ISSN-0866-854X
An Official Publication of The Vietnam National Oil and Gas Group Vol 6 - 2011
PETRO
VIETNAM
Petro
ietnam
Te Giac Trang field: Geological features,
reservoirs and field development concepts
Biofacies and sequence stratigraphy,
Oligocene to Pliocene, Cuu Long
and Nam Con Son Basins, Vietnam
PETRO
VIETNAM
Petro
ietnam
Editor-in-chief
Deputy Editor-in-chief
Editorial Board Members
Secretary
Contact Address
Designed by
Dr.Sc. Phung Dinh Thuc
Dr. Nguyen Van M inh
Dr. Phan Ngoc Trung
Dr. Vu Van Vien
Dr. Sc. Lam Quang Chien
Dr. Hoang Ngoc Dang
Dr. Nguyen Minh Da
BSc. Vu Khanh Dong
Dr. Nguyen Anh Duc
MSc. Tran Hung Hien

31
Advanced drilling in HPHT: The TOTAL experience on Elgin Franklin
(North Sea - UK)
24
80
79
Contents
Contents
PETROLEUM EXPLORATION & PRODUCTION
Te Giac Trang field: Geological features, reservoirs
and field development concepts
38
60
PETROLEUM PROCESSING
NEWS
PVFCCo launches a new fertilizer brand - Phu My NPK
74
Development of a Kinetic Model for the Aromatisation of Propane and
Propene over H-ZSM-5 Catalyst under Deactivating Conditions
The characteristics of Miocene sedimentary rocks in the
Western Cuu Long Basin
3
PETROVIETNAM - JOURNAL VOL 6/2011
PETROVIETNAM
1. Introduction
The Cuu Long Basin lies just o shore from the Eastern
Sea coast of Southern Vietnam. It is separated to the South
by a basement high, the Con Son Swell, from a larger re-
gion of several sub-basins comprising the Nam Con Son
Basin that straddles a large part of Vietnam’s territorial wa-

nd
order cycles. This scheme is in its infancy and is open to refinement as more wells are studied,
but is currently complete enough for application to any new well drilled in either basin. It has already led to some radi-
cally revised age assignments amongst legacy wells so far studied. In addition, there are some important differences
in sedimentary regime between the Cuu Long and Nam Con Son Basins, reflected in the palynofacies assemblages,
particularly within the Late Oligocene and Early Miocene.
Age constraining of sedimentary units is particularly important in petroleum exploration of the Vietnam offshore.
The section has a plethora of repetitive clastic lithologies. The characteristics of some of these intervals as potential
migration zones or stratigraphical traps (as detectable from fluid inclusion studies), need to be accurately delineated
within a workable regional sequence stratigraphical scheme.
4
PETROVIETNAM - JOURNAL VOL 6/2011
PETROLEUM EXPLORATION & PRODUCTION
monotonously alternating sandstones and mudstones
that are di cult to constrain and correlate lithostrati-
graphically and by wireline logs. Major limestone units are
present in the Nam Con Son Basin (Fig. 2).
Additional di culties arise from the presence of few
age restricted microfossils for strict biostratigraphical age
determination. Much of the interval of exploration interest
(Oligocene - Middle Miocene) is non-marine or marginal
marine, yielding only long ranging palynomorphs (Fig. 3),
though more open marine sections in the later Neogene
yield good micropalaeontological and calcareous nanno-
fossil age markers. Marine in uence commenced earlier
and is more strongly evident in the biofacies of the Nam
Con Son than the Cuu Long Basin.
Though most are long ranging, palyno-
morphs are present in large numbers within
most cuttings samples available from the Late

This paper investigates the opportunity of using
biofacies trends at a more re ned level in sequence
stratigraphical analysis. Identi cation of similar biofa-
cies trends across a number of intra-basin wells should
provide several additional correlation tie-points. If such
trends can be demonstrated to be sea-level controlled,
their value as time synchronous cross-facies stratal sur-
faces can be validated. In this way a number of supple-
mentary time-lines become available to add to the FAD’s
and LAD’s ( rst and last occurrence datums) from age
diagnostic biostratigraphical taxa alone. A sea-level driv-
Fig. 1. Cuu Long Basin - Con Son Swell - Nam Con Son Basin, Vietnam
5
PETROVIETNAM - JOURNAL VOL 6/2011
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en sequence stratigraphical model may also provide a
means of inter-basin correlation between the Cuu Long
and Nam Con Son Basins.
Morley (1991) used quantitative palynomorph zones
in improved stratigraphical resolution in the SE Asian Ter-
tiary and mentioned the elimination of non-stratigraphi-
cal quantitative events whose correlation lines cut across
good biostratigraphical correlation datums. A recommen-
dation of a 4 well minimum database for initiation of a
quantitative local scheme within a basin was mentioned
with a further 4 wells, a total of 8 therefore, suggested
as the requirement for full elaboration and assembly of
a scheme erected on a series of quantitative events for
basin-wide predictive purposes.
2. Megasequences

