Initially, as the pipe is lowered into the hole, it reaches...

Initially, as the pipe is lowered into the hole, it reaches ambient temp at each depth, so progressively expands. The initial installation therefore accomodates all the expansion from the difference between 25degC pipe being lowered into a 200+degC hole.

For changes in temperature:
Depends on how the pipe is held.

If it is fixed top & bottom, then all that happens is the pipe acquires compressive stress, same reason why the (continuously welded) rail line from Sydney to Perth does not buckle.

The stress is contained by the wellhead at the top and the bottom of the hole.Perth and Sydney Central stations in my example, although I have never yet seen a stressed rail employee, so......

So, the pipe expands downward to the extend of its bottom fixing method PLUS it acquires some compressive stress.