Low Energy Depositional Systems of SE Asia: Implications for Reservoir Characterisation. General Lecture. Prof. Joseph J. Lambiase

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1 Low Energy Depositional Systems of SE Asia: Implications for Reservoir Characterisation General Lecture Prof. Joseph J. Lambiase Department of Petroleum Geoscience Universiti Brunei Darussalam Yogyakarta, 22 May 2004 Geological Engineering Student Association Department of Geological Engineering Faculty of Engineering Gadjah Mada University

2 General Lecture: Prof. Joseph J. Lambiase, Department of Petroleum Geoscience UBD Abstract Many of the reservoir sandstones of SE Asia were deposited in the low energy shallow marine environments that develop in semi-enclosed seas with small ranges. Generally, these environments are described as "micro" and are expected to follow standard models for micro coastlines with respect to sand body geometry, facies distribution and sedimentary structures. However, ongoing research indicates that the Miocene outcrops and modern low energy systems of northern Borneo exhibit a significant departure from the established sedimentologic and stratigraphic models with respect to facies distribution, sand body geometry, stratigraphic succession, sedimentary structures and permeability distribution on both deltaic and nondeltaic coastlines. Furthermore, the modern systems demonstrate that subtle variations in the relative influence of the wave and regimes (plus the fluvial regime on deltaic coasts) generate strikingly different sets of coastline morphologies and facies distributions. These various morphologies and facies distributions are capable of depositing the range of stratigraphic successions seen in outcrop, although none of them duplicate the standard micro coastline model. The variety and complexity of the modern systems and low energy outcrop successions, many of which are direct analogues for producing reservoirs, indicates that the standard sedimentologic and stratigraphic models are far too simplistic to accurately predict subsurface reservoir properties in most cases. (For example, in some very low energy environments it is even difficult to distinguish wave-dominated facies from tide-dominated facies based on a standard interpretation of sedimentary structures.) Indeed, preliminary analysis of a producing field with connectivity problems suggests that most of the problems result from inaccurate predictions of sand body geometry because the predictions were based on a standard facies model. The need for new models is readily apparent; consequently, the outcrop and modern examples are being studied to derive a set of sedimentologic and stratigraphic models designed to distinguish among the various types of low energy depositional system based on the facies succession, sedimentary structures and faunal assemblages that can be interpreted from standard borehole data. The anticipated result is a significant improvement in the prediction of sand body geometry, connectivity and heterogeneity. 2

3 Low Energy Depositional Systems of SE Asia: Implications for Reservoir Characterisation Sari Di wilayah Asia Tenggara tubuh batupasir sebagai cebakan minyakbumi umumnya diendapkan pada lingkungan laut dangkal berenergi rendah yang berkembang di laut semi-tertutup dengan pasang-surut yang kecil. Umumnya lingkungan seperti itu disebut sebagai mikro, dan diharapkan mengikuti model standar untuk lingkungan pesisir mikro dalam kaitannya dengan geometri batupasir, distribusi fasies dan struktur sedimennya. Namun riset yang tengah berlangsung mengindikasikan bahwa singkapan-singkapan berumur Miosen dan sistem-sistem pengendapan modern yang berenergi rendah pada bagian utara Pulau Kalimantan menunjukkan penyimpangan terhadap model sedimentologis dan stratigrafis berkaitan dengan distribusi fasies, geometri tubuh batupasir, suksesi stratigrafis, struktur sedimen dan distribusi permeabilitas. Penyimpangan-penyimpangan tersebut terjadi baik pada lingkungan pesisir delta maupun non-delta. Lebih jauh, sistem-sistem modern tersebut menunjukkan variasi-variasi dalam pengaruh relatif dari rejim gelombang dan pasang-surut (plus rejim sungai pada lingkungan pesisir delta) menghasilkan kombinasi morfologi dan distribusi fasies yang berbeda-beda. Kombinasi-kombinasi tersebut mampu mengakomodasi berbagai suksesi stratigrafis yang terlihat di singkapan, meskipun tidak satu pun dari mereka yang persis sama dengan model lingkungan pesisir mikro standar. Dalam banyak contoh, variasi dan kompleksitas sistem-sistem modern dan suksesi singkapan berenergi rendah, banyak diantaranya merupakan pembanding (analog) langsung untuk menentukan cebakan minyakbumi, mengindikasikan bahwa model-model sedimentologis dan stratigrafis standar terlalu disederhanakan untuk bisa secara tepat memprediksi sifat-sifat cebakan bawah permukaan. [Sebagai contoh, dalam beberapa lingkungan berenergi rendah adalah sangat sulit untuk memisahkan fasies dominasi gelombang dari fasies dominasi pasang-surut hanya berdasarkan interpretasi standar struktur sedimen]. Analisa dari lapangan minyakbumi dengan permasalahan hubungan antar cebakan (konektivitas) menunjukkan bahwa permasalahan tersebut sebagian besar berasal dari prediksi geometri tubuh batupasir yang tidak tepat karena menggunakan model fasies standar. Kebutuhan akan model baru pun muncul; singkapan-singkapan dan contoh-contoh modern dipelajari untuk menghasilkan model-model sedimentologis dan stratigrafis yang dirancang untuk membedakan antara jenis-jenis sistem pengendapan berenergi rendah berdasarkan suksesi fasies, struktur sedimen dan asosiasi fauna yang dapat digunakan untuk interpretasi data core. Diharapkan akan terjadi peningkatan yang nyata dalam prediksi geometri tubuh batupasir, hubungan antar cebakan dan kemajemukannya. 3

