The Effect Of Natural Fractures On Hydraulic Fracture In High Stress Field

This dissertion mainly researches in the propagation when hydraulic fracture crossing the natural fractures.As the shale gas revolution,the propagation behavior when hydraulic fracture crossing the natural fractures has been more and more important.This dissertation researches it by 3 aspects: theory criterion,numerical simulation and laboratory test.We simulates the hydraulic fracture propagation in high stress condition to help us find the propagtion difference between high and low stress condition.With those method,we got following conclusions:(1)Extend Gu's criterion,and the comparison between criterion and laboratory result shows good accuracy.Conclude the fracture constitutive model.(2)Complete the hydraulic fracture simulation algorithm by DEM.We found that the DEM simulation has good relativity with Gu's criterion,which infer the simulation is relative correct.(3)Research the propagation behavior with laboratory test by triaxial mechanical mechaine.With the laboratory test we found following conclusions: a)The shorter natural fracture length will cause the pressure curve more unstable,and the Fracture Pressure will be higher;b)the longer natural fracture length will cause hydraulic fracture has branch cracks more easily.(4)Reasearch the propagation behavior by DEM simulation.We found that the simulation result has good relevance with laboratory in low stress condition.In the high stress condition,the simulation shows complex fracture network in nearbore zone,which means high confining stress may cause the failure of nearbore rock.