Detection of productive intervals using acoustic wave velocity

Abstract

Detection of productive intervals is a very important task in reservoir studies. Reliable reserve estimation and proper depth of production logging and well perforation depend upon accurate recognition of pay zones. In this study, velocity-permeability and velocity-deviation logs have been used to detect productive intervals for a carbonate oil reservoir. Permeability trends are revealed by constructing a velocity deviation log from a combination of the sonic log and the density and neutron porosity logs. Then the behaviour of acoustic waves in productive intervals is demonstrated and their application in the detection of productive intervals is described. This study shows that a productive interval has relatively low compressional and shear velocities, low impedance, small negative peaks of the velocity-deviation log and high porosity and resistivity. On the whole, this approach employing more criteria, prevents the possible errors of conventional methods which use simple cutoffs for defining pay zones.