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Petroleum System: Seal and Trap - Coggle Diagram
Petroleum System:
Seal and Trap
Cap Rock (seal)
an impermeable rock (as barrier to
further migration of HC liquid)
Properties:
-commonly shale, mudstone, anhydrite, salt
-estimate sealing efficiency based upon
~lateral extent and continuity
~permeability
~presence/absence of fault and fractures
effectiveness:
-lithology
-ductility
-thickness
-lateral continuity
-burial depth
Reservoir
subsurface body of rock with porosity and permeability to store and transmit fluids
-normally sedimentary rocks (porous)
Characteristics
-produce HC when buried and heated
-may contain recoverable HC resources
-prevent HC from passing (trap)
Trap
configuration of rock for HC
sealed by impermeable formation
Structural Trap
(result of faulting/folding)
anticlinal trap
(petroleum migrate into highest part of fold)
fault trap
(petroleum migration is prevented by impermeable layer)
Stratigraphic trap
HC trap that result from changes in
rock type or pinch-outs, unconformity or other
sedimentary features like reefs or buildups
difficult to find and detect/small in size
result from reservoir bed being trapped/
porosity or permeability change
Petroleum Alteration
petroleum composition change due to
-biodegradation
-thermal alteration
asphaltenes sink due to high density (gravity segregation)
-oil and water contact (NSO rich heavy oil build up)
-reservoir pressure (strata uplift) cause phase changes