Abstract: Precambrian source rocks and predictions oil-bearing within the central part of Russian Plate
AREFIEV, OLEG A., IGIRGI, OLGA K. BAZHENOVA*, and BORIS A. SOKOLOV
Precambrian sedimentary formations are widely spread within Russian Plate. Riphean deposits up to 4 km thick fill in narrow graben, while Vendian formation up to 1,5 km thick have more wide distribution. The inflow of oil and oil shows are revealed along the whole Precambrian succession.
Sedimentary rocks in sections studied are represented by clayey-terrigenous rocks. The content of TOC in the most part of the samples studied is not high -0.02-0.2%, but five such intervals of source rocks were identified in the deepest section of Pavlovo-Posad well (Moscow graben) with TOC content up to 5-6%, and synbitumen to 0.1%, genetic potential to 5.5 kg HC/t of rock.
The distribution of alkane HC is characterized by not high content of n-alkanes (5-15%) and prevalence phytane over pristane (Pr/Ph 0.6-0.8). According to the character of the distribution of steranes HC there were revealed two types of OM and oils, genetically associated with it, i.e. type 1 - with proportional distribution of steranes and 2-type, with distinct prevalence of ethylholestane.
Summarizing all the maturity indicators (pyrolysis data-Tmax, PI, biomarker ratios for maturity assessment such as sterane indices, Ts/Tm ratio) it is concluded that the degree of maturation of Riphean OM in the Moscow graben does not exceed the middle of maturity stage MC2 (corresponding to Ro of 0.7-0.75%). The OM of Vendian rocks is lower maturity (Ro less than.5%).
Within Precembrian complex two oil groups are distinguished: 1. Heavy, naphteneous oils of the Verkhne-Kamsk depression. These oils are proper Precambrian, 2. Light methane's oils of Danilovsk area; these oils are young.
AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria