Seismic Array Response in the Presence of Laterally Varying Thickness of the Weathering Layer

Jubran Akram* and Abdullatif Al-Shuhail**
KFUPM, Saudi Arabia
*[email protected]
**[email protected]

Wavelet response analysis of seismic arrays is a more convenient and direct method of analysis than using their conventional time-harmonic responses. This is because wavelets, rather than sinusoids, are actually generated by the seismic source. This study involves an investigation of the effect of lateral variations in thickness of the weathering layer over the array length on the array response. Three types of variations were studied; namely, dipping-bottom boundary, channel and irregular bottom boundary of the weathering layer. The in-vestigated parameters were the number of elements (12 and 24 elements), the weighting function (equal and triangular), the incident wavelet (Ricker and Klauder) and the error amount. The degradation in the root-mean square (RMS) amplitude responses generally increased with the error amount. RMS amplitude responses were more degraded in the channel case than the other two cases. Errors affected triangularly weighted arrays more than equally weighted arrays. Klauder wavelet array responses were more affected by these errors than Ricker wavelet responses. Vertically traveling waves (i.e. signals) were more affected than the horizontally traveling waves (i.e. noise). Since these variations cannot be inferred from the surface topography, they can affect the array responses without being de-tected, unlike topographic and element’s positional errors. Therefore, it is recommended to test for these effects prior to array layout. Solutions to this problem are to record single-element data and correct these during processing before summing, or to move the array away from the sources of these effects.

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain