7. SUMATRA. Petroleum Geology of Indonesia : Current Knowledge. Regular HAGI Course Yogyakarta, 2 6 August by : Awang Harun Satyana

Transcription

1 Petroleum Geology of Indonesia : Current Knowledge Regular HAGI Course Yogyakarta, 2 6 August SUMATRA Minangkabau architecture by : Awang Harun Satyana

2 SUMATRA

3 Barber et al. (2005)

4 Simandjuntak and Barber (1996)

5 SUMATRA MAJOR TECTONIC ELEMENTS The Sunda Shelf borders the back arc basin to the east Asahan Arch, Bukit Tigapuluh Mountains and Lampung High partitions the back-arc basins The Bukit Barisan Range : Neogene Magmatic arc, separates the back-arc basins from West Sumatra forearc basins The Outer Arc Islands : accretion wedges The Sumatra trench: an oblique subduction zone

6 SUMATRA BACK ARC BASIN MODEL Koesoemadinata (2006)

7 Sumatra Pre-Tertiary Basement Pre Tertiary rocks are exposed in the Barisan Range, Tigapuluh Mountains and Lampung High. Sumatra Pre-Tertiary rocks have been analyzed into separate terranes consisting of : highly tectonized Paleozoic and Mesozoic terranes Paleozoic to Mesozoic intrusive rocks Melange (ophiolitic rocks). Pre-Tertiary terranes are interpreted as a collage of Asian and Gondwanan microcontinents.

8 Microplate boundaries Pertamina and Beicip (1985)

9 SUMATRA TERTIARY BASINS Back-arc and partly fore-arc basins are underlain by continental crust. The magmatic arc, Barisan Range, uplifted Pre-Tertiary rocks forms border to the basins. Paleogene rift basins extend from back-arc to fore-arc basins across the Bukit Barisan. Volcanism is limited to Paleogene (in the Southwest) and Plio-Pleistocene. The presence of the Great Trans-Sumatra wrench fault (Semangko Fault) along the Bukit Barisan.

10 Barber et al. (2005)

11 North Sumatra Basin Central Sumatra Basin South Sumatra Basin Sedimentary basins of Sumatra

12 Stratigraphy of Sumatra back-arc basins Samuel and Gultom (1986)

13 Sumatra Tectono-Stratigraphic System From top to base : Syn-orogenic deposition in a back-arc basin : regressive (Mid-Miocene-Recent) rising Barisan Range clastic source Post-rift deposition in a shelfal basin : transgressive (Early Miocene) Sundaland clastics source and carbonates Syn-rift deposition in active rift-valley basins : one or more rift phases (?Eocene-Oligocene) local clastic source

14 Sumatra Major Fault System THE TRANS SUMATRA STRIKE-SLIP FAULT SYSTEM : active since Early Tertiary times THE PALEOGENE BASEMENT FAULT SYSTEM : This fault system resulted in the Paleogene graben-half-graben system with syn-rift deposition The Sumatra Paleogene Fault System extends SE to the NW Java basinal area

15 Sumatra Fault System Koesoemadinata (2006)

16 The Paleogene Basement Fault System This fault system consists of two main components N-S component WNW-ESE component In South Sumatra a NE-SW component is present This fault system cuts clear across the Barisan Range, beneath the fore-arc basin. This fault system is responsible for the development of Paleogene graben- halfgraben basin system with syn-rift deposition forming important oil kitchens.

17 Murphy (2000)

18 Sumatra Paleogene Fault System Koesoemadinata (2006)

19 Paleogene Basement Faults Explanation Moulds (1989): Faults are mainly N-S and was created due to the E-W directed extensional regime during the initial stage of the N-S directed stress caused by the subduction. Other explanation: transtensional faults due to the dextral wrenching movements of the Indian Ocean Plate relative to the Sunda continental plate

20 The Neogene Fold system The fold system is dominated by the WNW-ESE trending anticlinoria. Generally forming an en-echelon pattern. Explanation: Wrench movement along the NW-SE basement faults (related to the Paleogene graben system) (Harding,1988) Draping over uplifted blocks due to compressive regime of the subduction (Moulds, 1989)

