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In oil and gas industry, classifying carbonate rocks is a major step in core and thin section description. Two classification systems have been widely used in the industry:  

In oil and gas industry, classifying carbonate rocks is a major step in core and thin section description. Two classification systems have been widely used in the industry:  

# Folk (1959<ref name=Flk1959>Folk, R. L., 1959, [https://archives.datapages.com/data/bulletns/1957-60/data/pg/0043/0001/0000/0001.htm Practical petrographic classification of limestones]: AAPG Bulletin, v. 43, p. 1–38.</ref>, 1962<ref name=Flk1962>Folk, R.L., 1962, Spectral subdivision of limestone types, in Ham, W.E., ed., Classification of carbonate Rocks-A Symposium: American Association of Petroleum Geologists Memoir 1, p. 62-84.</ref>) Classification  

# Folk (1959<ref name=Flk1959>Folk, R. L., 1959, [https://archives.datapages.com/data/bulletns/1957-60/data/pg/0043/0001/0000/0001.htm Practical petrographic classification of limestones]: AAPG Bulletin, v. 43, p. 1–38.</ref>, 1962<ref name=Flk1962>Folk, R. L., 1962, [https://archives.datapages.com/data/specpubs/carbona2/data/a038/a038/0001/0050/0062.htm Spectral subdivision of limestone types], ''in'' W. E. Ham, ed., Classification of carbonate Rocks-A Symposium: [https://archives.datapages.com/data/alt-browse/aapg-special-volumes/m1.htm AAPG Memoir 1], p. 62-84.</ref>) Classification  

# Dunham (1962<ref name=Dnhm>Dunham, R. J., 1962, Classification of carbonate rocks according to depositional texture, in Ham, W. E., ed., Classification of Carbonate Rocks: AAPG Memoir 1, p. 108–121.</ref>) Classification  

# Dunham (1962<ref name=Dnhm>Dunham, R. J., 1962, [https://archives.datapages.com/data/specpubs/carbona2/data/a038/a038/0001/0100/0108.htm Classification of carbonate rocks according to depositional texture], ''in'' W. E. Ham, ed., Classification of Carbonate Rocks: [https://archives.datapages.com/data/alt-browse/aapg-special-volumes/m1.htm AAPG Memoir 1], p. 108–121.</ref>) Classification  

Both classifications provide an indication of depositional energy setting and reservoir quality.

Both classifications provide an indication of depositional energy setting and reservoir quality.

* Pelmicrite: consists of pellets with microcrystalline matrix (Figure 10).

* Pelmicrite: consists of pellets with microcrystalline matrix (Figure 10).

<gallery mode=packed heights=300px widths=300px>

<gallery mode=packed heights=300px widths=300px>

File:GeoWikiWriteOff2021-Abdulwahab-Figure7.png|{{figure number|7}}Intramicrite<ref>SEPM Strata, 2021, [http://sepmstrata.org/microscopic_gallery_details.aspx?gid=165&pg=1&gcid=9 Microscopic Gallery]</ref>

File:GeoWikiWriteOff2021-Abdulwahab-Figure7.png|{{figure number|7}}Intramicrite<ref>[http://sepmstrata.org/microscopic_gallery_details.aspx?gid=165&pg=1&gcid=9 SEPM Strata Microscopic Gallery]</ref>

File:GeoWikiWriteOff2021-Abdulwahab-Figure8.png|{{figure number|8}}Oomicrite  

File:GeoWikiWriteOff2021-Abdulwahab-Figure8.png|{{figure number|8}}Oomicrite<ref>[http://www.sepmstrata.org/microscopic_gallery_details.aspx?gid=207&pg=3&gcid=11 SEPM Strata Microscopic Gallery]</ref>

File:GeoWikiWriteOff2021-Abdulwahab-Figure9.png|{{figure number|9}}Biomicrite

File:GeoWikiWriteOff2021-Abdulwahab-Figure9.png|{{figure number|9}}Biomicrite

File:GeoWikiWriteOff2021-Abdulwahab-Figure10.png|{{figure number|10}}Pelmicrite

File:GeoWikiWriteOff2021-Abdulwahab-Figure10.png|{{figure number|10}}Pelmicrite

==Dunham Classification==  

==Dunham Classification==  

===Dunham’s Criteria===

===Dunham’s Criteria===

Dunham classification system is based on three depositional textural features:

[[w:Dunham classification|Dunham's classification system]] is based on three depositional textural features:

* The presence or absence of lime mud.