Pleistocene).
Each of the megasequences
V1 - V4 are marked at their base
inception by a major increase in
marine microfossils. The actual
biofacies boundary may then, be
better de ned using the scheme
of Galloway (1989) that places
Fig. 2. Sequence Stratigraphy Scheme, Cuu Long and Nam Con Son Basins
6
PETROVIETNAM - JOURNAL VOL 6/2011
PETROLEUM EXPLORATION & PRODUCTION
sequence boundaries at  ooding surfaces. This occurs
slightly younger in the section, with the exception of the
Miocene - Pliocene boundary (V3-V4) at 5.33 Ma that is al-
ready placed at a  ooding surface on the Geological Time
Scale of Gradstein et al. (2004).
Megasequence boundaries at the initial transgres-
sive surface of the next transgressive systems tract (TST)
or maximum  ooding surface at the base of the ensuing
high stand systems tract (HST), as used in this study are
as follows:
22.3 Ma - Late Oligocene, V0.
15.8 Ma - Early Miocene, V1.
8.0 Ma - Middle Miocene - early Late Miocene, V2.
5.33 Ma - Late Miocene, V3.
0.05 Ma - Plio-Pleistocene, V4.
Megasequence V2 is dated as Middle Miocene to early
Late Miocene (Langhian, Serravallian and Early Tortonian).
Age of the upper boundary of this megasequence is

marine ingress into the basin is near and strong enough.
Mangrove pollen with marine dinocysts and other marine
palynomorphs such as chitinous microforaminiferal lin-
ings may rapidly become an increasingly important com-
ponent of each successive parasequence up through the
sequence. In more high angle beach settings, pollen of
plants such as Casuarina, Marginipollis concinnus, Pandanii-
dites sp. and Echiperiporites estelae are particularly evident.
If the basin remains in an interior continental setting
or is distal with respect to the direction of marine ingress,
raised base level will be manifest by an increase in lacus-
trine algae and pteridophyte spores of associated water-
logged terrain, such as Magnastriatites howardi.
Fig. 3. Palynofloral Zones, Cuu Long and Nam Con Son Basins
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3.2. Highstand systems tract (HST)
Following the R-in ection point of maximum rate of
sea-level rise, with the maximum  ooding surface, sedi-
mentation may continue over an area of plentiful accom-
modation space, but it can become more regressive, pro-
gradational in aspect. Palyno oral assemblages will be
dominated by lowland freshwater pollen types and where
waterlogging persists in a non-marine setting, pterido-
phyte spores, including Magnastriatites howardi from the
aquatic fern Ceratopteris.
Restricted basins or those distal to the open marine
realm may register continued high freshwater base level
from the earlier TST phase, recording raised lacustrine al-

to non-sequences and higher
energy of  ow as the ‘nick’ point
erodes back over an increased al-
luvial gradient. If sea-level does not fall below the exist-
ing shelf sediments of the earlier highstand, then a shelf
margin wedge systems tract may be produced.
With either shelf margin wedge sedimentation or
shelf incision, coarser clastic lithologies tend to predomi-
nate with the higher energy run-o alluvial  ow rates.
The winnowing e ect of the current leads to dispersal
and destruction of organic material. Palynomorph as-
semblages tend to be quite poor, coinciding with coarser
clastic lithologies. Where palynomorphs are present they
are dominated by a lower diversity of taxa and a greater
concentration of montane gymnosperm pollen such as
Piceapollenites sp., Pinuspollenites sp. Alnipollenites sp. and
Zonalasporites sp.
Lowstand sedimentation coincides with glacial maxi-
ma, which in the tropics may lead to increased seasonality
Fig. 4. Microfacies Scheme, Cuu Long and Nam Con Son Basins
8
PETROVIETNAM - JOURNAL VOL 6/2011
PETROLEUM EXPLORATION & PRODUCTION
with a more marked dry season. Lowland everwet rainfor-
est pollen types may be reduced in favour of shrub  oras
dominated by fern spores and savanna grassland with
Monoporites annulatus.
4. Biofacies of megasequences
In this section broad trends of environmentally sig-
ni cant taxa from a number of wells are examined in

