Penulis: tektonesiana

New Observations on the Evolution of the Bogor Basin, West Java: Opportunities for Turbidite Hydrocarbon Play*

Awang H. Satyana 1), Cipi Armandita 2), Budi Raharjo 2), and Ildrem Syafri 2)

[1) Exploration Badan Pelaksana Migas, Jakarta 2) Geology Dept. University of Padjadjaran, Bandung]

* Buletin Geologi Institut Teknologi Bandung – Edisi Khusus 42 Tahun Pengabdian Prof. Dr. Soejono Martodjojo, M.Sc.

Departemen Teknik Geologi, FIKTM, ITB, Bandung, 2002

ABSTRACT

Recent detailed field studies in the Sumedang area and regional re-interpretation indicated new observations on the evolution of the Bogor Basin. The basic ingredient is that the Bogor Basin in its history ever received sediments from the northern provenance of the Northern Platform. This differs with Martodjojo (1984)’s conclusions stating that all Bogor’s sediments were sourced from the south. Turbiditic sediments of the upper Middle Miocene Cinambo, lower Pliocene Subang and Bantarujeg are examples of the exposed sediments in the area sourced from the north provenance. Older north-sourced sediments than those formations may also present. Lowstand levels in the Northern Platform has eroded the Talang Akar, Baturaja, Cibulakan, and Parigi sediments. The sediments were transported southward by submarine channels through the slope area between the platform and the Bogor Basin and were deposited in ponded basins possibly formed on the slope area and as submarine fans on the floor of the basin. The Baribis normal fault deforming the slope area had accommodated the transport of these gravity-flow sediments. The fault was inverted to become a back-arc thrust verging to the north in the Pleistocene. These new observations open the windows of opportunities for hydrocarbon exploration in the Bogor Basin. This is based on the analogue with the proven productive turbidite play like that in the Makassar Strait and other deep-water plays. Prolific reservoirs and good sources of the sub-basins of the Northern Platform like those in the Pasir Putih (Pasir Bungur and Kepuh) and Jatibarang had partly been eroded in lowstand levels, transported, and deposited as gravity flow sediments within the Bogor basin. With stratigraphic and structural trap formation, sealed by good top and lateral seals, charged by hydrocarbons generated within the basin, then these transported sediments will become good hydrocarbon prospects. Detail model of sedimentology and petroleum system of the Bogor Basin is required to justify the turbidite play, then seismic surveys and exploration drilling will prove the concept. This will influence all turbidite plays in the whole Java area.

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Kontribusi Seismik Stratigrafi pada Pembenahan “Satuan Resmi Bawah Permukaan” Sandi Stratigrafi Indonesia 1996*

Awang H. Satyana**, Brahmantyo K. Gunawan**

** Badan Pelaksana Kegiatan Usaha Hulu Minyak dan Gas Bumi

* Simposium Kajian Sandi Stratigrafi Indonesia 1996, Yogyakarta, 28-29 Agustus 2002

PPIAGI – Teknik Geologi UPNVY- Pengda IAGI DIY-Jateng

SARI

Stratigrafi Bawah Permukaan memegang peranan sangat penting bagi kepentingan keilmuan seperti pemahaman evolusi cekungan sedimen maupun untuk kepentingan ekonomi seperti penelusuran formasi-formasi produktif. Untuk sampai kepada pemahaman ini, data seismik dan penafsiran seismik stratigrafi memegang peranan yang sangat penting. Sandi Stratigrafi Indonesia (SSI), baik yang diterbitkan tahun 1973 maupun tahun 1996, kelihatannya masih kurang mengakomodasi masalah stratigrafi bawah permukaan, bertentangan dengan kepentingan stratigrafi bawah permukaan yang tidak bisa disangkali lagi. SSI 1996 telah memuat Satuan Sekuen Stratigrafi, tetapi kelihatannya juga tidak berdasarkan kepada data bawah permukaan khususnya data seismik. Makalah ini mengulas kepentingan stratigrafi bawah permukaan, status saat ini tentang satuan bawah permukaan di dalam sandi-sandi stratigrafi, peranan seismik stratigrafi dalam identifikasi satuan bawah permukaan, dan beberapa usulan pembenahan Satuan Resmi Bawah Permukaan di dalam SSI 1996.

