Timelapse images

The CO2 plume is imaged as a number of bright sub-horizontal reflections within the reservoir, growing with time (Figure 2a). The reflections are interpreted as arising from thin (< 8 m thick) layers of CO2 trapped beneath thin intra-reservoir mudstones and the reservoir caprock. The plume is roughly 200 m high and elliptical in plan, with a major axis increasing from about 1500 m in 1999 to about 2000 m in 2001 (Figure 2b). The plume is underlain by a prominent velocity pushdown (Figure 3) caused by the seismic waves travelling much more slowly through CO2-saturated rock than through the virgin aquifer.

Figure 3. Velocity pushdown. a) Inline through the reservoir in 1994 and 1999 showing pushdown of the Base Utsira Sand beneath the plume. b) Cross-correlogram of a reflection window beneath the central part of the 2001 plume. Pick follows the correlation peak and defines pushdown. c) Pushdown maps in 1999 and 2001. Black disc denotes injection point.

Figure 3. Velocity pushdown. a) Inline through the reservoir in 1994 and 1999 showing pushdown of the Base Utsira Sand beneath the plume. b) Cross-correlogram of a reflection window beneath the central part of the 2001 plume. Pick follows the correlation peak and defines pushdown. c) Pushdown maps in 1999 and 2001. Black disc denotes injection point.

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