inertinitic kerogen derived from
coal seams indicative of freshwa-
ter swamp deposition.
4.1.1. Sequences
The V0 sequence in the Cuu
Long Basin reveals some marked
downhole changes in abundance
of the lacustrine algae Botryococ-
cus, Bosedinia and Pediastrum in
a few wells that have penetrated
a good interval of the Late Oligo-
cene. There are also changes in
the kerogen type. It is uncertain
that these changes can be related
to sea-level e ects within these
continental rift basins. Morley
(1991) has noted that mangrove
taxa of the Florschuetzia group
and the back mangrove taxon Dis-
coidites borneensis may have had
a freshwater swamp origin in the
Palaeogene.
Sequences V0a, V0b and V0c
have been tentatively recognised
Fig. 5. Palynofacies Defined Genetic Sequences, Cuu Long Basin, Vietnam
9
PETROVIETNAM - JOURNAL VOL 6/2011
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pending further studies, but they may be more related to
local changes in water conditions, though base level ef-

the-less these lacustrine
phases provide an im-
portant subsidiary source
rock facies, though to a
lesser degree than in the
syn-rift section.
Dua Formation as-
semblages from the Nam
Con Son Basin yield an
abundance of the lacus-
trine alga Pediastrum spp,
but not records of Botryo-
coccus spp, or Bosedinia
sp., indicative of smaller,
less permanent, ephem-
eral lakes that may have
been subject to minor
marine inundation. Pte-
ridophyte spores and
gymnosperm pollen are
comparatively common.
Marine palynomorphs
are present in increasing
numbers up through the
megasequence and the
microfaunal analysis re-
veals J. cf. macrescens plus
Elphidium cf. tikutoensis
and rare ostracods.
Fig. 6. Palynofacies Defined Genetic Sequences, Nam Con Son Basin, Vietnam

courses and more stable for
a greater diversity of pterido-
phytes and clearer develop-
ment of mangroves, but less
favourable for lowland forest
to become established.
4.2.2. Highstand Sequences
Highstand sequences
(V1a & V1d) are character-
ised in the Cuu Long Basin by
prominent lacustrine facies,
but on a slightly reduced
scale than seen in the TST,
similarly of the lake fringing
facies of Ceratopteris and its
spore M. howardi.
Assemblages of lowland
freshwater pollen and spores tend to be richer and more
diverse. These biofacies re ect the development of stable
plant communities and diverse habitats over extensive
tracts of prograding upper and lower coastal plain, during
this phase of diminishing rate of sea-level rise.
In the Nam Con Son Basin marine in uences are
overall greater and lacustrine palynofacies, with M. how-
ardi lesser than in the Cuu Long highstand sequences
V1a and V1d.
4.2.3. Lowstand Sequences
In the Cuu Long Basin lowstands V1b and V1e are
characterised by poor palynomorph recovery and diver-
sity as shelfal accommodation space was rapidly reduced.

the South where May & Eyles (1985) have documented
Middle Miocene reefal carbonates.
4.3.1. Lowstand Sequences
Some of the thickest limestone development in the
Nam Con Son Basin has been linked to lowstand sedimen-
tation (sequence V2b), though in some areas of the basin
clastics remained dominant.
In the Cuu Long Basin no carbonates are encoun-
tered as the basin remained landward of the shelf edge.
Sedimentation was characterised by valley incision and
high sedimentation rates of coarse clastics in depocen-
tres. Sequence V2b yields abundant gymnosperm pollen
indicative of greater upper coastal plain/montane in u-
ence in the depositional environment and it is poorly dis-
tinguishable from the ensuing TST. Sequence V2e is a
poor recovery interval in some areas of the Cuu Long
Basin, whilst sequence V2i is rarely observed, perhaps
re ecting a non-sequence during sediment by-pass at
this time in the basin.
4.3.2. Transgressive Sequences
Cuu Long Basin sediments of the V2c sequence
are characterised by common mangrove pollen and
M. howardi indicative of the creation of abundant sedi-
ment accommodation space with wide tracts of lower
coastal plain for these plants to  ourish.
Nam Con Son Basin V2c sediments display a
marked increase in marine palynomorphs but lime-
stones are not always evident probably due to ravine-
ment erosion and renewed extensive shelfal clastic
sedimentation leading to inundation of former reefs.

