Figure 1.  Locations of 23 provinces of southeast Asia assessed in this study.

Thai Basin

Penyu-West Natuna

Basin

Malay Basin

Sulu Sea Basin

Palawan Shelf

 Basin

Khorat Plateau

Thai

Cenozoic

Basins

Cuu Long Basin

Nam Con Son Basin 

 Baram Delta/

Brunei-Sabah 

 Basin

South China Sea Platform

Greater 

Sarawak Basin

Kutei Basin

North 

Sumatra Basin

Central 

Sumatra Basin

South 

Sumatra 

Basin

Song 

 Hong Basin

Phu 

Khanh 

Basin

Northwest 

Java Basin East Java Basin

Barito 

Basin

Tarakan 

Basin

 3605

Palawan 

 Shelf

Hanoi

Manila

Jakarta

Bangkok

Rangoon

Singapore

Vientiane

Phnom Penh

Kuala Lumpur

100°E 110°E 120°E

20°N

10°N

0°

10°S

Sulu

Sea

Gulf of 

Thailand

Java Sea

Andaman

Sea

South

China

Sea

Celebes Sea

Indian Ocean

MALAYSIA

BRUNEI

PHILIPPINES

BORNEO

SULAWESI

MALAYSIA

SUMATRA

JAVA

AUSTRALIA

CHINA

THAILAND

BURMA

VIETNAM

CAMBODIA

LAOS

Indian 

Ocean

Southeast 

Asia

Assessment 

Area

I N D O N E S I A

0 250 500 Kilometers

0 125 250 Miles

Explanation

Assessed Provinces

C H I N A

Pearl River 

Mouth Basin

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2010–3015

June 2010

World Petroleum Resources Assessment Project

Assessment of Undiscovered Oil and Gas Resources of 

Southeast Asia, 2010

Printed on recycled paper

Using a geology-based assessment 

methodology, the U.S. Geological Survey 

estimated a mean of 21.6 billion barrels 

of oil and a mean of 299 trillion cubic 

feet of undiscovered natural gas in 

23 provinces of southeast Asia.

Introduction

The U.S. Geological Survey (USGS) 

assessed the potential for undiscovered 

conventional oil and gas fields within 

geologic provinces of southeast Asia 

as part of the USGS World Petroleum 

Resources Assessment Project (fig. 1). 

Twenty-three provinces were assessed in 

this study (table 1), including provinces 

entirely or partially within Thailand, 

Laos, Cambodia, Vietnam, Myanmar, 

Malaysia, Indonesia, Brunei, China, and 

Philippines. Many of the oil and gas 

basins within these geologic provinces 

originated as extensional basins that 

evolved into a post-rift thermal subsidence phase, which is characterized by 

carbonate platform deposits or prograding clastic wedges typical of passive margins. This simple sketch does not reflect 

the complexity of the tectonic history in 

southeast Asia, which has included rifting and attenuation of continental crust, 

opening and closing of ocean basins, 

development of regional fault systems 

and associated structures, collision and 

suturing of terranes, formation of accretionary prisms and local uplifts (Morley, 

2001, 2002; Hutchinson, 2004; Hall and 

others, 2008).

Petroleum systems in provinces 

of southeast Asia reflect the complex 

tectonic evolution, but generalities can 

be made concerning the origin of oil and 

gas in what are mainly Cenozoic basins 

(Todd and others, 1997; Doust and Sumner, 2007; Hall, 2009). Petroleum source 

rocks mainly are synrift deep-basin 

lacustrine and marginal lacustrine shales; post-rift marginal marine to marine coaly 

mudstones, coals, and marine shales (Todd and others, 1997). Oil predominantly is generated from synrift lacustrine shales, whereas gas is generated from the post-rift coaly 

mudstones, coals, and shales, and by cracking of earlier-formed oil. As gas generation 
Table 1. Southeast Asia assessment results.

