Modelling of a deepwater Brazilian field to assess fault reactivation and the insitu stresses during production

Fault reactivation and stress distribution are considered during a 30-year production period on a deep-water oil field using a 3D finite element geomechanical numerical simulation. Field geometry is constructed as a geomechanical model with the simulation carried out in terms of total stress; the model incorporated a network of 54 pre-existing faults which permits actual slip to occur. The principal objective is to determine whether the existing faults would propagate through to the seabed during production. The pre-production phase aims to capture material and stress states of the field accounting for salt creep and stress realignment due to the presence of the predefined faults. Preproduction stresses show good agreement with minifrac experimental results; the 3D simulation overestimates the minimum horizontal stress by 1.7-3.7%. The production stage shows that vertical compaction of the reservoir is the major influence on fault slip; the rate and magnitude of the fault slip is directly related to the rate and magnitude of depletion. The maximum fault slip is 0.82 m with normal faulting occurring beneath and thrust faulting occurring above the reservoir. Fault slip is not significant close to the seabed and the pre-existing faults are not anticipated to propagate to the seabed.