Abstract: A method for generating hydrofluoric acid (HF) in-situ in a subterranean formation (e.g. sandstone formation) by simultaneously injecting an acid generating component having ammonium fluoride and an oxidizing agent and a heat generating component having ammonium and nitrite salts into a wellbore of the formation. The method optionally involves a pre-flush of an acid (e.g. HCl) containing solution prior to the injecting. HF is generated via an endothermic reaction of the ammonium fluoride and the oxidizing agent with the assistance of the heat provided by an exothermic reaction of the ammonium and nitrite salts. The method is effective in enhancing permeability of the formation by at least 30%.

Abstract: A method for generating hydrofluoric acid (HF) in-situ in a subterranean formation (e.g. sandstone formation) by simultaneously injecting an acid generating component having ammonium fluoride and an oxidizing agent and a heat generating component having ammonium and nitrite salts into a wellbore of the formation. The method optionally involves a pre-flush of an acid (e.g. HCl) containing solution prior to the injecting. HF is generated via an endothermic reaction of the ammonium fluoride and the oxidizing agent with the assistance of the heat provided by an exothermic reaction of the ammonium and nitrite salts. The method is effective in enhancing permeability of the formation by at least 30%.

Abstract: The chelating fluid for enhanced oil recovery in carbonate reservoirs and the method of using the same utilizes a chelating fluid injected into a carbonate oil reservoir through a fluid injection system. The chelating fluid is a solution of a polyamino carboxylic acid chelating agent in brine, with the polyamino carboxylic acid chelating agent having a concentration of approximately 5.0 wt % of the solution, with the solution having a pH of approximately 11.0. The polyamino carboxylic acid chelating agent is preferably ethylenediaminetetraacetic acid (EDTA). The brine preferably has a relatively high salinity, with a sodium chloride concentration preferably on the order of approximately 18,300 ppm.

Abstract: The chelating fluid for enhanced oil recovery in carbonate reservoirs and the method of using the same utilizes a chelating fluid injected into a carbonate oil reservoir through a fluid injection system. The chelating fluid is a solution of a polyamino carboxylic acid chelating agent in brine, with the polyamino carboxylic acid chelating agent having a concentration of approximately 5.0 wt % of the solution, with the solution having a pH of approximately 11.0. The polyamino carboxylic acid chelating agent is preferably ethylenediaminetetraacetic acid (EDTA). The brine preferably has a relatively high salinity, with a sodium chloride concentration preferably on the order of approximately 18,300 ppm.

Abstract: The method for enhanced oil recovery by in situ carbon dioxide generation utilizes a chelating fluid injected into an oil reservoir through a fluid injection system. The chelating fluid is a low pH solution of a polyamino carboxylic acid chelating agent. The polyamino carboxylic acid chelating agent may have a concentration of about 5 wt %. The polyamino carboxylic acid chelating agent is preferably either an aqueous solution of H2Na2-ethylenediaminetetraacetic acid (pH 4.5), H3-hydroxyethyl ethylenediamine triacetic acid (pH 2.5), or an aqueous solution of H2NaHEDTA (pH 4). The injection of the chelating fluid may be preceded by flooding the core with seawater, and is followed by injection of either to seawater, a high pH chelating agent, or low salinity water to ensure maximal extraction of oil from the reservoir. The method is particularly for use in formations where the core of the reservoir has a carbonate rock matrix.