Numerical Simulation Of Oil Well Perforation

Perforation completion is the main method of well completion. In the current study, It is briefly introduced that the related knowledge and researches about oil well perforation. Three-dimensional finite element model of a perforating charge is established. Jet formation, continuation and fracture are simulated numerically by ALE algorithm.Then, based on dynamic underbalance perforating test conducted by the laboratory of perforation efficiency in an oil field, ten three-dimensional finite element models that a perforating gun armed with multiple perforating charges(or trepanning charges) in the well fluid(water) with the initial pressure are constructed and numerical simulations are performed. The dynamic response of all the materials and the change law of the pressure field and the velocity field in the ten models are analyzed. It is indicated that the process of pressure variation inside the perforating gun can be divided into4stages-severe concussion stage, slowly rise stage, rapid rise stage and pressure balance stage and the process of pressure variation outside the perforating gun can be divided into3stages-severe concussion stage, pressure drop stage and pressure balance stage, whether the charges are perforating charges or tapping charges.Contrastive analyses about the ten models are implemented. Analysis results show that(1) The final pressure value in the well is positively correlated with the number of trepanning charges, while time used in pressure drop is negatively correlated with the number of trepanning charges;(2) The final pressure value in the well is positively correlated with the initial pressure value of the fluid. With the increase of initial pressure, time used in the pressure drop will be reduced, when the initial pressure is less than a certain value. But as the initial pressure is greater than the certain value, the trends of time variation are not obvious.(3) The relationship between the final pressure value and perforating gun height is monotone decreasing, while the relationship between time used in the pressure drop and perforating gun height is not liner.Finally, the analyses of dynamic underbalance perforating are carried out. Three key parameters of dynamic underbalance perforating are maximum dynamic underbalance pressure, the duration of pressure drop and the duration of the pressure recovery. And the main variables which control these key parameters are discovered from the results of simulation analysis. The main variables are perforating gun height, the initial pressure value of the fluid and the number of perforating charges (or trepanning charges).