Integrating 4D seismic, geomechanics andreservoir simulation in the Valhall oil field

摘要

Time-lapse seismic monitoring of compacting reservoirs measures changes that occur both inside andrnoutside of the reservoir interval. Inside the reservoir, changes in saturation, porosity, velocity, andrnlayer thickness alter the reflection coefficients and intra-reservoir travel times that result in bothrnamplitude and travel time changes. Outside of the reservoir, the compaction creates long-wavelengthrnchanges in the stress and strain fields that perturb the seismic velocity and produce additional changesrnin the seismic travel time and amplitudes from the rocks above and below the reservoir. Understandingrnthese changes in the amplitudes and timeshifts leads to an improved understanding of the reservoirrnbehavior and provides additional tools to better manage our fields.rnIn order to account for changes that occur simultaneously inside and outside the reservoir we employrnan integrated workflow that combines the results of reservoir simulation and geomechanical modelingrnto produce time-lapse synthetic seismic that is then compared with the actual time-lapse results.rnDiscrepancies indicate areas where we need to focus our attention and update the underlying models.rnWe apply this workflow to the massively compacting Valhall chalk field located offshore Norway.