U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2009–3028

October 2009

World Petroleum Resources Project

An Estimate of Recoverable Heavy Oil Resources 

of the Orinoco Oil Belt, Venezuela

Printed on recycled paper

The U.S. Geological Survey 

estimated a mean volume 

of 513 billion barrels of 

technically recoverable heavy 

oil in the Orinoco Oil Belt 

Assessment Unit of the East 

Venezuela Basin Province; 

the range is 380 to 652 billion 

barrels. The Orinoco Oil Belt 

Assessment Unit thus contains 

one of the world’s largest 

recoverable oil accumulations.

Figure 1. Map showing the location of the Orinoco Oil Belt Assessment Unit (blue line); the 

La Luna–Quercual Total Petroleum System and East Venezuela Basin Province boundaries are 

coincident (red line).

Venezuela Basin Province. Thrust faults 

associated with the fold belt caused lithospheric loading and basin formation, and 

the resulting burial placed Cretaceous and 

possibly older petroleum source rocks into 

the thermal window for the generation of 

oil (Parnaud and others, 1995; Summa and 

others, 2003). The oil migrated updip from 

the deeper basin to the shallow southern 

basin platform, forming the Orinoco Oil 

Belt. The oil is considered to be concentrated along a forebulge that formed south 

of the foreland basin (Bartok, 2003).

The heavy oil in the Orinoco Oil 

Belt AU is largely contained within fluvial, 

nearshore marine, and tidal sandstone reservoirs of the Miocene Oficina Formation 

(Kopper and others, 2001; Bejarano, 2006). 

Introduction

The Orinoco Oil Belt Assessment 

Unit (AU) of the La Luna−Quercual 

Total Petroleum System encompasses 

approximately 50,000 km2 of the East 

Venezuela Basin Province that is underlain by more than 1 trillion barrels of 

heavy oil-in-place (fig. 1) (Fiorillo, 

1987). As part of a program directed at 

estimating the technically recoverable oil 

and gas resources of priority petroleum 

basins worldwide, the U.S. Geological 

Survey (USGS) estimated the recoverable oil resources of the Orinoco Oil 

Belt AU. This estimate relied mainly on 

published geologic and engineering data 

for reservoirs (net oil-saturated sandstone 

thickness and extent), petrophysical 

properties (porosity, water saturation, 

and formation volume factors), recovery 

factors determined by pilot projects, and 

estimates of volumes of oil-in-place.

The East Venezuela Basin is a foreland basin south of a fold belt (fig. 2). The 

progressive west-to-east collision of the 

Caribbean plate with the passive margin of 

northern South America in the Paleogene 

and Neogene formed a thrust belt and foreland basin that together compose the East 

The reservoir sandstones, although porous 

and permeable, are characterized by several 

depositional sequences with considerable 

internal fluid-flow heterogeneity caused 

by juxtaposition of different facies and 

by shale barriers that reduce recovery 

efficiency. Sandstone reservoirs range in 

depth from 150 to 1,400 meters, and they 

contain heavy oil with a range of gravities from 4 to 16 degrees API. Viscosities 

are generally low, ranging from 2,000 to 

8,000 centipoises (Dusseault, 2001).

Methodology and Input Data

In addition to the standard USGS 

methodology for assessing continuous 

oil accumulations such as those in the 

VENEZUELA

BRAZIL

COLOMBIA

SURINAME

GUYANA

0 50 100 200 MILES

0 50 100 200 KILOMETERS

ST. LUCIA

BARBADOS

GRENADA

TRINIDAD

ARUBA

NETHERLANDS ANTILLES

ST. VINCENT AND

THE GRENADINES

CARIBBEAN SEA

PACIFIC

OCEAN

ATLANTIC

OCEAN

SOUTH

AMERICA

East Venezuela 

Basin Province

EXPLANATION

Orinoco Oil Belt Assessment Unit

East Venezuela Basin Province

70° 68° 66° 64° 62° 60° 58° 56°

14°

12°

10°

8°

6°

4°

A'

A
Figure 2. Schematic structural cross section of the East Venezuela Basin showing the updip position of the Orinoco Oil Belt 

relative to the deeper part of the East Venezuela Basin. Oil generated from thermally mature Cretaceous and possibly older source 

rocks in the deeper part of the basin migrated updip to form the accumulation in the Orinoco Oil Belt (after Jacome and others, 2003).

Orinoco Oil Belt (Crovelli, 2000), we 

used reservoir data, petrophysical data, 

oil-in-place estimates, and recovery factors taken from studies of the Orinoco 

Oil Belt to develop five other approaches 

for estimating recoverable resources and 

to adequately represent the geologic and 

engineering uncertainty in the assessment. Key data used in the assessment 

are summarized in table 1. The estimates 

of volumes of recoverable oil and associated gas reported here reflect the distribution of mean estimates obtained by the 

six methodologies applied to the Orinoco 

Oil Belt AU (table 2). 

