FEATURES OF THE LITHOLOGICAL STRUCTURE AND DEVELOPMENT OF RESERVOIR ROCKS AND HYDROCARBON RESERVOIRS IN THE MIDDLE DEVONIAN SEDIMENTS OF THE SOUTHERN PART OF THE TUZLIV DEPRESSION (DOBRUDJA FOREDEEP)

• Дата: 2024
• Автори: Гнідець, В.П., Григорчук, К.Г., Павлюк, М.І., Кошіль, Л.Б., Яковенко, М.Б.
• Формат: Стаття
• Мова: Ukrainian
• Опубліковано: Institute of Geological Sciences, NAS of Ukraine 2024
• Теми: lithological features; cyclites; reservoir rocks; Middle Devonian sediments; Dobrudja Foredeep
• Онлайн доступ: http://geojournal.igs-nas.org.ua/article/view/300565
• Назва журналу: Geological journal

The aim of the work was to clarify the features of the lithological structure of the Middle Devonian sediments of the Zhovtoyarska-Tuzlivska and Biloliska-Zarichnenska prospective areas of the Dobrudja Foredeep and to determine its influence on the formation of reservoir rocks, traps and hydrocarbon reservoirs. The research was based on the results of geophysical research of wells (radioactive methods) in combination with fragmentary geological (lithological) data. As a result, 9 lithocycles of regressive nature were identified in the section for the first time (e-1 – e-5; g-1 – g-4). Each lithocycle is characterized by a two-membered structure and represents a separate productive horizon (PH). The lower parts of the latter are composed of porous and fractured reservoir rocks (limestones, dolomites, siltstones, sandstones), and the upper parts are composed of fluid-resistant packs (marls, anhydrites). It has been shown that cyclites are grouped into larger units (mesocyclites) of re- or progressive nature, which in different wells (in separate intervals) exhibit a certain similarity or difference in structure. Such spatial and age variability is caused, on the one hand, by the placement of wells in different facies zones of the sulfate-carbonate shelf, and on the other, by the processes of interaction of synsedimentary tectonic movements and paleoceanographic (sea level changes, etc.) factors. The consequence of this is the lateral lithological heterogeneity, which in the petrogeological aspect is manifested in the morphological features of the reservoirs and the character of the development of various types of reservoirs and ultimately determines, taking into account secondary rock changes, the prospects of specific productive horizons. Thus, for the Zhovtoyarska-Tuzlivska area, the vaulted trap is localized near borehole Zhovtoyarska-1 (e-1, e-2 productive horizons), according to other horizons it is fixed near borehole Zhovtoyarska-2. The development of lithological traps is predicted in e-1, e-3 and e-4 productive horizons, which is associated with the wedging of pore reservoirs in the direction from borehole Tuzlivska-2 to borehole Zhovtoyarska -2 and -1. For most productive horizons, the quality of reservoir rocks is expected to deteriorate in the same direction, which suggests the possibility of catagenetic screening of fluids. For the Biloliska-Zarichnenska area, along all productive horizons, trap vaults are localized near borehole Zarichnenska-1 or further south. The most capacious are the traps of horizons e-1, e-4 and e-5, composed mainly of pore-type collectors, the quality of which is low due to anhydritization. The best reservoir rocks are predicted in the Givetian sediments (g-2 – g-4 productive horizons) of borehole Zarichnenska -1.