Abstract

Statics play an important role in land seismic processing. They affect velocity analysis, reflection continuity, resolution and apparent structure.

When statics supplied from the field are inadequate, refraction statics are necessary to rectify the problem. Inadequacy of the field statics could be due to various field conditions such as shot-depth, fast lateral changes in weathered layer thickness and velocity, the inherent limitations of the uphole method and so on.

The key to successfully resolving these problems in applying any refraction statics program is to properly pick the first breaks coming from refracted raypaths, then build a near-surface model to calculate vertical transit time.

Various techniques from various processing companies are used in picking the first breaks. These range from enhancing the first breaks display to interactive computer-aided picking.

In building near-surface models many methods are used. Some programs build a simple one layer model while other programs can create and handle more complex models. Accuracy in determining both weathered layer and refractor velocities has a considerable influence on the statics computations.

This paper details the results of processing a line with known significant statics problems using several contractors.