Changes

The majority of carbonate sediments are produced in shallow, warm ocean waters by extraction of calcium carbonate from seawater by organisms to form their shells or skeletal material. The sediments are composed of a spectrum of sizes and pore geometries. The Dunham classification (Figure 1) describes depositional textures in a manner that can be related to pore geometries. The grain-supported textures tend to have larger pore sizes than do mud-supported textures. The textures have different geometries in different depositional environments.

The majority of carbonate sediments are produced in shallow, warm ocean waters by extraction of calcium carbonate from seawater by organisms to form their shells or skeletal material. The sediments are composed of a spectrum of sizes and pore geometries. The Dunham classification (Figure 1) describes depositional textures in a manner that can be related to pore geometries. The grain-supported textures tend to have larger pore sizes than do mud-supported textures. The textures have different geometries in different depositional environments.

[[file:carbonate-reservoir-models-facies-diagenesis-and-flow-characterization_fig1.png|thumb|{{figure number|1}}<ref name=pt06r29>Dunham, R. J., 1962, Classification of carbonate rocks according to depositional texture, in, Classifications of Carbonate Rocks—A Symposium: AAPG Memoir 1, p. 108–121.</ref>) classification of carbonate rocks according to depositional texture. (From <ref name=pt06r138>Swanson, R. G., 1981, Sample examination manual: AAPG Methods in Exploration Series, 65 p.</ref>.)]]

[[file:carbonate-reservoir-models-facies-diagenesis-and-flow-characterization_fig1.png|thumb|{{figure number|1}}Dunham<ref name=pt06r29>Dunham, R. J., 1962, Classification of carbonate rocks according to depositional texture, in, Classifications of Carbonate Rocks—A Symposium: AAPG Memoir 1, p. 108–121.</ref> classification of carbonate rocks according to depositional texture. (From <ref name=pt06r138>Swanson, R. G., 1981, Sample examination manual: AAPG Methods in Exploration Series, 65 p.</ref>.)]]

There are five basic carbonate depositional environments. From shore to basin, they are ''peritidal'' (tidal flat), ''shallow shelf interior, shelf margin complex, slope'', and ''basin'' (Figure 2).

There are five basic carbonate depositional environments. From shore to basin, they are ''peritidal'' (tidal flat), ''shallow shelf interior, shelf margin complex, slope'', and ''basin'' (Figure 2).

===Petrophysical classification of carbonate pore space===

===Petrophysical classification of carbonate pore space===

The <ref name=pt06r5>Archie, G. E., 1952, Classification of carbonate reservoir rocks and petrophysical considerations: AAPG Bulletin, v. 36, p. 278–298.</ref>) classification was the first attempt at relating rock fabrics to petrophysical rock properties. <ref name=pt06r79>Lucia, F. J., 1983, Petrophysical parameters estimated from visual descriptions of carbonate rocks—a field classification of carbonate pore space: Journal of Petroleum Technology, March, p. 629–637.</ref>) improved on the Archie classification by defining the pore size distribution in relationship to the particle size and the spatial relationship of the pore space to the particles.

The Archie<ref name=pt06r5>Archie, G. E., 1952, Classification of carbonate reservoir rocks and petrophysical considerations: AAPG Bulletin, v. 36, p. 278–298.</ref> classification was the first attempt at relating rock fabrics to petrophysical rock properties. Lucia<ref name=pt06r79>Lucia, F. J., 1983, Petrophysical parameters estimated from visual descriptions of carbonate rocks—a field classification of carbonate pore space: Journal of Petroleum Technology, March, p. 629–637.</ref> improved on the Archie classification by defining the pore size distribution in relationship to the particle size and the spatial relationship of the pore space to the particles.

''Interparticle porosity'' (<ref name=pt06r79 />) is defined as that pore space located between grains (intergranular porosity) or between crystals (intercrystalline porosity), but which is not significantly larger than the grains or crystals. ''Vuggy porosity'' is defined as pore space larger than or within rock particles. Isolated vugs are called ''separate vugs'', while vugs that form a connected pore system on a reservoir scale are called ''touching vugs''. (For more information on porosity, see the chapter on “[[Porosity]]” in Part 5.)

''Interparticle porosity''<ref name=pt06r79 /> is defined as that pore space located between grains (intergranular porosity) or between crystals (intercrystalline porosity), but which is not significantly larger than the grains or crystals. ''Vuggy porosity'' is defined as pore space larger than or within rock particles. Isolated vugs are called ''separate vugs'', while vugs that form a connected pore system on a reservoir scale are called ''touching vugs''. (For more information on porosity, see the chapter on “[[Porosity]]” in Part 5.)

===Rock fabric and petrophysical property relationships===

===Rock fabric and petrophysical property relationships===