National and Global Petroleum Assessment Project

Assessment of Undiscovered Oil and Gas Resources of the 

Paris Basin, France, 2015

Using a geology-based assessment methodology, the 

U.S. Geological Survey estimated means of 222 million 

barrels of unconventional oil; 2,092 billion cubic feet of 

unconventional gas; 18 million barrels of conventional oil; 

and 47 billion cubic feet of conventional gas resources in 

the Paris Basin of France.

Introduction

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

the potential for undiscovered, technically recoverable oil and gas 

resources in the Paris Basin of France (fig. 1) as part of an effort 

to assess priority European basins. The Paris Basin composes part 

of the USGS Anglo-Paris Basin Province, but for this study, only 

the Paris Basin was evaluated for undiscovered conventional and 

unconventional (shale oil, shale gas, tight gas) oil and gas resources. 

More than 35 conventional oil and gas fields have been discovered in the Paris Basin since the 1950s, with the largest oil field, 

Chaunoy, discovered in 1983. The assessment of undiscovered 

conventional resources in these oil and gas fields is straightforward, 

due to the fields’ geology, along with their discovery and exploration history, and what is known of the Lower Jurassic source rocks. 

This study focuses on the geologic evaluation of unconventional 

(continuous) oil and gas source-reservoir rock systems and potential 

resources.

For conventional resources, the USGS defined a Mesozoic Reservoirs Assessment Unit (AU) to encompass petroleum that was generated from Lower Jurassic organic-rich shales, then migrated and 

was trapped in Triassic, Jurassic, and Lower Cretaceous reservoirs. 

Migration of petroleum across tens of kilometers occurred from the 

areas of thermally mature Lower Jurassic source rocks. In contrast to the conventional petroleum system, Lower Jurassic source 

rocks were evaluated for potential source-reservoir rock systems 

that retained moveable oil. For this assessment, an unconventional 

(continuous) source-reservoir rock system must: (1) contain greater 

than 2 weight percent total organic carbon (TOC), (2) be within the 

proper thermal maturity window for oil or gas generation, (3) have 

greater than 15 meters of organic-rich shale, and (4) contain Type 

I or Type II organic matter (Charpentier and Cook, 2011). After 

potential areas for assessment were defined, the tectonic history, 

thermal history, and timing of maturation and generation were used 

to evaluate the risk of retention of hydrocarbons within the source 

rock. The USGS defined a Toarcian-Domerian Continuous Oil AU 

(including the “schistes carton”) and a Lotharingian-Sinemurian 

Continuous Oil AU. The USGS also defined a Permo-Carboniferous 

Tight Gas AU, which involves coal-sourced gas that migrated 

locally into low-permeability, or “tight” fluvial sandstones within 

Permo-Carboniferous rift systems, similar to the Lower Saxony 

Basin of Germany (Wuestefeld and others, 2014). The presence of 

rifts, “tight” fluvial reservoirs, and coal-sourced gas are all highly 

uncertain in the Paris Basin, and the uncertainty is reflected in the 

F95 fractile of zero resource.

The assessment input data for three unconventional (continuous) 

AUs are shown in table 1.

Resource Summary

The USGS quantitatively assessed undiscovered oil and gas 

resources in four assessment units within the Paris Basin (table 2). 

For undiscovered technically recoverable resources, the mean totals 

are: 222 million barrels of continuous oil (MMBO), with a fractile 

(F95–F5, respectively) range from 42–527 MMBO; 2,092 billion 

cubic feet of continuous gas (BCFG), with a fractile range from 

3–5,547 BCFG; 18 million barrels of conventional oil, with a fractile range from 10–31 MMBO; and 47 BCFG of conventional gas, 

with a fractile range from 13–114 BCFG.

Of the mean total continuous oil resource of 222 MMBO, 

140 MMBO are estimated to be in the Toarcian-Domerian 

Continuous Oil AU, and 82 MMBO are in the LotharingianSinemurian Continuous Oil AU. Nearly all potential continuous 

gas resources occur in the Permo-Carboniferous Tight Gas AU 

(mean of 2,074 BCFG, with a range from 0 to 5,503 BCFG). The 

ranges of resource estimates reflect the geologic uncertainty of the 

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FRANCE

UNITED KINGDOM

GERMANY BELGIUM

NETHERLANDS

SWITZERLAND

English Channel

BAY OF

BISCAY

NORTH SEA

7°6°5°4°3°2°1°0°1°2°3°4°5° 52°

51°

50°

49°

48°

47°

46°

FRANCE

Area of

study

BAY OF

BISCAY

NORTH

SEA

English Channel

EXPLANATION

Anglo-Paris Basin Province 

International boundary

Paris Basin 

0 62.5 125 MILES

0 62.5 125 KILOMETERS

Figure 1. Location of the Paris 

Basin within the Anglo-Paris 

Basin Province.

