Timan-Pechora oil-gas province in the northeast part of European Russia has an area of 350,000 sq km. Temperature measurements used in this study were made in drill holes to depths of 2500-3000 m. Maps were compiled showing temper- ature at the top of the Lower Permian rocks, on the pre-Domanik (Upper Devonian) rocks, and on the top of the Proterozoic Riphean rocks, as well as for geothermal gradient of the entire sedimentary section.
On a basis of the geothermal field the surface of the basement is clearly divided into two geo-blocks, the Timan on the west and the Pechora on the east. These geo-blocks are in turn divided into mega-blocks. Temparature range on the Timan geo-block is 20-100 degrees C, and on the Pechora geo-block 110-200 degrees C. An abrupt horizontal temperature gradient corresponds with the boundary between these two geo-blocks, and also with zones of high permeability of the crust, the Ilych-Chikshin and Pechora faults. Numerous intrusions have been emplaced along these faults.
Tectonic activity has played an important role in formation of the oil and gas fields. It was accompanied by increased heat flow so that tectonically active blocks are characterized by maximum geothermal gradients (2.55-2.70 degrees per 100 m).
On the lower stratigraphic horizons of mobile mega-blocks modern temperatures are 80-90 degrees lower than paleo temperatures. There is little difference on the upper horizons, however. There is little difference between paleo and modern temperature for all the section on stable mega-blocks.
Comparison of temperatures on the surface of the Riphean, pre-Domanik, and Lower Permian rocks with calculated paleo temperatures shows the oil-generating potential of the sedimen- tary cover. The highest temperatures are found in the northern parts of the Denisov and Kolvin mega-blocks and on the Koro- taikhin, Kos'-yu-Rogov, and Verkhne-Pechora mega-blocks. The Lower Permian and Carboniferous sediments of the first two of these were capable of generating significant amounts of oil. The Domanik and pre-Domanik could have entered the thermal gas window.
Gas in all probability migrated vertically along faults from the deeper horizons into the Upper Paleozoic and Mesozoic reservoir rocks.
In general, oil-gas and gas fields are characteristic of the mobile mega-blocks, and oil fields are characteristic of the stable mega-blocks.
Taken from Zaporozhdeva, Yegorova, and Gorban, 1985;
digested in Petroleum Geology, Vol. 23, No. 7/8, four maps.
Copyright 2003 James Clarke. You are encouraged to printout
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