| Popis: |
Summary The paper is devoted to several variants of geometric 3-D inversions of EM data with finding the parameters of conductivity and chargeability of a geolelectrical model. The first variant is based on two-stage 3-D inversion, at the first stage of which, the 3-D conductivity structure is recovered with separating the signals of EM and IP fields. At the second stage (of the first variant), the chargeability parameters are recovered with the use of residual signals obtained as subtraction of EM signals, which are computed for the conductivity model obtained at the first stage, from the observed data. In the second variant of 3-D inversion, we perform the simultaneous search of conductivity and chargeability distributions and, if it is necessary, the parameters of decay function. In both variants, the block structures are used for the initial model parameterization, and the vector of parameters includes x-coordinates of borders between the blocks, y-coordinates of borders between the rows of blocks as well as the electro physical parameters within the blocks. The workability of both approaches is demonstrated on the synthetic data for the 3-D geoelectrical model, which is constructed on the basis of the 3-D inversion results of DNME-data obtained on one of the North Pre-Caspian oil fields. |
