MINISTRY OF EDUCATION AND TRAINING

HA NOI UNIVERSITY OF MINING AND GEOLOGY

LE TRUNG TAM

RESERVOIR CHARACTERIZATION, GEOLOGICAL MODEL

AND HYDROCARBON POTENTIAL OF PRE-CENOZOIC

CARBONATE, NORTHEAST SONG HONG BASIN

Major: Geological engineering

Code:62.52.05.01

SUMMARY OF THE PhD THESIS

Ha Noi- 2015

The thesis work has been completed at: Ha Noi Uneversity of

Mining and Geology.

Principal Advisor:

1.Dr. Pham Van Tuan

Ha Noi University of Mining and Geology

2.Dr. Cu Minh Hoang

PVEP Overseas.

Judge 1: Dr. Phan Tu Co

Vietnam Association of Petroleum

Judge 2: Dr. Nguyen Anh Duc

Vietnam Oil and Gas Group

Judge 3: Ass. Prof. Nguyen Van Phon

Vietnam Association of Geophysicists

The doctoral thesis work will be defend at the University

Council of Scoring Thesis Meeting at the Ha Noi University of

Mining and Geology at ……hour, day……, month….., year 2015

You can find out the thesis in the libraries: National library, or

Libarary of Ha noi University of Mining and Geology.

1

INTRODUCTION

1.The necessity

In 2008 and 2009, Petronas drilled 02 exploration and appraisal

wells on Ham Rong structure with the good results of DST in pre-

Cenozoic carbonate reservoir. In 2013 and 2014, Petrovietnam

Exploration Production Corporation (PVEP) drilled 02 exploration

wells on Ham Rong Dong and Ham Rong Nam prospect nearby Ham

Rong oil field. The DST results in pre-Cenozoic has oil and gas

discoveries with very good flow.

The recently oil and gas discoveries show the correctness of

Petrovietnam as exploration in pre-Cenozoic carbonate reservoir.

However, the systematic studies about reservoir characteristics of

pre-Cenozoic carbonate reservoir has limited. Stemming from the

urgent requirement of reality, I have chosen the name of thesis is:

"Reservoir characterization, geological modelling and hydrocarbon

potential of pre-Cenozoic carbonate, Northeast Song Hong Basin".

2. Tasks

- To clarify petrographic characteristics.

- Choosing the appropriate research methodology to build

geological modelling.

- Assess the hydrocarbon potential of prospects and ranking

them.

3. The object and scope of study

Object of study is pre-Cenozoic carbonate resrervoir at block

106, Northeast Song Hong Basin, shelf Viet Nam.

2

Scope of study including: the studies about lithology, age,

depositional enviroment, classification of rock and create porosity

modelling by artificial neural networks.

4. The content of study

- Collection, analysis document about stratigraphic, tectonic and

regional geology.

- Study about petrography of carbonate.

- Create the reservoir modelling.

- Use the results of thesis for study and exploration in the study

area.

5. Research methodology

To exploit the data and documents efficiently and achieve the

purpose of the research, the thesis uses a combination of the

following methods: cutting sample analysis; thin section analysis;

XRD analysis; SEM analysis; well log interpretation; seismic

attributes annalysis; Artificial Neural Networks.

6. The meaning of science and practice

6.1 The meaning of science

- To clarify petrography characteristics of pr-Cenozoic

carbonate reservoir in the study area.

- The thesis provides additional methodology, theory and

characteristics of carbonate rocks.

- Can be applied the methodology in thesis to study carbonate

rocks in other areas.

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6.2 The meaning of practice

- The petrography characteristic of carbonate was clarified,

would be to clarify the orientation of further research.

- Forward pland for exploration in this area will be strongly

supported based on the results of thesis.

7. Thesis protection

- The carbonate in the northeast Song Hong Basin has

lithological composition mainly calcite and dolomite, age from

carbon to permian, biochemical origin, mainly mudstone and

wackestone, depositional environment from low to medium power,

strongly diagenetic changes. The secondary porosity is the most

important in reservoir quality.

- Application of artificial neural network to build reservoir

modelling with the parameters input consists of 03 seismic attributes

RMS, Envelope, Sweetness and well log interpretation results is

consistent with carbonate in the northeast Song Hong basin. The

model allows assess the hydrocarbon potential of prospects and

ranking them.

