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Grant agreement No. 640979
ShaleXenvironmenT
Maximizing the EU shale gas potential by minimizing its environmental footprint
H2020-LCE-2014-1
Competitive low-carbon energy
D2.3 Reservoir conditions for European samples
WP 2 – Shale Core Acquisition and HTHP Handling Capabilities
Due date of deliverable 31/08/2018 (Month 36) Actual submission date 31/08/2018 (Month 36) Start date of project 1st September 2015 Duration 36 months Lead beneficiary Halliburton Last editor Jabraan Ahmed (UCL) Contributors UCL, Halliburton Dissemination level Public (PU)
This Project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 640979.
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History of the changes
Version Date Released by Comments
1.0 12-05-17 Nils Backeberg Early draft of general outline
1.1 30-07-18 Jabraan Ahmed First draft circulated internally for review
1.2 10-08-18 Jabraan Ahmed Final Version
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Table of contents Key word list ............................................................................................................................. 4
Definitions and acronyms ........................................................................................................ 4
1. Introduction ................................................................................................................. 5
1.1 General context ................................................................................................. 5
1.2 Deliverable objectives ........................................................................................ 6
2. Distribution of European Shale Gas Plays .................................................................... 7
3. Summary of activities and research findings ............................................................. 10
3.1 Basin summaries .............................................................................................. 11
3.1.1 The Bowland Basin, England ..................................................................... 11
3.1.2 The Midland Valley Basin, Scotland .......................................................... 11
3.1.3 Alum Shale Basin, Scandinavia ................................................................. 11
3.1.4 The Lower Saxony Basin, Germany .......................................................... 12
3.1.5 The Paris Basin, France (and Weald Basin, south England) ...................... 12
3.1.6 The Southeast Basin, France..................................................................... 12
3.1.7 The Basque-Cantabrian Basin, Spain ........................................................ 12
3.1.8 The Baltic Basin, Poland ............................................................................ 13
3.1.9 The Lublin & Podlasie Basin, Poland ......................................................... 13
4. Conclusions and future steps ..................................................................................... 14
5. Publications resulting from the work described ........................................................ 14
6. Bibliographical references.......................................................................................... 15
List of figures
Figure 1: (Top) Map of Europe showing shale rock sedimentary basins (yellow) with shale gas potential areas highlighted in colour. Colour represents the age of the shale gas play (blue – Jurassic, red – Carboniferous, green – Cambrian to Silurian). (Bottom) Geological timeline and tectonic evolution of Pangaea with depositional environment and basin settings shown for European shale gas plays. ......................................................................... 8
List of tables Table 1: Summary of European shale gas plays with present day temperature and pressure estimates and measurements for selected depths within play range. Red indicates assumed/calculated values. ....................................................................................................... 9
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Key word list Shale rock library, European shale gas basins, Pressure – Temperature conditions, Total organic carbon range, Maturity range, Exploration target areas
Definitions and acronyms
SXT ShaleXenvironmenT European Consortium
WP Work Package
UCL University College London
HB Halliburton
PTx Pressure – temperature – composition
TOC Total organic carbon, measured in volume percent (%)
Ro Vitrinite reflectance (%); measure of thermal maturity
Tcf Trillion cubic feet (for gas reservoir estimates)
MPa Mega pascal (pressure)
nD NanoDarcy
MA Million years ago
EIA U.S. Energy Information Administration
BGS British Geological Survey
USGS United States Geological Survey
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1. Introduction
WP2 has the main task of providing shale core samples for experimental characterization.
The specific objectives as part of WP2 include:
1. Provide shale rock samples (some at reservoir pressure) for scientific research;
2. Develop capability for laboratory exchange and analysis of pressurised samples
recovered from depth;
3. Provide pressure temperature composition (PTx) properties of shale rocks under
reservoir conditions to be used in physical, chemical, thermodynamic models and
mechanical experiments in other work packages.
1.1 General context
Unconventional gas (and oil) refers to hydrocarbon reservoirs stored within tight shales.
