GEOCHEMISTRY OF OILS IN THE TEREK‐CASPIAN FOREDEEP AND PRIKUMSK SWELL, NE GREATER CAUCASUS, SOUTHERN RUSSIA

Hydrocarbon reserves of the order 1140 MM brl oe have been identified in northern foreland eastern Greater Caucasus, principally Terek-Caspian fold-and-thrust belt and Prikumsk Swell north foredeep. Despite great economic significance these areas their long exploration history, origin hydrocarbons is still poorly understood. In present paper, geochemical data from 73 oil samples representing 28 fields are used to investigate presence families correlate oils with potential source rocks. Biomarker composition Cretaceous Miocene reservoirs mainly controlled by reservoir depth (100-5700 m) maturity (0.70-1.15 %Ro), it therefore difficult separate facies effects. For example, a downward increase diasterane/sterane ratios may indicate change rock or be attributed increasing maturity. Some shallow biodegraded. The short-chain n-alkanes biodegraded indicates recent hydrocarbon migration. (e.g. oleanane) compound-specific isotope suggest that Khadum Formation lower part Maikop Group main rock. However Paleogene organic-rich rocks, which also contributed accumulated oils, urgently needed quantify possible input. Swell, at least two families, characterized low high C28/C29 sterane respectively, can distinguished rocks Triassic age. Most absence oleanane (“Group B oils”). These characteristics pre-Upper for supported geological setting. Hierarchical cluster analysis suggests four sub-groups (Sub-Groups B1 B4). Typically, biomarker more uniform than those Jurassic reservoirs. Potential include Lower deep-water clayey limestones shales as well Middle Aptian-Albian marine shales. Three form family A”), genetically related belt. A general contain some oleanane. contribution Cenozoic likely.