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PSThe Role of Active Structural Growth in Controlling Deep-Water Reservoir Systems and Petroleum Prospectivity in the Confined Gulf of Lion Basin, Western Mediterranean

By

Roman S. Ianev1, Nathalie Bordas-Le Floch1, John R. Underhill2, and Richard J.W. Bunt1

 

Search and Discovery Article #10124 (2007)

Posted May 8, 2007

 

Adapted from poster presentation at AAPG Annual Convention, Long Beach, California, April 1-4, 2007

 

1Melrose Resources plc, Exchange Tower, 19 Canning Street, Edinburgh, EH3 8EG, U.K. ([email protected])

2Grant Institute of Earth Sciences, School of Geosciences, The University of Edinburgh, King's Buildings, West Mains Road, Edinburgh, EH9 3JW, U.K.

 

Abstract 

The interpretation of a recently acquired regional 2-D seismic survey and its integration with onshore field exposures in neighbouring parts of Southern Europe has led to renewed exploration interest in Neogene (Mio-Pliocene) deep-water reservoir plays in the confined Gulf of Lion Basin in the Western Mediterranean. It can now be shown that the basin originated in the Oligocene as a syn-sedimentary extensional back-arc system that included the analogous Sarcidano Basin of Sardinia.  

Subsequent Miocene-Recent post-rift subsidence was allied to increasing sediment supply due to increased run off from the developing Alpine and Pyrenean mountain belts. As a result the basin became increasingly dominated by turbiditic deposition as part of an upward-shoaling succession during the Miocene.  

The basin fill subsequently records a dramatic shallowing episode during the Late Miocene (Messinian) in response to desiccation of the Mediterranean Sea with the development of deeply incised canyons in proximal areas and thick evaporite deposits in the offshore.  

Post-rift sedimentation resumed on the margin following Pliocene transgression. Burial and tilting triggered decollement on the mobile Messinian evaporites and down-slope movement of the Plio-Quaternary sediments with the formation of a spectacular linked extensional-translation-compressional system of normal faults and folds with concomitant effects on sedimentation. Interpretation of seismic facies demonstrates how active structural growth of the mobile evaporite system controlled sediment dispersal patterns and petroleum prospectivity in the sub-salt and supra-salt turbidites. Furthermore, basin subsidence and modelling of the source rock maturation histories has provided a testable model of the newly identified play opportunities.

 

uAbstract

uRegional setting

uGeodynamic setting

uRift tectonics

uSarcidano field analogue

uMessinian salinity crisis

uSalt tectonic control

uImplications

uReferences

uAcknowledgments

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

uAbstract

uRegional setting

uGeodynamic setting

uRift tectonics

uSarcidano field analogue

uMessinian salinity crisis

uSalt tectonic control

uImplications

uReferences

uAcknowledgments

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

uAbstract

uRegional setting

uGeodynamic setting

uRift tectonics

uSarcidano field analogue

uMessinian salinity crisis

uSalt tectonic control

uImplications

uReferences

uAcknowledgments

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

uAbstract

uRegional setting

uGeodynamic setting

uRift tectonics

uSarcidano field analogue

uMessinian salinity crisis

uSalt tectonic control

uImplications

uReferences

uAcknowledgments

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

uAbstract

uRegional setting

uGeodynamic setting

uRift tectonics

uSarcidano field analogue

uMessinian salinity crisis

uSalt tectonic control

uImplications

uReferences

uAcknowledgments

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

uAbstract

uRegional setting

uGeodynamic setting

uRift tectonics

uSarcidano field analogue

uMessinian salinity crisis

uSalt tectonic control

uImplications

uReferences

uAcknowledgments

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

uAbstract

uRegional setting

uGeodynamic setting

uRift tectonics

uSarcidano field analogue

uMessinian salinity crisis

uSalt tectonic control

uImplications

uReferences

uAcknowledgments

 

Regional Setting

(Figures 1RS-1 - 1RS-2)

 

The Gulf of Lion is a major sedimentary depocentre that lies in offshore French waters of the Western Mediterranean between the Riviera Coast and the islands of Corsica and Sardinia.

