The BZ19-6 condensate gas field,characterized by large reserves,small surface pressure differential,high temperature and pressure reservoir conditions,and low porosity and permeability,is highly susceptible to retrograde condensation contamination during production operations.Evaluating the degree of retrograde condensation contamination and adopting appropriate contamination remediation measures are crucial for improving the situation in the BZ19-6 condensate gas field.The long core failure experiment was carried out using the mixed condensate gas to simulate the reverse condensate pollution,test the gas permeability corresponding to different exhaustion pressure points and evaluate the degree of reverse condensate pollution.Additionally,experiments on remediation of retrograde condensation contamination were carried out using three different approaches:injection of surfactant(TC281),injection of methanol,and injection of a combination of methanol and surfactant.Furthermore,an experiment was conducted using a combination of methanol and surfactant to address both retrograde condensation and water blockage,a comprehensive liquid phase contamination.The experimental results indicate that all three schemes of injecting active agent(TC281),injecting methanol and injecting methanol+active agent have certain effects on removing retrograde condensation pollution.The group of injecting methanol+active agent 1 has the best effect on removing retrograde condensation and removing retrograde condensation pollution,and the permeability recovery rate is 84％.The permeability recovery rate of methanol injection to remove retrograde condensation pollution is 81％.The recovery rate of retrograde condensate permeability in the surfactant injection group 1 was 54％.The injection of methanol+active agent 1 relieved the comprehensive liquid phase pollution of reverse condensation+water lock,and the permeability recovery rate reached 80％.These experiments provide guidance for remediation strategies to address retrograde condensation contamination in the BZ19-6 condensate gas field.
low permeabilitycondensate gas reservoirretrograde condensate damageremove damagepermeability recovering rate
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