seismic system used and strong multiple
reflections. The lower boundary is unidentifiable,
but the upper boundary is a regional unconformity
as shown by a pronounced erosional surface on the
structurally high areas (Figures 3, 4, 5 and 6). On
most of seismic sections, Unit 1 is characterised by
a
medium
amplitude,
continuous
parallelsubparallel
reflection
pattern
of
possibly
interbedded sandstone and mudstone (Figures 3, 4
and 5). The sections acquired near the
Karimunjawa and Bawean Arches suggest that the
lower part of Unit 1 is probably equivalent to the
Miocene strata exposed on these islands, which are
characterised by the occurrence of limonitic
sandstone, interbedded with lignite, marl and
crystalline limestone (Bemmelen, 1949). A mounded
structure characterised by low amplitude of internal
reflectors is observed on the top of Unit 1, and
probably represent a highstand reef (Figure 6).
Unit 2
Unit 2 is relatively thick and was deposited
following sea level fall at the end of the Miocene. It
consists of two subunits: 2a and 2b, with subunit
2a forming the major part of the sequence.
Correlation between the seismic and the
micropalaeontological data from some petroleum
exploratory wells confirmed that this unit developed
during the Pliocene. The top boundary of Unit 2 is
an erosional surface marking extensive subaerial
exposure in the study area. Based on reflection
configuration patterns, the sediment sources of
these subunits were mainly the Karimunjawa and
Bawean Arches in the western half of the study
area. In the eastern half, the deposits were sourced
from both the Bawean Arch and Madura Island, but
the
distribution
was
complicated
by
the
development of folds.
On the stable area, such as on the Karimunjawa
Arch, the Pliocene unit was thinly deposited on top
of the Miocene unit which suggests that the
subsidence rate on the arch was very low. The
seismic characters are mainly form a strong
amplitude parallel reflection pattern (Figure 3)
which is often associated with mounded forms of
possibly reefal limestone. In the areas where the
depositional slope was high, such as near the
margins of the Muria Trough, the East Bawean
Trough and the growing Madura Island, the
deposition of the lower part of Unit 2 may be divided
into two main systems tracts: the lowstand and
highstand systems tracts (Figures 5 and 6).
Page 7 of 34
Figure 3. Seismic line JA from east of the Karimunjawa Islands which comprises a stable area of the
Karimunjawa Arch. Pliocene and Quaternary units are thin and nearly flat due to slow subsidence and low
depositional slope.
Page 8 of 34
Figure 4. Seismic line JD which represents southeast margin of the Bawean Arch. A thicker succession of the
Miocene units shows stronger parallel reflection amplitudes, indicative of a shoaling upward sequence. The wedge
shaped Unit 2 indicates a southward increase of subsidence, which may lessened by the end of Pliocene.
Page 9 of 34
Figure 5. Seismic line JCN from southwestern slope of the Bawean Arch. The arch was exposed subaerially
following highstand reef deposition in the Late Miocene. The pronounced prograding complex on the flank of
the arch represents the major highstand deposition in the Pliocene. A major channel observed on top of
subunit 3d may result from the last glacial sea level lowstand.
Page 10 of 34
Figure 6. Seismic line JI from northern flank of Madura Island. The continuous growth of the island has resulted
in a pronounced northward progradation of the lowstand and highstand systems tracts in the Pliocene and Early
Quaternary. Such conditions may extend towards the northern coast of Java in the study area.
Page 11 of 34
The transgressive systems tract on most of the
seismic lines studied is absent or unidentified,
probably due to a rapid sea level rise which did not
permit formation of a seismically resolvable
transgressive unit.
In the western part of the study area, the upper
part of Unit 2 is recognised as a thin prograding
complex downlapping onto the erosional surface at
the top of Unit 2a (Figure 7). This erosional surface
should be correlated with a lowstand of sea level
and the prograding complex with the highstand
deposits. On the flank of Madura Island a thicker
unit was deposited, which may be resolved into
lowstand and highstand deposits (Figure 6).
Figure 9 shows palaeogeographic maps during the
lowstand period of subunit 2a. These maps indicate
that the Pliocene basin in the western half of the
study area was still influenced by the normal fault
movement of the half graben system in the Muria
Trough. The occurrence of the deepest basin and
accumulation of the thickest Pliocene sediments in
this trough (particularly along the normal faults)
has further suggested probable faster subsidence
and sedimentation rates. In the eastern half of the
area, the influence of the previous structural
configuration (Figure 3) is not obvious. The Pliocene
structural development (east-west trending folds)
had more influence on the sedimentation
particularly in the area between Java and Bawean
Islands and near the Madura Island, as indicated by
the trends of basin morphology and the Pliocene
sediment accumulation (Figure 8).
Unit 3
Unit 3 was deposited following a sea level fall which
exposed the whole study area at the end of the
Pliocene. The seismic characters and sedimentation
patterns of Unit 3 differ significantly from those of
the preceding Unit 2. They appear to be strongly
influenced by extreme and rapid sea level
fluctuations.
Such
fluctuations
during
the
Quaternary have been demonstrated by many
workers through the oxygen isotope records of deep
sea cores, which they have related with the
orbitally-induced fluctuations of global ice volume.
These glacio-eustatic sea level fluctuations are
particularly apparent since 0.97 Ma (Harland et al.,
1989) with a relatively constant period. The global
sea level falls may have reached 130 m below
present level during the glacial maximum (Bloom et
al., 1974; Chappell & Shackleton, 1986; Fairbanks,
1989).
The present seismic study identified five main
Quaternary seismic subunits in the area. These
subunits are characterised mostly by parallel to
subparallel reflection patterns or are reflection free.
Each of them ended with channel cut and fill along
their upper part and are interpreted to represent
marine
deposition
and
fluvial
channelling
respectively. In some areas the thickness of these
subunits appears to be similar, which may indicate
constant subsidence rates combined with periods of
sea level fluctuation. Because these subunits have a
similar seismic character and do not represent thick
deposits, lateral correlation is difficult and tends to
be speculative. But they can be grouped into five
subunits, 3a to 3e, based on the occurrence of
widespread unconformities on top of each unit.
