ACID COMPOSITION FOR TREATING TERRIGENOUS OIL RESERVOIRS AND A METHOD FOR ACID TREATMENT OF THE BOTTOM ZONE OF FORMATION 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, wt %: inhibited aqueous hydrochloric acid 8.0-15.0, fluorine-containing reagent 1.5-10.0, boric acid 1.0-3.0, surfactant 0.5-1.5, and fresh water, in particular 1:2 mixture of Naftenol ML and OS-20 as surfactant, hydrofluoric acid or ammonium bifluoride, or ammonium fluoride as fluorine-containing reagent, and additionally: isopropyl alcohol 0.0-10.0. 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. Presence of borohydrofluoric acid in composition creates borosilicate film preventing migration of particles during the acid treatment. Composition is characterized by slowed reaction with rock at formation temperature so enlarging coverage of the formation treatment zone and reducing appearance of deposits, low surface tension, low corrosion rate, compatibility with inhibitors added to commercial acid. Composition forms also no emulsions upon contact with oil and hydrocarbons.

EFFECT: increased acid treatment efficiency.

2 cl, 1 dwg, 2 tbl, 4 ex