EXPERIMENTAL ANALYSIS ON P-WAVE ATTENUATION IN CARBONATE ROCKS AND RESERVOIR IDENTIFICATION

摘要

Understanding the relationships between seismic wave responses and rock properties is a key factor for quantitative seismic interpretation and characterization of complex hydrocarbon reservoirs. We have performed laboratory ultrasonic measurements on 10 carbonate samples and recorded the waveforms under different conditions, such as varying pore-fluid types, confining and pore pressures and partial saturations. P- and S-wave velocities are measured on the basis of the first arrivals and the attenuation of P-waves is estimated by use of the spectrum-ratio method on the transmitted signals. The sensitivity analysis based on the experimental results show that P-wave attenuation is one of the most sensitive indicators for rock porosity and permeability, especially for low porosity rocks. P-wave attenuation is then used to identify the high quality carbonate reservoirs from the actual stratum on the basis of the post-stack seismic data. The inverse quality factor Q(-1) is estimated by using the spectral ratio method based on a generalized S-transform of the post-stack seismic data. The empirical relations between porosity, permeability and P-wave attenuation, which are derived from the experimental measurements, are then applied to the values obtained from seismic profile. We predict the reservoir porosity and permeability from the carbonate stratum. The prediction results are in good agreement with the well log production reports, validating P-wave attenuation as an effective indicator for directly characterizing in-situ carbonate reservoirs.