Numerical Simulation Of Complex Reservoir Permeability Characteristic

Permeability is a measure of the capacity for fluid movement in porous media or fracture media. Permeability distribution of the reservoir has directly influence on the distribution, the migration and the exploitation of oil and gas, it has an important significance for the exploration and the future exploitation of oil and gas reservoirs. At present, many studies indicate that the seismic response of reservoir includes permeability information. Based on rock physics, this paper analyses the role of permeability on the seismic response of sandstone reservoirs, the objective is to provide effective guidance for predicting the permeability characteristics of reservoir by using seismic data.Based on White’s model with patchy saturation and for three sandstone reservoirs, this paper analyzes the phenomenon of seismic attenuation and velocity dispersion characteristics and the effects of permeability on the seismic attenuation and velocity dispersion characteristics: For three sandstone reservoirs, seismic wave attenuation and velocity dispersion are the most obvious in the unconsolidated sandstone reservoir, the second is the medium consolidated sandstone reservoir, the last is the consolidated sandstone reservoir; Permeability has obvious effects on the seismic wave attenuation and velocity dispersion in the sandstone reservoir, the stronger the permeability, the greater the velocity dispersion and attenuation is; Permeability has effects on the frequency that the peak of attenuation corresponds to and the frequency move to the direction of high frequency with the increase of permeability. For unconsolidated sandstone reservoir, we have studied the different of velocity dispersion and attenuation between the gas-water reservoir and the gas-oil reservoir, the result indicates that the velocity dispersion and attenuation of the gas-oil reservoir is significantly weaker than the gas-water reservoir, but Permeability has obvious effects on the seismic wave attenuation and velocity dispersion in the gas-oil reservoir.Based on Trapeznikova normal-incident reflection coefficient and phase angle equations, we have studied the effects of permeability on reflection coefficient and phase angle characteristics: Permeability has obvious effects on reflection coefficient and phase angle in the sandstone reservoir, especially in the medium consolidated sandstone reservoir, It could lead to phase polarity reversal. Based on Trapeznikova normal-incident reflection coefficient equation, we have deduced the approximate equation of the reflection coefficient frequency gradient and proved that it is the same as the precise equation for Q greater than 10; Permeability has obvious effects on the reflection coefficient frequency gradient in the sandstone reservoir, the stronger the permeability, the stronger the reflection coefficient frequency gradient is; we have analyzed the different sensitivity of 1/Q and the reflection coefficient frequency gradient to permeability in three sandstone reservoirs, the sensitivity of 1/Q and the reflection coefficient frequency gradient is no different for the medium consolidated sandstone reservoir and unconsolidated sandstone reservoir, but for the consolidated sandstone reservoir, the reflection coefficient frequency gradient is more sensitive than 1/Q in the high frequency and low frequency.Numerical simulation of permeability effects on the amplitude of seismic reflection data of the reservoir interface, permeability has obvious effects on the amplitude of seismic reflection data, the top amplitude of the reservoir has obvious attenuation relative to the bot amplitude of the reservoir, the stronger the permeability, the greater the attenuation is. We have analyzed the amplitude spectrum characteristics of the bot of the reservoir, permeability has effects on the main frequency of reflection wave and the frequency move to the direction of low frequency with the increase of permeability. Based on Zoeppritz equation, We have analyzed permeability effects on the AVO characteristics in three sandstone reservoirs, for three sandstone reservoirs, the AVO characteristics are different; permeability has little effects on AVO characteristics, the development trends of AVO don’t change with the permeability; The sensitivity of the reflection coefficient to permeability is influenced by incidence angles, the greater the incidence angle, the more sensitive the reflection coefficient to permeability.In conclusion, the seismic response of reservoir carries permeability information, the reservoir permeability has obvious effects on the velocity dispersion, the attenuation, reflection coefficient and amplitude of seismic reflection data. So the numerical simulation of this paper has effective guidance for predicting the permeability characteristics of reservoir.