Geology aspects of upper Devonian reef deposits in Timan-Pechora oil and gas bearing province

Abstract

The paper analyzes the structure of Upper Devonian reef strata within Moroshkinsky, Ust-Tsilemsky and Severo-Tebuksky reference sites located in the territory of the Komi Republic and Nenets Autonomous Okrug. Based on the re-interpretation of the materials of geophysical well logging involving lithologic description of core and results of its laboratory studies, a detailed analysis of the structure of Domanic-Famenian part of the profile has been made, and a correlation pattern for deep well profiles has been drawn. As a result of well log correlation, some of the stratigraphic boundaries have been updated, the scope of lithologic and stratigraphic subdivisions has been determined, reference bands with good visibility on geophysical diagrams and easily traceable carbonate formations known to geologists as F1, F2, F3, F4, F5, as well as inter-formation bands, have been specified. The paper contains the results of a geochemical study of the Upper Devonian reef deposits of the wells drilled in the territory of Moroshkinsky, Ust-Tsilemsky and Severo-Tebuksky sites. It presents content distribution of organic carbon, chloroform and alcohol-benzol extracted bitumoids in the rocks of certain well horizons, and describes oil generation potential of the rocks on the basis of pyrolytic data. Based on the comprehensive analysis of the results of laboratory core analysis and materials of production log tests, reservoir quality discrimination has been performed, an evaluation of their quantitative parameters and fluid content has been made. Porosity factor has been selected as the criterion for evaluation of reservoir properties of the rocks. Determination of porosity by neutron gamma-ray logging has been performed following the method of two guide formations using the dependencies developed by JSC KamNIIKIGS. For evaluation of quantitative parameters of carbonate reservoirs, the results of standard core analysis were used: effective porosity, absolute permeability to gas, and volumetric density. The results of the research can be used during prospecting and exploration in the territory of the three reference sites of interest.

Keywords

• timan-pechora oil and gas bearing province
• core
• profile
• well
• organic matter
• bitumoid
• oil source rocks
• rock eval pyrolysis
• ir spectrometry
• re-interpretation
• geophysical well logging
• porosity
• reservoir