Thanks for confirming that Mobilization and Top part of hole is...

Thanks for confirming that Mobilization and Top part of hole is usually the most expensive.
Hopefully not to many drilling issues for remainder of hole - and there are always issues.

One classic I recall is when NZOG was drilling Corvis - off WA coast. The gas zone was too big - over 400m and counting as never got to the bottom.
Because of the long time drilling and taking core, then the drilling fluids damaged the top part of the hole. So a 2nd hole was drilled very close by, with no coring and an open hole test was done. A lot of gas, but in the wrong price cycle, so it became a "stranded discovery" and was eventually handed back I think.