These shales are termed tight due to their extremely low permeability, which traps the
gas/oil within its source rock. Unconventional tight shale gas contrasts with conventional oil
& gas reservoirs, which have migrated away from their source rock and accumulated in
structural traps. Deliverable 2.3 of the ShaleXenvironmenT (SXT) European research
consortium reports on the reservoir conditions of unconventional European shale gas
basins. We report pressure and temperature data for prospective areas of shale gas basins
in Europe based on published thermal maturity (Ro) and total organic carbon (TOC) ranges
that are conducive for unconventional shale gas & shale oil. Economic potential is based on
a recommended list of criteria (Charpentier and Cook, 2011), with:
1. A total organic carbon content (TOC) of greater than 2 weight percent. Very high TOC
contents (> 15%) are also not conducive to effective exploitation potential, as these
rocks are typically mechanically ductile and difficult to pervasively fracture.
2. The required thermal maturity window for gas generation (Ro range of 0.7 – 2.5 %, >
1.2 % is ideal for gas).
3. A stratigraphic thickness of greater than 15m (others report > 30m) that meets
criteria 1 and 2.
The exploration industry includes further criteria that promote the exploitation potential,
which are a porosity range of 4 – 15 volume %, a permeability of greater than 100
nanoDarcy (nD), and low clay contents (< 40 %) or high quartz-carbonate contents, the latter
affecting the ‘frackability’ of the shale as in criteria 1 above. In contrast to oil generation,
the kerogen types seem to play a less important role in gas productivity (e.g. Tissot et al.,
1974).
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The data in this report are sourced from publically available reports and publications (see
list of references), world shale resource assessment by the U.S. Energy Information
Administration (EIA), United States Geological Survey (USGS), published down-hole
measurements and in-house research by Halliburton (HB).
1.2 Deliverable objectives
The report provides PTx conditions of European samples beyond the direct access of the SXT
research program. The current rock library of European shale rocks held by the SXT
consortium, covers the Bowland Shale in the UK, one of the primary shale gas exploration
targets in Europe. PTx data for the Bowland Shale is published in the previous report (D2.2 –
August 2016) and is included here for completion. This report expands on the PTx data of
report D2.2 to include the major shale gas basins across Europe. Of note, the Weald basin of
the UK is excluded as research and exploration are showing that it is predominantly a shale
oil reservoir (insufficient maturity for gas generation).
The PTx conditions form the basis parameters input into experiments, technical analyses
and models covered by the SXT research consortium.
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2. Distribution of European Shale Gas Plays
Various shale gas basins are located across Europe and we have identified the main shale
gas plays under exploration, or with exploration potential (Figure 1). In contrast to the North
American shale gas plays, European sedimentary basins have experienced a more
tectonically active geological history. This manifests as a series of superimposed geological
features, which need to be deconvoluted when making assessments on important shale play
criteria (i.e. maturity, fracture network, mechanical properties etc.).
All of the basins are linked to the tectonic evolution of Pangaea, the supercontinent
landmass that combined Gondwana (Africa, South America, Australia, India, Antarctica) and
Euramerica (or Laurussia: Europe, Asia and North America). The oldest shale gas basins
stretch from the Cambrian to Silurian periods and developed on continental platforms
before the amalgamation of Pangaea (green in Figure 1) at ~500 million years ago (Ma). The
next suite of sedimentary basins forming current day shale gas plays occurred as intra-
continental basins during the Variscan Orogeny spanning the Carboniferous around 300 Ma
(red in Figure 1). The Variscan Orogeny is the name given to the continental collision of
Gondwana and Euramerica that formed Pangaea. The youngest shale gas plays are found in
Jurassic basins that formed during the break-up of Pangaea (blue in Figure 1), whereby the
supercontinent broke up into the various continental land masses we see today.
For each of the shale gas plays shown in Figure 1 we have identified and summarised the
range of depth and petrophysical conditions (Table 1). The temperature conditions we
report for these areas are estimates for their depth range, using a continental geothermal
gradient of approximately 23°C/km with a surface temperature of 16°C. Similarly, for
reservoir pressure we use a hydrostatic gradient of 0.433 psi/foot (value taken from EIA),
which converts to approximately 9.8 MPa/km. In addition, Halliburton (HB) has provided in-
house research and down-hole pressure – temperature measurements.
