A full field study using the geomechanical simulator with a reservoir model was performed to help assess the integrity of the development plan. The study comprised four phases:
Phase I: Enhance the reservoir model.
Phase II: Obtain the stress state prior to any operations.
Phase III: Perform coupled flow/stress modeling to assess the stress and strain changes induced by production/injection operations up to today.
Phase IV: History match the field data using Geomechanics.
Using the graphical pre and post processor VisGen, the reservoir model was extended up to the sea floor. Layers were added on the bottom of the reservoir model to serve as underburden and cells were added on each of the 4 vertical boundaries to serve as the sideburden. Faults and fracture sets were incorporated in the embedded model. The mechanical properties were determined. A stress calibration was determined.
An effective initial stress state was computed that took into account all the complexity of the geomechanical model including contrast in mechanical properties and discontinuity in the rock. The computed initial stress state was in agreement with field data and geological features.
The changes in stress and strain induced by the production/injection operations were assessed using a geomechanical simulator. The computed compaction was in agreement with the estimated value from 4D seismic data. Further, the coupled simulations have demonstrated that compaction and subsidence effects are to be attributed to pore collapse within the reservoir layers and that differential of pore collapse could result in localized well failure.
Finally a coupled fluid flow/stress simulation was performed with dynamic permeability changes according to stress and strain changes. It was established than it was possible to history match the field data based on Geomechanics.
This study demonstrates that geomechanical modeling lends direct support to drilling operations and reservoir management.