21 North Sumatra Basin The basin is notable for the first commercial oil field the Telaga Said field (discovered 1885) and the giant Arun gas field. The basin is extremely large and extends from just north of Medan northwards for several hundred kms into the Andaman Sea and across the Thailand Indonesia border. The Indonesian sector of the basin is bordered to the west by the Barisan Mountain thrust system and to the east by the stable Malacca platform. Onshore sector of the basin has been extensively explored, however, remaining potentials include : gas filled Peutu carbonate buildups, Belumai buildups on the Malacca shelf, Baong and Keutapang stratigraphic play, lowstand turbidite fan systems of middle Miocene (Tsukada et al., 1996; Nur aini et al. 1999), latest Oligocene Bampo fan systems, syn rift Parapat in graben deeps, Eocene Tampur carbonates (Ryacudu and Sjahbuddin, 1994). Relatively unexplored northern deepwater (> 1000 m water depth) sector of the basin merits further investigation.

22 NORTH SUMATRA BASINAL AREA Koesoemadinata (1994)

23 North Sumatra Crustal Section Koesoemadinata (1994)

24 Pertamina and Beicip (1985) North Sumatra Basin

25 Generalized physiography and productive HC discoveries of the North Sumatra basin Netherwood (2000)

26 Cross section across Barisan uplift and Southern NSB Pertamina and BPPKA (1996)

27 Cross section across North Sumatra Basin Pertamina and BPPKA (1996)

28 Cross section across NE corner of Barisan uplift Pertamina and BPPKA (1996)

29 North Sumatra Eocene Basin Configuration Davies (1984)

30 North Sumatra Basement Eocene Davies (1984)

31 North Sumatra Basin Oligocene Development Davies (1984)

32 North Sumatra Basin : Miocene Davies (1984)

33 North Sumatra Basin : Pliocene Davies (1984)

34 North Sumatra Basin : Present Davies (1984)

35 Pertamina and Beicip (1985)

36 Stratigraphic nomenclature of North Sumatra Basin Caughey and Wahyudi (1993)

37 North Sumatra Stratigraphy

38 North Sumatra Stratigraphic Diagram Synorogenic Post-rift Syn-rift

39 ENI (2002) Chronostratigraphic scheme for northern part of the North Sumatra Basin

40 North Sumatra Petroleum System Source Rocks and Migration Reservoir Rocks Clastics : Belumai Sands, Baong Sands, Keutapang, Seurula sands Carbonates : Early Miocene Reefs Seals Trapping Conditions Stratigraphic Structural

41 ENI (2002) Stratigraphy and Petroleum System of North Sumatra Basin

42 Petroleum system of North Sumatra basin Pertamina and BPPKA (1996)

43 Pertamina and BPPKA (1996)

44 Pertamina and BPPKA (1996)

45 BAONG Pertamina and BPPKA (1996)

46 Pertamina and BPPKA (1996)

47 Pertamina and BPPKA (1996)

48 Pertamina and BPPKA (1996)

49 Deepwater North Sumatra Basin ENI (2002)

50 Central Sumatra Basin The Central Sumatra Basin is the most prolific oil basin in SE Asia. Reserves estimates for the basin of 13 BBOE ultimately recoverable, of which 2.5 BBO remain to be recovered (Sujanto, 1997). The basin is mature with respect to HC exploration with a simple and essentially single petroleum system operating. New ideas are required if further fields are to be discovered and trend of declining production to be halted.