cated by an uphole increase in marine to ter-
restrial (M:T) palynomorph ratio, a much more
marked change than that seen in the Cuu Long
Basin. This boundary also coincides with the
 rst appearance of limestones in the Nam Con
Son Basin, lithologies completely absent in the
Cuu Long Basin. Shallow marine benthonic mi-
crofaunas (microfacies 3 - 4) indicative of an in-
ner to middle neritic palaeoenvironment occur
at the base V2 megasequence, where none are
seen in the Cuu Long Basin.
The V2d sequence (coeval with an acme of
M. howardi in Cuulong Basin) is marked by a fur-
ther uphole increase in marine palynomorphs
and mangrove taxa.
The V2h sequence is dated as middle Mio-
cene (intra NN6 nannofossil zone) throughout
the Nam Con Son Basin. Palynomorph analysis
reveals a further increase in marine taxa (M:T
ratio) within this sequence, with progressive
subsidence following the middle Miocene in-
version and unconformity. This unconformity
shows diachroneity of its base and top across
the Cuu Long Basin from the apparent absence
of some sequences in some wells, but it ap-
pears to be an intra NN6 event.
4.4. V3 Megasequence (Fig. 10)
This megasequence is marked by a further
uphole increase in marine taxa in the palyno-
morph assemblage.

5. Conclusions
An attempt has been made to identify corre-
latable sea-level controlled biofacies events for
improved stratigraphical resolution in the non-
marine and marginal marine sections (Oligocene
to mid-Miocene) of the Cuulong and Nam Con
Son basins. This has been achieved by recognis-
ing frequency trends of some environmentally
controlled, but long ranging palynomorphs and
microfaunal microfacies.
It has been possible to demonstrate di er-
ences between coeval sequences in the 2 basins.
Such provincialism is indicative of isolation and
separate autonomous basin  lling histories. The
independent e ects of marine transgression
and forced regression have been invoked. An
overall sea-level control may permit correlation
of sequences between these unconnected inte-
rior fracture continental rift basins.
These di erences diminish into the Middle
Miocene, as progressive marine transgression
led to more regionally synchronous sedimen-
tation. It was not until the Late Miocene that
planktonic and benthonic foraminifera plus cal-
careous nannofossils become abundant, indica-
tive of widespread marine transgression of the
regional thermal sag phase.
These studies have allowed the assembly
of initial stratigraphical templates that provide
improved stratigraphical resolution through the

15(4) 451 - 464.
2. Bat, D., Quynh, H., Que, P. H. & Dong, T. L., January
1993. Tertiary stratigraphy of continental shelf of Viet-
nam. In: Proceedings of the 1
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international seminar
on the stratigraphy of the Southern continental shelf
of Vietnam.
3. Cole, J. M. & Crittenden, S., 1997. Early Tertiary ba-
sin formation and the development of lacustrine and qua-
si-lacustrine/marine source rocks on the Sunda Shelf of SE
Asia. In: Fraser, A. J. & Matthews, S. J. & Murphy, R. W. (eds)
Petroleum Geology of Southeast Asia, Geological Society
Special Publication 126: 147 - 183.
4. Cole, J. M., Whittaker, M., Kirk, M. & Crittenden, S.,
2005. EA sequence-stratigraphical scheme for the Late Car-
boniferous, Southern North Sea, Anglo-Dutch sector. In: Col-
linson, J. D., Evans, D. J., Holliday, D.W. & Jones, N. S. (eds)
Carboniferous hydrocarbon Geology: The Southern North
Sea and surrounding onshore Areas, Yorkshire Geological
Society Occasional Publication 7: 75 - 104.
5. Courel, L; Rey, J; Cotillon, P; Dumay, J; Mauriaud, P;
Rabiller, P; Raynaud, J. F; & Rusciadelli, G., 2008. Lithostratig-
raphy from lithologic units to genetic stratigraphy. Stratigra-
phy terminology and practice, Chapter 2. Editions Technip,
Paris. 7 - 39.
6. Galloway, W. E., 1989. Genetic stratigraphic se-
quences in Basin analysis I: Architecture and genesis of  ood-
ing surface bounded depositional units. Bull. Amer. Assoc.
Petroleum Geol. 73(2): 125 - 142.