* The presence or absence of lime mud.

* The abundance of grains.[j]  

* The abundance of grains.[j]  

===Extended Dunham Classification (1971)===

===Extended Dunham Classification (1971)===

Embry and Klovan<ref name=EmbryKlvn /> expanded the original Dunham classification due to the lack of:

Embry and Klovan<ref name=EmbryKlvn /> expanded the original Dunham classification due to the lack of:

* Classifying coarse-grained (>2mm) rocks.  

* Classifying coarse-grained (>2mm) rocks.  

* Subdividing organically-bound rocks (boundstones).  

* Subdividing organically-bound rocks (boundstones).  

The extended Dunham Classification is shown in Figure 18.  

The extended Dunham Classification is shown in Figure 18.  

====Coarse-Grained Rocks Classification====

====Coarse-Grained Rocks Classification====

* Floatstone: a matrix-supported rock with > 10% of grains >2mm and original components are not organically bounded together during deposition (Figure 19).   

* Floatstone: a matrix-supported rock with > 10% of grains >2mm and original components are not organically bounded together during deposition (Figure 19).   

* Rudstone: a grain-supported rock with > 10% of grains >2mm and original components are not organically bounded together during deposition (Figure 20).

* Rudstone: a grain-supported rock with > 10% of grains >2mm and original components are not organically bounded together during deposition (Figure 20).

====Organically-Bound Rocks Subdivision====

====Organically-Bound Rocks Subdivision====

* Bafflestone: in situ organically-bound rock in which organisms act as baffles (Figure 21).

* Bafflestone: in situ organically-bound rock in which organisms act as baffles (Figure 21).

* Bindstone: in situ organically-bound rock in which organisms encrust and bind (Figure 22).

* Bindstone: in situ organically-bound rock in which organisms encrust and bind (Figure 22).

* Framestone: in situ organically-bound rock in which organisms build a rigid framework (Figure 23).[k]

* Framestone: in situ organically-bound rock in which organisms build a rigid framework (Figure 23).[k]

===Depositional Energy Setting and Reservoir Quality Indications===

===Depositional Energy Setting and Reservoir Quality Indications===

Rudstones and framestones are usually formed in high-energy settings (above wave base).  

Rudstones and framestones are usually formed in high-energy settings (above wave base).  

Organically-bound rocks show good reservoir quality if the skeletal growth is interconnected.

Organically-bound rocks show good reservoir quality if the skeletal growth is interconnected.

==Notes==  

==Notes==  

==Other Sources==  

==Other Sources==  

* Gregg, Jay. (December 18). Limestone Petrology. Missouri S&T. https://web.mst.edu/~greggjay/carbonate_page/lsgallery/pages/c-ACS190_10.htm

* Gregg, Jay. (December 18). Limestone Petrology. Missouri S&T. https://web.mst.edu/~greggjay/carbonate_page/lsgallery/pages/c-ACS190_10.htm

* Sahraeyan, Mohammad. (2013, June). Sedimentary Basin Analysis of Sachun Formation in Southwestern Iran: Implication for Sedimentary Environments and Tectonic Setting. ResearchGate. https://www.researchgate.net/figure/Photomicrographs-showing-micrite-and-pelmicrite-in-the-argillaceous-limestone-facies-of_fig8_262337097

* Sahraeyan, Mohammad. (2013, June). Sedimentary Basin Analysis of Sachun Formation in Southwestern Iran: Implication for Sedimentary Environments and Tectonic Setting. ResearchGate. https://www.researchgate.net/figure/Photomicrographs-showing-micrite-and-pelmicrite-in-the-argillaceous-limestone-facies-of_fig8_262337097

* K. Bjørlykke (ed). Petroleum Geoscience: From Sedimentary Environments to Rock Physics, DOI 10.1007/978-3-642-34132-8_5, Ⓒ Springer-Verlag Berlin Heidelberg 2015.

