--> --> Cenomanian-Turonian Black Shales of the Tarkhankut Peninsula as Emerging Shale Gas Play: A Small-scale Replica of the Eagle Ford Formation?

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Cenomanian-Turonian Black Shales of the Tarkhankut Peninsula as Emerging Shale Gas Play: A Small-scale Replica of the Eagle Ford Formation?

Abstract

To known shale gas plays in Ukraine which are under active evaluation now in this country it would worth to add another prospective area in the Southern region located within the petroleum-prone basin characterizing by this date with minor discoveries of conventional hydrocarbons. The geological setting of the suite reveals direct analogies to the Eagle Ford–Woodbine petroleum system and corresponds to the OAE-2 anoxic global event. This potential play for unconventional hydrocarbons occupies the western part of the Crimea Peninsula and stratigraphically belongs to upper part of the Belogorsk suite, topmost part of Cenomanian stage. Likewise the Southern Texas, in the Mountainous Crimea it is observed a gentle unconformities related to sub-phases of the Subhercynian tectonism. The prospective area is totaled to ca. 2100 sq.km embracing onshore part of the Karkinit-North Crimean graben within 20-km wide belt stretching WSW-ENE from Olenevka towards Dzhankoy town. Net thickness of the marly shale interval (1–3% TOC in average, 3.84% max) is vary from 15 to 30 m within the transition series of 100 m thick composed mainly by carbonate rocks (marly shales, marls, and limestones). Higher thicknesses of this carbonate black shales with very characteristic gamma-ray log response are revealed to the northwest under the waters of the Karkinit Bay and Gulf of Odessa. A lateral analog of the rocks is outcropped to the south in the Crimean Mountains where TOC in the condensed Aksu-Dere section (0.7 m) of the black shales with high REE content reaches as much as 7.2%. Rather intense intra-formation fracturing is characteristic of that interval demonstrating low permeability and matrix porosity above 3%. The depth to target interval within the potential play is 1700–3000 m. The rocks are occurred within MK1-MK2 thermal maturity zone of main hydrocarbon generation (oil window). There are several small and sub-commercial gas and oil fields discovered in the Cenomanian-Turonian and Senonian carbonate formations (Austin Chalk analog) in the region, plus frequent oil and gas manifestations while drilling through the shales are reported. Shale gas resources of the play are estimated at 1 Tcm at least. The territory of play is a steppe terrain characterized by rather dry temperate continental climate, moderate agriculture and relatively low population density. Though the area lacks water resources there is a possibility to use marine water of the Karkinit Bay for fracking.