National and Global Petroleum Assessment

Assessment of Continuous Gas Resources in the Khorat 

Plateau Province, Thailand and Laos, 2016

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2017–3023

May 2017

Using a geology-based assessment methodology, the U.S. Geological Survey assessed mean undiscovered, technically recoverable

resources of 2.3 trillion cubic feet of continuous gas in the Khorat Plateau Province of Thailand and Laos.

Introduction

The U.S. Geological Survey (USGS) completed a geologybased assessment of undiscovered, technically recoverable 

shale-gas and tight-gas resources in the Khorat Plateau Province 

of northeast Thailand and western Laos (fig. 1). The Khorat 

Plateau Province is part of Sundaland, a geologically complex 

continental area that consists of several terranes that originated 

from the northern margin of the supercontinent Gondwana and 

accreted to Eurasia from the late Paleozoic through the Mesozoic 

(Barber and others, 2011; Metcalfe, 2011; Morley, 2012; Hall, 

2013; Morley and others, 2013). Progressive accretion of several 

Gondwanan blocks resulted in a mosaic of terranes, suture zones, 

accretionary wedges, and arc rocks that record a complex geologic history that may have affected the development and preservation of viable petroleum systems. Petroleum source rocks were 

deposited in extensional basins formed in the late Carboniferous–

late Permian and Late Triassic (Booth and Sattayarak, 2011; 

Racey, 2011). Upper Carboniferous–upper Permian source rocks 

are marine shales, carbonaceous shales, and coals; Triassic source 

rocks are organic-rich, deep-basin lacustrine shales. Burial history modeling suggests that petroleum residing in potential tight 

(low permeability) sandstone or shale reservoirs entered the 

thermal window for dry gas during Late Jurassic–Early Cretaceous burial by more than 5 kilometers of Khorat Group rocks. 

Both source-rock intervals were exposed to several phases of 

deformation, uplift, and erosion that may have adversely affected 

the retention of gas in tight sandstones, siltstones, and shale reservoirs. This assessment quantifies the volumes of gas potentially 

retained within lacustrine shales of the Triassic Kuchinarai Group 

and gas potentially retained within tight-clastic reservoirs of the 

Triassic through Lower Cretaceous (Koysamran and ComrieSmith, 2011). Shows of gas from tight rock have been reported 

from wells in the Khorat Plateau Province (Booth, 1998; Malila, 

2011; Racey, 2011), but there are no reports of recoverable gas 

from shales (Chumkratoke and Dunn-Norman, 2015).

Total Petroleum Systems and Assessment Units

For the Khorat Plateau Province, the USGS defined two total 

petroleum systems. The Triassic Kuchinarai Total Petroleum System was defined to include gas that was generated and potentially 

retained within synrift lacustrine organic-rich shales of the Triassic 

Kuchinarai Group (fig. 2). The Khorat Kuchinarai Shale Gas 

Assessment Unit (AU), the Sakon Nakhon Kuchinarai Shale Gas 

AU, the Phu Phan Kuchinarai Shale Gas AU, and the Savannakhét 

Figure 1. Map showing the location and boundaries of the Khorat 

Plateau Province, Thailand and Laos, and the seven continuous 

assessment units (AUs) defined for this study.

Kuchinarai Shale Gas AU were defined within this TPS. The 

Upper Carboniferous–Triassic Composite Total Petroleum 

System was defined to include gas that is potentially retained 

within tight-clastic reservoirs of the Upper Triassic, Jurassic, 

and Cretaceous. The Khorat Basin Tight Gas AU, the Sakon 

Nakhon Basin Tight Gas AU, and the Savannakhét Basin Tight 

Gas AU were defined within this TPS. Assessment unit boundaries were developed using published maps depicting Permian 

