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MINISTRY OF EDUCATION AND TRAINING

HA NOI UNIVERSITY OF MINING AND GEOLOGY

____________________

TRAN CHAU GIANG

CHARACTERIZATION OF THE CENOZOIC

PETROLEUM SYSTEM IN THE NORTHEASTERN OFFSHORE

SONG HONG BASIN

Subject area: Engineering geology

Code: 62.52.05.01

SUMMARY OF DOCTORAL THESIS WORK

HANOI -2014


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The thesis work has been completed at: Ha Noi University of Mining

and Geology

Principal Advisors:

1) Professor, Doctor of Science. Mai Thanh Tan

2) Dr. Le Tuan Viet

Judge 1: Associate Professor, Doctor. Pham Huy Tien

Judge 2: Dr. Nguyen Huy Quy

Judge 3: Dr. Cu Minh Hoang

The doctoral thesis work will be defend at the University Council of

Scoring Thesis Meeting at the Hanoi University of Mining and

Geology at .hour, day ., monthyear ..

You can find out the thesis in the libraries: National Library, Hanoi

or Library of Ha noi University of Mining and Geology


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INTRODUCTION

The necessi tySong Hong Basin is complex sedimentary basin, including several

tectonic elements with different oil and gas potential. The VPI-

IDENMITSU (2005-2007) project has confirmed non-marine dual

petroleum system (lacustrine and fluvio-deltaic) in the Song Hong

basin by advanced geochemical analysis. Due to no oilsource rock

correlation, the characterization of petroleum system in the

Northeastern offshore Song Hong basin has yet to be confirmed.

In 2008, the oil discovery by 106-HR-1X has proven the

hydrocarbon potential of the Pre- Cenozoic carbonate basement Play.

Next well 106-HR-2X was drilled through the oil reservoir bearing in

the PreCenozoic carbonate basement and penetrated a thick shale.

It is a questionable that this Pre- Cenozoic shale is a new source

rock. Well 107-PL-1X drilled in 2013 in the rich organic source area,

and has the same structural trend as 106-HR prospects. However the

well was dry. Other latest exploration wells have discovered gas

condensate with heavy H2S and CO2polluted in the reservoir fluid.

These facts show many issues have to resolved such as the quality

and distribution of source rocks, or which risk factor of geological

parameters in the petroleum system have affected the results of

exploration in the area of Northeastern (NE) offshore Song Hong

basin. Therefore, the topic " Character ization of the Cenozoic

petroleum system in the Northeastern of fshore Song Hong Basin"

was chosen with the objectives and research tasks are as follows:

Objectives:


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- To get better understand about the characterization and area

distribution of petroleum source rocks of Cenozoic sediments in the

NE offshore Song Hong Basin.- Contribute to improve the methodology for petroleum systems

evaluation and risk analysis in exploration.

Tasks:

- Integrate geological data and geophysical data to clarify the

regional geological setting.

- Research to clarify the characterization and level of maturity

and timing of HC generation and migration, identify the origin oil

generated source rock in the NE offshore Song Hong Basin.

- Determine the area distribution of source rocks and HC potential

areas.

Object and scope of the study:

The scope of the study include the block 106 area, Northwestern

of block 102 and North part of block 107 offshore Song Hong basin

that separated to others area by Song Lo fault. The objective to study

is Cenozoic petroleum system.

Thesis protection:

Thesis 1. Study results of the geochemical characterization

identified a lacustrine petroleum system related to the Oligocene

source rock exist in the NE offshore Song Hong Basin. The source

rock contains moderate to good organic richness, kerogen type II and

mixed type II/ III, locates in the grabens and half grabens within the

study area. Based on all available geochemical data of the Miocene

shale and Pre- Cenozoic shale that identifies these shales are not

qualified to be a source rock.


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Thesis 2. Based on the study of factors impact on risk of the

petroleum system such the origin, maturity, the Oligocene sediment

thickness and the distribution of potential prospects, restore thegeological development through the ages that are enable to identify

the Thuy Nguyen graben has lowest exploration risk. Next is the

Kien An graben. The South Bach Long Vi Island area and NW edge

of block 102 are the areas of high exploration risk.

