Casing Design Workshop: Final Surface Casing Design with Combined Loads Exercise (Last Updated 16 December 15)
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Casing Design Workshop Exercise: Final Surface Casing Design with Combined Loads Casing Design Workshop API Bi-axial Collapse Method Applied Use yield and tensile stress, calculate reduced yield with bi-axial yield equation Use appropriate collapse formula, calculate reduced collapse pressure Adjust casing design if necessary and recheck The Historical API Procedure Historical API Biaxial Procedure Calculate Axial Stress (Axial Load/Area of Tube) Calculate Effective Yield Stress 3 z z Ye Y 1 4 Y Determine Applicable API Collapse Formula (Using d o /t and the Effective Yield Stress) Calculate Reduced Collapse (Using the Applicable API Formula) PetroSkills, LLC., 16. All rights reserved. 1
Final Surface Casing Design with Combined Loads Example Final Casing Design Casing Design Summary 13 3/8" Surface Casing Safety Factor ** Section Joint Strength Number OD ID Weight Grade Connection Bottom Length Collapse Burst 13.375 1.615 54.5 K-55 ST&C 1 1 1. 1.33 1.6 1 13.375 1.415 68 K-55 ST&C 3 9 1.1 3. 3.6 Totals: 3 Does not include bi-axial effects Minimum Design Factors Mud Weight: 9. ppg Collapse: 1.15 Burst: 1.15 Tension: 1.6/1, ** Safety Factor: Strength / (k D * Load) Tension Load (Running) Depth (ft) Axial Load (1 lb) -5 5 1 15 5 1 15 5 3 35 Collapse Check Procedure Surface Casing Axial Loads True Axial Load Running Use true axial load (running case) No tension at the bottom Tension at bottom of 54.5 lb/ft section: 37, lb (from load line) at 1 ft TVD Calculate axial stress Calculate effective yield Calculate reduced collapse Calculate actual design load & compare it to pipe reduced collapse strength PetroSkills, LLC., 16. All rights reserved.
Casing Design Workshop Axial Stress 4 37 z 13.375 1.615 385 psi Effective Collapse Yield Calculate API Constants For Y e = 53769 psi A =.98643 B =.53445 C = 1169.191 F = 1.994 G =.35643 3 z z Ye Y 1 4 Y 3 385 385 Ye 55 1 4 55 Y 53769 psi e Use API formulas to calculate these constants (in manual and textbook) Your course spreadsheet will also make this calculation PetroSkills, LLC., 16. All rights reserved. 3
Final Surface Casing Design with Combined Loads Calculate d/t d d d o o o do t 1 do di 13.375 t.5 13.375 1.615 t 35. Determine API Collapse Formula Use the range formulas for each collapse formula to see which formula is appropriate (see manual for calculations) We determine that the correct collapse formula is the Transition Collapse Formula Or we could use the chart (next slide): d o /t = 35. Y e = 53769 psi Collapse Formula Range 4 PetroSkills, LLC., 16. All rights reserved.
Casing Design Workshop Calculate Reduced Collapse F pt Y G do t 1.994 pt 53769.35643 35. p 116 psi T Adjust the Design? The reduced collapse value is 116 psi The API value is 113 psi API rounds collapse pressures to nearest 1 psi If we round our result to nearest 1 psi then they are the same value No adjustment of the surface casing necessary New Formula? In the manual the reduced collapse is also calculated with the new API/ISO formula The reduced collapse is 1133 psi with the new formula (116 with historic formula) so there is no need for adjustment with the new formula either PetroSkills, LLC., 16. All rights reserved. 5
Final Surface Casing Design with Combined Loads Intermediate Casing 6 PetroSkills, LLC., 16. All rights reserved.