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Geochemistry and habitat of oil and gas in the East Java Basin: Regional evaluation and new observations*

Awang H. Satyana** and Margaretha E.M. Purwaningsih***

** Badan Pelaksana Kegiatan Usaha Hulu Minyak dan Gas Bumi, Jakarta; ***Department of Geology, Institute of Technology Bandung

* 31st Annual Conference Indonesian Association of Geologists, Surabaya, September 30 – October 2, 2002

ABSTRACT

A regional oil and gas geochemistry study was conducted recently based on geochemical data from around 100 wells and seeps of the East Java Basin. Geologic setting of the oil and gas occurrences were evaluated to derive their habitats. Most oils were derived from sub-oxic and oxic terrestrial to marginal marine source facies. Offshore oils are more terrestrial than those of onshore. Three genetic types of natural gases are found : thermogenic, biogenic, and mixed gases. The Paleogene Ngimbang, Lower Kujung, and Lower Tuban shales and coals are the sources of the oils and thermogenic gases. Biogenic gases were sourced by the Neogene Tawun to Lidah shales and coals. The study also evaluated the CO2 gas accumulations and found that significant high CO2 gas content are associated with thermal degradation of the Paleogene Kujung carbonates. Four trends of habitats are recognized: Ngimbang, Kujung, Ngrayong, and Mundu Trends.

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Lekukan Struktur Jawa Tengah: Suatu Segmentasi Sesar Mendatar

Awang H. Satyana**, Margaretha E.M. Purwaningsih***

**Eksplorasi Pertamina MPS, Jakarta, *** Departemen Geologi, Institut Teknologi Bandung, Bandung

Indonesian Association of Geologists (IAGI), Yogyakarta – Central Java Section

ABSTRAK

Garis pantai utara dan selatan Jawa Tengah menyempit masuk lebih ke dalam membentuk lekukan (indentasi) dibandingkan dengan garispantai utara dan selatan Jawa Barat dan Jawa Timur. Hal ini telah mengundang keingintahuan tentang asal gejala geologi ini dan akibat yang telah ditimbulkannya.

Pemeriksaan data geologi yang meliputi data gayaberat, geologi permukaan, citra satelit, dan seismik didukung analisis struktur dan tektonik regional menggiring ke pendapat bahwa sepasang sesar mendatar besar yang saling berlawanan arah dan gerak pergeserannya telah berperan penting atas pembentukan gejala geologi ini.

Kedua sesar mendatar tersebut diperkirakan mewakili dua arah elemen tektonik Paleogen Indonesia Barat yaitu arah Sumatra (baratlaut – tenggara) dan arah Meratus (baratdaya – timurlaut). Kedua sesar besar tersebut bertemu di Jawa Tengah dan telah menyebabkan perubahan geologi yang berarti. Lekukan barat garispantai Jawa Tengah di sekitar Cirebon ke arah baratlaut dipikirkan sebagai akibat sesar mendatar dekstral Pamanukan – Cilacap yang berarah baratlaut – tenggara. Lekukan timur garispantai Jawa Tengah di sekitar Semarang ke arah timurlaut diperkirakan sebagai akibat sesar mendatar sinistral Muria – Kebumen yang berarah baratdaya – timurlaut.

Kedua sesar besar tersebut telah menimbulkan pembubungan isostatik akibat massa kerak Bumi yang terdorong dan tersempitkan menuju bagian selatan Jawa Tengah. Di kawasan Cilacap – Kebumen, telah terjadi pembubungan maksimum akibat penguncian tektonik oleh bertemunya dua sesar besar itu di sebelah selatan Nusa Kambangan. Kompensasi isostatik atas pembubungan ini terjadi di bagian utara Jawa Tengah dengan tenggelamnya kerak batuan di kawasan ini. Gejala tektonik ini dipikirkan telah menyebabkan lekukan garis pantai utara dan selatan Jawa Tengah, penyingkapan kompleks batuandasar Lok Ulo – Karangsambung di sebelah utara Kebumen, penenggelaman kerak utara Jawa Tengah, dan terputusnya Jalur Pegunungan Selatan di bagian selatan Jawa Tengah.

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Evolution of the Salawati structures, eastern Indonesia: A frontal Sorong Fault deformation*

Awang H. Satyana 1), Margaretha E.M. Purwaningsih 2), and Enrico C.P. Ngantung 1)

1) Badan Pelaksana Kegiatan Hulu Minyak dan Gas Bumi, Jakarta; 2) Geology Department – Institute of Technology Bandung, Bandung

* Indonesian Association of Geologists, 31st Annual Conference, Surabaya, September 30 – October 2, 2002

 

ABSTRACT

Major Sorong Fault, a WSW-ENE trending left-lateral wrench fault terminates the Salawati Basin to the north and northwest. The fault has strongly controlled the basin’s structures since the mid-Pliocene and responsible for the present structural style of the basin. Four structural grains can be recognized : normal faults, strike-slip faults, fold-reverse fault belts, and diapiric structures. Four structural trends can be recognized : Salawati, Klasofo, Walio, and Cenderawasih trends. Based on left-lateral strain ellipsoidal analyses, the structural evolution can be grouped into four episodes commenced by the Sorong Fault initiation in the mid-Pliocene and peaked in the Pleistocene time when structures in the Sele Strait took place. Sequential shear-strain ellipsoids show that the Salawati structures evolved and rotated counter-clockwisely in constant magnitude of 25º relative to the present Sorong Fault from the mid Pliocene to the Pleistocene. Sorong Fault tectonism strongly controls the petroleum system of the Salawati Basin.

