Study On The Influence Of Natural Fracture In The Tight Reservoir Of M Oilfield On The Propagation Of Hydraulic Fracture

The reservoir of M oilfield is very tight,with low porosity and permeability,so it is necessary to carry out fracturing to effectively exploit.At the same time,the natural fractures in this area are relatively developed,which is fractured reservoir,and the natural fractures will have an important impact on the hydraulic fracture propagation.However,there is no systematic study on the expansion law of hydraulic fracture in M oilfield.Therefore,this thesis studies the influence law of natural fracture on hydraulic fracture propagation in fractured reservoir of M oilfield.In this thesis,through the method of combining experiment and numerical simulation,firstly,the rock mechanical parameters and in-situ stress of the target reservoir are obtained by testing the basic physical parameters of the reservoir core from the target block of M oilfield;Then,Firstly,the influence of natural fractures on hydraulic fracture propagation was studied by large-scale true triaxial fracturing physical model experiment of cement rock blocks with preset natural fractures on the based of the basic physical parameters of the reservoir;Finally,the propagation law of hydraulic fracture after encountering single natural fracture and the propagation law of hydraulic fracture under the condition of multiple natural fractures are studied by using Abaqus numerical simulation software to establish the two-dimensional model of the interaction between hydraulic fracture and natural fracture under the condition of single natural fracture and the two-dimensional model of hydraulic fracture propagation under the condition of multiple natural fractures.The results show that the Young’s modulus of the target reservoir rock in M oilfield is 24.4-37.68 GPa,the Poisson’s ratio is 0.21-0.27.In the range of typical rock mechanical parameters,the stress difference is 3.78-9.69 MPa,and mainly concentrated in 3-6MPa.Through the fracturing physical model experiment and numerical simulation based on the basic physical parameters of the reservoir,it can be seen that the hydraulic fracture tends to turn to the natural fracture extension after encountering the natural fracture under the conditions of low stress difference,low fracturing fluid viscosity,high displacement,high matrix tensile strength,low approximation angle and high natural fracture dip angle,and the hydraulic fracture turn to natural fracture extends a certain distance,it will gradually turn to the direction of the maximum horizontal principal stress to extend forward under the action of horizontal stress difference.At the same time,under the conditions of multiple natural fractures,the hydraulic fracture are more likely to activate natural fractures to form complex fractures under low stress difference,low fracturing fluid viscosity,high displacement,high brittleness index,large natural fracture density and length.And the study also found that the natural fracture cementation strength and matrix tensile strength is too large or too small,which is not conducive to hydraulic fracture activation of natural fractures to form complex fractures;the horizontal stress difference of M oilfield is mainly concentrated3MPa-6MPa,and the overall horizontal stress difference is small.The average brittleness index is 0.578,and the overall brittleness of reservoir rock is high.Therefore,the reservoir can form complex fracture morphology under the conditions of high displacement and low fracturing fluid viscosity.The research results in this thesis can provide theoretical basis and guidance for the fracturing design of tight reservoir in M oilfield.