08_SaltTectonics
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Transcript of 08_SaltTectonics
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GEOFÍSICA APLICADA À PROSPECÇÃO DE HIDROCARBONETOS
Leonardo Azevedo
Aula 8 – 12 Mar. 2013
Salt Tectonics
1 Leonardo Azevedo, 2013
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Salt Tectonics: Introduction
• Salt: mineral (Halite) and evaporitic rock (frquently
associated with siliciclastic, chalk, anhydrite).
• Both divergent (sin-rift/post-rift) and convergent
environments.
• Very ductile and low density.
• Halokinetis – deformation and movement of the sediments
above the salt layer.
• Sedimentary structures depend on the type of sediments
and the trigger event that lead to the salt movement.
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Evaporties: origin and generation
• Marine precipitates, by the evaporation of the sea water;
• Evaporites are formed when the evaporation rate is higher than the precipitation;
• Short periods of comunications with less salty waters;
• Nowaday, the deposition of evaporites is constrained to tidal and estuarines
areas;
• Variable thickness and impermeable!
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Salt Tectonics: introduction
• Various types of potential HC’s traps and
several types of morphologies.
• Very often associated with faults.
• Main Basins: Angola, Brasil e México
Leonardo Azevedo, 2013
Zagros Mountains
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Salt Tectonics: Buoyancy and deifferential compaction
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Salt Tectonics: Sedimentaitons
Leonardo Azevedo, 2013
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7 Jürgen Adam, Zhiyuan Ge, Marianela Sanchez (2012). Salt-structural styles and kinematic evolution of the Jequitinhonha
deepwater fold belt, central Brazil passive margin. Marine and Petroleum Geology, 37 (1).
Salt Tectonics : Main Geometries
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Salt Tectonics : Diapirism
SALT
Reactive:
Extension creates room for diapir.
Stairstep faulting above.
Salt
Active:
Diapir creates room.
Thining and arching above.
Drag on flanks
Salt
Passive:
No room problem.
Diapir in equilibrium
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Offshore France
Salt Tectonics
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• Chaotic/transparent texture;
• Salt top with stronger reflection but hard spatial interpretation;
• Velocity anomalies beneath salt bodies;
• In post-stack migration there are no reflection beneath the salt bodies.
Seismic Interpretation
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Salt Geometries: Salt pillow
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Salt Geometries: Salt Diapirs
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Feda Graben - Dinamarca
Salt Geometries: Salt Diapirs
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Salt Geometries: Diapirs - Norway
VSA
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Salt Geometries: Salt Domes
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Paul J Valle, John G Gjelberg, William Helland-Hansen(2001). Tectonostratigraphic development in the eastern
Lower Congo Basin, offshore Angola, West Africa. Marine and petroleum geology 18 (8).
Salt Geometries: rafts
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Salt Geometries: rafts
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Salt Geometries: Canopy
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North Sea
Exercício
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Exercício Gabão – Delta do Congo
Angola
Courtesy – CGGVeritas Leonardo Azevedo, 2013
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Horizontal time slices
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Mar do Norte (Coerência)
Off W. Africa (Azevedo 2009)
Seismic Attributes
Leonardo Azevedo, 2013