Exploration is past maturity for moderate depths in many areas of Russia; consequently, attention is turning to targets at great depth. Drilling of deep and super-deep wells is part of a program for increasing effectiveness of exploration. Results from three such wells are examined here: Kolva deep parametric well (depth of 7057 m), Timan-Pechora stratigraphic well (depth of 6904 m), and Tyumen super-deep well (depth of 7502 m). Kolva deep parametric well in Timan-Pechora oil-gas province supplied substantial new information on the Pechora-Kolva aulacogen, which is the main tectonic feature for the Paleozoics of the province. Thickness of the Lower Devonian turned out to be four times greater than had been assumed, and that of the Upper Silurian is two fold greater. Filling of this aucologen was by clay and clay-carbonate deposits, some of which are bituminous Domanik type, raising the assessment for this play. Timan-Pechora stratigraphic well penetrated a clastic-carbonate section, which in the lower part in the Lochkovian and Eifelian of the Devonian was found to be much thicker and more extensively intruded by dolerite sills than had been held earlier. Reflecting seismic interfaces correlated earlier with lithologic boundaries proved to be associated with these intrusions. Tyumen super-deep well did not confirm the assumed sedimentary nature of the Triassic rocks of the inner zone of the Lower Pur mega- downwarp. Contrary to the geophysical data, the well disclosed volcanic rocks in the rift. Not one of these wells confirmed the assumed geologic section at depth. This in turn raises doubts as to predictions of the oil and gas potential at great depths. These wells were drilled in regions that had been studied by geophysical surveys; consequently, the geophysicists now have abundant factual data for correcting their concepts as to the nature of the deep subsurface. In general oil shows are found to depths of 5000 m. At these depths there is a sharp drop in bitumen content. Below 5500 m solid bitumen insoluble in the usual solvents begins to be observed. This material differs from disseminated organic matter and is provisionally called pyrobitumen. Less deep-occurring rocks with pyrobitumen found in the Devonian of Timan-Pechora well have turned out to be associated with igneous intrusions. In Kolva and Tyumen wells pyrobitumens make their appearance at depths of 5500-6000 m, where modern temperatures are less than 150 and 165-175 degrees C, respectively. The temperature of distruction of oil hydrocarbons is then somewhat lower than proposed earlier, in spite of presence of overpressure, which commonly plays a stabilizing role for oil hydrocarbons. The geochemistry of the pyrobitumens of the Silurian carbonates in Kolva well indicates that they are a relict of an oil pool that was destroyed by thermal and oxidation-reduction processes. The most important result of the super-deep drilling has been the finding of reservoirs at great depths. Silurian carbonates in Kolva well yielded abundant water from a depth of 6890-6906 m. In the Tyumen well reservoirs with porosity up to 19 percent and good permeability are present at depths greater than 5000 m. (Taken from Belokon, 1998; digested in Petroleum Geology vol. 33, no. 3, p.311-318; lithologic sections and geophysical well logs). Copyright 2000 James Clarke. You are encouraged to print out this News Letter and to forward it to others. Earlier News Letters are available at http://geocities.com/internetgeology Inquiries concerning Petroleum Geology may be made by telephone at (703) 759-4487 or by FAX at (703) 759-3754.