Research On Impact Dynamics Behavior Of Curved Well Perforation String

Perforation completion is an important working procedure before oil and gas wells are put into production.The purpose of perforation is to penetrate the casing and cement ring to reach the oil and gas reservoir.In order to increase oil recovery efficiency,the perforating equipment has become more and more powerful,and the high impact overload generated during the perforating process has also increased dramatically.The excessive impact load has become a main factor in the deformation,bending,and fracture of the perforated string system during well completion.The dynamic behaviors of the perforated string system,which is mainly consist by perforating segments with perforating gun and other perforating equipment,under the explosive impact load caused by perforation bomb explosion has become a core problem for the safety design and optimal allocation of perforation string.Aiming at the core problem of the dynamic characteristics under percussive explosion impact,the energy source of the percussive impact load has been studied.Based on the combination of ANSYS simulation software and LS-DYNA solver,the process of cumulative energy jet and the conversion rate of main explosive charge to detonation shock wave of energetic perforated projectile were studied by adaptive mesh generation technology,and the ALE algorithm was used to simulate and analyze the distribution and evolution of the overpressure under free water zone and the distribution and evolution of the annulus overpressure in the actual wellbore when perforated projectile exploded.Comparing with the existing empirical model of explosion overpressure in free water zone,the model of explosion overpressure in actual wellbore completion has been summarized.On the basis of summing up the overpressure distribution and evolution model of the underground wellbore perforation and explosion,the wave control equation for the vibration of perforated pipe-string in the curve-well is established after the research on blasting vibration mechanism of downhole tools in the curve-well been made through the analysis of downhole perforation technology and perforating pipe-string structure.The vibration equation has been solved by using the numerical method of Newton difference.The computer program computing the shock and vibration of the perforating string of curve-well under explosive impact load is developed by Fortran language.The parameters of perforating string module,perforating gun module,shock absorber module,and wellbore structure module on influence of perforating string vibration dynamic response are studied respectively.It has been found that:as the perforated string length increases,the maximum tensile force the packer suffered is correspondingly increased.The maximum pressure of the perforation string suffered is shifted along the direction in which the oblique depth increases.The position of buckling instability in a perforated string appears in a certain position between the bending end point and the bottom of the perforated string.With the increase of charge quantity,the maximum tension and compression of perforated string increase dramatically.and the buckling of perforated string is more likely to happen.However,the length of perforating gun has no significant influence on the dynamic response of perforated string.With the increase in the number of shock absorbers,the maximum tension and compression of the perforated string suffered are significantly reduced,but when more than two shock absorbers are installed in the same location,the effect of vibration reduction is not very obvious,and the cost-effectiveness of vibration reduction is reduced.The greater the curvature of the well or the greater the angle of inclination of the well,that is the more severe the perforation string bends,the maximum compression the perforation string suffered increasing dramatically,and the bending transition at the perforated string is more prone to buckling than the rest position.So,for the large-curvature,large-angle inclined curved wells or horizontal wells,great attention must be paid to the stability of the perforated string.