Patent ID: 6028821
Filing Date: 2000-02-22
Classification: G01V

Abstract:
A method for separating waves propagating in a medium, said method comprising:generating waves in the medium successively from several positions of at least one source which are located at the surface of said medium,receiving said waves at at least one receiver that can successively occupy at least two positions in a borehole drilled in the medium, each receiver comprising three sensors which are oriented in a first system of axes (V, H.sub.1, H.sub.2), one of said axes (V) being oriented in a specified direction, each sensor delivering a signal which is recorded as a function of time in the form of a trace which is identified by the positions of a source/receiver pair that produced said trace,forming collections of traces (C) from a common source (z, t) said method further comprising,a) extracting first C signal arrivals of at least one of the C trace collections,b) generating, on the basis of said at least one C trace collection, initial data comprising a collection of residual C traces in which each residual trace is a difference between the C trace and a C signal estimate,c) selecting, from the collection of residual C traces, a pivot trace located at a focus depth z,d) plotting a straight line of variable slope p at each sampled point of the pivot trace,e) forming, along said straight line, for each value of p, amplitude sums by summing amplitudes of seismic events located at intersections of the traces with said straight line,f) transferring the amplitude sums for the corresponding time and slope into data in a domain (.tau., p) in which p represents values of said slope and .tau. represents time,g) making a synthetic seismogram on the basis of the data in said domain (.tau., p),h) comparing the synthetic seismogram with the common source collection of residual C traces, andi) performing iterations of the extracting to comparing steps until the synthetic seismogram is acceptable in terms of the initial data of said common source collection of residual C traces.