structural geology, propagation mechanics and - Stanford School of ...
structural geology, propagation mechanics and - Stanford School of ...
structural geology, propagation mechanics and - Stanford School of ...
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5.2.2. Discussion<br />
The elliptical patterns <strong>of</strong> water infiltration shown in Figure 7.9 demonstrate the<br />
dominant impact <strong>of</strong> the CB pattern on the gross direction <strong>of</strong> fluid transport. In fact, the<br />
saturation maps for the two cases are at first strikingly similar (Figure 7.9a), indicating<br />
that the production wells exert a minor influence on transport when compared to<br />
channeling <strong>of</strong> flow along the dominant b<strong>and</strong> trend. These directional transport effects are<br />
more pronounced than the relatively modest ∆P ratios presented in Figure 7.7 would<br />
suggest.<br />
The 56% increase in production efficiency gained in Case 2 for a 45° rotation <strong>of</strong> the<br />
five-spot well configuration is a significant (but not optimized) result that could vary<br />
substantially within the CB pattern <strong>and</strong> for different production configurations. In<br />
addition, the scale <strong>of</strong> our five-spot, as constrained by the available mapped area, is<br />
smaller than would typically be installed in a real reservoir production situation.<br />
Nonetheless, the petroleum engineer can glean two valuable insights from our results—<br />
that the presence <strong>of</strong> CB arrays can strongly affect production efficiency in reservoirs, but<br />
also that relatively simple adjustments in well placement can be made to mitigate <strong>and</strong>/or<br />
harness those effects.<br />
5.3. Contaminant transport<br />
In order to examine how the CB array would affect contaminant transport <strong>and</strong><br />
influence the evolution <strong>of</strong> a point-source plume, we established a fixed leak location for<br />
each <strong>of</strong> three regional pressure gradient directions: parallel to the dominant b<strong>and</strong> trend,<br />
oblique (45°) to the trend, <strong>and</strong> normal to the trend (Figure 7.11). We considered<br />
incompressible contaminant transport (mobility ratio = 1), <strong>and</strong> neglected physical<br />
dispersion. A consistent regional gradient <strong>of</strong> 0.23 Pa/m (enough to yield an average flow<br />
rate <strong>of</strong> approximately 7.7 m/year in the absence <strong>of</strong> CBs) was established in each <strong>of</strong> the<br />
three directions by specifying pressures for an array <strong>of</strong> eight wells distributed around the<br />
perimeter <strong>of</strong> the model domain (just inside the oval no-flow boundary). Each simulation<br />
represents 30 years at a constant leak rate <strong>of</strong> 0.08 m 3 /day. For each scenario, a<br />
corresponding CB-free control simulation was conducted. The results <strong>of</strong> all the<br />
simulations are presented in Figures 7.12, 7.13 <strong>and</strong> 7.14.<br />
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