Fault population description and prediction using examples from the offshore U.K.

Three-dimensional seismic interpretation and well-core data were analysed to characterize the fault populations in two offshore U.K. hydrocarbon fields. Comparison of multiline fault-throw samples from seismic-scale faults with displacement samples, measured on well-core fractures, shows that the displacement population is described by a power law. Faults seen in core and on seismic data are consistent with one another and appear to belong to the same continuous population; therefore the number of intermediate-scale faults can be predicted. Fault lengths are much more difficult to measure due to resolution effects and the size of the sampling area. Fault linkage also introduces some problems, as it may prove difficult to determine which splay should be included in the length measurement when faults branch. Well-core fault and fracture sets have been analysed in terms of their spacing, which also appears to be described by a power law and is clearly distinguishable from regular spacing. Comparison of core-scale fracture orientations with seismically-mapped faults shows that the two have similar azimuth distributions. Subsurface data, either well core or seismic, is particularly amenable to analysis by one-dimensional sampling.