and Triassic depocenters (Booth and Sattayarak, 2011). We 

102° 103° 104° 105° 106°

19°

18°

17°

16°

15°

14°

13°

CAMBODIA

THAILAND

LAOS VIETNAM

SOUTH

CHINA 

SEA

Tonlé 

Sap Lake

SAKON 

 NAKHON 

BASIN

KHORAT BASIN

Phu Phan

Uplift

SAVANNAKHÉT 

BASIN

INDIAN

OCEAN

Source: U.S. Department of the Interior

National Park Service

PHL

MMR

THA

CHN

KHM

VNM

LAO

Map

area

INDIAN

OCEAN

SOUTH

CHINA

SEA

0 80 KILOMETERS 40

0 40 80 MILES

EXPLANATION

Khorat Kuchinarai Shale Gas AU

Sakon Nakhon Kuchinarai Shale Gas AU

Phu Phan Kuchinarai Shale Gas AU

Khorat Basin Tight Gas AU

Sakon Nakhon Basin Tight Gas AU

Savannakhét Basin Tight Gas AU

Savannakhét Kuchinarai Shale Gas AU

Khorat Plateau Basin Province
Multistory, high-sinuosity fluvial channel sandstone with 

lateral accretion, Phra Wihan Formation of the Khorat Group 

near Ban Nong Khu, Thailand. Sandstone is 4.5 meters thick.

Figure 2. Stratigraphy of the Khorat Plateau Province, 

Thailand and Laos (modified from Koysamran and 

Comrie-Smith, 2011). Tertiary Cretaceous Jurassic Triassic Permian Carboniferous Devonian

Phu Phan

Uplift

Phu Tok Formation

Maha Sarakham Formation

Khok Kruat Formation

Phu Phan Formation

Sao Khua Formation

Phra Wihan Formation

Phu Kradung Formation

Upper Nam Phong Formation

Lower Nam Phong Formation

Huai Hin Lat Formation

Hua Na Kham Formation

Pha Nok Khao Formation

Nam Duk Formation

Si That Formation

Saraburi Group

Loei Group

Khorat Group Kuchinarai Group

Shale

Sandstone

Conglomerate

Limestone

Evaporite

Volcanics

Coal

Reservoir

Source

EXPLANATION

recognize that there were three episodes of basin formation in the province, 

but the AUs were named using the present geomorphic elements of Khorat 

Basin, Sakon Nakhon Basin, Phu Phan Uplift, and Savannakhét Basin. 

Assessment input data for seven continuous AUs are shown in table 1. 

Well drainage areas, estimated ultimate recoveries, and success ratios were 

taken from U.S. shale-gas and tight-gas analogs.

Undiscovered Resources Summary

In the Khorat Plateau Province, the USGS quantitatively assessed 

total mean undiscovered, technically recoverable shale-gas and tight-gas 

resources of 2,301 billion cubic feet of gas (BCFG), or 2.3 trillion cubic 

feet of gas, with an F95–F5 range from 0 to 9,268 BCFG and 17 million 

barrels of natural gas liquids (MMBNGL) with an F95–F5 range from 

0 to 67 MMBNGL (table 2). For undiscovered, technically recoverable 

shale-gas resources, the mean total is 586 BCFG with an F95–F5 range 

from 0 to 2,150 BCFG, and 6 MMBNGL with an F95–F5 range from 0 

to 19 MMBNGL. For undiscovered tight-gas resources, the mean total 

is 1,715 BCFG with an F95–F5 range from 0 to 7,118 BCFG and 11 

MMBNGL with an F95–F5 range from 0 to 48 MMBNGL. The wide 

ranges of estimated undiscovered gas resources reflect the level of geologic uncertainty on the retention of gas within tight clastic reservoirs and 

shale reservoirs given the tectonic history. For gas accumulations, zeros at 

F95 reflect the chance that continuous gas might not exist in the AU, and 

the geologic AU probability (risk) was estimated to be less than one.
Table 1. Key assessment input data for seven continuous assessment units in the Khorat Plateau Basin Province, Thailand and Laos.

