the indonesian sedimentologists forum (fosi) - iagi

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Berita Sedimentologi JAVA

Number 26 – May 2013

Published by

The Indonesian Sedimentologists Forum (FOSI) The Sedimentology Commission - The Indonesian Association of Geologists (IAGI)

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Editorial Board

Herman Darman Chief Editor Shell International Exploration and Production B.V.

P.O. Box 162, 2501 AN, The Hague – The Netherlands

Fax: +31-70 377 4978

E-mail: [email protected]

Minarwan Deputy Chief Editor Mubadala Petroleum (Thailand) Ltd. 31st Floor, Shinawatra Tower 3, 1010 Viphavadi

Rangsit Rd.

Chatuchak, Bangkok 10900, Thailand E-mail: [email protected]

Fuad Ahmadin Nasution Total E&P Indonesie

Jl. Yos Sudarso, Balikpapan 76123 E-mail: [email protected]

Fatrial Bahesti PT. Pertamina E&P NAD-North Sumatra Assets

Standard Chartered Building 23rd Floor

Jl Prof Dr Satrio No 164, Jakarta 12950 - Indonesia E-mail: [email protected]

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 E-mail: [email protected]

Rahmat Utomo Mubadala Petroleum (Thailand) Ltd. 31st Floor, Shinawatra Tower 3, 1010 Viphavadi

Rangsit Rd.

Chatuchak, Bangkok 10900, Thailand E-mail: [email protected]

Advisory Board

Prof. Yahdi Zaim Quarternary Geology Institute of Technology, Bandung

Prof. R. P. Koesoemadinata Emeritus Professor Institute of Technology, Bandung

Wartono Rahardjo University of Gajah Mada, Yogyakarta, Indonesia

Ukat Sukanta ENI Indonesia

Mohammad Syaiful Exploration Think Tank Indonesia

F. Hasan Sidi Woodside, Perth, Australia

International Reviewers

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 E-mail: [email protected]

Dr. T.J.A. Reijers Geo-Training & Travel

Gevelakkers 11, 9465TV Anderen, The Netherlands E-mail: [email protected]

Peter M. Barber PhD Principal Sequence Stratigrapher Isis Petroleum Consultants P/L

47 Colin Street, West Perth, Western Australia 6005


• 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.

Cover Photograph:

Halang Formation outcrop at

Bantarkawung district, Brebes

– Central Java. Taken in 1991.

Photo courtesy of Herman

Darman.

mailto:[email protected]


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Welcome to Berita Sedimentologi number 26!

In this edition, Berita

Sedimentologi No. 26/2013, we

are focusing on Java Island and

its vicinity. Three of the articles received by the editors cover the

eastern part of Java. Edwin and

co-authors have submitted a paper on Mundu-Paciran

Nannofossil zones. A paper on 3D

facies modeling on deepwater fan outcrop, onshore east Java, was

prepared by Cahyo et al. Surya

Nugraha and co-author discussed the Cenozoic stratigraphy of the

forearc system in the southeast of

Java.

A regional overview of Java sandstone composition was

summarized by Darman et al.

A relatively new research group has been established in UPN

“Veteran” Yogyakarta in mid

2010. Budiman et al has kindly

provided us an introduction article to this group.

The editors have also come up with general plan for future

themes as the following

BS#27 Sumatra: to be

published in August 2013

BS#28 Borneo: to be published

in November 2013

BS#29 SE Asia Biostratigraphy

to be published in early 2014

Hopefully with this plan potential

contributors can plan ahead in preparing their articles.

FOSI‟s Linked-In group registered 655 members in May 2013. The

demographics of the group

indicate a good balance between the senior and junior

geoscientists. The majority of the

members are from oil and gas industry (78%), followed by the

mining and metals (15%).

At last on behalf of the editorial team, I wish you a good reading

time and hopefully you get the

benefit from this bulletin.

Best Regards,

Herman Darman

Chief Editor

INSIDE THIS ISSUE

Cenozoic Stratigraphy of the East Java Forearc – A. M. S. Nugraha & Robert Hall

5

A Case Study on Using Mundu-Paciran Nannofossil zones (MPNZ) to Subdivide Mundu and Paciran Sequences in the MDA Field, East Java Basin, Indonesia – A. Edwin et al.

26

Book Review : The SE Asian Getway: History and Tectonic of the Australian-Asia Collision, editor: Robert Hall et al – T.J.A. Reijers

56

A Brief History of GeoPangea Research Group – A. Budiman et al.

18

Short Note : Mineral Composition of Eocene and Miocene Sandstones in Java Island – H. Darman et al.

33

Book Review - Biodiversity, Biogeography and Nature Conservation in Wallacea and New Guinea (Volume 1), Edited by D. Telnov, Ph.D. – H. Darman

58

Three-Dimensional Facies Modeling of Deepwater Fan Sandbodies: Outcrop Analog Study from the Miocene Kerek Formation, Western Kendeng Zone (North East Java Basin) – F. A. Cahyo et al.

19

Berita Sedimentologi

A sedimentological Journal of the Indonesia Sedimentologists Forum

(FOSI), a commission of the Indonesian Association of Geologist (IAGI)

From the Editor

Call for paperBS #27 Sumatera

to be published in August 2013

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About FOSI

he forum was founded in 1995 as the Indonesian

Sedimentologists Forum

(FOSI). This organization is a commu-nication 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.

Most of FOSI administrative work will be handled by the editorial

team. IAGI office in Jakarta will help if necessary.

The official website of FOSI is:

http://www.iagi.or.id/fosi/

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.

T

FOSI Membership

FOSI Group Member

as of MAY 2013

http://www.iagi.or.id/fosi/

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Cenozoic Stratigraphy of the East Java Forearc A.M. Surya Nugraha and Robert Hall

SE Asia Research Group, Department of Earth Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK

Corresponding Author: [email protected]

INTRODUCTION The study area is located in the offshore SE Java and is situated at the southeast edge of the

Eurasian plate, known as Sundaland (Figure. 1

and Figure 2). Sundaland is the continental core of

SE Asia and was constructed by amalgamation of continental blocks during the Mesozoic (Hamilton,

1979; Metcalfe, 1996; Hall & Morley, 2004).The

East Java Forearc is a relatively unexplored area and the basement has long been considered to be

Cretaceous arc and ophiolitic-accretionary

complexes (Hamilton, 1979; Wakita, 2000). But now there is increasing evidence for continental

crust beneath the East Java Sea (Manur &

Barraclough, 1994; Emmett et al., 2009; Granath et al., 2011), and the southern part of East Java

(Smyth, 2005; Smyth et al., 2007, 2008).

This article presents the findings of an MSc study (Nugraha, 2010) and a geological history presented

in an IPA paper (Nugraha & Hall, 2012). New

seismic lines south of Java have imaged a deep stratified sequence which is restricted to East Java

and is absent beneath the West Java forearc. Main

datasets were provided by TGS, comprising three long-offset 2D-seismic datasets (SJR-9, SJR-10,

and SJI-10). These data consist of thirty-seven 2D

marine seismic lines across the Java forearc with a total of 8266 km survey length. Previously

published seismic data (Kopp et al., 2006) were

limited to shallow imaging 4-streamer seismic

sections.

All three TGS seismic datasets image down to 9

seconds two-way-time (TWT) and show very deep

units in the forearc basin not seen in previously

published seismic data in the area (Figure 3 and Figure 4). Three well datasets were available,

including: Cilacap-1, Borelis-1, and Alveolina-1.

The Borelis-1 and Alveolina-1 wells were drilled by Djawa Shell N.V. (Bolliger & de Ruiter, 1975) in the

early 1970s and are located in the shallow part of

the offshore Central Java forearc (Figure 2). These wells encountered mid-late Cenozoic rocks and

have about 2 km total depth (Figure 5). The

biostratigraphic top information (Shell interpretations) from these wells form the main

reference for our mid and late Tertiary age-

controlled stratigraphic interpretation.

Figure 1. Location of the study area (red box).

Figure 2. Seismic grid used in this study and location of wells.

