Patent ID: 6477112
Filing Date: 2002-11-05
Classification: G01V

Abstract:
A method of using an acoustic logging tool conveyed in a borehole in a formation for determining a characteristic of the formation, said logging tool having at least one source and a plurality of receivers the method comprising:(a) selecting a depth interval of investigation; (b) identifying a plurality of positions of the at least one source and a subset of associated receivers corresponding to said depth interval and defining a plurality of subarrays associated with said depth interval; (c) for each of said plurality of subarrays, defining a plurality of associated signals; (d) selecting an initial slowness associated with said depth interval; (e) for a selected one of said plurality of subarrays determining a measure of difference between the selected associated signal and an estimated value of the selected associated signal using signals other than the selected associated signal and the slowness, and summing said measures of difference to give a summed measure of difference for the selected associated signal; (f) repeating step (e) for at least one other of the associated signals for the subarray and summing the summed measures of difference to give a mismatch residue for the subarray; wherein both forward and backward shifts are used in determining said estimated values for the at least one or the at least one other associated signal.