Orta – Geç Jura Yaşlı Birimlerin Hidrokarbon Potansiyelinin Değerlendirilmesi (Karadeniz, Türkiye)

Abstract

This study aims to determine the hydrocarbon potential of Middle-Late Jurassic source rocks in the Western and Central Black Sea regions through office, field, and laboratory analyses works. A total of 87 samples collected during fieldwork were subjected to XRD-Whole Rock, XRD-Clay Fraction, Rock-Eval Pyrolysis, Total Carbon-Sulfur, and Organic Petrography analyses in different sets.

XRD-Whole Rock analysis revealed that clay minerals were dominant in the Himmetpaşa Formation shales (%46.2), followed by quartz (%35.1) and mica (%9.7). XRD-Clay Diffraction analysis indicated that kaolinite was dominant (%70.8), followed by illite (%23.1), based on the occurrence rates of clay minerals. Illite crystallinity, sharpness ratio, and chlorite crystallinity measurements yielded results that varied between diagenesis and metagenesis. While the Rock-Eval Pyrolysis analysis of the Himmetpaşa Formation shales yielded quite good results in terms of TOC, most of the samples were classified as Type IV kerogen due to low S2 values. However, one sample with hydrocarbon production potential have been identified in the sample set.

In the Triassic – Liassic Akgöl Formation shales, XRD-Whole Rock analysis showed that clay minerals were dominant (%36.3), followed by quartz (%19.2) and kaolinite minerals (%8.3) based on their occurrence rates. XRD-Clay Diffraction analysis revealed that illite was the most abundant clay mineral (%55.5), followed by kaolinite (%34.6) and chlorite (%5.6). Illite crystallinity, sharpness ratio, and chlorite crystallinity measurements yielded results that varied between diagenesis and metagenesis. Generally, the Rock-Eval Pyrolysis analysis of the Akgöl shales indicated that their current hydrocarbon generation potential were quite poor in terms of both TOC and S2. Although the dominant kerogen type was Type IV, 6 samples have been classified as Type III kerogen. No sample with hydrocarbon production potential was found among the Akgöl Formation samples.

Furthermore, in the Triassic-Liassic Akgöl Formation, attempts were made to test whether the TOC value increases towards the younger parts of the formation, specifically the Toarcian age, to provide a clue for the existence of the T-OAE (Toarcian Oceanic Anoxic Event) in the Black Sea region. Although some results that raised suspicion were obtained from the samples taken for this purpose, this evaluation requires confirmation with new studies.

According to the results of XRD – Whole Rock analysis in the Triassic Çakrazboz Formation, the dominant clay minerals were 44.2% and calcite minerals were 28.6%. XRD - Clay Diffraction analysis revealed that the dominant clay minerals were Illite (50.2%), Vermiculite (21.5%), and Kaolinite (11.97%) respectively. Thermal maturation measurements conducted from the XRD - Clay diffractograms showed that three samples were in the diagenetic zone, and one sample was near the diagenetic zone boundary but still within the anchizone. The result of the Rock – Eval Pyrolysis analyzes identified a sample with hydrocarbon generation potential, classified as a “very good” source rock, containing Type II kerogen and is in the oil window.

In addition to the above formations, although not within the scope of the thesis, the samples from the Çağlayan and Cankurtaran Formations taken in order to ensure the integrity of the field work were also analyzed and their evaluations were given in the thesis.