FAULT POPULATION DESCRIPTION AND PREDICTION USING EXAMPLES FROM THE OFFSHORE UK

Three-dimensional seismic interpretation and well-core data were analy sed to characterize the fault populations in two offshore U.K. hydroca rbon fields. Comparison of multiline fault-throw samples from seismic- scale faults with displacement samples, measured on well-core fracture s, shows that the displacement population is described by a power law. Faults seen in core and on seismic data are consistent with one anoth er and appear to belong to the same continuous population;therefore th e number of intermediate-scale faults can be predicted. Fault lengths are much more difficult to measure due to resolution effects and the s ize 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 fra cture sets have been analysed in terms of their spacing, which also ap pears to be described by a power law and is clearly distinguishable fr om regular spacing. Comparison of core-scale fracture orientations wit h seismically-mapped faults shows that the two have similar azimuth di stributions. Subsurface data, either well core or seismic, is particul arly amenable to analysis by one-dimensional sampling.