[MMBO, million barrels of oil. BCFG, billion cubic feet of gas. MMBNGL, million barrels of natural gas liquids. Results shown are fully risked estimates. For gas accumulations, all liquids are included as NGL (natural gas liquids). Undiscovered gas resources are the sum of nonassociated and associated gas. F95 represents a 95-percent

chance of at least the amount tabulated; other fractiles are defined similarly. AU, assessment unit. AU probability is the chance of at least one accumulation of minimum

size within the AU. TPS, total petroleum system. Gray shading indicates not applicable. Largest expected oil field size in MMBO; gas field size is in BCFG]

Total Petroleum Systems 

(TPS) 

and Assessment Units (AU)

AU

probability

Field

type

Largest

expected

field size

Total Undiscovered Resources

Oil (MMBO) Gas (BCFG) NGL (MMBNGL)

F95 F50 F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean

Pearl River Mouth Basin Province (Paleogene Lacustrine TPS)

Eocene-Miocene

Reservoirs AU 1.0

Oil 97 279 567 1,079 608 290 694 1,526 773 10 26 63 30

Gas 2,371 3,279 8,078 18,047 9,035 102 256 588 289

Song Hong Basin Province (Eocene-Miocene Composite TPS)

Paleogene-Neogene

Reservoirs AU 1.0

Oil 62 80 183 399 204 405 945 2,112 1,061 4 11 25 12

Gas 922 5,782 10,599 18,625 11,205 121 226 399 238

Phu Khanh Basin Province (Paleogene TPS)

Paleogene-Neogene

Reservoirs AU 1.0

Oil 107 48 166 593 223 244 854 3,152 1,162 3 9 37 13

Gas 1,955 4,268 10,679 23,532 11,878 89 226 507 253

Khorat Plateau Province (Mesozoic TPS)

Permian Carbonates AU 1.0

Oil – 0 0 0 0 0 0 0 0 0 0 0 0

Gas 279 502 1,171 2,426 1,278 3 6 14 7

Khorat Group Sandstones

AU 1.0

Oil – 0 0 0 0 0 0 0 0 0 0 0 0

Gas 202 187 568 1,478 665 1 3 8 4

Cuu Long Basin Province (Eocene-Oligocene Composite TPS)

Syn-Rift Reservoirs AU 1.0

Oil 427 726 1,599 3,204 1,735 1,463 3,359 7,339 3,748 40 92 203 103

Gas 315 112 487 1,750 649 3 14 50 19

Nam Con Son Basin Province (Eocene-Miocene Composite TPS)

Oligocene-Miocene

Reservoirs AU 1.0

Oil 146 321 643 1,192 685 1,165 2,376 4,524 2,547 38 79 151 85

Gas 1,800 6,196 11,488 19,899 12,053 190 353 616 371

South China Sea Platform (Miocene TPS)

Dangerous GroundsReed Bank AU 1.0

Oil 703 764 2,192 5,380 2,522 3,058 8,889 22,683 10,370 58 168 437 197

Gas 4,217 4,609 13,151 32,381 15,149 260 756 1,928 881

Thai Basin Province (Eocene-Miocene Composite TPS)

Pattani Trough AU 1.0

Oil 80 386 615 946 634 2,406 3,939 6,200 4,071 66 109 173 113

Gas 787 3,739 6,055 9,419 6,253 148 242 379 250

Offshore Western Cenozoic

Rifts AU 1.0

Oil 181 152 479 1,347 578 942 3,041 8,812 3,716 26 84 247 103

Gas 257 136 426 1,360 543 5 17 55 22

Thai Cenozoic Basins Province (Eocene-Miocene Composite TPS)

Onshore Cenozoic Rifts AU 1.0

Oil 76 162 362 727 391 104 240 503 263 2 5 10 5

Gas 136 123 321 804 372 2 5 13 6

Palawan Shelf Province (Eocene-Miocene Composite TPS)

Eocene-Miocene

Reservoirs AU 1.0

Oil 101 84 226 609 270 54 147 417 179 2 5 13 6

Gas 514 319 984 3,035 1,229 10 30 94 38

Tarakan Basin (Neogene TPS)

