SEAPEX Exploration Conference Fairmont Hotel, Singapore

2nd – 5th April 2019

ORAL PRESENTATION

Day 3: 5th April 2019

Session 11: Vietnam and Gulf of Thailand

Chairs: Paolo Tognini – Mubadala Petroleum, David Goulding – Sharp Reflections

13:30 Sand Body Characterisation in Tidal Marine Settings: Examples from the Malay Basin

Melissa Johansson Geode-Energy

13:55 Cambodia's Hydrocarbon Prospectivity - An Insight from Block A

Katherine Kho KrisEnergy

14:20

A Revised Chronostratigraphy for the Cuu Long Basin, Based on the Interpretation of Climate-driven Depositional Cycles during the Late Eocene/Oligocene, and VIM Depositional Cycles during the Mio-Pliocene

Bob Morley Palynova

14:45 Hydrocarbon Potential Offshore Vietnam, Opportunity and Challenges

Nguyen Anh Duc Petrovietnam

SEAPEX Exploration Conference Fairmont Hotel, Singapore

2nd – 5th April 2019

ORAL PRESENTATION

Sand Body Characterisation in Tidal Marine Settings: Examples from the Malay

Basin

Melissa Johansson1

1Geode-Energy, UK

mjohansson@geode-energy.com

The Malay Basin is located offshore Peninsular Malaysia. During the early Oligocene, the sediments were interpreted to be

non-marine, with marine incursions occurring during the early post-rift stage of the Late Oligocene. Three major lithological

groups are identified: sandstone, heterolithic and mudstone, with each facies often transitional into the next. The overall

depositional environment has been interpreted as restricted shallow marginal marine bay, adjacent or proximal to, a low energy

delta or estuarine mouth.

The heterolithics are some of the most common sediments observed in the Malay Basin, characterized by a number of diverse

facies ranging from silty cross-bedded sandstone, clay-laminated sandstone or siltstone, argillaceous bioturbated sandstone

or siltstone and flaser bedded sandstone. The silty cross-bedded facies appear to occur above the clean cross-bedded

sandstones and mark the initiation of channel abandonment.

The clay laminated sandstones show rhythmic interbedding, with minor Paleophycus burrows and occasionally exhibit

synaeresis cracks. This facies is observed located between cross-bedded sandstones. The argillaceous bioturbated

sandstones are associated with a sharp base and poorly defined upper contact, with rootlets, and the flaser-laminated

sandstones are defined by laminae couplets, iron-staining sandstone, Glaugonite and restricted ichnofauna.

The Mudstone lithologies are also characterized by a number of facies ranging from mudstone with rootlets, silty-mudstone,

silty bioturbated mudstone and sandy laminated mudstone. The mudstones are obviously defined by their large proportion of

clay, however they exhibit a variety of intricate structures. Features including small pisoids, rare sketal fragments, pyritic

nodules, burrow structures such as Planolites, Chondrites, Helminthopsis, J-shaped Arenicolites-type burrows (not necessarily

in the same interval) are observed.

The Malay Basin depositional environment, based on the facies observed, is interpreted to be a shallow marine coastal setting,

which comprises various sub environments ranging from estuaries, distributary channels, tidal channels, sand bars and

beaches, which form 5th order parasequences (Fig 1). A characteristic cycle comprises restricted bay mudstones at the base,

grading up into cyclic bay shales, transitional to firm-ground-capped tidal shoal silts, overlain by prograding tidal flat/bay margin

interlaminated facies followed by higher energy tidally influenced channel and mouth bar sands, the latter becoming rooted at

the top.

.

Figure 1. Different types of sand bodies observed in the Malay Basin

RESERVOIR CHARACTERISTICS

• Classic reservoir facies identified are laminated, cross-bedded and rippled sandstone. Marginal reservoir facies

include clay laminated sandstone and sandy bioturbated shales.

• Bioturbated facies can have higher than expected permeabilities. These include bioturbated sandstone and sandy

bioturbated shales. This enhanced permeability could be due to a complex interlaced network of more porous

material relative to the host sediment, providing a possible preferred flow pathway.

• Major inhibitors to permeability in the sandstones are the rootleted horizons which appear to be associated with

siderite or calcite. The siderite is indicated by the excess iron observed from the elemental spectroscopy.

• Large bodies of sandstone can be compartmentalized by iron rich sideritic or calcitic permeability barriers. This has

implications for reservoir management and future exploitation of the Malay Basin.

• The reservoir potential of heteroliths are very hard to calculate. The thin nature of the beds prevents accurate

porosity and permeability calculations from conventional logs. High resolution, advanced technology and

interpretation are needed to capture the impact of this play.

