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A world of reality—Designing land 3D programs for signal, noise, and prestack migration—Part 2

Mustagh Resources, Calgary, Alberta, Canada

Corresponding author: ncooper@mustagh.com

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

This article is the continuation of a two-part tutorial. The first part (October, 2004) reviewed methods of estimating signal and understanding noise in a given project area, discussed the concepts of trace density and statistical diversity, and addressed concepts in prestack migration. This part begins with a brief discussion of the merits of various model types, which will lead to a discussion of robustness during implementation. The tutorial concludes by suggesting a data simulation method to evaluate the characteristics of a survey design.

	3D model types

 
Much discussion about survey design has focused around the potential advantages of different survey geometries or model types (orthogonals, staggered orthogonals, bricks, diagonals, etc.). When compared using fixed source and receiver densities, Cooper and Herrera (2002) found very little difference amongst many of these variations. By focusing on limited statistics (for example nearest contributing offset in each bin), differences can be presented that favor some designs over others. However, when other statistics are presented (for example, the gap from nearest to second nearest offsets) the preferences often reverse.

I have attempted to study the various common models using more generalized statistics as well as data simulations. The model types were divided into two classes: orthogonal designs (rigid orthogonal, offset orthogonal and staggered orthogonal) and diagonal designs (double brick, triple brick, skewed diagonals, rotated diagonals). I concluded that there were some clear benefits within each category. The staggered orthogonal design showed less bin-to-bin erratic behavior (refer to the offset homogeneity histograms at the top of Figure 14 and the azimuth homogeneity histograms at the top of Figure 15). Similarly, the 26.56° skewed diagonal design exhibited somewhat better statistics than related brick patterns, but the differences between the best of the orthogonal class (the staggered orthogonal) and the best of the diagonal class (the 26.56° skewed) were very . . . [Full Text of this Article]