Deltaic AU 1.0

Oil 38 22 64 198 81 32 96 307 123 1 3 10 4

Gas 406 573 1,310 2,803 1,447 7 16 36 18

Turbidite AU 1.0

Oil 235 100 380 1,421 516 311 1,213 4,674 1,673 10 38 151 54

Gas 2,376 2,076 6,441 17,361 7,668 24 78 223 95

Mangkalihat Carbonates 

AU 1.0

Oil 71 14 64 370 110 83 380 2,274 675 2 12 71 21

Gas 590 162 710 3,343 1,089 4 16 76 25

Sulu Sea Province (Miocene TPS)

Sandakan Reservoirs AU 1.0

Oil 178 58 231 997 339 84 345 1,536 515 3 11 53 18

Gas 2,448 2,211 6,907 18,205 8,159 26 84 234 101

Baram Delta/Brunei-Sabah Basin Province (Brunei-Sabah TPS)

Brunei-Sabah Deltaics AU 1.0

Oil 67 350 608 1,012 635 1,208 2,165 3,678 2,269 23 41 70 43

Gas 444 2,905 5,130 8,618 5,366 90 160 270 168

Brunei-Sabah Turbidites AU 1.0

Oil 551 1,766 3,448 6,180 3,643 4,866 9,900 18,563 10,581 91 188 358 202

Gas 1,352 3,384 7,515 15,100 8,159 128 290 594 316
Total Petroleum Systems 

(TPS) 

and Assessment Units (AU)

AU

probability

Field

type

Largest

expected

field size

Total Undiscovered Resources

Oil (MMBO) Gas (BCFG) NGL (MMBNGL)

F95 F50 F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean

Greater Sarawak Basin Province (Sarawak Basin TPS)

Central Luconia AU 1.0

Oil – 0 0 0 0 0 0 0 0 0 0 0 0

Gas 2,492 11,849 20,048 32,212 20,759 318 542 878 562

Balingian AU 1.0

Oil 80 361 618 1,013 643 1,435 2,529 4,233 2,641 27 48 81 50

Gas 687 2,340 4,189 7,169 4,392 132 243 425 256

East Natuna Carbonate AU 1.0

Oil – 0 0 0 0 0 0 0 0 0 0 0 0

Gas 1,913 4,729 9,646 18,038 10,281 126 260 494 278

Malay Basin Province (Oligocene-Miocene Composite TPS)

Main Malay-Tho Chu AU 1.0

Oil 71 240 430 732 450 893 1,658 2,945 1,756 11 21 37 22

Gas 1,158 4,200 7,661 13,049 8,008 87 160 275 167

Khmer Trough AU 1.0

Oil 82 60 179 493 214 215 681 1,974 835 3 8 25 10

Gas 535 415 1,259 3,346 1,489 8 26 71 31

Barito Basin (Eocene-Miocene Composite TPS)

Barito Foredeep Structures

AU 1.0

Oil 84 20 94 460 146 32 160 816 256 1 3 16 5

Gas 997 589 2,108 6,444 2,617 9 32 100 40

Central Sumatra Basin Province (Brown Shale-Sihapas TPS)

Pematang/Sihapas

Siliciclastics AU 1.0

Oil 14 84 142 233 148 70 133 240 141 6 12 23 13

Gas 99 85 222 562 259 2 5 12 6

East Java Basin (Eocene-Miocene Composite TPS)

East Java Carbonates AU 1.0

Oil 190 173 435 1,146 514 1,031 2,639 7,128 3,154 32 82 224 99

Gas 1,742 3,049 6,319 12,670 6,879 68 142 288 155

East Java Siliciclastics AU 1.0

Oil 294 633 1,400 2,816 1,522 1,310 2,925 5,984 3,192 67 151 311 165

Gas 2,358 8,286 17,078 32,285 18,264 613 1,291 2,471 1,381

Kutei Basin TPS

Kutei Basin Deltaics AU 1.0

Oil 32 91 160 269 168 471 847 1,464 892 5 9 16 10

Gas 952 1,299 3,056 6,652 3,401 58 143 331 162

Kutei Basin Turbidites AU 1.0

Oil 615 1,371 2,851 5,393 3,047 9,643 20,104 38,035 21,478 101 216 423 233

Gas 2,471 11,212 19,416 31,896 20,230 187 328 546 342

North Sumatra Basin (Bampo-Cenozoic TPS)

