Multi-frequency rock physics measurements and dispersion analysis on tight carbonate rocks

Tight carbonate rocks have formed complex pore structure through diagenesis and post-diagenesis. Their elastic properties are not only related to porosity, but also closely related to pore structure. In order to further study the velocity dispersion characteristics of fluid correlation in tight carbonate rocks, it is very important to measure the dispersion and analyze the dispersion theory in the laboratory. In this study, a typical tight carbonate rock sample is selected. Based on the detailed description of the pore structure of the sample, including CT scanning and microscopic thin section, the laboratory cross frequency (from seismic frequency band to ultrasonic frequency band) dispersion measurement and dispersion response analysis are carried out. Comparing laboratory cross-band measurement results and dispersion curve from theoretical modeling, we can obtain the following understanding : 1) Compared with the typical squirt flow mechanism, the improved squirt flow model can semi-quantitatively explain the results of frequency dispersion measurements, which greatly improves the understanding of the dispersion response of tight carbonate rocks; 2) The improved squirt flow model still cannot exactly match laboratory dispersion measurement results. This shows that in addition to the microscopic squirt flow mechanism, there are other mechanisms that control dispersion and attenuation; 3) This work provides a theoretical basis for studying seismic wave responses in different frequency bands in tight carbonate reservoirs for reservoir prediction and fluid identification.