 

Geodynamic Setting 

(Figures 1GS-1 - 3-1)

 

The basin was formed as a result of Oligo-Aquitanian rifting in a back-arc setting, as subduction took place between Europe and Apulia during the latter stages of Alpine collision (Figure 1GS-1). The integration of structural and palaeomagnetic data demonstrates that syn‑sedimentary extension was limited to more north‑easterly areas and did not affect the area between the Spanish Coast and the southern Balaeric Islands (Majorca and Ibiza).  

Consequently, significant anti-clockwise rotation (>40 degrees) characterised the Gulf of Lion during early Miocene times (21.5-14 Ma - Figure 1GS-2). Rotation was accompanied by significant thinning of the continental crust and the development of quasi oceanic crust in more distal (central) parts of the basin (Figure 1GS-3).

 

Rift Tectonics and Eustatic Control on Sub-Salt Deposits 

(Figures 4RT-1 - 4RT-3)

 

Insights and Lessons from the Sarcidano Field Analogue 

(Figures 4S-1 - 4S-4)

Figure 4S-1. Chronostratigraphic and lithostratigraphic relationships in the Sarcidano Basin field analogue in Sardinia (modified after Monaghan, 2001).

Figure 4S-2. Location map showing the position of the Sarcidano Basin.

Figure 4S-3. Field photographs depicting the sedimentary and volcanoclastic facies variation that characterises the basin.

Upper pair: Alluvial fanglomerates of the Villanovatulo Member that fill early post-rift topography generated by Oligo-Miocene rifting. The coarse clastics appear to have entered the basin through discrete entry points centred upon relay ramps between prominent propagating normal fault tips.

Upper - Middle pair: Potential reservoir targets in the early post-rift succession include carbonates illustrated by exposures around the Isili Block and shallow marine clastics of Areci .

Lower - Middle pair: Evidence for contemporaneous volcanic activity is abundant and includes ignimbritic flows and dyke-like fumaroles cross-cutting tuffaceous sandstone.

Lower pair: left- Major sequence boundary at the base of the Plio‑Quaternary succession; right- Exposed major syn-sedimentary normal faults affecting the Cenozoic succession.

 

Stratigraphic sequences of Paleogene and Neogene age (Figure 4S-1) outcrop extensively on the Italian island of Sardinia (Figure 4S-2) and provide important insights both into the syn- and post‑rift evolution of the Gulf of Lion but also the reservoir potential and potential risks in the basin. The key exposures lie in and around the major NW-SE trending Sarcidano Basin (Sowerbutts and Underhill, 1998; Monaghan, 2001; Figure 4S-1). The stratigraphic succession is characterised by rapid temporal and spatial, facies, and thickness changes especially in the early stages of Oligo-Miocene extensional basin development (Sowerbutts and Underhill, 1998). This may be best exemplified in the central area where contemporaneous alluvial, shallow marine clastics, fault-block carbonates, and volcanoclastic (ignimbritic flows) all co-exist (Figure 4S-3). Their distribution and sedimentary character appears to be governed by competing extensional faulting, sediment supply, and volcanic processes (Figure 4S-4).

 

Messinian Salinity Crisis in the Western Mediterranean 

(Figures 5M-1 - 5M-3)

Figure 5M-1. Messinian desiccation is recorded in up-dip locations where canyons and incised valleys were created. The Messinian erosion surface beneath the western shelf: Part of seismic line (upper left) in detail; map of surface (upper right), with location of detailed segment of seismic line along with location of complete line (from Lofi et al., accepted); complete seismic line modified after Lofi et al., 2004).

Figure 5M-2. Seismic line in down-dip position. Down-dip, the Messinian record is completely different and consists of the erosional products in low-stand fan complexes. This phenomenon can be best illustrated using a sequence of depth structure and isopach maps.

Figure 5M-3. Isopach maps of the Early Messinian sequence recording the establishment of turbiditic and possibly deltaic (Messinian 4) systems: Messinian 2 (upper); Messinian 2 and 3 (middle), and Messinian 4 (lower).

 

Click to view sequence of isopach maps from upper Messinian to lower Messinian.