North Sumatra AU 1.0

Oil 12 48 77 119 79 288 478 763 495 5 10 17 10

Gas 183 534 934 1,570 977 36 66 121 71

Mergui Basin AU 1.0

Oil 169 71 280 1,018 374 423 1,711 6,434 2,338 8 33 137 48

Gas 1,493 2,796 6,486 13,524 7,096 188 461 1,031 516

Northwest Java Basin (Eocene-Miocene Composite TPS)

Sunda-Asri Basins AU 1.0

Oil 31 90 161 274 169 152 279 495 296 5 9 16 9

Gas 100 80 224 581 262 0 1 3 1

Ardjuna Basin AU 1.0

Oil 46 73 152 310 166 326 692 1,487 772 12 28 64 32

Gas 378 625 1,350 2,729 1,474 15 33 71 36

Biliton-Vera Basins AU 1.0

Oil 116 136 348 797 391 606 1,588 3,818 1,819 23 63 163 74

Gas 90 8 41 408 106 0 1 10 3

Penyu-West Natuna Basin Province (Oligocene-Miocene Composite TPS)

Gabus-Udang-Urang

Sandstones AU 1.0

Oil 24 27 66 150 74 109 284 699 329 1 4 10 5

Gas 153 598 1,048 1,754 1,094 24 43 72 45

South Sumatra Basin (Lahat/Talang Akar-Cenozoic TPS)

South Sumatra AU 1.0

Oil 82 133 321 681 353 537 1,338 2,967 1,491 11 28 65 32

Gas 639 1,398 3,112 6,194 3,367 48 110 228 120

Total Conventional

 Resources 8,922 19,541 41,558 21,632 128,908 272,848 557,051 298,761 3,828 8,270 17,216 9,099

Table 1. Southeast Asia assessment results.—Continued

[MMBO, million barrels of oil. BCFG, billion cubic feet of gas. MMBNGL, million barrels of natural gas liquids. Results shown are fully risked estimates. For gas accumulations, all liquids are included as NGL (natural gas liquids). Undiscovered gas resources are the sum of nonassociated and associated gas. F95 represents a 95-percent

chance of at least the amount tabulated; other fractiles are defined similarly. AU, assessment unit. AU probability is the chance of at least one accumulation of minimum

size within the AU. TPS, total petroleum system. Gray shading indicates not applicable. Largest expected oil field size in MMBO; gas field size is in BCFG]
is later than oil, gas is focused into the 

younger, post-rift clastic and carbonate 

reservoirs. Volumetrically, gas would be 

expected to be more prevalent than oil in 

these provinces where post-rift sources 

have achieved the appropriate thermal 

maturity for generation (Doust and 

Sumner, 2007).

The methodology for the assessment 

included a complete geologic framework 

description for each province mainly 

based on published literature and definition of petroleum systems and assessment 

units within these systems. Exploration 

and discovery history was a critical part 

of the methodology used to estimate 

sizes and numbers of undiscovered 

accumulations. In areas where there are 

no discoveries (for example, Phu Khanh 

Basin) geologic analogs were used as a 

basis for volumes of undiscovered oil 

and gas resources. Each assessment unit 

was assessed for undiscovered oil and 

nonassociated gas accumulations, and 

coproduct ratios were used to calculate 

the volumes of associated gas (gas in oil 

fields) and natural gas liquids.

Resource Summary

The USGS assessed undiscovered 

conventional oil and gas resources in 

assessment units within 23 geologic 

provinces (table 1). For conventional oil 

resources, the mean total is 21,632 million barrels of oil (MMBO), with a 

range from 8,922 to 41,558 MMBO; 

for undiscovered conventional gas the 

mean total is 298,761 billion cubic feet 

(BCFG), with a range from 128,908 

BCFG to 557,051 BCFG; and a mean 

total of 9,099 million barrels of natural 

gas liquids (MMBNGL), with a range 

from 3,828 to 17,216 MMBNGL.

