Thermodynamic Analysis of Burial Dissolution of Carbonate Rocks and Its Geological ignificance

Carbonate burial dissolution in nature is water-rock interaction under certain of temperature and pressure.By analyzing the Gibbs free energy(ΔG) of calcite and dolomite dissolution reaction,this paper pointed out that ΔG initially decreased and then increased with temperature increasing gradually at 25～200℃.The dissolution mostly occurred as temperature equaling to 115～140℃.Then carbonate dissolving became difficult when temperature was more than 140℃ due to precipitation.But the impact of pressure on dissolution was relatively small.Especially,when the pressure was over 15 MPa,its impact could be neglected.At the same burial depth,dolomite is dissolved more easily than calcite.In addition,the ΔG also decreased firstly and then increased,followed by reaching to minimum at the depth of 4 300～5 000 m.That means the burial dissolution occurred most easily.It provides theoretical basis for looking for good reservoirs.