structural geology, propagation mechanics and - Stanford School of ...

To produce a consistent and representative CB map for flow modeling, we applied the
simple criteria that only band traces that could unequivocally be identified on the high-
resolution scan were included on the map. In particular, no attempt was made to
interpolate band patterns through areas of poor exposure due to sediment cover or the
damage caused by younger, mid-Tertiary strike-slip faulting. Nor was any attempt made
to extrapolate band patterns in order to increase the area of coverage. In this way, a
consistent and conservative standard of objectivity was maintained while complications
and uncertainties associated with pattern matching and infilling were avoided.
The resulting 150,000 m 2 CB map (Figure 7.3) represents more than 2000 individual
band traces ranging from a few meters to more than 100 m in length, with an average
spacing of about 1.5 to 2 m. Successive intersections between bands occasionally form
through-going trends hundreds of meters long. Average band thickness measured in the
field is about 1 cm while spacing averages about 0.5 to 0.75 m—roughly one third that
captured on the map. Clustering of CBs (mm spacing) is also common, resulting in
composite bands up to 10 cm and more in total thickness. Field checking indicated that
most gaps within the mapped array not attributable to sedimentary cover or fault damage
do represent real interruptions in the continuity of the band fabric, although the absence
of distinct fins and/or poor image resolution was occasionally to blame. All areas of
bands identified and mapped on the scan were found to exist in outcrop.
4. Flow simulation model
In the scenarios considered below, both single-phase and two-phase flow simulations
are performed. The basic governing equation for incompressible single-phase flow in
porous media is obtained by combining Darcy's law with conservation of mass:
⎛ k ⎞
∇ ⋅⎜
∇p⎟
+ Q = 0 , (1)
⎝ µ ⎠
where p is pressure and Q represents sources and/or sinks (e.g., production/injection
wells). The fluid is described by its viscosity µ , while k represents the absolute
(intrinsic) permeability of the rock. Consistent with core measurements for the sandstone
systems considered here, we take k to be locally isotropic for both the compaction bands
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