Imaging Drainage of Turbidite Reservoirs Though Time-lapse Seismic Analysis at Bullwinkle, Green Canyon Block 65, Offshore Gulf of Mexico
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چکیده
Two orthogonal pre-production seismic surveys and a seismic survey acquired after eight years of production from the Bullwinkle field (GC 65, Gulf of Mexico) reveal extraordinary seismic differences that are attributed to productioninduced changes in rock and fluid properties. Separate normalizations of these surveys demonstrate that timelapse results are improved by utilizing seismic surveys that were acquired in similar orientations, and also that clearer difference images are obtained from comparing lower frequency datasets. Amplitude reduction is documented where production and log data show that water has replaced hydrocarbons as the oil-water-contact moved upwards. A smaller decrease in seismic amplitude in response to sediment compaction is also observed in the aquifer of the main reservoir sand. An otherwise convincing timelapse result from the near-perpendicularly orientated surveys is undermined by dimming above the oil water contact and lower aquifer correlation. This provides a warning of the danger of using dissimilar baseline and monitor surveys. After normalization, the non-whitened (lower frequency) surveys are more similar than the whitened surveys, and give the clearest image of large changes in seismic events. At Bullwinkle, this occurs to some extent at the expense of the ability to resolve smaller hydrocarbon reservoirs. Spectral whitening may therefore be useful if it is necessary to investigate changes in closely stacked reservoirs sands.
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تاریخ انتشار 2001