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Figure 1: (Top) Map of Europe showing shale rock sedimentary basins (yellow) with shale gas potential areas highlighted in colour. Colour represents the age of the shale gas play (blue – Jurassic, red – Carboniferous, green – Cambrian to Silurian). (Bottom) Geological timeline and tectonic evolution of Pangaea with depositional environment and basin settings shown for European shale gas plays.
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Table 1: Summary of European shale gas plays with present day temperature and pressure estimates and measurements for selected depths within play range. Red indicates assumed/calculated values.
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3. Summary of activities and research findings
This report is a desktop research study covering European shale gas basins. The findings are
meant as a guide to outline potential shale gas regions and provide pressure and
temperature estimates and measurements for depths that fall within the range of shale gas
plays. The pressure-temperature conditions reflect present day conditions and are not
maximum burial and maturity conditions experienced by the shale gas plays.
The prospective areas shown in Figure 1 correlate with the thermal maturity range of the
gas window (Ro = 0.9 to 3.0 %) that each basin experienced and preserved through its
geological history, as well as an economic cut-off of greater than 2% average TOC for shale
plays with a thickness greater than 30 m (approximately > 100 feet). The TOC and thermal
maturity data from published reports reflect borehole samples analysed from shale gas
prospective regions. These are extrapolated, together with geophysical studies (where
available) to assess the extent of potential shale gas plays (coloured areas in Figure 1).
Pressure and temperature data in the Halliburton rows (Table 1) are downhole
measurements from samples with gas potential and are a reference of comparison to
standard condition estimates.
It is important to note that the complete range and heterogeneity of each individual basin is
not represented in this report. Instead, we have researched the broad available literature
where possible in order to summarise representative values and ranges for each region. We
emphasise that the findings of this report are to be used as a starting point and guide for
further research of the individual basins of interest.
The results and findings of European shale rock basins are summarised in Table 1. The table
includes a brief summary of the basin location and prospective region, which are shown on
the map in Figure 1. The literature review rows in Table 1 include research articles and
survey reports. We present data for the Bowland Shale, Midland Valley Basin, Alum Shale,
Lower Saxony Basin, Paris Basin (upper and lower), Southeast Basin, Basque-Cantabrian
Basin, Baltic Basin and the Lublin Basin.
Table 1 excludes details on compositional variable (x). This is due to the broad mineralogical
heterogeneity of shale rocks defined by their sedimentary history. However, the
implications of mineralogy to shale gas prospectively should not be discounted when
considering shale gas exploitation, as the mineralogy defines the “brittleness” or strength of
shales. Shale rocks are typically characterised by their clay content, contrasted against
quartz, feldspar, pyrite and carbonate contents. High clay content shales have a lower
brittleness due to the more ductile behaviour of clays compared to the other shale-rock-
forming minerals. The published shale gas reviews by EIA characterise the basins by clay
contents of “low, medium or high”. As a rule of thumb, ranges of clay volume percentages
can be considered as 5 – 10% (low), 10 – 30% (medium) and 30 - 60% (high), however other
petro-physical factors will also affect the overall brittleness of shale rocks. For the Bowland
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Shale, EIA reports a “medium” clay content and reports by the British Geological Survey
(BGS) indicate high (50 – 60%) clay contents. Samples collected from the BGS as part of the
SXT research program from drill core of the Bowland Shale, have been characterised
predominantly by low clay contents of 6 – 10%. These results show the broad range of
mineral compositions that exist in natural sedimentary basins over cm to m scales, which
need to be considered for each basin separately.
3.1 Basin summaries
3.1.1 The Bowland Basin, England
Shale gas plays in Central England are found in the Carboniferous Craven Group within the
Bowland Shale and the underlying Hodder Formation, developed in sedimentary basins
between carbonate platforms (Fraser and Gawthorpe, 1990). There is a broad range in
depth and thicknesses reported in different reports: for example, the average depth in the
EIA database falls within a range of 5000 – 13000 feet, much deeper than the average depth
used in the pressure and temperature calculation in the “estimates” rows (Table 1). This is
because the EIA includes the Hodder mudstone formation. The Hodder mudstone is also
prospective for shale gas, but due to less drilling penetrating this deeper unit, most
exploration and resource estimations have focussed on the better constrained Bowland
Shale, also referred to as the “upper Bowland-Hodder unit” by Andrews (2013). The basin
has been differentially exhumed since passing through the oil and gas maturation window
during burial, which leads to the broad range in depth to shale gas plays. The highest shale
gas potential of the Bowland basin is within its western parts, where exploration companies
have identified “sweet spots”. The basin is cut by mostly normal faults.