These unconformities are commonly associated with
rather deep and wide fluvial channelling.
a. Subunits 3a and 3b
The subunits 3a and 3b were deposited during the
Early Pleistocene, based on their stratigraphic
position overlying Pliocene Unit 2. A stratigraphic
subdivision between these subunits in the western
part of the study area is rather speculative, but
clear differentiation can be made in the areas near
the Java and Madura Islands due to the higher
subsidence rate and the occurrence of a relatively
large sea level fall at the end of subunit 3a
deposition (Figures 6 and 7). Seismic features, such
as rapid basinward thinning (Figure 6) and
pronounced anticlines (Figure 7) indicate that their
distribution was influenced by local structural
development. There, subunit 3a can be further
subdivided into subunits 3a-1 and 3a-2 based on
the occurrence of an internal erosional surface
(Figure 7). The thickness of subunit 3a-1 reaches
100 msec TWT (about 75 m) in the deepest portion
of the basin, and it gradually thins toward the basin
margin. The maximum thickness of subunit 3a-2 is
about 60 msec TWT (about 45 m). The thickness
variation is mainly due to local subsidence, post
depositional erosion and a gradual thinning
because of the rising of the basin margin. Subunit
3a-2 onlaps on subunit 3a-1 on the southern
margin, and on Unit 2 when subunit 3a-1 wedges
out. The seismic character of these subunits is
similar, a subparallel reflection pattern with
medium amplitude and medium continuity which
suggests
deposition
in
a
shallow
marine
environment (Sangree & Widmier, 1977). To the
north of Madura Island a local deepening occurred
(Fig. 6), and subunits 3a-1 and 3a-2 are
characterised by northward prograding clinoform
deposits, indicating that the sediments were derived
from the growing Madura Island. Subunits 3a-1 and
3a-2 may be regarded as the units responsible for
the flatness of this area.
The subunit 3b was deposited on a flat surface and
has an extensive coverage although its thickness is
less than 35 msec TWT (26 m). Seismically, this
subunit is characterised by a similar appearance to
subunits 3a-1 and 3a-2, and probably was
deposited in a similar environment. The upper part
tends to show subparallel to hummocky patterns
with variable amplitude which indicates a shoaling
(regression) of the unit before finally being exposed
subaerially.
b. Subunits 3c, 3d and 3e
Subunits 3c and 3d can further be subdivided into
three (3c-1, 3c-2 and 3c-3) and two (3d-1 and 3d-2)
respectively.
Page 12 of 34
Figure 7. Seismic line JCS from the north of east Java which represents an area with high subsidence and
depositional rates. Local structures observed lie in an E-W direction and are controlled lateral distributions of the Late
Pliocene and Early Quaternary subunits.
Page 13 of 34
Figure 8. Palaeogeographic map during the deposition of lowstand systems tract Subunit 2a (Early Pliocene),
plotted on the time structure contours (in mSec. TWT) at top Miocene.
Page 14 of 34
These subdivisions can only be recognised in a
limited
area
where
the
subsidence
and
sedimentation rates were relatively high, such as in
the area just north of Java (Figure 7).
Subunits 3c-1 and 3c-2 are similar in seismic
character,
showing
a
medium
amplitude,
subparallel reflection pattern which probably
represents a shallow marine environment. Subunit
3c-3 is reflection free, indicating most probably
homogeneous mudstone. Subunit 3d is extensively
distributed and in some areas is characterised by
an almost reflection free character suggesting a
nearly homogeneous deposit probably of mudstone.
In the western part, subunits 3d-1 and 3d-2are very
thin to absent, which indicates a low depositional
rate.
Subunit 3e consists of a single reflection-free
sequence of possibly homogeneous mudstone. The
maximum thickness in the basinal area is about 30
msec TWT (about 22 m) with a little variation on the
western part of the study area. On some parts to
the north of Madura Island this subunit is too thin
to be identified, but locally thick deposits of up to
25 msec TWT (about 19 m) occur in a limited area,
particularly near the river mouths on the northern
coast of Java. The fluvial channelling at the base of
subunit 3e in some areas is very pronounced
(Figure 6). Its occurrence can be related to the last
glacial period, during the oxygen isotope stage 6,
when the sea level was -130 m below present level
(Chappell & Shackleton, 1986).
DISCUSSION AND CONCLUSION
The Miocene basin configuration of the study area
is poorly known, but it is suspected that the basin
development was still strongly influenced by the
northeast-trending structures related to the
basement configuration. These structures are half
grabens and have been the major control for the
Early Tertiary sedimentation. Although some
elements of these structures were still active until
the Pleistocene, their effectiveness in controlling the
sedimentation during the post-Miocene was
diminished. The Pliocene sedimentation, in general,
occurred in E-W trending synclinal basins which
indicate the dominance of the northward tectonic
compressional stress. This continued until the Early
Pleistocene, as is indicated by some local thickening
of the Early Pleistocene deposits. Since then,
further basin development appears to have ceased,
and a tectonically stable condition may have been
reached.
The Quaternary units, which are represented by
nine thin subunits, tend to be distributed widely
because of deposition on a relatively flat lying area.
The seismic characters are very similar, comprising
subparallel reflection or almost reflection free
patterns at the bottom which represent marine
deposits, topped by extensive fluvial channelling.
This repetitive succession is thought to represent
highstand and lowstand periods of sea level
respectively. Because the average water depth in the
study area is about 60 m, the fluvial channelling
may be correlated with the major sea level lows
during the Quaternary. The bases of subunits 3e,
3d and 3c are tentatively correlated with the glacial
periods during oxygen isotope stages 2, 6 and 16 of
Harland et al. (1989) respectively, while subunits 3a
and 3b represent earlier periods. During the glacial
periods the Sunda Shelf became widely exposed,
and river systems such as the Molengraaff river
(Molengraaff, 1921; Kuenen, 1950; Voris, 2000)
may have developed in the last glacial period.
ACKNOWLEDGEMENTS
The authors wish to thank the Head of the Marine
Geological Institute of Indonesia for permission to
use the data. This paper is part of the first author’s
PhD thesis supervised by Dr. Leonie Jones, Prof.
Colin Murray-Wallace and Prof. Brian G. Jones.
Therefore,
their
supervision,
support
and
contribution are greatly acknowledged.
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Page 16 of 34
Merits and Shortcomings of Heat Flow Estimates from
Bottom Simulating Reflectors
Minarwan and Rahmat Utomo
Mubadala Petroleum (Thailand) Ltd, Bangkok, Thailand
Corresponding author: [email protected]
ABSTRACT
The presence of gas hydrates in deep marine sediments and their Bottom Simulating Reflectors
(BSRs) on seismic lines can be used to estimate present-day surface heat flow. Despite its limited
accuracy, the estimated heat flow is still useful as an input in thermal maturity modeling of a
frontier basin.
BSRs commonly occur at several hundred meters below the seafloor, in low latitudes generally in
areas with water depth greater than about 700-1000m. They run parallel to the sea floor and may
cross-cut lithological boundaries. They represent a phase boundary between a gas-hydrates-stable
zone and underlying free gas- and water-saturated sediments. Since the depth of the hydrate- free
gas phase change is a function of temperature, depth (pressure) and gas composition for a given
gas composition (assuming hydrostatic pressure and mainly methane gas), the temperature
gradient between seafloor and the BSR can be calculated from its depth. The temperature gradient
can then be converted into heat flow, provided that thermal conductivity of the sediment is known.
Keywords: heat flow, gas hydrates, bottom-simulating reflectors.
