Theoretical Research And Engineering Application Of Rock Plastic Damage Model

With the increase of oil production time of oil wells,oil wells will be blocked due to mechanical impurity migration,chemical reaction product precipitation,mineral deposition and other problems in the near well zone,which will reduce oil production and even stop production,which is not good for efficient development of oil fields.Hydraulic oscillation(hydraulic pulse)plug removal technology can solve the problem of oil well plugging quickly and effectively without destroying the reservoir structure and polluting the oil quality,and plays an important role in improving oil well production.And the method is easy to operate,low cost,and has been applied in oil field.The essence of hydraulic oscillation plug removal is realized by the hydraulic oscillator running into the bottom of the well.Through the mechanical structure,it produces a certain frequency of cyclic stress,which acts on the shaft wall,generates hydraulic oscillation wave,transmits the stress,vibrates the surrounding strata,and peels off the attachments in the pores.When the stress reaches a certain degree,the rock near the shaft wall will be damaged,forming micro cracks and improving the seepage performance.In order to further understand the construction principle,the construction process is analyzed in combination with rock mechanics theory.Based on the investigation of current rock material strength criteria and existing numerical analysis methods,the international finite element analysis software ABAQUS is adopted.Aiming at the special point of hydraulic vibration construction: tension compression cycle load,CDP model included in ABAQUS software is selected for hydraulic vibration construction Simulation.CDP model is applicable to simulate the application of cyclic load in the presence of confining pressure.According to the construction of hydraulic oscillation,the model is established,and the boundary conditions and cyclic load of open hole completion and perforating completion are set to simulate.By changing the amplitude and vibration frequency of stress by controlling variable method,the following conclusions can be obtained:Under the condition of open hole completion and perforating completion,if the hydraulic oscillation frequency is above 50 Hz or too high,the stress amplitude transmission ability will be reduced,and the stress wave transmission range will be smaller.When the oscillation frequency is lower than 10 Hz,the influence of frequency on the construction effect will be smaller,so the low-frequency hydraulic oscillation is more favorable for the construction;the larger the stress amplitude,the strain of the rock near the borehole wall will also be caused The larger is the area of stress wave.Therefore,in the selection of construction stress amplitude,high amplitude hydraulic oscillator should be selected based on the principle of not breaking.