4 General Lecture: Prof. Joseph J. Lambiase, Department of Petroleum Geoscience UBD Contents Abstract.. Sari (Indonesia).. Contents A. Introduction 1. Micro Coastline Models. 2. Are These Models Appropriate? 6 6 B. Non-Deltaic Depositional Systems 3. Cases from North Borneo.. 4. Hydrodynamic Environment of N Borneo. 5. Wave Dominant, Non-Deltaic Depositional Setting of NW Borneo.. a. Outcrop analogs. b. Wave-dominated, straight coastline. c. Modern beaches d. Grab sample profiles. e. The modern Brunei coast.. f. Biostratigraphic and sequence stratigraphic implications g. Comparative stratigraphy.. h. Resume for NW Borneo depositional setting. 6. Wave Dominant, Non-Deltaic Depositional Setting of N Borneo.. a. Outcrop analogs of Sandakan Fm.. b. Sandakan Fm. Stratigraphy. c. Barrier island of Dent Peninsula.. d. Micro coastline models.. e. Resume of N Borneo depositional setting. 7. Comparative Features of NW and N Borneo Depositional Settings to the Models. 8. Resume for Non-Deltaic Coastlines C. Deltaic Depositional Systems 9. Deltaic Depositional Setting of NW Borneo 10. Drainage Basins. 11. Hydrodynamic Environment. 12. Shoreline Morphology 13. Baram Delta. a. Sand body geometry. b. Mouth bar morphology c. Mouth bar cross-section. d. Facies and stratigraphy e. Hydrodynamics.. f. Tidal Prism. g. Power distribution h. Stratigraphy. i. Baram Field Stratigraphy 14. Trusan Delta. a. Morphology b. Facies and stratigraphy.. c. Hydrodynamics.. d. Power distribution 15. Resume for Baram and Trusan Deltas 16. Mahakam Delta. a. Sediment Distribution

5 Low Energy Depositional Systems of SE Asia: Implications for Reservoir Characterisation 17. Channel Evolution.. 24 D. Conclusions 18. Micro Stratigraphic Models. 19. Micro Sand Body Geometry Reservoir Properties Conclusions Acknowledgements.. About the Instructor

6 General Lecture: Prof. Joseph J. Lambiase, Department of Petroleum Geoscience UBD 1. Micro Coastline Models barrier island flats lagoon spit micro marsh delta delta washover fan fluvial sand barrier island muddy sediment littoral sand (after Blatt et al. 1980) micro to meso (after Reinson 1992) 2. Are These Models Appropriate? The models assume.. An oceanic wave regime A mid-latitude, temperate climate SE Asia has.. A much lower energy wave regime in semi-enclosed seas A tropical to equatorial climate 3. Cases from North Borneo 6

7 Low Energy Depositional Systems of SE Asia: Implications for Reservoir Characterisation 4. Hydrodynamic Environment of N Borneo Tidal Range Wave Height NW Borneo 1.7 m 0.7 m Brunei Bay 1.7 m 0.4 m N Borneo 1.8 m ~1.2 m 5. Wave dominant, non-deltaic depositional setting of NW Borneo a. Outcrop analogs 7

8 General Lecture: Prof. Joseph J. Lambiase, Department of Petroleum Geoscience UBD b. Wave-dominated, straight coastline c. Modern beaches 8

9 Low Energy Depositional Systems of SE Asia: Implications for Reservoir Characterisation d. Grab Sample Profiles e. The modern Brunei coast 9

