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Fig. 8.5 Maui field: type log across the reservoir interval, and comparison of models to real
time-lapse seismic. Reproduced with permission from Hatchell et al. (2002).
and the question was whether water is simply displacing gas vertically throughout the
reservoir or whether the water is preferentially moving through the uppermost and
most permeable sands, over-riding unproduced gas in the less permeable sands below.
Figure 8.5 shows a comparison between the real time-lapse data and synthetic models
for the two cases. Clearly, the real data are in close agreement to the prediction with
water over-ride.
Stammeijer et al. (2002) have published the example shown in fig. 8.6 . This shows
time-lapse results over a mature field in the Northern North Sea that is being produced by
water-flood. The baseline survey was acquired in 1995, some six years after production
began, and the repeat survey was acquired in 2000. In this case, connected volume
analysis (as discussed in chapter 7 ) was used to identify the zones where oil had been
swept from the reservoir in the period between the two surveys. Some of the zones
where no change has occurred can be identified as areas completely swept before 1995.
The others represent unswept areas, which can now be targeted by an infill drilling
programme.
Repeat seismic surveys over a field in the UK West Shetland area allowed a flood
front to be seen (fig. 8.7) . Shortly after the repeat seismic survey showed that the flood
front was approaching the producer, significant water production began to be observed.
 
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