Ann. Conv. Indonesian
Petr. Assn. 255 - 276.
13. Morley, 1991. Tertiary stratigraphic palynology in
Southeast Asia: Current status and new directions. Geol. Soc.
Malaysia, Bull 28: 1 - 36.
14. Phan Trung Dien, Phung Sy Tai & Nguyen Van
Dung, 1997. Basin analysis and petroleum system of the
Cuu Long Basin on the continental shelf of Vietnam. Proc.
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15. Tapponier, P., Peltzer, G., Le Dain, A. Y., Armijo, R.
& Cobbold, P., 1982. Propogating extrusion tectonics in Asia:
New insights from simple experiments with plasticine. Geol-
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stress  eld in Northern Sunda Shelf basins. In: Geol. Soc.
Spec. Pub. 106: 291 - 306.
15
PETROVIETNAM - JOURNAL VOL 6/2011
PETROVIETNAM
Introduction
Facies and depositional environment determination
are fundamental work to be carried out when geoscien-
tists study any clastic reservoir for the purpose of hydro-
carbon exploration and development. Such work can be
relatively straightforward when outcrop data is available.
In the subsurface, however, it can be problematic when
only very limited core or sometimes even no core is avail-
able. The idea of using wireline logs as sedimentological

to help geoscientists to get a clear picture of what type of
sedimentological information is available on images and
how to use them in facies and environmental analysis, and
ultimately explain how geological uncertainty can be re-
duced with full integration of acquired image data with
conventional open-hole logs in clastic reservoirs.
Electrofacies and depositional environment
interpretation for a clastic reservoir utilizing
electrical image logs
Bingjian Li
Schlumberger Oil Field Services (Vietnam)
Facies are crucial inputs for depositional environment interpretation, reservoir property prediction and reser-
voir modeling. Traditionally, fancies description for classic reservoirs has relied heavily on core data. This is a time-
consuming data acquisition process with high well cost. This paper presents an alternative technique for electrofacies
characterization of classic sands utilizing electrical image logs, together with a case study. Electrofacies are deter-
mined with integration of sedimentary structure and texture information interpreted on image logs and lithology
from conventional open-hole logs. Analysis of facies association, sequence trend and paleocurrent directions pro-
vides satisfactory data to assist the depositional environment construction. This case study along with the devel-
oped work ow promotes more complete use of the acquired borehole images and conventional open-hole logs with
cost-e ective solutions for electrofacies and environmental determination. The presented data in the paper is from a
 uvio-estuarine sequence but the approach developed can be applied in any clastic reservoir in the local Miocene or
Oligocene formations in the subsurface of o shore Vietnam.
Abstract
16
PETROVIETNAM - JOURNAL VOL 6/2011
PETROLEUM EXPLORATION & PRODUCTION
Fig. 2. Sedimentary structures detected on FMI images. Plate A (up-
per) - Cross-bedding along with truncation surface and mud rip-up
clasts (red arrow indicated). Plate B (lower) - burrows appear as
white curved features on FMI

primary or syndepositional such as organic structures
formed in connection with an animal or plant organic ac-
tivity (borrow, root traces, etc) and inorganic structures
resulted in physical agents and postdepositional struc-
tures such as slumping, mud-cracks, dissolution and con-
cretions. Fig. 2 shows two examples of the sedimentary
structures; one includes both predepositional, small scale
erosional surfaces, as well as syndepositional inorganic
structure, cross-bedding, (plate A), and another one is the
syndepositional organic structure, burrows, (plate B).
One needs to bear in mind that some structures might
be ambiguous on electro-images; for example small
1 m
Cross-bed sets
Truncation surface
Truncation surfaceTruncation surface
Truncation surface
Mud rip
Mud ripMud rip
Mud rip-

