Hydrocarbon Prospectivity of Cendrawasih Bay Area

Citra Nurwani 1

, Zulfikar Imran 2, Chalid Idham Abdullah

3, Suci Nurmala Mulyati

1, Dicky

Rahmadi Aprillian1

1 SKK Migas

2 Repsol Exploracion

3 Institute Technology Bandung

Abstract. Cendrawasih Bay area is one of area in eastern Indonesia with hydrocarbon prospect, it covers

Cendrawasih Basin and North Waipoga/Memberamo Basin. Several wells have been drilled in this area since

1973 resulted hydrocarbon indication, either oil and gas show and gas. Those wells drilled with Memberamo

Formation and Makats Formation as their primary target, some targets show moderate maturity hydrocarbon.

The result of drop core oil analysis and geochemistry analysis help the identification of source rock maturity

which is show that the best reservoir and source rock in this area is Memberamo Formation (Memberamo-E).

Existing exploration data shows that this area have maturity problem. 3D seismic acquisition and processing,

geological modelling, drop core oil analysis and geochemistry analysis could identified more about the

maturity and organic content of the hydrocarbon source rock. This area have a high potential of hydrocarbon,

weather thermogenic or biogenic.

Keywords: cendrawasih, eastern Indonesia, hydrocarbon, prospectivity, memberamo

1. Introduction

Cendrawasih Bay area is one of area in eastern Indonesia with hydrocarbon prospectivity. Many blocks

are awarded in this area so the exploration activity still active until today. Based on BPMIGAS research on

2008, there are two sedimentary basins in this area: Cendrawasih Basin and Memberamo Basin. The

exploration activity is more active on the Memberamo Basin which also known as North Waipoga Basin.

Presumably the Memberamo Basin/ North Waipoga was formed at the site of an earlier subduction

system and interpreted to be a hybrid fore-arc basin which initiated as a fore-arc basin floored by oceanic

crust. It is also named as Paleogene Oceanic Fracture-Neogene Transform Margin Basin [1], [2].

Several wells have been drilled in this basin since 1973 and some of wells resulted hydrocarbon

indication. The basement of the basin is assumed to be part of Early Tertiary collision zone between

Australian plate to the south and Caroline collision zone to the north which consist of metamorphic and

igneous rocks. Proven reservoir is Turbidite Sandstone of Pliocene-Pleistocene Memberamo Formation and

the source rock is shale of Makats Formation [1]-[4].

Based on the P-1 well, the principal source of sediments was an island arc massif that had been uplifted

during collisional orogeny, and the oldest post collision sediments recorded in the northeast area of

Cendrawasih Bay are the Paleocene-early Miocene Auwewa formation. Numerous gas seeps have been

identified as thermogenic gas, biogenic gas, and oil and gas.

This paper explains about petroleum system and hydrocarbon prospectivity in Memberamo Basin based

on last exploration data and activity.

Corresponding author. Tel.: +622129241607.

E-mail address: cnurwani@skkmigas.go.id.

International Proceedings of Chemical, Biological and Environmental Engineering, V0l. 101 (2017)

DOI: 10.7763/IPCBEE. 2017. V101. 15

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2. Method of Study

This study is an integrated study of geological and geophysical data and interpretation from several data,

report and publication. Those integrated data will lead into one conclusion of the petroleum prospect of

Cendrawasih Bay.

The well data was provided by Nations Petroleum [5] and analysed manually with correlation well

logging methods and also cutting analysis. Drop core and geochemistry analysis was provided by Repsol

Exploracion [6], it is consist of geochemical characterization of two piston core extracts by Weatherford and

heat flow report from GDV Indonesia. Geochemical characterization of two piston core extracts were

analyzed for biomarkers and diamondoids, although the immature biomarkers from modern sea-floor

sediments could complicating the study so this extracts should separate twice and rerun. Biomarkers that

used in this study are hopane, norhopane, Ts, Tm and Oleanane. Heat flow measurements could use to

identify areas of anomalous heat flow to indicate localized fluid flow and predict temperature, burial, fluid

generation and fluid transport [6]. This work also integrated all of the literature about Cendrawasih Bay and

Memberamo Area to find a new conclusion.

