Abstract: A computer-implemented method, and system implementing the method, of performing impedance inversion of seismic survey data are disclosed. Sonic and density well logs are used to generate an elastic impedance model, at selected angles of incidence or offset range, using an expression for elastic impedance that depends upon the measured or estimated compressional velocity, shear velocity, and density of the subsurface layers in the survey region. The elastic impedance expression also includes a reference density value, and is dependent upon the ray parameter (or angle of incidence). This elastic impedance model is used, for example by way of a pseudo-density log, in estimating the input wavelet, and in carrying out an impedance inversion of the seismic survey over the entire survey region, for at least two angles of incidence.

Abstract: A computer system and method of operating the same to apply overburden corrections to seismic signals prior to amplitude-versus-offset (AVO) analysis is disclosed. The system and method retrieve common midpoint gathers of the seismic signals, and generate analytical, or complex, AVO intercept and AVO slope traces therefrom, effectively stacking the traces in each gather. Over a sliding time window of the stacks, the computer system generates p-measure standard deviation and correlation statistics, preferably using a p-measure value less than one. The AVO intercept and AVO slope traces are then modified, at each depth point of interest corresponding to a time window placement, according to the relationship between the p-measure statistics and the desired statistics for the background distribution.

Abstract: A method and system for producing an indicator for amplitude-versus-offset (AVO) analysis of seismic survey data is disclosed. According to the disclosed method and system, a raw AVO indicator is generated for each of multiple depth points, from the AVO intercept and gradient coefficient values. The indicator is generally a positive amplitude number for those locations having petrophysical importance, while the background neighboring points will have a zero or negative value for the raw indicator. Statistics are derived for a group of depth points that surround the depth point under analysis, in time and in space, from which a probability function may be evaluated, assuming a distribution of values in the background trend of AVO intercept and gradient values, and based upon which the raw AVO indicator will be modified. In one embodiment, the probability function is evaluated to determine the loci of points that are within the background to a certain statistical confidence.