A 9 5/8 in intermediate casing to be set at the depth of 7,991ft. The mud weight is 12.41 ppg, the formation pore pressure is0.751 psi/ft. and a bottom hole pressure of 4,612 psi is expectedwhen drilling the next hole section. The surface casing of 13 3 8in. is set at 3,000 ft. Assume that all API L, K and N grades areavailable. All the relevant information is given in the tables aregiven below.

i. Design a combination intermediate casing string for the worstpossible loading conditions. (25 marks)

ii. Estimate the number of sacks of cement required for theintermediate casing. (15 marks)

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Drillpipe Drillpipe Weight Dillpipe capacity Bit size Cementing data Casing OD Pump output Float collar above shoe Lead cement Lead cement slurry yield Tail cement yield Excess Volume 5.0 in 19.5 lb/ft 0.01776 bbl/ft 12-in 9- in 0.136 bbl/stk 100 ft 20% of surface casing depth 1.25 ft³/sk 1.15 Assume Grades Weight Plain end Area Burst Limit Collapse Limit Lb/ft in² 11.454 12.559 13.572 15.547 11.454 12.559 13.572 15.547 11.454 12.559 13.572 15.547 L-80 L-80 L-80 L-80 N-80 N-80 N-80 N-80 K-90 Casing Pipe Available for 9 5/8 in(O.D) K-90 K-90 K-90 40.0 43.5 47.0 53.5 40.0 43.5 47.0 53.5 40.0 43.5 47.0 53.5 (psi) 3815 4342 4895 5011 5750 6330 6870 7930 9515 10850 11990 12359 (psi) 1987 2215 2576 2846 3090 3810 4760 6620 8541 9972 10461 11168 Drillpipe Drillpipe Weight Dillpipe capacity Bit size Cementing data Casing OD Pump output Float collar above shoe Lead cement Lead cement slurry yield Tail cement yield Excess Volume 5.0 in 19.5 lb/ft 0.01776 bbl/ft 12-in 9- in 0.136 bbl/stk 100 ft 20% of surface casing depth 1.25 ft³/sk 1.15 Assume Grades Weight Plain end Area Burst Limit Collapse Limit Lb/ft in² 11.454 12.559 13.572 15.547 11.454 12.559 13.572 15.547 11.454 12.559 13.572 15.547 L-80 L-80 L-80 L-80 N-80 N-80 N-80 N-80 K-90 Casing Pipe Available for 9 5/8 in(O.D) K-90 K-90 K-90 40.0 43.5 47.0 53.5 40.0 43.5 47.0 53.5 40.0 43.5 47.0 53.5 (psi) 3815 4342 4895 5011 5750 6330 6870 7930 9515 10850 11990 12359 (psi) 1987 2215 2576 2846 3090 3810 4760 6620 8541 9972 10461 11168