Petroleum Geology Definition and introduction

 Ø Petroleum Geology:

Petroleum geology is the study of origin, , movement, occurrence, accumulation, and exploration of hydrocarbon fuels.

                                                                                       OR

                          Petroleum geology is the study of Petroleum System in order to explore the hydrocarbons

Ø Petroleum System:

A petroleum system encompasses a pod of active source rock and all genetically related oil and gas accumulations. It includes all the geologic elements and processes that are very necessary if an oil and gas accumulation is to exist.

The essential elements of a petroleum system include the following:

·         Source rock

·         Reservoir rock

·         Seal rock/Trap

The essential processes includes the following:

·         Generation

·         Migration

·         Accumulation

These essential processes and elements must be correctly placed in time and space so that organic matter included in a source rock can be change into a petroleum accumulation.

Basic Vocabulary of petroleum geology:

Petroleum (Rock Oil): naturally occurring complex of Hydrocarbons widely distributed in the sedimentary rocks

      Crude Oil: the liquid member of Petroleum
      Natural gas: the gaseous member of petroleum
      Asphalt, bitumen or Tar: the solid member of petroleum
      Reservoir: the rock containing petroleum

  Trap: feature of rock that restrain petroleum from moving out

  Pool: a single discrete accumulation of oil or gas in a single reservior with a single trap
     Field: several pools may lie vertically, side by side or overlap laterally within a single area, areally continuous.

  Sedimentary basin: a three dimention geological entity containing a number of oil or gas fields.

  Province (may be synonym of basin): several basin sharing clear similarities but separated by barren or non basinal tracts.

  District: a geographic concentration of fields within a province or a basin.

  Prospect: a small area within a basin, province or district which may contain oil and gas but no yet has been proved to do so.

  Play: a larger area within which drilling of prospect has been established success and pointed the way for further drilling.

  Conventional oil and gas: the oil and gas within a well discovered and exploited by drilling boreholes, if other than conventional would be unconventional.

  Well: A hole which yield any fluid.

  Exploratory or wildcat well: a well drilled in search of a new accumulation of oil and gas. 
     Discovery: if exploratory well is successful then it is discovery. 
     Gushers: earlier well spur oil high into air by a strong flow when drilled.

  Completed well: if a discovery well shows promise of being commercial it compeleted as a producting well.

  Dry hole: if a well yeilds no recoverable oil or gas.

  Logging: the processes of recording data of a well.

  Exploration: the search for new sources of petroleum.

  Reserves: the sources discovered by successful exploration becomes reserves, which are portion of total resources that have been shown to accessible and recoverable under current economic and technologic condition.

  Development: the process of recovering the reserves, by drilling wells within a field and operating them successfully.

  Operators: organization and individuals seeking or producing oil or gas.

  Basic Statistics:

Measurement Units

Quantities of oil are expressed in barrels:

1 barrel = 42 US gallons=159 liters app=34.9723158 UK (Imperial gallons)

1 Gallon(gal) = 3.7854118 US liter(L)/4.54609 UK (L)

1 cubic meter = 1,000 L= 6.37 barrels

1 metric ton = 6.8 to 7.6 barrels (dep. on sp. gravity, in UK, USSR and others by weight)

Gas is expressed in millions of cubic feet:

1 MMcf ~ 3.104 m3

Energy-wise, gas can be expressed in oil equivalents:

1 boe ~ 6000 to 6500 cf.