Petrophysical model of sedimentary rocks from Ruhnu borehole, Estonia

Physical properties of 113 Estonian sedimentary rock samples from Ruhnu borehole were studied together<br>with their chemical composition and interpreted using correlation analysis. Stratigraphic sequence<br>represented by carbonate and siliciclastic rocks was deposited during eight sedimentary cycles. Studied data<br>set was subdivided into the six lithological rock groups, distinguished by chemical composition and rock<br>properties. Distinct correlations were obtained for limestones together with calcareous marlstones and for<br>dolomitized carbonate rocks (dolostones and dolomitic marlstones). Correlation coefficients were higher for<br>limestones with calcareous marlstones for porosity-dependent parameters. The lowest porosity and iron<br>content were in pure limestones. Primary porosity and iron content had high positive correlation with clay<br>content in the studied rocks. Secondary porosity was determined in the dolomitized carbonate rocks. The<br>highest porosity and the lowest density were measured in the silicicalstic rocks represented by sandstones<br>and siltstones. Porosity, density, P-wave velocity, electric resistivity, thermal conductivity and magnetic<br>susceptibility of dolostones were higher than of limestones. Obtained results may serve as a basis for<br>interpretation of geophysical, petrophysical and geological data in Estonia and for correlation of sedimentary<br>beds in the other parts of the Baltic sedimentary basin.