AAPG Internatumal Con/erma d &hibitul/I '94 Augl"'t 21-24.1994. Kuala Lumpur, MalaY.lul
Sequence stratigraphy applied to the hydrocarbon productive basins of western Indonesia
S. COURTENEY
124 Wangford Road Reydon, Suffolk, IP18 SNZ, England
Abstract: Oil exploration began in Indonesia in 1870 and the first commercial discovery was made in 1885 in the North Sumatra Basin_ Since then over 3,000 exploratory wells have been drilled in Western Indonesia with some 750 discoveries reported. By the end of 1992 over 300 fields in eleven geological basins were producing in Western Indonesia and a further 100 fields were either shut-in or had been abandoned. However, despite the fact that Western Indonesia is a mature hydrocarbon province, all published work of a regional nature, and indeed most internal company reports, use lithostratigraphy and to a lesser extent biostratigraphy_ Lithostratigraphy is based, often unwittingly, on pre-1960's work when only relatively shallow wells and limited seismic were available. Additional difficulties arise from companies using alternative names for a rock unit and the same formation name for different rock units_ Biostratigraphy is handicapped by the lack of age diagnostic fossils in the Early Miocene and older sediments in most of Sumatra and Natuna_ In Java and Kalimantan, where the older section tends to be more marine and age diagnostic fossils are present, significant errors in age determination occur due to reworking of sediments_ As a consequence the 'hydrocarbon system' in Western Indonesia is inadequately understood and exploration efforts are often poorly applied_ This paper proposes a correlative framework using sequence stratigraphy for the hydrocarbon productive basins of Western Indonesia, which should contribute to a better understanding of the 'hydrocarbon system' and significantly reduce exploration risk in Western Indonesia.
INTRODUCTION reserves of 3.20 billion barrels of oil equivalent (excluding carbon dioxide). Most of the reserves Fourteen geological basins in Western Indonesia can be considered as 'proven' as a result of the (Fig. 1) can be considered as being hydrocarbon extensive testing of the giant 'L' gas field which has productive. Oil exploration began in West Java in yet to be developed due to the high carbon dioxide 1870 and since the first commercial discovery at content of the gas. Telaga Said, North Sumatra, in 1885, over 3,000 Before discussing the proposed correlative exploratory wells have been drilled in Western framework using sequence stratigraphy for Western Indonesia. By the end of 1992 over 300 fields in Indonesia, the drawbacks of correlations using eleven geological basins were producing in Western lithostratigraphy and biostratigraphy will be Indonesia and a further 100 fields were either shut reviewed. in or had been abandoned. The three basins which did not contain LITHOSTRATIGRAPHY producing fields at the end of 1992 are the Central Java-Pati, Lombok and East Natuna basins. The At present lithostratigraphy is still commonly Tjipluk field in the Central J ava-Pati basin produced used as a means of correlation within and between oil from 1903 until 1912 and may have also basins in Western Indonesia. Figure 2 shows a continued producing small quantities of oil until common 'problem' when using lithostratigraphy to 1941 (Van Bemmelen, 1949). correlate between two wells in different exploration In the Lombok basin the Pagerungan gasfield, blocks. Though this is an example from the North which was being developed in 1992/1993, began Sumatra basin, analogues can be found in all basins commercial production in January 1994 with the in Western Indonesia and the rest of the world_ first delivery of gas to the Gresik power station in Such 'miss-ties' most commonly occur at block East Java_ boundaries (in this example the old block boundary The East N atuna basin has yet to produce was located in the middle of the seismic line), but hydrocarbons commercially, but is included due to also in blocks when the new wells are not correctly the fact t4at the basin has estimated in-place integrated with earlier wells.
Ceo!. Soc. Ma!aYJia, Bulletin 37, Ju!y 1995; pp_ 363-394 364 S. COURTENEY
LEGEND Basins: 1. North Sumatra ~ 2. Central Sumatra 3. South Sumatra 4.Sunda 5. Northwest Java 6. Central Java· Pati 7. East Java 8. Northeast Java 9. Lombok 10. Barito 11. Kutel 12. Northeast Kalimantan 13. East Natuna 14. West Natuna Iil0%J Shelf Areas « 200 m Water Depth) !dill Land Areas (Indonesia) _ Land Areas (Other Countries) - Indonesian International Border
Figure 1. The hydrocarbon productive basins of Western Indonesia.
N. SUMATRA, MEDAN AREA sw NE () BASILAM A·1 TANJUNG PURA·1 <>
1.65 Ma KEUTAPANG
BAONG SHALE 10'5Ma~llIlililillllllllllllllllllllllllllllllllllllllllllll~jj15.5Ma~ BELUMAI DOLOMITES ~ PRE·TERTIARY DOLOMITES21 'O Ma~~~~~~~~~~~~~~~~~~~~~~~~~~~~
lkm
Lithostratigraphy from Kirby et at., 1989. Figure 2. North Sumatra, Medan area. Ceo!. Soc. /1I{aLaYJia, BuLLetin 57 SEQUENCE STRATIGRAPHY APPLIED TO THE HYDROCARBON PRODUCTIVE BASINS OF WESTERN INDONESIA 365
Very few formations in Western Indonesia have km. The first use ofthe Baturaja Formation can be well defined type sections and often the origin of a traced back to Gsell (1930), who in an internal formation name has been lost. Bataafsche Petroleum Maatschappij (BPM - the For example, the Julu Rayeu, Seurula and forerunner to SHELL) report describes, in German, Keutapang Formations which contain the main the limestone outcrops near the town of Baturaja clastic producing horizons in the North Sumatra in South Sumatra. The first use of the Baturaja basin were first described by T'Hoen (1922) on the Formation in a publication in the English language basis of surface outcrops, samples from shallow was by Westerveld in 1941. trenches, and cores from the two fields and limited Hadi and Simbolon (1976) described the exploratory drilling carried out in East Atjeh until Baturaja Formation at its type locality in some that time. Though this nomenclature was later detail. They established its age range as Te.5 to adopted for use throughout the North Sumatra Tf.1 of the East Indian Letter Classification. Using basin, problems in correlations had been identified the Biostratigraphic Correlation Sheet of van Gorsel by the 1930's when the application of micro (1988) this equates to the Early-Middle Miocene palaeontology became more widespread. The (i.e. 25.2 Ma-15.0 Ma). Van Bemmelen (1949) cites introduction of electric well logs and reflection an earlier Te.4-Te.5 (Late Oligocene-Early Miocene) seismic in the late 1930's confirmed the correlation age for the Baturaja outcrops further west in the problems. Meyer (1943) notes that R. Koch carried foothills of the Gumai and Garba mountains. To out a basin wide study of the planktonic foraminifera the northwest Wahab (1986) indicates a Middle of the Late Tertiary in the North Sumatra basin Oligocene age for the Baturaja Formation in the during 1941. This work apparently corroborated area of the Musi-Klingi High. Thus the reported earlier work by Meyer and demonstrated that the ages for the top of the Baturaja Formation vary lithostratigraphic correlations of the Seurula and from around 28.0 Ma (Late Oligocene) to 15.0 Ma Keutapang Formations were between 158 m and (Middle Miocene) over only 160 km. The Baturaja ~40 m high to the biostratigraphic correlations in Formation is thus very diachronous and cannot be the wells (e.g. Kr. Merbau, Gebang-1 and Lho' reliably correlated over the four basins as implied Soekon-1) which were located some distance from in the literature. This is perhaps the best example the surface outcrops in the foothills of the Barisan of the application of the same formation name to mountains. Unfortunately, neither the earlier work different rock units. of Meyer nor that of Koch has ever been published. The South Sumatra basin also provides a good The Sihapas Formation of the Central Sumatra example of the use of alternative names for the basin has, or rather had, a type section in the same rock unit. PERTAMINA-BEICIP (1985) show foothills of the Barisan mountains to the west of in their Figure 20 the nomenclature of the the main basin. This was first described by Durham lithostratigraphic units in the South Sumatra basin. (1939) from a stream section in the Aek Si Hapas. Taking the latest Middle Miocene (N.13-N.15) Cameron.(1983) downgraded the type section to the sandstone unit as an example, PERTAMINA apply Yang Asli Member of the new Sihapas Formation the name Air Benakat Formation (Upper), which had previously been assigned to the Kampar STANVAC the name Lower Palembang Formation Group (Aspden et al., 1982). The Kampar Group and both TOTAL and SHELL assign the same unit was named after a river that rises in the Barisan to the Upper Palembang Formation. mountains and was assigned to the outcrops along its upper course. Cameron (1983) demonstrated BIOSTRATIGRAPHY that the sandstones of the redefined Sihapas Formation in this part of the Central Sumatra The following three biostratigraphic zonation basin have a provenance area to the southwest. schemes have been regularly applied to wells in Other authors (Wongsosantiko, 1976) have Western Indonesia: demonstrated that the prolific sandstone reservoirs 1. East Indian Letter Classification introduced by in the Central Sumatra basin have a provenance van der Vlerk and Umbgrove (1927) for larger area to the north or northeast. The use of the foraminifera and subsequently modified. Sihapas Formation, or Group, for these reservoirs 2. The planktonic foraminifera zonation proposed thus bears little to no relevance to the supposed by Blow (1969). An earlier planktonic type section. foraminifera zonation proposed by Bolli (1966) The Baturaja Formation of the Sumatra is often used in the East Java area. Forearc, South Sumatra, Sunda and Northwest Java 3. The calcareous nannoplankton zonation scheme basins is a further example of the 'misuse' of of Martini (1971). lithostratigraphy. The greatest distance between The salient features of each scheme are reported occurrences of this formation is over 950 described below. For a detailed discussion of the July 1995 366 s. COURTENEY methods and pitfalls, together with other depths greater than 100 m. Such sediments, if biostratigraphic zonation schemes that have been deposited, have only been preserved since the Early applied locally, the reader is referred to van Gorsel Miocene N.4 zone in the basins of western Java, (1988). Natuna and most of Sumatra (Wight et al., 1986). De Coster (1974) gives examples of two wells and East Indian Letter Classification surface outcrops in the southwest of the South The East Indian Letter Classification is still Sumatra basin where planktonic foraminifera of used today. However, since it can only be applied the N.3 zone (Late Oligocene) have been identified. to carbonate sequences and since it is principally of Burnaman et al. (1985) cited Late Oligocene value in the recognition and dating of Early and benthonic and planktonic faunal assemblages from Middle Tertiary sediments (Adams, 1970), the East the Bampo Formation in the Jeuku A-I well, and Indian Letter Classification can only be reliably Jordan and Abdullah (1992) cite recent applied to: palaeontological studies that assign a Late The extensive Late Eocene to early Miocene Oligocene age to the Bampo Shale below