Investigating Reservoir Characteristics by Mapping P Wave Velocity Dispersion

Abstract

Velocity dispersion allows special insight into the physical properties of reservoir rocks. The total velocity dispersion may provide a link to rock physical properties, such as permeability and concentration of a certain material, but the shape of a velocity dispersion curve, including the critical frequency (fc), can provide more essential information, such as the existence of different attenuation mechanisms. For this purpose, continuous velocity measurement in a broad frequency band is desirable. In this study, we use broadband full-waveform multi-channel sonic logging data from Mallik gas hydrate research wells and measure the P wave velocity (Vp) dispersion curves with the filter-semblance-correlation (FiSCo) method. Profiles of Vp gradient and accumulated dispersion are obtained. In the profiles, the total Vp dispersion and fc are observed varying with several rock physical properties. The Biot's model is then applied to interpret the results. Also Biot's model can generally fit the results, more realistic models are needed to better describe the complicated geological condition of the gas hydrate reservoir.