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REGIONAL STRATIGRAPHY

Subduction and significant arc volcanism ceased beneath Java from about 90 Ma to 45 Ma (Hall et

al., 2009, Hall, 2009, 2011). Subduction resumed

when Australia began to move northwards in the

Middle Eocene (Hall, 2009). The oldest Cenozoic sediments reported onshore East Java are Middle

Eocene (Lelono, 2000, Smyth et al., 2008) and

were deposited unconformably on basement rocks. The Early Cenozoic sandstones above the oldest

sediments increase in volcanic material up-section

recording initiation of the Southern Mountain Arc (Smyth, 2005). There is an intra-Oligocene

unconformity across East Java and the East Java

Sea that was mainly caused by sea level change (Matthews & Bransden, 1995; Smyth, 2005).

Explosive volcanic activity was extensive throughout the Late Oligocene to Early Miocene as

indicated by thick sequences of volcanic and

epiclastic rocks (Smyth, 2005; Smyth et al., 2008). The oldest dated sediments exposed in the

Southern Mountains Arc are Oligocene reworked

bioclastic tuffaceous mudstones (Smyth et al., 2008). Upper Oligocene volcaniclastic rocks have

been reported in the Shell Alveolina-1 well,

offshore Central Java. In the Borelis-1 well, the

oldest dated rocks are Early Miocene. These two wells terminated in undated basalt (Bolliger & de

Ruiter, 1975) confirming the presence of Southern

Mountain Arc volcanism in offshore South Java.

Figure 3. Approximately N-S seismic line across the East Java

Forearc (A) uninterpreted and (B) interpreted, showing main

tectonic elements of the forearc and the Lower and Upper Sections

Figure 3. Approximately N-S seismic line across the East Java Forearc (A) uninterpreted and (B) interpreted, showing main tectonic elements of the forearc and the Lower and Upper Sections.

Figure 4. Approximately E-W seismic line along the Java Forearc (A) uninterpreted and (B) interpreted, showing the contrast in structure and stratigraphy of the forearc south of West and Central Java compared to that south of East Java. The Lower Section is thick south of East Java and dies out close to a cross-arc high at the position of the Progo-Muria lineament of Smyth et al. (2005).

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The Early Cenozoic arc volcanism was terminated by the short-lived Early Miocene Semilir super-

eruption event (Smyth 2005, Smyth et al., 2008,

2011). The whole southeast region of Sundaland was uplifted during this period (Sribudiyani et al.,

2005). To the north, a sequence boundary is

placed at the top of the Prupuh Limestone because basin inversion is interpreted to have been

initiated on a regional scale near to the end of its

deposition in the Middle Miocene (Matthews & Bransden, 1995).

During the Middle Miocene to Late Miocene,

volcanic activity was much reduced. Older volcanic material was reworked and carbonate platforms

were developed extensively during this period

(Bolliger & de Ruiter, 1975; Smyth, 2005). The carbonates range in age from late Early Miocene to

Middle Miocene (Lokier, 2000; Smyth, 2005).

Several tuff beds are observed in turbidite sequences in the Southern Mountains and range

in age from 12 to 10 Ma (Smyth, 2005). This

represents the resumption of volcanic activity at the position of the present Sunda Arc (Smyth et

al., 2005). Lunt et al. (2009) suggested that an

unconformity recorded a Late Miocene tectonic event which created a new series of basins that

were filled by erosion of structural highs in Central

Java. There are no Pliocene or Quaternary deposits

in the Southern Mountains zone due to uplift and erosion.

Figure 5. Parts of seismic lines that intersect wells Alveolina-1 and Borelis-1 showing seismic units identified in this study and ages of horizons from Bolliger & de Ruiter (1975).

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The Shell exploration wells record a major tectonic

event in the Late Pliocene which caused uplift of Java and the deposition of widespread Pliocene

and Quaternary sediments in the offshore area

(Bolliger & de Ruiter, 1975).

STRATIGRAPHIC UNITS We identify six seismic stratigraphy units, labelled

A to F, on the basis of their age, seismic character and deformation style in combination with onshore

published studies (Figure 6). We describe these

units from the shallowest to deepest, i.e. from F to A. The ages of Units D to A are reasonably

constrained by the exploration wells drilled south

of Central Java. The ages of Units E and F are

unknown. We consider two possible interpretations for the lower section. Unit E shows a half graben

character in places suggesting that rifting and

extension may be plausibly correlated with Southern Mountains volcanics and volcaniclastic

deposits on land in East Java (Smyth et al., 2005,

2008). Unit F could represent a deeper part of this arc sequence. To the north of the Southern

Mountains lies the thick sequence of the Kendeng

Basin. Thus one possibility is that the thick sequence of Units E and F is equivalent to the

Middle Eocene to Oligocene deposits of the

Kendeng Basin. An alternative is that Unit F is a

pre-Eocene sequence that was rifted when arc activity resumed in the Middle Eocene.

Pre-Neogene: Unit F

Unit F is the deepest seismic unit recognizable and

it is observed only in the deepest part of the forearc basin (Figure 7). It shows a relatively

uniform ~3 s TWT thickness. The lower part shows

moderate to weak reflectors, while the middle part is characterized by bright and parallel reflectors

with discontinuous lower amplitude reflectors. The

upper part is characterized by chaotic, discontinuous weak amplitude reflectors which are

brighter and relatively parallel near the forearc

basin edges. This unit is cut by a series of planar extensional faults with small displacements

forming graben and half graben structures. The

faults are more intense in E-W sections along the forearc basin than in N-S sections. A few faults

have been reactivated close to the subduction

complex and structural highs to the north. There are also a few internal thrust faults within this

unit which record later deformation. In places this

unit seems to be truncated by younger units.

Unit F is best imaged beneath the forearc basin

where the Neogene cover is thin and the structure

is relatively simple, and cannot be mapped at depths below about 6 sec TWT beneath the forearc

flank closer to the Southern Mountains. Although

it not seen Unit F could thicken towards the arc, where its internal character would be expected to

become more complex and seismically opaque

closer, since it would be dominated by volcanic rocks rather than the volcaniclastics and

carbonates deposited farther from the active arc.

This unit would then form a load-induced

depocentre south of the arc comparable to the Kendeng Basin succession and would thicken

towards the arc, although the distribution and

thickness of the sequence would influenced by several other factors such as the character of the

underlying crust, the width of the forearc and the

dip of the subducting slab. The Kendeng Basin formed during the Middle Eocene through to Early

Miocene (de Genevraye & Samuel, 1972; Untung &

Sato, 1978; Smyth et al., 2005, 2008) and consists of terrestrial and shallow marine rocks in a thick

succession that thickens toward the Southern

Mountains volcanic arc.

Figure 6. Proposed relations between seismic units of offshore East Java (Alveolina area) and the stratigraphy of the Southern Mountains Zone on land in East Java (from Smyth et al. 2005, 2008).

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Untung & Sato (1978) suggested that the deeper parts of the basin contain ~6 km of section.

Waltham et al. (2008) used gravity data to suggest

an approximate thickness of up to 10 km and proposed that the Kendeng Basin formed by

volcanic arc loading of a broken plate, with a

contribution from crustal extension and/or deep crustal loading. In this interpretation the half

graben of Unit E would represent extension at a

relatively late stage in the development of the Southern Mountains arc.

An alternative is that Unit F is older than Middle

Eocene. Deighton et al. (2011) suggested that this unit could be Mesozoic based on its position and

similarity of seismic character with Mesozoic

and/or Palaeozoic sections from the Australian NW Shelf. If the rifting that affects Unit E is Middle

Eocene then Unit F is older. Smyth et al. (2005,

2007, 2008) suggested that parts of East Java may be underlain by a Gondwana fragment derived

from western Australia, while a thick cover

sequence of (possibly?) pre-Cenozoic age, identified offshore East Java (Emmett et al., 2009; Granath

et al., 2010), is suggested to have a West

Australian origin. In the part of the forearc where

Unit F is well imaged it has a relatively constant thickness with sub-parallel reflectors and can be

traced for several hundred kilometres along the length of the forearc. Internal deformation is

largely restricted to extensional faulting that pre-

dates deposition of the forearc basin sequence of Miocene and younger age. These features are

consistent with a terrestrial to open marine

sedimentary sequence deposited on continental crust when the East Java–West Sulawesi fragment

formed part of the Australian margin (Hall et al.,

2009).

This suggestion is supported by the existence of

deep NW-SE lineaments discussed above. Hall

(2011) suggested that some NW-SE deep structural lineaments, traced across Borneo and into

Sulawesi (e.g. Satyana et al. 1999; Fraser et al.

2003; Gartrell et al. 2005; Puspita et al. 2005; Simons et al. 2007) represent basement structures

inherited from Australian blocks. Deep and old

structures can be traced offshore across the NW Shelf and Western Australia (e.g. Cadman et al.

1993; Goncharov 2004). We suggest that the deep

NW-SE structural lineaments in the East Java Forearc have a Gondwana origin and, based on the

limited evidence available, we prefer to interpret

Unit F as a Mesozoic or older section above

Australian continental basement.

Figure 7. Approximately N-S seismic line across the East Java Forearc (A) uninterpreted and (B) interpreted showing seismic units and principal structural features. The deeper reflectors of Unit F are mappable mainly below the forearc basin. Note the continuity and broadly constant thickness of seismic reflectors in Unit F which is cut mainly by extensional faults, except close to the accretionary zone where there are some thrust faults.

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Pre-Neogene: Units E and D

Unit E is mainly observed in the arc-flank and is

characterized by parallel discontinuous reflectors

(Figure 8). Wedge geometry is observed with thickening towards faults and is interpreted to

indicate sedimentary layers deposited in a syn-rift

event. A series of planar extensional faulted graben and half graben are observed within this unit along

faults with larger displacements than in Unit F.

Several of these faults have been reactivated at the structural highs. Unit E is interpreted to have been

deposited unconformably above Unit F. In places

close to the slope break in the forearc flank, Unit F seems to be truncated by Unit E.

Unit E is tentatively interpreted as alluvial to delta

plain deposits, with higher and lower amplitudes indicating intervals of sand and shale. It is

suggested that this sequence was deposited during

rifting in the Middle Eocene. Contemporaneous clastic sediments in the East Java Sea Basin

(Matthews & Bransden, 1995) and Java were

deposited above a regional angular unconformity in a terrestrial to marine environment. In the

Southern Mountains the Middle Eocene Nanggulan

Formation includes coals, conglomerates, silts and quartz-rich sands (Lelono, 2000; Smyth, 2005;

Smyth et al., 2005, 2008).

Unit D was deposited conformably above Unit E .In

contrast with the unit below, Unit D shows

generally continuous and well bedded strong reflectors with wedge geometry, but does not

clearly thicken towards faults. The seismic

reflectors become brighter and more continuous basinward which suggests a facies change. Unit C

was probably deposited at the end of the syn-rift

stage. This unit appears to be thinner and

truncated by the base of Unit C near to structural highs, and is interpreted to be associated with

inversion and erosion. Unit D contains Globigerina angulisuturalis and Globigerinoides trilobus fossils from wells and has been dated as Late Oligocene

(N2-N3) and Middle Early Miocene (N5-N6) above

basalts, volcanic agglomerates, tuffs and clays

(Bolliger & de Ruiter, 1975). Contemporaneous volcanic deposits crop out in the Southern

Mountains Zone and Kendeng Zone (Smyth 2005;

Smyth et al., 2005, 2008).

Figure 8. Approximately N-S seismic line across the forearc flank (A) uninterpreted and (B) interpreted. Units D and E are clearly observed below the Unit C carbonate platform and build-ups.

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Middle Miocene Unit C

Unit C shows strong, parallel and fairly continuous reflectors which become variable in amplitude

away from carbonate buildups. The bright

reflectors are interpreted as limestone and the varying amplitude is interpreted as an alternation

of shelf carbonates and mudstone. The carbonate

buildups tend to be developed on top of structural or topographic highs (Figure 9). Pinnacle reefs are

observed at the later stage of several carbonate

buildup developments. The unconformity between

Units D and C is interpreted to be of Early to Middle Miocene age. Based on well data and

seismic character Unit C is interpreted to comprise

Middle Miocene carbonates equivalent to the onshore Middle Miocene to Lower Pliocene

Wonosari Formation (Lokier, 1999). The Borelis-1

well penetrated the lower part of this unit, dated as Late Middle Miocene based on Globorotalia siakensis, and the Alveolina-1 well records

carbonate wackestone above (Bolliger & de Ruiter,

1975). Unit C is characterized by widespread carbonate development above the unconformity,

particularly on structurally high areas associated

with localized contractional truncation by the unconformity. Progradational cycles are observed

within the lower part of the carbonates above the

unconformity showing that they were initially deposited in lowstands during a period of quiet

tectonism and much reduced volcanism (Figure

10a), and are followed by cycles from progradational to retrogradational and/or

aggradational upward (Figure 9). The carbonate

platform is widespread in the western part of the study area and decreases to the east.

Upper Miocene Unit B

Unit B is characterized by bright, continuous, alternating reflectors, which are weaker in the

middle part (Figure 11). The upper part of Unit B is

observed to onlap onto the lower part of the carbonate buildup Unit C (Figure 7). Unit B shows

a relatively constant 0.6-0.8 s TWT thickness

suggesting deposition on the margin slope or outer platform.

Figure 9. Seismic section crossing carbonate build-up of Unit C in the forearc flank (A) uninterpreted and (B) interpreted. The internal structure of Unit C shows cycles of progradation, retrogradation and aggradation.

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Figure 10.

Palaeogeographic maps for the East Java forearc based on this study for (a) Middle Miocene, (b) Late Miocene to Middle Pliocene, (c) Late Pliocene, and (d) Recent. The entire forearc has subsided significantly since the Late Miocene.

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The lower part is interpreted as carbonate

mudrock, while the upper part could be mudrock or tuff. To the east, close to Lombok Basin, Unit B

thins towards the forearc basin depocentre (Figure

12) where it is interpreted to have been deposited above a paleo-high, suggested by a high positive

gravity anomaly across the eastern part of the East

Java forearc (Seubert & Sulistianingsih, 2008). This unit has been uplifted and eroded in the outer

arc ridge and forearc flank (Fig 11). A slump or

mass transport complex is observed and is

interpreted to be the result of reactivation of an older structure.

Unit B was deposited conformably above Unit C in a transgressive setting. Deepening at this time is

associated with a diminished area of carbonate

deposition characterised by isolated pinnacle reefs (Figure 10b). The Borelis-1 well penetrated clay at

the top of this unit dated as Late Miocene (N18)

based on the presence of Globorotalia margaritae (Bolliger & de Ruiter, 1975). Deformation

characterized by uplift that folded and eroded the

upper part of the sequence occurred during deposition of Unit B. This abrupt deformation is

interpreted to be related to the arrival of a

seamount or buoyant plateau (similar to but not the Roo Rise) at about 8 Ma. Lunt et al. (2009)

noted several basins filled with reworked material

caused by this deformation in Central Java.

Pliocene Unit A

Unit A shows moderate to weakly continuous

reflectors interrupted by bright continuous reflectors in places (Figure 11). It is interpreted to

consist of rapidly deposited pelagic/hemipelagic

and volcanogenic deposits (Figure 10c). Unit A was deposited unconformably above Unit B across the

whole East Java Forearc. This unit contains

Globoquadrina altispira and Globorotalia tosaensis

dated as Early Pliocene (N19) and Middle-Late Pliocene (N20-N21) in the wells.

Figure 11. Seismic section showing units at the southern boundary of the forearc basin with the outer-arc slope (A) uninterpreted and (B) interpreted. The basin is affected by the latest deformation which has folded Units A and B and which appears to be driven by uplift of the outer-arc high. Note the slump complexes in the upper part of the outer-arc slope.

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Unit A is interpreted to comprise Pliocene

volcaniclastics and deep marine clays, sometimes

interbedded with calci-turbidites (Bolliger & de Ruiter, 1975). In the forearc basin, Unit A is

characterized by a wedge shape, tilted landwards,

with a number of local unconformities that record

the episodic uplift of the outer arc ridges (Figure 11). These sequences onlap and downlap onto Unit

B. Mass transport-slump complexes observed in

this unit reflect submarine slope failure associated with uplift of the outer-arc high above the

subduction zone. Further north canyons incise

Unit A; some are infilled whereas others are active at the present-day (Fig 13). The high rates and

widespread sedimentation could be related to

resumption of volcanic activity in the modern Java Arc.

CONCLUSIONS

New seismic data allow the East Java forearc to be divided into six major seismic units bounded by

three major unconformities. We suggest that the

deepest, Unit F, may represent a pre-Cenozoic sequence deposited on continental crust, derived

from Western Australia. A major regional

unconformity separates this from a Middle Eocene to Lower Miocene sequence (Units E and D)

equivalent to the Southern Mountains volcanic arc

and Kendeng Basin deposits of East Java.

