Rock-Eval pyrolysis
The Rock Eval pyrolysis is a method for characterization of kerogen , ie potential oil - source rock . The result gives clues to the question of whether an oil well is economically interesting.
execution
A sample of approx. 100 mg is placed in a pyrolysis oven under inert gas , e.g. B. heated helium . The amount of substances emerging from the sample is measured with a gas chromatograph .
Step by step
- The oven is kept constant at 300 ° C for 3 minutes. In this phase most of the hydrocarbons , the molecules of which have fewer than 40 carbon atoms, evaporate . The amount of leaked substances in this phase is the S1 value.
- The temperature is increased to 550 ° C at a heating rate of 25 K / min. Crack reactions take place in the temperature range passed through. The cracked products evaporate. The amount of leaked substances in this phase is the S2 value. The temperature at which the amount of evaporated substances is highest is called Tmax.
- The furnace is cooled down again. When driving through the temperature range 390 ° C - 300 ° C carbon dioxide is released. The amount of carbon dioxide is the S3 value.
The S values are given in milligrams of leaked gas per gram of sample.
evaluation
Further key figures are derived from the measurement results of a sample. The TOC value is also used for their calculation .
- Hydrogen Index HI (Hydrogen Index) - reference point for the origin of the organic material. Aquatic plants consist of fat and protein-rich material with a higher hydrogen / oxygen ratio than land plants that tend to contain carbohydrates.
- Oxygen Index OI (Engl. Oxygen Index)
- Production index PI
literature
- J. Espitalie, M. Madec, B. Tissot, J. Menning, P. Leplat: Source rock characterization methods for petroleum exploration. Proceedings of the Offshore Technology Conference 1977, Volume III. Pp. 439-44.
swell
- ^ Ocean Drilling Program, Texas A&M University , viewed June 8, 2010