Abstract: At present,phenolic resin cross-linking agents commonly used in profile control and flooding operations in domestic oilfields have short storage period which makes it unable to meet the requirements of long period field operations.Under such circumstances,the modified phenolic resin cross-linking agents were synthesized by using salicylic acid modifier.Molecular structures of modified phenolic resins were characterized by 1H NMR,and researchers investigated the effects of modifier dosages,catalyst dosages and high temperatures on the storage life and gel strength of modified phenolic resin.The effects of cross-linking agent dosage,temperature and salinity on gelling time and gel strength of modified phenolic resin cross-linked system were also investigated.The thermal stability,plugging performances and EOR effects of the modified phenolic resin cross-linked system were assessed.Lab test results showed that the ester structure with steric hindrance that was introduced into the modified phenolic resin could prolong the storage life significantly,resulting in a storage life of modified phenolic resin up to 234 d at room temperature,and over 90 d at 45℃.The cross-linked system can form strong gel at temperatures of 60-100℃ or salinities of no more than 20 000 mg/L.Studies showed that the viscosity retention rate of the cross-linked system in 180 days was more than 88%,and the plugging ratio more than 98%.In this case,the EOR increased by 14.6%.The synthetically modified phenolic resin cross-linking agents not only have outstanding cross-linking properties,but also have excellent storage performances,so as to meet the demands of long-term operations,with excellent prospects for application.