In-situ polymerization gel system is one of the important measures to alleviate reservoir heterogeneity. In order to solve the problem that the gelation time of in-situ polymerization gel system is too fast

taking polyvinyl butyral（PVB） as the wall material and the mixture of ethanol and water as solvent

the delayed gelation microcapsule initiator with ammonium persulfate as the active core has been prepared by interfacial precipitation method. Meanwhile

the performance of microcapsule regulating gelation time of in-situ polymerization gel system has been studied. By mixing 0.05 % ethanol solution of PVB with aqueous solution containing ammonium persulfate and 0.6 % compound stabilizer（OP-10 and Twe

en 80） at a volume ratio of 7:3

microcapsule initiator with an average particle size of 0.7~1.5 μm have been prepared

and the optimal concentration of ammonium persulfate is 0.2 % ~ 0.4 %. At 40 ~ 90 ℃

the gelation time can be longer than 30 h by adjusting the concentration of microcapsule initiator. Core test result shows that the microcapsule initiator can be successfully injected into the core with an average permeability of 50×10

-3

μm

2

and initiate the polymerization of in-situ polymerized gel system to produce effective plugging. The in-situ polymerization systems with initiator microcapsules can be injected into reservoirs with an average permeability of 50×10

-3

μm

2

and initiate the polymerization of in-situ polymerization gel system to produce effective plugging. The enhanced oil recovery（EOR） result indicates that the oil recovery increases by 20.24 % after the gelation of the in-situ polymerization gel system.