51 Basement tectonostratigraphic map Pertamina and BPPKA (1996)

52 Basement tectonostratigraphic correlation chart Pertamina and BPPKA (1996)

53 CENTRAL SUMATRA BASINAL AREA

54 Central Sumatra Basinal Area Regional Seismic Section Mertosono and Nayoan (1974)

55 Pertamina and Beicip (1985) Central Sumatra Basin

56 Central Sumatra Rift Basins

57 Central Sumatra Paleogene Rift Basins

58 Mertosono and Nayoan (1974)

59 Eocene Oligocene F1 (45 Ma-26 Ma) regional structure map Pertamina and BPPKA (1996)

60 Miocene Recent F2-F3 (26 Ma-0 Ma) structure map Pertamina and BPPKA (1996)

61 Pertamina and BPPKA (1996)

62 Heidrick and Aulia (1993)

63 Mertosono and Nayoan (1974)

64 Central Sumatra tectonostratigraphic chart Pertamina and BPPKA (1996)

65 Stratigraphic nomenclature of Central Sumatra Basin Wain and Jackson (1995)

66 Central Sumatra Stratigraphic Diagram Atlas IPA (1991)

67 Central Sumatra Chronostratigraphy

68 Central Sumatra Petroleum System Central Sumatra is the most prolific petroleum in the Indonesian Basin. Source rocks and oil kitchen are exclusively synrift deposits (Brown shales of the Pematang Group). Reservoirs are exclusively clastics of the post rift transgressive Sihapas group. Trapping is provided by structural traps with stratigraphic components.

69 Central Sumatra petroleum system events chart Pertamina and BPPKA (1996)

70 Central Sumatra Basinal Area Miocene Duri Delta

71 Katz and Dawson (1997)

72 Cross plot of TOC and hydrogen index (HI) Pertamina and BPPKA (1996)

73 Kerogen assemblage dominated by fluorescent amorphinite (A) and degraded, freshwater Botryococcus (FWA) in Brown Shale formation, Central Sumatra basin. Netherwood (2000)

74 Brown shale isopach map in Pematang trough Pertamina and BPPKA (1996)

75 Central Sumatra regional heat flow map Pertamina and BPPKA (1996)

76 Paleogene depocenters, generalized structure and oil field distribution for the Central Sumatra basin Praptono et al. (1991)

77 Field distribution along regional, north-south trending dextral transcurrent faults in the coastal plains block of Central Sumatra Heidrick and Aulia (1993)

78 Netherwood (2000)

79 Sihapas reservoir of Bekasap formation in Minas field Pertamina and BPPKA (1996)

80 Central Sumatra Oil Fields Gas fields are practically non-existence Minas and Duri field are the main oil fields and can be classified as giant field.

81 F2 F3 Duri field and seismic profile Pertamina and BPPKA (1996)

82 F2 F3 East Kayuara field and seismic profile Pertamina and BPPKA (1996)

83 F2 F3 Kotabatak field and seismic profile Pertamina and BPPKA (1996)

84 F2 F3 Lalang field and seismic profile Pertamina and BPPKA (1996)

85 F2 F3 Libo SE field and seismic profile Pertamina and BPPKA (1996)

86 F2 F3 Lirik field and seismic profile Pertamina and BPPKA (1996)

87 F2 F3 Melibur field and seismic profile Pertamina and BPPKA (1996)

88 F2 F3 Minas field and seismic profile Pertamina and BPPKA (1996)

89 F2 F3 Parum field and seismic profile Pertamina and BPPKA (1996)

90 F2 F3 Petani field and seismic profile Pertamina and BPPKA (1996)

91 South Sumatra Basin The basin contains diverse petroleum systems, with both oil and gas being sourced from lacustrine and fluvio-deltaic terrestrial facies. Limited potential still remains for the traditional Talang Akar and Batu Raja formation plays. In contrast to the basin s mature oil status, the South Sumatra Basin is under-explored for gas, and contains good remaining gas potential in both new and existing successful plays. A further 6 to 10 TCF gas could be discovered in the basement, Talang Akar, and Batu Raja.

