Eocene to Miocene Composite Total 

Petroleum System, Irrawaddy-Andaman 

and North Burma Geologic Provinces, 

Myanmar

By C.J. Wandrey

Petroleum Systems and Related Geologic Studies in Region 8,

South Asia

Edited by Craig J. Wandrey

U.S. Geological Survey Bulletin 2208–E

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia: 2006

Posted online February 2006

Version 1.0

This publication is only available online at

http://www.usgs.gov/bul/2208/E/

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, 

natural hazards, and the environment:

World Wide Web: http://www.usgs.gov

Telephone: 1-888-ASK-USGS

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Wandrey, C.J., 2006, Eocene to Miocene Composite Total Petroleum System, Irrawaddy-Andaman and North Burma 

Geologic Provinces, Myanmar, Chapter E in Wandrey, C.J., ed., Petroleum systems and related geologic studies in 

Region 8, South Asia: U.S. Geological Survey Bulletin 2208-E, 26 p. 
iii

Foreword

This report describing the petroleum resources within a total petroleum system in Myanmar was prepared as part of the World Energy Assessment Project of the U.S. Geological 

Survey. For this project, the world was divided into 8 regions and 937 geologic provinces, 

which were then ranked according to the discovered oil and gas volumes within each (Klett and 

others, 1997). Of these, 76 “priority” provinces (exclusive of the United States and chosen for 

their high ranking) and 26 “boutique” provinces (exclusive of the United States and chosen for 

their anticipated petroleum richness or special regional economic importance) were selected 

for assessment of oil and gas resources. The petroleum geology of these priority and boutique 

provinces is described in this series of reports.

The purpose of the World Energy Project is to assess the quantities of oil, gas, and natural 

gas liquids that have the potential to be added to reserves within the next 30 years. These 

volumes either reside in undiscovered fields whose sizes exceed the stated minimum-fieldsize cutoff value for the assessment unit (variable, but must be at least 1 million barrels of oil 

equivalent) or occur as reserve growth of fields already discovered.

The total petroleum system constitutes the basic geologic unit of the oil and gas assessment. The total petroleum system includes all genetically related petroleum that occurs in 

shows and accumulations (discovered and undiscovered) and that (1) has been generated by a 

pod or by closely related pods of mature source rock, and (2) exists within a limited mappable geologic space, along with the other essential, mappable geologic elements (reservoir, 

seal, and overburden rocks) that control the fundamental processes of generation, expulsion, 

migration, entrapment, and preservation of petroleum. The minimum petroleum system is 

that part of a total petroleum system encompassing discovered shows and accumulations 

along with the geologic space in which the various essential elements have been proved by 

these discoveries.

An assessment unit is a mappable part of a total petroleum system in which discovered and undiscovered fields constitute a single, relatively homogeneous population such 

that the chosen methodology of resource assessment based on estimation of the number and 

sizes of undiscovered fields is applicable. A total petroleum system may equate to a single 

assessment unit, or it may be subdivided into two or more assessment units if each unit is 

sufficiently homogeneous in terms of geology, exploration considerations, and risk to assess 

individually.

A graphical depiction of the elements of a total petroleum system is provided in the form 

of an events chart that shows the times of (1) deposition of essential rock units; (2) trap formation; (3) generation, migration, and accumulation of hydrocarbons; and (4) preservation of 

hydrocarbons.

A numeric code identifies each region, province, total petroleum system, and assessment 

unit; these codes are uniform throughout the project and will identify the same type of entity in 

any of the publications. The code is as follows: 

Example

Region, single digit 2

Province, three digits to the right of region code 2004

Total Petroleum System, two digits to the right of province code 200401

Assessment Unit, two digits to the right of petroleum system code 20040101

The codes for the regions and provinces are listed in Klett and others (1997).

Oil and gas reserves quoted in this report are derived from Petroconsultants’ Petroleum 

Exploration and Production database (Petroconsultants, 1996) and other area reports from 

Petroconsultants, Inc., unless otherwise noted.
iv

Figures in this report that show boundaries of the total petroleum system(s), assessment 

units, and pods of active source rocks were compiled using geographic information system 

(GIS) software. Political boundaries and cartographic representations were taken, with permission, from Environmental Systems Research Institute’s ArcWorld 1:3 million digital coverage 

(1992), have no political significance, and are displayed for general reference only. Oil and gas 

field centerpoints shown on these figures are reproduced, with permission, from Petroconsultants (1996).
v

Contents

Foreword ........................................................................................................................................................iii

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................2

Acknowledgments.........................................................................................................................................2

Geologic and Tectonic History.....................................................................................................................2

Stratigraphy ....................................................................................................................................................9

Exploration and Production........................................................................................................................11

Total Petroleum System..............................................................................................................................17

Source Rocks.......................................................................................................................................17

Source Rock Richness..............................................................................................................18

Maturation...................................................................................................................................18

Generation and Migration .................................................................................................................18

Reservoir Rocks ..................................................................................................................................18

Traps and Seals...................................................................................................................................19

Assessment Units ........................................................................................................................................19

Cumulative Production Data ......................................................................................................................22

Assessment Comparisons..........................................................................................................................22

Summary........................................................................................................................................................22

Selected References...................................................................................................................................24

Figures

1–3. Maps showing:

 1. Location of Irrawaddy-Andaman (8048) and North Burma (8035)

geologic provinces................................................................................................................3

 2. Geologic province and total petroleum system boundaries ..........................................4

 3. Generalized geology and geologic province boundaries ...............................................5

4. Tectonic map of Myanmar and Andaman Basin .....................................................................6

5. Generalized stratigraphic column of Central Burma Basin, Myanmar................................7

6–11. Paleogeographic maps from perspective of study region, showing:

 6. Middle Jurassic (approximately 166 Ma)..........................................................................8

 7. Early Cretaceous (approximately 130 Ma) ........................................................................9

 8. Late Cretaceous (approximately 94 Ma)..........................................................................10

 9. Latest Cretaceous (approximately 69 Ma) ......................................................................11

 10. Middle Eocene (approximately 50 Ma)............................................................................12

 11. Late Oligocene (approximately 27 Ma)............................................................................13

12. Maps showing generalized early and late Eocene paleogeography and

associated cross sections ........................................................................................................14

13. Maps showing generalized early Miocene and Pliocene paleogeography and

recent cross section ..................................................................................................................15

14. Map showing generalized geology and some oil and gas fields........................................16
vi

15–19. Graphs of data for the Irrawaddy-Andaman geologic province, showing:

 15. Cumulative number of new-field wildcat wells versus completion year...................17

 16. Known oil and gas field sizes grouped in thirds by discovery date and

ranked by size ......................................................................................................................18

 17. Cumulative number of oil and gas fields versus discovery year.................................19

 18. Cumulative known (cumulative production plus reserves) oil and gas volumes

versus discovery year.........................................................................................................20

 19. Reservoir depth versus field discovery year for oil and gas........................................21

20. Diagram showing mean vitrinite reflectance of rock samples in Gulf of Martaban .......22

21. Pie diagram showing temporal distribution of producing reservoirs by

youngest age ...............................................................................................................................22

22. Pie diagram showing distribution of trap type.......................................................................24

23. Events chart summarizing stratigraphy, source rocks, reservoirs, seals, traps,

timing, and petroleum information for the Eocene to Miocene Composite Total 

Petroleum System.......................................................................................................................24

Table

1. USGS estimates of undiscovered oil and gas resources by assessment unit and 

aggregated for the total petroleum system (Wandrey and others, 2000)..........................23
Abstract

The Eocene-Miocene Composite Total Petroleum System 

(804801) was divided into two units for the purpose of assessment, the Central Burma Basin Assessment Unit (80480101) 

and Irrawaddy-Andaman (80480102) Assessment Unit.

 The Irrawaddy-Andaman (80480102) Assessment 

Unit is located in the southern central basin of Myanmar, 

the Irrawaddy Delta, and Andaman Basin. It is a gas-prone 

onshore and offshore basin developed subparallel to the converging continental and marine plate boundaries. The rocks 

that compose this assessment unit include Eocene sandstones 

and shales and the Oligocene-Miocene Pegu Group, which in 

places exceeds 6,500 meters in thickness. This group is made 

up of interbedded, shallow marine shales, limestones, and 

sandstones, and the sandstones, shales, and coals of deltaic 

and lagoonal facies. 

