Hydraulic and Poroelastic Rock Properties From Oscillating Pore Pressure Experiments

摘要

Knowledge of hydraulic and poroelastic properties is essential for simulating fluid flow in porous media. Accurate constraints on these properties have impacts on production forecasts and economics. In this paper we document an improvement of the oscillating pore pressure experiment by simultaneously measuring hydraulic and poroelastic properties of reservoir rocks. Measurements were carried out for four conventional reservoir rock quality samples at oscillation frequencies of 0.025-1 Hz and effective pressures of 3.5-62 MPa. Estimated permeability values decreased with increasing effective pressure and increased sharply above a frequency range of 0.3-0.4 Hz.We established that hydraulically measured storage capacities are overestimated by almost an order of magnitude when compared to elastically derived ones. Biot coefficient was estimated both from hydraulic and strain measurements, and comparison of two data sets reveals high uncertainty of the hydraulic specific storage measurements.We documented grain crushing and pore collapse event in a dolostone sample, observed as a permanent and drastic decrease of permeability and bulk modulus.We validated our method by detecting irreversible microstructural changes independently by hydraulic, elastic, X-ray microtomography (μCT) and nuclear magnetic resonance (NMR) measurements. Our approach can be used to constrain and to improve the estimation of specific storage and thus leads to better model inputs and forecasts.