The Kos'yu-Rogov downwarp is within the Timan-Pechora oil-gas province of the northeast of European Russia. The Kochmes, Padimey, Intin, Kozhim, and Lembin fields had been discovered here as of 1985.
Two stages of deposition are recognized in the sedimentary cover of the study area: pre-orogenic (peri-cratonal subsidence) and orogenic (foredeep). The pre-orogenic consists of carbonates and shales of the Middle Ordovician-Lower Silurian and Lower Devonian and clayey carbonates of the Upper Devonian, Carboniferous, and Lower Permian. The orogenic sediments are clay-sand deposits shed off the rising Urals.
The entire section was deposited under conditions favorable for the generation and accumulation of oil and gas. Domanik types of rocks containing large amounts of sapropelic organic matter are present in several areas in the Upper Silurian, Upper Devonian, and Lower Carboniferous Tournaisian. These and other sediments are rated as having good source- rock potential.
Geothermal conditions were generally favorable in the Kos'yu-Rogov downwarp. Even the Upper Permian sediments reached the middle stage of catagenesis and can have generated oil.
Information on reservoir properties of the pre-Permian section is scanty. Strong flows of gas and drops of the drill stem are positive factors, however. Also, several seals are present in the section. A salt member of Late Ordovician-Early Silurian age is present on the Kochmes high and probably also to the west and north. A thick anhydrite of Serpukhovian age is also extensive. Artenskian argillites are a seal for the Upper Paleozoics.
Oil and gas pools are known now only in the Kochmes and Padimey areas of the outer (northwest) zone of the Kos'yu-Rogov downwarp. Several structures were yet to be explored as of 1985, however. The sub-salt Ordovician-Silurian at greater depth is a favorable play. A strong flow of gas was was recovered from this part of the section in Kochmes well 3.
Ther inner (southeast) zone is very inadequately studied because of its complex geology. Even the structure of the Intin, Kozhim, and Lembin gas fields is not known sufficiently for estimating reserves. Thrust sheets of the region may act as seals here in the inner zone.
Taken from Sivkov, 1985; digested in Petroleum Geology
vol. 23, no. 7/8, one structure map.
Copyright 2003 James Clarke. You are encouraged to print out
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