Of the mean oil total of 

21,632 MMBO, about 70 percent is 

estimated to be in six provinces—Baram 

Delta/Brunei-Sabah Basin (mean of 

4,278 MMBO), Kutei Basin (mean of 

3,215 MMBO), South China Sea Platform (mean of 2,522 MMBO), East Java 

Basin (mean of 2,036 MMBO), Cuu 

Long Basin (mean of 1,735 MMBO), and 

Thai Basin (mean of 1,212 MMBO). In 

addition, several provinces are estimated 

to have potential oil volumes greater than 

500 MMBO—Northwest Java Basin 

(mean of 726 MMBO), Tarakan Basin 

(mean of 707 MMBO), Nam Con Son 

Basin (mean of 685 MMBO), Malay 

Basin (mean of 664 MMBO), Greater 

Sarawak Basin (mean of 643 MMBO), 

and Pearl River Mouth Basin (mean of 

608 MMBO).

For the mean undiscovered gas total 

of 298,761 BCFG, about 60 percent is 

estimated to be in six provinces—Kutei 

Basin (mean of 46,001 BCFG), Greater 

Sarawak Basin (mean of 38,073 BCFG), 

East Java Basin (mean of 31,489 BCFG), 

Baram Delta/Brunei-Sabah Basin (mean 

of 26,375 BCFG), South China Sea Platform (mean of 25,519 BCFG), and Nam 

Con Son Basin (mean of 14,600 BCFG). 

Several other provinces are estimated 

to have potential gas volumes greater 

than 10,000 BCFG—Thai Basin (mean 

of 14,583 BCFG), Phu Khanh Basin 

(mean of 13,040 BCFG), Tarakan Basin 

(mean of 12,675 BCFG), Song Hong 

Basin (mean of 12,266 BCFG), and 

Malay Basin (mean of 12,088 BCFG). 

Overall, the assessment indicates that 

(1) more than 90 percent of the undiscovered oil and gas resources are 

offshore, and (2) there is more than 

twice as much undiscovered gas resource 

(298,761 BCFG, or 49,794 MMBOE) 

than undiscovered oil resource 

(21,632 MMBO) in the provinces of 

southeast Asia using a barrels of oil 

equivalent conversion.

References

Doust, H., and Sumner, H.S., 2007, 

Petroleum systems in rift basins—a 

collective approach in southeast Asia 

basins: Petroleum Geoscience, v. 13, 

p. 127–144.

Hall, R., 2009, Hydrocarbon basins in 

SE Asia: understanding why they are 

there: Petroleum Geoscience, v. 15, 

p. 131–146.

Hall, R., van Hattum, M.W.A., and Spakman, Wim, 2008, Impact of India—

Asia collision on SE Asia: the record 

in Borneo: Tectonophysics, v. 451, 

p. 366–389.

Hutchinson, C.S., 2004, Marginal basin 

evolution: the southern South China 

Sea: Marine and Petroleum Geology, 

v. 21, p. 1129–1148.

Morley, C.K., 2001, Combined escape 

tectonics and subduction roll-backbackarc extension: a model for the 

Tertiary rift basins in Thailand, Malaysia, and Laos: Journal of Geological 

Society of London, v. 158, p. 461–474.

Morley, C.K., 2002, A tectonic model 

for the Tertiary evolution of strike-slip 

faults and rift basins in SE Asia: Tectonophysics, v. 347, p. 89–215.

Todd, S.P., Dunn, M.E., and Barwise, 

A.J.G., 1997, Characterizing petroleum 

charge systems in the Tertiary of SE 

Asia, in Fraser, A.J., Matthews, S.J., 

and Murphy, R.W., eds., Petroleum 

geology of Southeast Asia: Geological 

Society of London Special Publication 

v. 126, p. 25–47.

For Further Information

Supporting studies of the geologic 

models and the methodology used in 

the assessment of Southeast Asia Basins 

are in progress. Assessment results are 

available at the USGS Energy Program 

website, http://energy.cr.usgs.gov/oilgas/.

Southeast Asia Provinces 

Assessment Team: 

Christopher J. Schenk (Task Leader; 

schenk@usgs.gov), Michael E. Brownfield, Ronald R. Charpentier, Troy A. 

Cook, Timothy R. Klett, Mark A. Kirschbaum, Janet K. Pitman, and Richard M. 

Pollastro.