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Recent Significant Discoveries within Oligo-Miocene Carbonates of the East Java Basin: Integrating the Petroleum Geology

Awang H. Satyana**, Avicenia Darwis**

** Exploration Dept., Pertamina MPS, Jl. Medan Merdeka Timur 1A, Jakarta 10110

Proceedings Indonesian Association of Geologists (IAGI) & GEOSEA 2001 30th IAGI Annual Conference – 10th Geosea Regional Congress, Yogyakarta, September 10 – 12, 2001

ABSTRACT

Prospectivity of the Oligo-Miocene carbonates of the East Java Basin have been proven since 1970s when the Cities Service discovered oil and gas within these carbonates at the East Java Sea. However, the significance of the carbonates as oil producer have not obtained full attention until recently when un-interrupted significant discoveries within the carbonates have been reported. This resulted in hydrocarbon reserves in excess of 880 MMB oil and 600 BCF gas. Aggressive exploration is being made by oil companies pursuing the prospectivity of these carbonates both at onshore and offshore parts of the East Java Basin. The carbonates will hold future prosperity of the East Java Basin. The discoveries have also shown that old-worked basin is always open for new exploration.

Oligo-Miocene carbonates comprising the Kujung-Prupuh-Tuban-Rancak carbonates constitute the carbonate complex growing at the shelf edge areas to the southeast of the Sundaland. The carbonates trend ENE – WSW from the present onshore eastern part of the Central Java to the offshore areas north of East Java and Madura Island. The carbonates developed as platform carbonates, patchreefs, and shelf-edge reefs. Proven kitchens generating hydrocarbons trapped by these carbonates are located nearby within depression areas with mature sources range from the Eocene to the Early Miocene shales or carbonates.

The paper will summarize historical and recent exploration of the Oligo-Miocene carbonates of the East Java Basin and integrate aspects of petroleum geology including the regional geology, the carbonate sedimentology and the petroleum systems.

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Eocene Coals of the Barito Basin, Southeast Kalimantan: Sequence Stratigraphic Framework and Potential for Sources of Oil

Awang H. Satyana1, Margaretha Eka M.P.2, Moh. Imron3

1 Exploration Pertamina MPS, 2 Institute Technology of Bandung, 3 Exploration Pertamina Upstream

Berita Sedimentologi No. 17 III/2001

 

Abstract

Significant coal seams intercalate the middle Eocene siliciclastic series of the Lower Tanjung Formation of the Barito Basin, Southeast Kalimantan. The formation can be identified as composed of the seven sequences representing synrift and postrift sediments. The coals occur in the three sequences of the postrift phase with the most regional and the thickest coal seams distribute in the transition between the synrift and postrift phases. The coals were deposited within the environments from paralic to upper deltaic settings in various systems tracts including the late lowstand to early transgressive, late transgressive to early highstand, and early highstand to middle highstand.

Geochemical constraints are examined to see the possibility of the coals as sources for oil. The coals have excellent total organic carbon (TOC) of 44 – 73 %, very good hydrogen index (HI) from 285 – 567 mgHC/gTOC (averagely 425 mgHC/gTOC) and high elemental hydrogen to carbon ratio (H/C) of 0.87 to 1.18 concluding that the coals are liptinitic and can generate oil. These values are much higher than the cut off values established for coal to act as oil source (HI of 200 and H/C of 0.80). Geochemical correlation using carbon isotope and biomarker fingerprinting results in positive correlation meaning that the Tanjung coals have sourced the Tanjung oil. The coals may have substantial potential as sources of oil if the coals are volumetrically important.

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Origin of Pliocene Deep-Water Sedimentation in Salawati Basin, Eastern Indonesia: Deposition in Inverted Basin and Exploration Implication

AH Satyana*, I Setiawan*

* Exploration Pertamina MPS

INDONESIAN SEDIMENTOLOGISTS FORUM 2ND REGIONAL SEMINAR, Deep-Water Sedimentation of South East Asia, Jakarta 14 – 16 May 2001

Abstract

Salawati Basin is a foreland basin located at the frontal edge of the Indian-Australian continental plate. Sorong Fault, a major strike-slip fault in Eastern Indonesia and terminating the basin to the north, has inverted the basin’s polarity in the Late Pliocene by subsiding the whole northwestern part of the basin. Before this inversion, the Salawati Basin had a southern depocenter.