New findings of the thesis work:

- Based on latest exploration data, results of thesis work has

contributed accurately geochemical characteistics of the NE offshore

Song Hong basin. The Pre- Cenozoic shale below the carbonate layer

bearing oil has terrestrial lithoface, deposites under oxidizing

condition environment, with poor organic contain that is not

qualified to be a source rock.

- The new structural maps were built have contribution to get

better understand of Late Oligocene inversion event affect oil and

gas potential of the area of Northeatern Offshore Song Hong basin.

The scienti f ic and practical contr ibutions:

* Scientific contribution: The results of research allowed identify

the characterizations and the distribution of source rock to get better

understand of petroleum system in NE of Song Hong basin, offshore

Vietnam.

* Practical contribution:Contribute to improve the effectiveness

of HC potential assessment for the NE of Song Hong basin, and to

serve the Oil companies in the exploration and exploitation activities.

The layout of the thesis:

The thesis consists of 04 chapters excluding the introduction and

conclusions, recommendations, papers publication and reference


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lists. The entire content of the thesis is presented in 135 pages, 24

tables and 89 figures.

Chapter 1SUMMARY GEOLOGICAL STRUCTURE IN THE

NORTHEAST AREA OFFSHORE SONG HONG BASIN

1.1. Overview the geology of study area

1.1.1. Location

Study location is part of

Northeast Song Lo fault offshore

Song Hong basin. Water depth

from 30-40m. (fig.1.1)

1.1.2. Exploration hi story

Fisrt exploration work began

in 1978. In 1988, first PSC was

signed for block 106, and a part

of block 102, 103 and 107

between PVN and TOTAL. In

1992, IDEMITSUPVN signed

a PSC for block 102/91. Next the

blocks 102 106 with total area

of 10700 km2 was signed

between PVN and ATI

Petroleum Inc in 2000. Recently,

this PSC has relinquished area

and maintained in area of 225

km2. The remaining area now is

Fig. 1.1: Structural map of Topbasement Song Hong basin and

study area location (N.T.Dau. et

al, 2012)

block 102/10 and block 106/10 with PVEP operator. From 1990 to

present, in the study area were acquired more than 15,000 km of 2D,


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and over 3000 km2 of 3D seismic, more than 10 exploration wells.

Several studies are available as Geochemical model of Song Hong

Basin (N.T Dau, L.V Hien, 1997), Outcroup study in Bach Long Viisland, Do Son, Kien An, Elephant Mountain, and Cat Ba Island (P.Q

Trung, 1998), Investigate the amount of HC generated and migrated

from source rock to trap in the Song Hong basin by SIGMA 2D and

BSS softwares (N.T.B Ha, 2010), Final Report on the analysis and

modeling Song Hong Basin (VPI - GEUS, 2001), Report on

Characterization of petroleum systems in the Song Hong Basin by

State of the art Geochemical Technology (VPI-IDENMITSU, 2007).

1.2. Regional setting

1.2.1 L ithostratigraphy

Song Hong Basin

stratigraphic units consist of: (i)

Pre-Cenozoic basement; (ii) Phu

Tien Formation (E2pt); (iii) Dinh

Cao Formation (E2c); (iv)

Phong Chau Formation (N11pc);

(v) Phu Cu Formation (N12pc);

(vi)Tien Hung Formation

(N13th); (vii) Vinh Bao

Formation; (viii) Formation of

Hai Duong - Kien Xuong (N2-Q)

(Figure 1.2).

1.2.2 Tectono-structure

There exist in the study area

02 fault systems. The NW-SE

and NE-SW fault systems.

Fig.1. 2: Stratigraphic column of

the offshore Northeast S.Hong

basin (After N.T.Dau et.al, 2012)


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These fault systems created structural type of dipping down to the

basin center and formed a series of grabens alternate half grabens.

