The use of compiled thermal methods in the characteristics of source rocks on the example of menilite beds

Abstract

The aim of the research was to compare the results of the thermal decomposition of organic matter using different research methods. Experiments were carried out to assess interpretation methods in the characterization of the generation potential of source rocks. The research was conducted for samples of Menilite shales, recognized on the basis of long-term geochemical studies as good quality source rocks. The samples represented the Menilite Beds of the Silesian Unit, taken from the outcrops in the Carpathians. Research using known methods: Rock-Eval pyrolysis (RE), thermogravimetric and calorimetric methods (TG/DSC), and pyrolysis methods combined with gas chromatography analysis (PY-GC), were performed on the same samples- both on rock samples, as well as isolated kerogen. Such integrated studies have so far not been conducted on any rock material. The applied research methods showed a significant comparability of the results obtained. A number of correlations were found between the parameters from individual methods, including: the amount of hydrocarbons separated during PY-GC in the temperature range of 300–650°C, and the parameter S2 from RE, and mass loss in the TG analysis in the same temperature range; S2 values of rock samples and kerogen with weight loss as a result of pyrolysis from TG/DSC analysis at temperatures in the range of 300–650°C; temperature values of the maximum peak S2 (Tpk2) of rock samples with the maximum mass loss temperature during TG analysis; residual carbon content (RC) from RE analysis of rock and kerogen samples with a mass loss as a result of burning residual organic matter from TG/DSC analysis at temperatures in the range of 650–1050°C. The mass loss determined during thermogravimetric analysis, combined with the percentage share of individual hydrocarbon fractions, in which the C9+ fraction is significant, confirms the high petroleum potential of the organic substance contained in the Menilite Beds. Comparative studies of pyrolytic methods: Rock Eval, TG/DSC and PY-GC have proved the compatibility of the results obtained with all methods. Each of the methods also makes it possible to obtain mutually complementary information relating to the TOC, the degree of thermal maturity and type of generated hydrocarbons and other non-hydrocarbon compounds. The conducted tests and performed correlations showed the usefulness of a set of thermal methods to obtain complete information on source rocks.