I can't possibly help you with Norwegian terminology, but as far as I can tell your understanding of the term is correct. Here are a couple of references. "Warm-back" seems to concern shut-in in injection wells:
"Injection Wells
If an injection well is shut in for a period of time, the zones that take fluid will warm back to the geothermal gradient at a much slower rate than those that do not take fluid. Thus, it is possible
to use a short-term shut-in and the associated warm back profile to
determine which zones take injection."
http://www.spe.org/jpt/print/archives/2001/10/JPT2001_10_res... (p. 2)
"In this work, warm-back behavior (thermal recovery after injection completed), as well as JTC and VHD effects, at a multi-layered depleted gas reservoir are demonstrated numerically."
http://link.springer.com/article/10.1007/s12665-012-1689-9"For injection wells, a thermal analysis may be performed
by use of the “warm-back” response of the reservoir, after
it is shut in to determine the relative injectivity of the individual
zones."
http://www.spe.org/jpt/print/archives/2002/11/JPT2002_11_tec... (p. 2)