The Mechanism Of Crack Propagation Of "Fracture Network" Fracturing Of Tight Sandstone Gas Reservoir In Daniudi

Daniudi gas field belongs to tight sandstone gas reservoir.The effective permeability is lower than 0.1×10~3?m~2,and the pore structure of reservoir is characterized by low porosity,fine throat-fine throat.It is difficult to achieve effective development without fracturing.With long time mining,Daniudi development advantageous area of sand body and reservoir thickness gradually thinning.Horizontal wells after fracturing in the flow decreased gradually,the existing conventional fracturing technology has been unable to meet the level of wells further output.In the tight sandstone reservoir in Daniudi area,the fracture can be kept high and stable after the fracture of the network.This paper selected reservoir rock mechanics parameters,and establish well circumferential stress model of perforated well,respectively,the hole diameter,perforation orientation,perforation phase angle,perforation depth,perforation diameter,perforation density of well circumferential stress and fracture pressure are analyzed,only the phase angle and the azimuth angle have significant effect perforation orientation at 0 degrees and 180 degrees.The phase angle at 60 degrees or more hours minimum fracture pressure.Through physical simulation experiments,experimental displacement determine fracturing in tight sandstone gas reservoir in Daniudi 10mL/min,according to the formula into the field of displacement,respectively 10 meters and 100 meters fracturing,200 meters,a displacement of 4.565.42m~3/min,4.96.According to the formula into the field displacement,respectively,corresponding to the fracturing section 10 m,100 m,200 m displacement of 4.56,4.96,5.42m3/min.Finally,the influence of the perforation location and the natural crack angle on the crack propagation is analyzed by the physical model experiment.When the angle is 60 degrees or more,the hydraulic fracture will extend along the natural fracture,and it will extend through the natural crack.The classical crack fracture mechanics based on the extended model was developed using triangular unstructured grid of fractured rock mass is discrete,finite element method is used to calculate the displacement field and stress field,using the contour integral calculation of crack tip stress intensity factor and crack initiation angle,grid division or mobile nodes on the cracking unit numerical simulation of the crack propagation.And the influence of different parameters on the crack propagation in the multi-step and multi-stage fracturing of fracture network is analyzed.In the process of crack extension,there exists the phenomenon of steering,and the middle seam extends along the straight line.Both sides of the seam are affected by stress interference,and the direction of the minimum horizontal stress is deflected.When the length of the fracture extends to 60m,it is less affected by the stress interference,and then extends to the direction of maximum horizontal stress.Different cluster spacing can lead to different fracture deflection strength.The recommended spacing of two clusters is40m,and the recommended distance between the three clusters is 20m.On the basis of the stress state of Daniudi tight sandstone reservoir,the simulation of crack propagation in Daniudi horizontal well provides some guidance for the field.