Extensive shallow water carbonates (Unit C) were deposited above a Lower–Middle Miocene

unconformity during a tectonically quiet period

with much reduced volcanism in the northern part of the present forearc. Major changes in the forearc

began in the Late Miocene.

Figure 12. Seismic section showing units at the southern boundary of the forearc basin with the outer-arc slope east of Figure 9 (A) uninterpreted and (B) interpreted. The forearc basin in this area here is largely filled with Pliocene sediments of Unit A. Note that Unit B is thinner towards the forearc basin depocentre.

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There was significant subsidence (Unit B) with

drowning of the former carbonate platforms. We interpret deformation at the southern side of the

forearc to be caused by arrival of a buoyant

plateau at the subduction margin producing a regional unconformity that can be mapped across

the whole East Java forearc. Afterwards, older

rocks were buried by Late Pliocene volcanogenic

deposits (Unit A) with high rates of sedimentation.

ACKNOWLEDGEMENTS

We thank TGS for providing the data, the

consortium of oil companies who support the SE Asia Research Group for funding the MSc study of

A.M. Surya Nugraha, and Chris Elders, Ian

Deighton and Simon Suggate for advice and help.

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A Brief History of GeoPangea Research Group Agung Budiman, Iqbal Fardiansyah and Leon Taufani

GeoPangea Research Group (GPRG) Indonesia


INTRODUCTION

GeoPangea Research Group (GPRG) is an

independent research group founded on May 31st,

2010, led by ideas from young and passionate geology students of UPN ”Veteran” Yogyakarta. The

group is supervised by Dr. C. Prasetyadi, a faculty

member of the Geology Department, as well as a mentor to all research-related activities conducted

by GPRG. This group aims to contribute to

scientific knowledge in numerous aspects of geosciences (i.e. regional geology, sedimentology

and stratigraphy, structural geology, tectonics,

etc.) by performing research and demonstrating their application in hydrocarbon exploration. The

results of our research are documented as

published papers and articles in various journals

and scientific conferences of both regional and international levels.

GPRG RESEARCH FOCUS

The focus area of GPRG is primarily on field and

experimental-based research (Figures 1 and 2). To

date, there are more than twenty professional papers and articles that have been published by

GPRG, with the first research conducted in late

2010, entitled: Sedimentology of Parangtritis Coastal Dunes and Stream Table Analogue for Fluvial-Deltaic Morphology (Figure 2a). Since then,

this group keeps consistently developing experimental sed-strat analyses and structural

analogue modeling within the loop of research

projects (Figures 2b and 2c). GPRG currently

employs eight professional researchers and six undergraduate students of UPN ”Veteran”

Yogyakarta. Research projects are internally

funded by the members‟ monthly dues and supported by the laboratory facilities of the

Geology Department, UPN ”Veteran” Yogyakarta.

Any questions/interests related to our research group can be addressed to us via the website :

www.gprgindonesia.wordpress.com.

Figure 1. Some photos of GPRG’s field work activities. (a) and (b) outcrop observations ; (c) and (d) example of modern sedimentological study of lagoonal deposits.

Figure 2. Experimental-based research of GPRG, which is facilitated by laboratories of the Geology Department, UPN ”Veteran” Yogyakarta. (a) Stream table analogue for fluvio- deltaic morphology (2010) ; (b) Flume tank modeling to reconstruct chronostratigraphy within growth-faulted delta system (2011) ; and (c) Sandbox analogue for structural kinematics and geometry

identification (2012).

http://www.gprgindonesia.wordpress.com/

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Three-Dimensional Facies Modeling of Deepwater Fan Sandbodies: Outcrop Analog Study from the Miocene Kerek Formation, Western Kendeng Zone (North East Java Basin) Ferry Andika Cahyo1,2, Octavika Malda2, Iqbal Fardiansyah2 and Carolus Prasetyadi1

1Department of Geology UPN ”Veteran” Yogyakarta 2GeoPangea Research Group (GPRG)

Corresponding Author: [email protected], [email protected]

ABSTRACT

Kendeng Zone is well known as the main depocenter in the North East Java Basin. It developed as a back arc basin related to Oligo-Miocene volcanic arc and was subsequently filled with thick pelagic and volcanogenic sediments. This article emphasizes on determination of facies, geometry and distribution of sand bodies within the Miocene Kerek Formation that comprises the western Kendeng Zone. Sedimentological logs and rock samples were collected from outcrop data along river traverses in the study area. The samples were described and characterized by using petrography, paleontology and sedimentology analyses. Three depositional facies were identified, which consist of massive sandstone of submarine lower fan, a lobe of submarine lower fan and pelagic mud deposits. Statistical analysis was also used to characterize and describe identified depositional facies within the Kerek Formation. Statistically, the geometry consists of (1) pebbly massive sandstones of submarine lower fan (mean distribution of sands bodies: 4.58 km, mean thickness: 0.6 m, length from 3D modeling: 1.58 km); (2) sandstone sheets of submarine lower fan (mean distribution of sands bodies: 2.85 km, mean thickness: 0.08 m, length from 3D fence diagram: 1.26 km); (3) pelagic mud, which is composed solely of thick mudstone lithofacies. In term of reservoir potential, the massive sandstones that have significant amount of porosity would be considered as having the highest potential.

INTRODUCTION

The study area is located in Kedungjati region,

Purwodadi, Central Java (Figure 1). Stratigraphically, the area is comprised of four

lithologic units (formations) that include (in

younger order) Calcareous-sandstone of Kerek

Formation, Tuffaceous-sandstone of Banyak Member (Kalibeng Formation), Calcareous-

claystone of Kalibeng Formation and Limestone of

Kapung Member (Kalibeng Formation) (Figure 2).

North East Java basin, particularly the Kendeng

Zone, is located between volcanic arcs at present.

The Kendeng Zone was the main depocenter for

Eocene-Miocene sediments that are composed of

thick turbidite and pelagic sequences (De Genevraye and Samuel, 1972; Smyth et al, 2003 &

2005). The turbidites are recorded in the Miocene

age Kerek Formation.

The objectives of this article are to unravel the

depositional model, then subsequently construct an understanding of relation between turbidite and

reservoir sand bodies based on geometry and

distribution pattern of the Kerek Formation. This article emphasizes on outcrop-based study in

order to get a comprehensive understanding about

deepwater play characteristics in an active margin setting.

Figure 1. Digital elevation model (Shuttle Radar Transect Mission) overlain by schematic zonation of East Java. The study area is bounded by black square (modified from Smyth et al, 2003).



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METHODS

The study includes outcrop visits to produce

sedimentological logs (Figures 3 and 4), geological map and acquire rock samples for laboratory

analyses. The laboratory analyses are comprised of

petrographical and paleontological analyses. Outcrop data and lab results were then used in

geological modeling. The turbidite sandbodies

model (Figures 5 and 6) was built by correlating the sedimentological sections (chronostratigraphic

correlation), then gridding and layering vertical

horizon of sandbodies without involving fault

model. All of these steps were done by using standard 3-D geological modeling software

package.

FACIES & ARCHITECTURAL MODEL

Interpretation of sedimentological logs taken from the outcrops revealed that their depositional facies

are of fan complex, particularly of lower fan

system. The lower fan system was formed by accumulation of individual lobe fans and pelagic

deposits, which are products of high and low

density turbidity current.

Figure 2. Simplified geological map of the study area shows four lithostratigraphic units. The calcareous sandstone of Kerek Formation is shown in yellow colour.

Figure 3. Outcrop of Kerek Formation with representative KJ 98 sedimentological log along the Tuntang

River, Kedung Jati Village.

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Figure 4. Sedimentological log of KJ-85 that is composed sheet sandstone of fan lobe in the lower section and gradually change to massive sandstone in the

upper section.

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Figure 5. Correlation section of the sedimentological logs. The section is flattened on N16 marker.