[AU, assessment unit; %, percent; EUR, estimated ultimate recovery per well; BCFG, billion cubic feet of gas. EUR, well drainage area, and success ratios are from 

U.S. shale-gas and tight-gas analogs. The average EUR input is the minimum, median, maximum, and calculated mean. Shading indicates not applicable]

Assessment input data—

Continuous AUs

Khorat Kuchinarai Shale Gas AU Sakon Nakhon Kuchinarai Shale Gas AU

Minimum Mode Maximum Calculated mean Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 600 821,000 1,967,000 929,533 600 187,000 374,000 187,200

Average drainage area of wells (acres) 80 120 160 120 80 120 160 120

Success ratios (%) 10 50 90 50 10 50 90 50

Average EUR (BCFG) 0.04 0.1 0.8 0.138 0.04 0.1 0.8 0.138

AU probability 0.6 0.6

Assessment input data—

Continuous AUs

Phu Phan Kuchinarai Shale Gas AU Savannakhét Kuchinarai Shale Gas AU

Minimum Mode Maximum Calculated mean Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 600 675,000 1,351,000 675,533 600 249,000 498,000 249,200

Average drainage area of wells (acres) 80 120 160 120 80 120 160 120

Success ratios (%) 10 50 90 50 10 50 90 50

Average EUR (BCFG) 0.04 0.08 0.4 0.098 0.04 0.08 0.4 0.098

AU probability 0.6 0.5

Assessment input data—

Continuous AUs

Khorat Basin Tight Gas AU Sakon Nakhon Basin Tight Gas AU

Minimum Mode Maximum Calculated mean Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 600 1,303,000 12,408,000 4,570,533 600 371,000 2,081,000 817,533

Average drainage area of wells (acres) 40 80 120 80 40 80 120 80

Success ratios (%) 10 50 90 50 10 50 90 50

Average EUR (BCFG) 0.04 0.08 0.4 0.098 0.04 0.08 0.4 0.098

AU probability 0.5 0.5

Assessment input data—

Continuous AUs

Savannakhét Basin Tight Gas AU

Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 600 249,000 498,000 249,200

Average drainage area of wells (acres) 40 80 120 80

Success ratios (%) 10 50 90 50

Average EUR (BCFG) 0.04 0.08 0.4 0.098

AU probability 0.5

Lateral accretion surfaces and bedding in high-sinuosity fluvial channel sandstone of the Khorat Group along Highway 304, near kilometer 

marker 70. Sandstone is 5 meters thick.
ISSN 2327-6916 (print) ISSN 2327-6932 (online) https://doi.org/10.3133/fs20173023

For More Information

Assessment results are available at the USGS Energy Resources Program website at https://energy.usgs.gov.

Khorat Plateau Province Assessment Team

Christopher J. Schenk, Timothy R. Klett, Tracey J. Mercier, Thomas M. Finn, Marilyn E. Tennyson, Stephanie B. Gaswirth, 

Kristen R. Marra, Phuong A. Le, and Ronald M. Drake II

References Cited

Barber, A.J., Ridd, M.F., and Crow, M.J., 2011, The origin, 

movement, and assembly of the pre-Tertiary tectonic units of 

Thailand, in Ridd, M.F., Barber, A.J., and Crow, M.J., eds., 

The geology of Thailand: London, The Geological Society, 

p. 507–535.

Booth, J.E., 1998, The Khorat Plateau of NE Thailand—

Exploration history and hydrocarbon potential, in The Seapex 

Exploration Conference, 17th Offshore South East Asia 

Conference and Exhibition, Singapore, December 2–3, 1998, 

Proceedings: Southeast Asia Petroleum Exploration Society, 

p. 169–203, accessed December 19, 2016, at http://www.

seapex.org/document-download/. 

Booth, J.E., and Sattayarak, Nares, 2011, Subsurface 

Carboniferous–Cretaceous geology of NE Thailand, chap. 9 

of Ridd, M.F., Barber, A.J., and Crow, M.J., eds., The geology 

of Thailand: London, The Geological Society, p. 185–222.

