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$Drilling-induced tensile wall-fractures - Stanford University$

5.2.2. Discussion The elliptical patterns of water infiltration shown in Figure 7.9 demonstrate the dominant impact of the CB pattern on the gross direction of fluid transport. In fact, the saturation maps for the two cases are at first strikingly similar (Figure 7.9a), indicating that the production wells exert a minor influence on transport when compared to channeling of flow along the dominant band trend. These directional transport effects are more pronounced than the relatively modest ∆P ratios presented in Figure 7.7 would suggest. The 56% increase in production efficiency gained in Case 2 for a 45° rotation of the five-spot well configuration is a significant (but not optimized) result that could vary substantially within the CB pattern and for different production configurations. In addition, the scale of our five-spot, as constrained by the available mapped area, is smaller than would typically be installed in a real reservoir production situation. Nonetheless, the petroleum engineer can glean two valuable insights from our results— that the presence of CB arrays can strongly affect production efficiency in reservoirs, but also that relatively simple adjustments in well placement can be made to mitigate and/or harness those effects. 5.3. Contaminant transport In order to examine how the CB array would affect contaminant transport and influence the evolution of a point-source plume, we established a fixed leak location for each of three regional pressure gradient directions: parallel to the dominant band trend, oblique (45°) to the trend, and normal to the trend (Figure 7.11). We considered incompressible contaminant transport (mobility ratio = 1), and neglected physical dispersion. A consistent regional gradient of 0.23 Pa/m (enough to yield an average flow rate of approximately 7.7 m/year in the absence of CBs) was established in each of the three directions by specifying pressures for an array of eight wells distributed around the perimeter of the model domain (just inside the oval no-flow boundary). Each simulation represents 30 years at a constant leak rate of 0.08 m 3 /day. For each scenario, a corresponding CB-free control simulation was conducted. The results of all the simulations are presented in Figures 7.12, 7.13 and 7.14. 190
N Leak 150 meters P O Figure 7.11. Configuration of contaminant leak location with three directions of equal regional pressure gradient used in examining the impact of the compaction band pattern on plume migration (P=parallel to the dominant band trend, O=oblique to the trend, N=normal to the trend). 191 O P N
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STRUCTURAL GEOLOGY, PROPAGATION MEC
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Abstract Low-porosity, low-permeabi
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delivered with fortitude, humor, su
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Chapter 3—Energy-release model of
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List of Illustrations Figure A. Cov
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Figure A. Cover photo that accompan
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likely present in subsurface sandst
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hooking-tip interactions—using th
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and sandstone, my co-authors—Moha
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the hard data from which accurate p
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Although the Aztec sandstone experi
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Waterpocket Fault 36 o 26‘ N 0 1
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Cenozoic Mesozoic Paleozoic Quatern
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3.3. Deformation The Aztec also has
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There also are relatively high-angl
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(e) (f) (c) 500µm compaction band
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dihedral angle of 80° or more, and
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5. Compaction band orientations Ori
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n = 20 M n = 20 P n = 22 B n = 20 R
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were encountered, giving the dihedr
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Eichhubl et al., 2004) did not lend
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P (a) (c) S P S Figure 1.10. Stereo
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possible, and use these to better c
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1.5(ρgz) (b) WEST Willow Tank Uppe
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9. Acknowledgements My sincere than
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The term compaction band (CB) was c
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Pollard, 2002). The particular util
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Hue-based image analysis using MATL
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a direct genetic relationship (Hill
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Compaction band fin Depositional be
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suggests—that to first approximat
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Porosity Porosity 0.3 0.25 0.2 0.15
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pore-clogging clay—due presumably
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500 µm Figure 2.9. Electron backsc
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(a) (b) σ 3 σ 1 x 3 x 1 x 1 (c) u
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6. Elastic properties Despite a lon
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Comparison of the two approaches es
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term in (6a) and (6c) begins to dom
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MPa MPa 80 70 60 50 40 30 20 10 0 0
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2002) and use a BEM approach (Crouc
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MPa 10 4 10 3 10 2 10 1 10 −5 10
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concentration of quartz plasticity
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conducted on well-cemented sandston
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~ 62 m compaction band trend 500µm
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Sternlof et al. (2005) have suggest
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2005). It consists of a long (infin
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⎡ ∆ ⎤ ⎧ p 1 ∆ ⎛ M ⎞
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which point the inelastic strain ha
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they can exert significant effects
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interact is inversely proportional
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(a) (b) (c) (d) Figure 4.3. Typical
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Viewed individually, CB traces tend
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(a) (b) (c) (d) (e) (f) Figure 4.7.
