Simultaneous joint migration inversion for high‐resolution imaging/inversion of time‐lapse seismic datasets

Abstract

ABSTRACTThe current time‐lapse practice is to exactly repeat well‐sampled acquisition geometries to mitigate acquisition effects on the time‐lapse differences. In order to relax the rigid requirements on acquisition effects, we propose simultaneous joint migration inversion as an effective time‐lapse tool for reservoir monitoring, which combines a joint time‐lapse data processing strategy with the joint migration inversion method. Joint migration inversion is a full‐wavefield inversion method that explains the measured reflection data using a parameterization in terms of reflectivity and propagation velocity. Both the inversion process inside the imaging/inversion scheme and the extra illumination provided by including multiples in joint migration inversion makes the obtained velocity and reflectivity operator largely independent of the utilized acquisition geometry and, thereby, relaxes the strong requirement of non‐repeatability during the monitoring. Because simultaneous joint migration inversion inverts for all datasets simultaneously and utilizes various constraints on the estimated reflectivities and velocity, the obtained time‐lapse differences have much higher accuracy compared to inverting each dataset separately. It allows the baseline and monitor parameters to communicate with each other dynamically during inversion via a user‐defined spatial weighting operator. In order to get more localized time‐lapse velocity differences, we further extend the regular simultaneous joint migration inversion to a robust high‐resolution simultaneous joint migration inversion process using the time‐lapse reflectivity difference as an extra constraint for the velocity estimation during inversion. This constraint makes a link between the reflectivity‐ and the velocity difference by exploiting the relationship between them. We demonstrate the feasibility of the proposed method with a highly realistic synthetic model based on the Grane field offshore Norway and a time‐lapse field dataset from the Troll Field.