InterPore2026

Evaluation of the pore pressure influence on the acoustic velocities of Brazilian carbonate rocks

21 May 2026, 15:35

1h 30m

Poster Presentation (MS01) Porous Media for a Green World: Energy & Climate Poster

Speaker

MARCO CEIA (State University of North Fluminense Darcy Ribeiro (UENF))

Description

Acoustic velocities of reservoir rocks are dependent on in-situ stresses and pore pressures. However, loading or unloading stages may also influence acoustic velocities in distinct ways (Wang and Wang, 2015). An important application of understanding the sensitivity to effective pressure for velocity is in modeling 4D response, which impacts oil and gas exploration (Cruz et al., 2021) and CO2 storage monitoring (Lumley, 2010).
This work shows the results of lab experiments designed to measure acoustic velocities during pore pressure loading and unloading processes (Fig.1). Ultrasonic transmitted wave tests were performed on Brazilian pre-salt carbonate samples and Coquinas extracted from an outcrop of Morro do Chaves Fm. (NE Brazil). The core plugs were saturated with a high-salinity synthetic brine that aims to represent a typical Brazilian Formation Water (BFW) (Façanha et al., 2016). The experiments were performed using a triaxial system, which is composed of a pulse generator unit, three pairs of piezoelectric transducers: one P-wave (1.3 MHz) and two independent orthogonally polarized S-wave (900 kHz) at each vertical (Z-axis) and lateral (X and Y-axes) position, and an oscilloscope to detect the signal output. The measurements were performed by exploring a range of 10-25 MPa effective pressure and provided monitoring of P- and S-wave velocities in mean stress directions during different loading/unloading cycles (Fig. 2).
A velocity-pressure model (Wang & Wang, 2015) was also tested, yielding highly accurate predictions (R² > 0.8). Petroacoustic studies of complex carbonates addressing pressure sensibility are scarce in the literature. In the case of Brazilian carbonate rocks, it is even rarer. This way, this work aims to contribute to the understanding of velocity behavior in response to pressure variation. Such info is usually important for rock physics modeling of porous rocks with impacts to the mechanics and flow behavior.