3.1.2 The Midland Valley Basin, Scotland
The Midland Valley Basin in Scotland is a time and tectonic equivalent basin to the Bowland
Shale, but has experienced longer post-burial exhumation, which resulted in the significantly
shallower occurrences of shale gas mature plays (see Table 1). The basin is bounded by large
regional scale faults that outline the NE-SW trend of the basin. The maturity of the basin is
locally enhanced by extensive igneous activity during the Late Carboniferous to Early
Permian.
3.1.3 Alum Shale Basin, Scandinavia
The Alum Shale was deposited during the Middle Cambrian to Early Ordovician Period
(approximately 510 – 480 Ma). The sediments are predominantly shallow marine deposits
developed on the stable Balto-Scandia platform, the fringes of the Baltica microcontinent.
The Baltica microcontinent collided with Laurentia and Avalonia during the Ordovician to
form the Euramerica continental landmass (Figure 1). Shale gas mature areas of the Alum
Shale stretch across northern Denmark and southern Sweden.
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3.1.4 The Lower Saxony Basin, Germany
The Lower Saxony Basin evolution falls within the geological framework of the entire Central
European Basin System that spans from the Carboniferous to the Cretaceous Periods (Bruns
et al., 2013). The main shale gas plays of economic interest in the Lower Saxony Basin
belong to the Lower Jurassic, Toarcian Posedonia Shale (183 – 174 Ma). The Posedonia Shale
extends across both Germany and the Netherlands, but the shale gas mature areas are
predominantly preserved in NE Germany (Figure 1). Therefore, we exclude the Netherlands
from this report. The geometry of the Saxony Basin geology has been deformed into
regional scale folds during the Alpine orogeny, during which the basin was exhumed.
3.1.5 The Paris Basin, France (and Weald Basin, south England)
The Paris Basin is one of the larger sedimentary basins in central Europe. The basin has a
long history that includes two prospective horizons (Table 1): the Permo-Carboniferous
shales (Lower) and the Jurassic shales (Upper). The Jurassic shale is the equivalent to the
Lias Shale found in the UK’s Weald basin in southern England, which is only oil-mature and
not prospective for shale gas (see EIA reports and Andrews, 2014). In the Paris Basin, the
temperature measured in downhole drill sites (Halliburton) is approximately 30°C higher
than the estimate based on the geothermal gradient of 23°C/km. This is due to a geothermal
system in the region elevating the gradient to 35°C/km (Marty et al., 1988).
3.1.6 The Southeast Basin, France
The Southeast Basin in France stretches south from Grenoble across to Montpellier and Nice
in the South (Figure 1). The sedimentary sequence is over 10 km thick covering a history
throughout the Mesozoic and Cenozoic Eras, developed on the flanks of the Alpine thrust
belt. Higher shale gas potential is estimated in Jurassic Lias Shale in the western portion of
the basin with the required gas window and economic organic-rich intervals of around 50 to
200 ft thick (Table 1). Research identifies three potential oil-gas source intervals, but the
tectonic evolution during the Tertiary will have significant effects on the distribution and
potential for unconventional gas retention (Mascle & Vially, 1999).
3.1.7 The Basque-Cantabrian Basin, Spain
Situated in the north of Spain, the Basque-Cantabrian basin contains the country’s most
promising shale gas resources. A sequence of Jurassic Lias shale is of particular interest
given that it has been proven in boreholes across the basin and is consistently of wet-gas
maturity. However, with only a net thickness ~50 ft of organic rich shale at ~3% TOC, the
feasibility of extraction is likely to be hampered by economics. The basin is also host to
marine shales of Silurian-Ordovician age which are likely to be dry-gas mature and thus of
greater prospectivity (Quesada et al., 1997). Strata of this age have not been proven in the
majority of boreholes drilled to date. As a consequence, resource potential specific data is
largely unknown (EIA - Spain, 2015).