Source rocks include the lower Oligocene shales of the 

Yaw, Shwezetaw, and Okhmintaung Formations and shales of 

the Pegu Group. Total organic carbon percent is generally low 

(<1.75 percent) where sampled. Organic material is primarily 

terrestrially derived type III kerogen. Maturities are generally 

low, from R0 0.2 to 1.5 percent where sampled in the Gulf of 

Martaban. Maturities are likely higher in areas of the basin 

where burial depths are greater.

Significant generation commenced during the Pliocene. 

Migration is primarily vertical through fault and fracture systems associated with the plate collision. These fault systems 

have been periodically reactivated through the present. Short 

updip migration along the flanks of the basin is also likely.

Primary reservoir rocks are interbedded sandstones of the 

Pegu Group. Permeability ranges from less than 32 millidarcies (mD) to as high as 3,200 mD. Porosity ranges from less 

than 20 percent to 30 percent. Reservoir quality is fracture 

enhanced in many cases.

Traps include anticlines, faulted anticlines, and a few 

stratigraphic traps. Seals include interbedded Oligocene 

and Miocene shales and clays, and the thick clays of the 

upper Miocene−Pliocene Irrawaddy Group. Although few 

stratigraphic traps have been discovered, potential for more 

discoveries exists in the deltaic sequences. There is also potential for growth-fault related traps and in the offshore fans.

The Central Burma Basin Assessment Unit (80480101) 

is located in the north and central basins of Myanmar. It is an 

oil-prone onshore basin developed parallel to the converging 

continental and marine plate boundaries. The rocks that compose this assessment unit include the Eocene Laungshe Shale, 

Tilin and Pondaung Sandstones, and the Oligocene-Miocene 

Pegu Group, the thickness of which exceeds 6,500 meters. 

This group includes interbedded sandstones, shales, and coals 

of deltaic to fluvial facies, and shallow marine shales, limestones, and sandstones. 

Source rocks include the upper Eocene–lower Oligocene 

shales of the Yaw, Shwezetaw, and Okhmintaung Formations. 

Total organic content is generally low where sampled (>1.7 

percent). Organic content is primarily terrestrially sourced 

type III kerogens. Maturities are generally low, from R0 0.2 

to 1.5 percent where sampled outside of this assessment unit 

to the south in the Gulf of Martaban. The onset of generation 

probably occurred in late Miocene. Migration is primarily

short updip and vertical through fault and fracture systems 

associated with the plate collision. These fault systems have 

been periodically reactivated through the present.

Interbedded sandstones of the Pegu Group are the primary reservoirs. Permeability ranges from less than 32 mD 

to as high as 3,200 mD. Porosity ranges from less than 20 

percent to 30 percent. The Eocene Pondaung and Tilin sandstones may also have reservoir potential and have a combined 

thickness of as much as 3,500 meters, including the interbedded shales.

Traps include anticlines, faulted anticlines, fault truncations, and stratigraphic traps. Seals include interbedded Oligocene and Miocene shales and clays, and the thick clays of 

the upper Miocene and Pliocene Irrawaddy Group. Structures 

in the Chindwin Basin area and stratigraphic traps developed 

in alluvial and deltaic systems have been only lightly explored 

and may have significant potential.

Eocene to Miocene Composite Total Petroleum System, 

Irrawaddy-Andaman and North Burma Geologic 

Provinces, Myanmar

By C.J. Wandrey
Introduction

Among the 26 boutique provinces identified for the U.S. 

Geological Survey World Energy Assessment (2000) was the 

Irrawaddy-Andaman geologic province (8048) (fig. 1). The 

Eocene to Miocene Composite Total Petroleum System (TPS) 

(804801) (fig. 2), as defined for this assessment, extends north 

and also encompasses most of the North Burma geologic province (8035); therefore, that province is also included in this 

report. Located in central Myanmar, Gulf of Martaban, and 

the Andaman Sea, it is an onshore and offshore TPS covering 

approximately 800,000 km2 (fig. 3).

The North Burma and Irrawaddy-Andaman geologic 

provinces are bounded on the north and west by the IndoBurman and Arakan Yoma Mountain Ranges and on the east 

by the Sino-Burman Ranges, Shan Plateau, and Tenasserim 

Ranges. The area includes the Chindwin Basin, Salin Basin, 

Prome Embayment, Irrawaddy River Delta, Gulf of Martaban, and the Andaman Sea east of the Andaman Islands. The 

area described is essentially a complex back-arc/fore-arc 

basin (fig. 4), with portions of, or the entire onshore part 

being variously referred to as, the Central Basin, Central 

Burma Basin, Inner or Central Burma Tertiary Basin, and 

Central Burma Tertiary Geosyncline. In this report the entire 

onshore part will be referred to by the most commonly used 

term—the Central Burma Basin.

In the Central Burma Basin, the Cretaceous Kabaw 

Group (fig. 5) or younger rocks rest on the marine basement 

in the western basin and on continental basement rocks in 

the eastern basin. In the ranges to the west, sedimentary and 

metamorphic rocks as old as Early Triassic have been identified. East of the Central Burma Basin, rocks younger than 

Cretaceous were not deposited or were almost completely 

removed by erosion, leaving a nearly continuous stratigraphic section from Cambrian to Lower Cretaceous. The 

offshore portion of the TPS consists of Eocene and younger 

rocks (Curray and others, 1979; Pivnik and others, 1998). 

Structurally, the TPS consists of a north-south-trending 

trough or fore-arc/back-arc basin that developed as a result of 

Eocene oblique multi-plate collision.

The Eocene-Miocene Composite TPS was further divided 

into two assessment units (AU) (fig. 2). These AUs are the 

Irrawaddy-Andaman AU (80480102) and the Central Burma 

Basin AU (80480101). The Irrawaddy-Andaman AU is located 

in the southern part of the Central Burma Basin of Myanmar, 

the Irrawaddy Delta and Andaman Basin. It is a gas-prone 

basin, developed both on and offshore subparallel to the converging continental and marine plate boundaries. The Central 

Burma Basin AU is located in the northern and central part 

of the Central Burma Basin of Myanmar. It is an oil-prone, 

onshore area, and it also developed parallel to the converging 

continental and marine plate boundaries.

Acknowledgments

The author thanks Hugh Balkwell and technical reviewers 

D.K. Higley and R.R. Charpentier for their valuable suggestions and insight.

Geologic and Tectonic History

The total petroleum system (TPS) and assessment units 

(AU) discussed herein owe their primary structural and stratigraphic features to a series of plate tectonic events dating from 

latest Paleozoic time to the present. The continental plates that 

were involved in the development of present-day Myanmar are 

the Indian and Eurasian plates and the Burma or Sunda microplate or fore-arc sliver. The Burma plate has been described 

as a micro-plate or fore-arc sliver bounded on the west by a 

subduction zone, on the east by a strike-slip fault, on the south 

by a spreading center, and on the north by a compressional 

plate boundary (Curray and others, 1979; Pivnik and others, 

1998). This sliver or micro-plate has also been described as 

an accretionary prism that consists of sedimentary, meta-sedimentary, intrusive, and volcanic rocks (Curray and others, 

1979; Bender, 1983) (fig. 4). Studies of the eastern part of the 

Indian plate suggest alternatively that the Burma plate may 

have been located north of the Indian plate prior to collision, 

and then underwent extrusion and 90° of clockwise rotation to 

reach its present position (Tapponnier and others, 1982; Besse 

and Courtillot, 1984; LeDain and others, 1984; Everett and 

others, 1990). Lee and Lawver (1995) and Pivnik and others 

(1998) suggested that the Burma plate originated as a part of 

the early Tertiary continental shelf of southeast Asia located 

southeast of its present location.

From Permian through Middle Jurassic time, the Eurasian 

plate (or plates) and probably the Burma plate extended just 

south of the equator. The Indian plate was located farther to 

the southwest, between the African, Antarctic, and Australian 

plates, making up part of southern Gondwana (fig. 6). During 

the Late Jurassic and Early Cretaceous, Southeast Asia and the 

area of the Burma plate moved northward across the equator to 

between lat 10° and 20° N.

