Analysis of oscillatory fluid flow through rock samples

Abstract

S U M M A R YOscillatory hydraulic tests were conducted on samples of two varieties of Fontainebleau sandstone differing in porosity and a stacked sample of the two varieties. Simultaneous measurements of the upstream and downstream pressures and the upstream fluid flow permit the calculation of permeability and specific storage by two methods, the conventional upstreamdownstream pressure analysis and the upstream pressure-flow analysis. The pressure analysis yields a relatively constant permeability for the high-porosity sample at different effective pressures and oscillation periods, but slightly period-dependent permeability for the low-porosity samples and the stacked sample. The period dependence diminishes with increasing period. Estimates of specific storage capacity derived from pressure analysis appear problematic. For samples with the higher porosity, values are highly uncertain due to peculiarities of the solution space used to convert attenuation and phase shift to permeability and storage capacity. For the sample with the lower porosity and the stacked sample, normalized storage capacity values fall significantly below the physical limit constituted by sample porosity. The flow analysis yields well-constrained values of permeability and specific storage capacity for the sample with the higher porosity. For the samples with the lower porosity and the stacked sample, both parameters show a strong dependence on oscillation period. We suppose that the two methods probe different portions of the pore space and thus yield different results for heterogeneous samples when periods fall below a critical period estimated from the scaling relation for hydraulic diffusivity. Flow analysis probes the portion of the sample facing the upstream reservoir with a thickness approximated by the penetration depth. In contrast, the pressure analysis probes the dominant flow path connecting the sample ends. In samples with connected but stagnant pores, the storage capacity has two distinct contributions from an effectively storing porosity and an effectively conducting porosity. The observed period dependence of storage capacity probably reflects the shift in balance between the two contributors.

Influence of Normal and Shear Stress on the Hydraulic Transmissivity of Thin Cracks in a Tight Quartz Sandstone, a Granite, and a Shale

“…When permeability is low, however, a long time may be required to establish a steady state; therefore, a transient flow method is commonly employed, such as the pulse transient decay method (Brace et al, 1968) or the oscillating pore pressure method (Bernabé et al, 2006;Faulkner & Rutter, 2000;Fischer, 1992;Kranz et al, 1990;Song & Renner, 2007). Both of these latter methods have been used in the present study.…”

“…In these cases the pressure pulse transient decay method (Brace et al, 1968;Cui et al, 2009) or the oscillating pore pressure method (Bernabé et al, 2006;Faulkner & Rutter, 2000;Fischer, 1992;Kranz et al, 1990;Song & Renner, 2007) must be employed. In the steady state flow method the mass of fluid in the pore spaces…”

Changes in Electrokinetic Coupling Coefficients of Granite under Triaxial Deformation

“…To measure the permeability continuously during the deformation experiments [35], we adopted the sinusoidal oscillation method [36][37][38][39]. The method is based on the measurement of an attenuation and a phase retardation of an oscillation of the pore-fluid pressure as it propagates through the specimen.…”

Theoretical Analysis of One-Dimensional Pressure Diffusion from a Constant Upstream Pressure to a Constant Downstream Storage

“…(2)), a number of techniques have been proposed to simultaneously determine the hydraulic properties of rock samples by solving the diffusion equation with various boundary conditions. The name of each method is taken from the boundary condition; for example, pulse-transient (HSIEH et al 1981;SONG et al 2013), pore-pressure oscillation (FISCHER 1992;BERNABÉ et al 2006;SONG and RENNER 2007), constant flow rate (MORIN and OLSEN 1987;SONG et al 2004), and linear pressurization (SONG and RENNER 2006, 2008. Of these approaches, only the pulse-transient method uses the transient pressure curve; however, this method involves complicated curve-fitting procedures (SONG et al 2013).…”