National and Global Petroleum Assessment

Assessment of Continuous Oil and Gas Resources in the 

San Jorge Basin Province, Argentina, 2017

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

resources of 78 million barrels of oil and 8.9 trillion cubic feet of gas in the San Jorge Basin Province, Argentina.

Introduction

The U.S. Geological Survey (USGS) completed an assessment 

of undiscovered, technically recoverable continuous oil and gas 

resources within the San Jorge Basin Province of Argentina (fig. 1). 

The structural configuration of the San Jorge Basin is the result of 

several phases of extension beginning in the Permian–Triassic related 

to the initial oblique rifting of South America from Africa and ending 

with final continental breakup and separation in late Early Cretaceous 

(Macdonald and others, 2003). Episodes of extension formed a series 

of east-west to northwest-southeast trending normal faults that define 

a deep central basin with shallower basin margins to the north and 

south (Fitzgerald and others, 1990; Sylwan, 2001; Foix and others, 

2012; Paredes and others, 2013). Sediments deposited during the 

Late Jurassic–Early Cretaceous extension and thermal sag are mainly 

nonmarine fluvial and lacustrine sandstones, siltstones, and shales 

that include the principal petroleum source rocks in the province. 

Neogene compression related to Andean subduction inverted some 

extensional structures in a narrow band in the basin forming the 

nearly north-south trending San Bernardo fold belt (fig. 1).

Total Petroleum Systems and Assessment Units

For the San Jorge Basin Province, the USGS defined two 

total petroleum systems (TPSs): the D-129 Lacustrine TPS and the 

Callovian–Aptian Lacustrine Composite TPS (Rodriguez and Littke, 

2001; Legarreta and Villar, 2011). The D-129 Lacustrine TPS was 

defined by the presence of thermally mature Hauterivian–Aptian 

organic-rich lacustrine shales of the D-129 Formation. These shales 

have total organic carbon values as much as 4 weight percent and a 

maximum thickness of 2,000 meters. Within this TPS are the D-129 

Lacustrine Shale Oil Assessment Unit (AU) and the D-129 Lacustrine Shale Gas AU. The geologic model for these AUs is for recoverable oil or gas to have been retained within the D-129 Formation 

lacustrine shales following petroleum migration into conventional 

traps.

The Callovian–Aptian Lacustrine Composite TPS was 

defined to account for potential tight-gas resources sourced by 

lacustrine organic-rich shales of the Callovian–Berriasian Aguada 

Bandera Formation and lacustrine shales of the Hauterivian–Aptian 

D-129 Formation (Legarreta and Villar, 2011). In this composite 

TPS, total organic carbon values are as much as 4 weight percent, 

and maximum thickness of the shale interval is about 600 meters. 

The Eastern San Jorge Tight Gas AU and the Western San Jorge 

Tight Gas AU are within this TPS. The geologic model is for recoverable gas to have been trapped in a low-permeability matrix of alluvial, fluvial, and marginal lacustrine sandstones of the Neocomian 

synrift Matasiete Formation and in overlying sandstones of the 

Mina del Carmen Formation.

Figure 1. Location of the San Jorge Basin Province, Argentina, 

and the four assessment units (AUs) defined in this study.

Assessment input data for four continuous AUs are shown 

in table 1. Well drainage areas, estimated ultimate recoveries, and 

success ratios were guided by U.S. shale-oil, shale-gas, and tightgas analogs.

Undiscovered Resources Summary

The USGS quantitatively assessed undiscovered, technically 

recoverable continuous oil and gas resources within the San Jorge 

Basin Province (table 2). The estimated mean totals for continuous 

oil and gas resources are 78 million barrels of oil (MMBO) with an 

F95–F5 range from 17 to 180 MMBO; 8,893 billion cubic feet of gas 

(BCFG), or 8.9 trillion cubic feet of gas, with an F95–F5 range from 

1,802 to 20,869 BCFG; and 67 million barrels of natural gas liquids 

(MMBNGL) with an F95–F5 range from 13 to 165 MMBNGL.

For the mean total continuous gas resources of 8,893 BCFG, 

3,440 BCFG (39 percent) are estimated to be shale-gas 

resources, and 5,453 BCFG (61 percent) are estimated to be tightgas resources.

–72° –70° –68° –66° –64°

–44°

–46°

–48°

Rawson

Puerto

Aisén Comodoro Rivadavia

ARGENTINA

CHILE

SOUTH

ATLANTIC

OCEAN

GOLFO

SAN JORGE

LAGO

MUSTERS

LAGO

COLHUÉ

HUAPI

0 50 100 KILOMETERS

0 50 100 MILES

Source: U.S. Department of the Interior National Park Service

EXPLANATION

Western San Jorge Tight Gas AU

San Jorge Basin Province boundary

San Bernardo fold belt

D-129 Lacustrine Shale Gas AU

Eastern San Jorge Tight Gas AU

D-129 Lacustrine Shale Oil AU

BRA

BOL

URY

PRY

PER

CHL

ARG

COL

VEN GUYSUR

GUF

ECU

SOUTH

ATLANTIC

OCEAN

SOUTH

PACIFIC

OCEAN

Map

area

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2017–3043

July 2017
Table 1. Key assessment input data for four assessment units in the San Jorge Basin Province, Argentina.

