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PETROLEUM SYSTEM RESERVOIR SEAL TRAP - Coggle Diagram
PETROLEUM SYSTEM RESERVOIR SEAL TRAP
Petroleum Trap
a configuration of rocks suitable for containing hydrocarbons and sealed by a relatively impermeable formation through (hydrocarbon cannot migrate)
Petroleum trap (2 type)
structural traps
formed because of deformation in rock layer that contains the hydrocarbon
two common example of structural traps are fault traps and anticlines
stratigraphic traps
formed by lithological changes (during or after deposition)
Structural Trap
primary result of folding and faulting or both
Fault Trap
occurs when the formations on either side of the fault have been moved into a position that prevents futher migration of petroleum
ex: an impermeable formation on one side of the fault may have moved opposite the petroleum-bearing formation on the other side of the fault
further migration of petroleum is prevented by the impermeable layer
Anticlinal Trap
is an upward fold in the layers of rock, much like an arch in abuilding
petroleum migrated into the highest part of the fold and its escape is prevented by an overlying bed of impermeable rock
Petroleum Trap
a trap may contain oil, gas or both
oil water contract (OWC): the deepest point of the oil can be removed
GOC or GWC: the lowest limit of gas production
the contract of the fluid is horizontal and flat, if tilted it is caused by
Hydrodynamic flow
production
slope of the trap
tar formation at the bottom
facies changes (grain size)
Stratigraphy Traps
formed by lithological changes: deposition or erosion (unconformity)
more difficult to find and detect
smaller in size
this trap is result when the reservoir bed is sealed by other beds or by a change in porosity or permeability within the reservoir bed itself
there are many diff kinds of stratigraphic traps
a tilted or inclined layer of petroleum-bearing rock is cutoff or truncated by an essentially horizontal, impermeable rock layer.
The effectiveness of
the cover rock
Lithology
Ductility
Thickness
Lateral continuity
Burial depth
Cap Rock (Seal)
secondary migration proceeds until an impermeable barriers is encounted that prevents futher flow
the most common seal is shale layer
the most effective seals are evaporites, notably salt and anhydrite
partly because of their inherently low permeability
partly because their capacity for viscous flow enables them to heal fractures and fault
seal rocks prevents petroleum from leaking out of a trap
Timing of trap formation
the timing of trap formation is essential to prospect evaluation
a trap that developed too late to receive a petroleum charge will filled with pore water
all type of trap need exactly trap timing
deposional an unconformity traps are very early, sating from the time the sealing units became effective
thus these trap are ready to receive a charge from a very early stage
Petroleum Alteration
changes in petroleum composition due to biodegradation
changes in petroleum composition due to thermal alteration
other alteration processes leading to compositional changes in petroleum