Resolution within seismic imaging must be understood in all three dimensions to make quantitative approximations of subsurface geometries. Constructive interference of incident spherical waves within the first Fresnel zone will limit the resolution due to spatial aliasing. Motivated by the problem of estimating the influence of this effect on the volume uncertainty several interpretations of trapping faults, being equally probable within the first Fresnel zone, are perturbed and multiple realizations of a structural model constructed. After estimating the depth dependent mean frequency and velocity within a zone around the fault plane, the fault interpretations are stochastically perturbed. The frequency- and velocity-dependent perturbations of the dips are analytically derived based on geometric considerations. The anticipated maxima of the repositioned fault dips specify thresholds for deterministic definitions of high and low cases for the fault geometries in a framework. The structural models, resulting from repositioning the faults, show significant alterations of the hanging-wall and footwall horizon terminations due to the varying dips and repositioning of the interpretation. We have applied our to the structural and stratigraphic interpretation obtained for a prospect in the Gulf of Mexico. The spatial variations of the bounding faults result in a spread of volumetric outcomes when analyzing the gross rock volume of the compartment.
In a reservoir, faults at the limit of the seismic resolution can be crucial to explain production history and to optimize field development. However, in most cases the detail required to describe such subtle features depends on the assistance of seismic attributes and semi-automated interpretation techniques. We generated a detailed description of the fault network in the South Arne Chalk Group using a workflow based on a globally consistent computation of the seismic dip. This led to more accurate seismic edge attributes than gained with standard dip estimation techniques. We analysed each fault set and qualitatively assessed its control on fluid flow. Our investigation suggests that the two fracture sets that influence production developed along the same WNW-ESE structural trend and cannot be separated based on the seismic data alone. These faults were active both during and post Chalk deposition. We observe ENE -WSW lineaments that match the pattern of a time-lapse seismic amplitude anomaly associated with water injection. It remains to be verified whether these lineaments could be an extension of overburden faults, as well as whether the increased intensity of the fault network as seen on the 2005 v. the 1995 3D seismic survey was caused by production effects.
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