In seismic data acquisition, the industry is facing a challenge to extend the implementation of temporal sampling principles to the spatial domain as the initial sampling interval in space impacts operational efficiency and is constrained by the availability of a sufficient number of sensors and the capacity and dynamic range of the recording instruments in addition to cost considerations. The use of single-sensor seismic acquisition has the potential to solve the aliasing problems associated with inadequate special sampling. This paper presents the reasoning behind conducting single-sensor 3D seismic surveys in onshore Kuwait and the quality of the results obtained.
The seismic wavefield arriving to the surface is the net result of all distortions affecting the wavefield during its travel in the subsurface. This wavefield, ideally, should be properly sampled temporally and spatially in the receiver, source, offset and CDP domains. In 3D conventional land data acquisition, the wavefield arriving to the surface is only sampled at its intersections with receivers configured in an array. Marschall (1999) defined nominal 3D full fold acquisition in 3D land acquisition as the case in which the surface acquisition template consists of square grids. An active receiver is located at each grid point within a square with side-length equal to a single receiver line and the source at the center. Roll-along in x- and y-directions is with increment of one grid point. This scheme is intended to be the theoretical reference against which other schemes are to be evaluated. Ongkiehong et al. (1988) defined universal land acquisition as a scheme in which we are not forced to commit to a final processing and/or interpretation sampling grid during the acquisition process, but have the ability to change the processing/interpretation bin dimensions at various later times and called this “uncommitted acquisition”, i.e., in the field no irreversible step should be carried out such as group forming by conventional arrays. Several other authors have also discussed issues relating to acquisition to better sample the seismic wavefield and improve data resolution. Conventional land 3D seismic using arrays acquired in Kuwait had shot and receiver arrays having a length of 50m. Consequently, the surface spatial sampling interval is equal to this length. Such array forming in the field by straight analog summation provides suboptimal performance in signal preservation and in antialias filtering. Their responses are distorted by the presence of intra-array perturbations and seismic data quality is adversely affected. Residual ground-roll will alias and consequently will not be effectively removed in processing. Intra-array perturbations are differences in amplitude, phase and timing between the different elements of an array. Intra-group statics, coupling, amplitude and phase variations, near-surface inhomogeneities, geophone sensitivity, dead sensors, polarity reversals, irregular spatial sampling, position errors, etc. cause these differences.
Single-sensor seismic data acquisition has the potential to achieve 3D full fold uncommitted land seismic, which can reduce the above-mentioned perturbations and solve the aliasing problems associated with inadequate special sampling and consequently improve the quality of seismic data.