During the Cretaceous, the Indian plate continued to drift 

northward toward the Burma and Eurasian plates (figs. 7 and 

8), and by latest Cretaceous time the sea floor of the Bengal 

Basin began to form (Scotese and others, 1988). Along the 

Ninety East Ridge a transform fault became active (fig. 9), 

and in the Assam area, a southeasterly dipping block-faulted 

shelf developed. Counterclockwise rotation of the Indian plate 

began, and the western part of the Indian plate that is now the 

Seychelles began to break away from the Indian plate (Waples 

and Hegarty, 1999) (fig. 9). During Paleocene time, oceanic 

plate subduction occurred along the west edge of the Burma 

 Petroleum Systems and Related Geologic Studies in Region 8, South Asia
8003

8042

8025

8024

8001

8023

8022

8021

8026 8002

8028

8043

8063

8062

8061

8004

8044

8045

8033

8030

8031 8032

8046

8047

8034 8035

8006

8048

8005

Irrawaddy- Andaman

North Burma

8001 S8002 H8003 I8004 S8005 I8006 T8021 M8022 B8023 C8024 A8025 S8026 K8028 H8030 C8031 S8032 D8033 P8034 A8035 N8042 I8043 B8044 C8045 K8046 M8047 G8048 I8061 M8062 L8063 K

Arabian

Sea

Region 2

Region 1

Region 3

Indian

Ocean

Bay

of Bengal

60°E 70°E 80°E

10°0°20°30°40°

90°E 100°E

Figure 1. Location of Irrawaddy-Andaman (8048)and North Burma (8035) geologic provinces shown in green; other assessed provinces in regio
ÚÊ

INDEX MAP

Mandalay

Rangoon

EXPLANATION

Indian

 Ocean

Eocene to Miocene Composite Total Petroleum System 804801

Irrawaddy Province 8048

Other province boundary

Irrawaddy-Andaman Assessment Unit 80480102

Central Burma Basin Assessment Unit 80480101

Gas field

Oil field

8035

8048

People’s

Republic

of

China

0 500 1,000 KILOMETERS

10°

15°

20°

25°

85°E 90°E 95°E 100°E 105°E

Myanmar

Thailand

India

Bangladesh

Figure 2. Geologic province and total petroleum system boundaries.

 Petroleum Systems and Related Geologic Studies in Region 8, South Asia
Arakan Yoma 

Indo-Burman Ranges 

Assam 

Andaman Islands 

Tenasserim Ranges 

Chindwin Basin 

Salin Basin 

Prome Embayment 

Pegu Yoma 

Shwebo Basin 

MzPz 

Ts 

N 

Pg 

dms 

Q

Pzl

Pg 

Pg 

N 

Ts 

TrCs 

Pzi 

TrCs 

Pzu

Osm

Mzim Osm

Pz

Mzim 

Pz Pzu 

Pzu Mzim EXPLANATION Mzim Mzim 

pe Trms 

Pzu Cs dms MzPz 

MzPz 

Pr Geologic province boundary Pzu Mzim Q Pr 

Ts pe Trms Geologic contact Trms Pr Jd Ts JTr Evident fault pe

Mzim N Jd Pr

Pz PrTrms 

MzPz Pz Trms Inferred fault Pzu N Jms 

pe Ts River MzPz pe Trms 

Ti Mzim Pr

Q Pz pe

Ts TKim Cs

Trms 

Water depth contour Pz Pr MzPz Osm 

Ts N OsmPr Osm

Pr Q - Quaternary sediments pe MzPz 

pe MzPz 

pe CsPr pe N Cs N India Pg N pe Q N - Neogene sedimentary rocks Ts Pr 

pe Ts 

Q Pg Pg 

pe Q Cmsm 

Cs 

Pg - Paleogene sedimentary rocks pe Ts Pg pe Osm 

pe N N 

T

T

s 

s N Tv 

People’s Ts - Tertiary sedimentary rocks pe TKimTs Ts 

Pg Pg Pg Ts Pg Ti Q Mzim Republic of Ti - Tertiary igneous rocks

N Pg Ks 

Ts Q 

Ts Mzim 

China Tv - Tertiary volcanic rocks pe TKim

Q N 

Ts TKim - Tertiary and Cretaceous igneous and metamorphic rocks N Pr 

Trms Pz N Pr Q Tv Ts Q Q S 

Pr S Mzim - Mesozoic intrusive and metamorphic rocks Pr 

Bangladesh Q Pz 

Ks Pr

N Pz Ks - Cretaceous sedimentary rocks Q 

pe Jms dms Jms - Jurassic metamorphic and sedimentary rocks Pg Cs 

Pr Cs 

Jms Jms Jd- Jurassic and Triassic rocks CsCs 

Q 

Q 

Pg 

Pg Pzl

Jms 

N 

Pzl Pzu JmsTs dms - Triassic metamorphic and sedimentary rocks

Pg Pzl N Q 

N MzPz - Mesozoic and Paleozoic undivided N pe

Pzu Ti 

N dCs - Lower Triassic to Upper Carboniferous rocks Q Pzl Mzim 

Q Mzim 

Jms Cs Pzl 

Pg Q Q Pz- Paleozoic rocks N pe Pzu Cs Q Pzu pe

Mandalay pe

Pg Jms Pzu Pz 

Cs Pzu - Upper Paleozoic rocks Ts 

Pz N 

QQ Q Pg Ks Pg pe

Q N Pzl Pzu Pzi Pzl - Lower Paleozoic rocks Shan Q 

N Q Pzu Pzi Q 

Q pe pe Pzi Pr TrPr Pzi - Paleozoic igneous rocks Plateau S Q pe Ts Jms Mt Popa Q MzimTrms 

Q Tv Cs - Carboniferous sedimentary rocks Jms Cs 

S

TsMzim 

Jms Pz 

Jms Pr S - Undivided Silurian rocks N N pe Pzi 

Q Pr 

Pr S 

Pr Osm - Ordovician sedimentary and metamorphic rocks N TKim

pe TKim S TKim 

S

Pzl emsm - Cambrian sedimentary and metamorphic rocks Myanmar Pg N N pe pe - Undivided Precambrian rocks 

I - Undivided igneous rocks 

N pe

Bay Surface water 

Unmapped area 

Pg Pg

of Ks

N 

Q

Bengal N

pe Thailand 

Pg 

Q

Yangoon Q Pzu 0 500 1,000 

S 

N Q Q Pzu 

Gulf S

of Pzl KILOMETERS 

Irrawaddy Martaban Pzl 

Ti S 

Jms 

N Delta Ti 

Figure 3. Generalized geology and geologic province boundaries Q (Wandrey and Law, 1999). Ti 

N

Ti Q I Ti

Pzl

Pg Ti

Pzl

Pzl

Pzl

Pg

Ks Q Pzl

Pzl Ti

Ts Pg 

Pg 

Ks 

Ks 

Ks 

Pzl Andaman Pzl

Pzl

Sea Cs Pzl

Pz

Pzl

Pzl Pz

Pg Pzl Pzl

Q 

Pzl 

Ti 

Pg 
Ninety East Ridge

^

^

^ ^

^ ^

^ ^ ^ ^

^

^

^

^

^

^

^

^

^

^

^

| | | | | | | | | | | | | | | |

^

^

UPPER

ASSAM

S

h

a

n

P

l

a

t

e

a

u

Ganges Delta

l l l l

^

^

96°E

0 100 500 KM

24°

16°

8°

Gulf of 

Thailand

Andaman

 Sea

 Gulf of

Martaban

^

^

^

Bay

 of 

 Bengal

BANGKOK

H I M A L A Y A S

Shillong Plateau

 Andaman

Islands

YANGOON

Narcondam

 Island

Barren

Island

S I N

O

B

U

R

M

A

N

R

A

N

G

E

S

Southern Tethys suture

Foredeep (IndonesianAndaman trench=

subduction zone)

Inner volcanic arc

( Cenozoic volcanoes)

Major fault zones

Shan boundary fault zone

Thrust complexes

Oceanic spreading ridge

Chin Hills

Arakan Yoma

Naga Hills

NI DO

B

U

R

M

A

N

RANGES

Figure 4. Tectonic map of Myanmar and Andaman Basin (modified from Bender, 1983).

 Petroleum Systems and Related Geologic Studies in Region 8, South Asia
Figure 5. Generalized stratigraphy of Central Burma Basin, Myanmar (modified from Stamp, 1927; Khin and 

Win, 1969; and Bender, 1983).

