FIELD GEOMETRY FOR

MULTICHANNEL SEISMIC (MCS) PROFILES

Introduction to Seismic Reflection Imaging: Pt 2

Layouts for (A) a comon-shot gather; (B) a cmmon mid-point gather; and(C) a common receiver gather.

Sequence of survey layouts to acquire a 6-fold coverage; S indicates the source and G a geophone (or hydrophone).

Fold = N/2n whereN = total number of receiver groups;n = number of group intervals moved between shots

Results of common mid-point (CMP) stacks showing improvement in imaging for summations of 6, 18 and 48 shot-receiver pairs.

A. Composite shallow reflection record made up of five separate 12-channel records, each of which was recorded with a different time delay between the shot instant and the start of recording.

B. Corresponding time-distance graph identifying the major seismic events on the record. The optimum window is that range of source-receiver separations that allows the target reflection to be observed without interference from other events.

Example of a common mid-point gather

Some Examples of Shot Gathers

The application of a time-varying gain function to a waveform exhibiting spherical divergence, in order to recover signal amplitudes at later travel times. Gain functions are applied in discrete windows(labelled 1 to 5 as shown).

Types of filters: (A) bandpass; (B) low-cut (high-pass); (C) high-cut (low-pass); (D) notch.

filtered

unfiltered