Estimates of Original Oil-in-Place

A comprehensive study by Petroleos 

de Venezuela S.A. (PDVSA) established 

the magnitude of the original oil-in-place 

(OOIP) at 1,180 billion barrels of oil 

(BBO), a commonly cited estimate for 

the Orinoco Oil Belt (Fiorillo, 1987); 

PDVSA recently revised this value to 

more than 1,300 BBO (Gonzalez and 

others, 2006). In this study the median 

OOIP was estimated at 1,300 BBO 

and the maximum at 1,400 BBO. 

The minimum OOIP was estimated 

at 900 BBO, given the uncertainty of 

regional sandstone distribution and oil 

saturation (Fiorillo, 1987).

Estimates of Recovery Factor

Recovery factor, or that percentage of the OOIP that is determined 

to be technically recoverable, was 

estimated from what is currently 

known of the technology for recovery 

of heavy oil in the Orinoco Oil Belt 

AU and in other areas, particularly 

California, west Texas, and western 

Canada. The minimum recovery factor 

was estimated to be 15 percent, the 

recovery expected for cold production 

using horizontal wells. The median 

recovery factor was estimated to be 

45 percent, on the assumption that 

horizontal drilling and thermal recovery 

methods might be widely used. The 

maximum recovery factor was estimated to be 70 percent, on the assumption that other recovery processes, 

in addition to horizontal drilling and 

steam-assisted gravity drainage, might 

eventually be applied on a large scale 

in the Orinoco Oil Belt AU (Dusseault, 

2001; Curtis and others, 2002; Acasio 

and Regardiz, 2006; Fernandez and 

Bashbush, 2008).

SE

A A'

NW

EAST VENEZUELA BASIN

ORINOCO OIL BELT MAIN PRODUCING AREA

0

5

10

15

SEA LEVEL KILOMETERS

EXPLANATION

Jurassic and/or

 Paleozoic?

Pre-Cretaceous

 basement

Fault

Oil field

Middle Miocene

 to present

Lower Miocene

Cretaceous to Paleogene

 passive margin

VERTICAL EXAGGERATION X 5

0 25 50 KILOMETERS

0 15.6 31 MILES
Minimum Median Maximum

Orinoco oil-in-place (BBO) 900 1,300 1,400

Recovery factor (%) 15 45 70

Net oil-saturated sandstone thickness (ft) 1 150 350

Porosity (%) 20 25 38

Water saturation (%) 10 20 25

Formation volume factor 1.05 1.06 1.08

Gas/oil ratio (scf/bbl) 80 110 600

Table 1. Key input data for assessment of Orinoco Oil Belt Assessment Unit.

[%, percent; BBO, billion barrels of oil; ft, feet; scf/bbl, standard cubic foot per barrel]

Total Petroleum System 

(TPS)

and Assessment Unit

(AU)

Field

Type

Total Undiscovered Resources

Oil (BBO) Gas (TCFG) NGL (BBNGL)

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

La Luna–Querecual TPS

Orinoco Oil Belt AU Oil 380 512 652 513 53 122 262 135 0 0 0 0

Table 2. Orinoco Oil Belt Assessment Unit assessment results.

[BBO, billion barrels of oil; TCFG, trillion cubic feet of gas; NGL, natural gas liquids; BBNGL, billion barrels 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] 

Probability Distributions of 

Petrophysical and Reservoir 

Properties

Oil-saturated sandstones in the 

Orinoco Oil Belt AU are largely unconsolidated (Dusseault, 2001). The values 

used in the assessment for porosity, 

water saturation, net oil-saturated sandstone 

thickness, and formation volume factor are 

shown in table 1. Net thickness and extent 

of oil-saturated sandstone were obtained 

from a published map that resulted from 

a comprehensive PDVSA study of the 

Orinoco Oil Belt (Fiorillo, 1987).

Summary of Results

The assessment of technically 

recoverable heavy oil and associated gas 

resources is shown in table 2. The mean 

of the distribution of heavy oil resources 

is about 513 BBO, with a range from 

380 to about 652 BBO. The mean estimate 

of associated dissolved-gas resource is 

135 trillion cubic feet of gas (TCFG), 

with a range from 53 to 262 TCFG. 

No attempt was made in this study to 

estimate either economically recoverable 

resources or reserves within the Orinoco 

Oil Belt AU. Most important, these results 

do not imply anything about rates of heavy 

oil production or about the likelihood of 

heavy oil recovery. Also, no time frame 

is implied other than the use of reasonably 

foreseeable recovery technology.

References Cited

Acasio, Y., and Regardiz, K., 2006, 

Opportunity for a SAGD pilot test 

implementation in a zone in initial 

phase of operation, Ayacucho 

area, Orinoco Belt: World Heavy 

Oil Conference, Beijing, China, 

November 12–15, 2006, Proceedings, 

Paper 2006–771, 13 p.