the Arun carbonate province that extends from Central gas field. These studies imply that planktonic Java to the southern Kutei basin and smaller foraminifera ofthe Blow's N.2IN.3 zones have been carbonate developments in the Mangkalihat identified. Peninsular and western Northeast Kalimantan Elsewhere in Sumatra, western Java and basin. N atuna the sediments below the N.4 zone are Early Miocene carbonates in all but the Central lacustrine, alluvial plain, delta plain and shelfal Sumatra and West Natuna basins. where planktonic fauna are either absent or scarce. Isolated Late Oligocene carbonate developments The latter three of course contain the major reservoir in the western parts of the North and South units throughout the area. The thickness of Sumatra basins and the onshore part of the sediments below the N.4 zone varies from 0-1,200 Northwest Java basin. m in wells to over 1,500 m on seismic sections (e.g. Adams (1970) also makes two points that are of Fig. 8). pertinence to the later discussion on sequence In eastern Java and the adjacent areas together stratigraphy of Western Indonesia. These are: with Kalimantan, planktonic foraminifera zones as 1. No type sections exist. old as P.9-P.10 (Early-Middle Eocene) are known 2. Van Doornink's record (1932) of Early Eocene (Bransden and Matthews, 1992). In Kalimantan faunas from Java is incorrect. The beds contain dating problems have arisen due to the reworking Pellatispira a characteristic larger foraminifera of Cretaceous and Jurassic fossils in Eocene genus of Late Eocene age. sediments (Mouret, 1987) and similar problems have The second point may also be of relevance to been reported from the Sumatra Forearc basin the Barito basin where the East Indian Letter (Karig et al., 1979). Classification has been applied since the 1930's. In Java and Kalimantan particularly, No detailed descriptions have been published, but significant errors in age determination using the fact that the first datable marine micro-fossils planktonic foraminifera occur due to the reworking . of the Lower Tanjung Formation cited by Kusuma of sediments or the absence of index species in the and Darin (1989) are described as Mid-Late Eocene Late Miocene and younger sediments (e.g. Badak- suggests that the micro-fossils are larger 44 type log shown as Figure 2 in Ade et al., 1988). foraminifera. It is equally probable that the Though not documented, the author believes that palaeontQlogist assigned a T.ab age to them, since such errors also occur in Sumatra especially near T.ab is a common 'catch all' first introduced by the Barisan mountains in the North and South BPM geologists for pre-Oligocene sediments. The Sumatra basins. term T.ab was used widely by many companies in The additional apparent advantage of using Indonesia until the early 1980's (Bishop, 1980). the planktonic foraminifera is the existence in This is discussed in detail later. Indonesia of a type section, which is often used by palaeontologists as a local reference point. This Planktonic Foraminifera Zonation will shortly be discussed, but unfortunately in terms The planktonic foraminifera zonation of Blow of significant age errors! (1969) is a world wide scheme that is now the most frequently applied zonation scheme in Indonesia. Calcareous Nannoplankton Zonation However, as with the East Indian Letter The calcareous nannoplankton zonation Classification it has drawbacks. The planktonic (Martini, 1971) is widely used in the low latitude foraminifera tend to be found and preserved in Cenozoic and is applied in Indonesia to the same marine sediments which were deposited in water marine sequences as the planktonic foraminifera Geol. Soc. MalaYdia, Bulletin 37 SEQUENCE STRATIGRAPHY APPLIED TO THE HYDROCARBON PRODUCTIVE BASINS OF WESTERN INDONESIA 367
zonation. Use of the two schemes together often 1 and Kruka structures are shale leads to a more accurate age determination and a enhanced inversions. MS-1-1 reached a better understanding of the palaeoenvironments. total depth of 2662 m in a marl which is The application of calcareous nannoplankton reported as being Middle Miocene in age. zonation suffers from the same geographic and age A seismic line across the Kruka field was restrictions as the planktonic foraminifera. At first published by Patmosukismo et al. (1985) it appears that the calcareous nannoplankton zones and this is shown in Figure 4. The MS- NN.1 to NN.3 and NN.8 have been correlated to the 1-1 structure is represented at the surface Indonesian section, implying perhaps, the existence by Kambing Island and is more elongate of an Indonesian type section. than the Kruka structure. Its flanks are also steeper, but the structure appears Indonesian Type Section not to be as faulted as the Kruka The existence of a reliable Indonesian type structure. section for either planktonic foraminifera or BD-1: Drilled by MOBIL in 1987 to test a calcareous nannoplankton is of great importance suspected Early Miocene reefal buildup. since it would provide a vital control point for A seismic line across the 'BD' reef sequence stratigraphy. The type section of the published by Widjonarko (1990) is shown planktonic foraminifera can be· traced from Blow in Figure 5. The ages on Figure 5 have (1969) to Bolli (1966) and back to a dissertation at been converted from the series ages using the University of Utrecht by Boomgart (1949). the Mesozoic-Cenozoic Cycle Chart ofHaq The planktonic foraminifera type section is in et al. (1987). fact the Bodjonegoro-1 well drilled by BPM in 1934 The difference between the post and pre-drilling in Northeast Java (Fig. 3 - inset). It is perhaps interpretations is very significant bearing in mind worth noting that in the same year as Boomgart that the MS-1-1 well is only 7.5 km NNW of BD-1 completed his dissertation, van Bemmelen (1949) and has apparently reliable palaeontological control published The Geology of Indonesia. In the to the Middle Miocene. There are no major faults Economic Geology section of this work van between the two wells, just the steep flank of the Bemmelen states, when describing the stratigraphy MS-1-1 structure which is seen on the northern end ofthe oilfields in Northeast Java: "The sequence of of each panel in Figure 5. Whereas the difference the Neogene sediments in NE Java differs strongly in the deeper and older sequences can be explained from the stratigraphy of the oil terrains in Sumatra by lack oflocal control, the difference of around 430 and Borneo." (Volume II, Page 33). The milliseconds TWT (approximately 410 m) at the Bodjonegoro-1 well is located on the same anticlinal Base Pliocene is much harder to explain. The axis as the Kawengan oilfield around 25 km to the palaeontological data from the MS-1-1 well indicate ESE. Since the Kawengan field is the largest field a reliable correlation back to the type section of the in Northeast Java, the choice of a type section on Bodjonegoro-1 well. It is thus necessary to examine the same regional trend in an area with obvious fully the palaeontological data in the Bodjonegoro- stratigraphic correlation problems is worrying. 1 well which is only 150 km west of MS-1-l. Notwithstanding the above, Bolli (1966) stated: Figure 6 shows the distribution of planktonic "No similarly complete Lower Miocene to Pliocene foraminifera in Bodjonegoro-1 which has been section rich throughout in planktonic foraminifera simplified so that only the index species of Bolli is known to the author. Bodjonegoro-1 therefore (1966) are included. It is apparent that Bolli (1966) offered a unique opportunity to restudy the and Blow (1969) assign significantly different ages planktonic foraminifera in the light of present day to the planktonic foraminifera as is shown in Table l. knowledge ...... " The Bodjonegoro-1 well has thus In justifying the differences between their become established as a type section even though interpretations Blow (1969, page 90) states: "It is Blow (1969) also expressed some reservations. evident that Bolli and Bermudez (1965) did not Before examining the Bodjonegoro-1 well in correctly assess the complete stratigraphic ranges of detail the results of two modern wells in the East the taxa used by them ...... Further, Bolli (1965, Java basin will be reviewed. The two wells are: 1966) and Bermudez (1965) did not relate their MS-1-1: Drilled in 1970 by CITIES to test the 'biostratigraphy' sufficiently to local geological Kawengan ("GL") Formation of Late conditions and were misled by heterogeneous Miocene-Pliocene age (using the-zonation assemblages, incomplete knowledge of the ranges of of Bolli) which produced some 10.8 million the taxa they used and by using too few taxa in their barrels of oil in the onshore Kruka oil zonatio~: thus, they had insufficient stratigraphic field (Courteney et al., 1989) situated control over the actual taxa used in the distinction some 53 km to the west. Both the MS-1- and differentiation of the 'zones' they proposed". July 1995 105 0 110 0 111 0
ION
Equator
JAVASEA _
Figure 12A . Figure 20
085 0 100· 105 0 110 0 115 0
Figure 3. Location of figures and wells. en om c m Z E. JAVA, KRUKA FIELD () m ~ :rJ ~ Gi :rJ J> -u 'CLASSIC' INTERPRETATION BASED ON ::r: -< INTERPRETATION SEQUENCE STARTIGRAPHY -uJ> -u c:: m w KRUKA FIELD E W KRUKA FIELD E o o--l o.o -=....-:"!= =":""'l'l!;'" 0.0 0.0 '"r-:l~=~ 0.0 ::r:--l m ::r: -
c.u (J) <.0 E. JAVA, 8D·1 WELL
INTERPRETATION OF POST DRILLING REPROCESSED SEISMIC INTERPRETATION s o BD-1 N s *BD-1 N Proposed Location TD4256m
5.5Ma 5.5Ma 10.5 Ma 10.5 Ma ~+-21.0Ma 21.0 Ma ?25.5Ma
?25.5Ma 2km
Modified from Widjonarko, 1990. Figure 5. Pre and post drilling interpretations ofBD-l well, East Java. SEQUENCE STRATIGRAPHY APPLIED TO THE HYDROCARBON PRODUCTIVE BASINS OF WESTERN INDONESIA 371
DISTRIBUTION OF PLANKTONIC =.(!I Ii FORAMINIFERA IN WELL il t iii BODJONEGORO-1, EAST JAVA. I I j I ;;; a I j 1 ;I ":I i .II i !i!IJ i~!i tt~i~l - UTHOS1RAllORAPHY BPII DEPTH IN PLANKTONIC:Ii :I ! I- ; i I I :Ii :Ii a -I I I!! I PLANKTONIC ! ACCORDING 10 BPII Faunal MElRES FORAMINIFERA ~.. i .II -c i .II .II ~ .II 01 I!! .II iii .II .11.11 FORAMINIFERA II Z_aBELOW ZONES 1!-F.'C11=11I1!11!'f. 1 -!111 ZONES jI I-Fanna--aan-"'-SIBg--l. ROTARY (BOW, 1868) .§ :!' 1.1 .co .§ j .I .8 .8 .ao .8 1.1 .8.8 (BLOW, 1888) :I ~ ~ ~~ a~ ~~Ia!~!!~~ ~~~ I Tm :>< I NO SAMPLES t---+--I .. 101- III M Ii ?EllUIV.OF G.INfLATAI N 20 ifi u 4 I~ G. TRUNCATULINOIDES • So! N 218- :5 D 901- I ~~;o'iiMB _N,:1! ___ lao U 1M _ ~ G.lIARGAIIII'AE II IN; llr • 5.5Ma 1---1'-..... SIB _ ::5 I • -
Le -Lilt G~ III ~., ACOSTAEHSB - ~~~ I N.17 ifi III 6 - """ .. ~ ~ ~ """~ ~g - "...... ~""".. N.16 Ii ~ ~- ~ ~~ GLOBOROTALIA ~ :5 YENARDU -- ~ Nj5 "GL" g W 05- 5~----+-~-+rHH-+-HH~-+~4-+-~-+~---~ ~ 10.5Ma o .. .. "!!I GLOBORGTALIA N.14 N ...... ! MAYBII o ,.. - e ...... o L Nj3 III o 7 1219 ~ ...... GLOBIQBUNDIDES !i iii :: :::. RUBER ~ U ...... a g ------~: 1«11- g G~ !i - FOHSIIIOBUS~.. N.12
11M1855- .... "I ~~ f/OS _ G. FOHSI LOBATA II """
...... : GLOBOROTALIA Ito.... $ FOHSIFOHSI II """ "'" I~~ t-.l!.11 "OK" ii'I I ...... 11142- 15.5Ma G. FOItSI BARBAHENSB T III f-- 1814.1_ II II I i5 ... GLOBICISIINA1B.LA II N.S N 9 8 S INSUETA • Ii ==:: :: :: III T.D. 2034 m
Notes JAVASEA ~ 1. Tm =Tambakromo, Le =Ledok. 2. Part of N.9. aU of N.10 and part of N.11 mlaalng. 3. Hlatua malked aa: ---
Map Legend <> BOdJonegoro-1 Wen Location. * FOBBn Localltlea • • OIiFielda. e GaB FleldB.
