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

P P P P I I P P Case 1 P P Case 2 I Injection well P Production well 150 meters Figure 7.8. Well configurations used for the five-spot production scenarios—square pattern 150 m on a side with central injector and producers at the corners. In Case 1, one diagonal of the five-spot is aligned with the dominant band trend (left). In Case 2, both diagonals are oriented obliquely (~45°) to the bands. 186
5.2. Reservoir production A standard five-spot production-well configuration—square, with central injector and producers at the corners—was used to simulate two-phase (oil-water) incompressible flow within the band pattern. Two case scenarios were modeled using the same 5.5-acre pattern (150 m on a side)—the only difference being a 45° rotation of the production- wells about a fixed injector location (Figure 7.8). In Case 1, the straight-line path from injector to two of the producers runs generally along the dominant band trend, while the path to the two other producers runs generally across it. In Case 2, the straight-line paths from injector to all four producers run oblique to the dominant band trend. For both cases, we specified complete initial saturation of the pore volume with oil, exact balance at all times between the total volume of water injected and the total volume of fluid produced, and equal pressure at all four production wells. A total injection/pumping rate of 15.9 m 3 /day was used and both simulations were run for 250 days, yielding a total pore volume injected (PVI) of 0.15 (i.e. 15% of the total model pore volume). Relative permeability was accounted for using representative data for light crude oil (viscosity 2 cp) as the nonwetting phase and formation water (viscosity 1 cp) as the wetting phase in granular media similar to the Aztec sandstone (Table 1). Capillary pressure is neglected in these simulations, as attempting to include it produced computational problems. The efficient handling of strong capillary effects may require the modification of some of our numerical treatments. The simulation results are presented in Figures 7.9 and 7.10. 5.2.1. Results Figure 7.9 shows equivalent saturation-map snapshots for the two simulations at approximately 0.03, 0.09 and 0.15 PVI. In both cases, the elliptical patterns of water infiltration that develop suggest a strong tendency toward preferred transport along the dominant band trend. Judging from the aspect ratios of the infiltration patterns, the transport rate along the band trend exceeds that across it by at least a factor of two. This effect results in early breakthrough of water to the production wells oriented along the band trend from the injector in Case 1 at < 0.03 PVI (Figure 7.9a). For Case 2, significant breakthrough does not occur until 0.09 PVI (Figure 7.9b). These diverging results are clearly reflected at 0.15 PVI (Figure 7.9c), when the substantially greater area of water infiltration for Case 2 illustrates that 56% more oil has been produced than in Case 1. 187
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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
Page 148 and 149: Permeability (mD) 10 4 10 3 10 2 10
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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 200 and 201: Case 1 Case 1 Case 1 (a) (b) (c) In
Page 202 and 203: 5.2.2. Discussion The elliptical pa
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
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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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