Mission and Tasks 

Like the major oil companies, ONHYM has a Department of Organic Geochemistry with the following mission:

  • Maintain a center of excellence in organic geochemistry and its application to petroleum exploration, and the introduction of new methods of analysis.
  • Ensure the delivery of analysis and geochemical studies for ONHYM and external customers.
  • Develop geochemical and thermal models and their application to oil exploration.

Two main methods are used for analysis and studies:

  • Rock-Eval Pyrolysis
  • Optical microscopy


The Department of Organic Geochemistry is composed of:

  • A geochemical analysis laboratory
  • A unit of studies and geochemical/thermal modeling of sedimentary basins.

Geochemical analysis is provided by the organic geochemistry laboratory whose mission is the study of the ability of rocks and sedimentary basins to generate hydrocarbons. Two main methods are used for this purpose:

  • Rock-Eval Pyrolysis,
  • Optical microscopy

Rock-Eval Pyrolysis: 

This method involves pyrolysis of a sample rock to evaluate its richness in organic matter, its oil potential and the quality of its kerogen.

1 Determined parameters: 

  • Total organic carbon (TOC): assessing the richness of organic matter in rock and its ability to generate hydrocarbons.
  • The potential in free hydrocarbons (S1): the amount of free hydrocarbons in the rock,
  • The potential in residual hydrocarbon (S2): the amount of hydrocarbons generated by pyrolysis, which is assumed to have been generated if the rock had reached a sufficient stage of maturity.
  • Tmax in C: determines the degree of maturation of the rock.  It is the pyrolysis temperature recorded at the maximum peak of generation S2.
  • Carbon mineral: evaluates the degree of carbonate.
  • The residual carbon: allows the determination of the amount of inert organic matter.
  • The production index (IP), hydrogen index (IH) and the index of oxygen is calculated from the TOC, S1, S2 and S3.

2 Examples of presentation of results Geochemical Log

S6 4

The presentation of the results of samples from wells in the log, allows the rapid identification of bedrock levels.

Optical microscopy :

This is the study of organic matter in sedimentary rocks, under a microscope to determine:

  • Type of kerogen: lacustrine, marine or continental,
  • Degree of maturation.

Determined parameters:

  • The type of organic matter: lacustrine, marine or continental
  • The IAT, the Thermal Alteration Index: To assess the degree of maturation;
  • The reflectance of vitrinite or PRV Ro (%): To assess the degree of maturation

4 Examples of presentation of results :

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Geochemical and thermal modeling

The modeling of burial and thermal maturation is performed by BasinMod-1D ® software

Study results:

  • Draw the landfill diagram
  • Calculate the heat flow
  • Calculate the geothermal gradient
  • Calculate the gradient of maturation
  • Calculate the generation timing
  • Draw the diagram of the petroleum system