Figure 6. Bodjonegoro-l Well. 372 S. COURTENEY Table 1. Comparison between age determinations of Bolli and Blow for the well Bodjonegoro-l.
Chronostratigraphy Bolli Blow Series (Haq et 01., 1987) (1966) (1969) Difference
Base Pliocene 5.5Ma 216m 254m 38m
Base Late Miocene 10.5 Ma 286m 670m 384m
Base Middle Miocene 15.5 Ma 1431 m 1916m 485m
Figure 36 of Blow (1969) correlates Bodjonegoro- The two localities mentioned by van Gorsel are 1 to Kawengan-9 which is located 25.2 km to the marked on the map in Figure 6. The Bodjonegoro- west. This well in the large Kawengan oil field is 1 well is located between them. The planktonic located 670 m northwest of Kawengan-1 which is foraminifera distribution chart in Figure 6 shows a shown on the seismic section in Figure 15. The preponderance of Globorotalia. This author main production in the Kawengan field comes from therefore believes that the Bodjonegoro-1 well has the Ngrayong sands at the base of the 'GL' penetrated a section of Pleistocene sediments (Globigerina Marls) Formation which are containing abundant reworked Miocene and interbedded with deep water marls. Pliocene fauna (both benthonic and planktonic It is interesting to note in Bolli (1964) that foraminifera). Such an interpretation also explains adverse ecological conditions are invoked to explain the fact that good porosity reservoirs have been an absence over 899 m of the Globigerinoides ruber encountered in the oil fields in the area despite the in Bodjonegoro-1 and that similar conditions are fact that palaeontologically the sediments would again invoked to explain why the Globorotalia appear to be deep marine. The Bodjonegoro-1 wen tumida complex in Bodjonegoro-1 continue to the is thus not suitable as a type section for planktonic present, whereas in Venezuela (Cubagua-1) the foraminifera in Indonesia. species disappears after a short but distinct Mention was made earlier of a possible occurrence. Indonesian type section for calcareous In view of the reported difference in stratigraphy nannoplankton. However, when the references of between NE Java and other areas of Western Martini (1971) are checked the Indonesian examples Indonesia (van Bemmelen, 1949), the presence of are traced back to Bramlette and Wilcoxon (1967) over 3,300 m of Pliocene and younger sediments in who state that: "the many (95) samples from the well BD-1 (Widjonarko, 1990), the correlation Indonesia were from drilled wells, with their location by Blow (1969) between the Kawengan field and and depths unavailable, but their original Bodjonegoro-1 and the rapid facies changes in the stratigraphic assignments are indicated under the NE Java area reported by several authors, an discussion of Biostratigraphic Zonation and shown alternative interpretation is possible: namely, that in Table 2." Their Table 2 cites the East Indian most of the Bodjonegoro-1 section is reworked! Letter Classification, which has been discussed Strong evidence to support this interpretation earlier, and the section of their discussion of is provided by van Gorsel (1988) who states: "Uplift Biostratigraphic Zonation dealing with Indonesia of the Kendeng zone in NE Java caused erosion of ends with the comment: "The letter assignment of the rich Late Miocene-Pliocene Globigerina marls these samples was based, however, on the results of and deposition of locally abundant reworked deep field exploration, drilling, and accompanying study marine foraminifera in the Pleistocene lacustrine by biostratigraphers in areas of Java and Borneo and fluvial Pucangan and Kabuh Formations to over a period of many years." While this does not the South. At first sight preservation is good, but necessarily mean ,that a full circle back to the close inspection reveals common dissolution pits. Bodjonegoro-1 well has been made, it is highly Also, most species are thick-walled Globorotalia and likely that the Miocene and younger samples were Pulleniatina: small fragile Globigerina are absent. from the NE Java area. There is thus no suitable Recent sediments of the Solo River delta North of Indonesian type section for the calcareous Surabaya also contain such reworked Kendeng zone nannoplankton that can be used for sequence material (S.R. Troelstra pers. comm.)." stratigraphy.
Geol. Soc. MalaYJia, Bulletill 37 SEQUENCE STRATIGRAPHY APPLIED TO THE HYDROCARBON PRODUCTIVE BASINS OF WESTERN INDONESIA 373 PROPOSED CORRELATIVE compaction) of each third' order cycle of Haq et al. FRAMEWORK USING SEQUENCE (1987) from some 500 wells throughout Western Indonesia. It is interesting to note that even after STRATIGRAPHY allowing for the effects of compaction the late All the hydrocarbon producing basins of Western Neogene sequences are considerably thicker than Indonesia are underlain by rifts or rift systems the earlier sequences. The convergence of the (Courteney and Williams, i994) and generally these Average and "Weighted" Average curves around basins are separated by wide arches comprising 19.5 Ma shows the point at which the Early Tertiary Pre-Tertiary metasediments and intrusives. rifts have been filled. The reason for this is that Consequently, the limitations of biostratigraphy the ''Weighted'' Average curve only includes those described earlier are further compounded by the wells where the earlier sequences have been fact that sequence boundaries visible on seismic deposited and preserved. The later divergence of and tied to biostratigraphy in wells in one basin the two curves in the late Tejas B2 and in Tejas B3 cannot often be followed on seismic to the adjacent indicates the erosion caused by the uplift and/or basin. This is particularly true of the pre-Early inversion particularly in the Barisan Mountains, Miocene sequences (pre-N.4). Older units in the Sumatra, the Natuna area and Central Kalimantan non-marine basins of Western Indonesia have been during those times. . correlated by applying the principles of ,non-marine' Prior to discussing the Supercycles in detail a sequence stratigraphy to well logs and seismic with further 'key' point needs to be addressed: namely, support, when available, of Kr/Ar age what is 'Basement'? Many authors imply that determinations of volcanics. Basement is synonymous with Pre-Tertiary. This The major 'geological hurdles' to this correlative interpretation is usually based on the interpretation framework were the Karimunjawa Arch (separating of a low frequency/high amplitude seismic event the Northwest Java basin from the basins of the (PERTAMINA-BEICIP, 1994; Soeparyono and greater East Java area), the Meratus Mountains Lennox, 1989) or significant changes in electric log (and their extension, the Meratus Ridge) and the character (Mulhadiono and Sutomo, 1.984). In many Laut Ridge (separating the greater East Java basins cases this interpretation is valid, however, there from the Barito and Kutei basins), the Mangkalihat are some significant cases where it is not. Figure Peninsular (separating the Kutei and Northeast 8 shows a question first posed by Santoso et al. in Kalimantan basins), the Lampung High (separating 1990. The Top Pre-Tertiary reflector is in fact at the Sunda and South Sumatra basins) and the around 1.65 seconds TWT in the centre of the Asahan Arch (separating the North and Central section. The packet oflow frequency/high amplitude Sumatra basins). Lesser 'hurdles' were occasioned events that reach a time of 1.15 seconds TWT near by the Tigapuluh High, which separates the Central the centre of the section represent the Brown Shale and South Sum~tra basins, and the Seribu Platform, Member (or Formation) of the Pematang Formation which separates the Sunda and Northwest Java (or Group). In the Central Sumatra basin this is basins. These are all shown in Figure 3. The . the main source rock (Williams et al., 1985). Thus isolated nature ofthe Natuna basins on the northern many authors have interpreted the top of the source margin of Sundaland also presented difficulties. rock interval as the top of basement (or Pre Notwithstanding the above, the Tejas A3, A4, Tertiary)! . B1, B2 and B3 Supercycles ofHaq et al. (1987) can PERTAMINA-BEICIP (1994) and Soeparyono be recognised in Western Indonesia. Sediments and Lennox (1989) have made similar error in the from the earlier Tejas A2 Supercycle are also present Asri sub-basin of the Sunda Basin and in the Cepu locally. Using log and seismic data within the area of the East Java basin. Seismic data in the constraints of the available and reliable age Medan area also suggests that a more optimistic determinations (from biostratigraphy, strontium interpretation to that of Mulhadiono and Sutomo isotope data, radiometric data), boundaries (1984) is possible. They are by no means the only approximating to the 39.5 Ma, 30.0 Ma, 21.0 Ma authors which have made the same error and, for and 10.5 Ma sequence boundaries of these example, a detailed comparison of earlier Supercycles have been correlated throughout publications containing Pre-Tertiary or basement Western Indonesia. Additionally, perhaps as a maps with the well results in the AAPG function of the better age determination through International Developments (MASERA-AAPG Data the application of planktonic foraminifera, the 25.5 Systems, 1991) shows similar misidentification. Ma, 15.5 Ma and 5.5 Ma Sequence Boundaries have also been correlated. Other sequence Tejas B2 (TB2) Supercycle boundaries have been used locally. The discussion of the supercycles of Haq et al. Figure 7 shows the thicknesses (after (1987) will commence with the least controversial. July 1995 374 S. COURTENEY
Om 200 m 400 m 600m 800m oMa I _ ~ ~Badak.44 ...III ~ ~- --- TB3 -< r - - ~ ArunField .. ~ . 10 Ma ~ r--. 10. 5 Ma ~ ------~ -;2~ TB2 71G~~ 20 Ma ~ ---- 21.0 Ma K:;
~ TB1 ~ t::a 30 Ma Y? 30.0 Ma [ ~ c TA4 ~ 40 Ma ~ 39.5 Ma :------TA3 i~ ~ t::- 50 Ma 49.5 Ma LEGEND G-B-B Average deposition. ~ 'Weighted" average deposition (see text) . ••• Maximum deposition. Figure 7. Graph of sediment thickness versus age.
