Abstract: A chemical channeling sealing agent BFD is developed to solve the problem of channeling through cement sheath in Zhongyuan. This agent is composed of 20% to 30% of net-bridging agent, 60% to 70% of gelling material and 5% to 10% of swelling agent. A simulating sealing and plugging model was established, and it was used to evaluate the squeezing depth, sealing strength, rheology and initial setting time of BFD, while the influence of squeezing pressure and temperature on squeezing depth and sealing strength, as well as changing tendency of sealing strength in the sealing zone and borehole were investigated. Test results showed that it has minimum formation damage; the squeezing depth is 0.3 to 0.5 m, which can be eliminated through perforating; its sealing strength is 25 MPa or higher, and the initial setting time is 6h or longer. It also has such advantages as safe operation, good rheology and stability, simple field operation, etc., and it is suitable for sealing the external casing channeling in 30 to 150℃, sealing the bottom water in the pay zone and full-sealing reperforating operation. This agent has been field used for 12 times, with an operation success rate of 100% and efficiency rate of 95%.