[AU, assessment unit; %, percent; EUR, estimated ultimate recovery per well; MMBO, million barrels of oil; BCFG, billion cubic feet of gas. EUR, well drainage area, 

and success ratios 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 D-129 Lacustrine Shale Oil AU D-129 Lacustrine Shale Gas AU

Minimum Mode Maximum Calculated mean Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 1,600 266,500 533,000 267,033 1,200 846,600 2,822,000 1,223,267

Average drainage area of wells (acres) 80 160 240 160 40 80 120 80

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

Average EUR (MMBO, oil; BCFG, gas) 0.04 0.08 0.3 0.092 0.1 0.4 1.2 0.441

AU probability 1.0 1.0

Assessment input data Eastern San Jorge Tight Gas AU Western San Jorge Tight Gas AU

Minimum Mode Maximum Calculated mean Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 800 1,411,000 2,822,000 1,411,267 800 554,500 1,109,000 554,767

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, gas) 0.1 0.4 1.2 0.441 0.1 0.4 1.2 0.441

AU probability 1.0 1.0

Table 2. Assessment results for four continuous assessment units in the San Jorge Basin Province, Argentina.

[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. 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

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

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

D-129 Lacustrine Total Petroleum System

D-129 Lacustrine Shale Oil AU 1.0 Oil 17 66 180 78 12 49 137 58 0 1 2 1

D-129 Lacustrine Shale Gas AU 1.0 Gas 643 2,760 8,188 3,382 6 27 85 34

Callovian–Aptian Lacustrine Composite Total Petroleum System

Eastern San Jorge Tight Gas AU 1.0 Gas 825 3,339 9,011 3,921 5 20 56 23

Western San Jorge Tight Gas AU 1.0 Gas 322 1,299 3,533 1,532 2 8 22 9

Total undiscovered continuous resources 17 66 180 78 1,802 7,447 20,869 8,893 13 56 165 67

References Cited

Fitzgerald, M.G.; Mitchum, R.M., Jr.; Uliana, M.A.; and Biddle, K.T., 1990, Evolution of the San Jorge Basin, Argentina: American 

Association of Petroleum Geologists Bulletin, v. 74, no. 6, p. 879–920.

Foix, Nicolás, Paredes, J.M., and Giacosa, R.E., 2012, Upper Cretaceous–Paleocene extensional phase in the Golfo San Jorge basin 

(Argentina)—Growth fault model, paleoseismicity and paleostress analysis: Journal of South American Earth Sciences, v. 33, no. 1, 

p. 110–118.

Legarreta, Leonardo, and Villar, H.J., 2011, Geological and geochemical keys of the potential shale resources, Argentina basins: 

American Association of Petroleum Geologists, Search and Discovery Article No. 80196, November 7, 2011, 21 p., accessed 

March 21, 2017, at http://www.searchanddiscovery.com/pdfz/documents/2011/80196legarreta/ndx_legarreta.pdf.html.

Macdonald, David; Gomez-Perez, Irene; Franzese, Juan; Spalletti, Luis; Lawver, Lawrence; Gahagan, Lisa; Dalziel, Ian; Thomas, 

Chris; Trewin, Nigel; Hole, Malcolm; and Paton, Douglas, 2003, Mesozoic break-up of SW Gondwana—Implications for regional 

hydrocarbon potential of the southern South Atlantic: Marine and Petroleum Geology, v. 20, nos. 3–4, p. 287–308.

Paredes, J.M., Plazibat, S.G., Crovetto, Carolina, Stein, Julián, Cayo, Eric, and Schiuma, Ariel, 2013, Fault kinematics and depocenter 

evolution of oil-bearing, continental successions of the Mina del Carmen Formation (Albian) in the Golfo San Jorge Basin, 

Argentina: Journal of South American Earth Sciences, v. 46, p. 63–79.

Rodriguez, J.F.R., and Littke, Ralf, 2001, Petroleum generation and accumulation in the Golfo San Jorge Basin, Argentina—A Basin 

modeling study: Marine and Petroleum Geology, v. 18, no. 9, p. 995–1028.

Sylwan, C.A., 2001, Geology of the Golfo San Jorge Basin, Argentina: Journal of Iberian Geology, v. 27, p. 123–157.

For More Information

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

San Jorge Basin Province Assessment Team

Christopher J. Schenk, Tracey J. Mercier, Sarah J. Hawkins, Marilyn E. Tennyson, Kristen R. Marra, Thomas M. Finn, Phuong A. Le, 

Michael E. Brownfield, Heidi M. Leathers-Miller, and Cheryl A. Woodall

ISSN 2327-6916 (print) ISSN 2327-6932 (online) https://doi.org/10.3133/fs20173043