Study On The Effect Of Loading Pressure On The Integrity Of Cement Sheath In Gas Storage

The gas storage is an artificial gas reservoir formed by reintroducing the natural gas that has been taken into the abandoned oil or gas field,which plays an important role in the supply and reserve of natural gas.The cement sheath is one of the important barriers to the wellbore integrity of the injection and production wells.The mechanical integrity of the well is seriously affected by the life cycle and safety of the injection and production wells.It is very important to study the effect of injection load change on the integrity of cement sheath,which is very important to improve the annular sealing capacity of cement ring in gas storage and production wells and effectively ensure the wellbore integrity of injection wells.In this paper,the model of casing-cement sheath-well wall rock is established,and the sealing integrity of cement sheath is determined by theoretical calculation.Then the cement sheath under different cyclic stress environment is taken as the experimental object to study the influence of the change of injection load on the integrity of cement sheath seal.In order to improve the carrying capacity of the cement sheath,the mechanical properties of the cement sheath to improve the cement sheath to ensure long-term sealing capacity.On the basis of theoretical research and experimental research,this paper has formed the following conclusions:(1)The evaluation model of cement sheath seal integrity considering initial stress,wellbore pressure,ground stress and temperature is established.The theoretical evaluation model was used to evaluate the cement sheath of X gas storage.The evaluation results show that the existing cement slurry system can theoretically play a safe and effective sealing effect.(2)The seal integrity test of X-gas storage cement sheath was carried out.The experimental results show that the existing cement slurry system can be sealed for a long time.The experimental results show that the cement sheath can resist the high pressure difference.The stress cycle test of the cement sheath is selected.The greater the pressure difference,the greater the risk of the cement sheath being destroyed.(3)By comparing the basic mechanical properties of cement sheath with different materials,the carbon fiber with the best effect on the mechanical properties of cement sheath was selected to improve the mechanical properties of cement sheath.The modified cement sheath can withstand longer cycle loading cycle and greater internal and external pressure difference,which can provide strong guarantee for the efficient development and safe production of gas storage.