www.jpg.co.uk Journal of Petroleum Geology, Vol. 39(3), July 2016, pp 305-326 305 PETROLEUM SYSTEMS OF THE WEST IBERIAN MARGIN: A REVIEW OF THE LUSITANIAN BASIN AND THE DEEP OFFSHORE PENICHE BASIN N. Pimentel1* and R. Pena dos Reis2 The relatively well-studied Lusitanian Basin in coastal west-central Portugal can be used as an analogue for the less well-known Peniche Basin in the deep offshore. In this paper the Lusitanian Basin is reviewed in terms of stratigraphy, sedimentology, evolution and petroleum systems. Data comes from published papers and technical reports as well as original research and field observations. The integration and interpretation of these data is used to build up an updated petroleum systems analysis of the basin. Petroleum systems elements include Palaeozoic and Mesozoic source rocks, siliciclastic and carbonate reservoir rocks, and Mesozoic and Tertiary seals. Traps are in general controlled by diapiric movement of Hettangian clays and evaporites during the Late Jurassic, Late Cretaceous and Late Miocene. Organic matter maturation, mainly due to Late Jurassic rift-related subsidence and burial, is described together with hydrocarbon migration and trapping. Three main petroleum systems may be defined, sourced respectively by Palaeozoic shales, Early Jurassic marly shales and Late Jurassic marls. These elements and systems can tentatively be extrapolated offshore into the deep-water Peniche Basin, where no exploration wells have so far been drilled. There are both similarities and differences between the Lusitanian and Peniche Basins, the differences being mainly related to the more distal position of the Peniche Basin and the later onset of the main rift phase which was accompanied by Early Cretaceous subsidence and burial. The main exploration risks are related to overburden and maturation timing versus trap formation associated both with diapiric movement of Hettangian salt and Cenozoic inversion. INTRODUCTION conjugate margin of eastern Canada are the Jeanne d’Arc and Whale Basins (cf. Wilson et al., 1989; The West Iberian margin is one of the least explored Pinheiro et al., 1996; Peron-Pinvidic and Manatschal, of the North Atlantic margins. A number of on- and 2009) where major oil and gas fields include Hibernia offshore basins are present in West Iberia including (1016 MM brls) and Terra Nova (170 MM brls) in the mainly onshore Lusitanian Basin and the deep Newfoundland, and Sable (2.7 TCF) and Deep Panuke offshore Peniche Basin (Fig. 1). Counterparts in the (659 BCF) in Nova Scotia (CNSOPB, 2013). However no comparable discoveries have so far been made in 1 Instituto Dom Luiz, Faculdade de Ciências da the West Iberian margin. Universidade Lisboa, Campo Grande C-6, 1749-016 Exploration of the West Iberian margin began in Lisboa, Portugal. 2 Centro de Geociências, Faculdade de Ciências e the 1930s. Seismic data was acquired over the next Tecnologia da Universidade de Coimbra, Lg Marquês de Pombal, 3000-272 Coimbra, Portugal. Key words: Lusitanian Basin, Portugal, Peniche Basin, Iberian margin, North Atlantic, petroleum systems, source * Corresponding author, email: [email protected] rocks, rifts, pre-salt plays, diapirs. © 2016 The Authors. Journal of Petroleum Geology © 2016 Scientific Press Ltd Pimentel.indd 305 27/05/2016 12:14:16 306 Petroleum systems of the West Iberian margin 13°W 12°W 11°W 10°W 9°W 8°W 7°W 6°W Atlantic Ocean FRANCE 43°N 43°N N PORTUGAL SPAIN Mediterranean Sea 42°N Figure 2 42°N Galicia Porto Basin Basin Bragança Chaves Porto 41°N Figure 3 41°N Porto-Tomar Lousã-CaldasPORTUGAL 40°N Bb 40°N Distal Peniche Peniche Castelo Branco Basin Basin Nazaré SPAIN Arrife 39°N 39°N V.F. Bb Lusitanian Basin LISBON Pinhal Novo Arrábida 38°N 38°N LEGEND Messejana Central Iberian Zone - Plasencia South Portuguese Zone Avalonia Ossa-Morena Zone Alentejo Basin 37°N 37°N Ss Algarve Basin Gb 0 15 30 60 90 120Km. 36°N 36°N 12°W 11°W 10°W 9°W 8°W 7°W Fig. 1. Location map of the West Iberian margin of Portugal with the mainly onshore Lusitanian Basin and deeper-water offshore basins including the Peniche Basin. Bb, Berlengas Block. Red lines show the conjugate NNW-SSE and NE-SW fault system. Inset shows the Palaeozoic Iberian basement zones (Ribeiro et al., 1990). Boxes mark the areas of Figs 2 and 3. 