It should be easy to measure the pipe thickness near the break. If it has not been eroded it should be possible to hydraulically clamp the pipe closed (like you would a bleeding artery). Alternatively, it should be possible to place a section of pipe containing a valve over the broken end. Weld the valve containing pipe to the broken one. Close the valve.
Er, uhm, no.
Based on shear strength of 70,000 psi of the two pipes, and their combined cross section area, it would take over 8,500,000 pounds of force to crimp the pipe that way. With no assurance at all that the flow would stop, or be even reduced significantly.
If you could crush both pipes that is: The outer one (21 inch diameter, 1 thick walls) is going to protect the inner one as it deforms and prevent the inner pipe (9 inch diameter, also 1 inch walls) from deforming and closing completely at both sides. At the extreme cold of that deep, the pipes, rather than bending into tight 180 degree “bends” are more likely to crack at the tight kinked corners where the crushing force is concentrated and break axially - down the pipe thus releasing more oil from the cracks.