The Effect of Porosity on the Seismic Waves Velocities and Elastic Coefficients In A South-Western Iran’S Carbonate Oil Field

Seismic characteristics of reservoir rock provide the main data in the exploration of seismology, processing, and interpretation of the characteristics of hydrocarbon reservoirs. in this study, petrophysical and geophysical laboratory measurements were performed on 35 samples made of limestone in a south-western iran’s carbonate oil field. parameters including porosity, density, and permeability were measured along with the samples’ compressional and shear wave velocities under reservoir conditions. also, in the study of microscopic thin sections, factors affecting the velocity of waves, including porosity, poisson’s ratio, density, pressure, and pore type, were investigated. the scattering of points in the velocity diagrams of elastic waves based on the petrophysical parameters of the rock indicates that the most important factor of velocity changes is the pore type in the samples with the same porosity value. also, it is impossible to detect reflectors due to low wave amplitude by acoustic impedance changes. for this purpose, in the studied reservoir, lmr parameters (λ(l), μ(m), which are lame’s coefficients and ρ(r) which is density) were calculated using laboratory results of velocity measurement. the values of lmr parameters of seismic data were determined by the velocities of compressional and shear waves in the pre-stack stage seismic. then, using seismic inversion, compressional and shear wave resistances were estimated, and seismic sections with λ.μ and μ.ρ parameters were created. the results show a good correlation between laboratory measurement of rock physics and pre-stack seismic data. also, the factor affecting the velocity of waves, i.e., the pore types, should be considered. uncertainty in velocity values due to the diversity of pores can show differences in the velocity of elastic waves in the same porosity value to about 1500 m/s. also, porosity changes of up to 20 percent are visible at a constant velocity.