4-D Seismic
Monitoring of an Active Steamflood
David E. Lumely, Michel Bee, Steve Jenkins, and Zhijing
Wang
Multiple 3-D seismic
surveys have been acquired at time-lapse intervals over
a heavy oil reservoir in the Duri Field, Indonesia, to monitor the progress of
an active steamflood. Time-lapse 3-D
seismic
images show dramatic and complex
changes in the reservoir zone over a wide area, compared to baseline
seismic
data recorded prior to steam injection. Careful consideration of steamflood
fluid-flow, rock physics measurements, finite-difference seismogram modeling,
3-D
seismic
imaging and velocity analysis leads to an integrated interpretation
of this 4-D data set.
Anticipated large decreases in seismic
P-wave velocity near the injection
well correlate with the presence of a hot steam-saturated zone. Unanticipated
large velocity increases and reflectivity changes in an annulus around the steam
zone are consistent with a transient high-pressure front, in which initial free
gas in pore space is raised above the bubble point pressure and dissolves into
liquid oil. Horizontal and vertical
anisotropy
in flow directions inferred from
these
seismic
observations correlate with two temperature monitor wells, and in
situ measurements of upper and lower reservoir permeability. Since the pressure
front propagates out from the injector at least one order of magnitude faster
than either the thermal or steam fronts, monitoring it may be useful for
predicting f owpaths of heated oil and steam, months in advance.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California