The identified structural zonnation (Figure 1.3):Hai Phong Shelf:

The shelf located in the

northeastern part of the

study area, covers a

large area of the block

106 and block 101.

Thanh Nghe

undifferentiated

monocline:It is located

Fig.1. 3: Fault systems and structuralzonnation

to the West of the Song Chay fault.

Central trough: can be subdivided as

a) Miocene Inversion Zone

b) Dong Quan trough

North-East differentiated monocline: mades up of grabens, half

grabens, horsts, and basement uplifts. Detaily consists of:

a) Kien An Graben

b) Tien Lang - Ch Linh horst

c) Thuy Nguyen half graben

d) Trang Kenh Nose

e) Western Bach Long Vi trough

f) Yen Tu Horst

g) Southern Bach Long Vi trough

Tectonic evolution was constructed based on restoration cross

sections. The study results show the similarities and differences over

the period of development of the region on the two banks of Song Lo


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Fault. In Paleocene-Eocene to the Early Oligocene and Pliocene

Quaternary period are similar but different in period from late

Oligocene to late Miocene.1.3. Data base

The documents use in thesis work are more than 15000 km 2D

seismic, gravity maps of the Bac Bo Gulf, Vietnam geological maps,

well logs and obtained rock samples were analyzed for the

Petrography, Geochemistry, and Biostratigraphy studies. Especially

with 500 m of core samples from Enreca 3 well in Bach Long Vi

island to study sedimentary, litho-facies, and geochemistry of

Oligocene sediment.

Chapter 2

RESEARCH METHODS

2.1. Petroleum system and its role in oil and gas exploration

Petroleum system concept appears too many different definitions.

The term system includes source rock and reservoir rock, oil -

source correlation are considered a key factor in determining system

(Dow W.G, 1972). Synthesis of the concept put forward by many

authors, petroleum system is understood as a natural system where

exist generated petroleum source rocks with all the geological

elements and geological processes related to the ability to

accumulate oil and gas may occur.

In 1988, L.B Magoon had established a system classification,

which distinguishes the petroleum systems to sedimentary basins,

Plays and Prospects. Depend on the level of research, petroleum

system is evaluated as an overview to detail as scale of a country,

sedimentary basin, a play and to each independent prospect. The

basic methods of assessment can be summarized as follows:


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+ Analysis petroleum system was evaluated on the basis of the

total volume of HC generated/rock volume by Exxon.

+ Analysis petroleum system was evaluated on the prediction ofpetroleum geology characteristic (Delphi method), mainly based on

the experience of experts.

+ Analysis petroleum system was evaluated on Geochemical

material balance based on the calculation of the amount of oil and

gas generated from source rock, as well as oil and gas were migrated

and can accumulate in the trap.

+ Analysis petroleum system was evaluated on extrapolation of

production history.

+ Analysis petroleum system

by Play fairway analysis (based on

geological model and statistical

data) allows determine the change

of the geological factors related to

the oil and gas accumulation in an

considered region.

Figure 2.1: Play concept

[CCOP, 2000]

In the thesis work, Play assessment is applied to solve remaining

problems in petroleum system in the study area.

2.2. The geochemical methodology

Complex sets of geochemical index in evaluating the capacity of

HC generation of sediments used in the thesis are:

+ Combust a crushed sample of rock at 600C

+ Pyrolysis method Rock-Eval standards (RE)

+ Bitumen extraction method

+ Chromatography (GC)

+ Mass spectrometry analysis (GC-MS)


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+ The vitrinite reflectance (Ro,%)

2.3. Geochemical modeling

Geochemical modeling canreproduce the processes relating to

petroleum system in computer

from past to present time, which

enables to assess the timing and

location of generation, migration

and accumulation of Oil and Gas.

The soft ware used is SIGMA-2D.

Principles for SIGMA model is

explained detail as figure 2.2.

2.4. Petroleum system analysis

According to Magoon and Dow

(1994) to study a petroleum system

have to analyze four basic

elements includeing: source rock, Fig 2.2: SIGMA 2D outline

reservoir, seal and the overlying rock layer with the combination of

three processes are: the formation of oil and gas traps, the oil and gas

generation, migration and conservation of oil and gas after trapped.

