METHOD FOR TREATING BOTTOM-HOLE ZONE OF BED Russian patent published in 1998 - IPC

FIELD: oil and gas production industry. SUBSTANCE: this relates to recovery of liquid and gaseous media from bore-holes with application of corroding matters. According to method, to increase dimensions of filtration passages and consequently to increase permeability of down-hole zone due to solving minerals of cement and part of reservoir skeleton, successively injected into well are four water solutions in following sequence: alkali solution, two acid solutions and one buffer solution for separating them. Composition of solutions is as follows: alkali solution - hydroxide of alkali metal for example of sodium with concentration of 10-50 mass%; buffer solution - - chloride or/and nitrates, fluorides of same alkali metals with concentration of 10-25 mass%; first acid solution - for example muriatic or nitric acid with concentration of 12-30 mass%; second acid solution - hydrofluoric acid with concentration of 10-15%. Alkali solution is heated to temperature of 30-80 C. Exact concentrations of corroding solutions are calculated according to content of alkali-acid soluble minerals in cement and reservoir skeleton with surplus required for dissolving solid and colloidal products of reaction of preceding solution and maintaining Ph value. As to buffer solution, this is made according to density of corroding solutions. Treatment is performed without keeping solutions in bed for reaction. EFFECT: higher efficiency. 13 cl, 1 tbl