Contribution of Poroelasticity to Reservoir Engineering: Lab Experiments, Application to Core Decompression and Implication in HP-HT Reservoirs Depletion

Abstract

The linear mechanics of porous rocks is summarized : basic equations – i.e. constitutive law and fluid mass balance – and most useful relationships are given. For reservoir engineering applications, the hydrostatic loading case is dealt with in detail. The conventional diffusivity equation -i.e. uncoupled pressure equation-is then derived. Experimental procedures are suggested and results obtained on outcrop and reservoir sandstones are given. The data indicate that the sandstones have a nonlinear behavior and that volumetric coefficients are functions of the difference between the confining pressure and the pore pressure. A model is then proposed based on Biot's semilinear theory. The reservoir rock behavior is shown to be in agreement with this model for the experiments performed. As an application effective stress is computed. Finally the role of pore pressure in damaging cores during the pulling out phase is investigated.

Poromechanics: from Linear to Nonlinear Poroelasticity and Poroviscoelasticity

“…Experimental data confirm that the tangent bulk modulus varies according to the pressure difference p c -p p as indicated by Equation (40) (Boutéca et al, 1994). This is illustrated in Figure 9, where estimations of K t o computed from experiment 6 are plotted as a function of the confining pressure for different pore pressure values and as a function of p c -p p .…”

Poroelasticity and damage theory for saturated cracked media

“…In the case of an isotropic linear elastic solid with bulk modulus k'^ we obtain e = -P/3k'l and M = k'. Experimental results on Fontainebleau sandstone are in good agreement with this conclusion (Bouteca et al (1994)). Conversely, if cracks and pores are not connected, the cracks being empty and the pores being saturated, the simultaneous increase of confining pressure and pore pressure will progressively close the cracks.…”

“…The non linearity of the macroscopic elastic properties of rocks under compression has been widely investigated in rock mechanics and particularly in the case of sandstones (Bouteca et al (1994), Zimmermann (1991) and limestones (Lion et al (2005)). During an isotropic compression test, the typical feature is a significant increase of the tangent bulk modulus and the existence of an asymptotic value of the latter, reached at high confining pressures.…”

Mechanical Properties of Rocks: Pore Pressure and Scale Effects

“…To illustrate this, let us consider the experimental data shown in Figure 6 (Boutéca et al, 1994). The drained bulk modulus increases with the confining pressure.…”