Chemical process for backsurging fluid through well casing perforations

Claim 1

A chemical well treating process for backsurging fluid through well casing perforations and perforation tunnels that interconnect a well with a subterranean reservoir, comprising: injecting through the well conduits, well casing perforations and perforation tunnels and into the reservoir an aqueous liquid solution of (a) at least one compound which contains at least one nitrogen atom to which a hydrogen atom is attached and is capable of being oxidized within an acidic aqueous solution to yield nitrogen gas and dissolved or liquid by-products which are substantially inert to the components of the well and reservoir, (b) at least one oxidizing agent which is capable of so-oxidizing the nitrogen containing the compound, (c) an alkaline buffer which is capable of maintaining said solution at a pH of at least about 7 at which the rate of the gas-generating reaction is relatively slow while a significant proportion of hydrogen ions are being released within the solution, and (d) a pH-reducing reactant which is capable of subsequently overriding the buffer and reducing the pH of the solution to a value less than about 7 at which the rate of the gas-generating reaction is relatively fast; correlating the composition of said aqueous solution with the pressure and temperature of the reservoir and the rate at which fluid can be injected through the perforation tunnels into the reservoir so that (a) the buffer-reduced rate of said gas-generation and the rate of said buffer-overriding is slow enough to permit a significant volume of the gas-generating solution to be injected into the reservoir before the rate of the gas-generating reaction becomes relatively fast and (b) the kind and amount of the nitrogen-containing compound and oxidizing agent are such that a significant amount of gas and heat are generated after the rate of the gas-generating reactions becomes relatively fast; injecting a significant volume of said gas-generating solution into the reservoir at least substantially as soon as its rate of reaction becomes relatively fast; and, allowing fluid to be produced from the well.