Method for processing the lapse measurements

Abstract

Resistivity data acquired at two different epochs using different types of tools are jointly inverted. For example, a multiple propagation resistivity (MPR) tool is run first, preferably at several frequencies and several transmitter-receiver spacings. At a later epoch, an induction tool may be run, preferably on a wireline. The joint inversion process identifies bed boundaries based on inflection points in the propagation resistivity and induction logging raw data. An initial guess for an uninvaded earth model is generated using the selected bed boundaries and the apparent raw resistivity values. An inversion run using shallow measurements of propagation resistivity logging data is performed to estimate a resistivity structure representative of the near borehole zone resistivity (invaded zone). The bed boundary positions of the layers are also updated as part of the inversion process. Synthetic data for both the shallow and deep measurements are generated to delineate the invasion zones. If the data match is good for both shallow and deep subarrays, then the model obtained from the shallow data is used as the final model for the inversion. In the event the data match is good for short subarrays and not for long subarrays, a final inversion run is performed by introducing invasion in the earth model. The method may be used for inverting data obtained from wireline, MWD or permanently implanted sensors at two or more epochs.