10° 12° 14° 16° 18° 20° 22° 24° 26° 28° 30° 32° 34° 36° 38°

62°

60°

58°

56°

54°

SWEDEN

FINLAND

NORWAY

BELARUS

UKRAINE

RUSSIA

RUSSIA

LATVIA

POLAND

ESTONIA

LITHUANIA

GERMANY

BALTIC SEA

Area of 

study

SWLHLGRS

BO

ATLANTIC

 OCEAN

ARCTIC OCEAN

0 125

0 125 250 KILOMETERS

250 MILES

Source: U.S. National Park Service

EXPLANATION

International boundary

Baltic Depression Province 4021

Silurian Shale Gas AU 40210362

Silurian Continuous Oil AU 40210361

Cambrian-Ordovician Shale Gas 

AU 40210262

Cambrian-Ordovician Continuous Oil 

AU 40210261

Lower Paleozoic Reservoirs AU 40210401

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2015–3015

March 2015

National and Global Petroleum Assessment Project

Assessment of Undiscovered Conventional and Continuous Oil 

and Gas Resources of the Baltic Depression Province, 2014

The U.S. Geological Survey estimated mean volumes of 

undiscovered, technically recoverable resources of 282 million barrels of conventional oil, 576 billion cubic feet of 

conventional gas, 1.3 billion barrels of continuous oil, and 

4.6 trillion cubic feet of shale gas in the Baltic Depression 

Province.

Introduction

As part of the U.S. Geological Survey’s (USGS) National and 

Global Petroleum Assessment Project, the USGS completed an 

assessment of the conventional and continuous (unconventional) 

oil and gas resources of the Baltic Depression Province (fig. 1). 

The Baltic Depression Province is an area of approximately 

232,410 square kilometers (km2) that exists partly offshore and 

includes areas of onshore Poland, Russia (Kaliningrad), Lithuania, 

Latvia, Estonia, and Sweden.

For this study, the Lower Paleozoic Composite Total Petroleum 

System (TPS) was defined to include lower Paleozoic source rocks 

and conventional oil and gas reservoirs. The Lower Paleozoic 

Reservoirs Assessment Unit (AU) was bounded, in part, by the 

Silurian outcrop (Poprawa and others, 1999) and the 500-meter (m) 

isopach of Cambrian rocks (Shogenova and others, 2009). Discovered conventional oil and gas accumulations in the province (IHS 

Energy, 2013) provide evidence for: (1) the existence of a viable 

petroleum system containing lower Paleozoic source rocks, (2) the 

Figure 1. Location of the Baltic 

Depression Province 4021 (dashed 

black line) and conventional and 

continuous oil and gas assessment 

unit boundaries. LH, Lithuania; 

LG, Latvia; RS, Russia; SW, Sweden; 

BO, Belarus.

generation of hydrocarbons, and (3) the migration of hydrocarbons 

into lower Paleozoic conventional reservoirs. At the time of this 

assessment, the Baltic Depression Province contained 45 conventional oil and 6 conventional gas accumulations (IHS Energy, 2013), 

which exceed the minimum assessment size of 1 million barrels of 

oil (MMBO) and 6 billion cubic feet of gas (BCFG) used in this 

assessment.

The USGS assessment methodology for continuous (unconventional) resources requires that potential source rocks in the 

AU must: (1) contain greater than 2 weight percent total organic 

carbon (TOC); (2) contain Type I or Type II organic matter; (3) be 

within the oil and gas thermal generation window; and (4) contain 

organic-rich shale greater than 15 m in thickness (Charpentier and 

Cook, 2011). Using these geologic criteria, the USGS defined two 

continuous TPSs: (1) the Cambrian-Ordovician TPS containing 

the Cambrian-Ordovician Continuous Oil AU and the CambrianOrdovician Shale Gas AU, and (2) the Silurian TPS containing the 

Silurian Continuous Oil AU and the Silurian Shale Gas AU (fig. 1). 

The assessment input data for each continuous AU is shown in 

table 1.

Petroleum generation from Cambrian, Ordovician, and Silurian 

source rocks began in the Late Silurian prior to the Devonian to 

Carboniferous Hercynian orogeny. Uplift and erosion during this 

orogeny removed at least 1,000 m of lower Paleozoic rocks and 

potentially affected the retention of hydrocarbons within the sourcereservoir rock systems (Ulmishek, 1990), which constitutes a major 

source of geologic uncertainty in the assessment.
Table 2. Assessment results for conventional and continuous oil and gas resources in the Baltic Depression Province.

[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 the assumption of perfect positive correlation. Shading indicates not applicable.]