8. New finding of the thesis

- The first time research issues about pre-Cenozoic carbonate in

Vietnam was studied systematically. The appropriate research

methodology to build geological modelling will be chosen based on

the results of petrography characteristics study.

- The thesis has provided the theoretical basis of carbonate

rocks, use 03 minerals model to make petrophysical intepretation,

choosing 03 appropriate seismic attributes to annalysis.

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- Age and depositional environment of carbonate were clarified,

assess the impact of diagenetic changes to reservoir quality.

- Assess the hydrocarbon potential of prospects and ranking

them.

10. The structure of thesis

The thesis consists of 132 typed pages including 06 tables and

64 figures. In addition to the introduction, conclusion and

recommendations and a list of references, including 04 chapters is

arranged as following:

- Chapter 1: including 36 pages with 02 tables and 11 figures

show the stratigraphic, tectonic, regional geology and

petroleum system of the northeast Song Hong Basin.

- Chapter 2: including 22 pages with 02 tables and 07 figures,

show the theoretical basis of carbonate rocks.

- Chapter 3: including 21 pages with 01 tables and 14 figures,

show the documents, data used and mothodology applied for

thesis.

- Chapter 4: 45 pages with 01 tables and 32 figures, show the

all results of research including petrography characteristics,

reservoir modelling, reservoir quality, prospect ranking and

discussion.

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Chapter 1 – THE GEOLOGICAL CHARACTERISTICS AND

PETROLEUM SYSTEM IN THE NORTHEAST SONG HONG BASIN

1.1 Location

The northeast Song Hong

Basin includes block 106 and

blocks 102, 103, 107 (Fig 1.1).

Located in the sea of Hai

Phong city, Nam Dinh

province, Thai Binh province,

Ninh Binh province and Thanh

Hoa province.

The area features

tropical monsoon climate of

northern Vietnam.

Fig 1.1The location of northeast

Song Hong basin

1.2 Exploration history

1.2.1 Seismic acquisition

2D, 3D seismic acquisition in this area was carried out early by

Petrovietnam and foreign companies with each other periods as

following: Petrovietnam (period 1978 – 1987), Total (period 1989 –

1991), Idemitsu (period 1993 – 1995), PCOSB (period 2003 – 2009),

PVEP (period 2009 - present).

Up to present (01/2015), the total the total volume of seismic

surveys in this area is 22 092 km 2D and 5330 km2 3D.

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1.2.2 Drilling

In the period 1989-2014 the contractor Total, Petronas,

Idemitsu, PVN and PVEP has drilled 20 exploration wells, including

11 wells on the mainly exploration target of sandstone in Miocene -

Oligocene and 9 wells on the mainly exploration target in pre-

Cenozoic carbonate. Typical discoveries include: Thai Binh gas

fields in Miocene sandstone; oil and gas condensate discoveries in the

pre-Cenozoic carbonate at Ham Rong, Ham Rong Dong, Ham Rong

Nam and gas discovery in the Miocene sandstone at Hac Long, Dia

Long, Hong Long.

1.3 Tectonic

Vietnam Petroleum Institute (2014) named 06 tectonic units in

the northeast Song Hong basin (Fig 1.3): (I) Quang Ninh Shelf; (II)

Paleoxen grabens; (III) Bach Long Vi Shelf; (IV) Miocene inversion;

(V) Western zone; (VI) Central Trough.

Fig 1.3: Map of tructural units (VPI, 2014)

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1.4 Stratigraphic and petroleum system.

The stratigraphic in the northeast Song Hong Basin is divided

into 02 sections are pre-Cenozoic basement and Cenozoic sediments.

Pre-Cenozoic basement consists of carbonate rocks, Paleozoic

terrigenous, metamorphic rocks. They were found in the exploration

wells. Cenozoic mainly conglomerate, sandstone, claystone and

silstone were deposited in lakes, deltas and marine environment.

Cenozoic is divided into 7 formations from the Eocene to Quaternary

including: Phu Tien, Dinh Cao, Phong Chau, Phu Cu, Tien Hung,

Vinh Bao and Hai Duong, Kien Xuong.

