Study On Dynamic Prediction Of Ground Subsidence Of Underground Salt Reservoirs And Optimal Allocation Of Cavities

Salt rock has high tightness,low permeability and excellent deformation characteristics,so it can be used as a storage medium for oil,natural gas and other energy materials.The construction process of salt rock underground storage reservoir is relatively easy,the construction difficulty is relatively small,and the input cost is relatively low.Although salt rock reservoir has many advantages,it also has many potential risks due to its special physical and mechanical properties,changes of peri-chamber pressure and high in-situ stress during the operation of salt rock reservoir.The ground subsidence in the underground storage area of salt rock is a frequent event among numerous storage accidents,and many other types of accidents will also cause the ground subsidence in the storage area,and it is intuitive and effective for the monitoring and control of the ground subsidence,so it is necessary to conduct further research on the ground subsidence.In addition,in the construction of salt rock reservoir,key factors such as cavity shape,pillar size and cavity group configuration mode all play an important role in the stability of the reservoir.The distribution and combination of many factors should also be studied in depth to achieve the predetermined engineering effect.On the background of Juancheng salt mining project in southwest Shandong province,this paper studies the land subsidence and optimal configuration of cavity group in the study area by means of theoretical analysis,laboratory test,numerical simulation and mathematical modeling.The conclusions are as follows:1)Based on all kinds of mechanical test results of similar model materials,the obtained similar materials are similar to the original rock,which can reflect the mechanical properties of the original rock.Through statistical analysis and parameter optimization study,it can be found that the mechanical parameters of mudstone,salt rock and salt rock interlayer after optimization are less discrete than the data before optimization.2)Based on the data obtained from the similar model test,the numerical simulation analysis is carried out.It can be obtained through calculation that the horizontal deformation caused by the plastic deformation and late creep of salt rocks is far less than the vertical deformation.The numerical simulation results and analysis conclusions provide a theoretical basis for the establishment of the land subsidence prediction model.3)Based on maximum deformation theory and the limitation of convergence theory,land subsidence dynamic prediction model is set up,respectively,according to the different theoretical assumptions of the two models,this paper expounds the two advantage range of land subsidence dynamic prediction model is:when the settlement of the early stage of the storage reservoir prediction,selection should be aging convergence theory for the settlement of model,and store late sedimentation in reservoir prediction,should choose the maximum deformation theory to obtain the subsidence model.4)Swarm optimization selection cavity configuration must introduce key factors:cavity shape,pillar width,gas pressure,based on the yield close to degree index to calculation of 75 set of conditions,will eventually have to adopt the adjacent Angle is 120 ° hexagonal cavity group arrangement,its volume is the smallest of the most"dangerous area",under the condition of meet the repository closure rule,cavity operation pressure,the better for the stability of surrounding rock,the greater the repository operation pressure is very small,arrangement of cavity group of significant effects on the stability of surrounding rock,when the operating pressure is greater than 5 MPa,cavity group arrangement form and the pillar width effects on the stability of surrounding rock are weakened.