See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/322739556 An introduction to the Triassic: Current insights into the regional setting and energy resource potential of NW Europe Article in Geological Society London Special Publications · January 2018 DOI: 10.1144/SP469.1 CITATIONS READS 3 92 3 authors, including: Tom Mckie Ben Kilhams Shell U.K. Limited Shell Global 37 PUBLICATIONS 431 CITATIONS 11 PUBLICATIONS 61 CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: Reconstructing the Norwegian volcanic margin View project Paleocene of the Central North Sea: regional mapping from dense hydrocarbon industry datasets. View project All content following this page was uploaded by Ben Kilhams on 22 November 2019. The user has requested enhancement of the downloaded file. Downloaded from http://sp.lyellcollection.org/ by guest on January 26, 2018 An introduction to the Triassic: current insights into the regional setting and energy resource potential of NW Europe MARK GELUK1*, TOM MCKIE2 & BEN KILHAMS3 1Gerbrandylaan 18, 2314 EZ Leiden, The Netherlands 2Shell UK Exploration & Production, 1 Altens Farm Road, Nigg, Aberdeen AB12 3FY, UK 3Nederlandse Aardolie Maatschappij (NAM), PO Box 28000, 9400 HH Assen, The Netherlands *Correspondence: [email protected] Abstract: A review of recent Triassic research across the Southern Permian Basin area demon- strates the role that high-resolution stratigraphic correlation has in identifying the main controls on sedimentary facies and, subsequently, the distribution of hydrocarbon reservoirs. The depositio- nal and structural evolution of these sedimentary successions was the product of polyphase rifting controlled by antecedent structuration and halokinesis, fluctuating climate, and repeated marine flooding, leading to a wide range of reservoir types in a variety of structural configurations. Triassic hydrocarbon accumulations form an important energy resource across the basin, not only in the established Buntsandstein fairway but also in Rogenstein oolites and Muschelkalk carbonates. In addition, sand-prone sections in the Late Triassic, such as the Schilfsandstein, have the potential to be hydrocarbon reservoirs. Several Triassic intervals are now the focus for developing geothermal projects. A detailed understanding of Triassic reservoir quality and distribution is one of the main keys to efficiently unlocking the geothermal and remaining hydrocarbon potential across the basin. A concise overview of the stratigraphic and palaeo- basin-wide reservoir and seal units from the UK in geographical development of the Triassic is pre- the west to Poland in the east (Dadlez et al. 1998; sented here, including recent insights into the Lokhorst 1998; Evans et al. 2003; Geluk 2005; understanding of these complex systems. The chap- Feist-Burkhardt et al. 2008; McKie & Williams ters in this Special Publication deal mainly with the 2009; Bachmann et al. 2010; Barnasch 2010). These Triassic as a hydrocarbon reservoir, including explo- correlations can also be tied, supported by magneto- ration aspects in the Dutch and German offshore stratigraphy (Szurlies et al. 2012) and limited biostra- (Kilhams et al. 2018; Kortekaas et al., this volume, tigraphy (Kürschner & Herngreen 2010; Backhaus in press), the impact of overpressure models in the et al. 2013; Scholze et al. 2017), to equivalent succes- Terschelling Basin (Peeters et al., this volume, in sions further afieldintheNorthSeaarea,thusassisting press), the use of open access well data (van Kempen in developing an understanding of the regional palae- et al., this volume, in press) and enhanced gas recov- ogeographical evolution in response to tectonics and ery from the mature De Wijk gas field (Goswami climate. It has also become apparent that, for many et al. 2018). Franz et al. (this volume, in press) regions, much of the Permian and Triassic time periods also consider the deltaic systems of the Rhaetian and are missing in the sedimentary record (Fig. 1). their use as geothermal reservoirs in northern Ger- Antecedent Caledonian, Variscan and Permian many. An overview of historical Triassic hydrocarbon structures had a great bearing on the structural and discoveries and possible future geothermal aspects is depositional processes that operated in these basins. introduced as a framework for these chapters. The principal controlling lineaments are the Iapetus Suture and the Trans-European Suture Zone, mark- ing the northern margin of the Caledonian collision Triassic basin evolution (Smit et al. 2016). North of this line, focused rift tec- tonics prevailed; whereas, to the south, a wide exten- Over the last decade, various studies in NW Europe sion zone existed in areas of thickened