INTRODUCTION
Modeling source rock maturity in a basin requires
reliable thermal calibration, ideally by using
vitrinite reflectance data or other maturity
indicators. It is also important to calibrate the
present-day heat flow or geothermal gradient used
in the modeling against the present-day thermal
condition, which can be done by using
temperature gradient data from wells or direct heat
flow measurements. If vitrinite reflectance or other
thermal indicators are not available, then the
minimum pre-requisite would be to find the
present-day geothermal gradient and/or heat flow
data in order to predict the current level of thermal
maturity. As a temperature model forms an
important part of source rock maturity modeling,
maximum efforts have to be made in order to get
the most representative temperature input.
In a frontier deepwater basin with a good coverage
of seismic data and where gas hydrates are
present, heat flow can be estimated by deriving
temperature of the phase change in relation to the
gas hydrate system. The method for estimating
heat flow from marine gas hydrates was introduced
by Yamano et al. (1982) and to date, it has been
applied in many regions including Sebakor Sea,
Irian Jaya, Indonesia (Hardjono et al., 1998),
Kerala-Konkan, India (Shankar et al., 2004),
Caribbean offshore Colombia (López and Ojeda,
2006), offshore Southwest Taiwan (Shyu et al.,
2006), Gulf of Cadiz, Spain (León et al., 2009),
Simeulue fore-arc basin, Indonesia (Lutz et al.,
2011) and the Andaman Sea (Shankar and Riedel,
2013; Shankar et al., 2014).
Despite its usefulness, calculated heat flow from
BSRs can be inaccurate and show some disparities
with measured heat flow as reported by Kaul et al.
(2000) and He et al. (2009). This paper reviews
advantages and shortcomings of BSR heat flow
based on personal experience and some published
materials. We present the methods to derive heat
flow from BSRs, within the context of Indonesian
sea waters, and provide suggestions on how to use
them as inputs in thermal maturity modeling. We
will also review potential errors associated with
parameter assumption and theoretical errors as
shown by previous publications.
GAS
HYDRATES
AND
SIMULATING REFLECTION (BSR)
BOTTOM
Gas hydrates are ice-like crystalline solids formed
from water and gases (mostly CH4) under low
temperature and moderate to high pressure
conditions. They can be present in an area where
abundant supply of methane exists in the system.
Their stability is controlled by methane solubility
(the required minimum methane concentration)
and a three-phase equilibrium curve of CH4hydrates-water (e.g. Kvenvolden, 1988; Davie et
al., 2004—Figure 1).
Page 17 of 34
Figure 1. P-T diagram of gas hydrate stability
based on a three-phase equilibrium curve (after
Davie et al., 2004). Solid squares are P-T at the
base of natural GHSZ drilled by Ocean Drilling
Program, which show good correlation with
experimental three-phase P-T curve (sea water).
Figure 2. Gas hydrate stability zone in marine
environment is located between sediment-water
interface and the intersection of geothermal
gradient and the CH4-hydrates-water equilibrium
curve (Dickens and Quinby-Hunt, 1997). Graphic is
from Davie et al. (2004).
In cold or deep marine environments, gas hydrates
are stable between the sediment-water interface
and the intersection of the geothermal gradient
with a CH4-hydrates-water equilibrium curve
(Dickens and Quinby-Hunt, 1997—Figure 2).
accumulation of methane hydrates in marine
sediments. The most relevant points from their
work regarding gas hydrate & BSR are: (1) the base
of the zone where actual gas hydrates occur is not
always at the base of GHSZ, but rather lies at
shallower depth than the base of the stability zone;
(2) If the BSR marks the top of the free gas zone,
then it will occur substantially deeper than the
base of the stability zones in some settings and (3)
the presence of methane within the pressuretemperature stability field for methane gas
hydrates is not sufficient for gas hydrates to occur.
Gas hydrates “can only form if the mass fraction of
methane dissolved in liquid exceeds methane
solubility in seawater and if the methane flux
exceeds a critical value corresponding to the rate of
diffusive methane transport”. Figure 3 illustrates
the relationship between tops and bottoms of
actual gas hydrate, hydrate stability zone and top
of free gas according to the model developed by Xu
& Ruppel (1999).
Initial research on methane gas hydrates
occurrence in marine sediments inferred that the
base of Gas Hydrates Stability Zone (GHSZ) or
Methane Hydrates Stability Zone (MHSZ), which
represents the phase boundary from marine
sediments containing solid gas hydrates to those
containing only water and free gas, is frequently
imaged on seismic sections as a high amplitude
reflection that mimics the seafloor and cross-cuts
reflections of sedimentary layers. The reflection is
called a Bottom-Simulating Reflection (BSR) and it
always shows reverse polarity from that of the
seafloor, due to the decrease in velocity and
density across the boundary (Yamano et al., 1982).
The BSR is distinguishable from seafloor multiples
as the multiples occur at twice the two-way time
(TWT) between sea surface and seafloor. A BSR can
be present at depths of 100 to 1100 m below the
seafloor (Collett, 2002) and the thickness of gas
hydrates is usually 220–400 m (León et al., 2009).
Following Ocean Drilling Program (ODP) Leg 164 in
late 1995, Xu and Ruppel (1999) developed a
better analytical formula to explain evolution and
ESTIMATING HEAT FLOW FROM THE BSR
The commonly accepted method to estimate heat
flow from gas hydrates requires the geothermal
gradient from the seafloor to the base of the GHSZ
(note: main assumption here is the BSR marks the
base of GHSZ and also the top free gas) and
thermal conductivity of the sediments where the
Page 18 of 34
Figure 3. Possible location of BSR and its relationship to the base of Gas Hydrate Stability Zone
(GHSZ)/Methane Hydrate Stability Zone (MHSZ). BSRG1 is the estimated thermal gradient if the BSR
represents the base of Methane Hydrate Zone (this will give higher BSR heat flow than the measured
heat flow). BSRG2 is the estimated thermal gradient if the BSR represents the top of free gas zone (this
will give lower BSR heat flow). Graphic is from He et al. (2009), based on the model developed by Xu &
Ruppel (1999).
gas hydrates are present. The geothermal gradient
can be calculated if temperatures and depths of
the BSR and the seafloor are known. The simplest
approach would be to relate temperature (T) and
depth (Z) at the base of the GHSZ as a function
[T=f(Z)] because Z is the first variable that can be
estimated by using seismic and bathymetric data.
However, as the stability of the gas hydrate phase
is determined by temperature (T) and pressure (P),
then another function [P=f(Z)] correlating P and Z
has to be known first.
The BSR heat flow is estimated by using the
following equation (e.g. Shankar and Riedel, 2013):
equals hydrostatic pressure (León et al., 2009) and
therefore, P in Equation (1) can be calculated from
this equation:
Qbsr = 1000 x k x [(Tbsr - Tsea)/(Zbsr - Zsea)] (1)
where Qbsr is BSR heat flow (in mW/m2), k is the
thermal conductivity of marine sediments (in
W/mK), Tbsr (K) is the temperature at the depth of
BSR (Zbsr) and Tsea is the temperature at the
seafloor (Zsea).
