ACID COMPOSITION FOR TREATING LOW-PERMEABLE TERRIGENOUS OIL RESERVOIRS AND A METHOD FOR TREATING BOTTOM ZONE OF FORMATION USING INDICATED COMPOSITION Russian patent published in 2004 - IPC

FIELD: oil and gas production.

SUBSTANCE: invention relates to compositions and methods for acid treatment of bottom zone of terrigenous formation and can be used in the course of the oil inflow intensification and developing wells by way of acid treatment of terrigenous oil reservoir, and also to intensify oil inflow and to raise oil recovery of strata by acid solution-assisted hydraulic fracturing of formation. Acid composition according to invention comprises chlorine-containing reagent, fluorine-containing reagent, and fresh water, in particular ammonium chloride or inhibited aqueous hydrochloric acid as chlorine-containing reagent, 1.0-5.0%; hydrofluoric acid or ammonium bifluoride, or ammonium fluoride as fluorine-containing reagent, 1,0-5.0%; and additionally: polyglycols, 10.0-40.0%, and "Alkyl phosphate - Khimeko", "Efiroks-7", or "Fosfol-10", 10-30%. This composition as such or diluted with fresh water at ratio (1-5):1 is used in acid treatment of bottom zone of terrigenous formation comprising consecutively pumping buffer liquid and acid composition into hole, forcing acid composition into formation with the aid of the buffer liquid, waiting the end of reaction (not longer than for 8 h), and removing reaction products. Acid composition is used in amount corresponding to 0.5-2.0 m³ per 1 m of perforated formation thickness. Aforesaid buffer liquid is selected from 1.5-3.0% ammonium chloride solution, petroleum, and diesel fuel used in amounts corresponding to 0.5-1.5 m³ per 1 m of perforated formation thickness before pumping of acid solution and 1.0-5.0 m³ during the forcing of the latter. Use of proposed composition slows down reaction with rock at formation temperature so enlarging coverage of the formation treatment zone and reducing appearance of deposits. It also leads to lower surface tension in the border with hydrocarbons and reduces the rate of corrosion.

EFFECT: increased acid treatment efficiency.

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