EPOCHGROUP

Tertiary Cretaceous

Pleistocene

PlioceneMiocene Oligocene Eocene Paleocene PERIOD

Jaintia Irrawaddy Pegu

Irrawaddy

Delta

Prome

Embayment

Salin

Basin

Southwest

Chindwin

Basin

Kaungton

Tumyaung

Taunggale

Pyawbwe

Okhmintaung

Padaung/Tiyo

Shwezetaw/

Kyaukpon

Yaw 

Pondaung

Pyawbwe

Okhmintaung

Padaung/Tiyo

Laungshe

Paunggyi

Kabaw

Yaw/Nakyila

Laungshe

Paunggyi

Kabaw

Group

Kanbala

Tabyin/Tilin

Letkat

Pondaung

Kwingyaung

Kyaukkok Kyaukkok

Natma

Kathabung Obogon

Shwethamin

Mingin

Shale

Limestone

Sandstone

Siltstone, shale, 

and sandstone

Shale, siltstone, 

and sandstone

Gas production

Oil production

Source rocks

EXPLANATION

Volcanics

Shwezetaw/

Kyaukpon

Tabyin

FORMATION

Yaw 

Pondaung

Kabaw

Group

Taunggale

Kanbala

Unconformity

Eocene to Miocene Composite Total Petroleum System, Myanmar 
plate (Pivnik and others, 1998). Paleocene oblique subduction 

of the oceanic plate may have also detached the Burma plate 

from the Eurasian plate. Initial collision of the northeastern 

Indian and Burma plates occurred during the Eocene, possibly 

resulting in the coupling of the plates and accelerating the 

northward movement of the Burma plate (Pivnik and others, 

1998). From Eocene to early Miocene time, tectonic activity 

increased due to plate collision and rotation (figs. 10 and 11). 

During the Miocene, faulting, sedimentation, and the opening 

of the Andaman Sea were controlled primarily by northwestsoutheast extension and rifting. Regionally, terrestrial sediment influx from the rapidly rising Sino-Burman, Indo-Burman, and Himalayan ranges significantly exceeded carbonate 

accumulation rates on late Miocene platforms (Roychoudhury 

and Deshpande, 1982); and this influx smothered carbonate 

reef formation along the shelf areas. The former shelf areas 

along these collision zones were either subducted or became 

emergent fluvial-deltaic environments.

Early Pliocene collision of the Burma plate resulted in 

southwest-northeast transpressional forces that created reverse 

faults and north-south elongate anticlinal features such as the 

Pegu Yoma (fig. 3). The Pegu Yoma rose 900–1,200 m in the 

middle of the Central Burma Basin, dividing it into east and 

west subbasins. During the Pliocene, Mount Popa and other 

volcanoes along the volcanic arc to the south became more 

active, depositing volcanic mud and ash. The proto-Chindwin, Irrawaddy, and Sittang drainage systems developed. 

East-west uplift and faulting occurred near Mandalay, causing the Irrawaddy River to turn abruptly west and capture the 

Chindwin River. By Holocene time, anticlinal ridges in the 

eastern part of the Central Burma Basin were again uplifted 

and 300–450 m of sediments were stripped off. To the west, 

300–900 m of the newly uplifted Pegu Yoma were eroded. 

Myanmar now consists of three primary features; from east to 

west these are the Sino-Burman Ranges and Shan Plateau, the 

Central Burma Basin, and the Indo-Burman Ranges (fig. 3). 

The TPS rests on both marine and continental crusts, and the 

oceanic-continental plate boundary trends north up through 

the Central Burma Basin and coincides approximately with the 

northern boundary of the Irrawaddy-Andaman AU.

INDIAN

PLATE

AUSTRALIAN

PLATE

AFRICAN

PLATE

ANTARCTIC

PLATE

BURMA

PLATE

EURASIAN PLATES

Lowlands

Mountains

Shelf

Marine

Figure 6. Middle Jurassic (approximately 166 Ma). Perspective lat 20° S., long 68° E. (modified from Scotese 

and others, 1988, and Scotese, 1997).

   Petroleum Systems and Related Geologic Studies in Region 8, South Asia
Stratigraphy

Stratigraphic sequences ranging in age from Cretaceous 

to Pleistocene are shown in figure 5 for four different parts 

of the Central Burma Basin. The discussion that follows, 

however, includes mention of rocks (mostly older, but some of 

Cretaceous age and younger) not shown in figure 5; some of 

these strata are described from observations within the basin, 

but others are described from exposures elsewhere.

From Carboniferous to Jurassic time, extensive carbonates such as the Plateau Limestone Group and Shan Dolomite 

Group were deposited in what is now eastern Myanmar, 

including the area of the Shan Plateau and Tenasserim Mountain Ranges (Rau and Sethu, 1933; Hobson, 1941; Brunschweiler, 1974; Bender, 1983) (fig. 3).

The Jurassic Tati Limestone Formation in northeastern 

Myanmar and the Shan Plateau and the Kamawkala Limestone Formation in the east and southeast accumulated in a 

shallow marine environment before a period of uplift that was 

marked by a regional unconformity. On this unconformity, 

Upper Jurassic and Cretaceous redbeds of the Hsipaw, Kalaw, 

Mergui, and Khorat Formations were deposited (Bender, 

1983). Jurassic and Lower Cretaceous rocks are missing or not 

identified in the Central Burma Basin and in most of the IndoBurman Ranges to the west. Following this hiatus, in the area 

of the Indo-Burman Ranges, Early Cretaceous volcanic tuffs 

and cherts of the Kyauknimaw Formation were deposited. 

Throughout the Central Burma Basin, the Albian to Turonian 

age Lower Kabaw Group Paung-Chaung and Ywahaungyi 

Formation limestones were deposited. Campanian-age graded 

volcanoclastics then covered much of the Central Burma Basin 

and what are now the Indo-Burman Ranges. Following this 

episode of volcanic activity, extensive limestone reefs such as 

those in the Upper Cretaceous–Paleocene Falam Formation 

were deposited in the area of the Indo-Burman Ranges.

Along the eastern portion of the approaching Indian plate, 

Rajmahal Trap volcanics and carbonates of the Bolpur and 

Ghatal Formations accumulated. Although these carbonates 

are recognized today primarily on the eastern and western 

shelves, they were also likely deposited over much of the 

Lowlands

Mountains

Shelf

Marine

INDIAN

PLATE AUSTRALIAN

PLATE

AFRICAN

PLATE

ANTARCTIC

PLATE

BURMA

PLATE

EURASIAN PLATES

Figure 7. Early Cretaceous (approximately 130 Ma). Perspective lat 20° S., long 68° E. (modified from 

Scotese and others, 1988, and Scotese, 1997).

Eocene to Miocene Composite Total Petroleum System, Myanmar 
northern Indian shelf and the area of the Burma plate. This 

shelf environment persisted through Late Cretaceous when 

regressive sandstones such as the Tura Formation in the east 

and Pab Formation in the west were deposited.

From Paleocene through middle Eocene time, shales of 

the Kanbala and Taunggale Formations were deposited in the 

Irrawaddy Delta and Prome Embayment areas. Upper Cretaceous–Paleocene Kabaw Group (the Laungshe Shale of Stamp, 

1927) shales, limestones, and sandstones (fig. 5) were deposited in the Salin Basin. The lower Eocene Paunggyi Formation 

limestones rest unconformably on the Kabaw Group in the 

Salin Basin and conformably in the western Chindwin Basin 

(Bender, 1983). Overlying the Paunggyi Formation are the 

shales and sandstones of the middle Eocene Laungshe Formation of Bender (1983) (a different formation than the Laungshe 

of Stamp, 1927). Deposited on the Laungshe are the upper 

Eocene shales and sandstones of the Tabyin and Tilin Formations. Tabyin Formation shales have good source potential 

in the Salin Basin (Khin, 1991). Conformably overlying the 

Pondaung Formation (fig. 5) in the Central Basin, southwest 

Chindwin Basin, Prome Embayment, and Thayetmyo area are 

the shales and sandstones of the middle Eocene Yaw Formation. The eastern portion of the Central Burma Basin, which is 

part of the Asian plate, was emergent during the early Eocene. 

The area south of Mandalay and west of the Irrawaddy River 

was primarily a shallow marine environment, with the exception of the area of the present-day Indo-Burman Ranges (figs. 

4 and 12). The area north of Mandalay and in the eastern 

Chindwin Basin was emergent with a shallow marine environment only in the west.

