Petroleum Geochemistry Division - Source Rock Assessment...

Evaluation of potential source rocks is carried out on a series of sediment samples from one well or a group of wells, starting with screening analyses typically for a large number of samples. GEOTECH’s routine analyses for the assessment of source rocks include the following:

Total Organic Carbon Determination

Total organic carbon (TOC) determination is used as a screening tool to identify intervals of organic richness. Those samples with satisfactory source rock richness are then investigated further. In general, samples with TOC values greater than 0.5% for shales and 0.3% for carbonates are considered suitable for Rock-Eval pyrolysis.

Rock Eval Pyrolysis

Rock Eval pyrolysis is a fast and cost effective screening tool for the assessment of source rock potential. Rock-Eval data can be used in a number of ways:

      To investigate the source rock character, in particular the hydrocarbon            generating potential and the oil-vs-gas potential
      To determine the level of thermal maturity of potential source rocks
      To determine migrated hydrocarbons and insitu generated hydrocarbons
           present in a sediment
      To identify possible contamination of samples with drilling additives

Pyrolysis GC

Pyrolysis GC is performed on solvent extracted source rocks or isolated kerogens and determines the type of hydrocarbons expelled from the source rock (gas vs oil). The technique allows for a more detailed assessment of the character of potential source rocks than Rock Eval pyrolysis and samples for PyGC are normally selected from Rock-Eval screening data.

Vitrinite Reflectance and Maceral Description

Vitrinite reflectance measurements determine the maturation levels of organic matter and define zones of oil and gas generation within a particular interval. Vitrinite reflectance, together with maceral description, provides information about the type of organic matter present and can be used to help differentiate between in-situ generated hydrocarbons and migrated oil and to identify the presence of contamination. Vitrinite reflectance and maceral description are generally used in conjunction with TOC / Rock-Eval pyrolysis as effective screening tools for the identification of organic rich source intervals.