* K. Bjørlykke (ed). Petroleum Geoscience: From Sedimentary Environments to Rock Physics, DOI 10.1007/978-3-642-34132-8_5, Ⓒ Springer-Verlag Berlin Heidelberg 2015.

* Ardakani, Omid H. (2013, June). Diagenetic evolution and associated mineralization of Middle Devonian carbonates, southwestern Ontario, Canada. ResearchGate. https://www.researchgate.net/figure/Thin-section-photomicrographs-of-Middle-Devonian-rocks-A-Syntaxial-and-equant-calcite_fig3_235413575

* Ardakani, Omid H. (2013, June). Diagenetic evolution and associated mineralization of Middle Devonian carbonates, southwestern Ontario, Canada. ResearchGate. https://www.researchgate.net/figure/Thin-section-photomicrographs-of-Middle-Devonian-rocks-A-Syntaxial-and-equant-calcite_fig3_235413575

* Al-Awwad, Saad F. & pomar, Luis. (2015, May 21). Origin of the rudstone–floatstone beds in the Upper Jurassic Arab-D reservoir, Khurais Complex, Saudi Arabia. ScienceDirect. https://www.sciencedirect.com/science/article/pii/S0264817215001634

* Al-Awwad, Saad F. & pomar, Luis. (2015, May 21). Origin of the rudstone–floatstone beds in the Upper Jurassic Arab-D reservoir, Khurais Complex, Saudi Arabia. ScienceDirect. https://www.sciencedirect.com/science/article/pii/S0264817215001634

* Khanaqa, Polla. (2018, December). Stratigraphy and Facies Analysis of the Govanda Formation from Western Zagros, Kurdistan Region, Northeastern Iraq. ResearchGate. https://www.researchgate.net/figure/a-Photo-of-the-Coral-

* Khanaqa, Polla. (2018, December). Stratigraphy and Facies Analysis of the Govanda Formation from Western Zagros, Kurdistan Region, Northeastern Iraq. ResearchGate. https://www.researchgate.net/figure/a-Photo-of-the-Coral-Bafflestone-of-Barda-Balaka-Outcrop-Between-the-stems-Fine_fig12_330094098

Bafflestone-of-Barda-Balaka-Outcrop-Between-the-stems-Fine_fig12_330094098

* Bindstone. Bureau of Economic Geology. https://www.beg.utexas.edu/lmod/_IOL-CM02/st21-ancbindstone.htm

* Bindstone. Bureau of Economic Geology. https://www.beg.utexas.edu/lmod/_IOL-CM02/st21-ancbindstone.htm

* Camuera, Jon. (2014, July). Origin and palaeo-environmental significance of the Berrazales carbonate spring deposit, North of Gran Canaria Island, Spain. ResearchGate. https://www.researchgate.net/figure/A-Framestone-facies-composed-of-parallel-plant-moulds-coated-with-calcite-B-Plant_fig4_283498781

* Camuera, Jon. (2014, July). Origin and palaeo-environmental significance of the Berrazales carbonate spring deposit, North of Gran Canaria Island, Spain. ResearchGate. https://www.researchgate.net/figure/A-Framestone-facies-composed-of-parallel-plant-moulds-coated-with-calcite-B-Plant_fig4_283498781

* Lokier, Stephen W.; Al Junaibi, Mariam (2016). "The petrographic description of carbonate facies: are we all speaking the same language?". Sedimentology. 63 (7): 1843–1885. doi:10.1111/sed.12293

* Lokier, Stephen W.; Al Junaibi, Mariam (2016). "The petrographic description of carbonate facies: are we all speaking the same language?". Sedimentology. 63 (7): 1843–1885. doi:10.1111/sed.12293