Plug Removal Technology and Reasons for Low Efficient Injection Wells in Low Permeability Oilfield

摘要

For the characteristics of serious reservoir damage and insufficient injecting in injection wells in the water flooding development process in Chao Yanggou low permeability oilfield, it carries the analysis of reasons for forming low efficient injection wells and the development of acidizing plug removal agent. Through core damage experiment of wellhead sewage and well flushing sewage in Chao Yanggou oilfield, reservoir damage is mainly caused by excessive levels of suspended matters. After injecting wellhead sewage and well flushing sewage, the decrease rate of permeability is over 70% for cores that permeability is less than 10 x 10~(-3) μm~2. Based on the result of indoor core damage experiment and actual oilfield production data, the variation of apparent injectivity index in low efficient injection wells is researched. The research result indicates that reservoir damage radius of pollution wells is about 20m in Chao Yanggou oilfield. Based on reservoir damage condition of Chao Yanggou oilfield, compound acid is developed, which has the properties of strong penetration, retarding reaction velocity and strong chelate technology. Plug removal experiment indicates that the recovery rate of core permeability is about 100% using developed compound acid. Field test result indicates that the effective rate of acid stimulation treatment of new plug removal agent is 75.6%, and the effect is perfect.