Calculation and analysis of frequency-dependent azimuthal AVO response in vertically orthogonally fractured reservoirs
In the exploration and development of unconventional oil and gas reservoirs,it is crucial to describe fracture parameters and hydrocarbon saturation.In these unconventional reservoirs,the fracture systems are fundamental in controlling oil and gas transport.To accurately describe the properties of fractured reservoirs,we constructed a frequency-dependent rock physics model based on the Chapman multi-set fracture rock physics theory.This model includes two sets of vertically orthogonal fractures.And we quantitatively analyzed the influence of porosity,fracture density and fracture size on the frequency-dependent anisotropic characteristics of oil-saturated fractured reservoirs.In addition,using the anisotropic reflectivity method,we studied the frequency-dependent azimuthal AVO response characteristics of vertically orthogonal fractured sandstone reservoirs under different conditions of porosity,fracture parameters,and thin-layer thickness.The results indicate that in a single-interface reflection model,the reflection coefficient of the PP wave is more sensitive to porosity and fracture parameters at the low frequencies.The Changes of porosity and fracture size significantly affect the frequency-dependent AVO characteristics of the reflected PP wave.In the thin-layer reflection model,there is a positive correlation between thin-layer thickness and frequency-dependent effects.This study provides a foundation for the frequency-dependent analysis of complex anisotropic fractured reservoirs and aims to improve the accuracy of quantitative predictions for unconventional oil and gas reservoirs.
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