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In-Depth Information
Pressure ield #1
Pressure ield #4
2340
2360
2340
2360
2380
Saturation front
0.8
0.8
Saturation front
0.6
0.6
2380
2400
2420
Focus point
Focus point
0.4
0.4
2400
2420
0.2
0.2
0
0
2440
2440
−0.2
−0.2
50
100
150
200
50
100
150
200
Offset (m)
(a)
(d)
Offset (m)
Pressure ield at focus time
Pressure ield #2
2340
2360
2340
2360
2380
0.8
Saturation front
Saturation front
0.8
0.6
0.6
2380
2400
2420
Focus point
0.4
Focus point
0.4
2400
2420
0.2
0.2
0
0
2440
2440
−0.2
−0.2
50
100
150
200
50
100
150
200
Offset (m)
(b)
Offset (m)
(e)
Pressure ield #3
Electric potential at focus time
0.5
2340
2340
2360
2380
0.8
Saturation front
Saturation front
2360
2380
0.6
Focus point
Focus point
0.4
0
2400
2420
2440
2400
2420
0.2
0
2440
−0.2
−0.5
50
100
150
200
50
100
150
200
(c)
Offset (m)
(f)
Offset (m)
Figur
e
6.10
Seismic beamforming at the saturation front and resulting electrical potential distribution.
(a
-
e)
Evolution
of the confining pressure
P
(r,
t
) for 5 snapshots. The propagating wave fields interfere constructively at the focus point.
f
) Electrical potential distribution corresponding to the seismic energy focused at the saturation front (snapshot e).
(
See insert for color representation of the figure
.)
6.3 High-definition resistivity imaging
6.3.1 Step 1: the seismoelectric
focusing approach
We first illustrate our method using a heterogeneous
material that is bimodal in terms of the distribution of its
material properties (Figure 6.12). For instance, one phase
represents the porous material saturated with water, and
the other the porous material partially saturated with oil.
The properties of these
The goal of this section is to show that we can use the
beamforming approach described in Section 6.2 to
produce a high-definition map of the heterogeneities of
a formation. Then this map can be used in image-guided
inversion to help the inversion of apparent resistivity
data to converge to a more realistic model, producing
resistivity values close to the real ones. This is especially
useful if we want to monitor resistivity changes
associated with changes in the water saturation of a
reservoir.
”
rocks are provided in Table 6.3. Figure 6.12c shows
the position of two wells in which seismic receivers are
placed. The goal is to scan all the space indicated by the
yellow rectangle in Figure 6.12c (
“
reservoir
”
and
“
nonreservoir
will denote this
ℜ
