Consistent experimental investigation of the applicability of Biot-Gassmann’s equation in carbonates

Abstract

Carbonate formations are characterized by multiscale heterogeneities that control their acoustic response and flow properties. At the laboratory scale, carbonate rocks do not indicate a strong correlation between P- and S-wave velocities and porosity. The velocity disparities between carbonates of similar mineralogy and porosity result from different microstructures derived from their sedimentary facies and subsequent diagenetic transformations. The still-discussed applicability of Biot-Gassmann’s equation for fluid substitution in carbonate rocks remains another key issue. We have developed an integrated experimental workflow that allows a consistent checking of the applicability of Biot-Gassmann’s equation and provides key geologic and microstructural information to understand the petroacoustic signature of carbonate rocks. The defined approach is based on the phase-velocity measurements performed in liquid-saturated conditions using polar and nonpolar fluids. It allows the identification of the whole set of parameters required by Biot-Gassmann’s equation including the bulk modulus of the solid matrix. This approach is implemented on samples representative of two different carbonate formations deposited in lacustrine and marine environments, respectively. The obtained results demonstrate the applicability of Biot-Gassmann’s equation for the two studied carbonate families and indicate the link between their petroacoustic signature and diagenetic history.

Acoustic Insights into Facies-Dependent Pattern and Characterization for Aiding Exploration and Sequestrations Efforts in Bassein Carbonate Formations

“…To express the observation of velocity and the associated attenuation and dispersion in quantitative terms for reservoir description and performance behaviour, the relationship between seismic wave velocity and porosity has been the subject of numerous studies, e.g., (Anselmetti & Eberli, 1993;Verwer et al, 2010). Rock physics models attempt to confirm the applicability of fluid substitution (Baechle et al, 2005;Bemer et al, 2019;Gassmann, 1951;Gregory, 1976;Wang et al, 2015). However, it is still unknown if the wave-induced fluid movement may produce dispersion and attenuation of the wave velocities and if seismic, logs, or ultrasonic measurements may be impacted due to the range of pore types unique to carbonates.…”

Effects of pore fluids on quasi‐static shear modulus caused by pore‐scale interfacial phenomena

“…Vo-Thanh (1995) conducted laboratory measurements of acoustic velocities of sandstone and limestone, saturated with different pore liquids at the different degree of saturation, however we cannot use Vo-Thanh (1995) results for validation of our theory because laboratory measurements were conducted at ultrasonic frequency of 1MHz. The same comment is applied to the recent publication of Bemer, Hamon and Adelinet (2019), who studied dynamic properties of carbonate rock at ultrasonic frequency of 0.5 MHz. They found that unrelaxed shear modulus of the rock saturated with different pore liquids depends on the bulk moduli of pore liquids.…”