The temperature at the BSR (Tbsr) is estimated by
using the published empirical equation from
Dickens and Quinby-Hunt (1994), which relates
pressure to temperature of methane hydrate
disassociation in a laboratory experiment by using
seawater (salinity of 33.5 ppt). For any given
pressure between 2.5–10 MPa, their experiment
shows that P and T follow this equation:
1/Tbsr = 3.79 x 10-3 – [2.83 x 10-4 x log(P)]
(2)
where Tbsr is temperature (K) and P is pressure
(MPa).
Assuming pore-waters are connected and there is
no overpressure in the system, then pore pressure
P = ρ x g x Zbsr
(3)
where P is pressure at depth (MPa), ρ is density of
water (kg/m3), g is gravity acceleration (9.81 m/s2)
and Zbsr is depth of the BSR (m subsea).
The density of seawater can be estimated by
assuming constant salinity and sea surface
temperature for practicality. The salinity and sea
surface temperature data can be taken from the
World Ocean Atlas (2013), which can be accessed
online at US National Oceanic & Atmospheric
Administration (NOAA) website. As an example, the
average salinity and surface temperature of
Indonesian seawater are 33.5 ppt and 28.4 C,
respectively (World Ocean Atlas, 2013). Using
these numbers, the density of Indonesian seawater
would be 1021.182 kg/m3 (Millero et al, 1980). If
this value is used in Equation (3) then the
equation becomes:
P = 0.010017795 x Zbsr
(4)
Page 19 of 34
The Zbsr is calculated by converting Two-Way-Time
(t) from seismic into depth. The depth conversion
can be done by using the following steps
(assuming constant seismic velocity in seawater of
1500 m/s):
Zbsr = Zsea + Dbsr
Zsea = 1500 (1⁄2 tsea)
(5)
(6)
Equations (7) and (8) are taken from Equations (1)
& (2) of He et al. (2009), which were used to
estimate depth for the upper 1s seafloor sediments
in the Xisha Trough and Northern South China
Sea.
Dbsr = 982.576 (tbsr – tsea); if (tbsr – tsea) ≤ 0.5s (7)
or
Dbsr = 121.52 (tbsr – tsea)2 + 1269.1 (tbsr – tsea) –
173.692; if 1s ≥ (tbsr – tsea) > 0.5s
(8)
where Dbsr is thickness of the BSR (m from
seafloor), tsea and tbsr are TWT of the sea floor and
the BSR, respectively, from seismic datum (sea
level) in seconds.
The Dbsr can also be estimated from depth
conversion by using a constant interval velocity for
the upper 1km of marine sediments. For examples,
Yamano et al. (1982) used 1.85±0.05 km/s in the
Nankai Trough, Japan; Davis et al. (1990) used
2000 m/s in the Northern Cascadia margin; while
in the Simeulue fore-arc basin the interval velocity
may range from 1900 m/s to 2200 m/s (Franke et
al., 2008).
After solving Equation (4), the calculated pressure
can be used to solve Equation (2) and this gives
the temperature of the BSR (Tbsr). The seafloor
temperature (Tsea in K) ideally should be taken
from in situ measurement, however in the absence
of CTD (Conductivity-Temperature-Depth) and
Expandable Bathythermograph (XBT), Tsea can be
estimated from the World Ocean Atlas (2013)
dataset, providing representative data points are
available. Otherwise, another way to get seafloor
temperature is by adopting an equation used by
Shankar and Riedel (2013) in the Andaman Sea:
Tsea = 278.645 – (0.0002 x Zsea)
(9)
The equation above was based on in situ
measurements and published data near Little
Andaman Island, which is relatively close to
Indonesia region. It must be noted that seafloor
temperature can be affected by deep current flow,
therefore it is possible to get different temperatures
from different measurements throughout the year.
The seafloor temperatures generated by the two
methods mentioned above can differ by approx. 1
C, hence creating some uncertainties on
estimated heat flow (see next section).
The last parameter to be estimated before
calculating heat flow from the BSR is the thermal
conductivity (k) of marine sediments. Davis et al.
(1990) suggested an empirical solution that gives
average thermal conductivity of sediments starting
from the sea floor as follows:
k = 1.07 + (5.86 x 10-4) x Dbsr – (3.24 x 10-7) x Dbsr2
(10)
where k is thermal conductivity of sediments (W/m
K) and Dbsr is the thickness below the sea floor (m).
This equation in general is consistent with
measured thermal conductivity in the Xisha
Trough (He et al., 2009). The measured thermal
conductivity of marine sediments actually can
range pretty wide, for examples 1.1–1.8 W/m K (0–
3 m bsf) in the Makran accretionary prism,
offshore Pakistan (Kaul et al., 2000) and 1.0–1.4
W/m K (0–300 m bsf) in the Cascadia margin
(Ganguly et al, 2000). However the average thermal
conductivity of marine sediments can also be
assumed to be approx. 1.2 W/m K (Davis et al.,
1990) to 1.27 W/m K (Kaul et al., 2000).
ADVANTAGES AND SHORTCOMINGS
Advantages
In a frontier basin where no prior hydrocarbon
exploration activities have taken place and no
present-day heat flow measurements are available,
BSR heat flow estimates are useful as a presentday heat flow input in basin modeling. Having a
favorable thermal maturity model of a basin would
support a decision of whether or not to explore for
conventional hydrocarbon in a frontier area. The
method is considerably less expensive and more
practical than acquiring heat flow data directly
through heat flow probes, because BSR can be
identified even from regional 2D seismic lines and
calculations of heat flow values can be done
quickly by using publicly available parameter
assumptions. If BSR's occur in many regional
seismic lines across a basin, then more heat flow
values can be derived and variation of these values
can be taken into consideration to get appropriate
thermal maturity model(s).
Shortcomings
As previously explained in the methodology to
derive heat flow from the BSR, various levels of
assumptions and simplification must be applied,
due to either lack of data or naturally insufficient
empirical solution to constrain physical and
chemical properties of the required input
parameters. The assumptions and simplifications
may eventually lead to inaccurate BSR heat flow,
which may show large variation and even
disparities to measured heat flow values.
Another limitation of using BSR to estimate heat
flow is related to the Tbsr-Pressure relationship
(Equation 2) and the sea floor temperature
(Equation 9) that are best-applied in the deepwater
setting (WD > 750m). Using these equations for
shallow water setting can give Tsea > Tbsr, hence
giving negative heat flow values.
Page 20 of 34
BSR Heat Flow Variation
It is common to get a large variation of heat flow
when they are derived from the BSR in a basin.
The following examples demonstrate how wide the
range can be:
 36–90 mW/m2 (average 60.8 mW/m2) in one
Indonesian basin (unpublished)
 34.8–59.9 mW/m2 (average 47.7 mW/m2) in the
Sebakor Sea, Irian Jaya (Hardjono et al., 1998)
 32–80 mW/m2 in the Xisha Trough (He et al.,
2009)
 37–74 mW/m2 in the Simeulue fore-arc basin
(Lutz et al., 2011), and
 12–41.5 mW/m2 in the Andaman Sea (Shankar
and Riedel, 2013).
