Study on aggressively working casing string in extended-reach well

To study this operation, a new drag model is built to describe the behavior of casing string during aggressively working string. The model is an improved soft string model which considers dynamic motion of casing. The model is able to calculate forces and motion of casing string in falling process during aggressively working string. Two case studies are presented where casing string was aggressively worked to overcome high drags. Mechanical behavior of casing string in each case is studied and the safety issues are discussed. Finally, suggestions on this operation are also proposed.