Measurements of the elastic and anelastic properties of sandstone flooded with supercritical CO 2

We present a comprehensive characterization of the physical, mineralogical, geomechanical, geophysical and hydrodynamic properties of Corvio sandstone. This information, together with a detailed assessment of anisotropy, is needed to establish Corvio sandstone as a useful laboratory rock-testing standard for wellconstrained studies of thermo-hydro-mechanical-geochemical coupled phenomena associated with CO 2 storage practices and for geological reservoir studies in general. More than 200 core plugs of Corvio sandstone (38.1 and 50 mm diameter, 2:1 length to diameter ratio) were used in this characterization study, with a rock porosity of 21.7 ± 1.2%, dry density 2036 ± 32 kg m -3, and unconfined compressive and tensile strengths of 41 ± 3.28 and 2.3 ± 0.14 MPa, respectively. Geomechanical tests show that the rock behaves elastically between ~10 and ~18 MPa under unconfined conditions with associated Young's modulus and Poisson's ratio of 11.8 ± 2.8 GPa and 0.34 ± 0.01, respectively. Permeability decreases abruptly with confining pressure up to ~10 MPa and then stabilizes at ~1 mD. Ultrasonic P-and Swave velocities vary from about 2.8 to 3.8 km s -1 and 1.5 to 2.4 km s -1 , respectively, over confining and differential pressures between 0.1 -35 MPa, allowing derivation of associated dynamic elastic moduli. Anisotropy was investigated using oriented core plugs for electrical resistivity, elastic wave velocity and attenuation, permeability and tracer injection tests. Corvio sandstone shows weak transverse isotropy (symmetry axis normal to bedding) of <10% for velocity and <20% for attenuation.

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Characterisation and multifaceted anisotropy assessment of Corvio sandstone for geological CO₂ storage studies

Falcón-Suarez

Canal-Vila

Martín

et al. 2016

“…Batzle et al . ; Tisato and Madonna ; Mikhaltsevitch, Lebedev and Gurevich ; Pimienta, Fortin and Guéguen ; Spencer and Shine ; Szewczyk et al . ).…”

Section: Experimental Details and Data Analysisunclassified

Static and dynamic stiffness measurements with Opalinus Clay

Lozovyi

Bauer

2018

In this work, an experimental study was carried out with the aim of reconciling static and dynamic stiffness of Opalinus Clay. The static and dynamic stiffness of core plugs from a shaly and a sandy facies of Opalinus Clay were characterized at two different stress states. The measurements included undrained quasi‐static loading–unloading cycles from which the static stiffness was derived, dynamic stiffness measurement at seismic frequencies (0.5–150 Hz) and ultrasonic velocity measurements (500 kHz) probing the dynamic stiffness at ultrasonic frequencies. The experiments were carried out in a special triaxial low‐frequency cell. The obtained results demonstrate that the difference between static and dynamic stiffness is due to both dispersion and non‐elastic effects: Both sandy and shaly facies of Opalinus Clay exhibit large dispersion, that is, a large frequency dependence of dynamic stiffness and acoustic velocities. Especially dynamic Young's moduli exhibit very high dispersion; between seismic and ultrasonic frequencies they may change by more than a factor 2. P‐wave velocities perpendicular to bedding are by more than 200 m/s higher at ultrasonic frequencies than at seismic frequencies. The static undrained stiffness of both sandy and shaly facies is strongly influenced by non‐elastic effects, resulting in significant softening during both loading and unloading with increasing stress amplitude. The zero‐stress extrapolated static undrained stiffness, however, reflects the purely elastic response and agrees well with the dynamic stiffness at seismic frequency.

“…; Behura et al . ; Takei, Fujisawa, and McCarthy ; Tisato and Madonna ; Madonna and Tisato ; Mikhaltsevitch, Lebedev, and Gurevich ; Pimienta, Fortin, and Guéguen ). Ultrasonics : Two ultrasonic transducers are employed on either side of the rock sample, one as a source and the other as a receiver.…”

Section: Techniques Of Attenuation Measurementsmentioning

confidence: 99%

An overview of laboratory apparatuses to measure seismic attenuation in reservoir rocks

Subramaniyan

Quintal

Tisato

et al. 2014

Intrinsic wave attenuation at seismic frequencies is strongly dependent on rock permeability, fluid properties, and saturation. However, in order to use attenuation as an attribute to extract information on rock/fluid properties from seismic data, experimental studies on attenuation are necessary for a better understanding of physical mechanisms that are dominant at those frequencies. An appropriate laboratory methodology to measure attenuation at seismic frequencies is the forced oscillation method, but technical challenges kept this technique from being widely used. There is a need for the standardization of devices employing this method, and a comparison of existing setups is a step towards it. Here we summarize the apparatuses based on the forced oscillation method that were built in the last 30 years and were used to measure frequency‐dependent attenuation in fluid‐saturated and/or dry reservoir rocks under small strains (10−8–10−5). We list and discuss important technical aspects to be taken into account when working with these devices or in the course of designing a new one. We also present a summary of the attenuation measurements in reservoir rock samples performed with these apparatuses so far.