U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2018–3040

August 2018

National and Global Petroleum Assessment

Assessment of Undiscovered Continuous Oil Resources of 

the East Gobi, Nyalga, Tamtsag-Hailar, Erlian, and Yingen 

Basins of Mongolia and China, 2018

Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean continuous resources of 1.1 billion barrels of oil and 674 billion cubic feet of associated gas in the East Gobi, Nyalga, Tamtsag-Hailar, Erlian, and Yingen 

basins of Mongolia and China.

Introduction

The U.S. Geological Survey (USGS) quantitatively assessed the 

potential for undiscovered technically recoverable continuous (unconventional) shale-oil resources in the East Gobi, Nyalga, Tamtsag-Hailar, 

Erlian, and Yingen basins of Mongolia and China (fig. 1). Middle Jurassic 

and Late Jurassic–Early Cretaceous extension formed a regional system 

of extensional basins which were filled with synrift nonmarine facies 

(Changsong and others, 2001; Meng, 2003; Meng and others, 2003; 

Wilhem and others, 2012). Following cessation of rifting, a thermal sag 

phase led to increased accommodation space and deposition, resulting in 

local source-rock maturation and oil migration. The sag phase of deposition was interrupted by regional compression, uplift, and erosion in the 

Late Cretaceous, which inverted many of the extensional structures, and 

largely curtailed the thermal maturation of source rocks.

Each of these five basins considered in this study contains groups of 

basins, or subbasins. For potential shale-oil resources to be assessed in a 

subbasin, a self-sourced shale reservoir must have Type I or Type II kerogen, 

have greater than 2 weight percent total organic carbon, have greater 

than 15 meters of organic-rich source rock, and be within the thermal 

windows for oil or gas generation. In these subbasins, the limiting 

geologic factor appears to be the level of thermal maturation, as the 

thermal threshold for oil generation was not reached in many subbasins, 

which are not shown in figure 1. This assessment focused on the subset 

of subbasins that are interpreted to have entered the oil-generation 

window based on published information.

Total Petroleum Systems and Assessment Units

For potential continuous oil resources, the USGS defined 

five total petroleum systems (TPSs) and a shale-oil assessment unit 

(AU) within each of the five TPSs. The AUs are the East Gobi Basin 

Zuunbayan Shale Oil AU in the East Gobi Basin Zuunbayan TPS, 

the Nyalga Basin Khuren Dukh Shale Oil AU in the Nyalga Basin 

Khuren Dukh TPS, the Tamtsag-Hailar Basin Nantun Shale Oil AU 

in the Tamtsag-Hailar Basin Nantun TPS, the Erlian Basin Upper 

Aershan-Lower Tengger Shale Oil AU in the Erlian Basin Upper 

Aershan-Lower Tengger Shale Oil TPS, and the Yingen Basin 

Bayingebi Shale Oil AU in the Yingen Basin Bayingebi TPS. Each 

AU area encompasses the area of those subbasins that are interpreted 

to have thermally mature source rocks given the available information. 

Not all of the subbasins within a basin have resource potential. In 

the subbasins within these five basins, petroleum source rocks are 

organic-rich, deep-water lacustrine shales (Traynor and Sladen, 1995; 

Graham and others, 2001; Johnson and others, 2003; Johnson, 2004; 

Prost, 2004; Ding and others, 2015; Hasagawa and others, 2018; Luo 

and others, 2018). Source rocks are mainly Type I kerogen (with minor 

Type III kerogen), organic carbon content is as much as 10 weight 

percent, hydrogen index values are as much as 600 milligrams of 

hydrocarbon per gram of organic carbon, and thickness is as much as 

700 meters. The uncertainty on the potential production area of the 

assessment unit (table 1) reflects the uncertainty on the extent of source-rock 

facies within the grabens, level of thermal maturation of the source rocks, 

and retention of oil following compressional deformation.

Assessment input data are summarized in table 1. Input data for 

drainage areas of wells, success ratios, and estimated ultimate recoveries 

are from geologic analogs in the United States.

