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Zamora Valcarce et al.<ref name=Zamoravalcarceetal_2006 /> used fault restoration to validate the El Porton field structure in Argentina prior to building a 3-D model of the field. The model was to be built to help plan the trajectories of new development wells. The idea behind validating the structural model was to give extra confidence that a planned well could be expected to intersect with the intended reservoir target given the structural complexities of the reservoir ([[:file:M91Ch13FG85.JPG|Figure 7]]).

Zamora Valcarce et al.<ref name=Zamoravalcarceetal_2006 /> used fault restoration to validate the El Porton field structure in Argentina prior to building a 3-D model of the field. The model was to be built to help plan the trajectories of new development wells. The idea behind validating the structural model was to give extra confidence that a planned well could be expected to intersect with the intended reservoir target given the structural complexities of the reservoir ([[:file:M91Ch13FG85.JPG|Figure 7]]).

[[file:M91Ch13FG86.JPG|thumb|300px|{{figure number|8}}Relay ramps are found in the zone between two overlapping faults. They potentially provide pathways for fluid flow across a fault zone (from Peacock and Sanderson<ref name=Peacockandsanderson_1994>Peacock, D. C. P., and D. J. Sanderson, 1994, Geometry and displacement of relay ramps on normal fault systems: AAPG Bulletin, v. 78, no. 2, p. 147–165.</ref>).]]

[[file:M91Ch13FG86.JPG|thumb|300px|{{figure number|8}}Relay ramps are found in the zone between two overlapping faults. They potentially provide pathways for fluid flow across a fault zone (from Peacock and Sanderson<ref name=Peacockandsanderson_1994>Peacock, D. C. P., and D. J. Sanderson, 1994, [http://archives.datapages.com/data/bulletns/1994-96/data/pg/0078/0002/0100/0147.htm Geometry and displacement of relay ramps on normal fault systems]: AAPG Bulletin, v. 78, no. 2, p. 147–165.</ref>).]]

Fault restoration can also give insights into the structural history of an oil field. By determining the timing for episodes of faulting, uplift, and erosion, insights can be gained that allow the structural controls on reservoir development to be understood.

Fault restoration can also give insights into the structural history of an oil field. By determining the timing for episodes of faulting, uplift, and erosion, insights can be gained that allow the structural controls on reservoir development to be understood.

Damage zones in impure sandstones (those with 15–40% clay) contain phyllosilicate-framework fault rocks. These are anastomozing zones where the rock has been disaggregated and the clays have been mixed in with the framework grains to produce a more homogenous mixture of clays than is present in the undeformed host rock. Faults affecting clay-rich sandstones with more than 40% clay content form clay smears.<ref name=Fisherandknipe_1998>Fisher, Q. J., and R. J. Knipe, 1988, Fault sealing processes in siliciclastic sediments, ''in'' H. Jones, Q. J. Fisher, and R. J. Knipe, eds., Faulting, fault sealing and fluid flow in hydrocarbon reservoirs: Geological Society (London) Special Publication 147, p. 117–134.</ref>

Damage zones in impure sandstones (those with 15–40% clay) contain phyllosilicate-framework fault rocks. These are anastomozing zones where the rock has been disaggregated and the clays have been mixed in with the framework grains to produce a more homogenous mixture of clays than is present in the undeformed host rock. Faults affecting clay-rich sandstones with more than 40% clay content form clay smears.<ref name=Fisherandknipe_1998>Fisher, Q. J., and R. J. Knipe, 1988, Fault sealing processes in siliciclastic sediments, ''in'' H. Jones, Q. J. Fisher, and R. J. Knipe, eds., Faulting, fault sealing and fluid flow in hydrocarbon reservoirs: Geological Society (London) Special Publication 147, p. 117–134.</ref>

The intensity of damage decreases away from the fault with the width of the damage zone roughly proportional to the throw of the fault (Knott, 1994; Knott et al., 1996). Field work on faulting in the Navajo Sandstone of Utah found that the summed width of the damage zones on either side of the fault core is approximately 2.5 times the total fault throw (Shipton and Cowie, 2001). Note that this observation is case specific for this locality. Large and rapid variations in damage zone thickness occur along many faults, and any estimate attempting to systematically relate damage zone thickness to fault throw is liable to a significant uncertainty as a result (Fossen and Bale, 2007).

