International Proceedings of Chemical, Biological and Environmental Engineering, V0l. 101 (2017) DOI: 10.7763/IPCBEE. 2017. V101. 15 Hydrocarbon Prospectivity of Cendrawasih Bay Area Citra Nurwani 1, Zulfikar Imran 2, Chalid Idham Abdullah 3, Suci Nurmala Mulyati 1, Dicky Rahmadi Aprillian 1 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. 106
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] 107
(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 108
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. 109
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]. 110
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. 8. References [1] BPMIGAS, "Unpublish Report Study Petroleum Basins of Indonesia," 2008. [2] F. Hinscheberger, J.-A. Malod, J.-P. Réhault, M. Villeneuve, J.-Y. Royer and S. Burhanuddin, "Late Cenozoic Geodynamic Evolution of Eastern Indonesia," Techtonophysics, vol. 404, no. 1, pp. 91-118, 2005. [3] B. Sapiie, A. Adyagharini and P. Teas, "New Insight of Tectonic Evolution of Cendrawasih Bay and Its Implication for Hydrocarbon Prospect, Papua, Indonesia," Proceeding Indonesian Petroleum Association, 2010. [4] D. D. B. and S. R., "Western Irian Jaya: The end-product of oblique plate convergence in the late tertiary," Tectonophysics, vol. 106, no. 1, pp. 109-139, 1984. [5] N. Petroleum, "Yapen Block Unpublished Relinquishment Report to BPMIGAS," Jakarta, 2009. 111
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