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Case study

The Norne field is located in the Norwegian North sea. The main field is a 9 km x 3 km horst block comprised of high-porosity, high-permeability, high net-to-gross lower and middle Jurassic sandstones. The field was discovered in 1991 and production started in 1997. For this study, four high-resolution Q-marine time-lapse seismic data sets acquired in 2001, 2003, 2004 and 2006 are considered. The 2001 data is taken as the baseline. Osdal et al. (2006) and Aarre (2008) provide more detailed description of the geology, production history, time-lapse seismic acquisition and processing, and some interpretation of the time-lapse seismic response at the Norne.

The apparent vertical displacements (time-shifts) for three cycles between the 2006 and the 2001 data are shown in Figure 1. In this figure, and in similar ones throughout this paper, the orthogonal lines show slices through a 3D volume at the positions indicated by each line. Figure 2 shows the 2006 time-shifts together with the mapped top of the reservoir. The corresponding lateral displacements in the inline and cross-line directions (after three cycles) are shown in Figure 3. Figures 4 to 6 show the absolute vertical and lateral displacements overlain by arrows indicating the displacement direction. Estimated velocity changes at different production stages are shown in Figure 7. It is assumed that the time-shift estimates obtained by considering displacements in all directions are accurate. Differences between time-shifts, velocity changes and vertical strains obtained by considering all displacement components and those obtained by considering only vertical displacements are shown in Figure 8. The optimal match-filter parameters obtained by the evolutionary programming method are shown in Figure 9. Figures 10 and 11 show time-lapse images obtained after different processing steps. Amplitude errors resulting from considering only vertical displacements are shown in Figures 12.

Next: Discussion Up: Ayeni: Cyclic matching Previous: Cyclic 1D match-filtering by

2010-05-19