Petroleum system: mainly source rocks are Oligocene and

Miocene; reservoir include Oligoxen, Mioxen clastic and pre-

Cenozoic carbonate; seal is Oligoxen, Mioxen claystone; Traps are

mainly structural traps.

1.5. Tectonic history

Based on the analysis results from neck and neck specified

plant, Cocks and Torsvik (2013) suggest that in the early Paleozoic,

Southeast Asia is part of Gondwana, located at 300 south latitude

neck. The continental shelf of Vietnam located at 2 different plate:

The northern segment of south China plate (S.China), the southern

segment of Annamia plate.

The spreading and continental margin of Gondwana break

occurred in the early Ordovician, the microplate S.China and

Annamia separated from Gondwana, moving northward, Sibumasu

plate started moving southwards. This process is ongoing up to early

Devonian.

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In the late Devonian S.China plate and Annamia plate started

separated, this period highline the Paleotethys sea widely distributed

and grown to late Permian.

In the early Carbon, Sibumasu still attached to the northern

Australia and only separating by Phuket-Mergui and moving

northward. In the early Permian, S.China located on the equator and

gradually Annamia binding domain forming the East Asian continent

was covered by Paleotethys sea.

Tectonic activity is typical pre-Cenozoic orogenic cycle began

in the late Permian started for history of development in Mesozoic at

Southeast Asia.

Late Cretaceous to early Eocene, carbonate formations and old

rocks was lifted, weathered by the impaction between Sibumasu and

Vietnam China plate.

After the Eocene period, carbonate formations are covered by

subsidence and Cenozoic sediments become good traps for oil and

gas accumulated.

Oligocene and Miocene periods of tectonic activity continues to

occur include compression molding process for the creation of

inversion tectonics (late Oligocene) and phase 2 impiety in the

Miocene tectonic.

Oligocene and Miocene periods, the tectonic activity continues

include locally compression created tow phase inversion tectonics in

late Oligocene and Miocene .

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Chapter 2 – A GENERAL OVERVIEW OF CARBONATE

2.1 Definition and diagenesis

2.1.1 Definition

Carbonate rock are common in sedimentary rocks, the

chemical and biochemical. The most common is mainly limestone,

and then dolomite. Also carbonate rocks doping between carbonate

and non-carbonate component as clay, silica, mechanical debris.

2.1.2 Diagenesis

Three common rules in the diageneis of carbonate rocks as

following:

- Carbonate material sediments with large amounts of organic

origin.

- The reef is that part of a carbonate rock created by essentially

in-place.

- The changes of carbonate after diagenesis is very strong.

2.2 Classification of carbonate rock

2.2.1 Dunham classification

The classification is a way of describing the composition of

calcareous rocks in hand sample. For descriptions detailing the

textural components of sediments and sedimentary rocks, Dunham

(1962) named 06 diffirents rocks include: mudstone, wackestone,

packstone, grainstone, boundstone and crystalline. Fig 2.2 show

Dunham classification.

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Fig 2.2. Dunham classification (1962);

Modified by Embry và Klovan (1971)

2.2.2 Classification by depositional environment

The classification of Loucks (1993) and Bosscher (1992) is

used widely in oil and gas industrial, include: basin carbonate, slope

carbonate, platform carbonate, platform interior carbonate, patch reef

carbonate and tidal flat carbonate (Fig 2.3).

Fig 2.3 Classification of Loucks (1993), and Bosscher (1992)

Embry and Klovan (1971)

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2.3 Changes of carbonate after diagenesis

There are 04 mainly changes of carbonate after diagenesis,

which very important when evaluate reservoir quality, include:

solution, cimentation, dolomitization and stylolittization.

Jones and Xiao (2005) created the model relationship between

the dolomitization and porosity. The dolomitization can increase or

decrease the porosity in carbonate rocks depending on the each

periods, (Fig 2.4).

Fig 2.4 Relationship between the dolomitization and porosity

2.4 Characteristics of carbonate on geophysical

2.4.1 Characteristics on seismic

Velocity in carbonate rocks generally faster than in clastic at the

same depth. High velocity and high density of carbonate rocks would

result in a higher impedance than clastic, thereby creating a high

reflection coefficient at the boundary between clastic and carbonate

rocks.

