Inhibition of scale formation from oil well brines utilizing a slow release composition

A method for the inhibition of scale deposition on the surfaces of a well coproducing oil and scale forming brines comprising injecting into the well reservoir an acidic aqueous solution at a first pH containing dissolved therein a scale inhibitor, multivalent metal ions in the presence of which said scale inhibitor is soluble at said first pH but with which it forms sparingly soluble salts at a higher pH, and a heat-sensitive pH-increasing substance containing no more than 10 carbon atoms, which decomposes at elevated temperatures liberating an alkaline compound, such that the solution is inherently heated by the higher ambient reservoir temperature to a temperature at which the alkaline compound is liberated from the heat-sensitive substance thus raising the pH of the solution to said higher pH at which a sparingly soluble multivalent metal salt of the scale inhibitor is phase separated from the solution on the porous surfaces of the reservoir rock formation, providing for a slow release of inhibitor into the produced brines when the well is in its production phase.