Perforating The Casing Strength

This paper was supported by the state key project of ministry of education (205135) "the research of complex formation earth stress based on coupling and mechanism of casing wear".Firstly, this paper investigated a large amount of information of test, theory and FEM research of perforated casing and method of improving its strength at home and abroad. A research of aspect of this paper was put forward after summarizing the materials. Then many finite element models on different perforation parameter including pore diameter, foramen density and phase angle were established, and analyzed the rule of strength decrease and ratio of stress concentration of perforated casing with perforation parameter. Based on those, some finite element models were established about different casing grade, different perforation parameter and different operating condition with comprehensive consideration of perforation parameter, casing parameter and active oil yield condition. This paper analyzed the change of perforated casing residual strength and yield stress and found these change rules with perforation parameter. These rules advise and support the optimal of perforation parameter.1. Most dominant factor affected casing collapsing strength is phase angle of perforation. While there are same pore density and pore diameter, 45 and 60 degree phase angle of perforation with screw holding affects least the casing collapsing strength.2. At 60 degree phase angle, pore diameter and pore density are contributed to casing collapsing strength lese than 10 percent. So big pore diameter and high pore density of perforation should be adopted to increase slotted density and reduce gas and oil flow rate in pore of perforation in case of sand production.3. The investigation of casing strength with perforation is shown the maximum stress and strain is not more than casing strength at some pore density, pore diameter and phase angle of perforation and high production is get by reasonable perforation parameter.4. After a mount of theory and FEM analysis, high pore density can improve the productivity ratio and casing collapsing strength reduces a little when other parameters of perforation don't change. So this paper recommends high pore density perforation well completion to oil yield.