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3.1.8 The Baltic Basin, Poland
The Baltic Basin in north Poland was once considered Europe’s premier shale gas resource
thereby attracting international interest and investment earlier in the decade. On account of
the basin’s simple structural evolution, overmature sediments and early studies estimating a
net thickness of at least 800 ft of TOC rich shales, the likes of ConocoPhilips, Marathon Oil,
Nexen, Talisman, BNK and PGNiG have bought acreage and drilled test several wells (EIA –
Poland 2015).
Despite the passage of several years, full scale production has yet to be realised with
operators reporting poor gas yields following stimulation. It is thought that despite the
targeted intervals having properties conducive to gas generation and storage, the strata is
highly heterogenous and not always productive across its lateral extent (Kiersnowski and
Dyrka, 2013). Additionally, developments have been hampered by the operational
challenges such as the inability to stimulate highly pressurised zones.
Exploration is still ongoing in the region, albeit at a subdued pace. The strata of interest date
back to the Cambrian-Silurian where the basin was in a marine setting (Gautier et al., 2012).
The most prospective of these shales were deposited during the Ordovician when the basin
was particularly sediment starved and at its deepest.
3.1.9 The Lublin & Podlasie Basin, Poland
The Lublin and Poldaise Basins have also attracted international investment for shale gas
exploration in Poland, but to lesser extent in comparison to the Baltic Basin. This is on
account of its more complex structural history whereby Cambrian-Silurian shales have been
extensively faulted and folded making correlation attempts more difficult (EIA – Poland,
2015).
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4. Conclusions and future steps
European shale gas plays cover a broad range in geological environments and have ages
spanning across the Palaeozoic. From deep marine basins in the Ordovician, to
continental/intracontinental basins in the Carboniferous and to Jurassic rift basins
associated with the break-up of Pangaea. All of these basins are then further affected by
Alpine tectonics, complicating the structural history. Within this geological setting, Europe
has preserved potentially large recoverable shale gas plays with a varied geological history
leading to a broad range in pressure, temperature and compositional characteristics, which
are simplified and summarised in Table 1.
Generally speaking, older shales, such as those found in Poland, are the most mature and
thus have potentially generated the most amount of shale gas. Moreover, the present day
over pressured reservoir conditions of these formations makes them ideal candidates for
exploration. Carboniferous shales, such as the Bowland Shale UK, also present a viable
exploration target due to the thick net-pay of this reservoir.
5. Publications resulting from the work described
This data compilation will feed into all sample and basin specific publications part of SXT. Parameters for high-pressure high-temperature experiments and modelling simulations have been informed from this work.
Backeberg, N.R., Iacoviello, F., Rittner, M., Mitchell, T.M., Jones, A.P., Day, R., Wheeler, J., Shearing, P.R., Vermeesch, P. and Striolo, A., 2017. Quantifying the anisotropy and tortuosity of permeable pathways in clay-rich mudstones using models based on X-ray tomography. Scientific Reports, 7(1), p.14838.
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6. Bibliographical references
1 Andrews, I.J. 2013. The Carboniferous Bowland Shale gas study: geology and resource estimation. British Geological Survey for Department of Energy and Climate Change, London, UK.
2 Andrews, I.J. 2014. The Jurassic shales of the Weald Basin: geology and shale oil and shale gas resource estimation. British Geological Survey for Department of Energy and Climate Change, London, UK.
3 Bharati et al. 1995. Elucidation of the Alum Shale kerogen structure using a multi-disciplinary approach. Organic Geochemistry, 23 (11/12), 1043 – 1058.
4 Bruns, B. et al. 2013. Petrolium systems evolution in the inverted Lower Saxony Basin, northwest Germany: A 3D basin modelling study. Geofluids, 13, 246 – 271.
5 Bruns, B. et al. 2016. Thermal evolution and shale gas potential estimation of the Wealdon and Posedonia Shale in NW-Germany and the Netherlands: A 3D basin modelling study. Basin Research, 28, 2 – 33.
6 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.
7 Department of Energy and Climate Change, 2012. The unconventional hydrocarbon sources of Britain’s onshore basins – shale gas.
8 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, 55, 49 – 86.
