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A new methodology for 3D survey design

Seismic Image Software^*, Calgary, Alberta, Canada

Corresponding author: Mike Galbraith, mgalbraith@gedco.com

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

There are two main problems in designing a 3D seismic survey. Firstly, a survey geometry needs to be established that will handle signal correctly—in terms of resolution and amplitude fidelity. Secondly, the same survey geometry must somehow effectively attenuate various types of noise that will be present. The design process described below achieves these two goals (record signal in an optimum way and attenuate noise as much as possible). The process may be applied to any 3D survey regardless of subsurface complexity and survey location. The method is applicable to land, marine, and OBC acquisition. Some example details in this paper (notably, parts of step 9 and all of steps 11–14) pertain more to land and OBC geometries than to marine (parallel) geometries. Nonetheless, steps 11 and 12 still apply to marine geometries with small changes to accommodate the line spacing employed there. The analysis of noise and migration impulse response is just as important to a marine survey as it is to a land survey.

The areal geometries currently employed for some marine 4-C acquisition surveys may also be designed by this method. In this acquisition style, receivers are spaced infrequently (for example, every 400 m) along two orthogonal directions (e.g., two sets of receiver lines) while shots are taken often (e.g., every 50 m) along lines that have the same separation (50 m). Thus, there is a very dense grid of shots and a very sparse grid of receivers. The calculations below for bin size, etc. will be based solely on the inline and crossline shot spacing (which should be equal). The "shot" and "receiver" line spacing calculations (step 9) are based on the inline receiver spacing and the crossline receiver spacing.

There is nothing intrinsically wrong in traditional methods of 3D survey design (Cordsen et al., 2000), . . . [Full Text of this Article]