Interval inversion of well-logging data for objective determination of textural parameters

A joint inversion method for the evaluation of well-logging data is presented, which is applicable to determine textural parameters, i.e., cementation exponent, saturation exponent and tortuosity factor, simultaneously with conventional petrophysical properties. The inversion techniques used today perform local interpretation. Since the number of unknowns is slightly lower than that of the data estimated locally to one depth-point, a set of marginally overdetermined inverse problems has to be solved. For preserving the overdetermination, textural parameters must be kept constant for longer depth intervals (i.e., 200–300 m), despite the fact that they seem to be varying faster with depth according to field experiences. An inversion method was developed, which inverts data of a greater depth interval jointly in a highly overdetermined inversion procedure and gives a better resolution (10 m or less) estimate for the textural parameters. In the paper, a set of inversion tests on synthetic data as well as a field example prove the feasibility of the method.