Study On Stability And Sealing Of Surrounding Rock Of Deep Anhydrite Cavern

Petroleum is an important energy source for modern industry,which is of great significance to China’s economic development and national defense security.However,China’s dependence on foreign oil has always been high,and the import volume is increasing year by year,which has become a major energy problem.In order to guarantee the long-term stability of oil supply,the construction of petroleum strategic reserve system is imperative.However,the existing petroleum storage methods are difficult to meet the strategic petroleum reserve requirements because of high engineering cost or harsh site selection conditions.Therefore,some scholars put forward a new idea of oil storage,that is,to use the abandoned anhydrite goaf for oil storage.According to the storage requirements,anhydrite mined-out area should meet the three principles of stability,tightness and no interaction with oil.However,according to the existing research results,most studies in this field focus on the stability of anhydrite mined-out area,and few studies involve tightness.Based on China’s anhui province hengtai hard gypsum mine engineering,through indoor experiment and numerical simulation mainly explores the anhydrite in destroying the permeability in the process of change,analyzed the anhydrite mined-out area after completion of the excavation and different storage pressure stability and sealing,demonstrates the feasibility of using the abandoned goaf storage anhydrite.The main research contents of this paper are as follows:（1）The triaxial compression seepage test and acoustic emission test were designed and carried out to obtain the stress-strain curve and permeability coefficient of anhydrite samples during the test process.Based on this,the permeability coefficient-strain curve was drawn and the empirical formula of permeability coefficient-strain was constructed.At the same time,the change mechanism of the permeability of anhydrite during the experiment is analyzed,and the change rule of the permeability of anhydrite is discussed.（2）On the basis of engineering data and test data,numerical simulation of anhydrite goaf after excavation was carried out by FLAC^3D software.The overall stability of goaf after excavation was evaluated,and the sealing property of anhydrite goaf was analyzed according to the established empirical formula of permeability coefficient and strain.Finally,it is considered that the anhydrite mined-out area after excavation has better stability and tightness.（3）According to the excavation calculation results of the numerical model and the actual oil storage state of the cavity,further research is carried out on the anhydrite goaf under the condition of oil storage.The distribution of maximum principal stress,minimum principal stress,horizontal displacement,vertical displacement and plastic zone of anhydrite goaf under different storage pressures is discussed respectively,and the overall stability and tightness of goaf under different storage pressures are evaluated.The results show that the stability and tightness of anhydrite goaf are good during oil storage.