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A Field Analogue for Buried Karst Reservoirs in the NW-Mediterranean

Eglantine Husson, Michel Seranne, Hubert Camus, Pierre Jean Combes, Renaud Couëffé, Mihaela Carmen Melinte-Dobrinescu, Marie José Fondecave-Wallez, and Bernard Peybernès

Tethysian carbonate platforms around the NW-Mediterranean make one of the carbonate reservoirs in an area otherwise dominated by silicoclastic reservoirs. Mesozoic carbonate massifs in the South of France are well exposed and deeply incised by canyons, which provide an opportunity to analyze: 1) the physical properties of karstified massifs, 2) the distribution of karst facies (carbonate matrix alteration and karst infill) with respect to base-level. The study area stands as a unique field analogue of the Mesozoic carbonate reservoirs buried beneath the Neogene rift-drift marine sequences in the Mediterranean.

Karst events can be distinguished by their specific karst infill. Distribution of karst facies is controlled by the position along an upstream-downstream profile. Discrete karst conduits are observed upstream. The middle part displays pervasive dissolution-induced brecciation, which affects volumes 10’s of m thick and 100’s of m wide; an evolved facies corresponds to collapse breccia. Finally, breccia deposition in small alluvial fan or fan-delta is found in the downstream parts of the profile.

Similarly, karst infill depends on its position with respect to the base-level: fine to coarse sediments partly fill cavities above, while fine silts and clay settle below the base-level.

Multiple karstification phases in the NW Mediterranean (including the iconic Messinian desiccation event) have affected carbonate massifs over wide (presently) coastal areas and deep extend , which constitute a target as they have a high storage capacity for water or hydrocarbon.

AAPG Search and Discovery Article #90161©2013 AAPG European Regional Conference, Barcelona, Spain, 8-10 April 2013