EESC07H3 Lecture Notes - Lecture 7: Carbonate Rock, Calcite, Aquifer
13 Feb 2018
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Fracturing done by pressure release is 3, not regional. Including clastic and chemically precipitated rocks containing of calcite, dolomite, and minor amounts of clay. Less susceptible to solution because it doesn"t dissolve as readily. Porosities of carbonate rocks are ~20% for coarse blocky limestone, and and >50% for less well cemented chalks. Due to the pore size, most carbonates have a very low primary (intergranular) permeability, < 10-5 cm/s (not aquifer material), but good for aquitard/aquiclude. Most carbonates have a significant secondary permeability due to the enlargement of fractures and bedding planes by chemical solutions: caco3 + h2o + co2 ca2+ + 2(hco3)- (carbonic acid). Co2 is from the microorganisms in soil. A lot of co2 gets taken up by water as it permeates through soil. This then can dissolve the rock and creates the carbonate/dolomite into an aquifer.
