RU2466172C1 - Composition for water insulation works - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: composition for water insulation works, including a sodium silicate, concentrated acid: orthophosphoric acid, hydrochloric, sulfuric or acetic acid and fresh water, additionally contains monoethanolamine at the following ratio of components, wt %: sodium silicate 5.0-12, specified concentrated acid 0.65-1.8, monoethanolamine 0.17-0.7, water - balance.

EFFECT: increased time of compositions gelling, increased strength and improved viscosity characteristics of a produced gel.

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Description

The invention relates to the oil and gas industry, in particular to the limitation of water inflow in producing wells, and can be used to equalize the injectivity profiles and isolate the washed zones of injection wells.

One of the analogues for the claimed composition is the composition described in [US Pat. US No. 834343, 1981], which provides for the use of sodium soda liquid glass, concentrated acid, including saline, and water. In this case, 40% sodium silicate, water containing 2% KCl, and 31, 45 wt.% Hydrochloric acid are used in an amount necessary to achieve a pH of 8-8.5. Following the addition of acid during gel formation, it is broken for 10 minutes. However, such a system has a short gelation time (t _max = 1 h 18 minutes at T = 20 ° C and 14 minutes at 75 ° C), which can lead to gelation of the system even on the surface before injection into the well.

The prototype of the invention is a gel-forming composition to limit the flow of water into the well [US Pat. RF №2418030, С09К 8/512]., Including in wt.%: Sodium silicate 3.0-6.0, concentrated acid (H ₃ PO ₄ or HCl or H ₂ SO ₄ ) 0.1-0.6, acrylic acid 4.0-10.0, polymerization initiator 0.4-1.5. The disadvantages of this composition are low manufacturability due to the short gelation time (t max - 5.5 hours), low strength characteristics. Apparently, the polyacrylic polymer formed during the reaction, reduces the strength characteristics.

The aim of this invention is to increase the gelation time of the compositions, increase the strength and improve the viscosity characteristics of the resulting gel.

This goal is achieved in that the composition for waterproofing works, including sodium silicate, concentrated acid: phosphoric, hydrochloric, sulfuric or acetic and fresh water, according to the invention additionally contains monoethanolamine, in the following ratio of components:

Sodium silicate 5.0 ÷ 12% Specified concentrated acid 0.65 ÷ 1.8% Monoethanolamine 0.17 ÷ 0.8% Water rest

The proposed composition in comparison with the prototype contains a new product monoethanolamine, therefore, the claimed invention meets the criterion of "novelty."

Acetic acid, acting in those percentages, as well as the indicated concentrated acids, was introduced to expand the range of available affordable inexpensive reagents so that, if necessary (for urgency of work, inaccessibility of other acids), replace the above acids.

In the present invention, when monoethanolamine is added, there is an increase in gelation time and a decrease in viscosity in the liquid glass-acid system.

Gelation in a liquid glass - acid system is the formation of hydrogen bonds between polysilicic acid molecules after adding any kind of acid (for example, phosphoric, hydrochloric or acetic) to liquid glass. To slow down gelation, a competitive reagent must be introduced, which will block the centers (points) of the formation of hydrogen bonds. We selected (found) such a reagent - monoethanolamine (MEA).

The MEA contains a nitrogen atom in its molecule, which has an unshared electron pair capable of forming donor-acceptor bonds, for example, with hydrogen protons. Therefore, for example, MEA is used as an easily regenerated absorber of acid gases (H ₂ S, CO ₂ and others). Given the above, we can assume the following mechanism of action of MEA as an inhibitor of gelation. Apparently, before the acid is added to the system, the OH group of the MEA interacts with oxygen, which carries a negative charge of the anion polysilicate:

NH ₂ CH ₂ CH ₂ OH ... -O- (SiO-O-) _n-1 SiO-O ^- ... HOCH ₂ CH ₂ NH ₂

where n is the silicate module of sodium polysilicate.

увеличивает кислотные свойства ОН группы МЭА, что еще боле упрочняет ее связь с кислородом полисиликат анионаAfter the addition of acid, hydrogen ions begin to interact with NH ₂ groups. Formed group

increases the acid properties of the OH group of the MEA, which even more strengthens its bond with oxygen anion polysilicate

на кислород полисиликат аниона с образованием поликремниевой кислотыAs mentioned above, the MEA easily regenerates the absorbed hydrogen ion, that is, its basicity is not as high as the polysilicate of the anion. Obviously, over time, a hydrogen ion transfers from the group

polysilicate anion with oxygen to form polysilicic acid

The sign of reversibility in the given reaction means the establishment of chemical equilibrium with a certain constant equilibrium, depending on the basicity constants of the MEA and the polysilicate anion.

The sample formulations and their gel-forming parameters are shown in tables 1-4, the viscosity properties are shown in tables 5-8.

Based on the last equilibrium reaction, it is easy to conclude that an increase in the concentration of MEA in the system will shift the equilibrium towards the formation of its protonated state (up arrow), and a decrease in it will shift the equilibrium towards the formation of polysilicic acid (down arrow) (Table 1-4, samples 3, 4, 5, 6).

If MEA is introduced into liquid glass before acid, then with the subsequent introduction of an acid containing protons, a "capture" of part of the protons by monoethanolamine will occur. But over time, as a result of chaotic Brownian motion in random close collisions, these protons will transfer to stronger oxygen centers of silicates, with the formation of hydrogen bonds and spatial structures. Thus, the time of continuous gelation in the liquid glass-acid system is prolonged (slowed down).

In the proposed solution, when adding monoethanolamine, a decrease in the viscosity of the system also occurs. Obviously, this is due to the slowdown (inhibition) of the processes of structural gelation as a result of "wedging" of the protonated MEA between the molecules of silicates. Tables 5-8 provide examples of viscosity reduction when adding MEA.

Table 5 Components, wt.% No. of experiments one 2 3 four Sodium silicate eleven eleven eleven eleven Sulphuric acid 1,5 1,5 1,5 1,5 Monoethanolamine - 0.25 0.5 0.7 Water 87.5 87.25 87.0 86.8 Viscosity, MPa * s 2,4 1.81 1,53 1.4

Table 6 Components, wt.% No. of experiments one 2 3 four Sodium silicate eleven eleven eleven eleven Hydrochloric acid 1.65 1.65 1.65 1.65 Monoethanolamine - 0.25 0.5 0.7 Water 87.35 87.1 86.85 86.65 Viscosity, MPa * s 2.5 1.95 1,6 1.4

Table 7 Components, wt.% No. of experiments one 2 3 four Sodium silicate 9.0 9.0 9.0 9.0 Acetic acid 1,5 1,5 1,5 1,5 Monoethanolamine - 0.25 1,5 1,5 Water 89.5 89.25 89.0 88.8 Viscosity, MPa * s 2.0 1.8 1,5 1.3

Table 8 Components, wt.% No. of experiments one 2 3 four Sodium silicate 9.06 9.06 9.06 9.06 Orthophosphoric acid 1,6 1,6 1,6 1,6 Monoethanolamine - 0.25 0.5 0.7 Water 89.34 89.09 88.84 88.64 Viscosity, MPa * s 1,920 1,780 1,430 1,300

The composition is prepared as follows.

At the first stage, diluting from commercial 40% liquid glass with a module of 2.9-3.1, density 1470-1500 kg / m ^{3 by} diluting with water, a liquid glass solution with a calculated concentration of sodium silicate is prepared. Then the calculated amount of monoethanolamine is added, the mixture is mixed for 15 minutes on a Voronezh mixer at 3000 rpm. The mixture is kept at rest for 30 minutes, then the calculated amount of acid is added to the mixture.

The most important operational and technological characteristics of the claimed composition are the gelation time (or yield loss), plastic viscosity and viscosity properties that characterize pumpability, especially in the formation. The reservoir temperature was simulated in a water thermostat.

During gelation, the time was taken when the sample stopped flowing when the tube was tilted.

The viscosity of the compositions was determined on viscometers VPZh.

The strength of the gels was measured by Rebinder cones with angles of 30 and 60 ° according to the depth of their introduction into the test samples.

Monoethanolamine produced according to TU 2423-159-00203335-2004 is a colorless or yellowish transparent liquid with a density of 1015-1018 kg / m ³ at 20 ° C.

As can be seen from tables 1-4, the introduction of MEA into the liquid glass - acid system increases the gelation time from 10 minutes to 500 minutes (Table 1-4, samples 1, 3, 4, 5, 6). An increase in the MEA content above 0.7% is not economically feasible, since due to a shift in the equilibrium according to reaction 1 and an increase in protonation, the gelation time sharply increases to 36-38 hours, which is technologically unacceptable (Table 2, sample 6, table 4, sample 6), and a decrease below 0.17% sharply reduces this time (Table 1-4, sample 11).

The increase in the content of sodium silicate above 12%, is also impractical, because no property improvement occurs. With a decrease in the sodium silicate content below 5%, the gelation time and strength also decrease (Tables 1-4, samples 4, 13).

With a decrease in acid below 0.65%, no gelation is observed, and above 1.8%, there is a sharp decrease in the gelation process time (Table 1-4, samples 9, 10).

The inventive composition differs from the prototype in that it has a longer gelling time - 500 minutes, against 330, a large plastic strength of 140 kN / m ² against 14.6 kN / m ² .

The inventive composition due to the long gelation time can be used for large-scale flooding with deep penetration through aquifers and a large radius of coverage.

Claims (1)

Composition for waterproofing works, including sodium silicate, concentrated acid: phosphoric, hydrochloric, sulfuric or acetic and fresh water, characterized in that it additionally contains monoethanolamine in the following ratio, wt.%:
Sodium silicate 5,0-12 Specified concentrated acid 0.65-1.8 Monoethanolamine 0.17-0.7 Water Rest