Abstract:In order to reveal the mechanism of early seal failure of the high performance HNBR packer in CO2 injection well,the features of failure wells and the phase characteristics of CO2 were analyzed,and an indoor experimental method for achieving a constant decompression rate was proposed.The rubber surface topography was observed and the mechanical performance was tested under different CO2 decompression rates.The results show that with the increase of the decompression rate,the phenomenon of small bubbles,large bubbles and bubble rupture appear on the rubber surface,and the sealing performance of the rubber is obviously deteriorated.When thepressure the gas injection well is suddenly relieved,the gas inside the rubber can not seep out in a short time.Under the action of internal and external pressure difference,it will expand to form bubbles or even burst,which is the main reason for the early seal failure of packer in CO2 injection well.In order to prevent the the early seal failure of packer,it is recommended that the decompression rate of wellhead onsite should be controlled within 5 MPa/h.