AN IMPROVED APPROACH TO DERIVE POROSITY FROM THE ACOUSTIC LOG

It is important in log interpretation to accurately estimate porosity. With the exception of core
measurements, the porosity tool responses (density; ρb, neutron; ɸN, and acoustic; Δt) can all be defined by equation
in which porosity is a factor, and which can therefore be solved for porosity. Also useful information about porosity can
be obtained by using a combination of at least two of these logs. This paper is mainly addressed to shed more light on
some approaches used to determine the sonic-derived porosity and to introduce an equation for estimating porosity
from acoustic logs. The equation can be simply achieved by merging Raymer et al. (1980) transform and Raiga-
Clemenceau et al. (1988) since the first takes into account the effect of matrix and fluid transit time, whereas the
second takes only the effect of matrix transit time and matrix nature into consideration. However, the proposed
equation combines in its structure all parameters included in both equations, which in our opinion enhances the
accuracy of computing porosity from acoustic logs. This equation was tested among a wide variety of samples
representing different lithology. The results obtained from its application showed particularly a good agreement with
experimental data in various cases subjected to study particularly with clean lithology material.