Design a $\frac{51}{2^{\text{'}\text{'}}}$ O$.$D$.$ casing string to $16,500ft,$ using any of the $P-110$ casing weights available in the Halliburton book. Assume worst possible conditions $($no backup for burst or collapse, etc.$).$ Use the API design factors $($Collapse $1\mathrm{.}125,$ Burst $1\mathrm{.}1,$ and Tension $1\mathrm{.}8).$ The weight of the mud in the hole is $13\mathrm{.}0l\frac{b}{g}al.$ Expected formation pressure below the casing seat is $10,000.$ Please design the most economical combination casing string for this well.

Calculate the Following:

Weight$/$ft of casing in bottom section of string $l\frac{b}{f}t$

Length of bottom section

$q,$

Weight$/$ft of casing in top section of string

$q,$ ft

Total weight of string in air

$q,l\frac{b}{f}t$

Actual weight of string in mud, considering buoyancy,

$q,$ lbs and assuming that the string is full of mud on the inside $q,$ lbs

Note:

Axial Load $($S$),$ psi Collapse Resistance, psi

$10,000,10,720$

$15,000,10,510$