Abstract

Shooting medium is one of the key elements and impacts directly the data quality in land seismic data acquisition. In course of acquiring long offset (~6.0 Km.) 2D seismic data in Wamaj low area of Cambay Basin, characteristic difference in quality of monitor records was observed due to change in shooting layer. These shooting layers appear to have similar velocity, uphole pulse attributes and lithology, along a part of a seismic profile. These layers however show characteristic difference in signal energy (layer wise) and the relative difference continues to be seen even if velocity in a layer laterally grades down (2000m/s to 1000 m/s). This suggests that the decision of shooting medium is to be made based on energy transmission characteristics rather than based on high velocity and uphole pulse. This can be achieved by analyzing data quality from check shots in different layers. Lateral extent of shooting medium thus found suitable should be tested inspite of velocity grading down considerably. In areas having significant near surface velocity variations, correlation of shooting medium over an area and following it up with the help of check shots will result in better quality data.