RU2283423C1 - Water flow isolation method - Google Patents

Abstract

FIELD: oil production, particularly methods or devices for cementing, for plugging holes, crevices, or the like.

SUBSTANCE: method involves injecting composition containing polyacrylmide, sodium silicate and water in reservoir through well. Solid polyacrylmide is previously treated with 0.3-10 Mrad dose of accelerated electrons. The composition contains 5-15% of polyacrylmide suspended in aqueous sodium silicate solution having density of 1.2-1.5 g/cm³. After above suspension injection water composition is additionally injected in reservoir. The water composition contains soluble calcium or magnesium or aluminum or ammonium salt taken in amount of 3-30% by weight, above polyacrylmide taken in amount of 0.2-2% by weight, remainder is water.

EFFECT: EFFECT: increased water and behind-the-casing flow isolation time.

3 ex

Description

The invention relates to oil and gas production, in particular to methods for the elimination of water inflows and casing flows.

A known method of isolating the absorption zones during drilling and well repair, involving the use of a composition for isolating the absorption zones, containing, wt.%: Bentonite 5-8, g-radiation radiated polyacrylamide 0.4-0.6, sodium silicate 0.6-1 , 6 and the rest of the water [1].

The closest analogue to the claimed invention is a method of isolating water inflows by injecting into the reservoir a composition containing, wt.%: Anionic polyacrylamide 0.5-2.0, condensed sulphite-alcohol stillage or lignosulfonate 0.75-1.5, wood flour 1.0-4.0, sodium or potassium dichromate 0.02-0.05, sodium silicate 2.0-8.0, the rest is water [2].

A disadvantage of the known methods is the insufficient strength of the resulting gel, as well as the temporary nature of the insulation when exposed to formation water.

The objective of the invention is to increase the duration of isolation of water inflows and annular flows.

The problem is solved in that in the method of isolating water inflows, including injecting into the formation through a well a composition containing polyacrylamide, sodium silicate and water, polyacrylamide treated in the solid phase with accelerated electrons at a dose of 0.3-10 Mrad is used as the specified composition - 5-15% suspension of said polyacrylamide in an aqueous solution of sodium silicate density of 1.2-1.5 g / cm ^3, and after the injection of the slurry is carried out additional download aqueous system composition, wt%: Single soluble salt. tsiya or magnesium or aluminum or ammonium 3-30, said polyacrylamide 0.2-2, rest water.

Polyacrylamide injected into the reservoir in an aqueous solution of sodium silicate of the specified density does not dissolve after contact with water, but only swells to a limited extent. This allows you to pump the swollen dispersed gel into the reservoir. The lower value of the dose interval - 0.3 Mrad - defines the lower limit of the insolubility of polyacrylamide. At lower doses, polyacrylamide is noticeably soluble in water. The upper value of the dose limit - 10 Mrad - is determined by the fact that exceeding it leads to excessively hard gels that swell poorly. Using a solution of sodium silicate with a density of 1.2-1.5 g / cm ³ for the preparation of a suspension of polyacrylamide allows you to get a suspension with a concentration of 5-15%. At higher concentrations due to the increase in viscosity, it is not amenable to pumping through pipes. A concentration of less than 5% is not practical because an excess of free sodium silicate may subsequently block low permeable productive portions of the formation.

An aqueous solution of sodium silicate is selected with a density of 1.2-1.5 g / cm ³ , since in this case the dispersion of the swollen polymer has positive buoyancy, does not separate for a long time, which leads to a more efficient treatment of the annular flow area.

After injection of the specified suspension, a subsequent injection of an aqueous system is carried out containing a soluble salt of a strong acid - for example, sulfuric, hydrochloric, orthophosphoric with a cation of calcium, magnesium, aluminum, ammonium. These salts react with sodium silicate bound in a dispersed PAA gel.

This does not happen immediately, but after the displacement of a free solution of sodium silicate from the gel phase. In the future, a chemical reaction occurs of the formation of silicates of the above cations and a silica gel between PAA gel particles. To increase the uniformity of curing of silicate in the reservoir, the water system contains 0.2-2% PAA (processed as described above), which acts as a thickener. At a concentration above 2%, the viscosity of the system is excessively high for pumping it into the well, and at a concentration of less than 0.2% it is ineffective. The result of the interaction of sodium silicate and salt is the formation of a relatively rigid framework. In this case, the concentration of silicate in the gel decreases and it begins to swell. The result is a system containing swollen gel particles of PAA reinforced with a rigid structure of silicates. Such a system has increased mechanical strength and can be used to isolate water inflows, annular flows, insulation works for a longer period of time.

Example 1

To test the method assembled model annular space. The model is a glass pipe with an internal diameter of 15 mm and a length of 50 cm. Inside the pipe there is a cylinder of artificial stone with a diameter of 13 mm and a length of 50 cm. The volume of the annular gap is 22 cm ³ . On each side of the pipe is provided the input and selection of fluid. Using a solid phase treated with ionizing radiation — accelerated electrons — at a dose of 0.3 Mrad, PAA polyacrylamide was prepared by mixing with a 5% suspension of this swollen polymer in an aqueous solution of sodium silicate with a density of 1.5 g / cm ³ . We uploaded it to the reservoir model. They were sold into the reservoir with a composition containing 30 wt.% Calcium chloride, 0.2% of the same polyacrylamide and 69.8% of water. Weathered the system for 5 hours. Water was forced into the reservoir model to determine the effectiveness of insulation. Result - insulation withstood a pressure drop of 34 atm.

Example 2

A 15% suspension of swollen PAA treated with ionizing radiation — accelerated electrons — 5 Mrad in a water solution of sodium silicate with a density of 1.3 g / cm ^{3 was} pumped into a model of annular space, as in Example 1, and pressed through with its aqueous system, containing, wt.% 1 - of the same above PAA, 10 - aluminum alum and 89 - water. After holding for 5 hours, water was pushed into the formation to determine the effectiveness of insulation. The result - the insulation withstood a pressure drop of 35 atm.

Example 3

In the annular space model, as in example 1, a 10% suspension of swollen PAA, treated with ionizing radiation — accelerated electrons — at a dose of 10 Mrad, in an aqueous solution of sodium silicate with a density of 1.2 g / cm ^{3 was} pumped and pressed through with an aqueous system, containing, wt.% 0.5 - of the same above PAA, 10 - ammonium sulfate and 89.5 - water. After holding for 5 hours, water was pushed into the formation to determine the effectiveness of insulation. The result - insulation withstood a pressure drop of 31 atm.

Information sources

1. RF patent No. 2033518, publ. 04/20/1995.

2. RF patent №2136878, publ. 09/10/1999.

Claims (1)

A method of isolating water inflows, including injecting into the formation through a well a composition containing polyacrylamide, sodium silicate and water, characterized in that polyacrylamide treated in the solid phase with accelerated electrons in a dose of 0.3-10 Mrad is used as the specified composition — 5 -15% suspension of the specified polyacrylamide in an aqueous solution of sodium silicate with a density of 1.2-1.5 g / cm ³ , and after injection of this suspension, an additional aqueous system of the composition is carried out, wt.%: Soluble calcium or magnesium salt, silt and aluminum, or ammonium 3-30, the specified polyacrylamide 0.2-2, water - the rest.