3. Regional Geology and Tectonic

Tectonics evolution of Papua can be divided into two parts, namely Bird Body or eastern New Guinea

and the Bird’s Head or West Papua. Both parts show strongly an E-W structural pattern, the Bird’s Head is

exposed by Kemum High while the Bird’s Body is by the Central Range. These two patterns are separated by

a relatively N-S Lengguru Fold Thrust Belt and a triangular embayment called Cendrawasih Bay (see Fig. 1)

[3], [7], [8]. While the prospectivity of hydrocarbon is located from the centre of Cendrawasih Bay to the

eastern part (Yapen offshore and Papua mainland) which situated in the rear of the eastward drifting shield of

Australian continent. This area is influenced by Sorong-Yapen fault zone which shows with mud volcanoes

through the center of Waropen-Membramo depression [7]-[12].

Fig. 1: Map of Cendrawasih Bay shows tectonic elements of Papua including Bird’s Head, Bird’s Neck and Bird’s Body

[3]

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(Sapiie, 2000) (McAdoo & Haebig, 1999)

Fig. 2: Regional stratigraphic correlation of Papua. The Cendrawasih Bay is a combination between Australian

continental crust and Pacific oceanic crust [3] [9] [10].

4. Exploration History

The first block which located in Cendrawasih Bay area were granted to Pertamina-Tesoro in 1970. The

first exploration well in Cendrawasih Bay area was start with E-1 well which located at the southern part of

Yapen Island and the primary target is Memberamo and Makats formation, but the result shows no Makats

Formation and immature source rock in the Memberamo Formation. It was plug and abandoned at 2289 m.

The second exploration well was H-1which was located only 18 km from E-1 and the primary target are

Makats Formation and Auwewa Formation. The results indicate a very poor show of hydrocarbon at 1856 m

and this well was drilled into 3596 m [1], [5].

The third exploration well named R-1 is quite promising and the target is the same as H-1 but reached

only to 2307 m. The R-1 well discovered several thin gas bearing sands from 1770-1772 meters tested 6.8

MMSCFD dry gas, meanwhile the other test were failed or inconclusive [1], [5].

The fourth exploration well is P-1which quite far from the centre of Cendrawasih Bay, near eastern

Yapen. The primary target of this well is Memberamo, Makats, and Auwewa Formation. There are several

hydrocarbons show at Memberamo formation, meanwhile only traces of hydrocarbound found at the Makats

and Auwewa Formation. This well was plug and abandoned at 4595 m [1], [5].

The fifth exploration well named O-1 was situated only 34 km to the northeast of R-1 with no show of

hydrocarbon. Next well was drilled on the centre of Cendrawasih Bay named Elang-1 the result is dry. This

result show that the migration path more likely to the eastern part which also showed by some wells in the

land resulted (Gesa-1 & Gesa-2) oil and gas [1], [5].

Sapii et al. (2010) have been published the stratigraphic unit for Cendrawasih Bay which is more

combination between Australian continental crust and Pacific oceanic crust (See Fig. 2).

Based on P-1 well, the principal source of sediments was an island arc massif that had been uplifted

during collisional orogen, and the oldest post collision sediments recorded in the northeast area of

Cendrawasih Bay are the Paleocene-early Miocene Auwewa formation [1], [5].

5. Hydrocarbon Occurrences

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5.1. Source Rock

Contributions The presence of thermogenic hydrocarbon confirms by the drop core data resulted

hydrocarbon with primarily gas and locally oil and biogenic oil (see fig. 3) [6]. while geochemistry of

extracts from some selected drop cores all contain oil derived from a Type II in early mature stage (see fig. 4)

[6]. However, the TOC value from cutting samples of Iroran-1 well is fairly high, on average 2% in the

shales of Memberamo D and 3% in Makats formation and in Otus-1, the possible source rock is

Memberamo-E which contains varied value of organic carbon content, from good to excellent (2-12.17%)

[1], [5]. While the pyrolysis data show that Memberamo-E have fair to very good gas and good oil source

rock potential. Thermal maturity evaluation by the basis of vitrinite reflectance measurements and pyrolysis

Tmax readings shows that moderately mature oil rocks are encountered [1], [5], [6].