The Eocene to upper Miocene lower Pegu Group in the 

Salin Basin and Prome Embayment area contains many of the 

identified source rocks and reservoirs within the Eocene to 

Miocene TPS. For example, upper Eocene–lower Oligocene 

Shwezetaw or Kyaukpon Formations of the Pegu Group consist 

of shallow marine interbedded clays, shales, and sandstones. 

INDIAN

PLATE

AUSTRALIAN

PLATE

AFRICAN

PLATE

ANTARCTIC

PLATE

EURASIAN

PLATES

BURMA

PLATE

Mascarene

Basin

Lowlands

Mountains

Shelf

Marine

Kerguelen

Hot Spot

Figure 8. Late Cretaceous (approximately 94 Ma). Perspective lat 20° S., long 68° E. (modified from Scotese 

and others, 1988, and Scotese, 1997).

10 Petroleum Systems and Related Geologic Studies in Region 8, South Asia
The Shwezetaw and Kyaukpon Formations contain both source 

and productive reservoir rocks, and they are conformably 

overlain by the Padaung Formation (fig. 5) clay and sandstone, 

which produces both oil and gas. Upper Eocene–lower Oligocene rocks were not deposited, or were eroded, in the western 

Irrawaddy Delta (Bender, 1983). Following this hiatus, shallow 

marine shales, sandstones, and limestones of the upper Oligocene Tumyaung Formation were deposited in the Irrawaddy 

Delta area. To the north, in the Prome Embayment and Salin 

Basin, the sandstones and limestones of the Okhmintaung 

Formation accumulated. On an unconformable late Oligocene 

surface marking the top of the Okhmintaung, as much as 1,000 

m of sandy shales and fine- to medium-grained sandstones 

of the upper Oligocene−lower Miocene Upper Pegu Group 

Pyawbwe Formation was deposited. The Pyawbwe sandstones 

produce both oil and gas. As much as 1,500 m of sandstones 

of the lower to middle Miocene upper Pegu Group Kyaukkok 

Formation overlies the Pyawbwe Formation. The Kyaukkok 

Formation also produces both oil and gas. The middle Miocene 

Obogon Formation (as much as 1,000 m thick) consists of fineto medium-grained sandstones, sandy shales, and siltstones. 

The unconformity at the top of the Obogon Formation marks 

the top of the Pegu Group. Deposited in alluvial environments, 

on the unconformable top of the Pegu Group, was as much 

as 3,000 m of nonmarine medium- to coarse-grained massive 

crossbedded sandstones, clays, and conglomerates of the upper 

Miocene to Quaternary Irrawaddy Group (fig. 13).

Today the total sedimentary column in the Central 

Burma Basin exceeds 12,000 m in places, with the greatest 

thickness in the Irrawaddy Delta and the thinnest along the 

east edge of the basin.

Exploration and Production

Oil seeps and production from hand-dug wells were 

reported in the Yenangyuang area as early as the thirteenth 

century. By 1797 production at Yenangyuang (fig. 14) from 

Lowlands

Mountains

Shelf

Marine

AFRICAN

PLATE

ANTARCTIC

PLATE

INDIAN

PLATE

AUSTRALIAN

PLATE

BURMA

PLATE

Seychelles

Mascarene

rift basin

Ninety East Ridge

Kerguelen

Hot Spot

EURASIAN

PLATES

Tethyan Sea

Madagascar

Figure 9. Latest Cretaceous (approximately 69 Ma). Perspective lat 20° S., long 68° E. (modified from Scotese 

and others, 1988, and Scotese, 1997).

Eocene to Miocene Composite Total Petroleum System, Myanmar 11
several hundred hand-dug wells on 12.8-m spacing yielded 

a total of 200–400 barrels per day. Hand-dug wells were 

reported as late as 1949, and to be as deep as 120 m. In 1888, 

the first “drilled” (cable tool) well was brought in, and rotary 

drills were used as early as 1911 (Stamp, 1927). Although 

the total number of exploratory wells drilled was not large, 

successes continued until World War II, when the petroleum 

industry infrastructure was almost completely destroyed. 

Following that war, rehabilitation of the industry was slow. In 

1959, the Payagon oil and gas field was discovered, and the 

rate of exploration increased (fig. 15). The oil industry was 

nationalized in 1965 and the national oil company Myanma 

Oil Company (MOC) was formed. In 1970 MOC discovered 

Mann oil field, and between 1972 and 1974 MOC drilled 12 

wells in the Gulf of Martaban. That drilling effort resulted in 

several uneconomic gas discoveries. In 1974 MOC invited 

foreign oil companies to bid on offshore blocks. Thirteen 

offshore blocks were awarded. After numerous dry holes and 

one gas discovery off the Arakan coast, all of the blocks were 

relinquished by 1977.

Interest in offshore exploration was revived in 1982, 

when Yadana gas field was discovered 70 km offshore in 

the Irrawaddy Delta fan at a water depth of 45 m (fig. 14). 

Reserves are estimated at more than 5 trillion cubic feet of 

gas (TCFG), with the nearby Sein and Badamyar discoveries 

adding 0.7 TCFG of reserves. Total Myanmar Exploration 

and Production (TMEP), Unocal, Petroleum Authority of 

Thailand Exploration and Production International Limited 

(PTTEP), and Myanma Oil and Gas Enterprise (MOGE), in a 

joint venture, began development of the field in 1992, and in 

1998 Yadana field came on line (www.energy.gov.mm/MOGE; 

accessed 2003). Yetagun gas field, with reserves in excess of 

3 TCFG and 80 million barrels (mmb) of condensate, in the 

Taninthayi offshore area of the eastern Andaman Sea (fig. 14), 

was discovered in 1992 (www.energy.gov/mm/MOGE_2.htm; 

accessed 2003). As demand for gas in the region increases and 

Lowlands

Mountains

Shelf

Marine

ANTARCTIC

PLATE

AFRICAN

PLATE

AUSTRALIAN

PLATE

INDIAN

PLATE

EURASIAN

PLATES

Madagascar Ninety East Ridge

BURMA

PLATE

Seychelles

Somali

Basin

Mascarene

Basin

Bengal

Basin

AssamArakan

Shelf Bombay

Shelf

Indus

Shelf

Figure 10. Middle Eocene (approximately 50 Ma). Perspective lat 20° S., long 68° E. (modified from Scotese and 

others, 1988, and Scotese, 1997).

12  Petroleum Systems and Related Geologic Studies in Region 8, South Asia
a pipeline system is developed, further exploration and development in the area are likely. Recently a large gas discovery 

has been made off the west coast of Myanmar.

Within the Central Burma Basin at least 59 fields were 

discovered between 1864 and 1996 (Petroconsultants, 1996). 

These fields contain at least 76 reservoirs that have produced 

oil, gas, or condensate. The largest fields are Yenangyuang 

(>200 mmbo), Yadana (>5 TCFG), and Yetagun (>3 TCFG) 

discovered in 1889, 1983, and 1992, respectively (fig. 14).

The plot of cumulative new-field wildcat wells versus 

completion year for the Irrawaddy-Andaman geologic province (fig. 15) shows that, although the total number of exploration wells drilled is low, the rate of exploration increased 

substantially in the 1960s and the rate has remained relatively 

constant since the 1970s.

The plots of known oil and gas fields ranked by size and 

grouped in thirds by date of discovery do not show a significant decrease in field size in progressive thirds (fig. 16). The 

INDIAN

PLATE

Lowlands

Mountains

Shelf

Marine

AUSTRALIAN

PLATE

AFRICAN

PLATE

ANTARCTIC

PLATE

EURASIAN

PLATES

Ninety East Ridge

Myanmar

Madagascar

Seychelles

Somali

Basin

Mascarene

Basin

small decrease in field size through time indicates that the 

province is still not mature in terms of exploration; a mature 

province would show a larger decrease in field sizes between 

the first and third thirds. The largest fields were found in the 

first and third thirds for oil and the second and third thirds 

for gas. Known field size versus discovery year plots (fig. 17) 

also show that relatively large gas fields are still being found.

The plots of cumulative volume of known (cumulative 

production plus proven reserves) oil and gas versus the field 

discovery year (fig. 18) show recent large increases in cumulative known volumes. The reservoir depth versus field discovery 

year plots (fig. 19) indicate that, although generally deeper, in 

some cases the reservoirs found later were very shallow. This 

may indicate that significant resource is to be found that was 

previously bypassed. These are also areas where seismic data 

acquisition and interpretation are difficult. Application of the 

most recent seismic technology and methods to these areas 

may reveal additional shallow traps. Note that data for gas 

Figure 11. Late Oligocene (approximately 27 Ma). Perspective lat 20° S., long 68° E. (modified from Scotese 

and others, 1988, and Scotese, 1997). 

