The influence of pore media distribution on the elastic parameters of rocks in Miocene sediments (Carpathian Foredeep, Poland, B deposit)

Abstract

This paper presents the results of modelling compressional and shear wave velocities and elastic moduli, as well as Poisson’s coefficient changes in sandstone-shale rocks, based on the distribution of media reservoir (water, gas) in the pore space. Modelling was performed using the Estymacja-TP computer program and theoretical Kuster–Toksöz and Biot–Gassmann relationships. Phase distribution of saturating pores (ellipsoidal shapes) in several ways was assumed. Calculations were made of elastic parameters in the deposits of the autochthonous Miocene Sarmatian in the borehole B-4. Using a method similar to the so-called »fluid substitution« velocity of compressional and shear waves, elastic moduli, Poisson’s ratio and bulk density, under various conditions of water and gas saturation, were calculated. The assumed change in water saturation ranged from S$_{w}$ = 0% to 100%.