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1973; Mardon, 1988; Peck et al., 19
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undamaged host rock. That CBs canno
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0.5 0.4 0.3 0.2 0.1 0.5 0.4 0.3 0.2
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Normalized stress magnitude 3 2.5 2
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helps to explain why the oblique ap
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and ts = G·ds + H·dn (2) where tn
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plastic compaction, as suggested by
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To determine the sensitivity of pro
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segments will self-correct to provi
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6.3. Approaching tip interactions A
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0.2 0.15 0.1 0.05 0 −0.05 −0.1
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0.2 0.15 0.1 0.05 0 −0.05 −0.1
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the hooking patterns commonly obser
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(a) (b) (c) σ1 compaction band max
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σ 3 σ 2 σ 1 Figure 4.24. Schemat
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NV UT CA AZ Park Road Map Detail Pa
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compaction band Figure 5.2. Typical
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3. Computational method The methodo
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compaction band A 5 mm A‘ compact
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4. Application to the Aztec sandsto
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Permeability (mD) 10 4 10 3 10 2 10
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B‘ A‘ A c f m c m c f c f c f c
Page 152 and 153: equivalent of the Aztec sandstone,
Page 154 and 155: effective permeability represents a
Page 156 and 157: NV UT CA AZ Park Road Map Detail Pa
Page 158 and 159: Commonly from ~1 mm to ~1.5 cm in t
Page 160 and 161: Although systematic arrays of DBs p
Page 162 and 163: to 2 m, with both sets in a cross-h
Page 164 and 165: y identical blocks all subject to t
Page 166 and 167: contiguous areas. This type of char
Page 168 and 169: (0,b) n 3 (0,0) f 2 n 2 n 1 (a,0) (
Page 170 and 171: 6.1. Parallel Effective permeabilit
Page 172 and 173: By contrast, band-parallel effectiv
Page 174 and 175: Relative Effective Permeability 1.0
Page 176 and 177: (a) (b) (c) 0 meters 3 = 10-2 kb /k
Page 178 and 179: Though grossly systematic, anastomo
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Page 182 and 183: 100 meters 5 meters NV UT CA AZ Par
Page 184 and 185: compaction band trend 500µm Figure
Page 186 and 187: Cover Outcrop Band N 100 meters 20
Page 188 and 189: (CBs) and the matrix rock in all si
Page 190 and 191: The finite volume discretization fo
Page 192 and 193: isotropic) can lead to numerical di
Page 194 and 195: 5. Simulations Three sets of 2-D si
Page 196 and 197: Normalized ∆P ∆P ratio (n/p) 4.
Page 198 and 199: P P P P I I P P Case 1 P P Case 2 I
Page 200 and 201: Case 1 Case 1 Case 1 (a) (b) (c) In
Page 204 and 205: 5.3.1. Results With the regional gr
Page 206 and 207: (a) (b) Leak 200 meters Regional gr
Page 208 and 209: anticipated sustainable pumping rat
Page 210 and 211: Finally, there is the issue of fore
Page 212 and 213: 200
Page 214 and 215: Bakke, S., and Øren, P. E., 1997,
Page 216 and 217: Carpenter, D. G., and Carpenter, J.
Page 218 and 219: Eichhubl, P., Taylor, W. L., Pollar
Page 220 and 221: Karimi-Fard, M., Durlofsky, L. J.,
Page 222 and 223: -, 1987, Fracture from a straight c
Page 224 and 225: Shipton, Z. K., and Cowie, P. A., 2
Page 226: Wong, T. F., David, C., and Zhu, W.
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