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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 (1959,1962) 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) Classification  

# Dunham (1962) Classification  

# Dunham (1962) 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.

* Wentworth (1922){{note|a}} [a]

* Wentworth (1922){{note|a}} [a]

* Bramkamp & Powers (1958)

* Bramkamp & Powers (1958)

* Folk (1959,1962)

* Folk (1959<ref name=Flk1959 />,1962)

* Dunham (1962)

* Dunham (1962)

* Leignton & Pendexter (1962)

* Leignton & Pendexter (1962)

* Wright (1992)

* Wright (1992)

* Hallsworth & Knox (1999)

* Hallsworth & Knox (1999)

Among all of the attempts, Folk (1959, 1962) and Dunham (1962) extended by Embry & Klovan (1971) classifications were widely accepted.  

Among all of the attempts, Folk (1959<ref name=Flk1959 />, 1962) and Dunham (1962) extended by Embry & Klovan (1971) classifications were widely accepted.  

==Folk Classification==  

==Folk Classification==  

===Folk’s Criteria===

===Folk’s Criteria===

Folk classification system is based on three basic components of limestone:  

[[w:Folk classification|Folk's classification]] system is based on three basic components of limestone:  

* Allochems (sediment grains): framework component of the rock. There are four major types of allochems in Folk system: intraclasts, oolites, fossils, and pellets.  

* Allochems (sediment grains): framework component of the rock. There are four major types of allochems in Folk system: intraclasts, oolites, fossils, and pellets.  

* Microcrystalline lime mud: matrix component of the rock < 4 μm in size.  

* Microcrystalline lime mud: matrix component of the rock < 4 μm in size.  

==Notes==  

==Notes==  

:1. {{note|a}} ^[a] Early carbonate classification is grain-size based system: Calcilutite (grains < 63 μm), calcarenite (63 μm < grains < 2mm), calcirudite (grains > 2mm).   

# [a] Early carbonate classification is grain-size based system: Calcilutite (grains < 63 μm), calcarenite (63 μm < grains < 2mm), calcirudite (grains > 2mm).   

 

# [b] This family has restricted limits because cement by itself cannot form a rock and the supported framework component (allochems) has limited packing.

2. ^[b] This family has restricted limits because cement by itself cannot form a rock and the supported framework component (allochems) has limited packing.

# [c] If the microcrystalline limestone had been disturbed either by bioturbation or soft-sediment deformation, the term “disturbed microcrystalline limestone” or “dismicrite” could be assigned.   

 

# [d] Examples of biolithites are: algal biolithite and coral biolithite.  

3. ^[c] If the microcrystalline limestone had been disturbed either by bioturbation or soft-sediment deformation, the term “disturbed microcrystalline limestone” or “dismicrite” could be assigned.   

# [e] Naming of a subdivision is a composite of two parts. The first part refers to the name of the allochem. The second part refers to the family type. For Example, intrasparite: intra- refers to intraclasts, and –sparite refers to family I.       

 

# [f] Oosparites are more common than Oomicrites because the need of strong current to form these rocks.  

4. ^[d] Examples of biolithites are: algal biolithite and coral biolithite.  

# [g] Intrasparites are more common than intramicrites because the need of strong current to transfer course rock fragments.  

 

# [h] Both biosparites and biomicrites are common. However, biosparites are usually more rounded and abraded because of the strong current.  

5. ^[e] Naming of a subdivision is a composite of two parts. The first part refers to the name of the allochem. The second part refers to the family type. For Example, intrasparite: intra- refers to intraclasts, and –sparite refers to family I.       

# [i] The subdivisions could be applied considering other types of allochems: intraclasts, oolites, and pellets.  

 

# [j] The abundance of grains defines the nature of the framework. In other words, whether it is mud-supported or grain-supported.  

6. ^[f] Oosparites are more common than Oomicrites because the need of strong current to form these rocks.  

# [k] The term “boundstone” is retained if the organic bounding type is not recognized.   

 

7. ^[g] Intrasparites are more common than intramicrites because the need of strong current to transfer course rock fragments.  

 

8. ^[h] Both biosparites and biomicrites are common. However, biosparites are usually more rounded and abraded because of the strong current.  

 

9. ^[i] The subdivisions could be applied considering other types of allochems: intraclasts, oolites, and pellets.  

 

10. ^[j] The abundance of grains defines the nature of the framework. In other words, whether it is mud-supported or grain-supported.  

 

11. ^[k] The term “boundstone” is retained if the organic bounding type is not recognized.   

 

20. ^ [3] [4] [5] [9] Folk Classification. Wikipedia. https://en.wikipedia.org/wiki/Folk_classification#cite_ref-2

20. ^ [3] [4] [5] [9] Folk Classification. Wikipedia. https://en.wikipedia.org/wiki/Folk_classification#cite_ref-2