Prediction of calcareous sandstone based on simultaneous broadband nonlinear inversion of Young's modulus, Poisson's ratio and S-wave modulus

Abstract

The oilfield's further fine development is significantly impacted by the interlayer of calcareous sandstone. Projecting the lateral distribution of subterranean calcareous sandstone is crucial for determining sequence boundary division, reservoir quality, and even CO₂ storage. Research on the sensitive characteristics of calcareous sandstone is still lacking. This study computes the percentage of lithologic difference and performs an intersection analysis of rock physical properties. It is found that Young's impedance, Poisson's ratio, and S-wave modulus have pleasurable sensitivity to distinguish calcareous sandstone. On the basis of this, a new sensitive factor for calcareous sandstone was built. The traditional approximate YPD reflection coefficient equation is only applicable to the weak contrast interface, and the accuracy is limited. This difficulty is solved in this paper by deriving a new equation for the nonlinear reflection coefficient. The equation is expressed by Young's modulus, Poisson's ratio, S-wave modulus, and density. Finally, the broadband nonlinear inversion method is adopted to provide a reasonable low-frequency model for the inversion of parameters. This allows for the realization of a stable inversion of parameters. The simultaneous broadband nonlinear inversion of Young's modulus, Poisson's ratio, and S-wave modulus provides a novel approach for calcareous sandstone prediction. We tested the accuracy and rationality of the method with both synthetic and field data examples.