The AVO (amplitude variation with offset) technique assesses variations in seismic reflection amplitude with changes in distance between shot points and receivers. AVO analysis allows geophysicists to better assess reservoir rock properties, including porosity, density, lithology and fluid content.
While traditional AVO methods are somewhat mature, GX Technology (GXT) has developed next-generation AVO tools and approaches which extend the utility and application of the technique. A key tool developed by the company is wavelet-based AVO (WAVO). Building off the foundations of AZIM anisotropic processing, WAVO extends applications of the more traditional AVO technique to harder rocks, deeper horizons, thinly-bedded or fractured reservoirs, and areas with low signal-to-noise ratios.
Another limitation of AVO analysis using only P-wave energy is its failure to yield a unique solution. One common misinterpretation is the failure to distinguish a gas-filled reservoir from a reservoir having only partial gas saturation (‘fizz water’). However, AVO analysis using full-wave energy (like that recorded by ION’s VectorSeis sensor) allows geophysicists to differentiate degrees of gas saturation and improve their company’s exploration success rates.
Inversion is a technique that combines surface-acquired seismic data, vertical seismic profiles, and well log data to develop a model of subsurface layers and their thickness, density and P- and S-wave velocities. In essence, it is the method used to “scale down” coarse seismic data to the finer scale of information acquired at the well level (e.g., to well logs). Successful inversion usually requires a high signal-to-noise ratio and recording broad bandwidth data, both of which are key outcomes when VectorSeis single-point sensors are used.
