GEOCHEMICAL CHARACTERISTIC OF POTENTIALLY OIL AND GAS SOURCE ROCKS OF THE SAKHALIN BAY SEQUENCE (BASED ON STUDIES OF WELL ASTRAKHANMORE-1)
The article presents results of studying organic matter (OM) along sequence of well Astrakhan-more-1 done in analytical laboratory of OOO “RN-SakhalinNIPImorneft” and laboratory of geological faculty of Lomonosov Moscow State University for the purpose of evaluating oil and gas prospects of offshore Sakhalin bay. In process of study the most enriched OM intervals relating to Daekhuriinskiy and Uyninskiy horizons of Oligocene and Lower Miocene age have been distinguished. In overlying deposits of Daginian, Okobykaiskiy and Nutovskiy horizons of Lower Miocene-Pliocene age the potentially source rocks were not revealed. Values of hydrogen index (HI) are not high for deposits considered. Generation rock potential of Uyninskiy and Daekhuriinskiy horizons is determined as satisfactory. Studies of syngenetic bitumoids from rocks of Daekhuriinskiy horizon show the prevailing aline components in OM composition. Character of original HC potential distribution by activation energy for kerogens from Uyninskiy and Daekhuriinskiy horizon samples is mostly similar to kerogens of the II type. By data on vitrinite reflectivity (R o) and T max kerogen decomposition, extent of OM catagenetic transformation for deposits of Nutovskiy, Okobykaiskiy and most part of Daginian horizon corresponds to gradation of middle protokatagenesis (PK 2). Katagenesis of deposits of lower part of Daginskiy oflingg, Uyninskiy and stripped part of Daekhuriinskiy horizons at maximum depth of their plunging of 3,4 km is not beyond limits of late protokatagenesis (PK 3). Beginning of the main oil generation zone in this region is forecasted from depth of burial of 3,5 km.