Reservoir Compaction Quantification Using Geomechanical Inversion of Timelapse Timeshifts

Modelling and observation help us to quantify pressure-induced compaction in depleting reservoirs. Reservoir simulators and geomechanical modelling tools provide reservoir compaction maps based on forward modelling, while timelapse seismic data provide compaction maps based on observation in multi-dimensional space. Timeshift attribute of timelapse surveys is the key parameter to obtain reservoir compaction maps from seismic data.<br><br>The compaction timeshifts are small compared to seismic wave periods and various methods for measuring timeshifts will trade spatial and temporal resolution against noise suppression. For example, cross correlation techniques between the base and monitor surveys are robust to noise using long correlation gates but the resultant temporal smearing will mask the true timeshifts in the vicinity of the reservoir interval where the timeshift gradient changes sign. This can lead to inaccurate prediction of the reservoir compaction.<br><br>We propose to use geomechanical models to constrain our timeshift estimation and reduce the errors in the estimated reservoir compaction. This is done using an inversion algorithm that updates a geomechanical model to match the predicted time-lapse seismic response with the actual data. Tests on synthetic and real data examples show that the inversion procedure converges rapidly resulting in better resolution of the underlying reservoir compaction. <br><br>