Abstract: A Look at Carbonate Rocks

A. L. Bowsher

Important ore deposits are found in carbonate rocks, and large volumes of oil and gas are also produced from carbonate rocks on a worldwide basis. Reservoir types and productive capability are most often related to rock type and the facies to which the rock belongs. Broad new understanding of carbonate rocks came with the publication of Classification of Carbonate Rocks--A Symposium (AAPG Memoir 1, 1962).

The principal parameters of carbonate rocks are (1) chemical composition, (2) grade size, (3) sorting and packing, (4) identification of grains in the rock, (5) cement, (6) color, (7) alteration or recrystallization, and (8) porosity. Original porosity in carbonate rocks relates to kind and packing of original particles. Secondary porosity is reduced by infilling that usually relates to some particles, or is enhanced because some types of grains are dissolved. Carbonate sediments are organic detritus. The range of solubility of organic detritus is very large. Fossils present in the carbonates are clues as to the source of the detritus in the rock. Additional research is needed in faunal relations of facies and of rock types.

Ore recovery, well completion, and EOR are more successful when the parameters of carbonate rocks are extensively studied. A simplified approach to carbonate description is discussed.

AAPG Search and Discovery Article #90980©1994 AAPG Southwest Section Meeting, Ruidoso, New Mexico, April 24-26, 1994