22. Genetic Classification of Petroleum Systems

22.

Genetic Classification

of Petroleum Systems

by: Awang Harun Satyana

INDONESIAN PETROLEUM ASSOCIATION (IPA)

REGULAR COURSE, SOLO – CENTRAL JAVA, 4-8 JUNE 2012

1. volumetrically adequate petroleum generation, occurring during or

after the time of trap formation;

2. favorable migration-drainage geometry, leading to the focused

movement of hydrocarbons into traps rather than to dispersion and

loss of hydrocarbons in either subsurface migration “waste zone”

or up to the surface;

3. the existence of volumetrically adequate traps, capable of retaining

their petroleum charge from the earliest time of trap filling to the

present day.

Three important geologic factors control the accumulation

of petroleum in the subsurface and, thus are essential to

the existence of viable “petroleum systems:

Demaison and Huizinga (1991)

Two Subsystems of Petroleum System

1. A generative subsystem provides a certain supply of petroleum during a

given time span. Generative subsystems are essentially controlled by

chemical processes, consisting of biochemical transformation of dead

organisms into kerogen during the source depositional stage and thermo-

chemical kinetics, which control the transformation of kerogen into

petroleum.

2. A migration-entrapment subsystem gathers petroleum from the mature

source rocks and distributes it in a manner that may lead to either

concentration of petroleum into economic accumulations or loss of

petroleum due to dispersion and destruction. Migration-entrapment

subsystems are predominantly controlled by physical processes, including

the buoyant rise of petroleum in water, fluid flow and capillary pressures in

porous media, and pressure-temperature-composition relationships

affecting phase behavior before and during petroleum entrapment.

Demaison and Huizinga (1991)

Demaison and Huizinga (1991)

Purpose of Genetic Classification

• Describe and predict the relative charging

potential of petroleum systems and, thus

segments of petroleum basins,

• Describe geographic location of zones of

petroleum occurrence or plays in basins.

Demaison and Huizinga (1991)

Genetic Classification of Petroleum System

1. Combining qualifiers from each of the following three

categories: (1) charge factor (supercharged, normally

charged, undercharged), (2) migration drainage style

(vertically drained, laterally drained), and (3)

entrapment style (high impedance, low impedance).

2. Application of these working concepts should help to

significantly reduce geologic risk, particularly in new

ventures-type exploration.

Demaison and Huizinga (1991)

Genetic Classification of Petroleum System

1. The charge factor is estimated on the basis of the richness and

volumetrics of mature source rocks. The source potential index

(SPI), which combines source rock richness and thickness into a

single parameter is introduced.

2. The migration drainage style is determined from the structural and

stratigraphic framework of a basin. Recognition of the dominant

migration style helps to predict the location of zones of petroleum

occurrence in relation to the hydrocarbon kitchens.

3. The entrapment style, which is also dependent on the structural

framework and the presence and effectiveness of seals, describes

the degree of resistance (impedance) working against dispersion

of the petroleum charge.

Demaison and Huizinga (1991)

Demaison and Huizinga (1991)

Demaison and Huizinga (1991)

Demaison and Huizinga (1991)

Migration Drainage Styles

1. Short-range lateral migration along permeable carrier beds and vertical

migration through fault and fracture zones are the most commonly observed

mechanisms of petroleum charging into traps.

2. The petroleum accumulations in most basins are commonly found over or

immediately adjacent to hydrocarbon kitchen. In fact, most commercial

petroleum accumulations result from short lateral-migration distances (less

than 30 km).

3. Low-angle lateral migration is physically less efficient that vertical migration.

The buoyant force of an oil filament of fixed length and volume is several times

higher for purely vertical displacement than for lateral upward transport along

a gently dipping carrier bed. Consequently, lateral migration is more

demanding on the amount of oil needed to create an adequate buoyant force

capable of breaking through capillary pressure barriers in the carrier unit

(Illing, 1939).

4. Fault and fracture systems that are persistently reactivated by tectonic

movements may serve as highly efficient avenues for vertical migration of

petroleum.

Demaison and Huizinga (1991)

Migration Drainage Styles

Demaison and Huizinga (1991)

Demaison and Huizinga (1991)

Demaison and Huizinga (1991)

Entrapment Styles

1. The degree of structural deformation and seal integrity are the two

key factors used to qualify entrapment styles. Together, these

factors control the degree of impedance working against the

natural tendency for petroleum to become randomly dispersed and

lost in sedimentary basins.

2. High-impedance systems are characterized by laterally continuous

seals coupled with a moderate to high degree of structural

deformation.

3. Low-impedance systems are characterized by either a high degree

of regional seal continuity and low degree of structural

deformation, or low degree of regional seal effectiveness, coupled

with a high or low degree of structural deformation.

Demaison and Huizinga (1991)

Demaison and Huizinga (1991)

Demaison and Huizinga (1991)

Demaison and Huizinga (1991)

Demaison and Huizinga (1991)

Demaison and Huizinga (1991)

Demaison and Huizinga (1991)

Demaison and Huizinga (1991)

Demaison and Huizinga (1991)

Demaison and Huizinga (1991)