Petroleum System

Definition

The processes

The elements

From my understanding, the petroleum system is the geologic components and processes that need to produce and keep the hydrocarbon (generation and accumulation) in the aquifer of source rock from migration.

  1. Source rock: A deposit rich in organic matter of the remains phytoplankton that typically a fine-grained marine that buried to a depth by a suitable temperature and pressure
  1. Migration pathway: A porous and permeable conduit from source to a reservoir that commonly a layer of sand or sandstone, fault and fracture systems
  1. Reservoir rock: A porous and permeable material that hydrocarbon residue in the layer of sandstone or limestone which it could be a fractured stratum of impermeable rock
  1. Trap: A concave-downwards geometric arrangement of a seal or impermeable lateral equivalents of the reservoir rock that commonly looks like an anticline or stratigraphic pinch-out
  1. Seal rocks: Look like impermeable ductile stratum, commonly shale or evaporites, precluding further upward migration
  1. Trap formation
  1. Hydrocarbon generation
  1. Hydrocarbon migration
  1. Hydrocarbon accumulation
  1. Preservation

Source rock for hydrocarbons to be generated. A porous and permeable reservoir rock is needed to contain the hydrocarbon and allow them to accumulate

Reservoir must surrounded by impermeable cap which act as a barrier

The system must be sealed to avoid leak

The timing must be favourable and important that trap form before hydrocarbon migrate

Generation-) Migration-) Entrapment-) Retention-) Recovery

Petroleum Generation is the cooking process

The cooking process called is maturation with heating over time

Rock types (lithologies)

  • Those that may produce hcs when buried and heated (usually occur in fine grained rock)
  • Those that may can contain recoverable hydrocarbon resources (usually occur in porous coarse grained rock)
  • Those that prevent hcs passing through them, trapping them usually impermeable fine grained rock

Sedimentary basin are large subsiding depression filled with thick sequence of sedimentary rock.

Mostly detected by geophysics

They are only places where there may have been sufficient burial for petroleum generation

Most oceans have too thin sediments

Thickest accumulation of sediments tend to occur along continental margins

Types of sediments

  • Siliciclastics ( sand & mud or Sandstones & shales)

Those that produce hydrocarbons when buried and heated, contain recoverable hcs resources and prevent hcs from passing through them by traping them

Source rock

A petroleum source rock may be defined as a fine-grained sediment that in its natural setting has generated and released enough hydrocarbon

Three sedimentary rock types mostly encountered in oil fields: (1. Shales) (2. Sandstones) (3. Carbonates)

Source rock properties: Total Organic Content (TOC) and Hydrogen Index (HI)