4D Pre-stack Seismic Inversion of Multi-vintages - A Case Study on the Norne Field

Time lapse seismic is now commonly used by the oil and gas industry to monitor fluid displacements in conventional reservoirs. A 4D elastic inversion workflow is described and applied to seismic data recorded in 2001, 2003 and 2004 over the Norne field, a reservoir of Lower and Middle Jurassic Age in the southern part of the Nordland II area, in the Norwegian Sea. We compare the P- and S-wave optimal impedance distributions obtained from independent inversions of the three vintages with those obtained after a joint inversion of the same vintages. Such a workflow requires two scaling laws to match the different monitor time bases in the joint inversion process. Each scaling law is provided by a warping technique computing time shift according to impedances provided by independent inversions. In the end, the 4D inversion workflow yields quantitative estimates of the elastic impedances. The case study presented here emphasizes the added value of 4D joint stratigraphic inversion to help understanding production effects on reservoir properties.