Sealing Performance of Packers in Offshore CO2 Injection Wells

Summary The reliability of the sealing performance of the packer rubber cylinder is crucial for the successful implementation of CO2 injection technology. Presently, the lack of an evaluation method for the sealing performance of the packer in the downhole environment of high-temperature and high-pressure CO2 medium makes it impossible to establish effective replacement standards for the rubber cylinder in accordance with various working conditions. This frequently results in serious downhole safety accidents. To research the degradation law of packer sealing performance in CO2 injection wells, this study first carried out the mechanical property test of rubber cylinder material with comprehensive consideration of the effects of temperature and CO2 corrosion. Based on the experimental results, a hyperelastic constitutive model of the packer cylinder material incorporating a temperature decrement factor and a time-temperature aging factor is constructed. Taking the offshore example Well X as the object, the variation law of the sealing coefficient of the packer during service under different temperature conditions is analyzed. The analysis results show that the higher the temperature of the packer in the initial stage, the better the sealing effect. For example, the sealing coefficient of the packer at a setting depth of 4000 m (82.06℃) is 5.70% higher than at a depth of 2500 m (68.98℃). However, higher-temperature environments accelerate the aging of the rubber cylinder as service time progresses, leading to a more rapid rate of degradation of its sealing performance. After 36 months of service, the sealing coefficient of the packer at a setting depth of 4000 m has instead decreased by 3.10% compared with the setting depth of 2500 m. This study is of great significance for predicting the life of the packer sealing element and establishing the replacement standard.