Velocity Prediction and Secondary-pores Quantitative Inversion for Complex Carbonate Reservoir

Abstract

Dissolved caves, holes, and cracks are the main secondary pore types for carbonate reservoirs in Tarim Basin. Velocities of elastic wave propagating in this kind of complex reservoirs change enormously for different secondary pore shapes. Based on Berryman’s differential effective medium (DEM) model and Gassmann’s equation, a rock physics model for complex carbonate reservoirs is established by modeling geometrical shapes of different secondary pores. This model is employed to predict the P- and S-wave velocities of carbonate reservoirs in Tarim Basin. The predicted results are consistent well with the measured data, proving the practicality of the rock physics model on velocity prediction for complex carbonate reservoirs. Additionally, an idea is proposed to quantitatively invert the secondary pores by inversely employing the rock physics model. The feasibility of this idea and the rationality of the inversion results are proven by the consistence between the inverted secondary pore types and those indicated in FMI data.