40 years and 78 wells were drilled with oil shows (operator), Kosmos, GALP and Partex). Meanwhile, and sub-commercial discoveries recorded (UPEP, the Lusitanian Basin (onshore and shallow offshore) 2016). Increased seismic acquisition took place in was explored by Mohave Oil & Gas from 1998 to the 1970s with the drilling of 22 offshore wells (Fig. 2014, with 2D and 3D seismic acquisition, nine wells 2). The margin was further explored between 1978 and signifi cant oil and gas shows recorded. and 2004 (particularly the Porto Basin: Fig. 1), and Recent exploration activity in the West Iberian an additional 28 wells were drilled with a few oil margin has focused on the deep offshore with new 2D shows (Fig. 2). The deeper offshore has been covered and 3D seismic campaigns, as well as aerial gravimetric by a seismic campaign (TGS-NOPEC 99-02; UPEP, surveys of both onshore and offshore areas (UPEP, 2016) (Fig. 2), and concessions in 2007 included 2016). Little direct information about the sedimentary three blocks in the Alentejo Basin (ENI (operator) and infi ll of the deep offshore basins is available due to the GALP) and four blocks in the Peniche Basin (Repsol absence of wells in water depths greater than 200m Pimentel.indd 306 27/05/2016 12:14:18 N. Pimentel and R. Pena dos Reis 307 42°N 11°W 10°W 9°W 8°W 42°N SPAIN N 200m Porto Galicia 2000m Basin Lu-1 Basin Lm-1 North Atlantic Porto Ocean 41°N 398 5A-1 41°N PORTUGAL 901 12C Ca-1 5A Do-1 5B 200m 2000m Mo-1 Ve-1 Bb 13E-1 40°N 13C-1 14C-1 40°N MRW 14A Distal Fa-1 Vm-1 Peniche SPM-2 4A Basin 16A-1 Peniche 17C-1 4B 12A Basin 200m 12B PW-4 20B-1 Lusitanian Basin Bf-1 39°N 8 Mo-1 39°N Bb SB-1 2000m LEGEND Profiles of seismic LISBON lines in Figs. 4,5,8, Br-2 & 12 Outcrop oil Br-1 seeps Wells with oil shows Figure 3 Go-1 Offshore wells ODP sites Pe-1 38°NModelled wells Alentejo 38°N (Fig.9) 0 15 30 60 90 120km. Bathymetry Basin 11°W 10°W 9°W 8°W Fig. 2. Regional map of the Portuguese margin showing the location of the main TGS-NOPEC seismic lines (red), offshore wells, wells with oil shows, and locations of oil seeps (after UPEP, 2016). Purple lines show the profiles of seismic sections reproduced in Figs 4, 5, 8 and 12. Crosses mark the locations of modelled wells SB-1 and PW-4 (Fig. 9). Box marks the area of Fig. 3. (Fig. 2). However the sedimentary fill in the deep Available data offshore may be extrapolated from the outcrop geology Overviews of the geology and evolution of the of the onshore areas which has been well documented Lusitanian Basin include Witt (1977), Ribeiro et al. (e.g. Alves et al., 2003, 2006, 2009; Pereira et al., 2011, (1979), Wilson (1988), Wilson et al. (1989), Rasmussen 2012; Pena dos Reis et al., 2011). et al. (1998), Azerêdo et al. (2003), Dinis et al. (2008), In this paper we present an overview of the Pena dos Reis et al.(2000, 2011) and Kullberg et al. Lusitanian Basin and of the related petroleum systems (2013). To complement this published information, the and elements, and discuss possible correlations with fill of the Lusitanian Basin was studied at 38 outcrop the deep offshore Peniche Basin. The paper integrates locations in terms of stratigraphy, sedimentology and outcrop and subsurface data from the onshore with lithofacies variations (Atlantis, 2010). In addition recently-acquired seismic data from the offshore. to these outcrop studies, more than 50 well reports were studied for different stratigraphic intervals. Pimentel.indd 307 27/05/2016 12:14:19 308 Petroleum systems of the West Iberian margin 9°W LEGEND Tertiary sediments overlying the Porto Lusitanian basin succession or resting on Palaeozoic basement (Aveiro, Mondego, Tejo Basins) ¬ 41°NLusitanian Basin succession at outcrop: 41°N Cretaceous Jurassic CIZ Triassic Mesozoic (undiff.) exposed offshore Palaeozoic basement Aveiro exposed at outcrop. Basin Diapirs Major faults Palaeozoic Boa Viagem Terranes CIZ, OMZ,SPZ Terrane boundaries Montemor-o-Velfio Coimbra Coastline Cabo Mondego 40°N Mondego 40°N Pedrógão Basin Atlantic Lousã Caldas Ocean S. Pedro de Muel Leiria OMZ Vale Furado Tomar Nazaré Fig. 10A SPZ ALC-1 Arrife Porto de Mós Lousã Caldas Peniche OMZ CP-1 OMZ Torres Vedras Santa Cruz Tejo Torres Fx-1 Basin Vedras Sb-1 39°N 39°N Villa Franca Fig. 3. Map showing structural and tectonic SPZ elements of the Lusitanian Basin, west-central Portugal. Mesozoic geology based on LNEG, LISBON 2010; Palaeozoic basement based on Pena dos Reis et al. (2012). Palaeozoic terranes: CIZ – Central Iberian Zone; SPZ – Southern Portuguese Zone; OMZ – Ossa Morena Zone. Outcropping diapirs with Hettangian evaporites are marked by pink polygons. 0 15 30 60 km. Arrábida White dashed line shows the profi le line of the 9°W seismic section in Fig. 10a. Finally, published regional and local 2D seismic For the Peniche Basin, no direct data are available lines (vd. Rasmussen et al., 1998; Kullberg, 2000) except for some recent piston-core studies of the and a comprehensive seismic interpretation report seabed, so the basin is known mainly from seismic data (Lomholt et al., 1996) were used to investigate basin (e.g.