2.5. Geological risk assessment

The purpose of risk assessment in petroleum system analysis is to

estimate the probability of discovery prior to drill of a prospect/play.

The probability of discovery is defined as the product of the

following major probability factors, each of which must be evaluated

with respect to presence and effectiveness. According to CCOP risk

assessment guideline, the 04 factors are: Reservoir (P1), Trap (P2),

Petroleum charge system (P3), and retention after accumulation (P4).


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The probabilities of these factors are estimated with respect to the

presence and effectiveness of the geological process associated with

them. The probability of discovery is calculated using the formula: P = P1*P2*P3*P4 (2.1)

Where

P: Probability of discovery oil and gas (or probability of

simultaneous occurrence of the events associated with each

independent)

P1: The probability of the presence of reservoir rock includes: i)

P1a: Probability of existence of reservoir facies; ii) P1b: Probability

of effectiveness of the reservoir

P2: The probability of the presence of a trap includes: i) P2a the

probability of presence of the mapped structure and ii) P2b the

probability of effective seal mechanism for the mapped structure

P3: The probability factor for the petroleum charge system

includes: i) P3a the probability of effective source rock and ii) P3b

the probability of effective migration

P4: Probability of effective retention of HC in the prospect after

accumulation.

Tab.2.1: Probability of

existence of reservoir facies

Tab 2.2: Probability of

effective reservoir with depth


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In essence, the probability of discovered of an object is:

P = P1a* P1b* P2a* P2b* P3a* P3b*P4 (2.2)

Probability value of each parameter is defined rely on subjectiveknowledge, extrapolation from the analysis geological and statistical

data. Following the guidance of CCOP, for example, the tables 2.1

and 2.2 describe the probabilities of P1a and P1b parameters.

Chapter 3

CHARACTERIZATION OF SOURCE ROCK IN THE

OFFSHORE NORTHEAST SONG HONG BASIN

3.1. Organic richness in source rock

+ Pre-Cenozoic sediments: very poor in organic matter and not

be generated oil and gas. TOC values from 0.03 to 0.05% weight.

Unmeasurable indicators S1, S2, PI, HI and Ro.

+ Eocene sediments:no wells confirm met Eocene.

+ Oligocene sediments:organic matter is moderate to good. 8/14

samples in 106-HR-1X well have TOC values> 1%. Samples on

Bach Long Vi Island with TOC values from 1.5 to 6.59%, 10/100

samples have S1 value from 0.08 to 1.19 mg/g, and 99/100 samples

with S2 > 10 mg/g, in average of 17 mg/g represented the organic

contain from good to very good.

+ Lower Miocene sediments: all samples get very low value, so

not analyisis.

3.2. Kerogen type

+ Oligocene sediments:Figures 3.1a and 3.1b (N.T.B.Ha, 2010)

show the Oligocene (brown points) found in wells in block 107 and

Chi Linh Yen Tu host with HI values


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rock is able to generate mixture oil and gas and have reach maturity

level.

Figure 3.1a: Plot HI and Tmax by

the structural zonnation in the

Song Hong Basin (NTB Ha,

2010)

Figure 3.1b: Plot (S1 + S2 mg/g)

and TOC% by structural

zonnation in Song Hong Basin

(NTB Ha, 2010)

Results of the well ENRECA 3 on Bach Long Vi Island show

sample populations fall into the group of kerogen type II and I.

Oligocene sediments have oil prone with capability from fair to good

(Figure 3.2 a, b) .

+ Lower Miocene sediments: almost HI


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Figure 3.2a: Plot HI and Tmax at

well ENRECA 3

Figure 3.2b: (S1+S2 mg/g) v

TOC % at well ENRECA 3

3.3. Depositional environement of organic matter

The HI vs TOC diagram (Figure 3.3), results of gas

chromatography (GC) (Figure 3.4) indicate depositional environment

of organic matter of Oligocene source rocks in the study area is

mainly lacustrine origin.

