Three-level assessment for casing in marine gas reservoir

摘要

With the large-scale exploitation of marine gas reservoirs in Sichuan, a casing becomes thin, deformed, cracked or even broken after long-term downhole service, seriously restricting the working life of gas wells. To assess the safety of in-use casings, a three-level assessment model of casings is established, which provides a systematic screening and analysis method for the safety evaluation of casings in marine gas reservoirs. By means of factor analysis, feasibility demonstration and result comparison, the three-level assessment is proved to be suitable for casings. The assessment shows that the safety margin of casings rises step by step. The casing with high safety margin can be eliminated by the first level assessment to improve the efficiency and economy of the process, and then the scope of the dangerous case can be reduced by the second level assessment. Finally, the dangerous case and its real safety margin can be identified by the third level assessment to avoid increasing of the maintenance cost because of the excessive safety margin. Therefore, accurate identification and cost reduction can be achieved by three-level assessment.