The newly formed northwestern depocenter has subsided rapidly since the inversion as an isostatic compensation to the southern and eastern uplifts. This condition resulted in the accommodation space for northwestern deep-water sedimentation. Sediments were eroded from the uplifted areas and deposited rapidly into the subsiding basin as debris flow deposits of Pliocene Klasaman sediments within bathyal depositional environment. The depocenter was increasingly subsided by tectonic loading of the contemporaneous Upper Klasaman multiple thrust sheets.

Thick deep Klasaman deposits became burial sediments for the Miocene source rocks once deposited in the lagoonal environment to attain a depth of oil window. Rapid Klasaman deposition triggered overpressuring and shale diapirism. The deposition was too fast for the sediments to compact and dewater in normal way. Overburden pressure and lack of permeable conduits caused the overpressuring. The Klasaman overpressuring presents a drilling hazard as undergone by all wells drilled in the area. Low densities of overpressured Klasaman shales caused the shales flowed upward as diapirs. Sorong Tectonism controlled these diapirs as shown by their parallel trends with the Sorong Fault. The Klasaman diapirism may relate with hydrocarbon traps of faulted domal structures, dragged beds below the diapirs’ overhang zones, faulted beds in the peripheral sinks, and turtle structures.

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Significance of Focused Hydrocarbon Migration in the Salawati Basin: Controls of Faults and Structural Noses

Awang H. Satyana*, Yanto Salim**, J.M. Demarest**
* JOB Pertamina– Santa Fe Salawati
** Santa Fe Energy Resources

Proceedings, Indonesian Petroleum Association, Twenty Seventh Annual Convention & Exhibition, October 1999

Abstract
The Salawati Basin, Bird’s Head of Irian Jaya, has been extensively explored. Exploration for oil in the basin began in 1906. Up to 1998, 160 exploration wells have been drilled in the basin. The efforts were rewarded with 35 commercial discoveries, 22 of which are still producing oil and gas. Yet, the basin is still interesting for exploration as shown by recent regional petroleum geochemistry and structural studies.

Regional evaluation on the present-day structure, paleo-structure, and timing of hydrocarbon generation versus proven hydrocarbon accumulations, have shown that unique migration compartments occurred within the Salawati Basin. The interplay between fault trends with structural noses appears to control the focus of hydrocarbon migration within the basin.

The study showed that the foredeep kitchen of the Salawati Basin is connected to the basin’s updip areas through regional structural noses. Numerous normal faults are present within the basin, intersect or parallel to the regional noses. Generated hydrocarbons flowed updip through fault fractures and carrier beds of structural noses. Faults and noses control the hydrocarbon migration pathways. High efficiency migration takes place in an area where fault trends are parallel with the structural dip. Proven hydrocarbon accumulations of the Salawati Basin discovered to date are located in such an area. The study has identified areas with high-efficiency faults and regional structural noses that act as migration fairways.

This concept of migration has explained the distribution of both proven hydrocarbon accumulations and dry wells within the Salawati Basin. The concept also provides a tool for evaluating migration risks for undrilled prospects.

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Meteoric Water Flushing and Microbial Alteration of Klamono and Linda Oils, Salawati Basin, Eastern Indonesia: Geochemical Constraints, Origin, and Regional Implications

Satyana, A.H.*, Wahyudin, M.**

* JOB Pertamina-Santa Fe Salawati, currently at Pertamina-BPPKA
** Pertamina-EP Irian Maluku Exploration Team

ABSTRACT

Klamono and Linda Fields provide good examples of oil alteration due to meteoric water flushing and biodegradation. The oils show characteristics of biodegraded oil : low gravity, high sulfur content, high viscosity, low pour point, low saturated hydrocarbon content, removal of the majority of n-paraffins and isoprenoids, and increased δ13carbon isotope ratio of saturates. Based on the molecular geochemistry (GC/GC-MS) data, the oils are moderately biodegraded (level 3 to 4 at Hunt, 1996’s scale).

Regional evaluation answers the question on the origin of the biodegradation. The Miocene Kais carbonates forming the reservoir of the Klamono Field was outcropped to the east at the Ayamaru Platform. Meteoric water has entered this area, flowed downdip westwards to the Klamono Field, and altered the oils through microbial alteration. The shallow depth of the Klamono reservoir enhanced the biodegradation.

The Linda Field is in different mechanism of biodegradation. The field is located frontal to a major surface normal fault called the Cendrawasih Fault. A splay of the Cendrawasih Fault faulted the Linda Field. The faults are considered to have acted as conduits for meteoric water to reach faulted Kais reservoir of the Linda Field and altered the oil through microbial alteration. Other oils located along the Cendrawasih Fault are biodegraded and thus support this consideration. Based on the above two mechanisms, the regional distribution of biodegraded and non-biodegraded oils within the Salawati Basin can be expected. The methods of this study can be applied elsewhere.

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