 

Salt Tectonic Control on Late Neogene Supra-Salt Deposits 

(Figures 6-1 - 6-7)

Figure 6-1. Four-way dip closures above salt pillows: seismic line (left) and top Messinian depth structure map (right). Early salt movement created topography: the highs were eroded while the depocentres around were infilled.

Figure 6-2. Listric fault-bound roll-over anticlines: seismic line (left) and detail of central part (right). They result from gravity driven salt movement towards the deepest part of the basin.

Figure 6-3. Structurally-constrained channel and levee turbiditic systems: seismic line (left) and detail of part with significant syn-tectonic fault growth. Flow direction is controlled by the movement along the listric faults: during the active tectonic phase, channel axes in the faulted area shift by 90° and run perpendicular to the slope, following the topography created by the salt movement.

Figure 6-4. Map of the listric faults in the roll‑over anticline zone (from Tadeu et al., 2005).

Figure 6-5. Isopach map of the Upper Pliocene. Note the thickening of the series in the listric fault area and the two distinct depocentres.

Figure 6-6. Isopach map of the Pleistocene. The sediment influx is now dominated by the Rhone.

Figure 6-7. Seabed depth map showing the present-day Rhone deep-sea fan.

 

Click to view in sequence maps of Upper Pliocene, Pleistocene, and present-day fan.

 

Implications for Hydrocarbon Prospectivity 

  • Recognition of pre-, syn- and post- rift play types.

  • Subdivision of post-rift into two play types: sub-salt (Pre- and Early Messinian ) and supra-salt (Late Messinian and Plio-Quaternary).

  • Field analogue in Sardinia highlights syn– and early post-rift sedimentary (reservoir) variability over remarkably short distances (1 to 10 km).

  • In contrast, later post-rift sequences display a more region-wide distribution in the Gulf of Lion.

  • Active growth of extensional faults creates a distinct roll-over anticline zone, the faulting in which determines deep-water reservoir sediment dispersal pattern in the Plio-Quaternary. Continuous subsidence provides accommodation space for the deposition of turbidite systems.

  • Future research will focus on source rock maturation and migration and its timing with respect to supra-salt trap formation.

 

References 

Dos Reis, A.T., Gorini, C., and Mauffret, A., 2005, Implications of salt-sediment interactions on the architecture of the Gulf of Lions deep-water sedimentary systems - western Mediterranean Sea: Marine and Petroleum Geology, v. 22, p 713-746.

Gattacceca, J., 2001, Cinematique du basin Liguro-Provencal entre 30 et 12 Ma. Implications geodynamiques. PhD, Ecole des Mines de Paris, Memoires des Sciences de la Terre no. 41, 299p.

Lofi, J., Berne, S., Clauzon, G., Gorini, Christian, Ryan, W.B.F., and Steckler, M., 2004, Erosional processes and palaeo-environmental changes in the Gulf of Lion (SW France) during the Messinian Salinity Crisis (5.96-5.32 My) - The Messinian Salinity Crisis Revisited, 20-24 August 2004, Corte.

Monaghan, A., 2001, Coeval extension, sedimentation and volcanism along the Cainozoic rift system of Sardinia, in Ziegler, P.A., Cavazza, W., Robertson, A.H.F., and Crasquin-Soleau, eds.: Peri-Tethys Memoir 6: Peri-Tethyan Rift/Wrench Basins and Passive Margins:. Mem. Mus.natn.Hist.nat., v. 186, p.707-734.

Sowerbutts, A.A., and Underhill J.R., 1998, Sedimentary response to intra-arc extension: controls on Oligo-Miocene deposition, Sarcidano sub-basin, Sardinia: Journal of the Geological Society. V. 155, p. 491-508.

 

Acknowledgments 

We are grateful to the following companies and persons for their contributions to the study of the Gulf of Lion and this poster preparation:

 

The Marine Geosciences team of IFREMER in Brest, France

Alison Sowerbutts from the British Geological Survey in Edinburgh, Scotland

TGS Nopec in Oslo, Norway

PGL in Banchory, Scotland

Gerard White from the University of Edinburgh, Scotland

 

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