Geological Survey of Denmark and Greenland Bulletin
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Nr. 4, Review of Survey activities 2003, pp. 97-100 |
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97
The Vietnam Petroleum Institute (VPI) and the Geological
Survey of Denmark and Greenland (GEUS) have carried out
a programme of geoscientific research and institutional
capacity building since 1995. It has included geoscientific
projects focused on assessment of the hydrocarbon potential
of selected sedimentary basins, technology transfer and in-
house training at VPI in Hanoi and at GEUS in Copenhagen.
Co-operation is continuing within the framework of a new,
long-term project that aims to strengthen research capacity in
Vietnam within the fields of basin analysis and modelling.
Survey of Denmark and Greenland (GEUS) have carried out
a programme of geoscientific research and institutional
capacity building since 1995. It has included geoscientific
projects focused on assessment of the hydrocarbon potential
of selected sedimentary basins, technology transfer and in-
house training at VPI in Hanoi and at GEUS in Copenhagen.
Co-operation is continuing within the framework of a new,
long-term project that aims to strengthen research capacity in
Vietnam within the fields of basin analysis and modelling.
History of co-operation
In 1993 CCOP-representatives (Co-ordinating Committee
for Geoscience Programmes in East and Southeast Asia) vis-
ited GEUS to investigate the possibility of co-operation
within research capacity development in the CCOP-coun-
tries. The Danish Energy Authority (DEA) subsequently
approved a project proposal, and the first joint project
between VPI and GEUS was initiated in 1995. The com-
mencement of geoscientific studies showed an urgent need
for interpretation tools at VPI, and modern geological and
geophysical interpretation facilities were installed at VPI in
1996 with support from the Danish International
Development Assistance (Danida). Following the successful
completion of the first geoscientific project, DEA approved
funding for a second phase. The projects were accompanied
by a series of CCOP workshops held at VPI, and `On-the-
Job-Training' (OJT) programmes at GEUS for VPI geosci-
entists (Nielsen et al. 2003).
for Geoscience Programmes in East and Southeast Asia) vis-
ited GEUS to investigate the possibility of co-operation
within research capacity development in the CCOP-coun-
tries. The Danish Energy Authority (DEA) subsequently
approved a project proposal, and the first joint project
between VPI and GEUS was initiated in 1995. The com-
mencement of geoscientific studies showed an urgent need
for interpretation tools at VPI, and modern geological and
geophysical interpretation facilities were installed at VPI in
1996 with support from the Danish International
Development Assistance (Danida). Following the successful
completion of the first geoscientific project, DEA approved
funding for a second phase. The projects were accompanied
by a series of CCOP workshops held at VPI, and `On-the-
Job-Training' (OJT) programmes at GEUS for VPI geosci-
entists (Nielsen et al. 2003).
The two first geoscientific projects were aimed at an analy-
sis of the hydrocarbon potential of the Song Hong Basin (Fig.
1). Seismic interpretation, field work, stratigraphic evalua-
tion, and assessment of results from the few exploration wells
drilled in the basin were carried out (Dien et al. 1997, 1998,
1999; Andersen et al. 1998, 1999; Nielsen et al. 1999).
Seismic facies analyses together with investigations of ther-
mally immature potential source rocks at localities in the
Song Hong Basin where inversion structures expose oil-prone
Oligocene lacustrine mudstones and thin coals, led to the
identification of areas for future hydrocarbon exploration
(Petersen et al. 2001, in press).
1). Seismic interpretation, field work, stratigraphic evalua-
tion, and assessment of results from the few exploration wells
drilled in the basin were carried out (Dien et al. 1997, 1998,
1999; Andersen et al. 1998, 1999; Nielsen et al. 1999).
Seismic facies analyses together with investigations of ther-
mally immature potential source rocks at localities in the
Song Hong Basin where inversion structures expose oil-prone
Oligocene lacustrine mudstones and thin coals, led to the
identification of areas for future hydrocarbon exploration
(Petersen et al. 2001, in press).
The implementation of these initial projects revealed a
fundamental need for enhancement of the research skills of
VPI geoscientists as part of an institutional development pro-
gramme. An application for a long-term geoscientific research
capacity building project was submitted to Danida's ENRECA
project in the year 2000.
