The present invention provides a method and treatment fluid for blocking
the permeability of an elevated-temperature zone in a reservoir of a
subterranean formation penetrated by a wellbore, the method comprising
the steps of: a) selecting the zone to be treated, wherein the upper
limit of the temperature range of the zone is equal to or greater than
190.degree. F. (88.degree. C.); b) forming a well treatment fluid
comprising: water; a water-soluble polymer comprising polymerized vinyl
amine units; and an organic compound capable of crosslinking with the
vinyl amine units of the water-soluble polymer; c) selecting the
water-soluble polymer and the organic compound of the well treatment
fluid such that the gel time of the well treatment fluid is at least 2
hours when measured at the upper limit of the temperature range of the
zone; and d) injecting the well treatment fluid through the wellbore and
into the zone.