Process for the secondary or tertiary recovery of petroleum

A process for the secondary or tertiary recovery of petroleum from subterranean formations penetrated by an injection well and a producing well which comprises introducing into said reservoir through said injection well a displacing medium to displace said petroleum from the reservoir, said displacing medium comprising water and an aminomethylated polymer having a molecular weight of at least 200,000, said polymer being selected from the group consisting of polyacrylamide, partially hydrolyzed polyacrylamide and copolymers of acrylamide and 2-acrylamido methyl propane sulfonic acid wherein the amino substituent of the polymer is prepared from amines of the formula:

• ##EQU2## wherein R.sub.1 and R.sub.2 are each independently selected from alkyl groups having from 1 to 5 carbon atoms in order to increase the solution viscosity of said displacing medium.