Fig. 3: Drop Core Oil Analysis consist of UCM, TSF, T/D ratio and drop core gas analysis consist of Total Alkane,

Ethane/Ethene ratio, and Methane Ratio. Drop core confirm the presence of thermogenic hydrocarbon with

primarily gas, locally oil and biogenic gas.

Fig. 4: Geochemistry analysis which conducted from seeps sample show the kerogen type for the source rock is Marine

type II.

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5.2. Reservoir

All Sandstones from Auwewa Formation, Darante Formation, Makats Formations, and C-Memberamo

Formation could be good enough reservoirs, while limestone and sandstone from D-memberamo are better

(17-37%), but the best reservoir in this area are Darante Formation and B-Memberamo [1]. One of the

proven reservoir is Late Pliocene Memberamo formation with thinly bedded fine to medium grained and

consist of 50% quartz grain with volcanic rock fragment and porosity occlusion (see fig. 5).

Fig. 5: core porosity vs permeability as reservoir quality description in four well (Otus-1, O-1, P-1, and R-1. The

porosity and permeability are varied but moderately it between 17.5 to 30 and 1 to 50 md. The reservoirs are

thinly bedded fine to medium grained and porosity inclusion with some calcareous material with fair

porosity and low permeability [5].

5.3. Trap and Migration

Trap and migration in this area is consist of Structural trap and stratigraphy trap. Stratigraphy trap will

exist in the turbidites sandstone and limestone, such as Auwewa Formation, Darante Formation, and Makats

Formation. In Niego High it formed onlap on top of the basement. Otus-1 tested stratigraphic trap onlap

against the volcanic basements rocks. Structural trap formed in anticline and normal faults resulted from

Pliocene and Pleistocene compressional phase. Both trap, structural and stratigraphic, appears to be sitting on

top of basement high (see figure 6). The timing of migration is expected occur in the Pliocene-Pleistocene, it

leads from numerous gas seeps which have been recorded at the southern area of Rombebai Block [1], [5].

5.4. Seals Interbedded Shales in Memberamo Formation could be a good seal for Makats Formations and D-

Memberamo [1].

6. Conclusion

Cendrawasih Bay area covered two basin, Cendrawasih Basin and Waipoga/Memberamo Basin. The

basin itself influences by the different factor, Cendrawasih basin is a triangular embayment which formed

caused by the tectonic evolution of Papua called Bird Body or eastern part of New Guinea [3], [10]. The

stratigraphic unit for Cendrawasih Bay which is more combination between Australian continental crust and

Pacific oceanic crust, so there is an opportunity for the hydrocarbon to be appear [3], [10], [13].

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Based on exploration data and history, the hydrocarbon occurs in the shore or near eastern mainland

Papua and in the Cendrawasih Bay Area (southern Yapen). It could be biogenic or thermogenic which appear

in the Memberamo Formation, Darant Formation, Makats Formations, and Auwea Formation with play near

basement high (weather structural or stratigraphic play). Moderate maturity of oil generations is encountered

on the Memberamo Formation and Makats Formation [1], [5], [6].

Existing exploration data shows that this area have maturity problem. 3D seismic acquisition and

processing, geological modelling, drop core oil analysis and geochemistry analysis could identified more

about the maturity and organic content of the hydrocarbon source rock [6].

Fig. 6: Petroleum system play of hydrocarbon in the Cendrawasih Area [14] Some play (structural and stratigraphic)

appears to be sitting on the basement high.

7. Acknowledgements

We would like to thanks to DITJEN MIGAS and SKK Migas for supporting this study. We would like to

thanks to Nations Petroleum, Niko Resources, and Repsol Exploracion. We would like to thanks to Dr. Fajril

Ambia ST., Mr. Awang Harun Satyana, Mr. Nizar Muhajidin, Mr. Brahmantyo K. G., Mrs. Shinta

Damayanti, and Mrs. Dessy Dharmayanti.

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