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==Pore types==

==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.

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.

===Sandstone pore systems===

===Sandstone pore systems===

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.

 

===Carbonate pore systems===

===Carbonate pore systems===

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.

{| class = "wikitable"

{| class = "wikitable"

| Porosity produced by sediment shrinkage

| Porosity produced by sediment shrinkage

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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.