Safety Evaluation And Treatment Of Annular Casing Pressure In Injection/production Wells Of Suqiao Underground Gas Storage

The Suqiao underground gas storage group is located in the hinterland of Beijing-Tianjin-Hebei.Currently,22 injection/production wells in use have annular casing pressure,which seriously affects the smooth operation of the UGS.Due to the alternate operation mode of injection and production of the UGS,the formation pressure and the force of the pipe string show periodic changes,and the safety of the annular casing pressure cannot be fully evaluated according to the safety evaluation method of traditional natural gas wells.This paper investigates the algorithm of the MAWOP recommended by the current international standards,and analyzes the adaptability of the algorithm with reference to the force of the pipe string and the change of the liquid level in the annulus under different working conditions.The author calculate the pressure around the packer and check the strength of the pipe string,optimize the existing algorithm,and then obtain the dynamic calculation method of the MAWOP of the UGS well.The author carries out the dynamic safety evaluation of the Suqiao injection/production wells.And refer to the evaluation results,the author proposes the Suqiao gas storage suggestions on the management and governance of wells with annular casing pressure.By establishing a mathematical model,the process parameters of the annulus nitrogen injection to relieve pressure fluctuations are optimized,and field tests are carried out.The research results show that among the three current international standards,the recommended algorithm of API RP 90-2 is more comprehensive.But combined with the analysis of the force of the pipe string and the change of working conditions,this method is not fully applicable to the injection/production well of the UGS.Because the B/C annulus is hardly affected by the changes of the working conditions,the API RP90-2 algorithm is used to statically calculate the outer annulus to obtain the MAWOP.To the A annulus,the wellbore string stress,and pressure changes refers to the injection and production conditions,dynamic calculation is nessary.Take the minimum value of both statically and dynamic calculating results as the MAWOP.The dynamic evaluation results of the injection/production wells in the Suqiao UGS show that the current annular pressure value of wells is higher than the MAWOP,and the risk of continuously producting is very high.The current annular pressure value of 5 wells is close to the safety limit,and the annular pressure of 9 wells is caused by alternating injection and production conditions.It is a normal phenomenon.It is recommended to inject nitrogen into the casing annular during the completion operation to reduce the annular pressure fluctuation caused by the change of conditions.The research conclusions of this paper provide a theoretical basis for the follow-up treatment of wells with ACP of the Suqiao UGS,and have practical significance for ensuring the safe and stable operation of the Suqiao UGS.