Permeability Characterization on Tight Gas Samples Using Pore Pressure Oscillation Method

摘要

For unconventional gas reservoirs, permeability, an important parameter in the subsurface evaluation, is typically low (≤ 10~(-3) mD). While several approaches have been proposed and used, determination of permeability of microdarcy or lower still remains challenging. In a pore pressure oscillation method, the sample is first stabilized at a certain pore pressure, then a small sinusoidal pressure wave is applied to the upstream side of the sample, and the pressure response at the downstream side is recorded. Permeability is deduced from the attenuation and phase shift of the downstream signal. When compared with other methods, this technique greatly reduces the pore pressure variation, increases the measurement sensitivity, and results in more accurate characterization. We have applied this technique in permeability characterization for various reservoirs. The results provided valuable input in subsurface modeling and production forecasting.