1Iterative method for the separation of blended seismic data discussion on the a

Geophysical Prospecting, 2012, 60, 782–801

doi: 10.1111/j.1365-2478.2012.01084.x

Iterative method for the separation of blended seismic data: discussion on the algorithmic aspects

Araz Mahdad , Panagiotis Doulgeris and Gerrit Blacquiere` Delft University of Technology, Geotechnology Department, Section of applied geophysics and petrophysics, Stevinweg 1, PO-Box 5048, 2628 CN Delft, The Netherlands. Received Jun 2011, revision accepted March 2012 A B S T R A C T

Recently much attention has been given to the possibility of shooting in an overlapping

fashion, the so-called blended or simultaneous acquisition. In conventional acquisition the

time intervals between successive sources are large enough to avoid interference in time.

In blending, a temporal overlap between source responses is allowed. This additional

degree of freedom in survey design has the potential to significantly reduce seismic

acquisition costs while maintaining or improving the data quality. Deblending is the

procedure of retrieving data as if they were acquired in the conventional, unblended way.

This is an essential step in the case where standard processing flows are applied. Several

methods have been proposed to perform data separation with the majority of them falling

into two categories. The first category consists in methods that filter out the blending

noise by arranging seismic data in some domain, whereas inversion techniques fall into

the second category. We recently introduced an iterative estimation and subtraction

algorithm that integrates elements of both categories. This method exploits the fact that

the character of the blending noise differs in different domains, e.g., it is coherent in the

common source domain but incoherent in the common receiver, common-offset or

common midpoint domains. Up to now, our method relies on the interaction with a

human operator. The automation of the thresholding process is addressed in this paper,

leading to a hands-off algorithm for the separation of blended data, optimized for both

efficiency and effectiveness. We found that one of the major limiting factors is the edge

artefacts generated by the coherence-pass filter. The effectiveness of the coherence-pass

filter has a considerable influence on the convergence of our deblending algorithm. This

is shown by testing different coherence-pass filters on marine data as well as introducing

errors in the coherence-pass process. We show that these data estimation errors can be

handled properly and the best result is obtained using a τ -p filter as a coherence-pass

filter. Furthermore, very promising results are obtained on numerically-blended land data.

I N T R O D U C T I O N Key words: Deblending, Thresholding, Coherence-pass filter.

Several authors have discussed the concept of simultaneous shooting for impulsive and vibroseis type sources as well as

E-mail: a.mahdad@tudelft.nl their particular advantages. Methods to utilize more than one source simultaneously in the field have been taken into con-sideration for a long time in land surveys. The use of simul-taneous vibrators transmitting the same or different reference signals was proposed by Silverman (1979). The High Fidelity Vibratory Seismic (HFVS) method was developed by Sallas,

782 C 2012 European Association of Geoscientists & Engineers

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