10 General Lecture: Prof. Joseph J. Lambiase, Department of Petroleum Geoscience UBD f. Biostratigraphic and Sequence Stratigraphic Implications Relic benthonic fauna in water depths greater than ~ 10 m Mixing of modern and relic fauna on a time scale of as little as 1 2 thousand years Shelf assemblage defined from mixed assemblage Inability to distinguish minor and major water depth changes g. Comparative Stratigraphy NW Borneo Micro Model trough cross-bedding wave ripples HCS/SCS parallel lamination h. Resume of NW Borneo depositional setting Micro with very low wave energy Fine-grained sand Little trough cross-bedding Attached beaches No barriers, lagoons or deltas NW Borneo is significantly different from most micro models with respect to coastal morphology, sand body geometry, sedimentary structures, grain size and stratigraphic succession 10

11 Low Energy Depositional Systems of SE Asia: Implications for Reservoir Characterisation 6. Wave Dominant, Non-Deltaic Depositional Setting of N Borneo a. Outcrop analogs of Sandakan Fm. 11

12 General Lecture: Prof. Joseph J. Lambiase, Department of Petroleum Geoscience UBD b. Sandakan Fm. Stratigraphy meters upper shoreface sandstone lower shoreface sandstone storm sand /mangrove mudstone marine mudstone trough cross-bedding wave ripples hummocky cross-stratification parallel lamination 10 0 (after Suraya Tulot 2002) c. Barrier island of Dent Peninsula 12

13 Low Energy Depositional Systems of SE Asia: Implications for Reservoir Characterisation d. Micro coastline models barrier island flats lagoon spit micro marsh delta delta washover fan fluvial sand barrier island muddy sediment littoral sand (after Blatt et al. 1980) micro to meso (after Reinson 1992) e. Resume of N Borneo depositional setting Micro with higher wave energy than NW Borneo Medium to coarse-grained sand Trough cross-beds are moderately common Narrow barrier islands with large spits and no dunes Lagoons are filled by mangrove swamps Inlets are drowned river mouths without deltas North Borneo is generally similar to most micro models with respect to grain size and stratigraphic succession, but some aspects of coastal morphology, sand body geometry and sedimentary structures are distinctly different 7. Comparative Features of NW and N Borneo Depositional Settings to the Models NW Borneo North Borneo Micro Models Wave Energy Lowest higher highest Sand Size Finest coarser coarsest Trough Cross- Rare moderate Common Bedding Morphology attached beaches narrow barriers with long spits wider barriers, smaller spits Tidal Inlets no drowned river mouths wave and tide generated Tidal Deltas no no yes 13

14 General Lecture: Prof. Joseph J. Lambiase, Department of Petroleum Geoscience UBD 8. Resume for Non-Deltaic Coastlines Variations in wave energy are as important as range in determining coastline morphology Mangrove growth reduces the prism, which significantly decreases energy Marine processes are incapable of filling in drowned river mouths or forming large deltas 9. Deltaic Depositional Setting of NW Borneo 10. Drainage Basins 14

15 Low Energy Depositional Systems of SE Asia: Implications for Reservoir Characterisation 11. Hydrodynamic Environment Baram Trusan Tidal Range (m) Wave Height (m) Fluvial Discharge (m 3 /sec) Grain Size Fine sand Fine sand 12. Shoreline Morphology 13. Baram Delta 15

16 General Lecture: Prof. Joseph J. Lambiase, Department of Petroleum Geoscience UBD a. Sand body geometry b. Mouth bar morphology Ebb Tidal Delta (Hayes and Kana 1976) Suspended Load Channel (Orton and Reading 1993) 16

17 Low Energy Depositional Systems of SE Asia: Implications for Reservoir Characterisation c. Mouth bar cross-section NW Baram Delta SE flocculated mud? 1 km 1 m (after Cheong 2000) Fine-Grained Suspended Load Channel salt wedge muddy river plume mouth bar (after Orton and Reading 1993) d. Facies and stratigraphy (after Abdul Aziz 2000) meters 15 N km 0 5 mud mixed sand and mud sand current ripples large cross-bedding wave ripples flaser bedding HCS/SCS burrows lateral accretion low angle cross-beds parallel lamination wave tide 17

