How to deal with Near-Surface imprint during the land data processing?
IPGP - Îlot Cuvier
Séminaires Géosciences Marines
David Le Meur
From the expectations expressed by oil&gas companies CGGVeritas puts in place since several years an innovative scenario to acquire and process dense Wide-Azimuth surveys. Near surface anomalies are at the root of all of the problems associated with land seismic data (weathering, bogs, swamps, limestone outcrops, rapid changes in elevations, sabkras, dunes, wadis...). The objective of this presentation is to give a general survey of our technical capabilities handling near-surface effects responsible for this loss of resolution. Our latest techniques to separate Surface Waves from the input data (called Groundroll or Guided waves) as well as cross-talk noises due to blended source acquisition are presented. Near-surface anomalies also generated amplitudes, time shifts and wavelet distortions that should be corrected in a surface-consistent way. Usually, First Arrival Traveltime Tomography is presented as a valuable tool for deriving refraction static corrections. Moreover amplitude decay and frequency dependant time varying effect are now handled via a Simultaneous Joint Inversion amplitude/deconvolution. Time shifts are computed using a non-linear approach in order to estimate residual statics. These new tools allow processing modern 3D Wide-Azimuth surveys in a reasonable time schedule with the highest quality industrial standard.