The intensity of damage decreases away from the fault with the width of the damage zone roughly proportional to the throw of the fault.<ref name=Knott_1994>Knott, S. D., 1994, Fault zone thickness versus displacement in the Permo-Triassic sandstones of NW England: Journal of the Geological Society, v. 151, p. 17–25.</ref> <ref name=Knottetal_1996>Knott, S. D., A. Beach, P. J. Brockbank, J. L. Brown, J. E. McCallum, and A. I. Welbon, 1996, Spatial and mechanical controls on normal fault populations: Journal of Structural Geology, v. 18, no. 2/3, p. 359–372.</ref> Field work on faulting in the Navajo Sandstone of Utah found that the summed width of the damage zones on either side of the fault core is approximately 2.5 times the total fault throw.<ref name=Shiptonandcowie_2001>Shipton, Z. K., and P. A. Cowie, 2001, Damage zone development over micron to kilometer scales in high-porosity Navajo sandstone, Utah: Journal of Structural Geology, v. 23, p. 1825–1844.</ref> Note that this observation is case specific for this locality. Large and rapid variations in damage zone thickness occur along many faults, and any estimate attempting to systematically relate damage zone thickness to fault throw is liable to a significant uncertainty as a result.<ref name=Fossenandbale_2007>Fossen, H., and A. Bale, 2007, [http://archives.datapages.com/data/bulletns/2007/12dec/BLTN06146/BLTN06146.HTM Deformation bands and their influence on fluid flow]: AAPG Bulletin, v. 91, no. 12, p. 1685–1700.</ref>

A study on the Big Hole Fault in Utah based on core data showed a significant permeability reduction within the damage zone (Shipton et al., 2002). Probe permeameter measurements of permeability range from more than 2000 md in the undeformed host sandstone to less than 0.1 md in fault-damaged rocks near the fault. Whole-core tests showed that the permeability of individual deformation bands vary between 0.9 and 1.3 md. The transverse permeability modeled over 5–10-m (16–32-ft)-length scales across the fault zone was estimated as 30–40 md. This is approximately 1–4% of the permeability for the undeformed host rock.

A study on the Big Hole Fault in Utah based on core data showed a significant permeability reduction within the damage zone.<ref name=Shiptonetal_2002>Shipton, Z. K., J. P. Evans, K. R. Robeson, C. B. Forster, and S. Snelgrove, 2002, [http://archives.datapages.com/data/bulletns/2002/05may/0863/0863.htm Structural heterogeneity and permeability in faulted eolian sandstone: Implications for subsurface modeling of fault]s: AAPG Bulletin, v. 86, no. 5, p. 863–883.</ref> Probe permeameter measurements of permeability range from more than 2000 md in the undeformed host sandstone to less than 0.1 md in fault-damaged rocks near the fault. Whole-core tests showed that the permeability of individual deformation bands vary between 0.9 and 1.3 md. The transverse permeability modeled over 5–10-m (16–32-ft)-length scales across the fault zone was estimated as 30–40 md. This is approximately 1–4% of the permeability for the undeformed host rock.

The general consensus in the industry is that damage zones around faults probably baffle flow across them rather than acting as barriers to fluid movement (Sternlof et al., 2004; Fossen and Bale, 2007). The exception may be in deep reservoirs with high reservoir temperatures (more than 120&deg;C). Here, accelerated quartz cementation at high temperature can decrease the pore throat diameters in the deformation bands to the extent that they become 100% water wet through capillary action. They thus become effective barriers to oil flow (Hesthammer et al., 2002).

The general consensus in the industry is that damage zones around faults probably baffle flow across them rather than acting as barriers to fluid movement (Sternlof et al., 2004; Fossen and Bale, 2007). The exception may be in deep reservoirs with high reservoir temperatures (more than 120&deg;C). Here, accelerated quartz cementation at high temperature can decrease the pore throat diameters in the deformation bands to the extent that they become 100% water wet through capillary action. They thus become effective barriers to oil flow (Hesthammer et al., 2002).