Eocene to Miocene Composite Total Petroleum System, Myanmar 13
60 Ma 40 Ma

WEST EAST WEST EAST

Molasse sediments

Flysch sediments

Paleozoic shelf sediments

Granodioritic intrusions

Crystalline Asian plate

Oceanic plate

Fault

EXPLANATION

Land area

Marine

Alluvial/deltaic

PEOPLE’S

REPUBLIC

OF CHINA

95°E

INDIA

THAILAND

MYANMAR

Gulf

of

Martaban

99°E

28°

24°

20°

16°

PEOPLE’S

REPUBLIC

OF CHINA

95°E

INDIA

THAILAND

MYANMAR

Gulf

of

Martaban

99°E

28°

24°

20°

16°

Figure 12. Generalized early (left) and late (right) Eocene paleogeography (modified from Khin and Win, 1968) and associated 

cross sections near lat 20° N. (modified from Bannert and Helmcke, 1981).

14  Petroleum Systems and Related Geologic Studies in Region 8, South Asia
Figure 13. Generalized early Miocene (left) and Pliocene (right) paleogeography (modified from Khin and Win, 1968) and recent 

cross section near lat 20° N. (modified from Bannert and Helmcke, 1981).

WEST

EAST

PEOPLE’S

REPUBLIC

OF CHINA

95°E

INDIA

THAILAND

MYANMAR

Gulf

of

Martaban

99°E

28°

24°

20°

16°

PEOPLE’S

REPUBLIC

OF CHINA

95°E

INDIA

THAILAND

MYANMAR

Gulf

of

Martaban

99°E

28°

24°

20°

16°

EXPLANATION

Land area

Marine

Alluvial/deltaic

Molasse sediments

Flysch sediments

Paleozoic shelf sediments

Granodioritic intrusions

Crystalline Asian plate

Oceanic plate

Fault

Eocene to Miocene Composite Total Petroleum System, Myanmar 15
EXPLANATION 

Quaternary sediments 

Neogene sedimentary rocks 

Paleogene sedimentary rocks 

Tertiary sedimentary rocks 20°

Tertiary intrusive and extrusive rocks 

Mesozoic and Paleozoic igneous and

 metamorphic rocks 

Cretaceous sedimentary rocks 

Jurassic metamorphic and sedimentary rocks 

Triassic metamorphic and sedimentary rocks 

Lower Triassic to Upper Carboniferous 

Mesozoic and Paleozoic intrusive and

 metamorphic rocks 

Undivided Paleozoic rocks 

Upper Paleozoic rocks 

Lower Paleozoic rocks 

Undivided Permian rocks 

Carboniferous sedimentary rocks 

Undivided Carboniferous to

 Ordovician rocks 15°

Undivided Silurian rocks 

Undivided Precambrian rocks 

Geologic province boundary 

Fault 

Inferred fault 

River 

Water depth contours 

Oil field 

Gas field 

Oil and gas field 

Town or city 

Anticline 

10°

Figure 14. Generalized geology and some 

oil and gas fields (modified from Khin, 1991, 

and Wandrey and Law, 1999). 

Mt.

 Popa 

Mann 

Prome 

Embayment 

Yadana 

I r r a w a d d y 

River 

Salin 

Basin 

Yetagun 

Irrawaddy 

Delta 

X

KABAW 

SAGAING FAULT 

Yenangyat 

Yenangyuang 

Minbu 

Chindwin River 

Syriam 

Payagon 

Prome 

Myanauang 

Shwepyitha 

Chauk 

Sein 

Badamyar Taninthayi 

Tenasserim Ranges

Indo-Burman Ranges 

Shan Plateau 

Andaman Islands 

Mandalay 

Yangoon 

Andaman 

Sea 

Gulf of 

Martaban 
discoveries do indicate a slight trend toward deeper discoveries. Exploration strategies designed to find larger commercially 

viable gas fields offshore are driving this trend toward deeper 

drilling.

Exploration is presently controlled by the limited market 

for gas within Myanmar as well as the neighboring countries 

of Thailand and Bangladesh. When gas demand increases, 

exploration for and development of Myanmar’s gas potential 

will likely accelerate.

Total Petroleum System

The USGS recognizes several petroleum systems within 

the Irrawaddy-Andaman and North Burma geologic provinces. 

For assessment purposes, however, they were combined into 

one composite petroleum system, the Eocene to Miocene 

Composite Total Petroleum System (804801). This combination was made because correlations between source rocks and 

reservoir hydrocarbons were available for only the Central 

Burma Basin at the time of the assessment. Oil analyses indicate Eocene and Oligocene–lower Miocene sources (Curiale 

and others, 1994; M.D. Lewan, oral commun., 1998). Multiple 

stacked source and reservoir rocks, connected by extensive 

fault systems, allow mixing of hydrocarbons; this makes identification of distinct TPS difficult.

The rocks that compose this TPS are of Eocene through middle Miocene age (fig. 23). These formations include carbonates, 

shallow marine shales and sandstones, and the sandstones, siltstones, shales, and coals of deltaic, alluvial, and lagoonal facies.

Source Rocks

The primary source rocks identified in the Central Burma 

Basin are the middle Eocene Tabyin/Tilin, Taunggale, and 

Laungshe Formations; upper Eocene Yaw Formation; lower 

Oligocene Shwezetaw, Padaung, and Okhmintaung Formations (Khin, 1991) (fig. 5). Up to 1,200 m thick, the Tabyin 

Formation consists of weathered clays with coal particles, 

platy limestone, lignite seams, and thin tuffaceous sandstone 

layers that increase in number to the north (Cotter, 1914). The 

Yaw Formation consists of as much as 300 to 600 m of shales, 

interbedded limestones, and bituminous coal in the Chindwin Basin (Cotter, 1914). The Yaw Formation was primarily 

deposited in a marine environment in the western portion of 

the Central Burma Basin and lagoonal to alluvial environment 

in the eastern portion. The Shwezetaw Formation, as much as 

1,200 m thick, consists of sandstones (calcareous in the lower 

part), shales, and thin coal seams deposited in shallow marine 

to alluvial environments (Vredenburg, 1922). The Padaung 

Formation consists of as much as 1,500 m of marine shales 

with interbedded sandstones that increase in thickness and 

frequency near the top of the formation (Bender, 1983). The 

Okhmintaung Formation consists of shallow marine sandstones, shales, and infrequent limestones.

Oligocene and Miocene source and reservoir rocks occur 

along the north, east, and west sides of the Andaman Sea, but 

near the spreading center sediment thickness was probably 

insufficient for generation to occur. 

0

20

40

60

80

100

120

1840 1860 1880 1900 1920 1940 1960 1980 2000 2020

YEAR

C

U

M

U

L

A

TIV

E

N

U

M

B

E

R

OF N

E

W-FIE

L

D

WIL

D

CAT

W

E

L

L

S

Figure 15. Cumulative number of new-field wildcat wells versus completion year for the Irrawaddy-Andaman geologic 

province (Petroconsultants, 1996).

Eocene to Miocene Composite Total Petroleum System, Myanmar 17
Source Rock Richness

Total organic carbon (TOC) content is generally low 

where sampled, with a TOC minimum in the Gulf of Martaban 

of <0.2 percent and a maximum of 1.5 percent. The kerogen is 

primarily gas prone, terrestrial, type III in the Gulf of Martaban. API gravities of oils range from 8° to 52°. Sulfur content 

ranges from 0.01 to 0.23 percent. Curiale and others (1994) 

and Khin (1991) suggested that only one oil family is present 

in the Central Burma Basin and that variations in chemical 

characteristics of oil samples are due primarily to biodegradation. Khin (1991) also suggested a possible Mesozoic source 

in the Salin Basin, the Cretaceous Paung Chaung Limestone 

Formation of the Kabaw Group (fig. 5).

