An integrated approach combining fluorescence spectrometry, pyrolysis geochemistry, and dispersed organic matter (DOM) maceral analysis has been used to determine the thermal maturity of Oligocene source rocks in two neighboring offshore wells within the complex deep-sea system of the Northwestern Black Sea. The samples contain predominantly immature Type II kerogen, including a mixture of marine liptinite (alginite, liptodetrinite), degraded liptinite, primary vitrinite, and reworked vitrinitic macerals. The occurrence of several vitrinite reflectance (VR) populations in the samples is attributed to a high influx of reworked vitrinite transported to the marine basin from multiple terrestrial sources with diverse degrees of degradation. The presence of multiple VR populations complicates the application of VR for determining the thermal maturity of the organic matter. Further, the VRo measurements on the primary vitrinite population show only a subtle increasing trend with depth. A significantly improved thermal maturity resolution was obtained using the red to green quotient (R/G). R/G was measured on the autochthonous unicellular -type alginite under UV-excitation. In contrast to VR the results show a significant correlation between increasing R/G values with increasing depth. This indicates that the R/G quotient is a better maturity proxy for the studied low maturity marine system with a large influx of sediments. The beginning of the downward declining trend in the temporal variation of liptinite is regarded as the onset of catagenesis. This occurs at a burial depth of 2.5 km and a R/G value of 0.50, corresponding to a VR equivalent (VR) of 0.44%. At a burial depth of 3.2 km and a R/G value of 0.57 (VR = 0.57%), the onset of the oil window is marked by an increase in the amount of solid bitumen (initial oil solid bitumen). The observed alterations in maceral composition with burial depth align with the thermal maturity of the wells. However, the data suggest that the thermal evolution of the organic matter is out of sync with the surrounding formation temperature, possibly due to rapid burial induced by a high sedimentation rate.

中文翻译：

---

陆源沉积系统热成熟度评估的复杂案例：黑海盆地西北部

结合荧光光谱法、热解地球化学和分散有机质（DOM）显微组分分析的综合方法已被用来确定黑海西北部复杂深海系统内两个相邻海上井中渐新世烃源岩的热成熟度。样品主要含有未成熟的 II 型干酪根，包括海洋脂质岩（海藻质、脂质质质）、降解脂质质、原生镜质质和再加工镜质质显微组分的混合物。样品中出现多种镜质体反射率 (VR) 群体的原因是，从具有不同程度降解的多个陆地来源输送到海洋盆地的大量再加工镜质体大量涌入。多个 VR 群体的存在使 VR 确定有机物热成熟度的应用变得复杂。此外，对原生镜质体群体的 VRo 测量仅显示出随深度的微妙增加趋势。使用红绿商 (R/G) 获得了显着提高的热成熟度分辨率。在紫外线激发下测量原生单细胞型藻岩的 R/G。与 VR 相比，结果显示 R/G 值随深度增加而增加之间存在显着相关性。这表明 R/G 商是所研究的具有大量沉积物的低成熟度海洋系统的更好的成熟度代理。 liptinite时间变化的下降趋势的开始被认为是退变的开始。这种情况发生在埋深为 2.5 km、R/G 值为 0.50 的情况下，对应 VR 当量 (VR) 为 0.44%。在埋藏深度为 3.2 km、R/G 值为 0.57（VR = 0.57%）时，石油窗口的开始以固体沥青（初始石油固体沥青）量的增加为标志。观察到的显微组分随埋藏深度的变化与油井的热成熟度一致。然而，数据表明，有机质的热演化与周围地层温度不同步，可能是由于高沉积速率引起的快速埋藏所致。