C. SUMATRA: NORTHERN AM AN DEPRESSION sw NE
0.5
1.0 Top Pre· Tertiary
1.5
2km
Modifi ed from Santoso et al., 199C. Figure 8. The Pre·TertiaryiBasement Enigma.
GeoL. Soc. )J1nfnYJia, BuLletin 37 SEQUENCE STRATIGRAPHY APPLIED TO THE HYDROCARBON PRODUCTIVE BASINS OF WESTERN INDONESIA 375 The TB2 Supercycle is tied to the giant Arun gas interval of the Kawengan field, the Ngrayong sands, field (Figs. 9A and 10) by palaeontological and is located above the 10.5 Ma Sequence Boundary strontium isotope data (Jordan and Abdullah, 1992) and is some 5.5 million years younger than the age and its base, the 21.0 Sequence Boundary, is tied to assigned to the Ngrayong sands in the literature the N.5 Zone of Blow (1969) elsewhere. (normally earliest Middle Miocene). Figures 9A-9C show a regional correlation using Similar correlations through to the Kruka oil well logs through significant fields in the North, field (Fig. 4, right panel) and the Sekarkorong oil Central and South Sumatra, Sunda and West field (Fig. 16, right panel) near Surabaya in East Natuna basins. In Figure 9A the TB2 Supercycle Java indicate an error of around 10 million years in is generally transgressive until the 15.5 Ma the 'classic' interpretation of these fields. Sequence Boundary. In the Arun field reefal Reservoirs of the early TB3 Supercycle contain limestones of the Peutu Formation were developed. 22.57% of the estimated 'in-place' reserves of Reefal limestones were also developed in the early Western Indonesia (Fig. 22), the vast majority being part of the Supercycle in the Tanjung Laban field in the clastic reservoirs of the Kutei basin (e.g. Fig. (Fig. 9B) and the nearby Rawa and Ramba fields 14 and Duval et al., 1992). Other significant fields (Fig. llB) which are locally assigned to the Baturaja in the same interval include: the Telaga Said Formation. A similarly thin reefal limestone is oilfield, N. Sumatra; the Kawengan oilfield, E. also developed above the 21.0 Ma Sequence Java and the giant 'L' gasfield, E. Natuna (Sarg, Boundary on the Krisna High in the Sunda basin 1988) which has reservoirs i.n a large reefal (Figs. 9C and 12A). A much thicker reefal carbonates. Only minor hydrocarbon potential development is the reservoir of the 'BD' gas field in remains in the early TB3 Supercycle. the East Java basin (Fig.. 5). The late TB3 Supercycle includes the In the Central Sumatra basin retrogradational Pleistocene clastic reservoirs of the Central Java sandstones were deposited and are the main Pati (Tjipluk oil field), East Java and Northeast reservoirs for the giant Duri field (Fig. 9A). These Kalimantan basins which account for 0.065 of the are in turn overlain by the progradational sands of estimated 'in-place' reserves of Western Indonesia the regressive late TB2 Supercycle which are also together with the Pliocene clastic reservoirs which reservoirs in the Duri field and some nearby much account for a further 2.94% of the 'in-place' reserves. smaller fields. In the West Natuna basin, sands of Such major fields as Rantau, North Sumatra, and the Lower Arang Formation are productive in the Pamusian, Northeast Kalimantan are produced Belida field (Figs. 9C and 13). These laterally very from Pliocene reservoirs. The reservoirs of the late discontinuous sands were probably deposited in TB3 Supercycle are only of historical interest since incised valleys. The overlying shales record the no remaining potential exists. first marine transgression in this part of the West Natuna basin. In the giant Badak gas field, Kutei Tejas B1 (TB1) Supercycle basin, the G61 Reservoir is a progradational The TBI Supercycle is also tied to sandstone in the early transgressive part of the palaeontological and strontium isotope data in the TB2 Supercycle (Fig. 14). Arun gasfield (Fig. 9A) where the interval from The early TB2 Supercycle (21.0 Ma-15.5 Ma) 25.5 Ma to 21.0 Ma is missing. However, as contains 14.87% of the estimated 'in-place' reserves mentioned earlier in the section on Biostratigraphy, of Western Indonesia (Fig. 22). The majority of elsewhere in Sumatra planktonic foraminifera are these are reservoired in the Arun and Duri fields. rare below the N.4 Zone. In Figures 9A-B the Duri The late TB2 Supercycle (15.5 Ma-l0.5 Ma) contains field has no age diagnostic foraminifera, in the 18.80% of the estimate 'in-place' reserves which are Minas, Sengeti and Tanjung Laban fields planktonic mostly reservoired in the Kutei basin. foraminifera allow the dating of the shales above the 25.5 Ma Sequence Boundary. No age diagnostic Tejas TB3 (TB3) Supercycle fossils are present in the lacustrine shales of the U sing planktonic foraminifera located away Alu Alu E-l well in the West N atuna basin, whereas from major uplifts such as the Barisan Mountains the shales interbedded with the thick carbonates of of Sumatra and the Kendeng Zone in East Java, it the Lower Baturaja Formation (above the 25.5 Ma is possible to correlate the 5.5 Ma and 10.5 Ma Sequence Boundary) in the Krisna field can be Sequence Boundaries into areas of significant reliably dated to the N.4 Zone. reworking like the oil fields of Northeast Java In South Sumatra sediments above the reef mentioned earlier. build-ups on the Musi-Klingi Platform have been Figure 15 shows the resulting interpretation of dated as Late Oligocene, N.31P.22 and N.21P.21 (de the area between and around the Kawengan and Coster, 1974; Wahab, 1986). Figures llA and llB Sebogo oil fields, E. Java. The major producing again illustrate the diachronous nature of the JuLy 1995 376 S. COURTENEY
ARUN A·1 (N. Sumatra Basin)
-700m ;::c::..:- lOP --'>' C',,-~__ _ < i r ~-e- .. ! \- .~ ~ 13.8M~, \ _. /13.8Ma 15.5 Ma ~ 15.5 Ma \ , -'1 ~~ ·500m Legend I~, ~ ~ Interval producing gas ./ , } ..:i~ * Interval producing gaslccndensate -""l: • Interval producing oil
) } -300m \ ;,.t ) ~ { 15.5 Ma DURI FIELD I (C. Sumatra Basin) ( MINAS FIELD -100m i ~ SP Rt (C. Sumatra Basin) l 5- 'f=-'-&z~( • 1:. ~-J ·r~ ~ 21.0MaTom ~ > • ~ om-21.0 Ma :~~ 25.5 Ma I, I Figure 9A. Correlation ofTBl and TB2 Supercycles. SENGETI·2 (South Sumatra· Jambl Sub·basln) TANJUNG LABAN·19 GR (S. Sumatra Basin· North Palembang) 21.0 Ma -0 m+---.:~...... j~--===:?----+------+--"';;;:~H~::------+O m- 21.0 Ma _+-----:~..... ~-----+__25.5 Ma ,....,...... --~ri-ft-..:....----t-- 30.0 Ma +200 m+---=:=llt-t-/- ...... -_:----I '------'--'------'-+200 m 25.5 Ma --+_~ __++__~...::::.--+J Pre-Tertiary "i'400I'iimnl====~~=f$======~~==j= Pre-Tertiary Figure 9B. Correlation ofTBl and TB2 Supercycles, continued. SEQUENCE STRATIGRAPHY APPLIED TO THE HYDROCARBON PRODUCTIVE BASINS OF WESTERN INDONESIA 377 ALUALU E·1 KRISNA B·2 (West Natuna Basin) (Sunda Basin) -SOm -SOm u... • (Doop) =-:=~ • 21.0Ma-Om Om-21.0 Ma • f- {" 1. +100m 25.5 Ma • ~ • • .. -~ e~ • ?.- 30.0 Ma -+200 m • 25.5 Ma • +300m Pre-Tertiary I I Pre-Tertiary Figure 9C. Correlation ofTBl and TB2 Supercycles, continued. N. SUMATRA, ARUN FIELD sw () () NE ~ ___ 1.0 1.0 21.0~ Top 3.0 Ma Pre-Tertiary ~;re~~i~~~!~~ 1 km Reinterpretation of seismic section from Wirjodihardijo, 1992. Figure 10. Sequence stratigraphy of the Arun gas field, N. Sumatra. July 1995 378 S. COURTENEY S. SUMATRA, BENAKAT GULLEY sw Rambutan Oilfield NE 1.65Ma-+ ~ . "-S.SMa S.5Ma-+ ..-10.SMa 10.5 Ma-+ . 1S.5 Ma-+ ..-15.5Ma 21.0 Ma-+ 30.025.5M~a-+ Ma ..- 21.0 Ma . ..-2S.5Ma ~ ..-~~ Top Pre-Tertiary ~Th~~JII~~;~:~lllllllllliillllllilllllll:~~4.0 Modified from Harding, 1983. Figure llA. South Sumatra basin sequence stratigraphy, Part l. S. SUMATRA, RAWA AREA sw • • RAWA FIELD • RAMBA FIELD NE 21.0Ma-' 25.5 Ma:--::-... 1.0 30.0Ma-' 39.5 Ma , 2km , Reinterpretation of seismic section from Zeliff et al. , 1985. Figure llB. South Sumatra basin sequence stratigraphy, Part 2. Ceo!. Soc. Iffa!aY,lia, BuLLetill 37 SUNDA, KRISNA FIELD WNW '0' PLATFORM ESE 0.0 0.0 _------..,------=~------..,..~=-.__:_.-_._:...;.. • .• ;_ -:-_. -- -- ' ,- - -~ -:: •.-=-~":':.--.---=-- . · --0- ~::;;::~===;;.:.> +-5.5Ma 1.0 15.5 Ma---+ Ma 21.0~ +-15.5 21.0 Ma Top ~=r~F~:lir::=;~S==E~~::E~~~~ +- Pre-Tertiary i~~ii!il~~~~i~i~+- 25.5 Ma 2km Reinterpretation of seismic section from Ardila, 1983. Figure 12A. Sunda basin sequence stratigraphy, Part 1. EAST SUNDA BASIN: SEQUENCE STRATIGRAPHY sw NE 0.0 'T"""-:----...