92 SOUTH SUMATRA BASINAL AREA Koesoemadinata (1994)

93 South Sumatra Crustal Cross-Section Koesoemadinata (1994)

94 South Sumatra Basin Outline

95 SOUTH SUMATRA BASINAL AREA JAMBI SUBBASIN NORTH PALEMBANG SUBBASIN CENTRAL PALEMBANG SUBBASIN SOUTH PALEMBANG SUBBASIN

96 South Sumatra structural framework Pertamina BPPKA (1996)

97 South Sumatra Basin Pertamina and Beicip (1985)

98 South Sumatra Sub-Basins

99 South Sumatra Paleogene Graben Halfgraben System

100 South Sumatra Paleogene Graben System The graben system is more complex than else where in Sumatra. In addition to the N-S-NW-SE system there is an additional NNE-SSW set. It consists mainly of half-grabens, facing west as well as east. The half-grabens are inverted with NW-SE set turning into a thrusted fold belts, described as flower structure. Ryacudu (2005)

101 Jambi Graben System A NNE-SSW complex graben system. Unique among the SW Sunda graben being not N-S oriented. Due to extension phase following a pre-existing major basement fault extending from Bukit Barisan to Singkep Island. This graben system becomes the site of the huge Jambi Depression in the Neogene.

102 South Sumatra Basin Tectonic Development (1) west east Koesoemadinata (1994)

103 South Sumatra Basin Tectonic Development (2) west east Koesoemadinata (1994)

104 Yulihanto and Sosrowidjoyo (1996) Generalized structural pattern of South Sumatra Basin

105 Basement terrains of South Sumatra Basin Ginger and Fielding (2005)

106 Structural styles of South Sumatra Basin Ginger and Fielding (2005)

107 South Sumatra surface structures Pertamina BPPKA (1996)

108 Stratigraphic Correlation of Central and South Sumatra Basins De Coster (1974)

109 Pertamina and Beicip (1985)

110 South Sumatra Stratigraphic Diagram Atlas IPA (1991)

111 South Sumatra Petroleum System Source Rocks and Oil Kitchens Migration Reservoir Rocks : Basement Talangakar sands Baturaja carbonates Air Benakat sands Muara Enim sands Seals Trapping Condition Structural Traps Stratigraphic Carbonate Build-ups

112 South Sumatra Oil and Gas Fields (Examples of Fields) Fractured basements : Suban, Sumpal, Sambar. Talangakar sandstones : Talang Akar, Pendopo, Benakat, Limau fields, some fields in Jambi. Baturaja carbonates : Ramba, Air Serdang, Kaji- Semoga. Air Benakat sandstones : old fields, Kampong Minyak, Rambutan. Muara Enim sandstones : old fields

113 Exploration history of the South Sumatra Basin Ginger and Fielding (2005)

114 Cummulative discovery curve for the South Sumatra Basin split by reservoirs Ginger and Fielding (2005)

115 Kerogen of South Sumatra Basin Netherwood (2000)

116 Present day maturity map on top basement Ginger and Fielding (2005)

117 Netherwood (2000)

118 Pertamina and BPPKA (1996)

119 Pertamina and BPPKA (1996)

120 Pertamina and BPPKA (1996)

121 Suban giant gas field : producing gas from multiple reservoirs (igneous-metamorphic rocks, siliciclastics and carbonates) Pujasmadi et al. (2002)

122 Depth structure map of top Baturaja Formation Stratigraphy of South Sumatra Basin Leached skeletal packstone of Baturaja carbonate Kaji-Semoga field : big discovery in an over 100 year explored-basin Hutapea (2002)

123 Oil grouping of South Sumatra Basin Ginger and Fielding (2005)

124 Intra-Arc Basins of Sumatra OMBILIN PASEMAH Darman and Sidi (2000)

125

126 Ombilin Rift Basin Early Stage

127 Ombilin Basin Central Sumatra Middle Stage

128 Ombilin Basin, Central Sumatra Late Stage

129 Stratigraphy of Ombilin Basin, West Sumatra

130 Kamal (2000) Tectonic setting of Pasemah Block, South Suamtra

131 Kamal (2000) Subsurface stratigraphy of Pasemah Block, South Suamtra

132 SUMATRA FORE-ARC BASINS Meulaboh Basin Sibolga Basin Mentawai Basin Bengkulu Basin Western Sumatra fore-arc basin are still underlain by continental crust, and Paleogene graben system extends underneath the Neogene fore-arc basin.

