A pyrolysis system was developed to identify the possible production type (oil, condensate, and gas) and the presence of contamination (by migrated oil or drilling additives) in rock samples. This is accomplished by incorporating gas chromatography (GC) in the pyrolysis system so that a direct analysis can be made of the hydrocarbons in the pyrolysis products from sediments samples. This analytical capability of making a positive identification of pyrolysis products is one of the important advantages of this system. Because of this additional feature, this pyrolysis system can overcome problems related to the interpretation of indirect production type indicators such as the oxygen and hydrogen indices used by the commercially available ROCK-EVAL system.

The productive type is recognized either qualitatively by GC fingerprint traces or quantitatively by hydrocarbon composition (C₁-C₄, C₅-C₁₄, and C₁₅₊) from the kerogen (Peak II) pyrolysate. Oil-prone sediments are recognized by GC traces with a full spectrum of C₁ to C₂₈ hydrocarbons, or by high amounts of C₁₅₊ hydrocarbons. In contrast, gas-prone sediments are characterized by the predominance of light hydrocarbons from C₁ to C₇ in the GC trace, or by low amounts of C₅-C₁₄ and C₁₅₊ hydrocarbons. Condensate or mixed type production is intermediate in character between the two.

Migrated oil or liquid contaminants are detected by a stepwise heating of the rock samples and GC analysis or Peak I (solvent extractables) and Peak II (kerogen decomposition) products.

The application of this pyrolysis system over the past four years as a rapid method for evaluation of organic richness, maturation, and production type using well or outcrop samples along with the limitations of the techniques will also be discussed.

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