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| ==Pore types== | | ==Pore types== |
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| + | [[file:porosity_fig2.png|thumb|{{figure number|2}}Idealized sandstone porosity system showing four basic pore types: intergranular, microporosity, dissolution, and fracture. (After <ref name=pt05r127 />.)]] |
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| Basic clastic and carbonate pore types can be identified by integrating data from [[core description]]s, thin section petrography, scanning electron microscopy, and [[capillary pressure]] tests. These analyses indicate that significant differences exist between clastic and carbonate pore types. | | Basic clastic and carbonate pore types can be identified by integrating data from [[core description]]s, thin section petrography, scanning electron microscopy, and [[capillary pressure]] tests. These analyses indicate that significant differences exist between clastic and carbonate pore types. |
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| + | [[file:porosity_fig3.png|left|thumb|{{figure number|3}}Idealized carbonate porosity system showing three basic porosity groups: fabric selective, not fabric selective, and fabric selective or not. (After <ref name=pt05r34 />.)]] |
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| ===Sandstone pore systems=== | | ===Sandstone pore systems=== |
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− | Four basic porosity types can be recognized in sandstones<ref name=pt05r127>Pittman, E. D., 1979, Porosity, diagenesis, and productive capability of sandstone reservoirs, in Scholle, P. A., Schluger, P. R., eds., Aspects of Diagenesis: Society Economic Paleontologists and Mineralogists Special Publication 26, p. 159–173.</ref>: (1) intergranular (primary), (2) microporosity, (3) dissolution (secondary), and (4) fracture (Figure 2). Intergranular porosity exists as space between detrital grains. Microporosity exists as small pores (less than 2 μm) commonly associated with detrital and authigenic clay minerals. Dissolution porosity is the pore space formed from the partial to complete dissolution of framework grains and/or cements. Fracture porosity is the void space associated with natural fractures. | + | Four basic porosity types can be recognized in sandstones<ref name=pt05r127>Pittman, E. D., 1979, Porosity, diagenesis, and productive capability of sandstone reservoirs, in Scholle, P. A., Schluger, P. R., eds., Aspects of Diagenesis: Society Economic Paleontologists and Mineralogists Special Publication 26, p. 159–173.</ref>: (1) intergranular (primary), (2) microporosity, (3) dissolution (secondary), and (4) fracture ([[:file:porosity_fig2.png|Figure 2]]). Intergranular porosity exists as space between detrital grains. Microporosity exists as small pores (less than 2 μm) commonly associated with detrital and authigenic clay minerals. Dissolution porosity is the pore space formed from the partial to complete dissolution of framework grains and/or cements. Fracture porosity is the void space associated with natural fractures. |
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− | [[file:porosity_fig2.png|thumb|{{figure number|2}}Idealized sandstone porosity system showing four basic pore types: intergranular, microporosity, dissolution, and fracture. (After <ref name=pt05r127 />.)]]
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| ===Carbonate pore systems=== | | ===Carbonate pore systems=== |
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− | In comparison to clastic pore systems, pore types in carbonate rocks are more varied (see “Carbonate Reservoir Models”). Three basic pore groups can be recognized<ref name=pt05r34>Choquette, P. W., Pray, L. C., 1970, Geological nomenclature and classification of porosity in sedimentary carbonates: AAPG Bulletin, v. 54, p. 207–250.</ref>: fabric selective, not fabric selective, and fabric selective or not (Table 1 and Figure 3). Seven porosity types (interparticle, intraparticle, intercrystal, moldic, fenestral, fracture, and vugs) are common and volumetrically important. | + | In comparison to clastic pore systems, pore types in carbonate rocks are more varied (see “Carbonate Reservoir Models”). Three basic pore groups can be recognized<ref name=pt05r34>Choquette, P. W., Pray, L. C., 1970, Geological nomenclature and classification of porosity in sedimentary carbonates: AAPG Bulletin, v. 54, p. 207–250.</ref>: fabric selective, not fabric selective, and fabric selective or not (Table 1 and [[:file:porosity_fig3.png|Figure 3]]). Seven porosity types (interparticle, intraparticle, intercrystal, moldic, fenestral, fracture, and vugs) are common and volumetrically important. |
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| {| class = "wikitable" | | {| class = "wikitable" |
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| | Porosity produced by sediment shrinkage | | | Porosity produced by sediment shrinkage |
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− | [[file:porosity_fig3.png|thumb|{{figure number|3}}Idealized carbonate porosity system showing three basic porosity groups: fabric selective, not fabric selective, and fabric selective or not. (After <ref name=pt05r34 />.)]]
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| Although fracture porosity is very common in carbonate rocks, it is generally less than 1% of the bulk volume in both clastic and carbonate reservoirs. | | Although fracture porosity is very common in carbonate rocks, it is generally less than 1% of the bulk volume in both clastic and carbonate reservoirs. |