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The characteristic lithofacies comprised in each

depositional facies of the lower fan system and its geometry are described below:

a. Pebbly massive sandstone of submarine middle fan

The massive sandstone of lower fan deposit

typically consists of some lithofacies that combine

together. Massive coarse sandstone with erosional

base contact dominates the lower portion of the deposit. Gradually normal graded sandstone and

stratified pebbly sandstone occur on several places

as a remark of temporary hydraulic change of the current. Stratified medium-grained sandstone cap

the upper part of the deposit. The entire package

shows a fining upward stacking pattern. Such combination of features is interpreted as the result

of high density turbidity current that occurs on a

fan. The process began with initial high density and velocity of the current allowed for the

transportation and deposition of coarse-grained

materials. As the current kept distributing the

materials to another part of the system, finally on the upper part of the deposit, finer-grained

(stratified medium-grained sandstone) are more

dominant. The results of 2D correlation and 3D modeling show that the mean thickness and sand

body distribution are 0.6 m and 4585.6 m,

respectively. The minimum thickness and distribution of sand bodies are 0.25 m and 1403

m, respectively. The length of the fan as inferred

from a single representative lobe is 1580 m (Figure 8).

b. Sandstone sheets of submarine lower fan

This deposit consists of several lithofacies that can

be easily classified by using Bouma sequence classification (Ta-Te) [Bouma, 1962]. Intercalation

of graded sandstone with erosional contact (Ta),

convolute sandstone (Tc), parallel laminated

siltstone (Td), and stratified mudstone (Te) occur monotonously all over the deposit. Thin bed of

convoluted lamination sandstone also occurs

simultaneously with another lithofacies, which provides evidence for low density turbidity current.

This is due to the current become less dense and

the velocity of the current become less unable to distract semiplastic sediments (Bouma, 2000). It

has been widely accepted that convoluted

lamination is the result of distraction of current on semiplastic sediments, therefore low density

turbidity current produce thin or even no

convolute structure (Shanmugam, 2005). The

result of 2D correlation analysis shows that the mean thickness and distribution of sand bodies

are 0.08 m and 2855.4 m, respectively, with the

minimum thickness and deployment of sand bodies being 0.02 m and 1011 m, respectively. The

length of the fan, as inferred from a single

representative middle fan is 1264 m.

c. Pelagic mud

This deposit consists solely of thick mudstone

lithofacies. Pelagic mud is the result of suspension process that occurs in almost all deep sea setting.

PALEOCURRENT ANALYSIS

Paleocurrent direction can be identified from a

variety of erosional structures such as tool mark, grove cast and flutecast. In the study area,

paleocurrent direction was analysed from flute cast

structures. The flute cast structure measurements indicate that the main trend of sediment supply

moving from north to south with average direction

of N 144o E (NW-SE) (Figure 6).

DISCUSSIONS AND CONCLUSIONS The unique characteristic possessed by turbidite

sediments in the Western Kendeng Zone is that

they are part of fan lobe complex and encompasses mixed sand and mud with overall coarsening

upward stacking pattern. Tectonically, turbidite

deposits within the Kendeng Zone and its vicinity are quite different due to the active margin and

volcanic arc setting. Kendeng zone as the main

depocenter received a lot of sediment contribution from Southern Mountain Zone to the south and

Rembang zone to the north.

Therefore these turbidite sequences predominantly composed mixed of siliciclastic, volcaniclastic and

even carbonate content (Smyth et al, 2005;

Subroto et al, 2007). Paleocurrent analysis shows that sand supply came from the NW towards SE,

most likely from Rembang High and was deposited

into Kendeng low. The 3D modeling could depict the architectural element of deep water fan

complex, focusing on sandy facies formation that

Figure 6. Paleocurrent analysis as measured from grove (top) and flute cast (bottom) structures yielded NW-SE depositional trend.

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has a significant implication to reservoir geometry

(Figure 7). Middle fan sandstones are rarely found in the study area, as only 10 out of 130 sand

bodies were identified as middle fan deposit whose

thin section results showed that they are wacky sandstones. The thickness slice of 3D modeling

yields the mean thickness-width ratio of massive

sand bodies 1:1300 m, with porosity of around 0.03 to 0.15. Therefore, it is mostly considered to

be a precisely analog of turbidite reservoir in the

Western Kendeng. There are 120 existing sand bodies in the study area which are interpreted as

part of the lower fan lobe. They are composed of a

thin sheet sands interbedded pelagic mud with

mean thickness-width ratio analyses from horizontal slice of 3D sandbodies modeling 1 : >

2000 m. However, lower fan sands have not been

considered eligible to be reservoir analog due to poor rock property values (porosity ranges from

0.01 to 0.05), quite thin sand and rich in clay

mineral (Figure 8).

Deep water processes in western Kendeng Zone

has produced a variety of stacking turbidite sands. Two-dimensional correlation reveals fan lobes

switching in this area. They have compensational

stacking character which fans are vertically migrated due to high accommodation space with

balanced sedimentation rate (Mutti and Davoli,

1992). Meanwhile the sheet sands are significantly retrogradely-stacked in lower Kerek Formation,

which are continuously-distributed to overall area,

and they represent lower fan lobe sands, although in some place only a half part of the lobes is

discovered. It probably proves the lobe geometry is

greater than expected during study. Beside in the

upper part of the Kerek Formation, the sand lobes tend to be thinner and smaller. This study might

be useful to provide turbidite reservoir analogue

model for subsurface application and for future hydrocarbon exploration in the western Kendeng

Zone.

A B

C Index MapKJ-13

KJ-92

KJ-98

KJ-100

KJ-85

Paleocurrent

Figure 7. A) 3D model showing the succession of deepwater fan facies sandbodies. B) Thickness-oriented slice within sandstone sheets of lower fan lobe and C) Thickness-oriented slice of pebbly massive.

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ACKNOWLEDGMENT

This study is part of the author‟s thesis, which was

supported by Department of Geology UPN”Veteran”Yogyakarta, PT Seleraya Energy and

GeoPangea Research Group. Special

acknowledgment is made for Riswa Galena and

MM team as partners on the fieldwork, Leon Taufani and Agung Budiman for good discussion,

UPN geology laboratories for samples analysis and

FOSI to publish this article. REFERENCES

Bouma, A. H., 1962, Sedimentology of Some Flysch Deposite, A graphic approach to fasies

interpretations: Elsevier Co., Amsterdams,

Netherlands. Bouma, A. H., 2000, Coarse-grained and fine-

grained turbidite systems as end member

models: applicability and dangers: Marine and petroleum Geology , Elsevier.

De Genevraye, P., and Samuel, L., 1972, Geology

of the Kendeng Zone (Central & East Java): Proceeding Indonesia Petroleum Association,

First Annual Convention, Jakarta, Indonesia.

Mutti, E., and Davoli, G., 1992. Turbidite

sandstones: AGIP, Istituto di geologia, Università di Parma.

Shanmugam, G., 2005, Deep-Water Processes and

Facies Models: Implications for sandstone petroleum reservoirs: Handbook Of Petroleum

Exploration And Production 5, Department of

Earth and Environmental Sciences The University of Texas at Arlington Arlington,

Texas, U.S.A.

Smyth, H., Hall, R., Hamilton, J.P., and Kinny, P., 2003, Volcanic origin of quartz-rich sediments

in East Java: Proceedings Indonesian Petroleum

Association 29th Annual Convention & Exhibition, Jakarta.

Smyth, H., Hall, R., Hamilton, J., and Kinny, P.,

2005, East Java: Cenozoic Basins, volcanoes

and ancient basement: Proceedings Indonesian Petroleum Association 30th Annual Convention,

Jakarta.

Subroto, E.A., Noeradi, D., Priyono, A., Wahono, H.E., Hermanto, E., Praptisih and Santoso, K.,

2007, The Paleogene Basin within the Kendeng

Zone, Central Java Island, and implications to hydrocarbon prospectivity: Proceedings

Indonesian Petroleum Association 31st Annual

Convention & Exhibition, Jakarta.

1

2

3

4

5

6

7

8

9

10

Mean

Median

Modus

Max

Min

1.2 7310

0.25 1403

-

4585.6

4630

-

3012

7265

0.607

0.515

Massive Sandstone Fasies Geometry

0.5

Based on 2D CorelationBased on 3D Fance

Diagram

0.35

Sandstone Layer

Length (m)

0.46

1580

14030.53

0.25

1

Datum N16

1.2

0.65

7310

3950

Distribution of sands

bodies (m)Thicknes (m)

28450.68

5800

5310

5316

3645

0.45

0

10

20

30

40

50

60

70

KJ 9 KJ 13 KJ 98 KJ 100

Calcareous Sandstone

Calcareous Mudstone

Measuring Section

%

(%) Lithology :

Sand-Shale Thickness Percentage in respectively section

A B

C

Figure 8. A) 3D sandbody modeling. B) Example statistics of massive sandstone facies sandbodies. C) Sand-shale percentage from several sedimentological logs.