Variscan crust have resulted in new insights into the sedimentary (Praeg 2004). As a result, the SPB is a complex amal- and tectonic evolution and resource potential of gamation of linked depocentres (e.g. the Polish the Triassic in the Southern Permian Basin (SPB). Trough, North German and Sole Pit basins). Fault High-resolution stratigraphic correlations have been systems inherited from earlier Permian rift systems carried out in order to consolidate the different strati- formed the backbone of the later Triassic graben sys- graphic frameworks in NW Europe, and to identify tems (Coward et al. 2003). During the Triassic, From:KILHAMS, B., KUKLA, P. A., MAZUR, S., MCKIE, T., MIJNLIEFF, H. F. & van OJIK, K. (eds) Mesozoic Resource Potential in the Southern Permian Basin. Geological Society, London, Special Publications, 469, https://doi.org/10.1144/SP469.1 © 2018 The Author(s). Published by The Geological Society of London. All rights reserved. For permissions: http://www.geolsoc.org.uk/permissions. Publishing disclaimer: www.geolsoc.org.uk/pub_ethics Downloaded from http://sp.lyellcollection.org/ by guest on January 26, 2018 M. GELUK ET AL. Fig. 1. Chronostratigraphic diagram of the Permian and Triassic deposits in The Netherlands and adjacent areas (after Geluk 2005). Stage names and numerical ages are after Cohen et al. (2013). ‘Golden spikes’ are indicated. The Induan and Olenekian replace the former Scythian. Two intra-Triassic unconformities are present – the Hardegsen Unconformity (Olenekian) and the Early Cimmerian Unconformity (Norian). Over large areas of the Southern Permian Basin, these unconformities result in large intervals of missing section. Downloaded from http://sp.lyellcollection.org/ AN INTRODUCTION TO THE TRIASSIC byguestonJanuary26,2018 Fig. 2. Geological cross-sections of various Triassic basins in NW Europe: T1, Lower and Main Buntsandstein; T2, Solling, Röt and Muschelkalk; T3, Keuper; JJ, Jurassic. Note the difference in scale between these basins, with the thickest Triassic successions in the Glückstadt and Horn graben. The depth scale is in kilometres. Two-fold vertical exaggeration. Modified after Geluk (2005) and references therein. Downloaded from http://sp.lyellcollection.org/ by guest on January 26, 2018 M. GELUK ET AL. progressive basin modification by extensional tec- conditions throughout the Triassic (Fig. 3), although tonics occurred as a result of fault propagation from the degree of aridity fluctuated across the region, both the Boreal and Tethyan regions (Bachmann possibly in response to warming induced by volca- et al. 2010). From the Middle Triassic onwards, rift- nism from Large Igneous Provinces and, more ing concentrated mainly in the Central and Northern locally, by episodic marine flooding increasing North Sea, and the Horn and Glückstadt grabens humidity. Warming may have influenced monsoon (Fig. 2), together with onshore graben in the UK strength, evaporation rates, temperature gradients and eastern France (Bourquin et al. 1997, 2002; Ruf- and the ability of monsoons to penetrate the conti- fell & Shelton 1999). The degree of extension across nental interior (McKie 2014). In response to these the basins varied and resulted, in combination with changes, fluvial systems cyclically expanded and the pre-existing structural grain and the presence of contracted across the basin, alternating with wide- underlying mobile Zechstein salt, in a wide variety spread playa, aeolian dune fields and, more rarely, of tectonic structures (Fig. 2). perennial lakes. Larger-scale eustatic sea-level The palaeolatitude and location of the SPB within changes caused episodic flooding of the SPB and Pangea resulted in generally arid to semi-arid provided a fluctuating base level that also controlled Fig. 3. Synopsis of Triassic climatic settings. (a) Late Triassic (Carnian–Norian) Pangean climate zonation (after Sellwood & Valdes 2007), placing the SPB region in the arid to semi-arid zone (red rectangle). (b) North to south climate variations through the Triassic (modified after McKie 2017). The plots are qualitative, with relatively drier conditions to the left and wetter to the right. O, Olenekian; A, Anisian; L, Ladinian; C, Carnian; N, Norian; R, Rhaetian; ITCZ, Intertropical Convergence Zone. Downloaded from http://sp.lyellcollection.org/ by guest on January 26, 2018 AN INTRODUCTION TO THE TRIASSIC Fig. 4. Illustrative Triassic palaeogeographical reconstructions (after McKie 2017): (a) Main Buntsandstein (Olenekian) fluvial–aeolian deposition within continental basins; (b) Röt (Lower Anisian) restricted marine connection and evaporites; (c) Lower Muschelkalk marine flooding (Anisian); (d) Middle Muschelkalk basin restriction and evaporate