Chumkratoke, C., and Dunn-Norman, S., 2015, Reservoir 

characteristics for unconventional shale play of Huai Hin Lat 

Formation in northeastern Thailand, in Society of Petroleum 

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(IATMI [Ikatan Ahli Teknik Perminyakan Indonesia]) Asia 

Pacific Oil & Gas Conference and Exhibition, October 20–22, 

2015, Nusa Dua, Bali, Indonesia, Proceedings: Society of 

Petroleum Engineers, SPE–76474 015–MS, 12 p.

Hall, Robert, 2013, The paleogeography of Sundaland and 

Wallacea since the Late Jurassic: Journal of Limnology, 

v. 72, no. 2, p. 1–17.

Koysamran, Suwisa, and Comrie-Smith, Nick, 2011, Basin 

modeling of Block L26/50, eastern Khorat Plateau, northeast 

Thailand, in The 4th Petroleum Forum—Approaching to 

the 21st Petroleum Concession Bidding Round, Chatuchak, 

Bangkok, Thailand, May 26–27, 2011, Proceedings: Department of Mineral Fuels, Ministry of Energy, p. 5–12, accessed 

April 11, 2017, at http://www.dmf.go.th/cms/assets/1/The%20

4th%20(DMF)%20Petroleum%20Forum%20Proceeding.pdf.

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Forum—Approaching to the 21st Petroleum Concession 

Bidding Round, Chatuchak, Bangkok, Thailand, May 26–27, 

2011, Proceedings: Department of Mineral Fuels, Ministry of 

Energy, 1 p., accessed December 19, 2016, at http://www.dmf.

go.th/cms/assets/1/The%204th%20(DMF)%20Petroleum%20

Forum%20Proceeding.pdf.

Metcalfe, Ian, 2011, Tectonic framework and Phanerozoic evolution of Sundaland: Gondwana Research, v. 19, no. 1, p. 3–21.

Morley, C.K., 2012, Late Cretaceous–Early Paleogene tectonic 

development of SE Asia: Earth Science Reviews, v. 115, 

no. 1–2, p. 37–75.

Morley, C.K., Ampaiwan, P., Thanudamrong, S., Kuenphan, N., 

and Warren, John, 2013, Development of the Khao Khwang 

fold and thrust belt—Implications for the geodynamic setting 

of Thailand and Cambodia during the Indosinian Orogeny: 

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M.F., Barber, A.J., and Crow, M.J., eds., The geology of 

Thailand: London, The Geological Society, p. 351–392.

Table 2. Assessment results for seven continuous assessment units in the Khorat Plateau Basin Province, Thailand and Laos.

[BCFG, billion cubic feet of gas; NGL, natural gas liquids; MMBNGL, million barrels of natural gas liquids. Results shown are fully risked estimates. For gas 

accumulations, all liquids are included in the NGL 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 correlation. Shading indicates not applicable]

Total petroleum systems 

and assessment units (AUs)

AU

probability

Accumulation

type

Total undiscovered resources

Gas (BCFG) NGL (MMBNGL)

F95 F50 F5 Mean F95 F50 F5 Mean

Triassic Kuchinarai Total Petroleum System

Khorat Kuchinarai Shale Gas AU 0.6 Gas 0 162 1,172 312 0 1 10 3

Sakon Nakhon Kuchinarai Shale Gas AU 0.6 Gas 0 33 233 62 0 0 2 1

Phu Phan Kuchinarai Shale Gas AU 0.6 Gas 0 105 554 162 0 1 5 1

Savannakhét Kuchinarai Shale Gas AU 0.5 Gas 0 0 191 50 0 0 2 1

Total shale-gas resources 0 300 2,150 586 0 2 19 6

Upper Carboniferous–Triassic Composite Total Petroleum System

Khorat Basin Tight Gas AU 0.5 Gas 0 0 5,801 1,389 0 0 36 8

Sakon Nakhon Basin Tight Gas AU 0.5 Gas 0 0 1,024 250 0 0 8 2

Savannakhét Basin Tight Gas AU 0.5 Gas 0 0 293 76 0 0 4 1

Total tight-gas resources 0 0 7,118 1,715 0 0 48 11

Total continuous resources 0 300 9,268 2,301 0 2 67 17