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A Case Study on Using Mundu-Paciran Nannofossil Zones (MPNZ) to subdivide Mundu and Paciran Sequences in the MDA Field, East Java Basin, Indonesia Azhali Edwin, Kian Han and Wildanto Nusantara

Husky – CNOOC Madura Limited

Corresponding Author: [email protected], [email protected] and [email protected]

ABSTRACT

The Husky-CNOOC Madura Limited (HCML) MDA-4 exploration well (2011) in the Madura Strait region targeted Globigerina limestones in the Mundu Sequence (3.8 Ma) and the Paciran Sequence (2.0 Ma). The MDA Field is covered by Merpati 3D Seismic (2005). Seismic features observed from the 3D volume include phase change or polarity reversal at the top of gas filled reservoirs of the MDA structure and DHI flat-spot approximating to the gas-water contact (GWC). The reservoirs are primarily planktonic foraminifera grainstones, packstones and wackestones that have been deposited as pelagic rains and were subsequently redistributed by sea floor bottom currents.

Differentiating the Mundu and Paciran Sequences relies heavily on biostratigraphy and chronostratigraphy, as there are no significant lithological features that can be observed between the sequences. This article introduces a method to construct detailed well correlations of the two sequences based on Mundu–Paciran Nannofossil Zones (MPNZ), using high resolution biostratigraphy events. The methodology uses varying nannofossil abundances in the interval NN18 (Late Pliocene) to NN11 (Late Miocene). The best reservoir performance in the study area may occur in the MPNZ-7 and MPNZ-6, which were deposited at the late stage of the depositional cycles.

INTRODUCTION

The Madura Strait Block (Madura Strait PSC) has

a long history of exploration with the first well

drilled back in 1970 (MS-1-1, dry hole, Cities Service Inc.). The last exploration well drilled

before the block was acquired by Husky – CNOOC

Madura Limited in 2008 was the MDA-3 well (1992, dry hole, MOBIL Madura Strait Inc.). The

MDA-3 was an appraisal well delineating a

reservoir boundary at the north of the MDA Structure.

Following a period of 19 years without exploration activity within the block, the MDA-4 exploration

program was proposed and initiated during 2011

(Figure 1). The MDA-4 targeted the Globigerina limestones of the Mundu and Paciran Sequences.

This well was a discovery, confirming a gas field

and provided support for considering potential

development options. Work continued with Project Engineering & Design (PED) preparation and

approval. The final Plan of Development (POD) was

approved by GOI in January 2013; two years after the well was drilled. This is possibly the fastest

cycle of discovery to POD approval in the region.

Figure 1. Madura Strait PSC Block.



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The Mundu Sequence (3.8 Ma) and Paciran

Sequence (2.0 Ma) (in East Java-Madura lithostratigraphy terminology they were known as

Mundu and Selorejo Formations, respectively),

consist primarily of planktonic foraminifera grainstones, packstones and wackstones. They are

considered to have been deposited as pelagic rains

and were subsequently redistributed by sea floor bottom currents. Differentiating the Mundu and

Paciran Sequences relies heavily on

biostratigraphy and chronostratigraphy as no significant lithological features can be observed

from samples and logs between those two

sequences. Detailed well correlation of MDA wells

was generated based on Mundu–Paciran Nannofossil Zones (MPNZ), using high resolution

biostratigraphy events. The methodology uses

varying nannofossil abundances in the interval NN18 (Late Pliocene) to NN11 (Late Miocene).

REGIONAL GEOLOGY

The Madura Strait Block is located in the southern

part of East Java Basin; a back-arc basin bounded to the west by Karimunjawa Arch and to the south

by Java Volcanic Arc (Satyana et al., 2004; Figure

2). The basin deepens eastwards into the Lombok Basin while to the north of the basin shallows to

become the Paternoster High (Satyana and

Djumlati, 2003). The block is located in an offshore

area between Madura Island to the north and the present-day East Sunda volcanic arc to the south.

The offshore area of East Java demonstrates an excellent example of Miocene – Recent structural

inversion of a Paleogene

extensional/transtensional basin system. The continued inversion and differential compaction

during Plio – Pleistocene time is a further primary

control on sedimentation. Seismic data show a complex structurally controlled sequence

stratigraphy (Bransden and Matthews, 1992).

There are several reservoir objectives in the area,

ranging from Eocene to Pliocene in age. The HCML

MDA-4 well is one of many proposed exploration

wells, targeting the Late Miocene – Late Pliocene reservoir (Figure 3). This foraminifera-dominated

reservoir was encountered in many exploration

wells in the East Java Basin and also developed in several onshore East Java areas.

Schiller et al (1994) suggested that there are at least two distinct types of Globigerina

sand/limestone deposits in the East Java Basin,

i.e.: planktonic foraminifera sands “drifts” deposited by bottom currents, which he considered

as the dominant process; and less pervasive

planktonic foraminifera “turbidites” deposited as

submarine channel-fills and fans. The Globigerina limestone (GL limestone) in the MDA-4 well was

interpreted as the result of pelagic rain deposition

and subsequently redistributed by sea floor bottom currents. This process is similar to the “planktonic

foraminifera sand „drifts‟ deposited by bottom

currents” that was proposed by Schiller et al

(1994).

MDA FIELD The MDA Field was discovered in 1984 by the

Hudbay MDA-1 exploration well, drilled on a crest

at the eastern part of the structure. This well was drilled to 4,016 feet subsea and tested 28

MMSCFD of gas. The discovery was confirmed by

the MDA-2 exploration well, which was located about 250 m southwest of the MDA-1. The MDA-3

appraisal well was drilled at the northern edge of

the structure; approximately 2 km northwest of the MDA-1 and MDA-2. The objective of the MDA-3

was to confirm a possible gas water contact at the

northern edge of the field. The well was considered

a dry hole due to poor reservoir quality.

The MDA-4 appraisal well was drilled in 2011 and it successfully confirmed MDA Field‟s gas reserve.

The well tested gas flow rates of 18.7 MMSCFD

from Pliocene reservoir (Paciran Sequence) and 8.3 MMSCFD from Pleistocene turbidite reservoir of

the Lidah Sequence.

SEISMIC CHARACTERISTICS

The MDA Field is covered by 80 sq.km of marine 3D seismic, which was acquired as part of a much

larger Merpati 3D survey in 2005. In 2009, the

data was reprocessed through Pre-Stack Time Migration (PSTM) and Pre-Stack Depth Migration

(PSDM).

All seismic sections in this article are displayed on zero phase data and following SEG convention, in

which positive reflection coefficient is displayed as

peak and negative coefficient as trough.

Two Direct Hydrocarbon Indicator (DHI) features

observed on the MDA structure, a polarity reversal at the top gas-filled reservoirs and a seismic flat-

spot indicating the gas-water contact. These

features helped reduce geological risk and increase confidence to drill.

RESERVOIR LITHOLOGY AND NANNOFOSSIL BIOSTRATIGRAPHY

The reservoir rocks in the MDA Field consist of the Mundu and Paciran Sequences (Figure 3). The

sequences and chronostratigraphic labels follow

the convention and descriptions of Goodall (2007). The Mundu Sequence is bounded by the T40 and

T50 sequence boundaries (7.3 and 3.8 Ma,

respectively). The Paciran Sequence is bounded by the T50 and T60 sequence boundaries (3.8 and 2.0

Ma, respectively). Within both sequences, there are

series of bioclastic grainstones, packstones and

wackestones. These reservoirs are in age equivalent and have the same lithologies as

SANTOS‟ Maleo Field (Triyana et al, 2007).

Oil

field

Gas f

ield

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The foraminifera association of both sequences

indicates that the water depth is approximating to the range 100-500 m, where planktonic

foraminifera were deposited as “pelagic rain” and

then were subsequently redistributed by sea floor

bottom currents. This process resulted in the grainstone, packstone, wackestone observed in the

wells to show distinct, rhythmic coarsening-

upward cycles. A similar depositional process took place in SANTOS‟ Oyong and Maleo Fields (Iriska

et al., 2010), which are located 150 km and 70 km,

respectively, to the west of the HCML MDA Field.

