Uncertainty Quantification of Two-term Relative Elastic Inversion

It cannot be assumed that rock property relationships that are valid for measured rock properties are also valid for rock property estimates obtained through seismic inversion. The particular case of two term inversion in the intercept-slope domain may result in a systematic shift of rock property relationships. Using methods of Uncertainty Quantification (UQ) it can be shown why this discrepancy exists, and how to correct for it. Clearly this effect will pass through to reservoir uncertainties if not accounted for. The shift in expectations is usually not significant for rock properties related to fluid detection (i.e. Lambda-Rho), but can be very significant for rock properties related to lithology discrimination such as relative Young’s modulus or relative Poisson’s ratio—properties that may be more relevant to unconventionals. It is possible to modify tables of forward rock physics expectations for application to inverted properties. The discrepancy between forward and inverse rock properties can be minimized by inverting to certain two term rock properties rather than AVO intercept and slope.