As an unconventional method, low-frequency vibration production technology is applied for oil recovery enhancement in amounts of oil fields. Petro-physic properties in seepage fluid-saturated porous media with are revealed to be influenced seriously by elastic wave in substantial researches. With an assumption of static fluid-saturated, porosity variation equation in Biot’s model is not appropriate to interpret the percolating in low-frequency vibration production technology, there exists an obvious error from the actual experimental data. Based on the function mechanisms and factors controlling the porosity in seepage fluid-saturated porous media, a modified model of porosity variation under vibration is developed to improve the accuracy. Different coefficients for porosity increase are derived. The factors include the compaction of matrix and fluid, proportion of seepage interconnected pores, change of adhesive layer in capillary tube as well as transport of particle under vibration. Furthermore, a comparison with experimental result in artificial sandstone cores is carried out to verify the validity. An error of about 4–21?% is reduced by the modified porosity variation compared with that in Biot’s model. As a critical basis of wave equation, the modified porosity is helpful to illustrate the concrete change of percolation in low-frequency vibration production technology.
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