--::__ --~-----~~~ ...... ------_!_--__._ 0.0 +-10.5 10.5 Ma-...... Ma 1.0 ~~a 15.5Ma~ +-21.0 Ma 21.0Ma~ ~25.5Ma 25.5Ma~ 30.0Ma-.. 2.0 39.5Ma~ ~ Top Pre-Tertiary 3.0 3.0 2km Reinterpretation of seismic section from Fainstein, 1987. Figure 12B. Sunda basin sequence stratigraphy, Part 2. 380 S. COURTENEY Baturaja Formation. On the Musi-Klingi Platform Figure 12B shows the 30.0 Ma Sequence the Baturaja Formation is developed between the Boundary truncating earlier syn-rift sequences 30.0 Ma and 25.5 Ma Sequence Boundaries either side of the 'NF' High over which it is (southwestern end of Fig. llA) whereas as shown coincident with the top of the Pre-Tertiary. A very earlier the Baturaja Formation in the Rawa and similar structural configuration is seen in the West Ramba fields is part of the T2B Supercycle above Natuna basin (Fig. 13) where the 30.0 Ma Sequence the 21.0 Ma Sequence Boundary (Fig. llB). Boundary is interpreted near TD in the Alu Alu E- Elsewhere in the North, Central and South 1 well (Fig. 9C). Sumatra and the Sunda basins the strata between In the BZZ area of the Northwest Java basin the 30.0 Ma and 25.5 Ma Sequence Boundaries are the interval 30.0 Ma to 25.5 Ma is represented by represented by marginal marine through delta and the reefal carbonates of the Baturaja Formation (!). alluvial plain sediments which contain no age With similar exceptions in the Northwest Java diagnostic fossils. The 30.0 Ma Sequence Boundary basin, throughout the rest of Java and also eastern is, however, a regionally significant unconformity Kalimantan the same interval is mainly represented which can be followed on seismic. It separates the by extensive platform carbonates or deep marine generally more marine rift fill sequences from the. shales. underlying non-marine syn-rift sequences (for The late TB1 Supercycle reservoirs contain example, the Sihapas from the Pematang in Central 21.96% of the 'in-place' reserves of Western Sumatra and the Talang Akar from the Lemat in Indonesia (Fig. 22). These reservoirs include the South Sumatra). Bekasap sandstones of the super giant Minas field On Figure 10 the 30.0 Ma Sequence Boundary in Central 'Sumatra, the Talang Akar sands of the is so close to the top of the Pre-Tertiary event that large Talang Akar-Pendopo field in South Sumatra they cannot be differentiated. On Figure llB the and the older Baturaja carbonates in the many 30.0 Ma Sequence Boundary and the top of the Pre small fields in the South Sumatra, Sunda and Tertiary are coincident below the Rawa field and Northwest Java basins. The early TBl Supercycle the same situation occurs below the Krisna field reservoirs contain 12.81% ofthe 'in-place' reserves. (Fig. 12A) where the Talang Akar sandstones which The early TB1 reservoirs include both carbonates onlap the Krisna High represent sequences between and clastics which are more geographically restricted the 30.0 Ma and 25.5 Ma Sequence Boundaries. since they are deeper in the rift fill sequences. w. NAT UNA, BELIDA FIELD AAE·3 • AAE.1. • AAE·4 NE 10.5 Ma 10.5 15.5 Ma 15.5 21.0 Ma 21.0 25.5 25.5Ma 30.0Ma 30.0Ma . . .. 2.0 CO 'Top Tol' Pre-Tertiary Pre-Tertiary 2km Reinterpretation of seismic section from Sutoto, 1991. Figure 13. West Natuna basin sequence stratigraphy. Geol. Soc. MaLaYdia, Bulletin 37 KUTEI BASIN, BADAK FIELD en om c: m oz BADAK-44 m NW 8ADAK-76 8-40. 8-15 08-17 .8-52 8-71 SE (TYPE LOG) il O Projected 0 0 Projected Projected ~ R G5 ~ -0 :::I: -< » -0 c:-0 , m .... o &.ilia d 1.0 :r!m :::I: o-< •_. ::Il ~ ~ Z 10.1110 -0 ~ o 10.5 Ma c: -. ~ <: m 1&.5110 ~ Z 15.5Ma---' en o •_. "T1 3.0 3.0 ~ 1 km ~ I I m ::Ilz ?ZUllo Z o Reinterpretation of seismic section and type log from Ade et ai, 1988 rnz S> Reinterpretation of seismic section and type log from Ade et al., 1988. Figure 14. Kutei basin sequence stratigraphy. w ex>..... 382 S. COURTENEY Tejas A4 (TA4) Supercycle Systems, 1991) and the sediments penetrated by The TA4 Supercycle is the most critical and this well are believed to include Middle Eocene controversial since its lower sequence boundary fluvio-deltaics similar to those which crop out in (39.5 Ma) is the top of the major effective source the Bajah area onshore. interval throughout Western Indonesia (Courteney In the Northwest Java basin the Jatibarang and Williams, 1994). By implication it makes the field produces from the J atibarang Volcanic age of these underlying syn-rift source rocks Formation which is dated as Late Eocene to Early significantly older than is published in the Oligocene (PERTAMINA-BEICIP, 1985 and Nutt literature. and Sirait, 1985). This age range is supported by Figure 17 shows all wells drilled to December, Soeria-Atmadja et al. (1994) who report a series of 1992 which have been reported as haVing drilled KlAr age determinations of surface outcrops of into, or through, Late Eocene sediments; surface volcanic rocks in Java from the Late Eocene (e.g. outcrops of Middle and Late Eocene sediments; and 39.86±3.31 Ma) to the Early Oligocene (e.g. the approximate extent of the Late Eocene in the 29.24±2.38 Ma). subsurface. As can be clearly seen the main In the South Sumatra basin de Coster (1974) occurrences of unequivocally dated Eocene cites probable Late Palaeocene-Early Oligocene ages sediments are in Kalimantan and the Lombok and for the Lemat Formation on the basis of spore East Java basins (for example: PERTAMINA pollen and KlAr age dating of some samples of BEICIP, 1982 and 1985, Mouret, 1987, Sunaryo et shale and tuff. In the Benkulu segment of the al., 1988, Phillips et al. , 1991, Bransden and Sumatra Fore-arc the FINA Arwana-1 well Matthews, 1992 and van de Weerd and Armin, apparently reached TD in Eocene sediments and 1992). Surface outcrops have been reported from Karig et al. (1979) reports the bathyal shales and Java which range from near shore clastics and turbidites in four wells in the Sibolga segment of limestones to bathyal shales and range in age from the Sumatra fore-arc as having been redetermined Middle to Late Eocene (van Bemmelen, 1949 and as Late Eocene to Early Oligocene in age. Onshore references therein, and Shiller et al., 1991). The Central Sumatra many papers have been published Ujung Kulon-1A well offshore Southwest Java on the Eocene section in the Ombilin sub-basin and reached TD in the Eocene (MASERA-AAPG Data Koning and Aulia (1985) also describe the results of E. JAVA, KAWENGAN FIELD OFFSET OF -3 KM;J KAWENGAN FIELD ~ OFFSET OF -1.5 KM SW NE.S .K.l 0K.eo NJ,SW SEBOGOFIELD --.~E Sea Level ------~~Ui~;;;;;:::;:;~~------~~~~.::=~... 0.0 .,------..... 10.5 Ma 3.0 f.,1j'1~1~·5Ma Top ------liii~;~~II.§I~I~~f~""'1ff' Pre-Tertiary Reinterpretation of seismic sections from Sutarso and Suyitno, 1976, and Soeparyono and Lennox, 1989. Figure 15. East Java basin sequence stratigraphy. Ceo !. Soc. MaLaYJia, BuLletin 57 en om c m E. JAVA, SEKARKORONG FIELD z (') m ~ ~ 1:;5 $! 