Burst is a condition where internal pressure exceeds pressure loading. Burst can happen in several situations, such as well control, pressure test casing/tubing, pumping operation, etc.
Figure 1 – Burst Pressure Diagram
Minimum burst rating pressure (internal yield pressure) can be calculated by the following equation.
Where;
PB – Minimum internal yield pressure (psi)
Yp – Minimum yield strength (psi)
t – Nominal wall thickness (in)
D -Nominal outside diameter of the pipe (in)
This image shows when tubular is exposed to a differential internal pressure over its burst pressure rating.
(Ref: http://gekengineering.com/Downloads/Free_Downloads/Casing_Design_Hand_Calculation_Design_Example.pdf)
Some interesting points about burst pressure
- This equation (Barlow’s Equation) determines the internal pressure at which the tangential stress at the inner wall of the tubular reaches the minimum yield strength (YS) of the pipe.
- Factor 0.875 in the equation represents allowance of manufacturing tolerance of -12.5% on wall thickness specified in API 5CT.
- Burst will be occurred when stress is over ultimate tensile strength of material. However, the equation uses the Yield Stress of material, which is a conservative assumption.
Example: Calculate the tensile strength of the following pipe.
4-1/2” casing, weight 9.5 ppf, grade J-55
Pipe ID = 4.09”
Wall thickness 0.205 “
Yp = 55,000 psi
PB = 4,385 psi
This figure can be seen in the API specification.
Figure 2 – API Burst Rating Pressure
Download the API tubular data sheet here – https://www.drillingformulas.com/oilfield-casing-data-sheet-free-download/
References
Jonathan Bellarby, 2009. Well Completion Design, Volume 56 (Developments in Petroleum Science). 1 Edition. Elsevier Science.
Wan Renpu, 2011. Advanced Well Completion Engineering, Third Edition. 3 Edition. Gulf Professional Publishing.
Ted G. Byrom, 2014. Casing and Liners for Drilling and Completion, Second Edition: Design and Application (Gulf Drilling Guides). 2 Edition. Gulf Professional Publishing.
PEH:Casing Design. 2015. Casing Design. [ONLINE] Available at: http://petrowiki.org/PEH%3ACasing_Design. [Accessed 1 June 2016].
