Clarification of the structure and facies zonation of Upper Devonian carbonates sediments of Lyzha-Kyrtael arch and Pechorogorodskaya step

UDK: 551.263
DOI: 10.24887/0028-2448-2017-12-80-82
Key words: Upper Devonian, horizon, formation, reservoir, seal, hydrocarbon accumulation
Authors: S.V. Kochetov, P.A. Shahov (VNIIneft JSC, RF, Moscow)

The article provides the information about special features of structure, lithology, stratigraphy and conditions of formation of Upper Devonian sediments of Lyzha-Kyrtael arch (LKV) and Pechorogorodskaya step (PS) of Pechora-Kolva aulakogen (PKA). Upper Devonian complex within Timan-Pechora province is one of the main complex considering the predicted resources and hydrocarbon potential. Upper Devonian complex has a complicated structure, dramatic facies variation and instability of facies zones through geological time. The paper provides the range of the main cross-section types and shows stratigraphically completed and uncompleted cross-sections of Upper Devonian sediments within LKV and PS. It was observed that completeness of cross-section of Upper Devonian complex depends on paleotectonic elements association (main trough, adjacent trough or tectonic steps). It was considered that the types of cross sections are connected to difficult paleorelief, which covered the area in Frasnian time. The detailed correlation scheme of the area is compiled; the main markers and formations are defined. It was noted that in addition to depression Domanic sediments the shallow shelf sediments of frasnian age were defined within the area. The following facies complexes were determined within LKV and PS: facies of starved basin and paleoelevations in there, facies of carbonate blocks and lagoon facies. Upper Devonian complex development in Timan-Pechora province took place during four deposition stages: Semiluki, Don, Sosnovski and Ust-Pechora-Dzhebol. Optimum conditions for good reservoir properties formation are associated with upper Frasnian terrigenous-carbonates, organogenic-hemogenic and organogenic massif and their flanks, and also related to adjacent trough of PKA. Also good conditions for reservoir formation are associated with separate intervals in Famenian age.

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