'CLASSIC' INTERPRETATION BASED ON "'0 :::c -< INTERPRETATION SEQUENCE STARTIGRAPHV » "'0 "'0c: SEKARKORONG FIELD SEKARKORONG FIELD m w E w E o (ABANDONED) (ABANDONED) d :::c-t m :::c o-< oe3 » :D ~ "'0 :Do o c ~ <: m ~ Z rn o " ::em ~ 1.0 ...L...;~;';';';:" ______~--'- 1.0 m~ 1.o~------~~t.o 1km 1km z o z mrn Reinterpretation of seismic section from Patmosukismo et al., 1985. > Figure 16. The differing interpretations ofthe Sekarkorong field, East Java. w 00 0 095 0 105 110 0 115 0 ~ ~: SON .. C1 Equator .. oc::;;;J...... ) ,. . V " } ... « \ \. '1'.".": ,,,. \: ) ... :;> '" • /11 ~ () o C :J:l -I zm m -< Legend EEl Eocene rifts in Java, Sumatra and West Natuna ~ ;;:; • Larger Eocene outcrops in Kalimantan and Java :---"" • Wells penetrating Late Eocene and older sediments ~ " ~ ;:;-- ~ ~. t:x:I 095 0 100 0 10S 0 110 0 115 0 ;:: ~ Figure 17. The Eocene of Western Indonesia. "'"~. ~ '1 SEQUENCE STRATIGRAPHY APPLIED TO THE HYDROCARBON PRODUCTIVE BASINS OF WESTERN INDONESIA 385 the Sinamar-l well which penetrated over 1200 m Tanjung-l well in the marine part of the Tanjung of Eocene sediments without reaching the Formation. Kusuma and Darin (1989) cite a Middle Palaeocene or Pre-Tetriary. The lower 877 m of the Late Eocene age for the foraminifera and then assign drilled section comprised continental sediments with the whole Stage 3 of the Tanjung Formation in minor littoral influx. Further north ?Eocene to which they occur to the Middle Eocene (47.5 Ma- Early Oligocene marine sediments are reported from 44.5 Ma) and their overlying Stage 4 (Middle Central and North Aceh (Cameron et al., 1980) and Eocene-Early Oligocene) is "terminated by a drastic offshore Northeast Sumatra the ONS D-l well is eustatic sea level fall". As noted earlier there is a reported to have reached TD in volcanics which are strong possibility that Kusuma and Darin are using apparently of Middle Eocene age. the old BPM T.ab interpretation as BPM were the Several authors (Blum, 1994) have highlighted original operators of the Tanjung field. the fact that base level changes in the marine part In contrast PERTAMINA-BEICIP (1985) cite of a basin affect the non-marine section more than the earliest datable larger foraminifera as being of 100 km landward of the shoreline. It is thus T.b (Late Eocene) and T.cd (Early Oligocene) age. reasonable to expect that the non-marine Volcanics are reported from the Tanjung field in equivalents of these many examples of Late Eocene the zone immediately below the foraminifera, but to Early Oligocene marine sediments may be as far as is known they have not been dated. Several preserved in what were the landward parts of the authors (van de Weerd and Armin, 1992) give a palaeo-drainage systems and are now the deeper Late Eocene age to the Keliam volcanics some 250 syn-rift sections of the North, Central and South km to the North of the Tanjung field and Bauman Sumatra, Sunda, Northwest Java, Central Java (1972) has described Late Eocene and Oligocene Pati and East Java Basins. It is also to be expected deep marine shales with rare basalt flows overlying that these non-marine sediments will exhibit the Middle Eocene non-marine to shallow marine major sequence boundaries on seismic sections and clastics. In addition a weak Middle Oligocene on electric logs. With this in mind and using the unconformity is reported by van de Weerd et al. additional control of KlAr age determinations of (1987) and Saller et al. (1992) point out that the volcanics, where volcanics are present and age major eustatic sea level fall predicted by Haq et al. determinations are available, a log correlation of (1987) is not recognised in Central Kalimantan. the TA4 Supercycle is shown in Figures 18A-D. A review of all available data and a re Reliable biostratigraphic data is available for correlation of the data provided by Kusuma and the well from the Pamusian Rift in the Northeast Darin (1989) with the data included in Waluyo et Kalimantan basin (Fig. 18D) allowing a reliable tie al. (1986) combined with the alternative to seismic (see Courteney and Williams, 1994). To interpretations above, strongly suggests that Stage the south many wells in the Kutei basin penetrated 3 of the Tanjung Formation as defined by Kusuma Middle Eocene and Late Eocene sediments and and Darin (1969) is in fact located just below the volcanoclastics. For example, the Jelmusibak-l 36.0 Ma Sequence Boundary. This is illustrated by well drilled through 1,300 m of Early Oligocene the Kambitin-3 well on Figure 18D. The main deep marine shales, about 410 m of Late Eocene producing zone in the Kambitin field is from sands shallow marine clastics and 2000 m of non-marine ofthe third order cycle above the 39.5 Ma Sequence conglomerates, sandstones and shales (van de Boundary and they can be correlated to the sands Weerd et al., 1987). The well reached TD in these in the main producing zone of the Tanjung field. non-marine sediments. The combined thickness of The sands are designated 'Z-860' are described by over 3710 m is one of the thickest sections known Kusuma and Darin (1989) as: "distributary channel in Western Indonesia. No age determinations older sands incised into the underlying unconformity than P.12 (Middle Eocene) are known surface". They are interpreted by the author as (PERTAMINA-BEICIP, 1985), however, thick basal being Late Eocene in age as opposed to the Middle conglomerates and non-marine sandstones are Eocene of Kusuma and Darin (ibid). reported by many authors (van Bemmelen, 1949; A correlation with the Late Eocene Ngimbang Wain and Berod, 1989; van de Weerd et al., 1987) clastics of the Lombok basin is suggested by which underlie the marine .sediments. A more lithological descriptions alone. The sequence detailed review of the available data on the Early stratigraphy log correlations are shown in Figure Tertiary sediments of the Kutei basin is given in 18C. The Pagerungan-l well is tied to Courteney and Williams (1994). biostratigraphy and the source rock intervals In the Barito basin barren red beds underlie reported by Phillips et al. (1991) have been marked the deepest Eocene producing zone in the Tanjung on the log. The L-49-1 is reliably tied to planktonic field (Kusuma and Darin, 1989). The first datable foraminifera zones (Bransden and Matthews, 1992) foraminifera occur some 400 m higher in the and a possible source rock interval, attributed to July 1995 386 S. COURTENEY PAGERUNGAN·1 (Lombok Basin) PEMATANG·1 MONA·1 37.0 Ma 37.0Ma (C. Sumatra Basin) (Sunda Basin) -100m 30.0 Ma -100m GR 39.5Ma 39.5 Ma +100m +100 m Pre- Pre- Tertiary Tertiary +300m RI +500 m i-----'rl-+r~--___i Legend ~ Interval producing gas • Interval producing 011 S Signmcant source Interval s Minor source Interval (S) Possible source interval +700 m t------il---t-I"------; , Figure 18A. Correlation ofTA3 and TA4 Supercycles. BZZ FIELD JATIBARANG-88 GR RI 25.5 Ma -+-t~=----+.o::+-..o:.. ___=--+- -500 m+-' ..... ,....----1- ~---~~~~r-----~~OOm ",..+----..;T-i-I-or""'"----_+_ 30.0 Ma 30.0 Ma -r~=~:-t +-~----+-, ~---~~~.....".~----_t-300 m -100 m i--~ ~"";--+-~.-=-----i 1----+---1-+---..0&-----+ -100 m 39.5 Ma - 0 m -j-oliiiiii__ =---1~--'~-----I------_+-...z...... _I:"""'t_+--~ __--_+Om-39.5 Ma Pre-Tertiary ~I===-;~~~==='J,===~~~~~~= Pre- +100 m.l.·-----L...l------.,...-J Tertiary ~-~---I-+___\3f_----_t +100 m Figure 18B. Correlation ofTA3 and TA4 Supercycles, continued. SEQUENCE STRATIGRAPHY APPLIED TO THE HYDROCARBON PRODUCTIVE BASINS OF WESTERN INDONESIA 387 L 49·1 .-----.-...-----.,.. ·500 m 30.0 Ma -+--+--++-""""';.....--+- 30.0 Ma 1------4'--I-+-~--_I_ ·300 m PAGERUNGAN·1 ·200 m .,-----,....,..------, 37.0 Ma -f-~~__++~~----_I_------4-_+-_I__I_;_---4_37.0 Ma I---+--I-+---II~-_I_ ·100 m 39.5 Ma - 0 m+- ...... ~~+.:4_...... ;~ __-I- ______-+-l~ __ -I-~...:::;;;;;.r:...._....j. 0 m- 39.5 Ma +100 m +--~-I-+--.f-----l f----=lt--H-~;;;:_---+ +100 m Figure 18C. Correlation ofTA3 and TA4 Supercycles, continued. WELL IN PAMUSIAN RIFT (N.E. Kalimantan Basin) ,------,.....-----..,.-400 m KAMBITIN·3 (Barlto Basin) 725.5 Ma -+-_--...... -I---'~_-...... j- 725.5 Ma ·300 m -r------,-.,...------, 30.0 Ma 30.0 Ma 36.0 Ma -+--.....;+-+-Io+o,.:;a;;.~--~_ f----=;;"...... -HI----i>==----...... j. ·200 m ~_+_---.::i...... -+-I1--~--~36.0 Ma 39.5 Ma -0 m+--li.-.""""=:r--++,~~~--+_------....j..--~~_+_-~~-___+o m- 39.5 Ma Pre-Tertiary ===ll=::::::;;=::!::::*=~==:i!