Results of gas chromatography (GC) from Oligocene, Lower

Miocene at 106-HR-1X, 106-HR-2X, 107-BAL-1X reflect the origin

of organic matter was derived from high plants (Figure 3.5a, b).The

Ts/Tm vs Oleanane/C30 Hopane diagram was used (Okui et al,

2007) to distinguish lacustrine petroleum system from fluvio-deltaic

petroleum system. This plot indicates the oil from Ham Rong field is

lacustrine origin.

3.4. Maturity of source rock

+ Oligocene sediments:Vitrinite index (Ro,%) from well Enreca

-3 has value


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sediments have varied thermal maturity level from low maturity to

oil window.

+ All Lower and Middle Miocene samples from Ham Rong-YenTu and Pha Lai wells are immature.

Figure 3.3: The diagram defines

Oligocene depositional

environment of organic matter in

Song Hong Basin (points brown)

(NTB Ha, 2010)

Figure 3.4: The diagram

defines depositional

environment of organic matter

by Pr / C17 and Phy / C18 in

the study area (Ha, 2013)

Figure 3.5a: The

Oleanane/C30Hopane vs

Ts/Tm diagram of study area

Figure 3.5b: Steranes C27-

28-29 triangle chart


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3.5. Oil to source rock correlation

Oil sample from Ham Rong was analysed that shows normal

crude oil and displays API gravity of 39,22

0

API, moderate waxcontent (11,3%), moderate viscosity (4,058Cst) and moderately low

pour point (270C). This oil is low sulphur content (0,062%Wt), low

nickel and vanadium contents (Ni=1,70ppm, V=trace) suggesting

characteristics of C class (After Barwise, A.J.C, 1984) derived from

lacustrine source rocks.

Results of gas chromatogram of the DST#1 oil from 106-HR-2X

show the presence of saddle shape distribution decreases with

increasing number of carbon atoms (Figure 3.6 and 3.7).

Figure 3.6: C15+ saturates

chromatogram of oil and

extracts from 106-HR-1X

Figure 3.7: C15+ saturates

chromatogram of oil and

extracts from 106-HR-2X

Pristane/phytane ratio is 2,95 and 2,9 for 106-HR-1X ST4, and106-HR-2X respectively. Consequently, these features are typical of

organic matter derived from a terrestrially dominated source,

deposited in submerged environment under reducing and weak

oxidizing conditions.

The GCMS analysis of saturate fraction of crude oil from Ham

Rong field (Figs. 3.8a & 3.9a), the mass fragmentograms of m/z191


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shows a wide Hopane distribution, gradually decreased with

reducing number of carbon atoms, which are recognised as organic

matter derived from a terrestrially dominated source, deposited inreducing environment condition. The presence of Oleanane is land

plant indicators. Distribution of Tricyclic Terpanes sharply

appearence from T2 to T8 suggested lacustrine algae have

contributed in the parent material.

(a)

(b)

Figure 3.8: Gas chromatography-

Mass Spectrometry (GCMS) of

saturates fraction of oil sample from

106-HR-1X

(a)

(b)

Figure 3.9 Gas

chromatography-Mass

Spectrometry (GCMS) of

saturates fraction of oil

sample from 106-HR-2X

The m/z 217 sterane distribution (Figures 3.8b and 3.9b) is

characterised by C29 steranes are higher than those of C27 and C28.

These features suggest the oil derived from terrestrial source. The 4-

Methyl C30-Sterane (peak 42) widely confirmed as the oil is derived

mainly from lacustrine algal organic matter.


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Oil Source rock correlation defines the origin of oil generated

from lacustrine algal organic matter that match with Oligocene

source rocks in the study area.3.6. H2S origin in crude oil

Worldwide rift lakes in the Paleocene and Eocene have met in

Spain, southern France, in Utah and Colorado (USA). They formed

in surface of Carbon-Permian or Devon limestone. By this the

carbonate material easily osmoses in the lake that created favorable

condition for carbonate development of along the evaporation zone

of lakes.