Differentiating these Mundu and Paciran

Sequences relies heavily on biostratigraphy and chronostratigraphy, as there are no significant

lithological features that can be observed from

samples and logs of those two sequences. The

methodology used was initially invented and developed by Goodall (2007), with varying

nannofossil abundance relative to sequence

boundaries in the interval NN18 (Late Pliocene) to NN11 (Late Miocene) helping to define a rigid

stratigraphical framework.

The detailed correlations in the MDA Field were

constructed using high resolution biostratigraphy events of the Late Miocene- Pleistocene MPNZ

(Mundu – Paciran Nannofossil Zones). This method

is generated based on cutting data from four wells

and also conventional cores of MDA-3 and MDA-4. The subdivisions are as follows (the youngest zone

is mentioned first):

MPNZ-8: Pleistocene age bounded by T60 and T65.

MPNZ-7: The first downhole occurrence of Discoaster brouweri with less abundant

Sphenolithus abies and any other nannofossil. This

zone has reworked materials from older

stratigraphy.

MPNZ-6: The first downhole occurrence of

common-abundant small Reticulofenestrids and in-situ Sphenolithus abies is used to date this event.

The absence or significantly decreased (downhole)

occurrence of Gephyocapsa is also noted in this

subzone.

Figure 3. East Java Basin chronostratigraphy.

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MPNZ-5: This event is recognized by the first

downhole occurrence of (super) abundant small Reticulofenestrids.

MPNZ-4: Defined by the first downhole occurrence of few-common Sphenolithus abies and/or medium

Reticulofenestrids. The first downhole occurrence

of few-common Dictyococcites spp also

characterizes the event.

MPNZ-3: This event is marked by the first

downhole occurrence of abundant Sphenolithus abies.

MPNZ-2: This event is characterized by the

maximum abundance of Reticulofenestrids and/or Sphenolithus abies during the Early Pliocene.

MPNZ-1: This event is coincident with the first downhole occurrence of in situ Discoaster quinqueramus (also used to mark the Late Miocene

- Pliocene boundary) and the first downhole

occurrence of Reticulofenestra rotaria. A downhole significant increase of medium Reticulofenestrids

and the absence of in-situ Dictyococcites spp. are

also noted at this subzone.

CONCLUDING REMARKS Inversion in Madura Strait region that took place

in the Late Miocene created “humps” on the sea

floor. The forams were deposited as “pelagic rain”

and were re-distributed in the area by strong currents coming from the Indian Ocean through

the Bali Strait. These currents created a clinoform

structure around the seabed located at relatively higher position from its surrounding. The evidence

of this clinoform can be seen at MPNZ-6

relationship between MDA-1 and MDA-2st wells

(Figure 5).

Based on the MPNZ subdivision, the top of MPNZ-7

in the MDA Field occurs within the Selorejo Formation (Figure 6). The Selorejo Formation is

based on lithostratigraphy, which means the

formation top does not necessarily coincide with time event. The upper reservoir interval of the MDA

Field is younger than the MPNZ-7 and it lies within

the lower part of MPNZ-8 (Lidah Sequence, Late Pliocene - Early Pleistocene). This interval was

interpreted as part of reworked materials from

older deposits.

The MPNZ-7 was only encountered in the MDA-3

(northern edge of the structure) and MDA-4

(western portion of the structure), which is believed to be composed of reworked sediments

from the eastern portion of the structure. This

interpretation is supported by the fact that MPNZ-7 deposit was not encountered in MDA-1 and

MDA-2ST (Figures 4, 5 and 6).

Based on internal reservoir characteristics, the

MPNZ-7 deposit in MDA-3 has less porosity and

permeability compared to similar reservoir in the

MDA-4; and this corresponds to the increase of mud content in the MDA-3. Hence, the facies

changes relative to the west of the structure during

MPNZ-7 time. It is interpreted that the MDA-3 reservoir was deposited by less winnowing

compared to the reservoir in the MDA-4, due to the

relatively low position in the structure.

Based on the above interpretation, it is suggested

that the best reservoirs are the MPNZ-7 and MPNZ-6, which were deposited at relatively high

position in the depositional setting.

Figure 4. Seismic amplitude cross section showing top MPNZ 7 and MPNZ 6 with facies change between MDA-4 and MDA-3 (MPNZ 7 age) and MDA-1 and MDA-4 (MPNZ 6 age).

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ACKNOWLEDGEMENTS

We would like to thank Budiyento Thomas and

Joint Venture of Husky – CNOOC Madura Limited for permission to publish this article; Jeffery

Goodall, Arnie Ferster and Fernando Gaggino for

reviewing this article. Discussions and comments from them have significantly improved this article.

REFERENCES

Bransden, P. J. E., and Matthews, S. J., 1992,

Structural and Stratigraphic Evolution of The

East Java Sea, Indonesia: Proceedings Indonesian Petroleum Association 1992.

Goodall, J. G. S., 2007, Madura Basin

Stratigraphic Study, Joint BPMigas/Santos internal study.

Iriska, D. M., Sharp, N. C., and Kueh, S., 2010,

The Mundu Formation: Early Production

Performance of An Unconventional Limestone Reservoir, East Java Basin – Indonesia:

Proceedings Indonesian Petroleum Association

2010. Satyana, A. H., and Djumlati, M., 2003, Oligo-

Miocene Carbonates of the East Java Basin,

Figure 5. AI cross section showing top MPNZ 7 and MPNZ 6 with facies change between MDA-4 and MDA-3 (MPNZ 7 age) and MDA-1 and MDA-4 (MPNZ 6 age).

Figure 6. Well correlation between MDA wells.

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Indonesia: Facies Definition Leading to Recent

Significant Discoveries: AAPG International Conference 2003.

Satyana, A.H., Erwanto, E., and Prasetyadi, C.,

2004, Rembang-Madura-Kangean-Sakala (RMKS) Fault Zone, East Java Basin: The Origin

and Nature of a Geologic Border, Indonesian

Association of Geologists 33rd Annual Convention, Bandung 2004.

Schiller, D. M., Seubert, B. W., Musliki, S., and

Abdullah, M., 1994, The Reservoir Potential of Globigerina Sands in Indonesia: Proceedings

Indonesian Petroleum Association 1994.

Triyana, Y., Harris, G. I., Basden, W. A., Tadiar, E., and Sharp, N. C., 2007, The Maleo Field: An

Example of The Pliocene Globigerina Bioclastic

Limestone Play In The East Java Basin – Indonesia: Proceedings Indonesian Petroleum

Association 2007.

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Short Note : Mineral Composition of Eocene and Miocene Sandstones in Java Island

Herman Darman1, Budi Muljana2 and J. T. van Gorsel3

1Shell International EP – Netherlands 2Geology Department, University of Padjadjaran – Indonesia 3Geoscience Research / Consultant


INTRODUCTION A number of studies discuss the mineral

compositions of Cenozoic sandstones in Java

Island, Some sandstones are dominated by quartz, derived from granitic and/or metamorphic

basement terrains or reworked sediments; many

others are dominated by lithics and plagioclase feldspars derived from andesitic volcanics. The

distribution of these two end-members varies

through space and time, and has not been systematically been document for all of Java.

In the first comprehensive study of the geology of

Java, Verbeek and Fennema (1896) suggested that most of the Neogene sandstones on Java were

erosional products of volcanic rocks, and that

quartz-rich sandstones were either of Eocene age or were deposited in the proximity of Eocene rocks.

Rutten (1925), however, studied 110 Neogene sandstones across Java and demonstrated that

many of the Miocene sandstones are also rich in

quartz, particularly across the northern half Java Island and on Madura Island (Figure 1). These

have common 'dusty quartz' and quartz with

undulose extinction patterns (both indicative of

metamorphic quartz), and were interpreted as clastic material derived from 'old rocks of Sunda-

land'. He also observed that grain sizes of Neogene

sands generally decrease in Southern direction and that andesitic material is not common before

the Late Neogene (probably meaning Late Miocene

and younger).

More recent work in West Java by Clements and

Hall (2007) and Clements et al. (2012) largely confirmed the patterns established by Rutten

(1925):

(1) Sandstones of Eocene and Oligocene age across all of West Java are virtually all quartz-rich, and

can be tied to 'Sundaland' Pre-Tertiary granite

and-metamorphic basement sources North of Java;

(2) Increase in volcanic detritus in Early Miocene

and younger sandstones, particularly in South Java and the axial basins, where all sandstones of

this age are typically sourced from the Late

Oligocene – Early Miocene "Old Andesites" volcanic arc of the Southern mountains and the Late

Miocene- Recent modern arc across the axial zone

of Java.