SPEAKER BIOGRAPHY

Dr. Melissa Johansson obtained her Ph.D on Deep Marine Sediments under the supervision of Prof Dorrik Stow. She worked

as a lecturer at UNIMAS Sarawak before joining Schlumberger, where she worked for 18 years all over the globe, with 8 of

them in Malaysia. She is now CEO of Geode-Energy Ltd specialized in reservoir characterisation especially borehole images.

SEAPEX Exploration Conference Fairmont Hotel, Singapore

2nd – 5th April 2019

ORAL PRESENTATION

Cambodia's Hydrocarbon Prospectivity - An Insight from Block A

Katherine Y.J. Kho1, Dr John M. Jacques1,2

1KrisEnergy Ltd

2JMJ Petroleum Pte Ltd

katherine.kho@krisenergy.com

The Gulf of Thailand remains one of the most attractive areas for hydrocarbon exploration and production in Southeast Asia,

and constitutes the southern offshore extension of a N-S trending Cenozoic intracontinental rift system that extends over 800

km. The eastern part of this offshore rift system is dominated by ?Eocene–Oligocene syn-rift basins (2–5 km) that underwent

rapid Miocene–Recent post-rift subsidence (4–8 km). Although unsubstantiated by significant well data, it is generally

regarded that the syn-rift half-grabens that characterise these basins are largely filled with continental sediments, including

important lacustrine deposits for hydrocarbon generation, particularly, oil. Coeval with the initiation of post-rift subsidence

(latest Oligocene–earliest Miocene), these oil-prone lacustrine sediments were covered by coal-rich, fluvial-deltaic to paralic

clastic sediments derived axially from the north (Western Highlands), east and west (e.g., Peninsular Thailand), and local

intrarift highs, supported by apatite fission track data and provenance studies. This largely fluvial-dominated setting has

provided the principal hydrocarbon-bearing reservoirs we see today, with intra-formational fluvial shales from paleosols

forming the main top seals, and fault sealing accomplished by sand-shale juxtaposition and gouge smear.

One of these intracontinental eastern Gulf of Thailand basins, the Khmer Trough, is the subject of this paper; with Block A,

operated by KrisEnergy, providing an invaluable insight into the untapped hydrocarbon potential of offshore Cambodia. The

Block itself is close to several large producing oil and gas fields in the Central and Northern Pattani basins and contains the

Apsara oil field - Cambodia’s only confirmed discovery.

Recent technical work completed by KrisEnergy, and by previous operators, demonstrates the significant exploration and

producing potential of Block A, and the Khmer Trough as a whole. Prospective trends in Block A have been identified with 3D

seismic interpretation and exploratory drilling. These plays are situated within 3-way dip structural closures of north-south

trending fault blocks, with multiple stacked reservoirs throughout the Oligo-Miocene section. There is also substantial potential

for other fault bounded complexes and stratigraphic traps.

This paper has been designed to: (1) provide an overview of the geotectonic setting and history of the Khmer Trough; (2) the

basin's essential play elements, including analogies from nearby genetically-related basins; (3) emphasise some of the key

exploration highlights of Block A with regards to its hydrocarbon prospectivity; and (4) present some of the key technical work

undertaken by KrisEnergy for the first phase of Apsara oil development in Cambodia Block A.

SPEAKER BIOGRAPHY

Katherine Kho received her BEng in Materials Science Engineering from the Nanyang Technological University of Singapore

in 2009, and a MSc in Petroleum Geophysics from Imperial College, London in 2010.

Since graduating from Imperial, Katherine initially worked in global seismic processing and interpretation in London with

Petroleum Geo-Services (PGS) from 2009-2011 and Schlumberger from 2011-2014. Since 2014 Katherine has been working

as a geophysical interpreter for KrisEnergy Ltd., based in Singapore, largely working on a variety of projects within the Gulf of

Thailand and the Bay of Bengal. Katherine was a recipient of the Karen Reed Memorial Award, a PESGB scholarship and

the BP Book Prize in 2010, and is a member of the AAPG and PESGB; she is also a serving councillor for the Southeast Asian

Petroleum Exploration Society (SEAPEX).

SEAPEX Exploration Conference Fairmont Hotel, Singapore

2nd – 5th April 2019

ORAL PRESENTATION

A Revised Chronostratigraphy for the Cuu Long Basin, Based on the

Interpretation of Climate-Driven Depositional Cycles During the Late

Eocene/Oligocene and VIM Depositional Cycles During the Mio-Pliocene

Robert J. Morley1, Nguyen Tung 2, Bui Viet Dung2, A.J. Kullman3, Robert T. Bird3

1Palynova UK

2Vietnam Petroleum Institute, Vietnam

3Murphy Oil, Vietnam

bobmorley100@gmail.com

INTRODUCTION

The chronostratigraphy of the Cuu Long Basin, which lies offshore Vietnam to the south of the Mekong Delta on the Sunda

Shelf, is poorly understood, both within the Palaeogene rifted succession and during the Mio-Pliocene.