133 Fore-arc Basins Fore-arc basins have traditionally been considered poorly prospective for hydrocarbons due to : source-rock facies were unlikely to develop in these essentialy shallow, oxygenated, open-marine basins, Reservoir quality was assumed to be problem because nearby volcanic arcs and melange complex have supplied a predominance of poor-quality reservoirs, Geothermal gradients are relatively low. Six fore-arc basins of Western Indonesia have been drilled : Banyumas, South Central Java, Southwest Java, Bengkulu, Mentawai, Sibolga. The results, in some way, fuel optimism for the existence of economic petroleum reserves in the Western Indonesia fore-arcs.

134 West Sumatra Basin Petroleum System The fore-arc basins are considered cool basins. The fore-arc basins are less likely to contain hydrocarbons. Oil and gas occurrences are sourced from the synrift deposits, which experienced heating during the rifting process.

135 Simplified map of structural elements and HC occurrence in the Sumatra forearc Yulihanto et al. (1995)

136 Bengkulu-Mentawai-Sibolga Basins (1) The Bengkulu basin is the mostwidely explored fore-arc basin in Indonesia. All Bengkulu basin carbonate targets proved to be waterfilled. Arwana-1 (Fina, 1992) encountered good oil shows and penetrated good marine sources of Oligo-Miocene shales which are within the oil window with GG of C/100 m (this is significantly higher than normal fore-arc setting). The origin of the Bengkulu basin is not strictly fore-arc, may originally have been in back-arc setting (Howles, 1986; Mulhadiono and Asikin, 1989; Hall et al., 1993; Yulihanto et al., 1995). The Bengkulu basin has a proven petroleum system for oil generation. It demonstrates a similar geology to the South Sumatra basin, with an undrilled Paleogene rift system that could feasibly contain lacustrine source rocks, and proven post-rift reservoir facies. Post-rift Miocene shales and some coals are proven source facies.

137 Bengkulu-Mentawai-Sibolga Basins (2) Fieldwork in the Mentawai Islands shows that the marine Oligocene graben fill in the Mentawai basin has source potential. Basin modelling suggests that these sediments may have entered oil window as early as the middle Miocene. Early Miocene buildups are considered potential reservoir target. Some wells contain biogenic methane shows (Yulihanto and Wiyanto, 1999). Suma-1, Singkel-1 (Union Oil), and Ibu Suma-1 (Caltex) wells of Sibolga basin encountered sub-economic quantities of biogenic gas (Dobson et al., 1998) middle Miocene carbonate build ups. The traps have sealing problem. Interbedded sands may show better biogenic gas prospects.

138 Bengkulu Basin Rifting Yulihanto et al. (1995)

139 Stratigraphy of Bengkulu fore-arc basin Yulihanto et al (1995)

140 Bengkulu Basin Stratigraphic Column Manna Subbasin Yulihanto et al. (1995)

141 Yulihanto et al (1995) Tectonic setting of Bengkulu fore-arc basin

142 Yulihanto (2000) Stratigraphy of Mentawai fore-arc basin

143 Yulihanto (2000) Subsurface stratigraphy of Mentawai fore-arc basin

144 vide Murphy (2000) Stratigraphy of Nias, Sibolga fore-arc basin

145 Seismic section and interpretation of the middle Miocene Ibu Suma buildup, Sibolga basin, north Sumatra fore-arc Dobson et al. (1998)

146 Fore-Arc Basins : Conclusions Fore-arc basins of Western Indonesia are poorly understood but their hydrocarbon potential is considered to be moderate to high (Netherwood, 2000). The Bengkulu basin experienced a history similar to that of the backarc basins : Paleogene rifting, Miocene structural modification, inversion and raised heat flow in Pliocene-Pleistocene times. The Bengkulu basin demonstrates mature source potential, sufficient heat flow for oil generation, and convincing oils shows in wells. Presence of biogenic gas and low geothermal gradient in Sibolga Basin are promising for future biogenic gas exploration. Interbedded sands within early Miocene reefs will be better sealed than reefs. Numerous oil and gas seepages in Bayah and Banyumas areas demonstrate the presence of active petroleum system. The presence of excellent Eocene reservoirs is promising. The areas are worth for further exploration.