Thermodynamic calculation of feldspar dissolution and the significance on research of clastic reservoir. Geological Bulletin of China,

Based on the calculation of Gibbs free energy increment (ΔG), this paper probes into the thermodynamic feature during the dissolution process of three feldspar components transforming into kaolinite or illite. It’s indicated that K-feldspar, albite and anorthite conversion to kaolinite and illite respectively are all spontaneous reaction. Lowest Gibbs free energy increment and high positive temperature is required for anorthite dissolution reaction which demonstrates that albite is most instable and easily to be decomposed under low temperature condition, while highest Gibbs free energy increment is required for K-feldspar as well as negative temperature, which shows higher stability of K-feldspar. Medium Gibbs free energy increment and temperature is required for Albite, but when the temperature goes up, its stability drops down. Compared to temperature, pressure has no obviously effect on the Gibbs free energy increment. Therefore, the secondary porosity, especially which formed in burial diagenesis environment, is strongly related to the K-feldspar, secondly albite. However, certain cushioning is imposed by the transforming process from smectite to illite conversion, which leads to less dissolution under burial diagenesis condition albite dissolution and possibly albitization or autogenous albite precipitation.