The exploration wells in the study area have penetrated thin

limestone in the Oligocene. Theoryly, the H2S and CO2pollution in

the oil reservoir in the Ham Rong fields were the product of thermal

sulfate reduction process (of CaSO4) in carbonate rocks explained

by Angler-Gofer Scheme formula:

CaSO4+ CH4= CaS + CO2+ 2H2O (3.1)

CaS + CO2 + H2O = CaCO3+ H2S (3.2)

Chapter 4

DISTRIBUTION OF SOURCE ROCK AND POTENTIAL

ZONNATION IN THE OFFSHORE NORTHEART SONG

HONG BASIN

4.1. Oligocene sediment distribution and evolution

On the basis of seismic data and results of latest wells, Phd

student have participated to re-interprete some seismic lines at VPI

workstation. Results of biostratigraphic studies are used to identify

and interprete the seismic reflection surface include:

+ Top Kainozoic basement

+ Top Lower intra- Oligocene (U500)


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+ Top of uncomformity is near top of Lower Oligocen (U400)

+ Top Oligocene (U300)

+ Top intra Middle Miocene (U220)+ Top Upper Miocene (U100)

Some of these seismic horizons just matched tie within a small

area. Oligocene stratigraphic sequence in the center area of block

106 can divide into two parts separated by U400, which is relatively

continuous. 107-TPA-1X supposedly was drilled to

Eocene?/Oligocen (U500). Well ties to seismic data just observed in

the small troughs in the NE Song Lo fault and the Southern part of

Bach Long Vi Island. The structural maps of Top Basement, Top

U400, Top U300 and the isopach map of Oligocen in scale 1/200.000

were built.

The isopach maps of Lower Oligocene (U400-Bsmt) and

Oligocene (U300-Bsmt) (Figures 4.1 and 4.2) represent the

distribution area of Oligocene significant altenated in the offshore

Northeast Song Hong basin. Figure 4.1 shows at the end of Early

Oligocene time, 02 closed lakes systems trending NE-SW and NW-

SE were developed in the study area. The basement hosts within

Ham Rong field area as boundary separate the lakes. In the Northern

part of block 107, which is belong to South Bach Long Vi trough

also has a deep lake. The lakes in Southeast edge of block 106 and

North of block 107 tend to be open to the Southeast, while the closed

lakes within the Northwest of blocks 102-106 and Northeast Yen Tu

host remain stable development.

Three (03) geological and physical seismic sections were selected

cut through the main structural zonations in the study area to


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investigate the level of development of the Oligocene sediment in

between Top of basement to Top Oligocen (U300).

Figure 4.1: Isopach map of

Lower Oligocene (U400-

Bstm)

Figure 4.2: Isopach map of

Oligocene (U300-Bstm)

The chronostratigraphy chart of seismic line 89-1-100 represents

at early stage of basin formation, a series of grabens and half grabens

filled by Oligocene sediment in the Eastern area of block 106. At

about 28 Ma in this area had experienced a compression phaseresulting in local cockle, inversion that lead to erode a big volume of

sediment during approximately 5 million years. On this line shows

the area of lakes reduced during period from Early Oligocene to Late

Oligocene.

On line 89-1-36a shows initially there some grabens development

in the area of Northwest block 102-106. These lakes are smaller thanthat lakes developed in the Eastern part of block 106. During stage of

deposition, whole area was not be affected by Late Oligocene

compression phase. Sediment were supplied and filled up the

grabens.

On line 89-1-54 shows a large volume of sediment filled up the

grabens in the Southwest block 102 that resulted in strong subsidence


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and inheritedly development of series deep grabens from Oligocene

to Late Miocene time. Meanwhile in the central part of block 106

extending to Hai Phong shelf, the grabens just developed to end oflate Oligocene time, then area was sinking and less affected by

tectonic fault activity.

