MODIFYING EXPANSION FORCES BY ADDING COMPRESSION
A method for expanding a tubular in a borehole, the tubular having upper and lower ends, the system comprises a) applying a compressive load to the upper end of the tubular and b) expanding the tubular by moving an expansion device relative to the tubular while maintaining the compressive load. Step a) may include resting a weight on the upper end of the tubular or applying hydraulic pressure to the upper end of the tubular. The lower end of the tubular may engage the formation before step b) or as a result of step b).
1 . A method for expanding a tubular in a borehole, the tubular having upper and lower ends and an expansion device positioned below the upper end, the method comprising:
a) applying a compressive load to the upper end of the tubular; and
b) expanding the tubular by moving the expansion device toward the upper end of the tubular while maintaining said compressive load.
2 . The method of claim 1 wherein step a) includes resting a weight on the upper end of the tubular.
3 . The method of claim 1 wherein step a) includes applying hydraulic pressure to the upper end of the tubular.
4 . The method of claim 3 wherein step a) includes forming a moveable fluid seal above the upper end of the tubular and applying fluid pressure above the seal so as to cause the seal to bear on the upper end of the tubular.
5 . The method of claim 3 wherein step a) includes forming a hydraulic chamber above the upper end of the tubular and applying fluid pressure within the chamber so as to cause the chamber to bear on the upper end of the tubular.
6 . The method of claim 5 wherein the expansion device is a mandrel and applying fluid pressure to the chamber also causes the mandrel to move relative to the tubular.
7 . The method of claim 1 , further including the step of engaging the formation with the lower end of the tubular before step b).
8 . The method of claim 7 wherein the lower end of the tubular does not engage the formation before step b).
9 . The method of claim 8 wherein the lower end of the tubular engages the formation as result of step b).
10 . The method of claim 7 , further including the step of resting the tubular on the bottom of the borehole before step b).