Method for quantitatively making a thickness estimate of thin geological layers based on seismic reflection signals in the frequency domain

A method for quantitatively estimating a thickness of a buried geological layer, comprising the steps of:

• using a seismic source having a source wavelet spectrum;
• registering a seismic trace of reflection time domain data (5t);
• selecting a temporal interval (t1, t2) of said trace of seismic reflection data (5t) producing a time interval series of seismic reflection data (5ts) for which a thickness (Δt or d) of said layer (L) in said temporal interval is to be determined;
• transforming said time interval reflection data (5ts) into a seismic interval frequency spectrum (5f);
• and
• repeating the following steps for a number of temporal thicknesses (Δt):
• forming a model reflectivity spectrum (Lmf) representing a current temporal thickness (Δt) of a reflectivity function (Lmt);
• multiplying said model reflectivity spectrum (Lmf) with said source wavelet spectrum (3f), producing a thin layer model spectrum (Lms);
• correlating said thin layer model spectrum (Lms) with said seismic interval frequency spectrum (5f) producing a (single) correlation value (C(Δt)) as function of the instant temporal thickness (Δt);
• and
• selecting a peak value (Chigh) in the so produced series of correlation values (C(Δt)) as function of the instant temporal thickness (C(Δt)), and letting the temporal thickness (Δt) corresponding to said peak value (Chigh) indicate a thickness estimate (Lm) of said buried geological layer.