Grant agreement No ShaleXenvironmenT. Maximizing the EU shale gas potential by minimizing its environmental footprint

Transcription

1 Grant agreement No ShaleXenvironmenT Maximizing the EU shale gas potential by minimizing its environmental footprint H2020-LCE 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 1 st September 2015 Duration Lead beneficiary Last editor Contributors Dissemination level 36 months Halliburton Jabraan Ahmed (UCL) UCL, Halliburton Public (PU) This Project has received funding from the European Union s Horizon 2020 research and innovation programme under grant agreement no

2 History of the changes Version Date Released by Comments Nils Backeberg Early draft of general outline Jabraan Ahmed First draft circulated internally for review Jabraan Ahmed Final Version PU Page 2 of 16 Version 1.2

3 Table of contents Key word list... 4 Definitions and acronyms Introduction General context Deliverable objectives Distribution of European Shale Gas Plays Summary of activities and research findings Basin summaries The Bowland Basin, England The Midland Valley Basin, Scotland Alum Shale Basin, Scandinavia The Lower Saxony Basin, Germany The Paris Basin, France (and Weald Basin, south England) The Southeast Basin, France The Basque-Cantabrian Basin, Spain The Baltic Basin, Poland The Lublin & Podlasie Basin, Poland Conclusions and future steps Publications resulting from the work described Bibliographical references 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 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 PU Page 3 of 16 Version 1.2

4 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 WP UCL HB PTx ShaleXenvironmenT European Consortium Work Package University College London Halliburton Pressure temperature composition TOC Total organic carbon, measured in volume percent (%) Ro Tcf MPa nd MA EIA BGS USGS Vitrinite reflectance (%); measure of thermal maturity Trillion cubic feet (for gas reservoir estimates) Mega pascal (pressure) NanoDarcy Million years ago U.S. Energy Information Administration British Geological Survey United States Geological Survey PU Page 4 of 16 Version 1.2

5 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 %, > 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). PU Page 5 of 16 Version 1.2

6 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. PU Page 6 of 16 Version 1.2

7 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 intracontinental 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 psi/foot (value taken from EIA), which converts to approximately 9.8 MPa/km. In addition, Halliburton (HB) has provided inhouse research and down-hole pressure temperature measurements. PU Page 7 of 16 Version 1.2

8 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. PU Page 8 of 16 Version 1.2

9 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. PU Page 9 of 16 Version 1.2

10 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-rockforming 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 PU Page 10 of 16 Version 1.2

11 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 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 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 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 Alum Shale Basin, Scandinavia The Alum Shale was deposited during the Middle Cambrian to Early Ordovician Period (approximately 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. PU Page 11 of 16 Version 1.2

12 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 ( 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 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) 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) 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). PU Page 12 of 16 Version 1.2

13 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 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). PU Page 13 of 16 Version 1.2

14 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., Quantifying the anisotropy and tortuosity of permeable pathways in clay-rich mudstones using models based on X-ray tomography. Scientific Reports, 7(1), p PU Page 14 of 16 Version 1.2

15 6. Bibliographical references 1 Andrews, I.J 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 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 Elucidation of the Alum Shale kerogen structure using a multidisciplinary approach. Organic Geochemistry, 23 (11/12), Bruns, B. et al Petrolium systems evolution in the inverted Lower Saxony Basin, northwest Germany: A 3D basin modelling study. Geofluids, 13, Bruns, B. et al 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, Charpentier, R.R., and Cook, T.A., USGS methodology for assessing continuous petroleum resources: U.S. Geological Survey Open-File Report , 75 p. 7 Department of Energy and Climate Change, The unconventional hydrocarbon sources of Britain s onshore basins shale gas. 8 Fraser A. J. and Gawthorpe R. L., Tectono-stratigraphic development and hydrocarbon habitat of the Carboniferous in northern England. Geological Society, London, Special Publications, 55, 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 , 2 p. (Available at 10 Ghanizadeh, A. et al., 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, Ghanizadeh, A. et al., 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, Kiersnowski, H. and Dyrka, I., 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): Nielson, A. T., et al The Lower Cambrian of Scandinavia: Depositional environment, sequence stratigraphy and palaeogeography. Earth-Science Reviews, 107, PU Page 15 of 16 Version 1.2

16 14 Mascle, A. & Vially, R, 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, Marty, B., et al., Low enthalpy geothermal fluids from the Paris sedimentary basin 1. Characteristics and origin of gases. Geothermix, 17 (4), Monaghan, A. A 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 Fluid systems and basin evolution of the western Lower Saxony Basin, Germany. Geofluids, 7, Pawlewicz, M.J. et al Map showing geology, oil and gas fields, and geologic provinces of Europe including Turkey. U. S. Geological Survey, open file report I 19 Quesada, S. et al 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), Stampfli, G. M., et al The formation of Pangea. Tectonophysics, 593, Thickpenny, A The sedimentology of the Swedish Alum Shales. Geological Society, London, Special Publications, 15, Thickpenny, A 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.), Tissot B., et al Influence of nature and diagenesis of organic matter in formation of petroleum. AAPG Bulletin, 58 (3), Underhill, J.R. et al Controls on Structural Styles, Basin Development and Petroleum Prospectivity in the Midland Valley of Scotland. Marine and Petroleum Geology, 25, U.S. Energy Information Administration (EIA), September Technically recoverable shale oil and shale gas resources: Other Western Europe U.S. Energy Information Administration (EIA), September Technically recoverable shale oil and shale gas resources: Poland U.S. Energy Information Administration (EIA), September Technically recoverable shale oil and shale gas resources: Spain U.S. Energy Information Administration (EIA), September Technically recoverable shale oil and shale gas resources: United Kingdom Waters, C.N. et al., Lithostratigraphical framework for Carboniferous successions of Great Britain (Onshore). British Geological Survey Research Report, RR/07/01/ 60pp. PU Page 16 of 16 Version 1.2