SALT TECTONICS

Field examples of seismic-scale structures and associated potential reservoirs

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Salt tectonics structures and their associated sediments are classic targets for hydrocarbon exploration. Recently, the south-central Pyrenees are becoming an excellent lab to test Mesozoic seismic-scale structures controlled by salt tectonics, in places not too overprinted by posterior Alpine compression. We illustrate analogue examples for drilled structures where seismic data do not provide an image, and we consider the role of salt in influencing the distribution of potential reservoir facies and fracturing in the adjacent hostrocks. This course is partially based on the paper Rising and falling diapirs, shifting depocenters, and flap overturning in the Cretaceous Sopeira and Sant Gervàs subbasins (Ribagorça basin, southern Pyrenees),Tectonics, 2016, by E. Saura, L. Ardèvol, A. Teixell and J. Vergés, and forthcoming papers in progress.

Cost: € 1,000
Dates: October 2-6, 2017 (closing date September 18)
Instructors: Lluís Ardèvol i Oró and Jon Gutmanis
Assistants: Marc Tudela and Davinia Díez-Canseco
Guest speaker: Jaume Vergés (Institute of Earth Sciences Jaume Almera, Barcelona)
Location: south-central Pyrenees, the course begins and ends in Barcelona
Meeting point: Barcelona, Cullera de Boix bar, 26 Ronda Sant Pere; October 2, 14:00h/after lunch
Trip end: October 6, Barcelona airport 17:30h; meeting point around 18:00h
Level: basic / skill
Delivery: field trip + 1h daily classroom
Physical demand: average hike (maximum 1h walk per day) with some hills

FIELD TRIP OUTLINE

Outcrops

  • Ribagorça basin, Senterada minibasin, Alinyà anticline
  • Triassic shales and evaporites: the role played by halite in the development of hydrocarbon reservoirs and in sealing
  • Lower Cretaceous shoreface and foreshore grainstones
  • Upper Cretaceous shelf / reefal / outer shelf carbonates and flysch deposits

Passive salt structures (minibasin stage)

  • Rise and fall of diapirs
  • Salt withdrawal minibasins, salt walls
  • Halokynetic sequence stratigraphy: hook and wedge sequences
  • Reservoir distribution: facies, fracture analysis, structural and stratigraphic traps
  • Overturned minibasin wings

Reactive salt structures (extensional stage)

  • Raft tectonics: extensional fault footwalls
  • Salt rollers – rollovers
  • Halokinetic breccias / cap rock
  • Carbonate lentils
  • Folds with large overturned flaps (flap folding)
  • Flip-flop salt walls

Active salt structures (compressional stage)

  • Toe-thrusts anticlines
  • Turtle-structure anticlines; rim synclines
  • Squeezed diapirs
  • Salt and fault welds: criteria for their recognition in the field; salt welds vs Alpine faults
  • Salt canopies and allochthonous sheets

Classroom

  • Geomechanical and fracture properties of salt and influence on sealing and reservoir development