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2.4.2 Characteristics on well log data

There are 05 physical characteristics of carbonate rock,

including: high bulk density, high transmission speed, low

gammaray, high resistivity, low hydrogen index. Table 2.2 presents

the physical characteristics of carbonate rocks and some other rocks.

Talbe 2.2: The physical characteristics of rocks

Density

(g/cm3)

Sonic

(ms.ft)

Gamaray

(API)

Resistivity

(Ohm.m)PE

Limestone 2.71 - 2.78 40-50 10-20 30 - thousands 5.08

Dolomite 2.71-2.78 40-50 10-20 30 - thousands 3.14

Sandstone 2.65-2.68 55-60 15-30 1.1 - 6 1.81

Claystone 2.2 - 2.7 50-150 100-150 1.1-3 1-5

Granite 2.71 - 2.75 45 - 55 35 - 50 50 - thousands 5

Rocks

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Chapter 3- DOCUMENTS AND RESEARCH METHODOLOGY

3.1. Document

The document used for research include:

- Seismic: 350 km2 3D seismic.

- well data: including data of 04 wells in the study area and 04

wells nearby as offset data.

- Samples: totally 280 cutting samples and 48 side wall core of

106-HR-2X, 106-HRN-1X and 106-HRD-1X well.

- The regional geology documents: Final well reports, block

evaluation report.

3.2 Methodology

The thesis uses a combination of methods including: cuttings

analysis, thin section analysis; X-Ray; SEM; well log interpretation;

seismic attributes analysis; Artificial neural networks. The study

workflow as show on Fig 3.14.

Fig 3.14 petrographic and reservoir modellinging study workflow

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Chapter 4- PETROGRAPHIC CHARACTERISTICS AND

GEOLOGICAL MODELLING

4.1 Petrographic characteristics

4.1.1. Lithological composition

The results of cutting analysis and X-ray show that mainly

lithology are calcite and dolomite. These results is high reliability,

can be integrated with well log data to conduct interpretation.

- X-Ray (XRD) results: performed on 48 samples including 20

samples from well 106-HRN-1X, 14 samples from well 106-HR-2X

and 14 samples from well 106-HRD -1X. Results showed that three

major minerals are present in most samples include calcite (0.0% -

99.3%, average 43.4%); dolomite (0.0% - 92.5%, average 35.7% )

and quartz (0.0% - 81.3%, average 11.4%). The other mineral from

0.0% to a few percent include: K-feldspar, plagioclase, pyrite,

laumontite (average 0.6%); analcime (average 1%); clay minerals,

kaolinite, chlorite, aragonite, geothite 0.5% - 1.5.

- Cuttings analysis: performed on 280 samples, two major

minarals identified are calcilte and dolomite, quartz appeared in some

samples.

Calcite: 40-60%, with light gray to white milk, blocky

carbonate, hard to very hard, brittle; light to light; streak is white,

translucent to transparent; bluk density from 2.75 to 2.81 g/cm3;

maybe emitting red, green, yellow and other colors under short-wave

radiation; soluble in HCl.

Dolomite: 30-50%, with gray to brown, blockylike calcite; very

hard, bulk density from 2.78 to 2.81 g/cm3; It can be white to red

15

fluorescence under ultraviolet light; luminescence due to friction,

insloluble in HCl.

4.1.2 Age and depositional environment

Hall & Wilson (2011) have studied and give a summary of the

characteristics of rocks for each period for 6 microarray of Southeast

Asia. According to the results of this study Fusuline petrify

(Foraminifera) only appears in the period from Carbon to Permian in

the Sibumasu, Indochina and South China plates.

On side wall cores from wells 106-HRN-1X, 106-HRD-1X

indentified many Fusuline petrifies (Fig 4.7), this result allows us to

indentify carbonate of study area has age from Carbon to Permian.

This carbonate was deposited in an environment with energy levels

from low to moderate, less affected by tidal and wave.

Fig 4.7 Fusuline petrify from SWC: well 106-HRN-1X (Depth

3580m, 3618m, 4115m, 4120m, 4125m), well 106 – HR-2X (Depth

3782m)

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4.1.3 Classification of rocks

According to Dunham classification, carbonate in the study area

is all most mudstone, wackestone and a little of packstone. The detail

descreption as following and Fig 4.8:

- Mudstone and wackestone:

Mudstone and wackestone appeared in most of samples,

characterized by mud supported with component from 90% to 100%,

grain from few to 10%.

