Compressional and shear wave velocity in terms of petrophysical parameters in clean formations

Abstract

This paper is aimed to introduce an approach for evaluating compressional and shear wave velocities via the neutron, density, gamma ray logs and poissons ratio (σ ) in a very simple way for different types of lithologies provided that this approach assumed matrix to be known from any one of the sources employed for such objectives. The approach taken in this present study based on the well known Dresser Atlas [Dresser Atlas, 1979: Log Interpretation Charts. Dresser Industries Inc., Houston, Texas, 107p.] equations for computing porosity. This can be achieved by merging such equations with the well known effective porosity equation in order to end up with a formula for both compressional and shear wave velocities as a function of neutron, density, shale volume poissons ratio; taking into account the effect of both matrix and fluid nature. A number of measurements, including compressional, shear and all elastic moduli, are used to test the proposed approach and compare its results with those obtained. The success of such comparison give us the opportunity to apply the suggested formula to real field data in the northern part of the Gulf Of Suez basin. The results of both test and application came in a good agreement and the small existing error can be negligible.