Effective medium modeling of diagenesis impact on the petroacoustic properties of carbonate rocks

Abstract

1Carbonate formations are heterogeneous and their velocity -porosity relationships are mainly controlled by microstructural parameters. As diagenesis is responsible for important changes in the microstructure of carbonate rocks, we propose here to extend the classic effective medium approach to mode! the impact of diagenesis on carbonate elastic properties through a step by step effective medium modeling. Two different carbonate formations are considered. The first key step is the characterization of the diagenesis which affected the studied carbonate series.An effective medium mode! integrating ail the geological information accessible from thin section analysis is then built. The evolution of the micro structural parameters during diagenesis is thoroughly constrained based on an extensive experimental dataset, including XRD analysis, various porosimetry techniques and ultrasonic velocities measurements. Finally, direct calculations with the mode! provide elastic wave velocities representative of the different diagenetic stages. An extrapolation to permeability evolution is also introduced. This approach allows the identification of the acoustic signature of specific diagenetic events, such as dolomitization, dissolution or cementation, and the assessment of their impact on the flow properties of carbonate formations.

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

“…The main phases identified from the XRD analysis are consistent with thin section analysis (Adelinet et al, 2018) and consist in calcite, dolomite and silicate, this last phase grouping quartz and a small fraction of feldspars. Other scarce phases such as clay minerals are neglected.…”

“…The upscaling of the obtained results at the log and the site scales would moreover require integrating the heterogeneity distribution resulting from the sedimentological and diagenetic history of the studied carbonate formations. An effective medium modeling approach based on a comprehensive petrographic characterization has thus been implemented and is presented in a companion paper (Adelinet et al, 2018 We have proposed an experimental approach allowing a consistent checking of the validity of Biot-Gassmann's equation for a given carbonate formation without referring to lesscontrolled dry measurements and without any assumption on the solid matrix bulk modulus. The obtained results moreover permit the direct identification of any weakening or dispersion effects.…”

“…The measured phase velocities are then more representative of the sample macroscopic behavior (Cadoret et al, 1995;Rasolofosaon and Zinszner, 2012;Bemer et al, 2016). (Adelinet et al, 2018).…”

“…The objective of our work is to derive an integrated experimental workflow designed to allow a consistent checking of the applicability of Biot-Gassmann's equation and provide key geological and microstructural information for an effective medium modeling approach presented in a companion paper (Adelinet et al, 2018). We first present the specific test sequence which includes petrographic analysis, petrophysical and petroacoustic testing and microstructure analyses.…”

A workflow for multimineralogic carbonate rock physics modelling in a Bayesian framework: Brazilian pre‐salt reservoir case study

“…One of the main objectives of rock physics modelling is to build a calibrated model accurately representing the reservoir elastic behaviour at calibration well locations and to take advantage of its extrapolation power to estimate elastic attributes away from these locations. For carbonate rocks, theoretical inclusion models have been used to quantitatively understand the main factors driving their elastic attributes (Agersborg, 2007; Xu and Payne, 2009; Fournier et al ., 2018; Adelinet et al ., 2019; Dias et al ., 2019). These models divide the rock in three nested units: matrix, pore network and fluids as we illustrate in Fig.…”