Smyth et al. (2008) provided additional detail on

sandstone composition from East and Central Java. They essentially confirm the same patterns

as in West Java, but found that some of the Lower-

Middle Miocene sediments in the Southern Mountains are quartz-rich, but are composed of

volcanic quartz (monocrystalline, clear, often

bipyramidal) and are sourced from local acid

volcanic rocks.

The purpose of this short note is to contribute to

the subject of Java sandstone provenance by summarizing quantitative analyses on sandstone

compositions in the recent studies by Muljana &

Watanabe (2012), Darman (1991), Siemers et al (1992) and Smyth et al (2008) and provide some

additional data points as QFL (Quartz- Feldspar-

Lithics) ternary plots. SANDSTONE GROUPS BASED ON MINERAL COMPOSITIONS

There are two groups of sandstones based on their composition: a) Non-quartz dominated sandstones

and b) Quartz dominated sandstones.

Non-quartz dominated sandstones are found in

West and Central Java (G & F, Figure 1). Muljana

& Watanabe (2012) studied the Miocene Cinambo and Halang formation in Majalengka area, West

Java. The quartz composition decreases from the

lower to middle Miocene followed by increasing of rock fragment (Figures 2A and 2B). The rock

fragment composition was dominated by andesite

fragments. These sandstones were deposited when the magmatic and tectonic influences are

particularly dominant. The upper Miocene Halang

Formation is distinguished by the volcanic content.

Darman (1991, Figure 2C) studied the upper

Miocene Halang Formation in the north of Central

Java and here the sandstones have a lower quartz content. The majority of the rock fragments are

volcanics and are rich in plagioclase minerals.

Similar to the Majalengka area, the Halang Formation is a turbidite deposit.

Based on the Dickinson classification diagram (1985, Figure 2D) some of the Lower Miocene

sandstone were derived from a recycled orogeny

terrain. The upper Miocene Halang Formation

sandstones in both Majalengka and Brebes came from a range of sources such as dissected to

undissected arc in the south to southeast of the


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area.

The sandstones compositions of the Bayah

Formation (A, Figure 1) and the Walat Formation (B, Figure 1) of SW Java are dominated by quartz

(Figure 3). These formations were deposited during

Eocene time (Siemers et al, 1992). The outcrop analysis indicated a mix of fluvial and shallow

marine sandstones. In Central and East Java,

Smyth et al (2008) also found a number of quartz-

rich sandstones. The provenance of these sandstones are interpreted as recycled orogen

terrain in the north to northeast of the outcrops.

In the southern part of Central Java, Smyth et al

(2008) found metamorphic quartz rich sandstone

(Figure 4A), deposited in a terrestrial environment

during pre-Middle Eocene time, classified as Type

1, in 3 locations (C in Figure 1). These are pre-

middle Eocene sandstones and described as metamorphic quartz-rich sedimentary rocks,

deposited in terrestrial environment

In the Southern mountains Miocene volcanic

quartz-rich sandstones were found in outcrops.

Smyth et al (2008) classified these sandstones as

Type 2 (Figure 4B), which are located in close proximity to the acid volcanic centers of the

Eocene to Lower Miocene Southern mountain arc

(Location D, Figure 1). The presence of lignite, channel structures and abundant rootlets, and the

lack of marine fauna indicate a terrestrial

depositional setting (Smyth et al, 2008).

Figure 2. Quartz, Feldspar and Lithics ternary plot of sandstones from the Halang Formation. A and B are from Majalengka, West Java and C is from Central Java. D is the provenance categories of sandstone based on Dickinson (1985).

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Figure 3. Quartz dominated sandstones of Bayah and Walat Formation, Southwest Java (Siemers et al, 1992).

Figure 4. Quartz dominated sandstones in Eastern Java based on Smyth et al, 2008. A) Type 1, B) Type 2 and C) Type 3 sandstones.

of 40



Mixed provenances of the Middle Eocene to

Miocene sandstone (E, in Figure 1) are common in the eastern part of Java. Smyth et al (2008) call

these sandstones as Type 3 (Figure 4C). In the

Southern mountain area these Type 3 sandstones are Middle Eocene in age, and part of the

Nanggulan Formation. Smyth also found quartz-

rich sandstone in a small outcrop in the Kendeng Basin, north of Central Java. Although it was

found in Miocene Lutut Beds, it has been

deposited on the southern margin of the basin and have subsequently been deformed and moved

northwards to their present-day position by

thrusting (Smyth et al, 2008). Additional Type 3

sandstones are found in Northeast Java, in the Middle Miocene Ngrayong Formation.

These 3 groups of sandstones described by Smyth et al (2008), mainly fall in the "Recycled Orogen"

category in the QFL diagram of the Dickinson

(1985) classification. Some of the Type 3 sandstones plot in the "Craton Interior" category of

provenance. However, the quartz-rich Type 2

sands are clearly of volcanic origin, demonstrating to not rely exclusively on these ternary plots for

sandstone provenance interpretation (a point

already stressed by Smyth et al. 2003, 2008).

CONCLUSION

Quartz rich sandstones are common in the Eocene

interval across Java, in the Miocene of the northern part of Java Island. Feldspar and

volcanic rock fragments are more dominant in

most other Miocene sandstones.

Sandstones from the Late Miocene Halang

Formation in northwest Java are dominated by

feldspar and rock fragments. The observation in Majalengka shows the reduction of quartz from the

lower to upper Miocene interval.

ACKNOWLEDGEMENT

The authors would like to thank those who contributed to the discussion through personal e-

mail or FOSI LinkedIn network: Ma'ruf Mukti,

Fadhel Irza, Arif Rahutama and Iqbal Fardiansyah.

REFERENCES

Clements, B., and Hall, R., 2007, Cretaceous to

Late Miocene stratigraphic and tectonic

evolution of West Java: Proc. 31st Ann. Conv. Indon. Petrol. Assoc. IPA07-G-037, 87-104.

Clements, B., Sevastjanova ,I., Hall, R., Belousova,

E.A., Griffin, W.L., and N. Pearson, N., 2012, Detrital zircon U-Pb age and Hf-isotope

perspective on sediment provenance and

tectonic models in SE Asia. In: E.T. Rasbury et al. (eds.) Mineralogical and geochemical

approaches to provenance: Geol. Soc. America

Spec. Paper 487, 37-61. Darman, H., 1991, Geologi dan Stratigrafi Serta

Studi Mineralogi Formasi Halang, Daerah

Bantarkawung dan Sekitarnya, Kabupaten

Brebes, - Jawa Tengah, BSc Thesis. Dickinson, W. R., 1985, Interpreting Provenance

Relations from Detrital Modes of Sandstones, G.

G. Zuffa (ed.) Provenance of Arenites NATO ASI Series, C 148: D. Reidel Publishing Company,

Dordrecht, 333–363.

Muljana, B., and Watanabe, K., 2012, Modal and Sandstone Composition of the Representative

Turbidite, from the Majalengka Sub-Basin, West

Java: Indonesia Journal of Geography and

Geology Vol. 4, No. 1, 3-17. Rutten, L., 1925, On the Origin of the Material of

the Neogene Rocks in Java: Koninklijke

Akademie van Wetenschappen te Amsterdam, Proceedings Vol. XXIX, 1, 15-33.

Siemers, C. T., Kleinhans, L. C., and Young, R.,

1992, SW Java Field Trip / Core Workshop: Indonesian Petroleum Association Post

Convention Field Trip guide book.

Smyth, H., Hall, R., Hamilton, J., and Kinny, P., 2003, Volcanic origin of quartz-rich sediments

in East Java: Proc. 29th Ann. Conv. Indon.

Petrol. Assoc. 1, p. 541-559.

Smyth, H., Hall, R., and Nichols, G. J., 2008, Significant Volcanic Contribution to Some

Quartz-Rich Sandstone, East Java: Journal of

Sedimentary Research, v. 78, 335–356.Van Bemmelen, R. W., 1949. The Geology of

Indonesia, Vol. 1A, Martinus Nijhof, The Hague

Verbeek, R.D.M., and Fennema, R., 1896, Geologische beschrijving van Java en Madoera:

J.G. Stemler, Amsterdam, 2 vols + Atlas, 1135

p.

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