- Packstone:

Packstone identified on 02 samples at 3580m and 3821m depth

106-HRN-1X well, characterized by grain supported with compoent

up to 80%.

Fig 4.8 Classification of rocks: (A) mudstone at 106-HR-2X (3508m),

106-HRN-1X (3618m); (B) wackestone at 106-HRN-1X (3480m),

106-HRD-1X (3815m); (C) packestone at 106-HRD-1X (3580m,

3821m).

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4.1.4 Changes of carbonate after diagenesis

There are 04

mainly changes of

carbonate after

diagenesis include:

solution,

cimentation,

dolomitization and

stylolittization

(Fig 4.11).

Fig 4.11 change of carbonate

Uses the 2

porosity model to log

analyze have

identified phi matrix

and secondary

porosity. As the

result allow identify

the secondary

porosity have a

positive impact on

the reservoir quality

(Fig 4.12).

Fig 4.12 log interpretation result

The results of the well log interpretation are shown in Figure

4.12 showing of secondary porosity is a major in most wells.

Đường khâu

Nứt nẻ

Calcite tái kết tinh

Xi măng hóa

HRN-1X/3515m HR-2X/3622m

HRD-1X/3842m HR-2X/3700m

dolomite

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4.2. Geological modelling

4.2.1. Reservoir characteristics

4.2.1.2 Petrophysical result

The lithology, primary porosity and secondary porosity were

identified by using 03 minerals and two porosity modelling.

According to the results, secondary porosity have a positive impact

on the reservoir quality with 1% to 8%, the total effective porosity

approximately up to 20%.

Figure 4.17 presents the results of total effective porosity. The

results showed that the total effective porosity of 106-HR-2X and

106-HRN-1X well larger than 106-HRD-1X well.

Fig 4.17 Petrohysical interpretation

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4.2.2 Seismic attribute analysis result

The results of seismic attributes RMS, Envelope and Sweetness,

showed the similarity together, reflecting the change in the porosity

and used to artificial neural networks.

Hình 4.20 Seismic attributes analysis result

4.2.3. Porosity modelling from ANN

4.2.3.1 Porosity modelling

The total effective porosity from wells 106-HR-2X, 106-HRN-

1X, 106-HRD-1X and 03 seismic attributes RMS, Envelope,

Sweetness are used as parameter input for artificial neural networks

to build porosity (Fig 4.24).

EnvelopeRMS

Sweetness

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The porosity

from model will

accommodate from

seismic attributes

and tend to follow

the distribution of

porosity from well

log interpretation

(Fig 4.25).

Fig 4.24 Porosity model workflow

Fig 4.25 Porosity model

4.2.3.2 Reliability assessment of the model

To assess reliability of the model, we compare the effective

porosity from porosity model and the effective porosity from well log

interpretation at each well. Based on the correlation coefficient (R2)

Top cacbonat 40 ms fromTop cacbonat

55 ms fromTop cacbonat 300 ms fromTop cacbonat

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to assess the reliability of the model. The result of R2 as following:

well 106-HR-2X, R2 = 0,88; well 106-HRN-1X, R

2 = 0,84; well

106-HRD-1X, R2 = 0,92. This results allow assessment the porosity

model have high reliability.

4.2.4 Reservoir quality of prospects

Up to the present, the study area have totally 07 prospects, in

which 03 prospects drilled, named Ham Rong, Ham Rong Nam,

Ham Rong Dong and 04 prospects still undrilled, named A, B, C, D

(Fig 4.28).

Fig 4.28 Prospect distribution on the structure map

Hàm Rồng

Hàm Rồng Nam

Hàm Rồng Đông

A

B

C

D

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Table 4.11 showed the reservoir quality and ranking of

prospect. According to the result, Ham Rong Nam prospect is the

best of reservoir quality and then is A, Ham Rong, B, C, D. The

bottom of ranking is Ham Rong Dong prospect.

