Direct and indirect laboratory measurements of poroelastic properties of two consolidated sandstones

Blöcher, Guido; Reinsch, Thomas; Hassanzadegan, Alireza; Milsch, Harald; Zimmermann, Günter

doi:10.1016/j.ijrmms.2013.08.033

Cited by 65 publications

(58 citation statements)

References 31 publications

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“…Evolution of the normalized porosity with respect to the mean effective stress. The nonlinear behaviour at low effective stress as observed in the experimental data (red line after Blöcher et al, 2014) is well captured by the modelling results which take into account a nonlinear evolution of the elastic moduli resulting from closure of pre-existing micro-cracks and fissures enhanced by compaction of the porous space followed by stiffening of the rock (increase Hertzian contact surface between solid grains).…”

Section: Mathematical Formulation Of the Problemsupporting

confidence: 65%

Flexible parallel implicit modelling of coupled thermal–hydraulic–mechanical processes in fractured rocks

Cacace

Jacquey

2017

Solid Earth

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Abstract. Theory and numerical implementation describing groundwater flow and the transport of heat and solute mass in fully saturated fractured rocks with elasto-plastic mechanical feedbacks are developed. In our formulation, fractures are considered as being of lower dimension than the hosting deformable porous rock and we consider their hydraulic and mechanical apertures as scaling parameters to ensure continuous exchange of fluid mass and energy within the fracturesolid matrix system. The coupled system of equations is implemented in a new simulator code that makes use of a Galerkin finite-element technique. The code builds on a flexible, object-oriented numerical framework (MOOSE, Multiphysics Object Oriented Simulation Environment) which provides an extensive scalable parallel and implicit coupling to solve for the multiphysics problem. The governing equations of groundwater flow, heat and mass transport, and rock deformation are solved in a weak sense (either by classical Newton-Raphson or by free Jacobian inexact NewtonKrylow schemes) on an underlying unstructured mesh. Nonlinear feedbacks among the active processes are enforced by considering evolving fluid and rock properties depending on the thermo-hydro-mechanical state of the system and the local structure, i.e. degree of connectivity, of the fracture system. A suite of applications is presented to illustrate the flexibility and capability of the new simulator to address problems of increasing complexity and occurring at different spatial (from centimetres to tens of kilometres) and temporal scales (from minutes to hundreds of years).

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Section: Mathematical Formulation Of the Problemsupporting

confidence: 65%

Flexible parallel implicit modelling of coupled thermal–hydraulic–mechanical processes in fractured rocks

Cacace

Jacquey

2017

Solid Earth

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“…In case of the B ind inferred from poroelastic theory, the values are lower, ranging between 0.8 and 0.6. In our case, both the direct and indirect measurements fit with the B ind of Blöcher et al []. However, the variations from 0.8 to 0.6 the authors measured were on a water‐saturated sample.…”

Section: Discussionmentioning

confidence: 99%

“…While not much conclusion can be given at this point, it remains of interest to discuss further on the possible bias. Because the authors found a method to measure pore pressure in the rock sample and not in the dead volume, the method of measurement of Blöcher et al [] should be more trusted. It could thus be that the effect of the dead volumes is here underestimated.…”

Section: Discussionmentioning

confidence: 99%

“…It could thus be that the effect of the dead volumes is here underestimated. On the other hand, because Blöcher et al [] use larger amplitudes of pressure variations, it remains possible for their values of B to be overestimated. Indeed, Blöcher et al [] also found both a drained bulk modulus and a skeleton bulk modulus exceedingly small at low P d of about K d =2.22 GPa (i.e., C d =0.45 GPa −1 ) and K s =28.82 GPa (i.e., C s =0.0347 GPa −1 ).…”

Section: Discussionmentioning

confidence: 99%

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New method for measuring compressibility and poroelasticity coefficients in porous and permeable rocks

2017

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Over the last decades, a large understanding has been gained on the elastic properties of rocks. Rocks are, however, porous materials, which properties depend on both response of the bulk material and of the pores. Because in that case both the applied external pressure and the fluid pressure play a role, different poroelasticity coefficients exist. While theoretical relations exist, measuring precisely those different coefficients remains an experimental challenge. Accounting for the different experimental complexities, a new methodology is designed that allows attaining accurately a large set of compressibility and poroelasticity coefficients in porous and permeable rocks. This new method relies on the use of forced confining or pore fluid pressure oscillations. In total, seven independent coefficients have been measured using three different boundary conditions. Because the usual theories predict only four independent coefficients, this overdetermined set of data can be checked against existing thermodynamic relations. Measurements have been performed on a Bentheim sandstone under, water‐ and glycerine‐saturated conditions for different values of confining and pore fluid pressure. Consistently with the poroelasticity theory, the effect of the fluid bulk modulus is observed under undrained conditions but not under drained ones. Using thermodynamic relations, (i) the unjacketed, quartz, and skeleton (Zimmerman's relation) bulk moduli fit, (ii) the drained and undrained properties fit, and (iii) it is directly inferred from the measurements that the pore skeleton compressibility Cϕ is expected to be constant with pressure and to be exceedingly near the bulk skeleton Cs and mineral Cm compressibility coefficients.

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“…An alternative approach for determining the poroelastic coupling parameter is to measure the Biot and Skempton coefficients directly, without measuring static elastic moduli. That is, the fluid mass content can be monitored to obtain Biot's coefficient, and the Skempton coefficient can be measured as the ratio of the induced pore pressure to the change in applied confining pressure for undrained conditions (Hassanzadegan et al, 2012;Blöcher et al, 2014). This has the advantages that no stress-strain measurements are required and the effective velocity ratio can be related directly to the poroelastic coupling parameter.…”

Section: Poroelastic and Dynamic Moduli Of Malm Carbonatementioning

confidence: 99%

Static and Dynamic Moduli of Malm Carbonate: A Poroelastic Correlation

Hassanzadegan

Guerizec

Reinsch

et al. 2016

Pure Appl. Geophys.

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The static and poroelastic moduli of a porous rock, e.g. the drained bulk modulus, can be derived from stress-strain curves in rock mechanical tests and the dynamic moduli, e.g. dynamic Poisson's ratio, can be determined by acoustic velocity and bulk density measurements. As static and dynamic elastic moduli are different a correlation is often required to populate geomechanical models. A novel poroelastic approach is introduced to correlate static and dynamic bulk moduli of outcrop analogues samples, representative of Upper-Malm reservoir rock in the Molasse basin, southwestern Germany. Drained and unjacketed poroelastic experiments were performed at two different temperature levels (30 and 60• C). For correlating the static and dynamic elastic moduli, a drained acoustic velocity ratio is introduced, corresponding to the drained Poisson's ratio in poroelasticity. The strength of poroelastic coupling, i.e. the product of Biot and Skempton coefficients here, was the key parameter. The value of this parameter decreased with increasing effective pressure by about 56% from 0.51 at 3 MPa to 0.22 at 73 MPa. In contrast, the maximum change in Pand S-wave velocities was only 3% in this pressure range. This correlation approach can be used in characterizing underground reservoirs, and can be employed to relate seismicity and geomechanics (seismo-mechanics).

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Direct and indirect laboratory measurements of poroelastic properties of two consolidated sandstones

Cited by 65 publications

References 31 publications

Flexible parallel implicit modelling of coupled thermal–hydraulic–mechanical processes in fractured rocks

Flexible parallel implicit modelling of coupled thermal–hydraulic–mechanical processes in fractured rocks

New method for measuring compressibility and poroelasticity coefficients in porous and permeable rocks

Static and Dynamic Moduli of Malm Carbonate: A Poroelastic Correlation

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