Rock Physics Characterization Using Acoustic Velocity Measurements On Late Cretaceous Carbonate Rocks From the Middle East

Abstract

We conducted laboratory measurements of Vp (compressional waves), Vs (shear waves), porosity and permeability on forty nine dry carbonate core plug samples at ambient pressure and temperature. We also, performed an initial lithological description, based on Dunham's carbonate rock classification to fully characterize the samples. The study results were analyzed to search for potential correlations between the different rock properties and lithological characteristics. We used cross plots of porosity-permeability, Vp - porosity, Vs - porosity, Vp - permeability, Vs – permeability, and Vp-Vs, for all samples and each rock type. The preliminary results from our analysis suggest that the acoustic velocities are highly affected by heterogeneity. The study also confirms an inverse relation between porosity and acoustic velocities, where pore size and pore type can be the main factors controlling the acoustic response at a given porosity. In addition, a general inverse tendency between permeability and acoustic velocities is found. The results also show that carbonate mudstones follow consistent trends of porosity-permeability, Vp - porosity, Vs - porosity, Vp - permeability, and Vs - permeability. This result can probably be attributed to the relativlely more uniform internal structure of carbonate mudstones compared with the other carbonate rock types. Wackestones and packestones present relationships that are less consistent and more dispersed than the ones found for mudstones for instance. The rest of the rock types display a great scatter and non apparent relationships. Finally, we find an empirical correlation between Vp and Vs that can be used to identify gas zones. This study has a great significance in the process of a better understanding of how acoustic velocities from different types of carbonate rocks relate to each other and to their rock properties. This knowledge can potentially be used to diagnose gas zones, predict Vs values, identify different types of carbonate rocks using well log data, and improve seismic interpretation and inversion.

Controlling Factors on Petrophysical and Acoustic Properties of Bioturbated Carbonates: (Upper Jurassic, Central Saudi Arabia)

“…A series of studies investigated the relationship between acoustic velocity and permeability and tried to define the factors controlling acoustic velocity and permeability in carbonates [64,[71][72][73][74][75], and found that pore structure, size, connectivity, and distribution are the main factors controlling acoustic velocity and permeability. The majority of these studies have shown an inverse relation between permeability and acoustic velocity, either as direct or indirect relation.…”