-up
up up
up clasts
clastsclasts
clasts
Cross
CrossCross
Cross-


Rock texture using SandTex*
A relative sorting index can be estimated from the
resistivity spectral analysis (SandTex* software) using the
electrical borehole images - FMI/FMS or OBMI (Newberry
et al, 2004). All points crossing the wellbore on electro-
images are grouped into three divisions - the “matrix” frac-
tion which is the background of the rock texture, resistive
fraction which is the portions having resistivities greater
than matrix and conductive fraction which has resistivi-
ties less than the “matrix” fraction. SandTex* calculates the
actual resistivity represented by each of the fractions and
the percentages of the three fractions to derive a sorting
index. Fig. 3 gives an example showing the outputs from
SandTex*: track 1 is the fractional percentages, track 2
showing the peak resistivity as well as the upper and low-
er boundaries for a well sorted sand overlain on the vari-
able density log display and the computed sorting index
(white curve). Fig. 4 shows an example of an image de-
rived sorting index (black curve in track 2) having reason-
able agreement with the sorting index (red dot) gained
from core analysis.
Electrofacies analysis workflow
In this paper, an integrated work ow is used to de ne
the electrofacies (Fig. 5). First of all, lithologies are deter-
mined using the conventional open-hole logs mainly GR
data as described in the previous section above. Second-
ly, sedimentary structures are interpreted on FMI images.
Thirdly, a sorting index is derived on FMI images using the
SandTex* described above.
Then electrofacies is determined for any particular

Electrofacies
ElectrofaciesElectrofacies
Electrofacies Determination Flowchart
Determination FlowchartDetermination Flowchart
Determination Flowchart
X
XX
X-

-bedded SST
bedded SSTbedded SST
bedded SST
Laminated SH
Laminated SHLaminated SH
Laminated SH
Massive SILT
Massive SILTMassive SILT
Massive SILT
Open-hole Logs
(GR-Pe-RHOZ
-NPHI)
FMI
Lithology
Core
calibration
Electro
ElectroElectro
Electro-

-

the upper section of the Plate A in Fig. 6. Sorting is usu-
ally good for the massive sands. Cross-bedded sand-
stones (CBSt): It is one of the most common facies in the
studied well. It has low GR response as clean sands and
intensive cross-beds. Fig. 8 shows an example of four dif-
ferent sets of cross-beds separated by truncation surfaces.
Some mud rip-up clasts might be observable at the base
of a truncation surface (see 471.4m of Fig. 8). The cross-
bedded sands can be either well- or medium-sorted. Bed-
ded sandstones (BSt): It has either low or slightly higher
GR than clean sands. Horizontal or low angle bedding (or
lamination) can be observed on FMI images for bedded
sandstones. An example of bedded sandstone is given in
Plate B of Fig. 6. Bedded shale (BSh): It has high GR read-
ing (>75 API) with bedding or lamination observed on FMI
images (see Plate A in Fig. 7). Massive shale (MSh): It has
high GR readings (>75 API) without any bedding structure
observed. An example can be seen in the upper section
of Plate B, Fig. 7). Bedded silt (BSIt): It has a GR reading
between 65 API and 75 API with bedding or lamination
observable on images. An example of such facies is given
in the lower section of Plate B, Fig. 7.
Depositional environment interpretation
One of the main goals for electrofacies analysis is to
reconstruct the depositional environment. However, as
Walker (1978) pointed out, “many, if not most, facies de-
 ned in the  eld have ambiguous interpretations - a cross-
bedded sandstone, for example, could be formed in a me-
andering or braided river, a tidal channel, an o shore area
dominated by alongshore currents”. Therefore, it is impor-

commonly hampered by the fact that
very similar facies can be produced
in di erent environmental settings
(Boggs, 1987). It is often impossible
to make a unique environmental in-
terpretation based on a single facies.
Depositional environment reconstruc-
tion can be improved if we study the
facies associations and sequences
once all individual facies have been
de ned. The sequence in which fa-
cies communally occur contributes
as much information as facies them-
selves for depositional environmental
interpretation.
An overall  ning-upward se-
quence has been de ned based on
sequence analysis utilizing the open-
hole logs and interpreted electrofacies
in the studied well as showing in Track
3, Fig. 11. The  ning-upward sequence
starts at 489m where an erosional
surface detected on FMI with mud
rip-up clasts as lag deposits above it
and ends at about 451m where shale
is deposited. The sequence indicates a
decrease in transporting power of cur-
rents during deposition.
Depositional Environment Interpretation
A particular depositional environment is de ned by a

posits with the top small interval from 474.8 - 475.4m as
possible levee or lateral accretion sediments. The paleo-
current direction in this channel is dominantly due north
with a unimodal pattern.
467.8 - 474.8m: The low section is comprised of
moderately sorted cross-bedded sands (CBSt) deposited
on an erosional surface at 474.8m. The upper section is
consisted of interbeds of wellsorted bedded sands, mas-
sive sands and cross-bedded sands.
The azimuth of the cross-bed dip in-
dicates an overall NNW paleocurrent
direction (see track 5 in Fig. 11). The
section is interpreted as  uvial chan-
nel deposits.
455.6 - 467.8m: The base contact
of the section is gradual other than
an erosional one with the underlain
channel deposits. The electrofacies
include interbeds of bedded sands
(BSt), bedded silts (BSIt) and bedded
shale (BSh). The section is interpreted
as lateral accretion deposits. The azi-
muth of the lateral accretion beds are
dominantly dipping towards SW.
451- 455.6m: The section is com-
prised of mainly bedded shale (BSh)
or mudstone and interpreted as  ood-
plain deposits.
447.3 - 451m: The section is comprised of bedded
silts (BSIt) and shale and interpreted as brackish bay

and lateral accretion - red). Track 6 - sorting index (yellow shaded zone - well sorted, pink
shaded zone - poor sorted and the rest zone - moderate sorted). Track 7 - lithology. Track
8 - FMI static images. Track 9 - Electrofacies. Track 10 - facies code. Track 11 - facies descrip-
tion. Track 12 - depositional environment interpretation.
mended to be placed towards the North of the current
well in order to trace the same point bar in the appraisal
or in ll drilling. Plot B is a cross section view of the channel
showing in Plot C (right) along the direction of E-W.
Optimum position for injection wells
When water injection wells are required for second-
ary recovery for this type of reservoir, it
is recommended to place the injectors
either on the upstream (South, refer
plot C in Fig. 12) and the downstream
(North, refer to plot C in Fig. 12) end
of the longitudinal sand bar for better
sweeping e ciency. This is because t
the favorable permeability direction is
at E-W due to the dominant northward
cross-beds dip. Water injection needs
to avoid going along with the favor-
able permeability direction with the
producers within the high perm anisot-
ropy reservoirs.
Conclusions
A log-based sedimentological
characterization work ow for electro-
facies and depositional environment
analysis is proposed in this paper. Elec-
trofacies is determined with integra-

OBMI - Is an Oil-base MicroImager tool used in non-
conductive, invert-emulsion mud environments.
References
1. Boggs, Sam Jr., 1987. Principles of sedimentology
and stratigraphy. Merrill Publishing Company, p.784.
2. Galloway, W.E. and
Hobday, D.K., 1983. Terrige-
nous clastic depositional envi-
ronmental systems. Springer,
New York.
3. Newberry, B., Han-
sen, S. and Perrett T., 2004. A
Method for Analyzing Textural
Changes within Clastic.
4. Environments Utiliz-
ing Electrical Borehole Imag-
es. Gulf Coast Association of
Geologic Societies (GCAGS).
5. Convention. San Anto-
nio Texas, USA, Oct. 2004.
6. Selley, R.C. , 1970. An-
cient sedimentary environ-
ments. 1
st
ed. Chapman &
Hall, London.
7. Serra, O., 1972. Diag-
raohies and stratigraphie. In:
Mem. B.R.G. M., 77, p. 775-
832.

H3N, H3 and H4 (Fig. 3), and comprise stacks of numerous
individual reservoirs in thinly bedded sand layers of
lacustrine and fluvial origin.
In the TGT field, the dominant structural features are
ENE-WSW trending en-echelon faults, which are primarily
listric in character, with a strike-slip component. Most
faults die out upwards in the Lower Miocene strata but
some extend through the Bach Ho shale into the Middle
Miocene. An example is the major fault separating the H1
fault block and the Hai Su Trang field in the North of the
TGT field. Some faults extend downwards to basement,
whilst many sole out in the D Sequence shale (Fig. 4).
At different structural horizons, the reservoirs have
been subdivided into numerous compartments in fault
blocks or dip closures combined. The existence of the
compartments was supported by the PVT and RCI data
from many TGT drilled wells.
A zonation scheme was developed for reservoirs in
stacked sand systems in the fault blocks based on the log,
biostratigraphic and pressure data. As a result, these have
been subdivided into four main zones with 56 reservoirs
(Fig. 5).
The Intra Lower Bach Ho 5.1 reservoirs are very thin,
consisting of very fine- to medium-grained sandstones,
Te Giac Trang field: Geological features,
reservoirs and field development concepts
Pham Tuan Dung, Pham Thi Thuy, Nguyen Manh Tuan, Branimir Gojsic
Hoang Long JOC
Abstract
The Te Giac Trang (White Rhinoceros) Field is located in the Northern part of Block 16-1 in the Cuu Long Basin