VPI geoscientists as part of an institutional development pro-
gramme. An application for a long-term geoscientific research
capacity building project was submitted to Danida's ENRECA
project in the year 2000.
Basin analysis and assessment of hydro-
carbon potential
carbon potential
The ENRECA project was approved in August 2001. The
main aims were to undertake an integrated analysis and mod-
elling of sedimentary basins in Vietnam, to assess their hydro-
carbon potential and to establish a geoscientific background
main aims were to undertake an integrated analysis and mod-
elling of sedimentary basins in Vietnam, to assess their hydro-
carbon potential and to establish a geoscientific background
Geological Survey of Denmark and Greenland Bulletin 4, 97100 (2004) © GEUS, 2004
Petroleum potential of sedimentary basins in Vietnam:
long-term geoscientific co-operation with the Vietnam
Petroleum Institute
long-term geoscientific co-operation with the Vietnam
Petroleum Institute
Lars Henrik Nielsen and Ioannis Abatzis
Fig. 1. Regional map showing the prospective Vietnamese Cenozoic off-
shore basins.
on which decisions concerning exploration and exploitation
of hydrocarbons could be based. The studies are carried out
by geoscientists from VPI and GEUS, with support from sci-
entists at the Hanoi University of Mining and Geology,
Vietnam and the University of Copenhagen, Denmark. The
first phase of the project, focusing on the Cenozoic Phu
Khanh Basin offshore central Vietnam (Fig. 1), will last for
three years; long-term co-operation can be extended in up to
four phases.
of hydrocarbons could be based. The studies are carried out
by geoscientists from VPI and GEUS, with support from sci-
entists at the Hanoi University of Mining and Geology,
Vietnam and the University of Copenhagen, Denmark. The
first phase of the project, focusing on the Cenozoic Phu
Khanh Basin offshore central Vietnam (Fig. 1), will last for
three years; long-term co-operation can be extended in up to
four phases.
One of the principal short-term objectives is to provide a
research-driven assessment of the hydrocarbon potential of
the basin. Activities initiated during the first phase of the pro-
ject include seismic interpretation, field work, drilling of a
500 m deep core-well, geochemical and petrographic analy-
ses, the initiation of five Vietnamese and four Danish M.Sc.
studies, and several training courses.
the basin. Activities initiated during the first phase of the pro-
ject include seismic interpretation, field work, drilling of a
500 m deep core-well, geochemical and petrographic analy-
ses, the initiation of five Vietnamese and four Danish M.Sc.
studies, and several training courses.
Seismic interpretation
The Phu Khanh Basin is almost unexplored; it is covered only
by an open seismic grid and no wells have yet been drilled.
The Cenozoic basin-fill overlies strongly faulted older sedi-
mentary rocks and granitic basement that crop out along the
present-day coastline. The basement is cut by deep, listric,
eastward-dipping faults formed during rifting, which proba-
bly began during the Palaeogene. The basin-fill consists of a
syn-rift succession separated from the overlying post-rift suc-
cession by an unconformity that may be related to the open-
ing of the South China Sea. On seismic profiles the syn-rift
wedges are characterised by continuous reflectors interpreted
to represent lacustrine sediments, i.e. potential source rocks,
by an open seismic grid and no wells have yet been drilled.
The Cenozoic basin-fill overlies strongly faulted older sedi-
mentary rocks and granitic basement that crop out along the
present-day coastline. The basement is cut by deep, listric,
eastward-dipping faults formed during rifting, which proba-
bly began during the Palaeogene. The basin-fill consists of a
syn-rift succession separated from the overlying post-rift suc-
cession by an unconformity that may be related to the open-
ing of the South China Sea. On seismic profiles the syn-rift
wedges are characterised by continuous reflectors interpreted
to represent lacustrine sediments, i.e. potential source rocks,
whereas transparent zones are interpreted to represent fluvial
sands (Fig. 2).
sands (Fig. 2).