Maturation

Burial depths generally increase from north to south 

in the Central Burma Basin, with the youngest source rocks 

(Miocene) found in the Gulf of Martaban and northern Andaman Sea (Matthews and others, 2000). In the Salin Basin 

(fig. 3) the thermal gradient is low, with mature source rocks 

at depths of 4 km or greater (Khin, 1991; Curiale and others, 

1994). Given the low thermal gradient, upper Eocene and 

lower Oligocene source rocks are likely to be the youngest 

mature rocks in the north. Elevated temperatures associated 

with the tectonic and volcanic activity are generally localized and would have had little effect on regional maturation 

(Barker and others, 1984). The R0 value versus depth plot 

for the Gulf of Martaban indicates that rocks of Miocene 

age were sufficiently mature to generate oil and gas (fig. 20) 

(Bender, 1983).

Samples taken from depths of 3,048 m in the Salin Basin 

have a maturity of 0.5 percent Rm. In order to reach thermal 

maturities sufficient for generation and expulsion, Khin (1991) 

suggested, the source must be deeper in the Salin Basin. 

Curiale and others (1994) argued that Eocene and lower Oligocene source rocks reached the minimum maturity required 

for generation. Further burial history data and collection of 

samples from greater depths may resolve this question.

Generation and Migration

The onset of generation may have been as early as late 

Miocene (12 to 8 Ma), and generation is likely continuing today in at least the northern part of the Central Burma 

Basin. Generation probably occurred first in the Gulf of 

Martaban and Irrawaddy Delta area where burial depths were 

the greatest. Miocene rocks in the deep basin entered the oil 

window 8 to 5 Ma, the “gas window” 6.5 to 5 Ma, and the 

“dry gas window” 6 to 4.5 Ma (Matthews and others, 2000). 

Migration is primarily into adjacent reservoirs and vertically 

through faults that developed during compressional stages 

that created the anticlinal structures present in the Central 

Burma Basin.

Reservoir Rocks

Reservoir rocks range through almost the entire stratigraphic section from Eocene to Miocene (figs. 21 and 23). 

Primary reservoir rocks include sandstones of the Eocene–

lower Oligocene Shwezetaw, Padaung, and Okhmintaung 

Formations and the Miocene Pyawbwe and Kyaukkok Formation sandstones. These reservoir sandstones were deposited in alluvial, deltaic, and near-shore marine environments.

Reservoir quality within the Pegu Group reservoirs varies 

throughout the province, with porosity ranging from less than 

20 percent to more than 30 percent and permeabilities from 

less than 92 millidarcies to more than 3,200 millidarcies.

1

10

100

1,000

0 10 20 30 40 50

1

10

100

1,000

10,000

0 10 20 30 40 50

GAS FIELD RANK

KNO

WN G

AS FIELD SIZE (BCF)

OIL FIELD RANK

KNOWN OIL FIELD SIZE (MMB)

First third of fields discovered

Second third of fields discovered

Third third of fields discovered

Figure 16. Known oil and gas field sizes grouped in thirds by 

discovery date and ranked by size for the Irrawaddy-Andaman 

geologic province (Petroconsultants, 1996).

18 Petroleum Systems and Related Geologic Studies in Region 8, South Asia
Traps and Seals

Anticlines, faulted anticlines, fault blocks, and stratigraphic traps are the primary traps (Petroconsultants, 1996) 

(fig. 22). Seals include interbedded Oligocene and Miocene 

shales and clays of the Pegu Group and overlying Irrawaddy 

Group. 

The primary elements of the Eocene to Miocene Composite Total Petroleum System and their relationship to timing 

of events are shown in the events chart (fig. 23). 

Assessment Units

The Eocene to Miocene Composite TPS was subdivided into two units for assessment purposes: these are the 

Irrawaddy-Andaman (80480102) Assessment Unit (AU) and 

the Central Burma Basin (80480101) AU (fig. 2). 

The Irrawaddy-Andaman AU is located in the southern 

Central Burma Basin, the Irrawaddy Delta and Andaman 

Basin. It is a gas-prone onshore and offshore basin developed 

subparallel to the converging continental and marine plate 

0

2

4

6

8

10

12

14

16

1840 1860 1880 1900 1920 1940 1960 1980 2000

FIELD DISCOVERY YEAR

C

U

M

ULA

TIVE N

U

MBER OF OIL FIELD

S

0

5

10

15

20

25

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

FIELD DISCOVERY YEAR

C

U

M

ULA

TIVE N

U

MBER

OF G

A

S FIELD

S

Figure 17. Cumulative number of oil and gas fields versus discovery year for the Irrawaddy-Andaman 

geologic province (Petroconsultants, 1996).

Eocene to Miocene Composite Total Petroleum System, Myanmar 19
boundaries. The rocks that compose this assessment unit 

include Eocene sandstones and shales and the OligoceneMiocene Pegu Group, with a thickness exceeding 6,500 m in 

places. This group is made up of interbedded, shallow marine 

shales, limestones, and sandstones, and the sandstones, shales, 

and coals of deltaic and lagoonal facies. 

Source rocks include the lower Oligocene shales of the 

Yaw, Shwezetaw, and Okhmintaung Formations and shales 

of the Pegu Group. Total organic content is generally low 

(<1.75 percent) where sampled. Organic material is primarily 

terrestrially derived type III kerogen. Maturities are generally 

low, from R0 0.2 to 1.7 percent where sampled in the Gulf of 

Martaban, but maturities are likely higher in areas of the basin 

where burial depths are greater.

Significant generation commenced during the Pliocene. 

Migration is primarily vertical through fault and fracture systems associated with the plate collision. These fault systems 

have been periodically reactivated through the present. Short 

updip migration along the flanks of the basin is also likely.

Primary reservoir rocks are interbedded sandstones of 

the Pegu Group. Reservoir quality is fracture enhanced in 

many cases. Traps include anticlines, faulted anticlines, and a 

few stratigraphic traps. Seals include interbedded Oligocene 

and Miocene shales and clays, and thick clays of the upper 

Miocene−Pliocene Irrawaddy Group. Although few stratigraphic traps have been discovered, potential exists for more 

discoveries in the deltaic sequences. There is also potential for 

growth-fault related traps in the offshore fans.

0

100

200

300

400

500

600

700

800

1840 1860 1880 1900 1920 1940 1960 1980 2000

FIELD DISCOVERY YEAR

C

U

M

ULA

TIVE K

N

O

W

N

OIL V

OLU

ME (M

MB)

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

FIELD DISCOVERY YEAR

C

U

M

ULA

TIVE K

N

O

W

N

G

A

S

V

OLU

ME (BCF)

Figure 18. Cumulative known (cumulative production plus reserves) oil and gas volumes versus 

discovery year for the Irrawaddy-Andaman geologic province (Petroconsultants, 1996).

20 Petroleum Systems and Related Geologic Studies in Region 8, South Asia
The Central Burma Basin AU is located in the north and 

central part of the Central Burma Basin of Myanmar. It is an oilprone onshore basin developed parallel to the converging continental and marine plate boundaries. The rocks that make up this 

assessment unit include the Eocene Laungshe Shale, Tilin, and 

Pondaung Sandstones, and the Oligocene-Miocene Pegu Group, 

the latter exceeding 6,500 m in thickness. This group includes 

interbedded sandstones, shales, and coals of deltaic to fluvial 

facies, and shallow marine shales, limestones, and sandstones.

Source rocks include the upper Eocene–lower Oligocene 

shales of the Yaw, Shwezetaw, and Okhmintaung Formations. 

Total organic carbon content, generally low where sampled 

(less than 1.7 percent), is primarily terrestrially sourced type 

II and III kerogens. The onset of generation probably occurred 

in late Miocene. Migration is primarily over short distances, 

updip, and vertically through fault and fracture systems associated with the plate collision. These fault systems have been 

periodically reactivated through the present.

Figure 19. Reservoir depth versus field discovery year for oil (top) and gas (bottom) in the IrrawaddyAndaman geologic province (Petroconsultants, 1996).

0

500

1,000

1,500

2,000

2,500

3,000

1840 1860 1880 1900 1920 1940 1960 1980 2000

FIELD DISCOVERY YEAR

RESERVOIR DEPTH, IN METERS

0

500

1,000

1,500

2,000

2,500

3,000

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

FIELD DISCOVERY YEAR

RESERVOIR DEPTH, IN METERS

Eocene to Miocene Composite Total Petroleum System, Myanmar  21
Interbedded sandstones of the Pegu Group are the primary reservoirs. The Eocene Pondaung and Tilin sandstones 

may also have reservoir potential and have a combined thickness of as much as 3,500 m including the interbedded shales.

