Results of petromagnetic studies of core material from the Tyumen suite and Paleozoic basement rocks

This paper examines the results of determining the petromagnetic properties (magnetic susceptibility, thermomagnetic coefficient, and residual magnetization) of core material from a borehole located within the Navsky swell (West Siberian region). Stratigraphically, the core material consists of Jurassic sedimentary rocks and Paleozoic basement rocks. Paleozoic basement rocks are classified as having hard-to-recover reserves. The objective of this study is to obtain information on the petromagnetic properties of Jurassic and Paleozoic basement core material to assess the distribution of magnetic minerals and provide a detailed lithological subdivision of the studied deposits. It has been established that the following are readily identified in the Danilovskaya Formation: argillites by low values of magnetic susceptibility and residual magnetization; interlayers with elevated siderite concentrations by an increase in magnetic susceptibility and a decrease in the thermomagnetic coefficient. The petromagnetic properties of rocks of the Tyumen Formation can be used to: identify changes in lithological types in the section, namely, the change from the Danilovskaya Formation mudstones to the Tyumen Formation siltstones based on an increase in residual magnetization, as well as to identify layers with an increased siderite content based on an increase in magnetic susceptibility and a decrease in the thermomagnetic coefficient. The petromagnetic properties of Paleozoic basement rocks can be used for their detailed subdivision, namely: identifying weathering crust rocks based on magnetic susceptibility and thermomagnetic coefficient values; basalts based on magnetic susceptibility and residual magnetization; and effusive rocks of acidic composition based on magnetic susceptibility and residual magnetization.

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