Tubing Stress Analysis 

Oil and gas well tubing strings must be designed to withstand the forces and stresses generated by the anticipated service conditions over the operating life of the well. In addition, if the tubing is free to move, tubing length changes must be determined so that adequate seal assembly lengths are selected. This section is designed to help the completion engineer in understanding the reasons and consequences of the stresses and strain caused to the tubing and guide him/her through the tubing stress analysis process. Introduction: The cost of tubulars and completion components is often a large portion of the total well cost and can be as high as 20% of the total. The tubing and the completion form an integral part of the safety of the well. Failure of the completion can result in injuries, fatalities, major expenditure and considerable loss of production. Tubing stress analysis is a major requirement of any completion design. Since the calculations involved in the analysis procedure are complex, a computer program is used in determining the optimum tubing design. Consequently, it is no longer necessary for the designer to perform hand calculations to analyse tubing string stress and strain. However, an understanding of the calculations and procedure is required to properly utilise the tubing analysis computer model. Computer analysis liberates the designer from the drudgery of repetitious calculations due to the all the permutations of prognosed data available and optional completion designs so that he or she can concentrate on achieving a more accurate estimate of the service conditions. The tubing stress analysis computer program in use by BP worldwide is Enertech’s WellCat package. This document is not intended to be a user manual for such computing packages although reference can be made to the WellCat manual. Keywords: tubing stress analysis, oil and gas industry, drilling