This paper utilises a comprehensive biostratigraphic database from 46 exploration wells (Fig 1) to establish a high-resolution

sequence biostratigraphic framework for the Late Eocene and Oligocene Ca Coi, Tra Cu, Tra Tan and Bach Ho Formations

and identifies high frequency transgressive-regressive depositional cycles throughout this succession. The Miocene and

Pliocene, on the other hand, is interpreted by reference to VIM depositional cycles (Morley et al. 2011) which allow the extent

of Neogene unconformities to be determined.

Fig 1. Cuu Long Basin and positions of well locations and seismic lines used for this study

LATE EOCENE AND OLIGOCENE STRATIGRAPHY

The Late Eocene and Oligocene Formations have been systematically evaluated for palynology over many years by Vietnam

Petroleum Institute (VPI) biostratigraphers. Detailed analysis of the data shows that the entire succession consists of repeated

transgressive-regressive packages of alternating lacustrine and fluvial deposits (Fig 2). These are particularly well defined

within the Tra Nan and Bach Ho Formations. Altogether 36 such depositional packages have been differentiated, 30 of which

fall between two easily identified palynological datums. The oldest is the stratigraphic base of Magnastriatites howardi at

about 36 Ma during the late Eocene, whereas the second datum is the base of Florschuetzia levipoli, marking the base of

palynological zone PR9 of Yakzan et al (1996), close to top Oligocene (Morley et al. 2015). The cycles are clearly climate-

driven, each beginning at a time of drier climate and with a wetter climate at the time of the maximum development of lacustrine

conditions. It is suggested that these depositional cycles are driven by 406 ka eccentricity cycles, shown by Paalike et al.

(2006) to form the ‘heartbeat of the Oligocene’ climate (Fig 3).

Fig 2. Well A, showing lacustrine depositional cycles revealed from evaluation of abundance maxima of freshwater algae.

The nature of the algal maxima become clear only when presented using a variety of pollen sums.

All the cycles are present in the basin depocentre, but their representation at the basin periphery is more limited. The

differential representation of the cycles from basin margin to basin depocentre identifies three distinct unconformities, which

tie to three regional seismic picks (picks ‘C’, ‘D’ and ‘E’; Fig 3).

By integrating sequence biostratigraphic and seismic datasets, the Oligocene is shown to be characterised by two types of

depositional sequence: short-lived packages, termed parasequences, that are essentially driven by fluctuating climate (and

hence sea level change) and longer term packages, each comprising a succession of parasequences separated by

unconformities, which tie to the main seismic divisions within the Oligocene and are entirely driven by tectonics. The latter

are best visualised as 3rd order sequences, with the parasequences forming 4th order sequences.

The position of top Oligocene is placed within the Upper Bach Ho Formation, instead of at top Tra Nan Formation as suggested

previously. There are actually very few age-restricted markers through most of the Bach Ho Formation, but the presence of

good ‘bases’ for Florschuetzia levipoli (22.5 Ma) and F. semilobata, in the Upper Bach Ho Formation together with the highest

occurrence of Cicatricosisporites dorogensis suggests that the top Oligocene is likely to occur within that formation.

Eccentricity-driven 406 ka depositional cycles are likely to be widespread in East and Southeast Asian basins, driving

deposition throughout the Palaeogene in the Bohai Basin (Liu et al. 2018) and in the West Natuna Basin (Morley et al. 2007,

2012).

Fig 3. Representation of VIM depositional cycles in Neogene and 406 ka eccentricity-driven depositional cycles in Palaeogene

MIOCENE AND PLIOCENE STRATIGRAPHY

The Mio-Pliocene stratigraphy has been evaluated from just a few wells, for which detailed foraminiferal, nannofossil and

palynological analyses are available.

The Neogene has some age-restricted index fossils and is tentatively interpreted by reference to VIM depositional cycles

(Morley et al. 2011), which suggest close parallels with the Mio-Pliocene stratigraphy of adjacent basins.

The basal early Miocene Upper Bach Ho Formation includes a short interval with common Ammonia spp. (benthonic

foraminifera), termed the ‘Rotalia Shale’. It correlates with palynological zone PR8 or the base of PR9A and thus occurs close

to the base of the Miocene. It is thought to tie to VIM32, and forms a near-base Miocene transgression.

The immediately overlying Con Son Formation shows a regressive lower part, which had similarities with Cycles VIM 34 to

46, whereas the upper part has a more transgressive character, and can be divided into four depositional packages (Fig 3).

The second of these includes the highest consistent occurrence of Florschuetzia semilobata, a datum that occurs within Cycle

VIM 53, and an abundance acme of the nannofossil Sphenolithus heteromorphus in the flooding surface of the third of these

suggests Cycle VIM54. An acme of Miogypsina spp. in the topmost cycle would be consistent with VIM56. The basal cycle

has no diagnostic events but would be consistent with Cycle VIM52.

There is a significant middle Miocene unconformity, with Cycles VIM 58 to 63 missing (the middle Miocene Unconformity,

MMU), above which the late Miocene Dong Nai Formation is represented by Cycles VIM 64, VIM66 and VIM76, separated by

a further unconformity. VIM64 contains the NN9 nannofossil marker Discoaster hamatus, and VIM66 the NN10 marker D.

bollii, whereas VIM76 contains common Discoaster quinqueramus and long-armed D. berggrenii.

The lower part of the Bien Dong Formation is of Early Pliocene age, and can be referred to nannofossil zones NN14 or NN13.

REFERENCES

Liu, Z., Huang, C., Algeo, T.J., Liu, H., Hao, Y., Du, X., Lu, Y., Chen, P., Guo, L. & Peng. Li., 2018. High-resolution

astrochronological record for the Paleocene-Oligocene (66–23 Ma) from the rapidly subsiding Bohai Bay Basin, northeastern

China. Palaeogeography, Palaeoclimatology, Palaeoecology 510: 78–92.

Morley, R. J. 2012. A review of the Cenozoic palaeoclimate history of Southeast Asia. Pp. 79-114 in Gower, D. J., Johnson,

K. G., Richardson, J. E., Rosen, B. R., Ruber, L. & Williams, S. T. (eds.). Biotic evolution and Environmental change in SE

Asia, Systematics Association Cambridge University Press, Cambridge.

Morley, R. J, Salvador, P., Challis, M. L., Morris, W. R. & Adyaksawan, I, R. 2007. Sequence biostratigraphic evaluation of the

North Belut Field, West Natuna Basin. Proceedings of the Indonesian Petroleum Association 31st annual convention, IPA07-

G-120.

Morley, R. J., Swiecicki, T., and Dung Thuy Thi Pham 2011. A sequence stratigraphic framework for the Sunda Region, based

on integration of biostratigraphic, lithological and seismic data from Nam Con Son Basin, Vietnam Proceedings, Indonesian

Petroleum Association Thirty-Fifth Annual Convention & Exhibition, May 2011.

Morley R.J., Swiecicki, T., Pedro Restrepo Pace 2014. Correlation across the South China Sea using VIM transgressive-

regressive cycles. In: Tectonic evolution and sedimentation of South China Sea region, AAPG Geosciences Technology

workshop, Kota Kinabalu 2015, pp. 42-46.

Paalike, H., Norris, R. D., Herrle, J. O. et al. 2006. The heartbeat of the Oligocene climate system. Science, 314, 1894–8.

Yakzan, A.M., A. Harun, B. M. Nasib, and R.J. Morley, 1996, Integrated biostratigraphic zonation for the Malay Basin: Bulletin

of the Geological Society of Malaysia, 39, 157-184.

SPEAKER BIOGRAPHY

Bob Morley graduated from Hull University with a PhD in Quaternary palynology of the Sunda region a long time ago. After

spending 16 years with an international geological consultancy company and two years at the British Geological Survey he

established the consultancy ‘Palynova’, now in its 27th year, which specialises in high resolution sequence biostratigraphic

evaluations of Southeast Asian basins.

He has published over 120 papers on SE Asian geology and biogeography, and also a book ‘Origin and Evolution of Tropical

Rain Forests’ (John Wiley 2000). With a biostratigraphic database from over 300 wells from our region all uniformly interpreted

in terms of climate driven depositional cycles, he is currently looking at novel ways to examine the chronostratigraphy of the

area to clarify the duration and extent of regional unconformities, and also to use palynological records as a palaeolatitude

proxy to aid plate tectonic reconstructions.

SEAPEX Exploration Conference Fairmont Hotel, Singapore

2nd – 5th April 2019

ORAL PRESENTATION

Hydrocarbon Potential Offshore Vietnam, Opportunity and Challenges

Nguyen Anh Duc1

1Petrovietnam, Vietnam

ducna@pvn.vn

The presentation briefly reviews results of recent exploration activities and hydrocarbon potential of sedimentary basins

offshore Vietnam. The opportunities and challenges in hydrocarbon exploration in Vietnam are also introduced in the

presentation.

SPEAKER BIOGRAPHY

Dr. Nguyen Anh Duc has 15 years of experience working in Vietnam Petroleum Institute (VPI). Since 2011 he has held the

position of Manager of Reserves and Resources Management Department, Exploration Division, Vietnam Oil and Gas Group

(Petrovietnam).