COMPARISON OF THE COMPOSITIONS OF HEAVY MORDOVO-KARMAL CRUDE-OIL AND SUGUSHLINY BITUMEN EXTRACTED FROM BITUMINOUS SANDSTONE OF PERMIAN DEPOSITS IN TATARSTAN

An investigation has been made of the compositions of two characterist ic fossil fuels encountered in Permian deposits in Tatarstan: heavy cr ude oil with a density of 0.9413 g/cm(3), concentrated in reservoir ro ck, and semiviscous bitumen with a density of 0.9945 g/cm(3), disperse d in bituminous sandstone outcrops. These are classified as type B-2 a nd B-1 oils respectively. It has been established that oils of these t ypes have a common origin but differ substantially in their component and fractional compositions. Here a distinguishing feature of the bitu men, besides the absence of normal and isoprenoidal alkanes, and also the low content of vanadyl porphyrins, is the considerable predominanc e of asphaltenes and resins extracted with an alcohol-benzene mixture and rich in hydroxyl and ester groups. It has been shown that thermal degradation of the bitumen is more intense than that of the crude oil, with the formation of considerable amounts of hydrogen sulphide and m ercaptans owing to the breakdown, above all, of resins extracted from silica gel with an alcohol-benzene mixture and formed with the partici pation of sulphur and oxygen atoms. As a result of comparing the natur al variations observed in the composition of the Permian specimens inv estigated with experimental data obtained during the action of atmosph eric and microbiological factors on Devonian type Al paraffinic crude oil, it is concluded that, by comparison with heavy crude oil, bitumen in rock is the product not only of more extensive biochemical oxidati on, but also of subaerial weathering of, it appears, fairly light crud e oil that has migrated from lower-lying layers.