Sigra measures the amount of carbonate in crushed coal samples (usually from coal desorption or isotherm tests) by acid reaction and titration. The results of testing are presented in terms of mass of equivalent calcium carbonate removed.
Carbonates contained in cleats may block them and restrict permeability. If the cleat carbonate can be removed by acid leaching, the amount of carbonate removed is then determined by titration of the leachate.
In addition the core is examined to determine from which cleats or bedding planes the carbonate has been removed. This information can be used in combination with coal modulus and stress information to arrive at the expected de-stressing of the coal that would be achieved by solution of carbonates.
Carbonate filled cleats in a coal core