You must log in to edit PetroWiki. Help with editing
Content of PetroWiki is intended for personal use only and to supplement, not replace, engineering judgment. SPE disclaims any and all liability for your use of such content. More information
No edit summary |
No edit summary |
||
| Line 25: | Line 25: | ||
''ν'' = Poisson | ''ν'' = Poisson | ||
<nowiki>’</nowiki> | <nowiki>’</nowiki> | ||
s ratio, | s ratio, ''σ''<sub>1</sub> = overburden stress, | ||
''σ''<sub>1</sub> = overburden stress, | |||
''α'' = Biot | ''α'' = Biot | ||
<nowiki>’</nowiki> | <nowiki>’</nowiki> | ||
s constant, | s constant, ''p''<sub>''p''</sub> = reservoir fluid pressure or pore pressure, and | ||
''p''<sub>''p''</sub> = reservoir fluid pressure or pore pressure, and | |||
''σ''<sub>ext</sub> = tectonic stress. | ''σ''<sub>ext</sub> = tectonic stress. | ||
| Line 39: | Line 35: | ||
s ratio can be estimated from acoustic log data or from correlations based on lithology. '''Table 1''' presents typical ranges for Poisson<nowiki>’</nowiki> | s ratio can be estimated from acoustic log data or from correlations based on lithology. '''Table 1''' presents typical ranges for Poisson<nowiki>’</nowiki> | ||
s ratio. The overburden stress can be computed with density log data. Normally, the value for overburden stress is approximately 1 psi/ft of depth. The reservoir pressure must be measured or estimated. Biot<nowiki>’</nowiki> | s ratio. The overburden stress can be computed with density log data. Normally, the value for overburden stress is approximately 1 psi/ft of depth. The reservoir pressure must be measured or estimated. Biot<nowiki>’</nowiki> | ||
s constant is usually 1.0, but can be less than 1.0 on occasion. | s constant is usually 1.0, but can be less than 1.0 on occasion. <gallery widths="300px" heights="200px"> | ||
<gallery widths="300px" heights="200px"> | |||
File:Vol4prt Page 329 Image 0001.png|'''Table 1- Table Range Of Values For Young Modulus''' | File:Vol4prt Page 329 Image 0001.png|'''Table 1- Table Range Of Values For Young Modulus''' | ||
</gallery> | </gallery> | ||
Poroelastic theory is often used to estimate the minimum horizontal stress.<ref name="r4">Whitehead, W.S., Hunt, E.R., and Holditch, S.A. 1987. The Effects of Lithology and Reservoir Pressure on the In-Situ Stresses in the Waskom (Travis Peak) Field. Presented at the Low Permeability Reservoirs Symposium, Denver, Colorado, USA, 18–19 May. SPE-16403-MS. http://dx.doi.org/10.2118/16403-MS.</ref><ref name="r5">Salz, L.B. 1977. Relationship Between Fracture Propagation Pressure and Pore Pressure. Presented at the SPE Annual Fall Technical Conference and Exhibition, Denver, Colorado, USA, 9–12 October. SPE-6870-MS. http://dx.doi.org/10.2118/6870-MS._</ref><ref name="r6">Veatch Jr., R.W. and Moschovidis, Z.A. 1986. An Overview of Recent Advances in Hydraulic Fracturing Technology. Presented at the International Meeting on Petroleum Engineering, Beijing, China, 17-20 March. SPE-14085-MS. http://dx.doi.org/10.2118/14085-MS.</ref> '''Eq. 1''' combines poroelastic theory with a term that accounts for any tectonic forces that are acting on a formation. The first term on the right side of '''Eq. 1''' is a linear elastic term that converts the effective vertical stress on the rock grains into an effective horizontal stress on the rock grains. The second term in Eq. 1 represents the stress generated by the fluid pressure in the pore space. The third term is the tectonic stress, which could be zero in tectonically relaxed areas, but can be important in tectonically active areas. | Poroelastic theory is often used to estimate the minimum horizontal stress.<ref name="r4">Whitehead, W.S., Hunt, E.R., and Holditch, S.A. 1987. The Effects of Lithology and Reservoir Pressure on the In-Situ Stresses in the Waskom (Travis Peak) Field. Presented at the Low Permeability Reservoirs Symposium, Denver, Colorado, USA, 18–19 May. SPE-16403-MS. http://dx.doi.org/10.2118/16403-MS.</ref><ref name="r5">Salz, L.B. 1977. Relationship Between Fracture Propagation Pressure and Pore Pressure. Presented at the SPE Annual Fall Technical Conference and Exhibition, Denver, Colorado, USA, 9–12 October. SPE-6870-MS. http://dx.doi.org/10.2118/6870-MS._</ref><ref name="r6">Veatch Jr., R.W. and Moschovidis, Z.A. 1986. An Overview of Recent Advances in Hydraulic Fracturing Technology. Presented at the International Meeting on Petroleum Engineering, Beijing, China, 17-20 March. SPE-14085-MS. http://dx.doi.org/10.2118/14085-MS.