4.2. The factors for evaluating the potential of petroleum system

4.2.1 Process of sour ce rock maturi ty and HC generati on

The time of HC generation of Oligocene source rock is significant

difference according to the location survey points. Oligocene source

rock that observed in the Southeast block 106 has ealy HC

generation about 20 Ma . Recently, this source rock is still

generating oil and gas. At the lower part of Oligocene section, it is at

dry gas phase. In the Nortwestern block 106, at the lower Oligocene

section, source rock has started HC generation in about 14 Ma, while

the upper Oligocene is about 11 Ma.

4.2.2 Character izations of carbonate reservoir basement

Nine (09) exploration wells in the study area were drilled into the

Cenozoic basement and penetrated carbonate reservoir rock. The

documents of side wall cores, FMI log and wireline logs measured in

Ham Rong host show multi-types porosity ie: inter-granular,

vugs/cave and fractures. The vugs/cave porosity was calculated

separately from other. The rest types of porosity were calculated

together based on response of the density and neutron logs and

considered as matrix+fractured porosity. The porosity values from

side wall core samples are all less than 1%. The average porosity of

basement rock is 7% determined by logs. Cavern porosity if 100%.

As mentioned above, two main types of porosities were identified:

the matrix+fractured and cavern porosities. The NTG of these


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porosities were also identified separately. For fractured basement

segment the NTG ratio varies from 0,45 to 0,7. Meanwhile the NTG

of caver is applied 0,002 to 0,03 with assumption of cavern heightanalog from Ha Long Bay. Results reservoir testing measured

average permeability of 10 mD before aciding in basement rock and

40mD after aciding treatment, with horizontal permeability was

measured respectively at 8474 mD.ft and 21000 mD.ft

4.2.3 Seal characterization

Oligocene and Miocene shales play as local seal for carbonate

buried hill traps in the study area. Their thickness is from 20-150 m

with high clay contain (Illit > 50%, Kaolinit


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.

4.3. Risk assessment and potential zonnationThe results of seismic interpretation and mapping represent the

carbonate buried hill potential traps still remain in the study area.

They locate in the shallow water of northwest edge of block 102

(Tien Lang), in the Kien An and Chi Linh host, Thuy Nguyen half

graben, and South Bach Long Vi trough. All these structures are

close to the drilled wells. Review detaily results of drilled wells are

able to identify risk factors that will improve process risk analysis in

the study area. The analysis is performed on the assessment of the

involved geological processes and the facts of geological time.

Geological processes are firstly started with the formation of the

reservoir rock, next is the formation of a closed trap in relation to the

maturity of source rock, HC migration from source rocks to reservoir

rocks, the accumulation of HC in the trap and eventually progresses

after trapping and accumulating of hydrocarbons contained in it. The

main goal is just to know where is the location has above mentioned

factors are favorable or unfavorable to oil in carbonate basement play

and determine the value of probalilities.

Based on the guidance of

CCOP, 04 geological

factors are: reservoir

(P1), trap (P2), petroleum

charge system (P3) and

retention of HC (P4) are

used to estimate the

chance of success in term Fig.4.3: Potential zonnation of carbonate


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of geology, and predicte

the entirely change or

basement Play in the NE Song Hong

basin

partly change of geological factors in the a petroleum system ofNortheast offshore Song Hong basin. Figure 4.3 presents the

potential zonnations of the study area.

CONCLUSIONSAND RECOMMENDATIONS

The study results allows to point out some conclusions:

- Lacutrine Oligocene shale has been identified as an important

source rock exsit in the study area. This source contains moderate to

good organic richess, kerogen type II and mixed type II/ III with

early to oil windown of matutiry level. Recently, source rock in

Southeast block 106 is in wet gas phase. The source rock at Bach

Long Vi island has kerogen type II/I, good to excellent organic

richess, oil prone. Oligocene source in the study area has experienced

two phases of HC generation. Early phase is from 20 to 14 Ma; the

second phase is from 11 to 7 Ma. Time of HC generation varies by

structural zonnations within the study area. In deep grabens, this

source rock is still generating in HC.