In some cases, heat flow variation follows both
regional and local trends. For example on the
northern Cascadia margin, Canada, the regional
BSR heat flow increase towards the deformation
front, which is consistent with the trend shown by
heat flow probe, and locally, they are low over
topographic highs and high over the flanks of the
highs (Figure 4; Ganguly et al., 2000]. Similar
regional BSR heat flow behavior has also been
seen by Kaul et al. (2000) in the Makran
accretionary prism offshore Pakistan. This large
variation of heat flow values could be controlled by
active geological process such as proximity to
active deformation front and effects of rapid
sedimentation, but could also be due to poor
control of subsurface velocity variation. Local heat
flow variation may be caused by dynamic effects
such as upward migration of warm fluids along
permeable faults and the displacement of isotherm
by thrust faulting (Ganguly et al., 2000).
Figure 4. Local variation of BSR heat flow in the Cascadia Margin, Canada, showing low heat
flow values on the topographic highs and high heat flow on the flank (Ganguly et al., 2000).
Page 21 of 34
Disparities between BSR and Measured Heat
Flow
Disparities between BSR-derived and measured
heat flow were reported by Kaul et al. (2000) in the
Makran accretionary prism and He et al. (2009) in
the Xisha Trough, South China Sea. In the Makran
accretionary prism, the BSR heat flow values are
consistently higher than the measured heat flow
by about 15 to 25 mW/m2. The discrepancies were
attributed to high sedimentation rate and tectonic
uplift that led to the upward migration of gas
hydrate stability zone (as gas hydrates are
dissolved at the base of the GHSZ).
In the Xisha Trough, the BSR heat flow values are
32–80 mW/m2 and are significantly lower than the
measured values of 83–112 mW/m2. He et al.
(2009) argued that the disparities are caused by
theoretical errors rather than parameter errors
because the discrepancies are larger than a change
in the input parameters would have contributed to.
They estimated that the parameter errors would
have affected the BSR heat flow by only less than
25%,
while
their
calculations
indicate
discrepancies of up to 50% in some geological
settings.
Source of Error and Implications to BSR Heat
Flow
Uncertainties in Input Parameter Assumptions
The first source of errors in BSR heat flow
estimation is due to uncertainties in input
parameter
assumptions,
particularly
from
subsurface velocity (for time-depth conversion),
seafloor temperature, thermal conductivity and gas
composition. Tables 1 and 2 show the sensitivity of
various input parameters changes to the estimated
heat flow. Assuming all other parameters are
similar, an increase in the interval seismic velocity
by 10% would increase the estimated heat flow by
around 8-9%, while a decrease of 10% would make
the calculated heat flow lower by around 6–7%
(Table 1). A variation in seafloor temperature of 1
ºC lower or higher would contribute to the increase
or decrease of estimated heat flow by ±6-10%,
respectively (Table 2, columns 2 & 3).
A change in thermal conductivity by 0.1 W/mK
(Table 2, columns 4 and 5) correlates to a change
in the estimated heat flow by ±8-9%. As the
thermal conductivity may range from 1.0 to 1.4
W/m K for the first 300 m of sediments below the
seafloor (Ganguly et al., 2000), then the estimated
heat flow can vary by 18% colder for lower thermal
conductivity and 15% hotter for higher thermal
conductivity (Table 2, columns 6 and 7). At some
circumstances, when the TWT thickness between
the BSR and the seafloor is within the range of
0.5–1.0 s, a thermal conductivity of 1.0 W/m K
can lead to approximately 24% colder heat flow
(Table 2, column 6 Case 2). The thermal
conductivity may also vary spatially depending on
sediment types, therefore using a single thermal
conductivity for every calculation is not perfect.
The biggest uncertainty is the gas composition,
because the general assumption is that gas in
hydrates is pure methane (CH4). León et al. (2009)
showed that if the gas is thermogenic (i.e. contains
C2 to C5), for any given depth between 2000 and
3000 m, the T at the base of the GHSZ will be 5 ºC
higher than that of biogenic methane hydrates,
which means the estimated heat flow will be hotter
by approximately 29 to 35%.
Geological Phenomenon
Examples of the geological phenomenon that can
influence heat flow near the seafloor is the
thickening of sediment wedge towards the
coastline from the deformation front of a
subduction zone (e.g. Northern Cascadia, Canada
and Makran accretionary prism, Pakistan) and
upward migration of warm fluid through
permeable faults or due to rapid dewatering
process when sediments are compacting. Wang et
al. (1993) modeled that heat reduction due to the
thickening of sediment wedge is more significant
than the heat increase caused by the upwardmigrating fluid expulsion, which consequently
significantly can depress the seafloor heat flow to
become lower than the deep lithospheric heat flow.
Theoretical Errors
The model involving a critical value of methane
flux to exceed methane solubility in seawater,
necessary for methane hydrates to form, was
developed by Xu and Ruppel (1999) to explain
natural occurrence gas hydrates and its
relationship to the BSRs on the Blake Ridge
(offshore southeast US). Their work demonstrates
that the base of GHSZ (MHSZ) does not necessarily
coincide with a BSR and in some geological
settings the BSRs can represent the base of the
actual methane hydrates or the top of the free gas
zone. The meaning of ‘some geological settings’
here is those with different combination of water
depth, regional heat flow and available mass
fraction of methane. In some settings, if the BSR
represents the base of methane hydrate zone
(shallower than the base of the stability zone), then
the BSR heat flow will be higher than the regional
heat flow. However, if the BSR represents the top
of free gas zone, then the BSR heat flow will be
lower (see Figure 3). The latter case was proposed
by He et al. (1999) as the reason for the much
lower BSR heat flow in the Xisha Trough, South
China Sea. The disparities were caused by an
oversimplification of the BSR as the base of the
GHSZ (MHSZ) in every setting. This is a potential
error in the theoretical assumption of BSR heat
flow calculation and can only be solved when heat
flow probes or direct drilling data are available.
Page 22 of 34
against frequency and suitable range
to identify where the heat values are
concentrated;
2.
Compare the results with
published present-day heat flow at
the surface of the Earth's crust
(Global Heat Flow Database of the
International Heat Flow Commission,
Figure 5; Pollack et al., 1993), or for
SE Asia and Indonesia region
compare with the published heat
flow data compilation from Smyth
(2010).
3.
Build low, expected and high
case heat flow models that are
sensible to present-day heat flow
values as guided by global database
and also tectonic setting of the
basin. Currie and Hyndman (2006)
observed that the typical heat flow
for fore arc basins is approx. 40
mW/m2, while for Indonesian back
arc basins it is 76±18 mW/m2.
CONCLUSIONS
The method of deriving heat flow
from BSRs, despite not being new
and highly accurate, is still useful to
evaluate hydrocarbon potential of a
frontier region. It can give significant
input for making a quick decision in
evaluating a new area with limited
information. The method can be
applied to any frontier basin where
gas hydrates are present, providing
the assumptions to derive the heat
flow are appropriate
to local
conditions.
