An effective method to calculate permeability based on Stoneley waves

摘要

An algorithm of extracting formation permeability from array waveform data is specially designed for multipole array acoustic logging tool (MPAL). Purely transmitted Stoneley waves are obtained after digital filtering and waveform truncation. The corresponding amplitude curves of Stoneley waves are acquired by carrying out a Fast Fourier Transformation (FFT). Weighted spectral semblance method is used to calculate the slowness dispersion curve of Stoneley waves, and attenuation dispersion curves are obtained by using the least square fitting method. Matrix equation based on the boundary conditions at the borehole wall is applied to calculate slowness dispersion curves of Stoneley waves of equivalent elastic formation. At the end, the simplified Biot-Rosenbaum model is used to inverse formation permeability. This method is attached to log evaluation and application desktop (LEAD) of CNPC to process the logging data of oilfields. Processing results demonstrate that this method is able to calculate formation permeability fast and effectively, and the permeability obtained this way has good consistency with that of the nuclear magnetic resonance (NMR) method.