4-Petroleum-Systems-An-Overview-2012.pdf

AN INTRODUCTION TO PETROLEUM SYSTEMS

THE FANCIFUL RESERVOIR

Halliburton (2001)

WATER

Halliburton (2001)

Carbonate produc3on high because of the Middle East & Mexico.

PETROLEUM PRODUCTION BY ROCK TYPE

ORGANIC MATTER & HYDROCARBON GENERATION

MATURATION OF ORGANIC MATTER (CONVERSION OF ORGANIC MATTER (OM) TO HYDROCARBON (HC)

KEROGEN TYPES

oil-prone

gas-prone

Temperature gradients

HYDROCARBON MIGRATION & ACCUMULATION

When poten:al source and reservoir rocks are buried, they contain water in their pore space. The oil or gas, therefore, has to replace this water in the migra:on process when it reaches the reservoir rock. (TUDelN)

Subsurface rocks contain water; connate water if original trapped water (fossil water), or meteoric water fresh water that originates at the Earths surface.

Oil and gas, as it is generated, has to displace water

FORMATION WATER

FORMATION WATER

Most forma:on water is saline.

Sea water

MIGRATION

Primary migra:on

Secondary migra:on

Oil is generated in compacted shales, and presumably expulsed from these shales as they con:nue to compact. Being buoyant, it migrates upward.

Mature hydrocarbons rst have to migrate out of the source rock. This is in general a ne-grained rock that has a low permeability, During burial, this rock gets compacted and its inters::al uid become overpressured with respect to surrounding rocks that have higher permeabili:es and from which uids can migrate with greater ease upwards. Therefore, a uid pressure gradient develops between the source rock and the surrounding, more permeable rocks. This causes the uids - the water and the hydrocarbons - to migrate along the pressure gradient, usually upwards, although a downward migra:on is possible. This process is called primary migra:on, and it generally takes place across the stra:ca:on. Why?

PRIMARY MIGRATION

PRIMARY MIGRATION

PRIMARY MIGRATION

SECONDARY MIGRATION

SECONDARY MIGRATION

Lower pressure in the sandstone; hence some primary migra3on can be lateral or even downward from an organic shale into a porous-permeable sandstone layer.

SECONDARY MIGRATION

Unconformity trap; overlying impermeable shale.

SECONDARY MIGRATION

A facies change, say from oshore shales to nearshore sands.

SECONDARY MIGRATION

Abundant natural porosity & permeability of a reef = natural sponge for petroleum if you have a source rock that can feed the reef.

SEALS

SECONDARY MIGRATION

THE END (for now)