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2015–3016

April 2015
source-reservoir rock systems. Much of the uncertainty is interpreted to be related to the quantity of oil remaining in the source 

rocks following migration.

Using mean estimated ultimate recoveries, total potential areas, 

drainage areas, and success ratios (table 2), we estimate a mean 

of about 6,400 hydraulically fractured wells would be needed to 

exploit the continuous oil and gas resources.

Paris Basin Assessment Team

Christopher J. Schenk, Ronald R. Charpentier, Timothy R. Klett, 

Marilyn E. Tennyson, Tracey J. Mercier, Phuong A. Le, Michael 

E. Brownfield, Janet K. Pitman, Stephanie B. Gaswirth, Kristen R. 

Marra, and Heidi M. Leathers.

Table 1. Key assessment input data for the three unconventional (continuous) assessment units in the Paris Basin.

[EUR (estimated ultimate recovery per well), well drainage area, and success ratios are from U.S. shale-gas and shale-oil analogs. The average EUR input is the minimum, median (not the mode), maximum, and calculated mean. AU, assessment unit, %, percent; MMBO, million barrels of oil; BCFG, billion cubic feet of gas]

Assessment input data

Toarcian-Domerian Continuous Oil AU Lotharingian-Sinemurian Continuous Oil AU

Minimum Mode Maximum Calculated 

mean Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 2,690 269,000 1,485,000 585,563 3,370 337,000 691,000 343,790

Average drainage area of wells (acres) 80 160 320 187 80 160 320 187

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

Average EUR (MMBO, oil; BCFG, gas) 0.04 0.08 0.2 0.086 0.04 0.08 0.2 0.086

Permo-Carboniferous Tight Gas AU

Minimum Mode Maximum Calculated 

mean

Potential production area of AU (acres) 0 382,000 1,892,000 758,000

Average drainage area of wells (acres) 40 110 180 110

Success ratios (%) 10 50 90 50

Average EUR (MMBO, oil; BCFG, gas) 0.25 0.6 1.5 0.645

Table 2. Assessment results for unconventional (continous) and conventional oil and gas resources in the Paris Basin.

[MMBO, million barrels of oil. BCFG, billion cubic feet of gas; MMBNGL, million barrels of natural gas liquids; TPS, total petroleum system; AU, assessment unit. Results 

shown are fully risked estimates. For gas accumulations, all liquids are included under the NGL (natural gas liquids) category. F95 represents a 95 percent chance of at least 

the amount tabulated. Other fractiles are defined similarly. Fractiles are additive under assumption of perfect positive correlation. Shading indicates not applicable.]

Total petroleum systems (TPS) 

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

Toarcian-Domerian TPS

Toarcian-Domerian 

Continuous Oil AU 1.0 Oil 24 113 346 140 2 9 29 11 0 0 0 0

Lotharingian-Sinemurian TPS

Lotharingian-Sinemurian 

Continuous Oil AU 1.0 Oil 18 72 181 82 1 6 15 7 0 0 0 0

Permo-Carboniferous Composite TPS

Permo-Carboniferous Tight 

Gas AU 0.9 Gas 0 1,657 5,503 2,074 0 12 43 15

Total unconventional

 resources

42 185 527 222 3 1,672 5,547 2,092 0 12 43 15

Mesozoic Composite TPS

Mesozoic Reservoirs AU 1.0

Oil 10 17 31 18 1 2 3 2 0 0 0 0

 Gas 12 35 111 45 0 0 1 0

Total conventional

 resources

10 17 31 18 13 37 114 47 0 0 1 0

Total undiscovered

 resources

52 202 558 240 16 1,709 5,661 2,139 0 12 44 15

References Cited

Charpentier, R.R., and Cook, T.A., 2011, USGS methodology 

for assessing continuous petroleum resources: U.S. Geological 

Survey Open-File Report 2011–1167, 75 p., http://pubs.usgs.gov/

of/2011/1167/. 

Wuestefeld, Patrick, Hilgers, Christoph, and Koehrer, Bastian, 

2014, Structural diagenesis in an Upper Carboniferous tight gas 

sandstones analog: American Association of Petroleum Geologists, Search and Discovery Article #41491, 21 p.

For Further Information

Assessment results are available at the USGS Energy Resources 

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

ISSN 2327-6916 (print) ISSN 2327-6932 (online) http://dx.doi.org/10.3133/fs20153016