DISCUSSION ON THE PRECIPITATION THEORY OF GYPSUM IN ACIDIZING TREATMENT TO THE GYPSIFEROUS RESERVOIR

In order to prevent effectively the precipitation of gypsum in acidizing treatment and to improve the result of acidizing treatment to the gypsiferous reservoir,this paper analyses and discusses systematically the physical and chemical mechanism of dissolution and precipitation of gypsum applying the chemical thermodynamics,chemical equilibrium and electrochemical theory.The results indicate that the precipitation of gypsum in acidizing treatment relates to the solubility of gypsum in the reservoir,which depends on the interactions among the temperature effect,plasma effect,salt effect,acid effect and solvent effect.Therefore,in order to prevent effectively the precipitation of gypsum,the synthetical study on the factors to influence the dissolution of gypsum in the reservoir is the first thing.