GEOG 4891 Lecture Notes - Lecture 2: Casing String, Polyethylene Terephthalate
Document Summary
Casing string combined by more than one casing section is called combination casing string. The purpose of combination casing string is to reduce the cost while satisfying calculated three number of design factors: joint strength, collapse pressure and internal yield. (engineering practice shows that longitudinal yield is satisfied if joint strength is satisfied). Ls = pc / (0. 052*ni* ) where is fluid density in ppg. Here, assume that external pressure is due to external fluid column, and internal pressure is zero, and the cheapest weight and grade of casing satisfying above equation is to be chosen. To calculate casing section length other than the lowest, the longitudinal tension effect on collapse pressure is to be considered. This way requires either trial and error (iteration) solution or graphizal solution. Here, reduced collapse resistance is controlling factor, and joint strength together with longitudinal yield are to be considered. Casing section is to be designed to satisfy following equations:
