Please enable JavaScript.
Coggle requires JavaScript to display documents.
PETROLEUM SYSTEM : MIGRATION & ACCUMULATION - Coggle Diagram
PETROLEUM SYSTEM : MIGRATION & ACCUMULATION
ACCUMULATION
The Continuous Accumulation
Formed in
source rocks
Eg: shale hydrocarbon reservoirs
Comprises only a
single reservoir
Not controlled by traps
Mainly accumulate in
situ
or near the generation of hydrocarbons (no prominent migration)
The Quasi-continuous Accumulation
Occurs in the
tight reservoirs adjacent to source rocks
No
defined boundaries
No or only
local edge&bottom water distribution
No regional
oil-gas-water inversion
Controlled by
non-anticline traps
The Discontinuous Accumulation
Conventional-trap
type
Occurs in
conventional
reservoirs
Clear boundaries&complete edge water or bottom water
Accumulation is mainly driven by
buoyancy
Controlled by various traps
(esp structural traps
)
MIGRATION
Primary
Migration of oil&gas out of the
fine-grained source rocks into the coarse-grained reservoir rocks.
In short distance
Expulsion is
upward
except there's
pressure
that
overcome buoyancy
Secondary
Driven by
buoyancy
Initial pathway
dendritic
until path of atleast resistance established.
Follow path of max. rising until barriers are met.
Possibilities of
mixing
Possibilities of
physical, chemical & bacterial alterations
Movement of oil&gas from
carrier bed to trap
Long distance
Porosity
More porous, greater the amount of open space it contains
Stored
liquid&gas
Clay: greatest porosity
Source rock: high porosity
but
reservoir rock: poor porosity
Volume of pore space
Tertiary
Movement of oil&gas
from trap to fresh trap or to seepage
Includes
seepage, leekage, dissipation & alteration of petroleum
as it reaches Earth's surface.