Table 1. Sensitivity of average seismic velocity
changes to estimated BSR heat flow. The 'Base
case' Dbsr was calculated by using Equations (7)
& (8) for Case 1 and Case 2, respectively. The
Dbsr in other cases was calculated from assumed
single seismic velocity in marine sediments.
USING BSR HEAT FLOW IN THERMAL
MATURITY MODELLING
We suggest the following steps to capture
uncertainty generated by large variation of
calculated BSR heat flow when they are used as
inputs in a thermal maturity modeling:
1.
Apply a simple statistical analysis to get
arithmetic mean and standard deviation. Check
Input parameter assumptions are a
source of uncertainties in estimating
heat flow by using the BSR method.
Parameters that are sensitive to the
resultant heat flow estimation include gas
composition
(29-35%),
thermal
conductivity
(±17%), depth conversion (±8%) and seafloor
temperature (6-10% for 1 ºC change). In order to
reduce uncertainties and to get a more accurate
estimation, it is important to use real
measurements as much as possible, however when
real data are not available, then care should be
taken when making assumptions for those four
components. Another source of error is the
possibly erroneous assumption of the BSR as the
base of GHSZ (MHSZ) in all settings, leading to
disparities between BSR-derived and directly
measured heat flow. This theoretical error can only
be solved when real measurements or drilling data
are available.
Page 23 of 34
Table 2.
Sensitivity of
seafloor
temperature
and thermal
conductivity
changes to
estimated
BSR heat
flow. Columns
(6) and (7) are
for assumed
average
thermal
conductivity
(see text for
more
explanation).
Figure 5.
Present-day
heat flow at
the surface of
the Earth's
crust (Global
Heat Flow
Database of
International
Heat Flow
Commission)
as compiled
by Pollack et
al. (1993).
Page 24 of 34
As the BSR heat flow results cover a wide range, it
is advisable to use statistical analysis prior to
using the estimated heat flow as inputs in a
thermal maturity modeling. It is also important to
compare the estimation results with the global
heat flow database because the database has been
compiled from direct heat flow measurements.
ACKNOWLEDGEMENTS
We would like to thank Dr. J.T. van Gorsel and Dr.
Udrekh Al Hanif for their comments and
corrections that helped to improve this article.
REFERENCES
Collett, T. S., 2002, Energy resources potential of
natural gas hydrates: AAPG Bulletin, 86
(11), p. 1971–1992.
Currie, C. A. and R. D. Hyndman, 2006, The
thermal structure of subduction zone back
arcs: J. Geophysical Research, 111, B08404,
doi:10.1029/2005JB004024, 22p..
Davie, M. K., O. Y. Zatsepina, and B. A. Buffett,
2004, Methane solubility in marine hydrates
environments: Marine Geology, 203, p. 177–
184.
Davis, E. E., R. D. Hyndman, and H. Villinger,
1990, Rates of fluid expulsion across the
Northern Cascadia accretionary prism:
Constraints from new heat flow and
multichannel seismic reflection data: J.
Geophysical Research, 95 (B6), p. 8869–
8889.
Dickens, G. R. and M. S. Quinby-Hunt, 1994,
Methane hydrate stability in seawater:
Geophysical Research Letters, 21 (19), p.
2115–2118.
Dickens, G. R. and M. S. Quinby-Hunt, 1997,
Methane hydrate stability in pore water: A
simple theoretical approach for geophysical
applications: J. Geophysical Research, 102
(B1), p. 773–783.
Franke, D., M. Schnabel, S. Ladage, D. R. Tappin,
S. Neben, Y. S. Djajadihardja, C. Mueller, H.
Kopp, and C. Gaedicke, 2008, The great
Sumatra-Andaman earthquakes: Imaging
the boundary between the ruptures of the
great 2004 and 2005 earthquakes: Earth
and Planetary Science Letters, 269, p. 118–
130.
Ganguly, N., G. D. Spence, N. R. Chapman, and R.
D. Hyndman, 2000, Heat flow variations
from bottom simulating reflectors on the
Cascadia margin: Marine Geology, 164, p.
53–68.
Hardjono, T. S. Asikin, and J. Purnomo, 1998,
Heat flow estimation from seismic reflection
anomalies in a frontier area of the Sebakor
Sea, Irian Jaya, Indonesia. In: J.L. Rau
(Ed.): Proc. 33rd Session Co-ord. Committee
Coastal Offshore Geosci. Programmes East
and SE Asia (CCOP), Shanghai 1996, 2, p.
56–83.
He, L., J. Wang, X. Xu, J. Liang, H. Wang, and G.
Zhang, 2009, Disparity between measured
and BSR heat flow in the Xisha Trough of
the South China Sea and its implications for
the methane hydrate: J. Asian Earth
Sciences, 34, p. 771–780.
Kaul, N., A. Rosenberger, and H. Villinger, 2000,
Comparison of measured and BSR-derived
heat flow values, Makran accretionary
prism, Pakistan: Marine Geology, 164, p.
37–51.
Kvenvolden, K. A., 1988, Methane hydrate—a
major reservoir of carbon in the shallow
geosphere?: Chemical Geology, 71, p. 41–51.
León, R., L. Somoza, C. J. Giménez-Moreno, C. J.
Dabrio, G. Ercilla, D. Praeg, V. Díaz-del-Río,
and M. Gómez-Delgado, 2009, A predictive
numerical model for potential mapping of
the gas hydrate stability zone in the Gulf of
Cadiz: Marine and Petroleum Geology, 26, p.
1564–1579.
López, C. and G. Y. Ojeda, 2006, Heat flow in the
Colombian Caribbean from the Bottom
Simulating
Reflector
(BSR):
Ciencia,
Tecnología & Futuro, 3 (2), p. 29–39.
Lutz, R., C. Gaedicke, K. Berglar, S. Schloemer, D.
Franke, and Y. S. Djajadihardja, 2011,
Petroleum systems of the Simeulue fore-arc
basin, offshore Sumatra, Indonesia: AAPG
Bulletin, 95 (9), p. 1589–1616.
Millero, F., C. Chen, A. Bradshaw, and K.
Schleicher, 1980, A new high pressure
equation of state for seawater: Deep Sea
Research, Part A, 27, p. 255-264 (water
density
equation
was
accessed
at
http://www.csgnetwork.com/water_density_
calculator.html , on 10th of March, 2015).
Pollack, H. N., S. J. Hurter, and J. R. Johnson,
1993, Heat flow from the earth's interior:
Analysis of the global data set: Review of
Geophysics, 31 (3), p. 267–280. (Note: global
heat flow database is also available at
http://www.heatflow.und.edu/
and
the
colour-coded world heat flow distribution is
available at http://www.geophysik.rwthaachen.de/IHFC/heatflow.html)
Shankar, U., N. K. Thakur, and S. I. Reddi, 2004,
Estimation of geothermal gradients and heat
flow from Bottom Simulating Refelectors
along the Kerala-Konkan basin of Western
Continental Margin of India: Current
Science, 87 (2), p. 250–253.
