Browsing by Subject "Poroelasticity"

Now showing 1 - 5 of 5
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    Deformation of fluid-saturated porous rock
    (2013-08) Makhnenko, Roman Yuryevich
    In-situ rock is often fully saturated or at least has a high fluid content. The presence of pore fluid can affect both the elastic response and the inelastic deformation process. However, testing of fluid-saturated rock is not typically performed, even though rock-fluid interaction is critical in many applications, such as oil and natural gas exploration and recovery procedures. Experimental techniques aimed at the measurements of the parameters that govern the deformation of fluid-filled porous rock were developed. Berea sandstone was tested under the limiting conditions of drained, undrained, and unjacketed response. Saturation methods were applied to the rock at pore pressures of 3 - 4 MPa. Hydrostatic loading and compression experiments, both conventional triaxial and plane strain loading, were performed on the sandstone to investigate isotropic and transversely isotropic poroelastic behavior. Measured parameters were used to calibrate a constitutive model that predicts undrained inelastic deformation from the drained response. The experimental data shows good agreement with the model: the effect of dilatant hardening in undrained triaxial and plane strain compression tests under constant mean stress was predicted and observed. Suggested experimental methods can be, and have been already, implemented for testing rock from the field. Moreover, the developed techniques are applicable for the prediction of deformation and induced seismicity in fluid-filled rock utilized for CO2 sequestration.
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    Experimental data on poroelastic moduli of transversely isotropic rock
    (2021-12-25) Tarokh, Ali; Labuz, Joseph F; jlabuz@umn.edu; Labuz, Joseph F; Rock Mechanics Laboratory, Department of Civil, Environmental, and Geo- Engineering, University of Minnesota
    These data present volumetric and deviatoric poroelastic moduli from a series of drained, undrained, and unjacketed tests in uniaxial, hydrostatic, and axisymmetric compression for a porous sandstone. These data enable the direct and independent measurement of all eight parameters that fully describe the mechanical response of a transversely isotropic rock.
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    Fluid-driven fracture in poroelastic medium.
    (2010-02) Kovalyshen, Yevhen
    This research deals with an analysis of the problem of a fluid-driven fracture propagating through a poroelastic medium. Formulation of such model of an hydraulic fracture is at the cross-road of four classical disciplines of engineering mechanics: lubrication theory, filtration theory, fracture mechanics, and poroelasticity, which includes both elasticity and diffusion. The resulting mathematical model consists of a set of non-linear integro-differential history-dependent equations with singular behaviour at the moving fracture front. The main contribution of this research is a detailed study of the large-scale 3D diffusion around the fracture and its associated poroelastic effects on fracture propagation. The study hinges on scaling and asymptotic analyses. To understand the behavior of the solution in the tip region, we study a semi-infinite fracture propagating at a constant velocity. We show that, in contrast to the classical case of the Carter's leak-off model (1D diffusion), the tip region of a finite fracture cannot, in general, be modeled by a semi-infinite fracture when 3D diffusion takes place. Moreover, 3D diffusion does not permit separation of the problem into two regions: the tip and the global fracture. We restrict our study of the fracture propagation to an investigation of two limiting cases: zero viscosity and zero toughness. We show that large-scale 3D diffusion and its associated poroelastic effects can significantly affect the fracture evolution. In particular, we observe a significant increase of the net fracturing fluid pressure compared to the case of 1D diffusion due to the porous medium dilation. Another consequence of 3D diffusion is the possibility of fracture arrest. Indeed, the fracture stops propagating at large time, when the fracturing fluid injection rate is balanced by the leak-off rate at pressure below the critical propagation pressure.
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    Poroelastic response of saturated rock
    (2016-12) Tarokh, Ali
    The existence of fluid in porous medium affects its mechanical response. Changes in pore pressure, defined as the pressure of the fluid contained within the pore space, induces expansion or compaction. Compression of the medium can also raise the pore pressure if the fluid does not have enough time to escape the pore network. These coupled mechanisms add a time-dependent character to the mechanical properties that can be a major concern in many applications, such as oil and gas exploration and recovery. This research is concentrated on determining the poroelastic parameters of fluid-saturated rock, and more specifically, directly measuring the so-called unjacketed pore modulus. Several indirect measurement of this parameter using relevant poroelastic constants have been performed, but limitations of this approach prevent a reliable estimation. Detailed poroelastic experiments, including hydrostatic compression and conventional triaxial compression under limiting conditions of drained, undrained, and unjacketed response are performed on two porous sandstones, Dunnville and Berea, as well as a synthetic silica specimen. The experimental data clearly show that for Dunnville sandstone and synthetic silica, both approximately representing an ideal porous material with a fully connected pore space, the unjacketed pore modulus is indeed equal to the unjacketed bulk modulus. The existence of non-homogeneities such as non-connected pores and compliant minerals in Berea sandstone cause a slight difference between these two moduli. Complete characterization of a transversely isotropic poroelastic behavior of Dunnville sandstone is also presented. The proposed experimental methods along with the results obtained from this research can be implemented for testing rock from the field. Furthermore, the developed techniques are applicable for the prediction of the mechanical response of fluid-filled carbon-capturing rock.