Table 4.1 Reservoir quality and ranking of prospects

No ProspectTop

(mTVDss)

Spill

point

(mTVDss)

Relief

(m)

Area

(x106 m2)

Volume

(BRV)

(x106m3)

NPV

(x106m3)

Phie

(Frac)Ranking

1 Ham Rong Nam* 3390 3800 410 12.5 3080 200.2 0.065 1

2 A 3450 3900 450 8.25 2230 122.7 0.055 2

3 Ham Rong* 3380 3925 545 9.5 3110 155.5 0.05 3

4 B 3750 4100 350 4.5 950 42.8 0.045 4

5 C 3450 3800 350 4.8 1010 45.5 0.045 5

6 D 3750 4125 375 8.6 2580 77.4 0.03 6

7 Ham Rong Dong* 3680 4000 320 18 3460 86.5 0.025 7

*: Prospect was drilled

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CONCLUSION

With these results of thesis, some of the main conclusions about

petroleum system characteristics, petrographic and geological model

of pre-Cenozoic carbonate Northeast Song Hong Basin as follows:

1. The northeast Song Hong Basin has complex geology,

petroleum system has been proven, exploration object including

oil and gas, reservoir include Miocene, Oligocene sandstone

and pre-Cenozoic carbonate basement. Carbonate rocks under

Cenozoic sedimentary has many similarities with carbonate on

the surface.

2. The carbonate in the northeast Song Hong Basin has

lithological composition mainly calcite and dolomite, age from

carbon to permian, biochemical origin, mainly mudstone and

wackestone, depositional environment from low to medium

power, strongly diagenetic changes. The secondary porosity is

the most important in reservoir quality.

3. Porosity from model consist with porosity from well log

interpretation, the correlation coefficient (R2) as following: well

106-HR-2X, R2 = 0,88; well 106-HRN-1X, R

2 = 0,84; well

106-HRD-1X, R2 = 0,92. This results allow assessment the

porosity model have high reliability.

4. According to the model, Ham Rong Nam prospect is the best of

reservoir quality and then is A, Ham Rong, B, C, D. The bottom

of ranking is Ham Rong Dong prospect.

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RECOMENDATIONS

1. Using the results of this thesis to study the facies characteristics of

carbonate northeast Song Hong basin. It is possible to apply the

methodology of the thesis to study the characteristics of pre-

Cenozoic carbonate nearby the study areas.

2. For Ham Rong oil field, the appraisal and development wells

should designed in the west of struture; for Ham Rong Dong

prospect, should be done hydraulic fracturing for DST because of

low porosity and low permeability; for Ham Rong Nam prospect,

due to very good reservoir quality, so the system of production

well will be appropriately designed.

3. In the four remaining prospects in the study area, prospect A is the

best and can be considered for next exploration well.

LIST OF SCIENTIFIC WORKS RELATED TO THE THESIS

1. Le Trung Tam, Cu Minh Hoang, Pham Van Tuan (2014),

“Petrographic characteristics of pre-Cenozoic carbonate in Ham

Rong field”, Oil and Gas Journal no5, p.23-30.

2. Le Trung Tam, Nguyen Van Phon, Nguyen Xuan Phong, Ta Xuan

Tien, Chu Phuong Long (2014), “The effect of dolomitization on

porosity in fractured carbonate resrvoir, Ham Rong oil field”, The

science conference 21th, Ha Noi University of Mining and Geology.

3. Nguyen Van Hoang, Le Quang Vu, Bui Van Cuong, Le Trung Tam

(2013). “A Study of Carbonate Reservoir Characteriazation By

Petrophysical Data In Block 102-106, Song Hong Basin”,

Petrovietnam International Technical Forum – Challenging

Reservoirs in Vietnam.

4. Le Trung Tam, Cu Minh Hoang (2013) “Major cause of low

resistivity and a model to calculate hydrocarbon saturation in the

turbidite pay sands of Song Hong basin”, Oil and Gas Journal

no8, p.19-24.

5. Le Trung Tam, Nguyen Quang Viet, Nguyen Van Hoang, Nguyen

Thi Tra Giang, “Sediment characteristics and geological history of

Truong Sa area”, Oil and Gas Journal no2, p.15-21.

6. Kieu Nguyen Binh, Tran Nhu Huy, Le Trung Tam (2011).

“Seismic while drilling and drilling optimization”, The

conference of science and technology 12th

, Ho Chi Minh City

University of Technology, p1-6.