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DFE04-PO-004

INDONESIAN PETROLEUM ASSOCIATION

Proceedings, Deepwater And Frontier Exploration In Asia & Australasia Symposium, December 2004

TURBIDITE PUCANGAN FORMATION AND PETROLEUM SYSTEM IN THE EASTERN PART

OF THE KENDENG ZONE, NORTH-EAST JAVA BASIN

Moch. Yohannes Pranoto Koesoemo*

ABSTRACT

The tectonic evolution of the eastern part of the

Kendeng zone, North-east Java Basin, extends from

Late Cretaceous to Recent times. Paleogene

extension was followed by Neogene compression

which resulted in faulting and folding.

A Pleistocene sea-level fall and sequence boundary

at 2.9 Ma is interpreted from analysis of outcrop,

seismic and well data. The sequence boundary is

identified from outcrops at Kalibeng, Kabuh and

Pucangan Hill.

The Pucangan Formation was deposited from north-

flowing turbidity currents and is recognised as a

new hydrocarbon play in the area. The postulated

 petroleum system comprises early Miocene Pelang

Formation shale source rock, hydrocarbons

migrating via faults and Pucangan Formationturbidites forming both reservoir (Ta,Tb) and seal

(Td, Te).

INTRODUCTION

Detailed geological studies comprising outcrop

observations, sequence stratigraphy, well log

analysis and seismic stratigraphy have been

undertaken on the middle Pleistocene turbiditic

Pucangan Formation of the Kendeng area, north-

east Java (Figure 1).

Erosion took place in response to sea-level falls

during the middle Pleistocene. In the eastern part of

Kendeng zone the eroded clastic sediments were

transported towards the north and redeposited by

turbidity currents within a submarine fan complex,

as seen in outcrops north of Jombang.

RESULTS

The 2.9 Ma sequence boundary may be observed in

outcrops on the eastern bank of Kali Beng River at

Pojoklitik Village where marl of the Kalibeng 

* Pusdiklat Migas, Cepu

Formation underlies the turbiditic Pucangan

Formation (Figure 2).

The middle part of the Pucangan Formation,

interpreted as having been deposited on the upper

 part of a submarine fan system (Figure 3), crops out

in the Pucangan Hill area (Figure 4) and also 20 km

north-east of Jombang. The upper part of theformation is well exposed at the village of Kabuh,

10 km north of Jombang  (Figure 5)  where coarse-

grained clastic sand (Bouma division Ta) forms the

reservoir for the Watudakon and Wunut gas-fields

By using sedimentological analysis, a Pucangan

hydrocarbon play may be inferred, with coarse

clastic sand (Bouma divisions Ta, Tb) reservoir

rocks, fine-grained clastic sediment (Bouma

divisions Td, Te) providing caprock, and shale of

the Miocene Pelang Formation as a potential source.

CONCLUSIONS

1. Coarse clastic turbidite sands (Bouma division

Ta) of the Pucangan Formation forms the

reservoir in the Watudakon and Wunut gas

fields ( Lapindo Brantas ).

2. Marls of the Pelang Formation and the shale of

the lower and middle Kerek Formation are

 possible source rocks.

3. Hydrocarbon migration occurred through

faults.

4. 

Pucangan Formation shales (Bouma divisions

Td and Te) constitute potential cap-rocks.

5. It is recommended that further detailed study of

outcrop geology and analysis of seismic

stratigraphy be undertaken to provide further

important information on the petroleum systems

in this part of north-east Java.

ACKNOWLEGEMENT

The author thanks Dr. Ir. Zuhdan Fathoni, Head of

Oil and Gas Educational and Training Centre

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(PPT Migas), for motivation and kindly providing

financial support during field work and the

 preparation of this paper.

REFERENCES

Koesoemo, Y.P., Yuwono, N.T., and Musliki, S.,

1996.Sequence Stratigraphic Concept Applied to

Middle Miocene to Pliocene Outcrops in Northeast

Java Basin Indonesia. Proceedings of International

Symposium on Sequence Stratigraphy in S.E. Asia,

 p. 329–344.

Koesoemo, Y. P., 1993. Sequence Stratigraphy

Middle to Upper Miocene N.E. Java Basin, Thesis

S2 Geology ITB, Bandung.

Van Bemmelen, R.W., 1949. The Geology of

Indonesia. Martinus Nijhoff, The Hague,

 Netherland.

Vail, P. R., 1977. Seismic Stratigraphy and Global

Change of Sea Level, Part 3: Relative Changes of

Sea Level from Coastal Onlap. AAPG Memoir 26,

 p. 53-97.

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Figure 1 - Location Map.

Figure 2 - Outcrop of lower Pucangan Formation, Pojoklitik, 7 km north-west Jombang.

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Figure 3 - Outcrop of middle Pucangan Formation, Kabuh village, 10 km north Jombang.

Figure 4  - Outcrop middle Turbidite Pucangan Formation, Pucangan Hill, 20 km NE of

Jombang. Interpreted as having been deposited in mid-fan environment.

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Figure 5 - Outcrop of middle pucangan Formation, Kabuh village, 10 km north of Jombang.

Figure 6 - WD # X gas well, coarse-grained reservoir of Pucangan Formation at 250 m depth,

Bekucuk Village, 1 km North of Iodium Kimia Farma Factory 5 km west of

Mojokerto.