Experimental simulation of dolomite dissolution under burial diagenesis conditions and thermodynamic interpretation

Simulating experiments on dolomite dissolution by acetic acid were made under burial diagenesis conditions, at temperatures ranging from 75°C to 130° and pressures from 20 MPa to 30 MPa. The results show that the dissolution rate of dolomite increased rapidly with increasing temperature and pressure. From 75°C/20 MPa to 130°C/30 MPa, the total amount of released Ca and Mg increased from 32.98 mg/L to 337.9 mg/L, over one order of magnitude in difference. Thermodynamic calculation indicates that the increment of Gibbs free energy (△G) of the chemical reaction decreases with increasing temperature and pressure. This thermodynamic result is consistent with the experimental result. Based on the experimental results, it is suggested that secondary porosities formed by dolomite dissolution under conditions of deep burial diagenesis should be more common than those under epigenesis and shallow burial conditions, and therefore dolomite reservoirs in the formations that have been deeply buried should be more abundant than in the formations that have only been shallowly buried.