Study Of Perforation Borehole On Casing Damage Mechanism

During oilfield exploration, perforating is a main method used in well completion. It makes use of perforating charges to penetrate casing, cement and formation; make oil and gas from the formation flow into the wellbore, and flow to the surface with the formation pressure to produce oil and gas. Therefore, perforating completion is a very important step during oilfield exploration and production, which is significant for the productivity of oil and gas wells.When oil and gas channel are created by perforating, the casing is inevitably damaged to some extent. The shape and density of the perforations will affect the casing strength. Thus, it is important to study the effect of perforation on casing damage. The author of the paper utilized a finite element method and established a 3D finite element mechanical model. Based on theory of elasticity and assisted by finite element software, the round and flat holes in casing created by perforating are analyzed with finite element, and the maximum stress that the casing can stand are given under different conditions. The study mainly includes two aspects: one is that the casing are simplified to a cylindrical shell, based on Donnell governing equation of cylindrical shell, the expression of the cylindrical shell under stress is derived; the other is that using structural finite element analysis and numerical calculation software ANSYS, the maximum stress that the casing can stand are calculated when the single round hole, single flat hole, multiple round holes and multiple flat holes are created in the cylindrical shell, thus to provide effective theoretical guidance for actual perforating operation.