Simulation experiment of water-rock interaction in Silurian mudstone cap formation and its significance in Southeast Sichuan Basin

The influence of water-rock interaction of cap rock on reservoir formation and hydrocarbon preservation under different environments was analyzed with simulation experiment of water-rock interaction.The mudstone cap rock samples from the Silurian Longmaxi Formation in the Southeast Sichuan Basin were selected to react with freshwater and acetic fluid under different temperature and pressure conditions of 30℃,1 MPa;80℃,20 MPa and 160℃,40 MPa,respectively.Under normal temperature and pressure,the interaction between mudstone and fresh water was very weak,suggesting that the interaction was not destructive to cap rock under weak hydrodynamic force;however,acetic fluid under high temperature and pressure was more destructive than fresh water under normal conditions.Yet the solubility of mudstone was much lower than that of carbonate under the same conditions.In the study area,when hydrothermal fluid moved,more fluid was occluded in carbonate and reacted with rock because of low permeability and solubility of the Silurian mudstone.