The Middle Miocene to Recent post-rift succession can be
divided into eight seismic sequences forming an eastward-
thickening succession. The lower three sequences are thin,
and their limited distribution is in part determined by struc-
tural uplift, whereas the more widely distributed overlying
five sequences show distinct basinward prograding shelf-edge
clinoforms. Analyses of the seismic facies and geometry of the
sequences suggest a variety of sandy depositional environ-
ment, such as fluvial channels, shorefaces and basin floor fans
that may all form potential reservoirs for hydrocarbons gen-
erated from syn-rift lacustrine source rocks. High amplitude
reflectors over structural highs are interpreted as Miocene
carbonate build-ups that can also form potential reservoirs.
thickening succession. The lower three sequences are thin,
and their limited distribution is in part determined by struc-
tural uplift, whereas the more widely distributed overlying
five sequences show distinct basinward prograding shelf-edge
clinoforms. Analyses of the seismic facies and geometry of the
sequences suggest a variety of sandy depositional environ-
ment, such as fluvial channels, shorefaces and basin floor fans
that may all form potential reservoirs for hydrocarbons gen-
erated from syn-rift lacustrine source rocks. High amplitude
reflectors over structural highs are interpreted as Miocene
carbonate build-ups that can also form potential reservoirs.
Oil seeps
Oil seeps occurring at the basin margin have long been
known from onshore coastal outcrops, but their nature has
remained controversial. However, geochemical analyses of
petroleum impregnation in cracks and fractures in weathered
Cretaceous granites, tar mats on the beach, oil on vegetation,
and mud with oil from shrimp-farm basins, have shown the
presence of biodegraded petroleum, with biological markers
pointing to a marly source rock with some terrestrial input
(Bojesen-Koefoed et al. 2003, 2004). The oil contains 30-
norhopanes characteristic of carbonate-derived petroleum, as
well as oleanane, a marker of contributions from angiosperm
higher land plants. The presence of petroleum in narrow fis-
sures in freshly cleaved granite testifies to the indigenous
known from onshore coastal outcrops, but their nature has
remained controversial. However, geochemical analyses of
petroleum impregnation in cracks and fractures in weathered
Cretaceous granites, tar mats on the beach, oil on vegetation,
and mud with oil from shrimp-farm basins, have shown the
presence of biodegraded petroleum, with biological markers
pointing to a marly source rock with some terrestrial input
(Bojesen-Koefoed et al. 2003, 2004). The oil contains 30-
norhopanes characteristic of carbonate-derived petroleum, as
well as oleanane, a marker of contributions from angiosperm
higher land plants. The presence of petroleum in narrow fis-
sures in freshly cleaved granite testifies to the indigenous
98
Fig. 2. Seismic profile of the Phu Khan Basin. The coastal oil seeps are located immediately west of the profile and indicate an updip migration path of
hydrocarbons generated from a possible kitchen in the Phu Khanh Basin. For location, see Fig. 1.
nature of the oil, and an origin from oil spills is therefore
unlikely. Samples from shrimp basins show the presence of
similar oil, although more altered by biodegradation. One
sample collected from a tar mat on the beach shows charac-
teristics similar to those of Cenozoic lacustrine oils found
elsewhere in Vietnam, for instance in the Song Hong Basin.
The close similarity of these oils suggests that pods of prolific
lacustrine petroleum source rocks may be regionally distrib-
uted.
unlikely. Samples from shrimp basins show the presence of
similar oil, although more altered by biodegradation. One
sample collected from a tar mat on the beach shows charac-
teristics similar to those of Cenozoic lacustrine oils found
elsewhere in Vietnam, for instance in the Song Hong Basin.
The close similarity of these oils suggests that pods of prolific
lacustrine petroleum source rocks may be regionally distrib-
uted.
Rift-lake successions and source rocks
In order to investigate the formation and hydrocarbon poten-
tial of rift-lake systems associated with transtensional fault-
ing, outcrop studies were carried out in the Song Ba Trough
supplemented by studies of a continuous core from the 500
m deep ENRECA-1 well. The Song Ba Trough was formed
by transtensional faulting in the onshore continuation of the
Tuy Hoa shear zone that marks the southern boundary of the
Phu Khanh Basin (Fig. 1). The outcrops expose coarse-
grained sandstones and conglomerates interbedded with
lacustrine mudstones and scattered coal beds. The core-well
encountered 480 m of sediments, beginning with thin fluvial
sandstones overlying granite. The sandstones are overlain by
lacustrine mudstones interbedded with thin sandstones,
whereas fluvial sandstones dominate the upper part of the
core. The lacustrine mudstones contain organic matter, com-
monly exceeding 5 wt%, and many samples have a hydrogen
index (HI) of more than 300 mg HC/g TOC (total organic
carbon), occasionally exceeding 700 mg HC/g TOC (Fig. 3).
