Tag: reservoir rocks

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LITHOLOGICAL AND FACIAL STRUCTURE AND PROSPECTS OF THE OIL AND GAS CAPACITY OF THE MIDDLE JURASSIC SEDIMENTS OF THE PREDOBROGEAN DEPRESSION

Home > Archive > No. 3–4 (195–196) 2024 > 24–35

Geology & Geochemistry of Combustible Minerals No. 3–4 (195–196) 2024, 24–35

https://doi.org/10.15407/ggcm2024.195-196.024

Kostyantyn HRIGORCHUK1, Volodymyr HNIDETS2, Oksana KOKHAN, Lina BALANDYUK

Institute of Geology and Geochemistry of Combustible Minerals of National Academy of Sciences of Ukraine, Lviv, Ukraine, e-mail: 1kosagri@ukr.net; 2vgnidets53@gmail.com

Abstract

The paper presents the results of complex lithogenetic studies of the Middle Jurassic deposits of the Predobrogean depression. The nature of the lithological-lithmological space-age variability of the Callovian and Bath-Bajocian deposits was established, lithophysical models were built on this basis, and the peculiarities of the development of reservoir rocks of various types and aquitards were clarified. In the lithological structure of the Middle Jurassic, three types of section are distinguished according to the ratio of rock components. It was established that the lithological structure of the Callovian and Bath-Bajocian deposits is significantly different: clayey, as well as siltstone-sand litmites are characteristic of the Bath-Bajocian, and mixed and terrigenous litmites with a carbonate component are characteristic of the Callovian. The lateral lithological and lithological heterogeneity of the sediments indicates that the studied profiles cross several facies zones. Two clastogenic packs of regional distribution were identified in the section of the Bath-Bajocian in the lower and middle parts of the section, 55–60 m and 50–240 m thick, respectively, separated by a pack of clay formations. The Callovian deposits are characterized by the development of mixed litmites, to a certain extent enriched in carbonate rocks. Three oil and gas promising areas have been localized. First, this is the district of Well Suvorivska-4, where the development of a combined (anticlinal and lithologically limited) trap is predicted in the Callovian deposits. Secondly, the area between Well Chervonoarmiyska-2 and Suvorivska-4, where 10 horizons of both pore and fracture reservoirs are wedged in the Bath-Bajocian deposits. The third is the district of Well Starotroyanivska-1, where there is a anticlinal trap with the development in the Bath-Bajocian deposits of two horizons of pore collectors, which are shielded by rather powerful aquitards.

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Keywords

deposits of the Middle Jurassic, litho-lithmological features, reservoir rocks, Predobrogean depression

Referenses

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Hnidets, V. P., Hryhorchuk, K. H., Kokhan, O. M., Rever, A. O., & Balandiuk, L. V. (2023). Litohenez maikopskykh vidkladiv Prychornomorskoho mehaprohynu. Lviv. http://iggcm.org.ua/wp-content/uploads/2023/12/ЛІТОГЕНЕЗ-МАЙКОПСЬКИХ-ВІДКЛАДІВ.pdf [in Ukrainian]

Hnidets, V. P., Hryhorchuk, K. H., Kurovets, I. M., Kurovets, S. S., & Prykhodko, O. A. (2013). Heolohiia verkhnoi kreidy Prychornomorsko-Krymskoi naftohazonosnoi oblasti Ukrainy (heolohichna paleookeanohrafiia, litohenez, porody-kolektory i rezervuary vuhlevodniv, perspektyvy naftohazonosnosti). Lviv. [in Ukrainian]

Hnidets, V. P., Hryhorchuk, K. H., Pavliuk, M. I., Koshil, L. B., & Yakovenko, M. B. (2021). Litohenetychni peredumovy formuvannia rezervuariv i porid-kolektoriv u serednodevonskykh vidkladakh Skhidnosaratskoho rodovyshcha (Pereddobrudzkyi prohyn). Rozvidka ta rozrobka naftovykh i hazovykh rodovyshch, 3(80), 7–18. https://doi.org/10.31471/1993-9973-2021-3(80)-7-18 [in Ukrainian]

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LITHOLOGICAL AND GEOCHEMICAL CHARACTERISTICS OF THE MIDDLE DEVONIAN STRATA OF THE LVIV DEPRESSION IN THE ASPECT OF THEIR OIL AND GAS BEARING PROSPECTS

Home > Archive > No. 3–4 (191–192) 2023 > 20–30

Geology & Geochemistry of Combustible Minerals No. 3–4 (191–192) 2023, 20–30

https://doi.org/10.15407/ggcm2023.191-192.020

Natalia RADKOVETS, Yuriy KOLTUN

Institute of Geology and Geochemistry of Combustible Minerals of National Academy of Sciences of Ukraine, Lviv, Ukraine, e-mail: radkov_n@ukr.net

Abstract

The Middle Devonian deposits within the Lviv Depression of the Volyn-Podillya plate are largely underexplored and are of great interest for further exploration for hydrocarbons. The presence of two discovered gas fields and the occurrence of granular and fractured reservoir rocks within the entire Lviv Depression point that the deposits of this age range are prospective for further exploration works for hydrocarbons. The authors conducted mineralogical and petrographic studies of these strata in order to study different types of reservoir rocks.

Petrographic studies of terrigenous rocks showed that the reservoir rocks are composed of fine-grained and medium-grained sandstones, as well as fine-grained and coarse-grained siltstones. The matrix in these rocks is contact-porous and contact, composed of dolomitized calcite (4–19 %) and hydromica (3–13 %). Regardless of the type of matrix, the pore space in rocks is formed by intergranular spaces of 0.05 to 0.5 mm size. Siltstone-sandstone deposits represent the granular-type reservoir rocks, the filtration properties of which are formed by the intergranular space, while fractures are of subordinate importance. Terrigenous rocks form gas-bearing horizons in Middle Devonian (Eiffelian and Zhivetian) in the Lokachi field of the Lviv Depression. Carbonate rocks are represented by a wide range of lithological types from slightly dolomitized biodetrital limestones to secondary dolomites. Dolomitization and recrystallization form fracture-like microcaverns with a size of up to 0.5 mm and result in a high porosity of up to 9 %. In carbonate reservoir rocks fracturing is prevailing, while porosity has a subordinate value.

Studies of the molecular composition of natural gases from reservoir rocks of the Middle Devonian of the Lokachi field showed that their predominant component is methane. Its content is 92.7–95.4 vol %. The rest of the methane homologues account for 1.45–2.16 vol %. The total share of non-hydrocarbon gases – nitrogen, carbon dioxide, helium and hydrogen are 3.102–5.082 vol %.

In order to clarify the origin of the Middle Devonian gases of the Lviv Depression, further studies of the carbon, nitrogen, and hydrogen isotopic composition of these gases and the study of the generation properties of the Lower and Middle Devonian rocks of the studied region are necessary.

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Keywords

Lviv Depression, Middle Devonian, reservoir rocks, mineralogical and petrographic composition of rocks, molecular composition of gases

Referenses

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