Simulation Of Fracture Interference And Propagation Of Multi-staged Horizontal Fractured Well In Shale Reservoir

Multiple stage fracturing is the core technique of the shale gas business development.Some unpractical conclusions on field fracturing were made for the vague cognition in the interference and extension law of multi-fracture of horizontal wells.The displacement discontinuity method was used to build model to calculate the induced stress of multi-fractures under the condition of any location,any length and any space in infinity and isotropy shale reservoir.Then based on the interference of multi-fractures,the material balance equation was made use of controlling time of extension,the maximum circumferential stress criterion was used to calculate crack steering angle.Finally the iterative coupling method was made use of simulating the interference and extension of multi-fractures.The model of the interference and extension of multi-fractures was used to simulate a variety of staged fracturing cracks.The main result and cognition as follow:(1)The modified displacement discontinuity method was made use of calculating the induced stress of single and multi-fractures.The induced stress in the original minimum horizontal principal stress direction is greater than the maximum horizontal principal stress direction.The induced stress calculated by the displacement discontinuity method is far less than the induced stress calculated by linear superposition.(2)The crack turning extension model was used to simulate the extension of single fracture under the condition of biaxial compression.The result show that when the perforation azimuth and the original maximum horizontal principal stress direction is inconsistent,the extension direction of bidirectional compressive single crack turn to the original minimum horizontal principal stress direction.The influence of horizontal stress difference and perforating angle on bidirectional compressive single fracture shape are analyzed at the same time.(3)The multi-fractures extension model was made use of simulating the subsequent fracturing crack,simultaneous fracturing crack,alternate fracturing crack and zipper fracturing crack extension respectively.The fracture propagation path,crack width and pressure distribution in the joint were analyzed.The influence of horizontal stress difference and crack space were analyzed quantificationally,the crack shape under difference condition was grasped.In this paper,a systematic study of multi-fractures extension rule was studied.The result of the study has a good practical guiding significance about the design of horizontal well staged fracturing.