Traps include anticlines, faulted anticlines, fault truncations, and stratigraphic traps. Seals include interbedded Oligocene and Miocene shales and clays, and the thick clays of 

the upper Miocene and Pliocene Irrawaddy Group. Structures 

in the Chindwin Basin area and stratigraphic traps developed in alluvial and deltaic systems have been only lightly 

explored and may have significant potential.

Cumulative Production Data

Based on Petroconsultants International Data Corporation data to 1996, the Irrawaddy Province (8048) was ranked 

103rd in the world (including United States provinces). 

This volume is approximately 0.1 percent of world volume 

excluding the United States. Known petroleum volumes are 

0.7 billion barrels of oil (BBO) and 10.3 TCFG for a total of 

2.5 billion barrels of oil equivalent (BBOE) including natural 

gas liquids (NGL).

Assessment Comparisons

Kingston (1986) estimated the mode of undiscovered 

petroleum resources in the Irrawaddy basin at 1.1 BBO and at 

<2.1 TCFG. Masters and others (1998) estimated the mean for 

undiscovered petroleum resources at 1.4 BBO for the Burma 

Basin and 6.2 TCFG for the Burma Basin and Andaman Sea. 

In this study mean undiscovered resources were estimated to 

be 725 mmbo and 20.5 TCFG (table 1).

Differences in estimates for undiscovered oil and gas 

result because the areas assessed are not the same size and 

significantly more data were available for the most recent 

assessment.

Summary

The Eocene-Miocene Composite Total Petroleum System 

has produced the majority of the hydrocarbons in the Central 

Burma Basin and Irrawaddy Delta. Structural traps are predominant, but stratigraphic traps are likely to be found in both 

ancient and modern delta environments.

Figure 20. Mean vitrinite reflectance of rock 

samples in Gulf of Martaban (modified from 

Bender, 1983).

? ?

Reliable value

Unreliable value

0

1,000

2,000

3,000

4,000

Depth

m

MEAN REFLECTANCE (percent Ro)

0 0.5 1.0 1.5 2.0

Lower Cretaceous and 

Upper Jurassic samples

Late Tertiary

samples

unconformity

unconformity

EXPLANATION

30%

Miocene

55%

1%

Paleocene

3%

Precambrian

1%

10%

unknown

Eocene

Oligocene

Figure 21. Temporal distribution of producing reservoirs by 

youngest age. Percentages represent number of reported 

occurrences by reservoir (IHS Energy Group, 2001).

22  Petroleum Systems and Related Geologic Studies in Region 8, South Asia
Code Undiscovered Resources

and Field MFS Prob. Oil (MMBO)

Type (0-1) F95 F50 F5 Mean F95 F50 F5 Mean F95 F50 

80480101 Central Burma Basin Assessment Unit

Oil Fields 1 75 446 1,192 516 158 951 2,751 1,134 9 5

Gas Fields 6 133 759 2,011 874 4 2

Total 1.00 75 446 1,192 516 291 1,709 4,763 2,008 13 8

80480102 Irrawaddy-Andaman Assessment Unit

Oil Fields 1 27 177 498 209 197 1,285 3,903 1,563 11 7

Gas Fields 6 3,710 14,982 36,669 16,949 125 51

Total 1.00 27 177 498 209 3,908 16,266 40,572 18,512 136 58

804801 Total: Eocene to Miocene Composite Total Petroleum System

Oil Fields 102 624 1,690 724 356 2,235 6,654 2,697 20 13

Gas Fields 3,843 15,740 38,680 17,824 129 53

Total 1.00 102 624 1,690 724 4,199 17,976 45,334 20,521 149 66

1.001.001.00

[MMBO, million barrels of oil. BCFG, billion cubic feet of gas. MMBNGL, million barrels of natural gas liquids. MFS, minimum field size assessed (MMBO or BCFG). Prob., pr

geologic and accessibility probabilities) of at least one field equal to or greater than the MFS. Results shown are fully risked estimates. For gas fields, all liquids are included under 

category. F95 represents a 95 percent chance of at least the amount tabulated. Other fractiles are defined similarly. Fractiles are additive under the assumption of perfect positive cor

not applicable]

Gas (BCFG) NGL (

Table 1. USGS estimates of undiscovered oil and gas resources by assessment unit and aggregated for the total petroleum system (Wandrey and others, 2
1% 1%

3% 1%

Dome

4%

3%

1%

12%

69%

Draping structure Facies change

Fault block Fault

Fold nose

Monoclinal fold

Regional arch

Asymmetric anticline

Anticline

5%

Figure 22. Distribution of trap type. Percentages represent 

number of reported occurrences (IHS Energy Group, 2001).

Figure 23. Events chart summarizing stratigraphy, source rocks, reservoirs, seals, traps, timing, and petroleum information for the 

Eocene to Miocene Composite Total Petroleum System.

Rock unit

Reservoir rock

Seal rock

Overburden rock

Trap formation

Preservation

GEOLOGIC

TIME

SCALE

PETROLEUM

SYSTEM EVENTS

30 15

MESOZOIC CENOZOIC

Cretaceous

Unconformity

Source rock

75 60 45

Paleocene Eocene Oligocene Miocene Pliocene Tiln Ss Tabyin Clay Pondaung Ss Padaung Cl

Lower Pegu Gp. Okhmintaung Ss

Kyaukkok Ss

Unconformity

Upper Pegu Gp.

Pyawbwe Ss

Unconformity

Irrawaddy

Group

Paunggyi Cngl

Laungshe Sh

Yaw Fm

Shwezetaw Fm

Obogon Fm

Migration

Accumulation

Generation

Favorable elements of this petroleum province are suitable organic material, sufficient maturation, ongoing charging 

of reservoirs, short near-vertical migration paths, and early 

trap formation.

Selected References

Bannert, D., and Helmcke, D., 1981, The evolution of the 

Asian plate in Burma: Geologische Rundschau, v. 70, no. 2, 

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Barker, C.E., and Pawlewicz, M.J., 1987, The effects of igneous intrusions and higher heat flow on the thermal maturity 

of Leonardian and younger rocks, western Delaware Basin, 

Texas, in Cromwell, D.W., and Mazzullo, L., eds., The 

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Guidebook to the Glass Mountains, West Texas: Midland, 

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Bender, F., 1983, The geology of Burma, in Bender, F., 

Jacobshagen, V., de Jong, J.D., and Luttig, G., eds., Beitrage 

zur Regionalen Geologie der Erde: Berlin, p. 298.

24  Petroleum Systems and Related Geologic Studies in Region 8, South Asia
Besse, J., and Courtillot, V., 1984, Paleogeographic maps of 

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Australia, November 4–7, 1991; Conference Proceedings, 

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Khin, U.A., and Win, U.K., 1969, Preliminary studies of the 

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G.L., 1997, Ranking of the world’s oil and gas provinces by 

known petroleum volumes: U.S. Geological Survey OpenFile Report 97-463, one CD-ROM.

LeDain, A.Y., Tapponnier, P., and Molnar, P., 1984, Active 

faulting and tectonics of Burma and surrounding areas: 

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Magoon, L.B., and Dow, W.G., 1994, The TPS—From source 

to trap: American Association of Petroleum Geologists 

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Mallic, S.V., Raju, S.V., and Mathur, N., 1997, Geochemical characterization and genesis of Eocene crude oils in 

a part of Upper Assam Basin, India, in Proceedings Second International Petroleum Conference & Exhibition, 

PETROTECH-97: New Delhi, v. 1, p. 391–402.

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Selected References  25
Reddy, B.R.P., Basumatary, J.K., Rizvi, S.F.H., and Kumar, 

Kishan, 1995, Contribution of Tertiary coals towards commercial hydrocarbon deposits in a part of Upper Assam 

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distribution of carbonate facies, Bombay offshore region, 

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M.S.R., Manju, Mathur, and Miara, K.N., 1997, Biomarker 

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American Association of Petroleum Geologists Bulletin, 

v. 11, no. 6, p. 557–579.

Stamp, L.D., 1934, Natural gas fields of Burma: American 

Association of Petroleum Geologists Bulletin, v. 18, no. 3, 

p. 315–326.

Tapponnier, P., Peltzer, G., LeDain, A.Y., Armijo, R., and 

Cobbold, P., 1982, Propagating extrusion tectonics in 

Asia—New insights from simple experiments in Plasticene: 

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and gas fields, and geologic provinces of South Asia: U.S. 

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26  Petroleum Systems and Related Geologic Studies in Region 8, South Asia