Undiscovered Resources Summary

The USGS quantitatively assessed shale oil and associated gas 

resources in five assessment units (table 2) in the East Gobi, Nyalga, 

Tamtsag-Hailar, Erlian, and Yingen basins of Mongolia and China. For 

undiscovered, technically recoverable continuous resources, the estimated 

mean totals are 1,121 million barrels of shale oil (MMBO), or 1.1 billion 

barrels of oil, with an F95–F5 range from 0 to 2,941 MMBO; 674 billion 

cubic feet of associated gas (BCFG) with an F95–F5 range from 0 to 1,789 

BCFG; and 2 million barrels of natural gas liquids (MMBNGL) with an F95–

F5 range from 0 to 7 MMBNGL. Of the mean estimated shale-oil resource 

of 1,121 MMBO, about 75 percent is in the Erlian basin (515 MMBO or 46 

percent) and Tamtsag-Hailar basin (326 MMBO or 29 percent).

EXPLANATION

East Gobi Basin Zuunbayan Shale Oil AU

Nyalga Basin Khuren Dukh Shale Oil AU

Tamtsag-Hailar Basin Nantun Shale Oil AU

Erlian Basin Upper Aershan-Lower

 Tengger Shale Oil AU

Yingen Basin Bayingebi Shale Oil AU

0 150 300 MILES

0 300 KILOMETERS 150

Base map from U.S. Department of the Interior National Park Service

YELLOW SEA

 LAKE

BAIKAL

100° E 105° E 110° E 115° E 120° E

55° N

50° N

45° N

40° N

35° N

CHINA

RUSSIA

MONGOLIA

Map area

MNG

CHN

PRK

KOR

JPN

RUS

Figure 1. Map showing the five continuous assessment units (AUs) 

in the East Gobi, Nyalga, Tamtsag-Hailar, Erlian, and Yingen basins of 

Mongolia and China.
Table 1. Key input data for five continuous assessment units (AUs) in the East Gobi, Nyalga, Tamtsag-Hailar, Erlian, and Yingen basins of Mongolia and China.

[AU, assessment unit; %, percent; EUR, estimated ultimate recovery per well; MMBO, million barrels of oil. Well drainage area, success ratio, and EUR are defined partly using 

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

Assessment input data—

Continuous AUs

East Gobi Basin Zuunbayan Shale Oil AU Nyalga Basin Khuren Dukh Shale Oil AU

Minimum Mode Maximum Calculated mean Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 200 891,000 1,782,000 891,067 200 215,000 431,000 215,400

Average drainage area of wells (acres) 60 100 140 100 60 100 140 100

Success ratio (%) 10 40 80 43.3 10 40 80 43.3

Average EUR (MMBO) 0.01 0.04 0.15 0.046 0.01 0.04 0.1 0.043

AU probability 0.9 0.7

Assessment input data—

Continuous AUs

Tamtsag-Hailar Basin Nantun Shale Oil AU Erlian Basin Upper Aershan-Lower Tengger Shale Oil AU

Minimum Mode Maximum Calculated mean Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 200 1,088,000 2,176,000 1,088,067 200 1,974,000 3,948,000 1,974,067

Average drainage area of wells (acres) 60 100 140 100 60 100 140 100

Success ratio (%) 10 50 90 50 10 40 80 43.3

Average EUR (MMBO) 0.01 0.06 0.2 0.067 0.01 0.06 0.2 0.067

AU probability 0.9 0.9

Assessment input data—

Continuous AU

Yingen Basin Bayingebi Shale Oil AU

Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 200 648,000 1,296,000 648,067

Average drainage area of wells (acres) 60 100 140 100

Success ratio (%) 10 40 70 40

Average EUR (MMBO) 0.01 0.04 0.15 0.046

AU probability 0.8

Table 2. Results for five continuous assessment units (AUs) in the East Gobi, Nyalga, Tamtsag-Hailar, Erlian, and Yingen basins of Mongolia and China.

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

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

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

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

East Gobi Basin Zuunbayan Total Petroleum System

East Gobi Basin Zuunbayan Shale Oil AU 0.9 Oil 0 130 414 158 0 77 252 95 0 0 1 0

Nyalga Basin Khuren Dukh Total Petroleum System

Nyalga Basin Khuren Dukh Shale Oil AU 0.7 Oil 0 23 81 28 0 14 49 17 0 0 0 0

Tamtsag-Hailar Basin Nantun Total Petroleum System

Tamtsag-Hailar Basin Nantun Shale Oil AU 0.9 Oil 0 271 845 326 0 160 514 196 0 1 2 1

Erlian Basin Upper Aershan-Lower Tengger Shale Oil Total Petroleum System

Erlian Basin Upper Aershan-Lower Tengger 

Shale Oil AU 0.9 Oil 0 426 1,335 515 0 252 813 309 0 1 3 1

 Yingen Basin Bayingebi Total Petroleum System

Yingen Basin Bayingebi Shale Oil AU 0.8 Oil 0 77 266 94 0 45 161 57 0 0 1 0

Total undiscovered continuous resources 0 927 2,941 1,121 0 548 1,789 674 0 2 7 2

References Cited

Changsong, L., Eriksson, K., Sitian, L., Yongxian, W., Jianye, R., and Yanmei, Z., 

2001, Sequence architecture, depositional systems, and controls on development of 

lacustrine basin fills in part of the Erlian basin, northeast China: American Association of Petroleum Geologists Bulletin, v. 85, no. 11, p. 2017–2043.

