Integrating 3-D seismic data, field analogs, and mechanical models in the analysis of segmented normal faults in the Wytch Farm oil field, southern England, United Kingdom

We propose a methodology for the analysis of normal fault geometries in thr ee-dimensional (3-D) seismic data sets to provide insights into the evoluti on of segmented normal fault systems and to improve recovery efforts in fau lt-controlled oil fields. Limited seismic resolution can obscure subtle fau lt characteristics such as segmentation and gaps in fault continuity that a re significant for oil migration and thus accurate reservoir characterizati on. Detailed seismic data analyses that incorporate principles of normal fa ult mechanics, however, can reveal evidence of fault segmentation. We integ rate seismic attribute analyses, outcrop analog observations, and numerical models of fault slip and displacement fields to augment the use of 3-D sei smic data for fault interpretation. We applied these techniques to the Wytc h Farm oil held in southern England, resulting in the recognition of signif icant lateral and, to a lesser extent, vertical segmentation of reservoir-s cale faults. Slip maxima on fault surfaces indicate two unambiguous segment nucleation depths, controlled by the lithological heterogeneity of the fau lted section. Faults initiated preferentially in brittle sandstone and lime stone units. Subsequent growth and linkage of segments, predominantly in th e lateral direction, resulted in composite fault surfaces that have long la teral dimensions and multiple slip maxima. Reservoir compartmentalization i s greatest at the level of prevalent segment linkages, which corresponds at Wytch Farm with the predominant hydrocarbon-producing unit, the Sherwood S andstone. At relatively shallower depths, fault segments are younger and le ss evolved, resulting in a greater degree of segmentation with intact relay zones.