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7th Middle East Geosciences Conference and Exhibition
Manama, Bahrain
March 27-29, 2006
Noise
within Seismic Arrays of Variable Geophone
Density
Exploration Operations Department/Geophysical Data Acquisition Division, Saudi Aramco, P. O. Box # 9370, Dhahran 31311 Saudi Arabia,
phone: 00966505859020, fax: 0096638738949, [email protected]
The behavior of surface noise
within seismic arrays of variable geophone density was investigated by means of recording a
dense grid of single geophones. Common single geophone gathers were generated and processed in order to separate the
seismic signal from non organized
noise
present in the data. Arrays with variable geophone densities were subsequently
simulated from the common single geophone gathers. The non-organized
noise
was evaluated as the residual RMS
amplitude of the simulated geophone gathers after separating the signal.
The result confirms the existence of spatial correlation of non-organized noise
manifested by decreasing array efficiency
attenuating the
noise
beyond a certain intra-geophone distance.
The effect
is visible over the full seismic bandwidth but is frequency dependent and more pronounced with decreasing
frequencies of the non-organized
noise
. At lower frequencies, the spatial correlation of the non-organized
noise
will
manifest itself as a deviation from the square root law at relative larger intra-geophone distances.
The resulting relationships between bandwidth, intra-array geophone distance and non-organized noise
attenuation suggest
a maximum useful geophone density of seismic arrays. Using these relationships may yield a better signal -to-
noise
ratio
and a more efficient use of the field equipment, a main contributor to the overall cost of present day seismic surveys.