REPRESENTATION OF NORMAL SLANT FAULTS IN A 2D BURIAL HISTORY MODEL

A discussion is given of the impact of normal slant faults on basinal structure, compaction, fluid overpressure development, and thermal eff ects in sedimentary basins. Faults which are hydraulically closed or o pen to fluid flow are examined in a dynamical two-dimensional fluid/fl ow compaction model. From this numerical investigation three dominant factors characterize the effects of single and multiple faults with op en or closed hydraulic behaviours: (i) there is a difference in excess pressure for fault planes with open or shut hydraulic conditions, but the neighbourhood where the effect of the fault is dominant is fairly localized (to within about half a kilometre or so laterally from the fault plane); (ii) the lateral and vertical motion of sediments betwee n faulted blocks induces a thermal difference prior to, during, and po st-faulting, which can play a role in influencing hydrocarbon generati on, migration, and accumulation; (iii) porosity retention and permeabi lity modification by fault development could influence hydrocarbon exp loration decisions regarding sealing, migration pathways, and fluid re tention. The general patterns of slant fault effects described here sh ould prevail in most geological situations, because the numerical expe riments are designed to illuminate sharply the dominant response chara cteristics within the framework of simplified situations.