~====l= Pre-Tertiary +100 .J... ____L-L _____ -l m '-----.L...I------L+100m Figure 18D. Correlation ofTA3 and TA4 Supercycles, continued. JuLy 1995 388 S. COURTENEY the well's operator, is also indicated. Figure 19 in the centre of Figure 1IA. In the West N atuna shows a seismic line extending northward from the basin the seismic event below the Alu Alu E-1 and eastern end of the Pagerungan gas field. The Alu Alu E-4 wells is an example of the 39.5 Ma localised nature of the pre-39.5 Ma sediments and Sequence Boundary (Fig. 13). The TA4 Supercycle the thinning of the TA4 Supercycle is clearly visible. can also be correlated to the East Java basin on the To the west in the Northwest Java basin the basis of the characteristic seismic signature below sequence stratigraphy interpretation of the the 39.5 Ma Sequence Boundary. Soeparyono and Jatibarang-88 log (Fig. 18B) is constrained by the Lennox (1989) implied that this signature age of the volcanics. The Jatibarang structure is represented a different type of 'basement'. an inversion as shown in Figure 20. Thinning of The reservoirs of the TA4 Supercycle are the TA4 Supercycle is visible over the structure. To extremely restricted geographically in the basins of the west in the offshore part of the Northwest Java west Java, N atuna and Sumatra since they are basin and in the Central Sumatra and Sunda basins within the syn-rift sequences. In the basins of the the TA4 Supercyclesediments are barren of fossils greater east Java area and Kalimantan, where the and volcanics are also scarce. However, the rifts were filled and drowned earlier, the clastic correlation between Jatibarang-88 and the 'BZZ' reservoirs tend to be very thin and discontinuous field is felt to be reliable even though few seismic and the later carbonate reservoirs tend to be lines have been published in the area. The 'BZZ' developed on localised Pre-Tertiary highs in front log is in fact a composite ofthe BZZ-1 and BZZA-9 of the main carbonate platforms (e.g. Kerendan wells (Suria, 1991) in order to facilitate the gasfield). integration into the sequence stratigraphy TA4 Supercycle reservoirs account for only framework of the source rock data of Noble et al. 5.24% ofthe 'in-place' reserves of Western Indonesia (1991). (Fig. 22). The largest field producing from this In the Sunda basin the 39.5 Ma Sequence Supercycle is the Pagerungan gasfield in the Boundary in Mona-1 (Fig. 18A) can be tied to a Lombok basin. regional seismic event that can be followed to the eastern flank of the basin (Fig. 12B). The thickness Tejas A3 (TA3) Supercycle of the TA4 Supercycle in this basin is more The identification of the 39.5 Ma Sequence regionally consistent than the interpretation of boundary implies that sediments between it and Prayitno et al. (1992) which assigns the same the Pre-Tertiary, assuming a further major sequence sediments to the interval 32.0 Ma to 26.0 Ma and boundary is not recognised, are part of the TA3 does not recognise the Middle Oligocene Supercycle. unconformity, which, unlike Central Kalimantan, Such sediments can be seen in the Central is regionally significant in the Western Java Sumatra (Figs. 8, 18A and 21), South Sumatra Sumatra area. (Figs. lIA and lIB), Sunda (Figs. 12B and 18A), In the Central Sumatra basin Longley et al. Northwest Java (Figs. 18B and 20), East Java (Fig. (1990) published detailed well to seismic correlations 15), Lombok (Figs. 18C and 19), Barito (Fig. 18D), of the Pematang source rocks in the Melibur - "TA" Northeast Kalimantan (Fig. 18D) and West Natuna Trough area. Figure 21 has been modified from the (Fig. 13) basins. Sediments from this Supercycle original of Longley et al. (1990) to show the sequence are known from the Kutei basin and Courteney and stratigraphy interpretation. The regionally Williams (1994) have identified them on seismic significant 30.0 Ma Sequence Boundary is clearly data in the North Sumatra basin. Courteneyand visible and the more localised 39.5 Ma Sequence Williams (1994) further argue that the TA3 Boundary is represented by the 'classic' low Supercycle contains the main effective source rocks frequency/high amplitude seismic event. Figure of Western Indonesia. 18A shows the Pematang type section from the The reservoirs of the TA3 Supercycle account Pematang-1 well (PERTAMINA-BEICIP, 1985) in for 0.67% of the estimated 'in-place' reserves of the northern Arnan Depression, Central Sumatra. Western Indonesia. They are normally very poor The relatively thin TA4 Supercycle in the well reservoirs deep in the syn-rift sequences and indicates that it is also an inversion similar to the produce in such fields as the Pematang oilfield, one illustrated in Figure 8 which is also from the Central Sumatra (Fig. 18A), and in the Tanjung northern Arnan Depression. oilfield, Barito basin. Similar log responses from wells drilled on inversion structures (e.g. the Limau fields) and Tejas A2 (TA2) Supercycle seismic events deep within the syn-rift can be Sediments belonging to the TA2 Supercycle have recognised in the South Sumatra basin. For been reported from the Lombok basin and are example, the reflections around 3.0 seconds TWT possibly present in the rift remnant shown in Figure GeoL. Soc. MaLaYJia, BuLLetin 37 enm 0 c zm () m en --I :0» LOMBOK BASIN, NORTHERN PLATFORM --I 15 :0» -U I N JS 53A·1 PAGERUNGAN·4 .n. S -< » (ProJected) • (Projected) v -U -U 0.0 mr on~~~------~~------+-~------+------0 15.5 Ma --I 0 --I I m I 10.5 Ma 21.0 Ma -< 0 1.0 1.0 :0 0 »() 21.0 Ma--- 25.5 Ma :0 30.0 Ma !D 25.5 Ma 0 39.5 Ma z -u 30.0 Ma :0 0 2.0 0 c 39.5 Ma () --I <: m »!D en Z en 0 -n ~ m en I 2km I --I m :0z Z Reinterpretation of a seismic section from Phillips et aZ., 1991. 0 0 Z m Figure 19. Lombok basin sequence stratigraphy. en 5> w 00 <0 390 S. COURTENEY N.W. JAVA, JATIBARANG AREA JATIBARANG SINDANG SE FIELD FIELD NW 0.0 ---~------~ 0.0 21.0MJ·~!15'5Ma-+-';;IIIEiillll=Ir=~~5 25.530.0Ma-+- Ma-+ ~~~ ~ Top ~.:;..;t:: 3.0 , 4km , Reinterpretation of seismic section from Adnan et at., 1991. Figure 20. Northwest Java basin sequence stratigraphy. CENTRAL SUMATRA: MELIBUR • "TA" TROUGH sw • MSTA-2 NE 10.5 Ma-+~~= 15.5 2km Modified from Longley et al., 1990. Figure 21. Central Sumatra: Melibur - "TA Figure Captions, Page 2" Trough. Ceo!. Soc. MaLaY.Jia, BuLLetill 37 SERIES STAGES AGE NORTH CENTRAL SOllTH SUNDA NORTHWEST CENlRAL EAST JAVA NORTEAST LOMBOK BARITO KUTEI NORTHEAST EAST WEST " Eslimat ed (Ma) SUMAlRA SUMAlRA SUMATRA JAVA JAVA JAVA KALIMANTAN NATUNA NAT UNA "In.pl..,." • PAn Reserves 1.65 2.94 6.5 T83 22.57 10.5 18.80 16.5 T82 14.87 21.0 21.96 26.5 T81 12.81 OLIGO- 30.0 CENE 5.24 TA4 39.5 44.0 0.67 TA3 49.5 63.0 TA2 PALEO- CENE Base Sediments TA1 68.0 CLUne CAABONAn [2J VOLCAHIC EF~ POSSIlLf EFRCllVE EIl RESERVOIRS G::J RESERVOIRS RESERVOIRS -SOURCf ROCI warm-water sediments. Bol. Informativo,Assoc. Venezolana Ann. Conv. IPA, 1, 117-137. de Geol., Min. y Pet., 8, 5. KUSUMA, I. AND DARIN, T., 1989. The hydrocarbon potential of BOOMGART, L., 1949. Smaller foraminifera from Bodjonegoro the lower Tanjung Formation, Barito basin, S.E. Gava). Diss. Univ. Utrecht, 175p. Kalimantan. Proc. 18th Ann. Conv. IPA, 1, 107-138. BRAMLETTE, M.N. AND WILCOXON, J.A., 1967. Middle Tertiary LONGLEY, I.M., BARRACLOUGH, R, BRIDDEN, M.A. AND BROWN,S., calcareous nanoplankton of the Cipero section, Trinidad, 1990. Pernatang lacustrine petroleum source rocks from West Indies. Tulane Studies in Geology, 5(3), 93-131. the Malacca Strait PSC, Central Sumatra, Indonesia. BRANSDEN, P.J.E. AND MATTHEWS, S.J., 1992. Structural and Proc.19th Ann. Conv. IPA, 1,279-297. stratigraphic evolution of the East Java Sea, Indonesia. MARTINI, E., 1971. Standard Tertiary and Quaternary Proc. 21st Ann. Conv. IP A, 1, 417-453. calcareous nannoplankton zonation. In: Farinacci, A. BURNAMAN, M.D., HELM, RB. AND BEEMAN, CR, 1985. Discovery (Ed.), Proc. 2nd Conf. Planktonic Microfossils Rome 1970,2, of the Cunda gas field, Bee block, North Sumatra: an 739-785. integrated geological seismic stratigraphy case history. MASERA-AAPG DATA SYSTEMS, 1991. International Proc.14th Ann. Conv. IPA,l,453-496. Developments in Exploratory Drilling, 1950-1990 (AAPG CAMERON, N.R CLARKE, M.CG., AWISS, D.T. AsPDEN, J.A. AND Bulletin), A set of CD ROMs. DJUNUDDIN, A., 1980. The geological evolution of Northern MEYER, H., 1943. A compilation of the results of geological Sumatra. Proc 9th Ann. Conv. IPA, 149-187. and geophysical exploration work done during recent CAMERON, N.R, 1983. The stratigraphy of the Sihapas years in the Tertiary basin of North Sumatra. Report for formation in the northwest of the Central Sumatra basin. the Japanese Imperial Army Engineers, incomplete, GRDC Proc. 12th Ann. Conv. IP A, 1, 43-65. Library, Bandung, Indonesia. COURTENEY, S. , COCKCROFT, P., MILLER, R, PHOA, RS.K. AND MOURET, C, 1987. Stratigraphy and