18 General Lecture: Prof. Joseph J. Lambiase, Department of Petroleum Geoscience UBD e. Hydrodynamics fluvial range 4 (m) 6 mixed tide 2 wave morphology facies tide wave wave height (m) f. Tidal Prism Tidal Prism the volume of water exchanged during a cycle; it can be expressed as the rate of exchange or Tidal Discharge; from E = ½ mv2, Tidal Energy Tidal Discharge g. Power distribution Pcurrent = E/t = (½ mv2)/t = ½ ρ(q/g)u2 Pwave = ECg = (ρgh2/8)(gt/4π) P - power E energy t - time ρ - fluid density q fluid discharge g gravity U flow velocity Cg wave celerity H wave height T wave period 18

19 Low Energy Depositional Systems of SE Asia: Implications for Reservoir Characterisation h. Stratigraphy /river bottom mud mixed sand/mud flats sand flats channel/bar sands upper shoreface sands lower shoreface sand/mud delta front mud current ripples large cross-bedding wave ripples flaser bedding HCS/SCS carbonaceous lateral accretion parallel lamination 4 metres

20 General Lecture: Prof. Joseph J. Lambiase, Department of Petroleum Geoscience UBD i. Baram Field Stratigraphy 30 shoreface 20 metres shoreface one cycle 10 0 shoreface Sandstone Mudstone HCS/SCS Ophiomorphia Planolites (after Tan et al. 1999) 14. Trusan Delta 20

21 Low Energy Depositional Systems of SE Asia: Implications for Reservoir Characterisation a. Morphology b. Facies and stratigraphy 21

22 General Lecture: Prof. Joseph J. Lambiase, Department of Petroleum Geoscience UBD c. Hydrodynamics fluvial range (m) 4 6 tide mixed 2 wave morphology facies tide wave wave height (m) d. Power distribution 22

23 Low Energy Depositional Systems of SE Asia: Implications for Reservoir Characterisation 15. Resume for Baram and Trusan Deltas Facies distribution and delta morphology respond differently to the modern hydrodynamic environment Sand body geometry is not easily predicted from facies succession 16. Mahakam Delta a. Sediment Distribution 23

24 General Lecture: Prof. Joseph J. Lambiase, Department of Petroleum Geoscience UBD 17. Channel Evolution distributary mangrove growth suspended mud erosion 18. Micro Stratigraphic Models increasing relative wave energy Trusan Baram NW Borneo N Borneo mean high tide mangrove swamp sand flat lower shoreface mud flat channel/bar storm sand mixed flat upper shoreface marine mud 24

25 Low Energy Depositional Systems of SE Asia: Implications for Reservoir Characterisation 19. Micro Sand Body Geometry Trusan Baram NW Borneo N Borneo 5 km 5 km 5 km 5 km increasing relative wave energy 20. Reservoir Properties Trusan Baram NW Borneo N Borneo Large, continuous sand bodies Fine-grained flat and channel sand Permeability barriers common Discontinuous sand bodies Fine-grained and shoreface sand Permeability barriers common Narrow, coastparallel sands, very continuous Fine-grained shoreface sand Local permeability barriers Long, wide coastparallel sands broken by inlets Medium coarse shoreface sand Few permeability barriers Heterogeneous reservoirs Heterogeneous reservoirs Homogeneous reservoirs Homogeneous reservoirs increasing relative wave energy 21. Conclusions Depositional systems on low energy, micro coastlines are much more complex than indicated by standard models. Different wave regimes produce major variations in coastal morphology, sand body geometry, stratigraphic succession, facies distribution, sedimentary structures and reservoir properties. Stratigraphic models suggest a link between facies succession, sand body geometry and reservoir properties that may allow accurate prediction in the subsurface. 25

26 General Lecture: Prof. Joseph J. Lambiase, Department of Petroleum Geoscience UBD Acknowledgements Abdul Razak Damit, Abdul Aziz Abdul Rahim, Cheong Yaw Peng, Suraya Tulot, Salahuddin Husein, George Pemberton and Mike Simmons for their contributions to the research. Brunei Shell Petroleum, Total Offshore Borneo, ExxonMobil Malaysia, Total Indonesia and Universiti Brunei Darussalam for financial support. About the Instructor Prof. Dr. Joseph J. Lambiase graduated from Brown University and received his Ph.D. in clastic sedimentology from McMaster University. After 3 years on the staff of Virginia Polytechnic Institute and State University he spent 13 years as an exploration geologist with Marathon Oil Company and Amerada Hess Limited. Since 1993, he has held the Brunei Shell Professorship, and the post of Head, in the Department of Petroleum Geoscience at Universiti Brunei Darussalam. He has authored numerous papers on shallow marine depositional systems and on stratigraphic development in rift basins. 26