- Crude oil from 106-HR basement reservoir is lacustrine algaes

origin. Results of biomarker analysis from oil are agreed with

extracts obtained from Oligocene source rock.

- Based on all available geochemical data, the Miocene shale and

Pre- Cenozoic shale are not identify as a source rock.

- Study results of geological development of Oligocene sediment

and history of local tectonic inversion express a large volume of

sediment were erodied during Oligocene to end of Late Miocene

time within the Bach Long Vi area. This is risk for timing factor of


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HC migration and trap formation and is not convenient for petroleum

system in the study area.

- Based on the study results of source rocks maturity, HCmigration and other parameters of the petroleum system have

allowed effectively application of probabilistic method in risk

assement, and established map of potential zonnation for northeast

offshore Song Hong Basin. Results are enable to identify the Thuy

Nguyen graben has highest oil and gas potential. Next to the Kien An

graben. The South Bach Long Vi Island area and Northwest edge of

block 102 are the areas of lowest potential.

From the results mentioned above, Phd student has some

recommendations:

1) To improve the effectiveness of source rock evaluation should

continuously carry out geochemical analysis for Pre- Cenozoic shale

as well as increase the amount of sample analysis for Cenozoic

sediment.

2) Further research on geothermal, paleo geothermal and heat

flow to exact time of HC generation and migration.

3) Supplemental research on sulfur and carbon isotope analysis as

well as biomarker analysis for reservoir fluid samples.

4) It is needed a parameter drilled well in combination with full

wireline logs measurement in entire KZ section to accurately

determine the absolute age and geological model of the study area.

5) Futher research on stratigraphic traps to accurately

HC potential of Northeast offshore Song Hong Basin.

6) Re-process seismic data in combination with available data of

blocks 102-106, MVHN02, blocks 103-107, and 100-101/ 4 in order

to improve the effectiveness of risk assessment for the whole area.


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LIST OF SCIENTIFIC WORKSRELATED TO THE THESIS

1.Tran Huu Than, Tran Chau Giang, Tran Nhat Dung, Nguyen DinhTy, Nguyen Trong Tin, Ngo Van Hung, 2005,The role and influenceof the Middle Miocene Inversion to oil and gas potential in theSouthwest area of Vinh Ninh fault, Conference Report of Sscienceand Technology 30 years of establishment of the Vietnam Oil andGas Corporation, p. 228-238.2. Tran Chau Giang et al, 2006,Petroleum activities in the Cenozoic

sedimentary basins of Vietnam, Collaborative research VIP- KIGAM,

Archives by Vietnam Petroleum Institute.3. Tran Chau Giang et al, 2007, Geological characteristics andhydrocarbon potential of Song Hong Basin. The joint study projectVPI-NIPPON OIL.Archives by Vietnam Petroleum Institute.4. Phan Tien Vien Nguyen Trong Tin, Hoang Ngoc Dang Trinh XuanCuong, Nguyen Anh Duc Tran Chau Giang et al, 2012,Evaluation of

potential oil and gas in the sea and the continental shelf of Vietnam,under "The Program of National basic survey and marine resourcemanagement by 2010, vision 2020, approved by the Prime Ministeron March 1, 2006 in accordance with Decision No. 47/2006 / QD-TTg., Archives by Vietnam Petroleum Institute.5. Tran Chau Giang, 2008,CO2 origin in the oil and gas reservoirsin the continental shelf of Vietnam, Conference Report on Scienceand Technology established 30 years Vietnam Petroleum Institute, p.433-443.6. Tran Chau Giang, Vietnam Tuan Le, Mai Thanh Tan, 2010, H2Sorigin in the crude oil at Yen Tu - Ha Long field,Oil and Gas Journal

No. 11/2010, p. 35-38.7. Tran Chau Giang, 2013, Risk analysis in evaluating petroleumsystems,Journal of Petroleum July 2013, p. 19-25.8. Tran Chau Giang, 2013,Applycation of the Bayers Theorem

in estimate conditional probability for interdependent prospect,,Journal of Petroleum in December 2013, p. 48-53.


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