Noise Reduction

Time-lapse (4D) acquisition

Shallow source and streamer configurations generally require good seastate conditions to avoid excessive noise. WesternGeco has developed a data-adaptive noise cancellation technique (LACONA) in conjunction with Q-Marine point-receiver technology. As seen in the following examples, the fine spatial sampling allows the noise to be sufficiently well sampled for attenuation during digital group forming (DGF). Thus, noise attenuation is achieved with preservation of low frequencies that are otherwise removed by high-pass filtering. The output is also free from array response effects and high frequencies are preserved.

Point receivers also remove the filtering effect introduced by receiver arrays. Such filtering effects are common to all conventional streamer systems where non-vertical arrivals are subjected to attenuation of high frequencies. Point receivers thus provide a more accurate AVO response.

Point receivers spaced at 3.125 m also allow for finer sampling of the wavefield. Finer sampling means less noise due to aliasing introduced during, for instance, Tau-p or parabolic Radon transforms in processing.