Difference between revisions of "Pore system shapes"
Jump to navigation
Jump to search
FWhitehurst (talk | contribs) |
FWhitehurst (talk | contribs) |
||
Line 19: | Line 19: | ||
:<math>\mbox{S}_{\rm w} = \left(\frac{1}{\Phi^{\rm m}} \times \frac{\mbox{R}_{\rm w}}{\mbox{R}_{\rm t}}\right)^{\rm 1/n}</math> | :<math>\mbox{S}_{\rm w} = \left(\frac{1}{\Phi^{\rm m}} \times \frac{\mbox{R}_{\rm w}}{\mbox{R}_{\rm t}}\right)^{\rm 1/n}</math> | ||
+ | |||
+ | where: | ||
+ | |||
+ | * S<sub>w</sub> = water saturation of the uninvaded zone | ||
+ | * n = saturation exponent, which varies from 1.8 to 4.0 but normally is 2.0 | ||
+ | * R<sub>w</sub> = formation water resistivity at formation temperature | ||
+ | * Φ = [[porosity]] | ||
+ | * m = cementation exponent, which varies from 1.7 to 3.0 but normally is 2.0 | ||
+ | * R<sub>t</sub> = true resistivity of the formation, corrected for invasion, borehole, thin bed, and other effects | ||
+ | |||
without modification. To predict water saturation in rocks with non-Archie porosity, we modify the Archie equation. | without modification. To predict water saturation in rocks with non-Archie porosity, we modify the Archie equation. |
Revision as of 18:34, 21 August 2014
Exploring for Oil and Gas Traps | |
Series | Treatise in Petroleum Geology |
---|---|
Part | Predicting the occurrence of oil and gas traps |
Chapter | Predicting reservoir system quality and performance |
Author | Dan J. Hartmann, Edward A. Beaumont |
Link | Web page |
Store | AAPG Store |
Archie and non-Archie rocks
Choquette and Pray's[1] porosity types include two different groups of pore system shapes: petrophysically simple Archie porosity and petrophysically complex non-Archie porosity. In most cases, water saturation (Sw) of rocks with Archie porosity can be predicted from log analysis using the Archie equation
where:
- Sw = water saturation of the uninvaded zone
- n = saturation exponent, which varies from 1.8 to 4.0 but normally is 2.0
- Rw = formation water resistivity at formation temperature
- Φ = porosity
- m = cementation exponent, which varies from 1.7 to 3.0 but normally is 2.0
- Rt = true resistivity of the formation, corrected for invasion, borehole, thin bed, and other effects
without modification. To predict water saturation in rocks with non-Archie porosity, we modify the Archie equation.
Table of characteristics
The table below describes pore system shapes and other important characteristics of Archie and non-Archie rocks.[2]
Feature | Archie | Non-Archie |
---|---|---|
Pore system shapes | Intergranular (found between rounded particles); interparticle | Mold-like |
Intercrystalline (found between angular particles) | Vug-like | |
Fracture-like | ||
Relationship of pore shape to rock particles | Negative image of particles making up matrix | Relates only indirectly to particles making up matrix |
Pore connectivity | Pore throats connect pores into regular networks | Pores are irregularly distributed and can be either poorly or very well connected |
Porosity reduction processes | Grain coating or pore filling by calcite, silica, or dolomite | Pore or pore throat filling by clays or other minerals |
See also
- Pore system fundamentals
- Pore and pore throat sizes
- Connectivity and pore throat size
- Pore systems
- Capillary pressure (Pc) curves: pore throat size determination
References
- ↑ Choquette, P., W., Pray, L., C., 1970, Geologic nomenclature and classification of porosity in sedimentary carbonates: AAPG Bulletin, vol. 54, no. 2, p. 207–250. Classic reference for basic concepts regarding carbonate porosity.
- ↑ Coalson, E., B., Goolsby, S., M., Franklin, M., H., 1994, Subtle seals and fluid-flow barriers in carbonate rocks, in Dolson, J., C., Hendricks, M., L., Wescott, W., A., eds., Unconformity Related Hydrocarbons in Sedimentary Sequences: RMAG Guidebook for Petroleum Exploration and Exploitation in Clastic and Carbonate Sediments, p. 45–58.