Patent Document ID: 20020188406
Application ID: 10133591
Patent Flag: 0

Claim One:
1 ) A method for facilitating identification of changes occurring, in the course of time, in the physical state of a first zone of an underground formation, from changes detectable within a first time window on several sets of seismic traces respectively obtained during successive seismic surveys, by taking account of uncertainties on a certain number of descriptive seismic attributes, by reference to parts of said traces of the various sets recorded in at least a second time window corresponding to at least a second zone of the underground formation where said formation undergoes no significant physical state variation during the successive seismic surveys, wherein a discriminant analysis technique is used to classify seismic events located on the record traces into defined categories, the method comprising: forming a learning base comprising physical states that have already been recognized and classified into predetermined categories, each one being defined by attributes of known statistical characteristics, constructing, by reference to the learning base, a classification function using a discriminant analysis technique, allowing to distribute in said categories the various seismic events to be classified from available measurements on a certain number of attributes, this function being formed by determining the probabilities of belonging of the events to the various categories by taking account of uncertainties on the attributes in form of probability intervals of variable width, and assigning each seismic event to at least one of the predetermined categories according to the width of the probability intervals, the method being characterised in that said uncertainties involved in the construction of the classification function are uncertainties expressing the lack of reproducibility of the seismic attributes from one seismic survey to the next, which are obtained by statistical analysis of the attribute variations of the seismic events of the second time window.