structural evolution of WIGHT, A.W.R (EDS.), 1989. PERTAMINA - IPA Oil & the Melawi basin (West Kalimantan, Indonesia) in its Gas Fields Atlas, Volume W, Java. regional setting. Paper presented at the 16th Ann. Conv. COURTENEY, S. AND WILLIAMS, H.H., 1994. The Palaeogene rifts IPA. of Western Indonesia. Paper presented atAAPG Annual MULHADIONO AND SUTOMO, lA., 1984. The determination of Meeting - Analogs for the World, Denver. economic basement of rock formation in exploring the DE COSTER, G.L., 1974. The geology of the Central and South Langkat-Medan area, North Sumatra basin. Proc.13th Sumatra basins. Proc. 3rd Ann. Conv. IPA, 77-110. Ann. Conv. IPA, 1,75-107. DURHAM, J.W., 1939. Mountain Front stratigraphy in Central NOBLE, RA., Wu, CH. AND ATKINSON, CD., 1991. Petroleum Sumatra. NPPM internal report. generation and migration from Talang Akar coals and DUVAL, B.C, CHOPPIN DEJANVRY, G. AND LOIRET, B., 1992. The shales offshore N.W. Java, Indonesia. Org. Geochem., Mahakam delta province: An ever changing picture and 17(3),363-374. a bright future. Proc. 24th Ann. OTC, 393-404. NUTT, W.L. AND SIRAIT, J., 1985. Application of offset seismic FAINSTEIN, R, 1987. Exploration of the North Seribu area, profiles in the Jatibarang volcanic reservoir. Proc. 14th northwest Java sea. Proc.16thAnn. Conv.IPA,l,191-214. Ann. Conv. IP A, 2, 385-406. GSELL, R., 1930. Geologische Untersuchungen in der P ATMOSUKISMO, 5., SYAHBUDDIN, A. AND ALAMEDA, G., 1985. New Umgebung von Batoeradja. BPM internal report. seismic method in populated areas (a case study in the HADI, T. AND SIMBOLON, B., 1976. The carbonate rocks of the Surabaya area, East Java, Indonesia). Proc. 14th Ann. Baturaja Formation in its type locality, Baturaja, South Conv.IPA,l,405-435. Sumatra. Proc. IPA Carbonate Seminar, 67-78. PERTAMINA~BEICIP, 1982. Petroleum Potential of Eastern HAQ, B.U., HARDENBOL, l AND VAIL, P.R, 1987. Chronology of Indonesia. Multiclient Report. fluctuating sea levels since the Triassic. Science 235, PERTAMINA-BEICIP, 1985. Petroleum Potential of Western 1156-1167. Indonesia. Multiclient Report. HARDING, T.P., 1983. Structural inversion at Rambutan oil PERTAMINA-BEICIP, 1994. Global geodynamics, basin field, South Sumatra basin. In: Bally, A. W. (Ed.), Seismic classification and exploration play-types in Indonesia. Expression of Structural Styles, AAPG Studies in Geology, Multiclient Report. 15(3),3.3-13 - 3.3-18. PHILLIPS, T.L., NOBLE, RA. AND SINARTIO, F.F., 1991. Origin of JORDAN, CF., JR. AND ABDULLAH, M., 1992. Arun Field - hydrocarbons, Kangean block Northern Platform, Indonesia. In: Foster, N.H. and Beaumont, E.A. (Eds.), offshore northeast Java Sea. Proc. 20th Ann. Conv. IP A, 1, Stratigraphic Traps III. Treatise of Petroleum Geology, 637-661. Atlas of Oil and Gas Fields, 1-39. PRAYITNO, W., ARMON, J.W. AND HARYONO, 5., 1992. The KARlG, D.E., SUPARKA, 5., MOORE, G.F. AND HEHANUSSA, P.E., implications of basin modelling for exploration - Sunda 1979. Structure and Cenozoic Evolution of the Sunda basin case study, offshore Southeast Sumatra. Proc.21st Arc in the Central Sumatra Region. In: Watkins, J.S., Ann. Conv. IPA, 1, 379-415. Montadert, L. and Wood Dickerson, P. (Eds.), Geological SALLER, A., ARMIN, R.A., ODE IcHRAM, L. AND GLENN-SULN AN, and Geophysical Investigations of Continental Margins. C,1992. Sequence stratigraphy of Upper Eocene and AAPG Mem. 29, 323-358. Oligocene limestones, Teweh area, Central Kalimantan. KIRBY, G.A., SITUMORANG, B. AND SETIARDJA, B., 1989. Seismic Proc. 21st Ann. Conv. IPA, 1, 69-92. stratigraphy of the Baong and Keutapang Formations, SANTOSO, H., BERMAWI, A. AND MURHANTORO, E., 1990. Combined North Sumatra basin. Proc.18th Ann. Conv. IPA, 1,289- interpretation of gravity with seismic and well data 301. using stripping technique. Proc. 19th Ann. Conv. IPA, 1, KONING, T. AND AULIA, K., 1985. The petroleum geology of the 131-146. Ombilin intermontane basin, West Sumatra. Proc.14th SARG,J.F., 1988. Carbonate sequence stratigraphy. In: Wilgus, July 1995 394 S. COURTENEY C.K., Hastings, B.S., Kendall, c.G.St.c., Posamentier, of the Tertiary hydrocarbon-bearing basins in Kalimantan H.W., Ross, C.A and van Wagoner,J.c. (Eds.), Sea-level (Borneo), Indonesia. Bull. Am. Assoc. Pet. Geol., 76(11), changes: An integrated approach. SEPM Spec. Pub. 42, 1778-1803. 155-181. VAN DER VLERK, I.M. AND UMBGROVE, J.H.F., 1927. Tertiaire SCHILLER, D.M., GARRAD, RA AND PRASETYO, L., 1991. Eocene gidsforaminifern van Nederlandsch Oost-Indie. submarine fan sedimentation in southwest Java. Proc. Wetensch. Meded. Dienst Mijnbouw Ned. Oost-Indie, 6, 3-31. 20th Ann. Conv. IPA, 1, 125-181. VANDooRNINK,H.W., 1932. TertiarynummulitidaefromJava. SCHLUMBERGER, 1986. Formation Evaluation Conference,Indonesia, Verh. Geol. Mijnb. Gen. 9. 332p. VAN GORSEL,J.T., 1988. Biostratigraphy in Indonesia: methods, SOEPARYONO, N. AND LENNOX, P.G., 1989. Structural pitfalls and new directions. Proc.17th Ann. Conv. IPA, 1, development of hydrocarbon traps in the Cepu oil fields 275-300. northeast Java, Indonesia. Proc: 18th Ann. Conv. IPA, 1, WAHAB, A, 1986. Hydrocarbon potential of KIingi Area, 139-156. South Sumatra. Jour. Ikatan Ahli Geologi Indonesia (lAG!), SOERIA-ATMAD)A, R, MAURY, RC., BELLON, H., PRINGGOPRAWIRO, 11,2,7-10. H., POLVE, M. AND PRIADI, B., 1994. Tertiary magmatic WAIN, T. AND BEROD, B., 1989. The tectonic framework and belts of Java. Jour. SE Asian Earth Sciences, 9(1/2), 13-27. paleo-geography of the upper Kutei basin. Proc. 18th SUNARYO, R, MARTOD)O)O, S. AND WAHAB, A, 1988. Detailed Ann. Conv. IP A, 1, 55-78. geological evaluation of the hydrocarbon prospects in WALUYO, YULIAN, B. AND HADI, T., 1986. Aplikasi interval the Bungalun Area, East Kalimantan. Proc 17th Ann. velocity untuk menentukan sand shale ratio dalam Conv. IPA, 1,423-446. hubungannya dengan eksplorasi minyak dan gasbumi SURIA, c., 1991. Development strategy in the BZZ field and di daerah Kambitin-Bagok, Kalimantan Selatan. Proc. the importance of detailed depositional model studies in XV Ann. Conv. IAGI, 35p. the reservoir characterisation of Talang Akar channel WESTERVELD, J., 1941. Three geological sections across South sandstones. Proc. 20th Ann. Conv. IPA, 1,419--452. Sumatra. Kon. Ned. Akad. v. Wetensch., Amsterdam, Proc., SUTARSO, B. AND SUYITNO, P., 1976. The diapiric structures and 44, 1131-1139. its relation to the occurrence of hydrocarbon in North WID)ONARKO, R, 1990. BD Field -- A case history. Proc.19th east Java basin. Paper presented a 5th Ann. Meet. IAGI, 46p. Ann. Conv. IPA, 1, 161-182. SUTOTO, A, 1991. Reservoir geology of the Belida field, south WIGHT, AW.R, SUDARMONO AND IMRON, A, 1986. Stratigraphic Natuna Sea, Block 'B'. Proc. 20th Ann. Conv. IPA, 1,453- response to structural evolution in a tensional back-arc 478. setting and its exploratory significance: Sunda basin, 'T HOEN, C.W.AP., 1922. De tertiaire petroleum terreinen ter West Java Sea. Proc. 15th Ann. Conv. IPA, 1, 77-100. Oostkust van Aljeh (Aljeh 11). Jaarb. Mijnw. Ned. Ind., WILLIAMS, H.H., KELLEY, P.A., JANKS, J.S. AND CHRISTENSEN, 1919, Verh. I, Batavia. RM., 1985. The Paleogene rift basin source rocks of VAN BEMMELEN, RW., 1949. The geology of Indonesia. The Central Sumatra. Proc.14th Ann. Conv. IPA, 2, 57-90. Hague, Government Printing Office, 732p. WIR)ODIHARD)O, K., 1992. Seismic reef expressions in the North VAN DE WEERD, A., ARMIN, RA., MAHADI, S. AND WARE, P.L.B., Sumatra basin. Proc. 21st Ann. Conv. IPA, 1, 117-144. 1987. Geologic setting of the Kerendan gas and WONGSOSANTIKO, A, 1976. Lower Miocene Duri Formation condensate discovery, Tertiary sedimentation and sands, Central Sumatra basin. Proc. 5th Ann. Conv. IP A, palaeogeography of the northwestern part of the Kutei 133-150. basin, Kalimantan, Indonesia. Proc.16th Ann. Conv. IPA, ZELIFF, C.W., TROLLOPE, S.W. AND MAULANA, E., 1985. 1,317-338. Exploration cycles in the Corridor block, South Sumatra. VAN DE WEERD, A AND ARMIN, RA, 1992. Origin and evolution Proc.14th Ann. Conv. IPA, 1, 379--400. ------.~.-~-+.~.------Manuscript received 24 October 1994 Ceo!. Soc. Ma!aYJia, Bulletill 37