In-situ permeability estimation : a comparison between acoustic and NMR logs

Abstract

The estimation of formation permeability from full waveform acoustic and nuclear magnetic resonance (NMR) logs in petroleum well logging has improved significantly in recent years. In this thesis, we review the methods of permeability estimation from Stoneley waves and provide permeability comparisons between acoustic and NMR logs. When a Stoneley wave travels along a permeable formation, hydraulic exchange between the Stoneley wave and formation will occur. As a result, Stoneley wave travel time will be delayed and the Stoneley wave attenuation will increase, causing a centroid frequency shift. Therefore, these two wave attributes can be used to estimate formation permeability. NMR logging data can also be used to estimate permeability. Permeability estimates using Stoneley waves and NMR logging were tested using data from a section consisting of sandstone and shale beds. The permeability results show very good correlation for these two different methods. Data from a gas zone that is analyzed shows high permeability values from acoustic data and low values from NMR. The difference between these two permeability results can be used as a gas zone indicator.