Question 2

The casing program for a vertical well is shown in Table 2:

(1) Calculate the worst collapse and burst loads for:

• Surface casing

• Intermediate casing

• Production casing

(2) Based on the collapse and burst loads above, design the intermediate casing string (other casing strings are not required) by identifying casing outside diameter, grade, weight and section length. Assuming that all API casing grades are available.

You should consider:

a) Maximum collapse loading - use 1 as the safety factor.

b) Maximum burst loading - use 1.1 as the safety factor, assuming BOP rating 5000 psi.

c) Maximum tensile loading including weight, shock loading, pressure testing (60% of the burst resistance of casing) and bending (with dog leg 3/100ft) – use 1.8 as the safety factor.

d) Biaxial loading.

e) Using combination casing string to save casing cost if applicable.