Objective The Tarim Basin exhibits extensively distributed deep fractured-vuggy carbonate reservoirs. Therefore, determining the seismic and petrophysical characteristics of carbonate reservoirs with a fracture and vug system will provide significant guidance for the exploration, discovery, drilling, and exploitation of favorable reservoirs in the basin. Variations in the filling state of dissolution fractures and vugs will lead to significantly different elastic and attenuation characteristics of the reservoirs.

Methods Based on geological insights into the geometric structural and filling characteristics of the dissolution fracture-vug system in the outcrop sections of carbonate strata in the Tarim Basin, this study proposed a digital rock modeling method for dissolution fracture-vug systems. Guided by physical similarity, this study calculated the dispersion and attenuation characteristics of digital rocks using dynamic stress-strain numerical simulations. Moreover, this study analyzed the wave dispersion and attenuation, as well as the underlying physical mechanisms, varying with the type and volume fraction of vug fillings, the volume fraction of fracture cements, and the gas saturation of fractures and vugs.

Results and Conclusions  Changes in the volume fractions of vug fillings and fracture cements significantly affected the wave velocity and attenuation in the reservoirs. The type of vug fillings produced a more pronounced impact on the wave velocity than the wave attenuation. In the case of varying gas saturation, the wave velocity manifested a monotonic variation trend, while the wave attenuation displayed complex jump characteristics. Wave velocity, as a parameter for characterizing the average properties of the internal structures of digital rocks, exhibited a strong correlation with vug fillings. In contrast, the wave attenuation was highly sensitive to the occurrence state of fluids within local structures of digital rocks. The results of this study can guide the quantitative seismic interpretation, selection of optimal attributes, and velocity modeling for deep fractured-vuggy carbonate reservoirs, supporting the high-precision geophysical characterization of these reservoirs.