特低渗油藏驱油剂蓄能压裂对裂缝扩展的影响OA

To improve the recovery of ultra-low permeability reservoirs in peripheral oilfields of Daqing,true triaxial fracturing experiment using sandstone outcrops with different displacement agents and diversion times is per-formed,induced stress field evolution law is calculated combining with pore pressure induced stress model,and field fracturing stimulation is operated based on technical concept of"pre-fracturing energy storage,multi-stages di-version and soaking imbibition".The results show that pre-fracturing energy storage can change horizontal stress field,causing hydraulic fractures to deflect about 13°.As displacement agent volume increases from 150 mL to 450 mL,horizontal stress difference decreases by 1.81 MPa,fracture deflection increases by about 32°.Field displace-ment agent volume is nonlinear correlated with fractures azimuth.When displacement agent volume exceeds 2 000 m3,fractures network azimuth increase tends to slow down,with stimulation effect weakened.Temporary plugging diversion fracturing can form complex fractures network,and the difference between breakdown pressure of new fractures and the extension pressure of previous stages surpasses horizontal stress difference(5 MPa),causing new fractures to break in rock matrix.If the pressure difference is less than 5 MPa,new fractures occur along natural weak planes or micro-fractures,with small angle to the main fracture(less than 30°).The research provides refer-ence for field development of ultra-low permeability reservoirs.