| Polymer flood has been one of the most promising tertiary oil recovery for its simple technique, high oil recovery improvement and better economic benefit Currently, it has been applied in commercial scale and achieved better results in Daqing oil field. But along with the injecting of polymer, injection situation is growing worse year after year. It mainly behaves with high injection pressure or intermittent injection, which affected development of polymer flood greatly. Conventional hydraulic fracture and chemical plug removal have been applied in field, it can solve the problem, but it still has shortage of low injection rate and short valid period. So we analyzed the main reasons of polymer injection wells plugging. According to the constituent of plugging matter, we developed a kind of new plug remover. Additionally, formation protection technique was studied to inhibit again-adsorption of polymer after plug removal to prolong the valid period of treatment. Degradation rate for polymer flocculating colloid from bottom of well applied the plug remover can reach 99.5%, meanwhile, it can dissolve nearly all mechanical impurity. After plug removal, core permeability restoring rate can be 132.8% averagely. For formation protector, total damage rate can be decreased by 19.6% , and core permeability can be improved 132-165% in condition of injecting 60PV polymer after treated by protector contrasting to blank. This technology have been applied for 17 wells, the average valid period is up to 6 month, longest 12month, effective rate 94%, and pressure decreased by 1 .50MPa in early stage after treatment. |
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