Bartok, Peter, 2003, The peripheral bulge 

of the Interior Range of the Eastern 

Venezuela basin and its impact on 

oil accumulations, in Bartolini, C., 

Buffler, R.T., and Blickwede, J., eds., 

The Circum-Gulf of Mexico and the 

Caribbean—Hydrocarbon habitats, basin 

formation, and plate tectonics: American 

Association of Petroleum Geologists 

Memoir 79, Chap. 41, p. 925–936.

Bejarano, C., 2006, Tertiary stratigraphy 

and sedimentary environments of the 

oil bearing sands of the Orinoco Oil 

Belt, Venezuela, South America: World 

Heavy Oil Conference, Beijing, China, 

November 12–15, 2006, Proceedings, 

Paper 2006–770, 7 p.

Crovelli, R.A., 2000, Analytic resource 

assessment method for continuous 

(unconventional) oil and gas 

accumulations—The “ACCESS” 

method: U.S. Geological Survey 

Open-File Report 00–044, 34 p.

Curtis, Carl, Kopper, Robert, Decoster, 

Eric, Guzman-Garcia, Angel, Huggins, 

Cynthia, Knauer, Larry, Minner, Mike, 

Kupsch, Nathan, Linares, Luz M., 

Rough, Howard, and Waite, Mike, 2002, 

Heavy-oil reservoirs: Oilfield Review, 

Autumn 2002, Schlumberger Oilfield 

Services Company, p. 30–51.

Dusseault, M.B., 2001, Comparing 

Venezuelan and Canadian heavy oil 

and tar sands, in Canadian International Petroleum Conference, Calgary, 

Alberta, Canada, June 12–14, 2001, 

Canadian Institute of Mining, Metallurgy, and Petroleum, Proceedings, 

Paper 2001–061, 20 p.
Fernandez R., E.A., and Bashbush, J.L., 

2008, Horizontal alternating steam 

drive process for the Orinoco Heavy 

Oil Belt in eastern Venezuela: Society 

of Petroleum Engineers/Petroleum 

Society/Canadian Heavy Oil Association, 

Paper SPE/PS/CHOA 117689, 13 p.

Fiorillo, G., 1987, Exploration and evaluation of the Orinoco Oil Belt, in Meyer, 

R.F., ed., Exploration for heavy crude 

oil and natural bitumen: American 

Association of Petroleum Geologists 

Studies in Geology 25, p. 103–121.

Gonzalez, O., Ernandez, J., Chaban, F., 

and Bauza, L., 2006, Screening of suitable exploitation technologies on the 

Orinoco Oil Belt applying geostatistical 

methods: World Heavy Oil Conference, 

Beijing, China, November 12–15, 2006, 

Proceedings, Paper 2006–774, 12 p.

Jacome, M.I., Kusznir, Nick, Audemard, 

Felipe, and Flint, Steve, 2003, Tectonostratigraphic evolution of the Maturin 

foreland basin—Eastern Venezuela, 

in Bartolini, C., Buffler, R.T., and 

Blickwede, J., eds., The Circum-Gulf 

of Mexico and the Caribbean—

Hydrocarbon habitats, basin formation, and plate tectonics: American 

Association of Petroleum Geologists 

Memoir 79, Chap. 33, p. 735–749.

Kopper, Robert, Kupecz, Julie, Curtis, 

Carl, Cole, Tony, Dorn-Lopez, Donald, 

Copley, Jeffery, Munoz, Alberto, 

Caicedo, Vladimir, and Suter, John, 

2001, Reservoir characterization of 

the Orinoco Heavy Oil Belt; Miocene 

Oficina Formation, Zuata Field, Eastern 

Venezuelan Basin: Society of Petroleum 

Engineers, Paper SPE 69697, 16 p.

U.S. Geological Survey Orinoco Oil Belt 

Assessment Team:

Christopher J. Schenk, Troy A. Cook, Ronald R. 

Charpentier, Richard M. Pollastro, Timothy R. Klett, Marilyn E. 

Tennyson, Mark A. Kirschbaum, Michael E. Brownfield, and 

Janet K. Pitman.

For Further Information

A publication detailing the methodologies used in the 

Orinoco Oil Belt AU assessment is in progress. Assessment 

results are available at the USGS Energy Program website, 

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

Parnaud, Francois, Gou, Yves, Pascual, 

J.C., Truskowski, Irene, Gallango, 

Oswaldo, Passalacqua, Herminio, 

and Roure, F., 1995, Petroleum 

geology of the central part of the 

East Venezuelan Basin, in Tankard, 

A.J., Suarez, R., and Welsink, H.J., 

eds., Petroleum basins of South 

America: American Association of 

Petroleum Geologists Memoir 62, 

p. 741–755.

Summa, L.L., Goodman, E.D., 

Richardson, M., Norton, I.O., and 

Green, A.R., 2003, Hydrocarbon 

systems of northeastern Venezuela—

Plate through molecular scale-analysis 

of the genesis and evolution of the 

Eastern Venezuela Basin: Marine 

and Petroleum Geology, v. 20, 

p. 323–349.