By:

HAMAS-UL-GHANI

ROLL NO. 11

BS APPLIED GEOLOGY 2ND PROF

Structural TrapsTERMS TO KNOW BEFORE UNDERSTANDING

TRAPS

Porous rock

Permeable rock

Source rock

Reservoir rock

Migration path(primary migration and

secondary migration)

Seal rock/Cap rock/Roof rock

Structural Traps Porous rock:

A rock which contains pores in it

Permeable rock:

A rock which contains interconnected pores

Source rock:

The rock which generates Hydrocarbons

Reservoir rock:

Porous and permeable rock unit which holds

Hydrocarbons

Structural Traps Seal rock:

An impermeable rock that acts as a barrier to the passage

of further upward migration of Hydrocarbons, migrating

in the subsurface.

Common seals are:

– Shale

– Evaporites

Seal overlies the reservoir rock to form a trap.

Also known as roof rock and cap rock.

Structural Traps Primary Migration:

The migration/movement of Hydrocarbons from the

source rock to reservoir rock is called primary migration.

Secondary Migration:

The movement of Hydrocarbons within the reservoir rock

is called secondary migration.

Structural Traps

What is a Trap?

Any arrangement of strata that permits the accumulation

of hydrocarbons in commercial quantities is a trap.

Structural Traps A trap is the place where oil and gas are barred from

further movement(Levorsen,1967).

Checks the flow of Hydrocarbons

Structural Traps A structural trap is a geological trap that forms as a result

of changes in structure of the subsurface due to tectonic,

gravitational and compactional processes i.e. Folding,

faulting etc.

Types of Structural Traps Anticlinal traps

Fault related traps

Salt dome traps

Structural TrapsAnticlinal Trap:

If a permeable rock like sandstone or limestone is

located between impermeable rock layers like shale

and the rocks are folded into an anticline, oil and gas

can move upward in the permeable reservoir rocks,

and accumulate in the upper region of the anticline.

Anticlinal Traps

Anticlinal Traps

Structural TrapsFault-Related Traps:

If faulting can shift permeable and impermeable rocks

so that the permeable rocks always have impermeable

rocks above them, then an oil trap can form.

Both normal and reverse faults can form this type

of oil trap

Fault-Related Traps

Fault-Related Traps

Structural TrapsREMEMBER:

A fault plane itself can act as a seal too.

Structural TrapsSalt Dome Traps:

salt that has moved up through the Earth,

punching through and bending rock along the

way.

Oil can come to rest right up against the

impermeable salt, which makes salt an effective

trap rock

Salt dome Traps