Oil sources of the Krasnoleninskoe field

Abstract

There is no consensus on the role of different source rocks (SRs) in the formation of the Krasnoleninskoe field. The main Upper Jurassic-Early Cretaceous SR of Western Siberia is represented on the Krasnoleninsky arch by the Tutleim formation (fm) (J3tt–K1v). It is overlain by argillaceous rocks of the Frolov fm (K1v–K1a), underlain by the Abalak (J2cl–J3km), Tyumen (J2a-b), Sherkalin (J1) formations and folded pre-Jurassic basement. All these formations potentially contain SR layers. The purpose of the article is to determine the sources of oil in the Krasnoleninskoe field by comparing oils with SRs and to determine of the history of oil composition formation. Based on a review of known geochemical parameters and the results of statistical analysis new molecular parameters for determining the type of organic matter (OM) and its maturity are proposed. A secondary processes of the oils of the Vikulov fm of the Kamennaya crest has been established, which is associated with the migration of hydrocarbons from the Vikulov fm to the overlying deposits. It is shown that the oils of the Vikulov fm of Kamennaya crest were formed from the SR, which was at the MC2 substage during the generation of hydrocarbons, and the oils of the Jurassic and pre-Jurassic deposits were formed on the end of MC2-beginning of MC3 substages. It was determined that the oils of Kamennaya crest have aquatic initial OM, aquatic OM was found in the Tutleim and Tyumen SRs. According to the criteria of OM type and its maturity, the source of Kamennaya crest oils cannot be determined; therefore, genetic features of the difference between the aquatic OM of the Tyumen and Tutleim formations were found. These features made it possible to estimate the source of oils for different parts of the Krasnoleninskoe field: for Kamennaya crest the Tutleim fm, for the Talinskaya area the Tyumen fm, for the Em-Egovskaya area, the Tyumen and Tutleim formations. Estimation of the contribution of the Sherkalin and Abalak SRs to the formation of hydrocarbon accumulations is beyond the scope of current work.