National and Global Petroleum Assessment

Assessment of Undiscovered Oil and Gas Resources in the 

Midlands Area, England, 2018

Figure 1. Location of four assessment units (AUs) in the Midlands area of 

England.

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

4° W 3° W 2° W 1° W 0° 1° E

54° N

53° N

NORTH

SEA

IRISH

SEA

UNITED KINGDOM

WALES

ENGLAND

EXPLANATION

Upper Bowland-Hodder Shale Gas AU

Upper Bowland-Hodder Shale Oil AU

Lower Bowland-Hodder Shale Oil AU

Lower Bowland-Hodder Shale Gas AU

0 20 40 MILES

0 20 40 KILOMETERS NORTH

SEA

NORTH

ATLANTIC

Map

area

FRANCE

GREAT

BRITAIN

IRELAND

Introduction

The U.S. Geological Survey (USGS) completed 

an assessment of undiscovered, technically recoverable 

continuous (unconventional) and conventional oil and gas 

resources in the Midlands area of England (figs. 1 and 2). 

The Midlands is a structurally complex area as a result of 

several regional tectonic events (Fraser and Gawthorpe, 

1990; Corfield and others, 1996). Extension in the Late 

Devonian to Carboniferous led to deposition of synrift 

organic-rich shales of the lower part of the Bowland 

Shale Formation and Hodder Mudstone Formation within 

several grabens. Postrift regional thermal subsidence led 

to the deposition of organic-rich shales in the upper part 

of the Bowland Formation and fluvial-deltaic sandstones 

of the Millstone Grit Group. Shales in the upper and lower 

parts of the Bowland and in the Hodder represent the most 

viable petroleum source rocks in the Midlands (Gross 

and others, 2015; Raji and others, 2015; Yang and others, 

2016; Fauchille and others, 2017; Hennissen and others, 

2017; Whitelaw and others, 2017). Regional, northdirected compression in the late Carboniferous and Early 

Permian caused many of the extensional structures to be 

uplifted and inverted. Extension and subsidence in the 

Late Permian through Jurassic resulted in the deposition 

of several kilometers of sediment, which led to thermally 

mature organic matter in shales of the Bowland and 

Hodder Formations and to the generation and migration 

of oil and gas. Up to 4 kilometers of uplift and erosion in 

the Paleogene (Anell and others, 2009) may have resulted 

in the breaching of conventional traps and the loss of 

oil and gas resources from conventional and continuous 

reservoirs. This uplift and possible loss of oil and gas is 

the major source of geologic uncertainty in the assessment 

of conventional and continuous oil and gas resources in 

the Midlands area.

Total Petroleum Systems and Assessment Units

In the Midlands area, the USGS defined the 

Bowland-Hodder Total Petroleum System (TPS), the 

Carboniferous TPS, and the Carboniferous Coal TPS. The 

Bowland-Hodder TPS encompasses oil or gas retained 

within shales of the Bowland and Hodder Formations 

in the (1) Upper Bowland-Hodder Shale Gas Assessment Unit (AU), 

(2) Upper Bowland-Hodder Shale Oil AU, (3) Lower BowlandHodder Shale Gas AU, and (4) Lower Bowland-Hodder Shale Oil AU. 

Boundaries of potential shale-gas areas are modified from Andrews 

(2013). Shales in the lower part of the Bowland are as much as 

3,000 meters (m) thick and contain both Type II and Type III kerogen. 

Shales in the upper part of the Bowland are as much as 900 m thick 

and contain predominantly Type II kerogen. Thermal maturity ranges 

upward to gas-generation levels in both shales (greater than 1.3 percent 

vitrinite reflectance), so present-day values of total organic carbon and 

hydrogen index are variable as these values are affected by maturation. 

The geologic model for potential shale-oil and shale-gas resources in 

the Bowland–Hodder TPS is for some portion of the oil or gas to have 

been retained within shales of the Bowland and Hodder Formations 

following Paleogene uplift and erosion.

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2018–3028

ver. 1.1, August 2018

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

recoverable resources of 319 million barrels of oil and 8.3 trillion cubic feet of gas in the Midlands area of England.
Figure 2. Location of three assessment units (AUs) in the Midlands area of England.

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

4° W 3° W 2° W 1° W 0° 1° E

54° N

53° N

NORTH

SEA

IRISH

SEA

UNITED KINGDOM

WALES

ENGLAND

EXPLANATION

Namurian–Westphalian Tight Gas AU

Midlands Coalbed Gas AU

Midlands Conventional Oil and Gas AU

0 20 40 MILES

0 20 40 KILOMETERS

NORTH

SEA

NORTH

ATLANTIC

Map

area

FRANCE

GREAT

BRITAIN

IRELAND

Table 1. Key input data for seven assessment units in the Midlands area of England.

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

ratio, and EUR are defined partly using U.S. shale-gas and shale-oil analogs. The average EUR input is the minimum, median, maximum, and calculated mean. Shading 

indicates not applicable]

Assessment input data—Continuous AUs

Upper Bowland-Hodder Shale Gas AU Upper Bowland-Hodder Shale Oil AU

Minimum

Mode Maximum Calculated 

mean

Minimum

Mode Maximum Calculated 

mean

Potential production area of AU (acres) 560 1,125,500 2,251,000 1,125,687 560 1,007,000 2,000,000 1,002,520

Average drainage area of wells (acres) 100 140 180 140 80 140 200 140

Success ratio (%) 10 50 90 50 10 50 90 50

Average EUR (BCFG, gas; MMBO, oil) 0.1 0.4 1.3 0.447 0.04 0.08 0.2 0.086

AU probability 1.0 0.9

Assessment input data—Continuous AUs

Lower Bowland-Hodder Shale Gas AU Lower Bowland-Hodder Shale Oil AU

Minimum

Mode Maximum Calculated 

mean

Minimum

Mode Maximum Calculated 

mean

Potential production area of AU (acres) 600 1,470,500 2,941,000 1,470,700 500 101,000 300,000 133,833

Average drainage area of wells (acres) 60 120 180 120 60 80 140 93.3

Success ratio (%) 10 50 90 50 10 50 90 50

Average EUR (BCFG, gas; MMBO, oil) 0.1 0.4 1.3 0.447 0.01 0.04 0.15 0.046

AU probability 0.9 0.9

Assessment input data—Continuous AUs

Namurian–Westphalian Tight Gas AU Midlands Coalbed Gas AU

Minimum

Mode Maximum Calculated 

mean

Minimum

Mode Maximum Calculated 

mean

Potential production area of AU (acres) 480 800,000 1,206,000 668,827 400 950,000 1,908,000 952,800

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

Success ratio (%) 10 50 90 50 10 50 90 50

Average EUR (BCFG) 0.08 0.4 1.2 0.44 0.08 0.25 1.0 0.29

AU probability 1.0 1.0

Assessment input data—Conventional AU

Midlands Conventional Oil and Gas AU

Minimum

Median Maximum Calculated 

mean

Number of oil fields 1 5 15 5.3

Number of gas fields 1 20 60 21.3

Size of oil fields (MMBO) 0.5 1.5 20 2.1

Size of gas fields (BCFG) 3 9 80 11.3

AU probability 1.0
The Carboniferous TPS is defined by oil and gas sourced 

from shales of the Bowland and Hodder Formations and possibly from coals of Westphalian age. Within this TPS are the 

Namurian–Westphalian Tight Gas AU and Midlands Conventional Oil and Gas AU. The geologic model for conventional 

accumulations in this AU is for oil and gas to have migrated 

into inversion structures that contain possible clastic and 

carbonate reservoirs. The geologic model for the continuous 

Namurian–Westphalian Tight Gas AU is for gas, generated 

from organic matter in shales of the Bowland and Hodder 

Formations and possibly from the Westphalian coals, to have 

migrated locally into and to have been trapped within low 

permeability, nonmarine to shallow-marine sandstones and siltstones of Namurian and Westphalian age. The AU area encompasses the Carboniferous Cleveland and Cheshire subbasins.

The Carboniferous Coal TPS is defined to encompass 

potential coalbed gas resources within Westphalian coals in 

two main areas of the Midlands, as mapped by the Department 

of Energy and Climate Change, United Kingdom (2013). In 

unmined areas, net coal thickness is as much as 40 m, and coal 

rank is variable but ranges upward to anthracite. The Midlands 

Coalbed Gas AU does not include areas of current coal mines, 

mined areas, or areas that produce coal-mine gas.

Assessment input data for seven assessment units are shown 

in table 1. For continuous assessment units, well drainage areas, 

success ratios, and estimated ultimate recoveries are guided by 

geologic analogs from the United States.

Undiscovered Resources Summary

The USGS quantitatively assessed undiscovered continuous 

and conventional oil and gas resources within the Midlands 

area of England (table 2). For undiscovered resources, the 

estimated mean totals are 319 million barrels of oil (MMBO), 

with an F95–F5 range from 4 to 753 MMBO; 8,254 billion 

cubic feet of gas (BCFG), or 8.3 trillion cubic feet of gas, with 

an F95–F5 range from 1,235 to 19,696 BCFG; and 54 million 

barrels of natural gas liquids (MMBNGL) with an F95–F5 range 

from 6 to 133 MMBNGL. Of the total mean oil resources of 

319 MMBO, about 97 percent, or 308 MMBO, is potential shaleoil resources; and of the mean total gas resources of 8,254 BCFG, 

about 97 percent, or 8,006 BCFG, are shale gas (54 percent), tight 

gas (22 percent), and coalbed gas (21 percent) resources.

Table 2. Results for seven assessment units in the Midlands area of England.

[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

Bowland-Hodder Total Petroleum System

Upper Bowland-Hodder 

Shale Gas AU 1.0 Gas 368 1,486 4,209 1,779 3 12 35 14

Upper Bowland-Hodder 

Shale Oil AU 0.9 Oil 0 250 653 279 0 148 400 167 0 0 1 1

Lower Bowland-Hodder 

Shale Gas AU 0.9 Gas 0 2,076 6,252 2,465 0 25 76 30

Lower Bowland-Hodder 

Shale Oil AU 0.9 Oil 0 23 78 29 0 14 48 17 0 0 0 0

Carboniferous Total Petroleum System

Namurian–Westphalian 

Tight Gas AU 1.0 Gas 403 1,590 4,179 1,850 2 6 17 7

Carboniferous Coal Total Petroleum System

Midlands Coalbed Gas AU 1.0 Gas 343 1,411 4,179 1,728 0 0 0 0

Total undiscovered 

continuous resources 0 273 731 308 1,114 6,725 19,267 8,006 5 43 129 52

Carboniferous Total Petroleum System

Midlands Conventional Oil 

and Gas AU 1.0 Oil 4 10 22 11 3 6 13 7 0 0 0 0

Gas 118 226 416 241 1 2 4 2

Total undiscovered 

conventional resources 4 10 22 11 121 232 429 248 1 2 4 2

Total undiscovered 

resources

4 283 753 319 1,235 6,957 19,696 8,254 6 45 133 54
Image within the Midlands area. Photograph by Tony Hill, accessed June 22, 2018, at https://pixabay.com/en/malham-cove-yorkshire-pano-panorama-2451405/.

References Cited

Andrews, I.J., 2013, The Carboniferous Bowland Shale 

gas study—Geology and resource estimation: London, 

United Kingdom, Department of Energy and Climate 

Change, prepared by British Geological Survey [London, 

United Kingdom], 64 p., accessed February 26, 2018, at 

https://www.ogauthority.co.uk/media/2782/bgs_decc_

bowlandshalegasreport_main_report.pdf.

Anell, I., Thybo, H., and Artemieva, I.M., 2009, Cenozoic uplift 

and subsidence in the North Atlantic region—Geological 

evidence revisited: Tectonophysics, v. 474, nos. 1–2, p. 78–105.

Corfield, S.M., Gawthorpe, R.L., Gage, M., Fraser, A.J., and 

Besly, B.M., 1996, Inversion tectonics of the Variscan foreland of the British Isles: Journal of the Geological Society 

[London, United Kingdom], v. 153, p. 17–32.

Department of Energy and Climate Change, United Kingdom, 

2013, The unconventional hydrocarbon resources of Britain’s 

onshore basins—Coalbed methane (CBM): London, United 

Kingdom, Department of Energy and Climate Change, 

prepared by British Geological Society [London, United 

Kingdom], 40 p., accessed February 26, 2018, at https://www.

ogauthority.co.uk/media/1694/promote_uk_cbm_2012.pdf.

Fauchille, A.L., Ma, L., Rutter, E., Chandler, M., Lee, P.D., and 

Taylor, K.G., 2017, An enhanced understanding of the basinal 

Bowland shale in Lancaster (UK), through microtextural and 

mineralogical observations: Marine and Petroleum Geology, 

v. 86, p. 1374–1390.

Fraser, A.J., and Gawthorpe, R.L., 1990, Tectono-stratigraphic 

development and hydrocarbon habitat of the Carboniferous 

in northern England: Geological Society, London, Special 

Publications, v. 55, p. 49–86.

Gross, D., Sachsenhofer, R.F., Bechtel, A., Pytlak, L., 

Rupprecht, B., and Wegerer, E., 2015, Organic geochemistry 

of Mississippian shales (Bowland Shale Formation) in central 

Britain—Implications for depositional environment, source 

rock and gas shale potential: Marine and Petroleum Geology, 

v. 59, p. 1–21.

Hennissen, J.A.I., Hough, E., Vane, C.H., Leng, M.J., Kemp, 

S.J., and Stephenson, M.H., 2017, The prospectivity of a 

potential shale gas play—An example from the southern 

Pennine Basin (central England, UK): Marine and Petroleum 

Geology, v. 86, p. 1047–1066.

Raji, M., Cornford, C., Pather, A., and Satterfield, D., 2015, 

Unconventional oil and gas potential of the Widmerpool 

Gulf in the East Midlands Province of England: Unconventional Resources Technology Conference, Denver, Colo., 

August 12–14, 2013, Proceedings, p. 949–961, accessed 

February 26, 2018, at https://library.seg.org/doi/abs/10.1190/

urtec2013-097.

Whitelaw, P., Uguna, C., Stevens, L., Meredith, W., Snape, 

C.E., Vane, C., Moss-Hayes, V., and Carr, A.D., 2017, 

An evaluation of shale gas potential in the Bowland 

Shale, UK using sequential high water pressure pyrolysis and methane adsorption: American Association of 

Petroleum Geologists, Search and Discovery Article 

No. 51450, December 26, 2017, 17 p., accessed February 

26, 2018, at http://www.searchanddiscovery.com/pdfz/

documents/2017/51450whitelaw/ndx_whitelaw.pdf.html.

Yang, S., Horsfield, B., Mahlstedt, N., Stephenson, M., and 

Könitzer, S., 2016, On the primary and secondary petroleum 

generating characteristics of the Bowland Shale, northern 

England: Journal of the Geological Society [London, United 

Kingdom], v. 173, no. 2, p. 292–305.

Midlands Area Assessment Team

Christopher J. Schenk, Marilyn E. Tennyson, Tracey J. Mercier, Cheryl A. Woodall, Thomas M. Finn, Stephanie B. Gaswirth, 

Phuong A. Le, Michael E. Brownfield, Kristen R. Marra, 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/fs20183028