Total petroleum systems (TPS) 

and Assessment Units (AU)

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

Cambrian-Ordovician TPS 402102

Cambrian-Ordovician Continuous Oil

 AU 40210261 0.9 Oil 0 587 2,028 744 0 118 442 156 0 3 14 5

Cambrian-Ordovician Shale Gas

 AU 40210262 0.9 Gas 0 1,162 4,337 1,540 0 9 36 12

Silurian TPS 402103

Silurian Continuous Oil

 AU 40210361 1.0 Oil 104 445 1,462 569 20 89 321 119 1 2 10 3

Silurian Shale Gas

 AU 40210362 1.0 Gas 510 2,235 7,094 2,804 4 17 60 22

Total unconventional resources 104 1,032 3,490 1,313 530 3,604 12,194 4,619 5 31 120 42

Lower Paleozoic Composite TPS 402104

Lower Paleozoic Reservoirs

 AU 40210401 1.0

Oil 131 264 498 282 23 53 112 58 1 1 3 2

 Gas 211 474 977 518 1 3 7 4

Total conventional resources 131 264 498 282 234 527 1,089 576 2 4 10 6

Total undiscovered resources 235 1,296 3,988 1,595 764 4,131 13,283 5,195 7 35 130 48

Table 1. Key assessment input data for the four continuous assessment units in the Baltic Depression Province.

[EUR (estimated ultimate recovery per well), well drainage area, and success ratios are from U.S. shale-gas and shale-oil analogs. MMBO, million barrels of oil; BCFG, 

billion cubic feet of gas; AU, assessment unit; %, percent. The average EUR input is the minimum, median, maximum, and calculated mean.]

Assessment input data

Cambrian-Ordovician Continuous Oil AU Cambrian-Ordovician Shale Gas AU

Minimum Mode Maximum Calculated mean Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 0 4,943,700 19,774,800 8,239,500 0 1,427,120 5,708,460 2,378,527

Average drainage area of wells (acres) 120 160 220 167 120 160 220 167

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

Average EUR (MMBO, oil; BCFG, gas) 0.01 0.03 0.1 0.034 0.1 0.2 1 0.245

Silurian Continuous Oil AU Silurian Shale Gas AU

Minimum Mode Maximum Calculated mean Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 78,500 1,962,570 7,850,270 3,297,113 50,370 1,259,180 5,036,720 2,115,423

Average drainage area of wells (acres) 120 160 220 167 120 160 220 167

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

Average EUR (MMBO, oil; BCFG, gas) 0.02 0.05 0.2 0.058 0.1 0.4 1.3 0.447

Resource Summary

The USGS quantitatively assessed oil and gas resource volumes 

in one conventional AU and four continuous AUs within the Baltic 

Depression Province (table 2). For conventional resources, the 

mean totals for the Lower Paleozoic Reservoirs AU are 282 million 

barrels of oil (MMBO), 576 billion cubic feet of gas (BCFG), and 

6 million barrels of natural gas liquids (MMBNGL). For continuous resources, the mean totals are 1,313 MMBO (continuous oil), 

4,619 BCFG (shale gas), and 42 MMBNGL for the four assessment 

units.

For Further Information

Assessment results are available at the USGS Central Energy 

Resources Science Center website: http://energy.cr.usgs.gov/oilgas/

noga/.

Baltic Depression Assessment Team

Michael E. Brownfield, Christopher J. Schenk, Ronald R. Charpentier, Timothy R. Klett, Janet K. Pitman, Marilyn E. Tennyson, 

Stephanie B. Gaswirth, Tracey J. Mercier, Phuong A. Le, and Heidi 

M. Leathers.

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/.

IHS Energy, 2013, International petroleum 

exploration and production database: Englewood, Colo., IHS Energy. [current through 

December 2013.]

Poprawa, Pawel, Šliaupa, Saulius, Stephenson, 

R., and Lazauskienė, J., 1999, Late VendianEarly Paleozoic tectonic evolution of the 

Baltic Basin—Regional tectonic implications from subsidence analysis: Tectonophysics, v. 314, nos. 1–3, p. 219–239.

Shogenova, Alla, Šliaupa, Saulius, Vaher, Rein, 

Shogenov, Kazbulat, and Pomeranceva, 

Raisa, 2009, The Baltic Basin—Structure, 

properties of reservoir rocks, and capacity for geological storage of CO2

: Estonian 

Journal of Earth Sciences, v. 58, no. 4, 

p. 259–267.

Ulmishek, G.F., 1990, Geologic evolution and 

petroleum resources of the Baltic Basin, 

in Leighton, M.W., Kolata, D.R., Oltz, 

D.F., and Eidel, J.J., eds., Interior Cratonic 

Basins: American Association of Petroleum 

Geologist Memoir, no. 51, p. 603–632.

ISSN 2327-6916 (print)

ISSN 2327-6932 (online)

http://dx.doi.org/10.3133/fs20153015