This work considers the Early Carboniferous coal-bearing deposits of the karst-erosional paleo-downcuttings of the Volga–Ural oil and gas basin. The depth of their occurrence is 900–1400 m or more. The role of organic matter in coal as a fluid-generating component in the transformations of the geological environment is highlighted. It was noted that specific reservoirs (methane–coal and pyrometamorphic) may be formed in coal-bearing rocks. This work covers the concept of catagenetic fracturing, which is also caused by fluid-generated losses of organic matter and an unequal decrease in the thickness of coal-bearing layers. Attention is also drawn to the other factors of changes in the filtration properties and fracture fluid conductivity (aggressiveness of some products of organic matter transformation, deposition of epigenetic minerals, and variability of the ash distribution). It is concluded that the discrete occurrence of paleo-downcuttings affects circulation of stratal waters in the Visean deposits of the basin; the geochemical and geomechanical features of bulks of coal increase the geofluidodynamic heterogeneity of these deposits.

中文翻译：

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伏尔加-乌拉尔油气盆地岩溶侵蚀下切的煤田作为地球流体动力非均质性的一个因素

这项工作考虑了伏尔加-乌拉尔油气盆地岩溶侵蚀古下切面的早石炭世含煤矿床。它们的发生深度为 900-1400 m 或更高。突出了煤中有机质作为流体生成成分在地质环境变化中的作用。注意到在含煤岩石中可能形成特定的储层（甲烷-煤和火变质储层）。这项工作涵盖了后生压裂的概念，这也是由流体产生的有机物损失和含煤层厚度不均等减少引起的。还应注意过滤特性和压裂液传导率变化的其他因素（某些有机质转化产物的侵蚀性、后生矿物的沉积、和灰分分布的可变性）。结论是古下切的离散发生影响了盆地Visean沉积物中地层水的环流；大块煤的地球化学和地球力学特征增加了这些矿床的地球流体动力学非均质性。