Shankar, U. and M. Riedel, 2013, Heat flow and
gas hydrate saturation estimates from
Andaman Sea, India: Marine and Petroleum
Geology, 43, p. 434–449
Shankar, U., K. Sain, and M. Riedel, 2014,
Assessment of gas hydrate stability zone and
geothermal modeling of BSR in the
Andaman Sea: J. Asian Earth Sci.79, p.
358-365.
Shyu, C.T., Y. J. Chen, S. T. Chiang, and C. S. Liu,
2006, Heat flow measurements over Bottom
Simulating Reflectors, offshore southwestern
Page 25 of 34
Taiwan: Journal of Terrestrial Atmospheric
and Oceanic Sciences, 17 (4), p. 845–869.
Smyth, H., 2010, SE Asia heatflow database:
Accessed online on March 20, 2015
http://searg.rhul.ac.uk/current_research/h
eatflow/index.html
Wang, K., R. D. Hyndman, and E. E. Davis, 1993,
Thermal effects of sediment thickening and
fluid expulsion in accretionary prisms:
Model
and
parameter
analysis:
J.
Geophysical Research, 98 (B6), p. 99759984.
World
Ocean
Atlas,
2013,
http://www.nodc.noaa.gov/cgibin/OC5/SELECT/woaselect.pl
accessed
online on March 8, 2015.
Xu, W. and C. Ruppel, 1999, Predicting the
occurrence, distribution and evolution of
methane gas hydrate in porous marine
sediments: J. Geophysical Research, 104
(B3), p. 5081–5095.
Yamano, M., S. Uyeda, Y. Aoki, and T. H. Shipley,
1982, Estimates of heat flow derived from
gas hydrates: Geology, 10, p. 339–343.
Page 26 of 34
Frontier Exploration Using an Integrated Approach of
Seafloor Multibeam, Drop Core and Seismic Interpretation
– A Study Case from North Banggai Sula
Farid Ferdian
Saka Energi Indonesia
EXTENDED ABSTRACT
Figure 1.
Regional
Structures
Map (After
Ferdian,
2010 and
Ferdian et
al., 2010).
Exploration in frontier areas is always challenging
and has resulted in the development of various
new technologies including georeferenced, high
resolution seafloor multibeam bathymetry and
backscatter. The multibeam bathymetry data
provides sea floor depth information, while the
backscatter data records the amount of acoustic
energy received by the sonar after interactions with
the sea floor and are used to infer seabed features
and materials. Interpretation of these new dataset
combined with piston cores and seismic data have
been conducted in the offshore of North Banggai
Sula. This integrated approach has been termed as
SeaSeepTM technology.
Page 27 of 34
Figure 2. Seafloor multibeam bathymetry (a) and backscatter (b) of the western portion of study area
(After Ferdian, 2010).
Figure 3. Seafloor multibeam bathymetry and backscatter which corresponds with: 3a. Mounded feature
interpreted as mud volcano; 3b. Subsea outcrop due to fault displacement.
In 2007, TGS-NOPEC with co-operation of Migas
has conducted Indodeep multi-client project which
is comprised of acquiring seafloor multibeam
bathymetry and backscatter, seafloor piston cores
and regional 2D seismic survey across the frontier
areas of Eastern Indonesia, including the study
area presented here (Figure 1). Subsequent
publications on the application of these new data
(e.g. Decker et al., 2009; Noble et al., 2009; Orange
et al., 2009; Riadini et al., 2009; Ferdian et al.,
2010; Rudyawan et al., 2011 etc.) have given a
new understanding of the geology and hydrocarbon
prospectivity of these frontier areas. One of the
publications, entitled “Evolution and hydrocarbon
Page 28 of 34
prospects of the North Banggai-Sula area: an
application of Sea SeepTM technology for
hydrocarbon exploration in underexplored areas”
and was written by current author and published
in the Proceedings of 2010 IPA Convention, is
summarized here as this extended abstract.
Interpretation
of
both
seabed
multibeam
bathymetry and 2D seismic lines has identified
several new structures in the area (Figure 1). In
the west, a dextral fault system is clearly identified
which is thought to continue onshore to the Poh
Head of Sulawesi’s East Arm. In this Poh Head
area, an abrupt elevation change with steep-sided
topography most likely indicates a strike-slip fault.
Along
the
slope
base
of
Banggai-Sula
Microcontinent (BSM) a series of relatively southverging thrusts is identified. However, these
thrusts are not a single fault system such as the
so-called North Banggai-Sula fault that has been
published by many workers (Hamilton, 1978;
Silver, 1981; Silver et al., 1983; Garrard et al.,
1988; Davies, 1990). These thrusts are actually
formed by at least two different events: in the west
it relates to the dextral fault system described
above, while in the east it formed as a southward
continuation of the widespread south-verging
thrust due to gravitational slide from the Central
Molucca Sea Collision Zone. In the middle area
where these two structure systems met, a large
scale slip plane was formed at the seafloor.
Multibeam backscatter data show numbers of
anomalously high backscatter areas across the
study area which correspond to locations of fault
lineaments (Figure 2), mud volcanoes (Figure 3a),
authigenic carbonates and possibly outcrops
(Figure 3b) [Ferdian, 2010]. The well-positioned of
the piston cores deployed into these anomalies can
give further insights on the sedimentology of the
basin through subsequent geochemical analyses
performed by TDI Brooks. Seven core locations
contain possible migrated liquid hydrocarbon (oil),
5 locations of possible migrated thermogenic gas
and another 5 locations of possible migrated both
oil and gas. Hydrocarbon charges from certain
parts of this area show definite marine
characteristic (Noble et al., 2009) with the
Mesozoic marine shale (i.e. Buya Fm.) being the
possible source rocks.
REFERENCES
Davies, I. C., 1990, Geology and exploration review
of the Tomori PSC, eastern Indonesia:
Indonesian
Petroleum
Association,
Proceedings of the 19th Annual Convention,
p. 41–68.
Decker, J., S. C. Bergman, P. A. Teas, P. Baillie,
and D. L. Orange, 2009, Constraints on the
tectonic evolution of the Bird’s Head, West
Papua, Indonesia: Indonesian Petroleum
Association, Proceedings of the 33rd
Convention and Exhibition.
Ferdian, F., 2010, Evolution and hydrocarbon
prospect of the North Banggai-Sula area: an
application of Sea SeepTM technology for
hydrocarbon exploration in underexplored
areas: Indonesian Petroleum Association,
Proceedings of the 34th Convention &
Exhibition.
Ferdian, F., R. Hall, and I. Watkinson, 2010,
Structural re-evaluation of the north
Banggai-Sula, eastern Sulawesi: Indonesian
Petroleum Association, Proceedings of the
34th Convention and Exhibition.
Garrard, R. A., J. B. Supandjono, and Surono,
1988, The geology of the Banggai-Sula
microcontinent,
eastern
Indonesia:
Indonesian
Petroleum
Association,
Proceedings of 17th Annual Convention, p.
