Compositional Data Analysis as a tool for interpretation of rock porosity parameters

Abstract

This work examines the possibility of implementing the statistical method, Compositional Data Analysis (CDA), to rock porosity measurement data. The rock samples analysed are different types of sandstones from Poland. Porosimetric measurements were carried out using the mercury injection capillary pressure method, together with computer image analysis. In this paper, compositions of data concerning pore distributions are analysed. Rock pores were distributed in 4 classes of pore dimensions: transitive pores, submacropores, real macropores and over-capillary pores. Based on the CDA methods it was revealed that: there is no constant proportion between transitive and macropores in the sandstones analyzed; the variability of the real macropores, over-capillary and transitive pores and the skeletal grains fraction is mainly one-dimensional. The relative variation between transitive pores and real macropores determines the variability in the sandstone stratigraphical groups; however, these groups are not very distinct as regards the pore sizes and skeletal grains proportion. The rock parameters: median pore diameter; threshold pore diameter and total pore area might be used as independent variables in equations that explain reasonable parts of variability of pore sizes and skeletal grains fraction log-ratios