9 Gautier, D.L., Pitman, J.K., Charpentier, R.R., Cook, T., Klett, T.R., and Schenk, C.J., 2012, Potential for technically recoverable unconventional gas and oil resources in the Polish-Ukrainian Foredeep, Poland, 2012: U.S. Geological Survey Fact Sheet 2012–3102, 2 p. (Available at https://pubs.usgs.gov/fs/2012/3102/.)
10 Ghanizadeh, A. et al., 2014. Experimental study of fluid transport processes in the matrix system of the European organic-rich shales: I. Scandinavian Alum Shale. Marine and Petroleum Geology, 51, 79 – 99.
11 Ghanizadeh, A. et al., 2014. Experimental study of fluid transport processes in the matrix system of the European organic-rich shales: II. Posedonia Shale (Lower Toarcian, northern Germany). International Journal of Coal Geology, 123, 20 – 33.
12 Kiersnowski, H. and Dyrka, I., 2013. Ordovician-Silurian shale gas resources potential in Poland: evaluation of Gas Resources Assessment Reports published to date and expected improvements for 2014 forthcoming Assessment. Przegląd Geologiczny. 2013;61(11/1):639-56.
13 Nielson, A. T., et al. 2011. The Lower Cambrian of Scandinavia: Depositional environment, sequence stratigraphy and palaeogeography. Earth-Science Reviews, 107, 207 – 310.
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14 Mascle, A. & Vially, R, 1999. The petroleum systems of the Southeast Basin and Gulf of Lion (France). In: Durnand, B., Jolivet, L., Horvath, F. & Séranne, M. (eds). The Mediterranean Basins: Tertiary Extension within the Alpine Orogen. Geological Society, London, Special Publications, 156, 121 – 140.
15 Marty, B., et al., 1988. Low enthalpy geothermal fluids from the Paris sedimentary basin – 1. Characteristics and origin of gases. Geothermix, 17 (4), 619 – 633.
16 Monaghan, A. A. 2014. The Carboniferous shales of the Midland Valley of Scotland: geology and resource estimation. British Geological Survey for Department of Energy and Climate Change, London, UK.
17 Muñoz, Y. A. et al. 2007. Fluid systems and basin evolution of the western Lower Saxony Basin, Germany. Geofluids, 7, 335 – 355.
18 Pawlewicz, M.J. et al. 2000. Map showing geology, oil and gas fields, and geologic provinces of Europe including Turkey. U. S. Geological Survey, open file report 97-470I
19 Quesada, S. et al. 1997. Geochemical correlation of oil from the Ayoluengo field to Liasic black shale units in the southwestern Basque-Cantabrian Basin (northern Spain). Organic Geochemistry, 27 (1/2), 25 – 40.
20 Stampfli, G. M., et al. 2013. The formation of Pangea. Tectonophysics, 593, 1 – 19.
21 Thickpenny, A. 1984. The sedimentology of the Swedish Alum Shales. Geological Society, London, Special Publications, 15, 511– 525.
22 Thickpenny, A. 1987. Palaeo-oceanography and depositional environment of the Scandinavian Alum Shale: Sedimentological and geochemical evidence. Chapter 8 in: Marine Clastic Sedimentology (Eds. Legget J. K. and Zuffa G. G.), 156 – 171.
23 Tissot B., et al. 1974. Influence of nature and diagenesis of organic matter in formation of petroleum. AAPG Bulletin, 58 (3), 499 – 506.
24 Underhill, J.R. et al. 2008. Controls on Structural Styles, Basin Development and Petroleum Prospectivity in the Midland Valley of Scotland. Marine and Petroleum Geology, 25, 1000-1022.
25 U.S. Energy Information Administration (EIA), September 2015. Technically recoverable shale oil and shale gas resources: Other Western Europe. www.eia.gov
26 U.S. Energy Information Administration (EIA), September 2015. Technically recoverable shale oil and shale gas resources: Poland. www.eia.gov
27 U.S. Energy Information Administration (EIA), September 2015. Technically recoverable shale oil and shale gas resources: Spain. www.eia.gov
28 U.S. Energy Information Administration (EIA), September 2015. Technically recoverable shale oil and shale gas resources: United Kingdom. www.eia.gov
29 Waters, C.N. et al., 2007. Lithostratigraphical framework for Carboniferous successions of Great Britain (Onshore). British Geological Survey Research Report, RR/07/01/ 60pp.
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