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Target-oriented adaptive subtraction in data-driven multiple removal

PGS Geophysical, Walton-on-Thames, England

Corresponding author: Roald.van.Borselen@pgs.com

The first 20% of the full text of this article appears below.

Data-driven multiple removal methods have proven a valuable addition to the demultiple toolbox for three main reasons. Firstly, such methods do not make use of any a priori information about the subsurface geology and, therefore, such information cannot bias the solutions. Secondly, data-driven methods can be applied in either 1D, 2D, or 3D mode and can therefore account for the full, multidimensional complexity of the earth. Finally, because no a priori information is used, the required user interaction is minimized. These methods are now applied in production-style processing environments with comparable speed and turn-around as conventional techniques.

In general, data-driven multiple removal is accomplished in two steps. First, multiples are predicted through convolutions of preprocessed common-shot and common-receiver gathers in time and space. Subsequently, the predicted multiples are subtracted from the input data using the minimum energy criterion, which states that the total energy after subtraction of the multiples should be minimized. Using adaptive subtraction techniques, the predicted multiples are removed by designing Wiener filters in overlapping windows. In general, this works well. However, when the set of predicted multiples is complex, the "standard" implementation may fail, because no filter can be found that subtracts all predicted multiples in an optimal manner. In this article, an approach is discussed that allows for constrained adaptive subtraction, where multiples are discriminated from other multiples based on frequency and/or dip. The method is illustrated with two marine field data examples.

	Background

 
The aim of data-driven multiple elimination methods is to remove all multiples that have been generated by either the free-surface or internal boundaries. Many authors have described ways to arrive at the same integral equation for the multiple-free pressure wavefield in terms of the multiple-contaminated measured pressure wavefield. In all formulations, the source wavelet must be known to solve the pertinent integral equation. . . . [Full Text of this Article]