</ref> '''Eq. 1''' combines poroelastic theory with a term that accounts for any tectonic forces that are acting on a formation. The first term on the right side of '''Eq. 1''' is a linear elastic term that converts the effective vertical stress on the rock grains into an effective horizontal stress on the rock grains. The second term in Eq. 1 represents the stress generated by the fluid pressure in the pore space. The third term is the tectonic stress, which could be zero in tectonically relaxed areas, but can be important in tectonically active areas. | ||
| Line 53: | Line 47: | ||
<nowiki>’</nowiki> | <nowiki>’</nowiki> | ||
s ratio is defined as "the ratio of lateral expansion to longitudinal contraction for a rock under a uniaxial stress condition."<ref name="r2">Gidley, J.L., Holditch, S.A., Nierode, D.E. et al. 1989. Rock Mechanics and Fracture Geometry. In Recent Advances in Hydraulic Fracturing, 12. Chap. 3, 57-63. Richardson, Texas: Monograph Series, SPE.</ref> The value of Poisson<nowiki>’</nowiki> | s ratio is defined as "the ratio of lateral expansion to longitudinal contraction for a rock under a uniaxial stress condition."<ref name="r2">Gidley, J.L., Holditch, S.A., Nierode, D.E. et al. 1989. Rock Mechanics and Fracture Geometry. In Recent Advances in Hydraulic Fracturing, 12. Chap. 3, 57-63. Richardson, Texas: Monograph Series, SPE.</ref> The value of Poisson<nowiki>’</nowiki> | ||
s ratio is used in '''Eq. 1''' to convert the effective vertical stress component into an effective horizontal stress component. The effective stress is defined as the total stress minus the pore pressure. | s ratio is used in '''Eq. 1''' to convert the effective vertical stress component into an effective horizontal stress component. The effective stress is defined as the total stress minus the pore pressure. The theory used to compute fracture dimensions is based on linear elasticity. When applying this theory, the modulus of the formation is an important parameter. Young<nowiki>’</nowiki> | ||
The theory used to compute fracture dimensions is based on linear elasticity. When applying this theory, the modulus of the formation is an important parameter. Young | |||
<nowiki>’</nowiki> | |||
s modulus is defined as "the ratio of stress to strain for uniaxial stress."<ref name="r2">Gidley, J.L., Holditch, S.A., Nierode, D.E. et al. 1989. Rock Mechanics and Fracture Geometry. In Recent Advances in Hydraulic Fracturing, 12. Chap. 3, 57-63. Richardson, Texas: Monograph Series, SPE.</ref> The modulus of a material is a measure of the stiffness of the material. If the modulus is large, the material is stiff. In hydraulic fracturing, a stiff rock results in more narrow fractures. If the modulus is low, the fractures are wider. The modulus of a rock is a function of the lithology, porosity, fluid type, and other variables. '''Table 1''' illustrates typical ranges for modulus as a function of lithology. | s modulus is defined as "the ratio of stress to strain for uniaxial stress."<ref name="r2">Gidley, J.L., Holditch, S.A., Nierode, D.E. et al. 1989. Rock Mechanics and Fracture Geometry. In Recent Advances in Hydraulic Fracturing, 12. Chap. 3, 57-63. Richardson, Texas: Monograph Series, SPE.</ref> The modulus of a material is a measure of the stiffness of the material. If the modulus is large, the material is stiff. In hydraulic fracturing, a stiff rock results in more narrow fractures. If the modulus is low, the fractures are wider. The modulus of a rock is a function of the lithology, porosity, fluid type, and other variables. '''Table 1''' illustrates typical ranges for modulus as a function of lithology. | ||
== Fracture orientation == | == Fracture orientation == | ||
| Line 155: | Line 147: | ||
| = | | = | ||
| Poisson<nowiki>’</nowiki> | | Poisson<nowiki>’</nowiki> | ||
s ratio | s ratio | ||
|- | |- | ||
| ''σ''<sub>min</sub> | | ''σ''<sub>min</sub> | ||
| Line 196: | Line 190: | ||
[[PEH:Hydraulic_Fracturing]] | [[PEH:Hydraulic_Fracturing]] | ||
==Category== | == Page champions == | ||
[www.linkedin.com/in/renealcalde Rene Alcalde] | |||
== Category == | |||
[[Category:2.5 Hydraulic fracturing]] [[Category:YR]] | [[Category:2.5 Hydraulic fracturing]] [[Category:YR]] | ||
edits