Petroleum Geochemistry

Online Course

Case Studies

unit1 Development of Petroleum Geochemistry
unit2  Origin and Migration of Petroleum
unit3 Habitat of Petroleum -- Sources and Reservoirs
unit4 Applications 

Subject Matter Expert:
Xxxx xx xxx. Ph.D.

Course Design:
Susan Smith Nash, Ph.D.

EDGe Education
The Universiy of Oklahoma

Green River Formation

Unit 2: Origin and Migration of Petroleum


  • How Oil Forms:  Natural Hydrocarbons
  • How Oil Forms: Generated Hydrocarbons
  • Modeling Petroleum Generation
  • The Origin of Natural Gas
  • Migration and Accumulation
  • Abnormal Pressures

Required Reading
Hunt, Petroleum Geochemistry
  • Chapters 4 -9

Key Concepts
  • Organic origins of hydrocarbons
  • Modeling Petroleum Generation -- time-temperature index (TTI) graphs
  • Types of oil-generating Kerogens
  • Origin of natural gas
  • Arrhenius equation
  • SOURCE ROCK - A unit of rock that has generated oil or gas in sufficient quantities to form commercial accumulations. The term "commercial" is variable and the terms "migratable" or "significant" are often substituted. Source rock is synonymous with "effective source rock".
  • LIMITED SOURCE ROCK - A unit of rock that contains all the prerequisites of a source rock except volume. Cannot be defined by geochemical data alone but requires geological information as to the thickness and aerial extent.
  • POTENTIAL SOURCE ROCK - A unit of rock that has the capacity to generate oil or gas in commercial quantities but has not yet done so because of insufficient catagenesis (thermal maturation). The distinction between source rocks and potential (immature) source rocks are essential in petroleum system studies and when correlating oils to their source rocks.
  • ACTIVE SOURCE ROCK - A source rock that is in the process of generating oil or gas. Active source rocks have oil window maturities and are at or close to their maximum burial depth. The distribution of active source rocks is essential in petroleum system studies. Active source rocks cannot occur at the surface.
  • INACTIVE SOURCE ROCK - A source rock that was once active but has temporarily stopped generating prior to becoming spent. Inactive source rocks are usually associated with areas of overburden removal and will generate hydrocarbons again if reburied. Oil-rock correlations are best done between oils and active or inactive source rocks.
  • SPENT SOURCE ROCKS - A source rock that has completed the oil and gas generation process. A spent oil source rock can still be an active or inactive source for gas. We feel that proper and consistent use of these source rock terms will help mitigate the confusion which exists in the literature and in interpreting and using source rock data.
  • BIOMARKERS most commonly used in crude oil-source rock correlations and in maturation evaluarions are steranes and terpanes.
  • Names of individual terpanes and steranes are based on four variations in their origin and chemistry: 1) compound class; 2) number of carbon atoms; 3) 3-dimensional; 4) 3D ring system configuration.
  • Hydrogen content of kerogen determines the quantity of oil generated in a petroleum system.
  • Migration
  • Porosity
  • Seal
  • Trap
  • Unconformities, Sheet, and Channel Sandstones
  • Distribution of Petroleum by Basin Type
  • Abnormal pressures
  • Geothermal gradient

  • Diagenesis
  • Catagenesis
  • Metagenesis
  • Biomarkers -- what do they include?
  • Basic building blocks of biomarkers
  • Odd-carbon chain lenths
  • CPI -- Carbon Preference Index--what does it indicate?
  • Sediments occurring in petroleum generation systems
  • Anoxic environments
  • What hydrous pyrolysis experiments indicate
  • Immature, mature, postmature stratigraphic intervals
  • Gas window
  • Oil window
  • Bacterial source of gas
  • Coal source of gas
  • Oil source of gas
  • Condensates
  • Nonhydrocarbon gases
  • Carbon dioxide sources
  • Hydrogen sulfide sources
  • Nitrogen sources
  • Pattern of gas compositions
  • Best petroleum reservoir rocks
  • Vertical migration pathways
  • Three critical factors for a petroleum trap
  • Best petroleum seals
  • Factors limiting porosity:  diagenetic alteration, cementation, dissolution
  • Processes which enhance porosity
  • Processes which reduce porosity
  • Permeability
  • Processes generating deep overpressures
  • Gas chimneys
  • Overpressures due to compaction disequilibrium

Practice Multiple-Choice Test Questions