23–52.
Hamilton, W., 1978, Tectonic map of the
Indonesian Region: U.S. Geological Survey
Map G78156.
Noble, R., D. Orange, J. Decker, P. A. Teas, and P.
Baillie, 2009, Oil and Gas Seeps in Deep
Marine Sea Floor Cores as Indicators of
Active Petroleum Systems in Indonesia:
Indonesian
Petroleum
Association,
Proceedings of the 33rd Convention and
Exhibition.
Orange, D., J. Decker, P. A. Teas, P. Baillie, and T.
Johnstone, 2009, Using SeaSeep Surveys to
Identify and Sample Natural Hydrocarbon
Seeps
in
Offshore
Frontier
Basins:
Indonesian
Petroleum
Association,
Exhibition.
Riadini, P., A. C. Adyagharini, A. M. S. Nugraha, B.
Sapiie, and P. A. Teas, 2009, Palinspastic
reconstruction of the Bird Head pop-up
structure as a new mechanism of the Sorong
fault: Indonesian Petroleum Association,
Exhibition.
Silver, E. A., 1981, A New Tectonic Map of the
Molucca Sea and East Sulawesi, Indonesia
With Implications for Hydrocarbon Potential
and Metallogenesis. In: Barber, A. J. and
Wiroyusujono, S. (Editors). The Geology and
Tectonics of Eastern Indonesia: Geological
Research and Development Centre – Special
Publication No. 2 Pergamon Press.
Silver, E. A., R. McCaffrey, Y. Joyodiwiryo, and S.
Stevens, 1983, Ophiolite emplacement and
collision between the Sula platform and the
Sulawesi island arc, Indonesia: Journal of
Geophysical Research, 88, p. 9419–9435.
Page 29 of 34
Marine Expeditions in Indonesia during the Colonial Years
Prepared by Herman Darman based on 2005 publication by van Aken
During the colonial years there was little support
from the Netherlands government for non-applied
scientific work. The colonies had to pay for
themselves and had to be profitable for the
Netherlands; science was not considered to be a
good investment.
Nevertheless, a number of
important oceanographic expeditions took place,
for example, the Siboga and Snellius expeditions.
Both were named after the ships that carried the
scientists and both were paid for by the
Netherlands government. The objective was to
prove that the Dutch Indies were not only the best
governed, but also the scientifically most developed
tropical colony. Moreover there were the Dutch
who needed to consolidate colonial rule by showing
the flag over the whole archipelago. Germans,
British, Americans and Japanese were encroaching
on the Far East (New Guinea, Philippines,
Malaysia and Taiwan) and in some ways the
expedition can be considered as ‘gunboat science’.
Even so, vast amount of prime oceanographical,
hydrographical, biological and geological data were
collected with state-of-the-art equipment.
Figure
1.
The
Siboga
at
sea
http://nl.wikipedia.org/wiki/Siboga-expeditie).
The Siboga expedition (1899-1900, Figures 1 and
2) was executed with an adapted gunboat made
available and paid for by the colonial government.
It was very much biologically oriented (Figure 3),
but useful oceanographical data were also
collected. Some 238 depth soundings were added
to the 50 already measured, but few purely
geological data were collected. Of interest is the
fact that a female scientist, Mrs. Weber-Van Bosse
(Figure 4), specialist in algae, participated in the
entire trip; she was probably the first woman in
the history of oceanography to serve in such a role.
She also was the wife of the leader of the
expedition, the biologist Max Weber, but she fully
earned her keep and published three monographs
on the algae collected during the expedition.
Amongst other things she proved beyond doubt,
that coccoliths are of organic origin and belong to
the algae (Weber-Van Bosse, 2000). She received
an honorary doctorate from Utrecht University in
1910, another first in history for a Dutch woman.
(source:
http://hydro-international.com
&
Figure 2. The Siboga expedition trips 1, 2 and 3. (source: van Aken, 2005).
Page 30 of 34
The Snellius expedition (1929-1930,
Figures 4, 5 and 6) focused on the physical
and chemical oceanography of the deep
basins of the East Indies and the geology
of its coral reefs. Again the government
provided the ship, this time built as a
scientific vessel, named it after one of the
greatest Dutch scientists Snel(lius) van
Royen and paid for the expedition
expenses. The expedition leader was P. M.
van Riel, a retired naval officer, head of
oceanography and maritime meteorology at
the Royal Meteorological Institute of the
Netherlands
(Koninklijk
Nederlands
Meteorologisch Institut, KNMI). On board
was also Philip Kuenen (Figure 4), who
was
to
become
an
internationally
renowned sedimentological and marine
geologist at Groningen University. A total
of 374 station soundings were recorded
and over 500 bottom samples were
collected during three trips. Regular shore
parties were organized to visit the coral
islands and to study their geology. The
echo sounder was in nearly constant use,
resulting in 33,000 measurements and
this alone immensely improved our
knowledge of these deep-sea tract.
Figure 3.
Cover of a report from Siboga
Expedition, a collection of the Naturalist Museum,
Leiden, the Netherlands (photo by H. Darman).
Study of the vast amount of data collected
by the expedition was greatly delayed,
especially
as
far
as
the
purely
oceanographic data were concerned, but
also the geological and biological data
proved too much to be quickly dealt with. This is
aptly demonstrated by the fact that, as late as
1978, an article was published on the foraminifers
from the Snellius expedition, as a final addition to
the already published 23 volumes of Snellius
reports (Figure 7).
Figure 4.
Left: Anne
Antoinette
Weber-van
Bosse (1852-1942); Source:
Wikipedia (left); and Right:
Philip H. Kuenen (19021976);
Source:
http://resources.huygens.
knaw.nl/bwn18802000/lemmata/bwn5/kue
nen).
Page 31 of 34
Figure 5. Snellius expedition 1929-1930 (1st trip) (Boekschoten. et al., 2012).
Figure 6. The Hr. Ms. Snellius ship at sea (Boekschoten. et
al., 2012).
REFERENCES
Boekschoten, B. et al., 2012, Dutch Earth
Sciences: Development and Impact, Royal
Geological and Mining Society of the
Netherlands, 1912-2012 Centenary Volume.
http://resources.huygens.knaw.nl/bwn18802000/lemmata/bwn5/kuenen)
Figure 7.
Example of a Snellius
expedition report in the Naturalist
Museum, Leiden, the Netherlands (Photo
by H. Darman).
http://hydro-international.com
http://nl.wikipedia.org/wiki/Siboga-expeditie
van Aken, H. M., 2005, Dutch oceanographic
research in Indonesia in colonial times:
Oceanography 18(4), p. 30–41.
Page 32 of 34
.
Page 33 of 34
Number 30 – August 2014
BIOSTRATIGRAPHY OF SE ASIA – PART 2
Page 34 of 34

The Indonesian Sedimentologists Forum (FOSI)

Transcription

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