The organic matter is mainly composed of fluorescent amor-
phous organic matter, alginite and liptodetrinite, corre-
sponding to type I kerogen, and may be an excellent source
for oil. The results suggest that oil-prone mudstones were pri-
marily formed in periods when the sedimentation rate was
outpaced by formation of new accommodation space.
tial of rift-lake systems associated with transtensional fault-
ing, outcrop studies were carried out in the Song Ba Trough
supplemented by studies of a continuous core from the 500
m deep ENRECA-1 well. The Song Ba Trough was formed
by transtensional faulting in the onshore continuation of the
Tuy Hoa shear zone that marks the southern boundary of the
Phu Khanh Basin (Fig. 1). The outcrops expose coarse-
grained sandstones and conglomerates interbedded with
lacustrine mudstones and scattered coal beds. The core-well
encountered 480 m of sediments, beginning with thin fluvial
sandstones overlying granite. The sandstones are overlain by
lacustrine mudstones interbedded with thin sandstones,
whereas fluvial sandstones dominate the upper part of the
core. The lacustrine mudstones contain organic matter, com-
monly exceeding 5 wt%, and many samples have a hydrogen
index (HI) of more than 300 mg HC/g TOC (total organic
carbon), occasionally exceeding 700 mg HC/g TOC (Fig. 3).
The organic matter is mainly composed of fluorescent amor-
phous organic matter, alginite and liptodetrinite, corre-
sponding to type I kerogen, and may be an excellent source
for oil. The results suggest that oil-prone mudstones were pri-
marily formed in periods when the sedimentation rate was
outpaced by formation of new accommodation space.
Significance for future exploration activi-
ties and research
ties and research
Interpretation of the seismic profiles suggests the presence of
possible reservoirs and deep-seated kitchens in the Phu
Khanh Basin. One possible kitchen is situated down-dip
along a likely migration route to the oil seeps (Fig. 2). Thus,
there is evidence that the common petroleum system found
in south-east Asian basins, which rely on syn-rift lacustrine
mudstones and coals, is also active in the Phu Khanh Basin.
The investigated rift-lake succession in the onshore Song Ba
Trough may thus be a valid analogue for older and deeply
buried syn-rift sequences in the Phu Khanh Basin.
possible reservoirs and deep-seated kitchens in the Phu
Khanh Basin. One possible kitchen is situated down-dip
along a likely migration route to the oil seeps (Fig. 2). Thus,
there is evidence that the common petroleum system found
in south-east Asian basins, which rely on syn-rift lacustrine
mudstones and coals, is also active in the Phu Khanh Basin.
The investigated rift-lake succession in the onshore Song Ba
Trough may thus be a valid analogue for older and deeply
buried syn-rift sequences in the Phu Khanh Basin.
99
Fig. 3. Core log of a selected interval of the ENRECA-1 core-well, which
penetrated a 500 m thick rift-succession of lacustrine mudstones. A sig-
nificant amount of preserved organic matter indicates an excellent source
rock for oil generation. The core-well is located in the Song Ba Trough, see
Fig. 1. HC, hydrocarbon; HI, hydrogen index; TOC, total organic carbon.
100
Acknowledgements
The Energy Research Programme of DEA, the Royal Danish Embassies in
Hanoi and Bangkok, Danida's Fellowship Center and Danida are
thanked for their financial support. VPI and PetroVietnam are acknowl-
edged for their institutional support and permission to publish the
results.
Hanoi and Bangkok, Danida's Fellowship Center and Danida are
thanked for their financial support. VPI and PetroVietnam are acknowl-
edged for their institutional support and permission to publish the
results.
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Authors' address
Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: lhn@geus.dk
Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: lhn@geus.dk