Ding, X., Liu, G., Zha, M., Huang, Z., Gao, C., Wang, P., Qu, J., Lu, X., and Chen, Z., 

2015, Characteristics and origin of lacustrine source rocks in the Lower Cretaceous, 

Erlian Basin, northern China: Marine and Petroleum Geology, v. 66, pt. 4, p. 939–955.

Graham, S.A., Hendrix, M.S., Johnson, C.L., Badamgarav, D., Badarch, G., Amory, J., 

Porter, M., Barsbold, R., Webb, L.E., and Hacker, B.R., 2001, Sedimentary record 

and tectonic implications of Mesozoic rifting in southeast Mongolia: Geological 

Society of America Bulletin, v. 113, no. 12, p. 1560–1579.

Hasegawa, H., Ando, H., Hasebe, N., Ichinnorov, N., Ohta, T., Hasegawa, T., Yamamoto, 

M., Li, G., Erdenetsogt, B.-O., Heimhofer, U., Murata, T., Shinya, H., Enerel, G., 

Oyunjargal, G., Munkhtsetseg, O., Suzuki, N., Irino, T., and Yamamoto, K., 2018, 

Depositional ages and characteristics of Middle–Upper Jurassic and Lower Cretaceous lacustrine deposits in southeastern Mongolia: Island Arc, v. 27, no. 3, p. 1–17. 

Johnson, C.L., 2004, Polyphase evolution of the East Gobi basin—Sedimentary 

and structural records of Mesozoic–Cenozoic intraplate deformation in Mongolia: Basin Research, v. 16, no. 1, p. 79–99.

Johnson, C.L., Greene, T.J., Zinniker, D.A., Moldowan, J.M., Hendrix, M.S., and 

Carroll, A.R., 2003, Geochemical characteristics and correlation of oil and 

nonmarine source rocks from Mongolia: American Association of Petroleum 

Geologists Bulletin, v. 87, no. 5, p. 817–846.

Luo, Q., Zhong, N., Liu, Y., Qu, Y., and Ma, L., 2018, Organic geochemical 

characteristics and accumulation of the organic matter in the Jurassic to 

Cretaceous sediments of the Saihantala Sag, Erlian Basin, China: Marine and 

Petroleum Geology, v. 92, p. 855–867.

Meng, Q.-R., 2003, What drove late Mesozoic extension of the northern China–

Mongolia tract?: Tectonophysics, v. 369, nos. 3–4, p. 155–174.

Meng, Q.-R., Hu, J.-M., Jin, J.-Q., Zhang, Y., and Xu, D.-F., 2003, Tectonics 

of the late Mesozoic wide extensional basin system in the China–Mongolia 

border region: Basin Research, v. 15, no. 3, p. 397–415.

Prost, G.L., 2004, Tectonics and hydrocarbon systems of the East Gobi basin, 

Mongolia: American Association of Petroleum Geologists Bulletin, v. 88, no. 

4, p. 483–513.

Traynor, J.J., and Sladen, C., 1995, Tectonic and stratigraphic evolution of the 

Mongolian People’s Republic and its influence on hydrocarbon geology and 

potential: Marine and Petroleum Geology, v. 12, no. 1, p. 35–52.

Wilhem, C., Windley, B.F., and Stampfli, G.M., 2012, The Altaids of central 

Asia—A tectonic and evolutionary innovative review: Earth Science Reviews, 

v. 113, nos. 3–4, p. 303–341.

Mongolia and China Basins Assessment Team

Christopher J. Schenk, Tracey J. Mercier, Janet K. Pitman, Thomas M. Finn, 

Cheryl A. Woodall, Kristen R. Marra, Phuong A. Le, and Heidi M. Leathers-Miller

For More Information

Assessment results are also available at the USGS Energy Resources 

Program website at https://energy.usgs.gov.

ISSN 2327-6916 (print) ISSN 2327-6932 (online) https://doi.org/10.3133/fs20183040