Study On Stability Evaluation Of Salt Rock Gas Storage Cavern With Interlayer

Salt Salt rock gas storage reservoirs with interlayer are used for seasonal peaking and emergency gas supply because of their strong sealing and fast injection and extraction rate,which can effectively alleviate the problem of "gas shortage" of natural gas in winter and guarantee the energy security of the country with strategic reserve of oil and gas resources.However,in recent years,the instability of salt-rock gas storage reservoirs has been frequent,causing serious accidents such as gas leakage and explosion,facility damage,casualties and other serious accidents,which have affected the stable social order and caused huge losses.Therefore,it is important to evaluate the stability of the cavity under the influence of the interlayer to ensure the stable operation of salt storage reservoirs.In view of this,this thesis investigates the cavities in salt rock gas storage reservoirs with interburden,analyzes the factors of cavity instability,constructs a targeted evaluation index system,and then establishes a reliable mathematical evaluation model,so as to provide suggestions for ensuring the stability of cavities.The main research contents and results obtained are as follows:(1)Study on the extraction of instability factors and influence law of dissolved cavity.Theoretical study on the nature of salt rock and interlayer,investigation of the main causes of instability accidents in salt rock gas storage,analysis of the accident site,and identification of instability factors;numerical simulation calculation of the parameters of salt rock gas storage affected by interlayer,and clarification of the conditions under the influence of temperature for each parameter to cause the instability of the dissolved cavity.(2)Construction of stability assessment index system.All factors that may cause cavity instability are analyzed one by one,and a comprehensive stability assessment index system is constructed for the cavity of salt rock reservoirs with interlayer by eliminating redundant indexes on the basis of the principles followed in constructing the assessment index system.(3)Establishment of analytical model for cavity stability assessment.A practical new weight assignment method is constructed,which can weaken the strong subjective interference caused by expert knowledge and experience differences,and consider the importance of indicators and the degree of mutual influence to ensure the accuracy of weight assignment.The efficacy coefficient method is introduced to accurately assess the stability of the cavity in the gas storage reservoir containing sandwich salt rock;finally,the reliability of the method is verified by using actual engineering data.(4)The control measures of dissolved cavity instability are proposed.Based on the evaluation model,control measures are proposed in accordance with the cavity state monitoring,operation parameter selection,adjustment and maintenance from two stages,including the cavity construction and operation periods,to provide a reference for the safety management of gas storage reservoirs containing intercalated salt rocks.The above analysis shows that the numerical simulation and evaluation methods used have operability and engineering application value,which can provide new references for practical work.Further studies on the optimization of parameters of gas storage reservoirs containing interbedded salt rocks can be done later.