RU2277573C1 - Gel-forming formulation to shut off water inflow into well - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: invention relates to gel-forming formulation to shut off water inflow into well for creating insulating shields and can be used to control intake capacity of injecting wells and to increase waterflooding-mediated coverage of formation. Formulation according to invention comprising water-soluble polymer (0.3-1.0%), polyvalent metal salt (0.03-0.1%), ammonium chloride (0.2-1.0%), and water has, polyacrylamide or carboxymethylcellulose as water-soluble polymer, chromium acetate or chromium potassium sulfate as salt, and additionally contains 1.0-10.0% of urea-formaldehyde resin. Invention results in increased quality of insulating properties of formulation and quality of controlling intake profile of injecting wells due to improved strength and adhesion characteristics of formulation with resulting structure of crosslinking gel preserved. Gelation and viscosity time control are also enabled.

EFFECT: improved performance characteristics of formulation.

2 tbl

Description

The proposal relates to the oil industry, in particular to gel-forming compositions for isolating water inflow into wells, to create insulating screens, and can be used to control the injectivity profile of injection wells and increase the coverage of the formation by water flooding.

Known gel-forming composition for isolating water inflow into the well, containing hydrolyzed polyacrylamide, a crosslinking agent (for example, potassium chrome alum) and water (AS USSR, No. 985255, IPC ³ E 21 B 33/138, publ. 30.12.82, bull. No. 48). The disadvantage of this composition is the lack of effectiveness and low strength of the resulting gel.

Known gel-forming composition for isolating water inflow into the well based on polyacrylamide, a crosslinking agent (for example, chrome alum), bentonite clay and water (AS No. 1731942, IPC ⁵ E 21 B 43/22, 33/133, 33/13, published 07.05.92, bull. No. 17).

In a known composition during the interaction of these reagents, a gel formation process takes place, which allows it to be used to isolate water inflow.

The disadvantage of the composition is that with the introduction of bentonite clay, a flocculation process occurs, as a result of which an inhomogeneous mass is formed in the form of globules, which negatively affects the clogging ability of the composition and the quality of insulation.

In addition, this composition is subject to destruction due to the duration of clay swelling in reservoir conditions, which leads to a decrease in the strength properties of the composition and a decrease in the insulation efficiency.

The closest to the proposed technical essence and the achieved result is a gelling composition for isolating water inflow into the well, including a water-soluble polymer, salts of polyvalent metals, ammonium chloride and water (RF patent No. 2169256, IPC ⁷ E 21 V 43/22, publ. 2001, .). Polyacrylamide is used as a water-soluble polymer, chromium acetate is used as a salt of polyvalent metals. The composition is used in a method for developing a waterlogged oil deposit, which provides for the regulation of oil field development, isolating water inflow into the well, and creating insulating screens with improved technological parameters. An aqueous solution of polyacrylamide reacts with an aqueous solution of chromium acetate containing an ammonium chloride stabilizer, which results in the formation of a continuous gel with a three-dimensional crosslinked structure, which improves the efficiency of isolating water inflow into the well and regulating the injectivity profile of injection wells. The strength of the gel increases as a result of a decrease in the thermal degradation of the polymer and the formation of the gel in the entire volume. A disadvantage of the known composition is its low efficiency when water inflow into the well is used to isolate the injectivity profile of injection wells, since the gel formed is removed back from the well production, which is associated with insufficiently high strength and adhesive properties of the composition’s interaction with the formation rock.

The technical objective of the proposal is to increase the insulating properties of the gel-forming composition and the quality of regulation of the injectivity profile of injection wells by increasing its strength and adhesive characteristics while maintaining the resulting structure of the crosslinked gel with simultaneous regulation of gel formation and viscosity. Extension of resources of the applied components.

The problem is solved due to the gel-forming composition for isolating water inflow into the well, containing a water-soluble polymer, a polyvalent metal salt, ammonium chloride and water. What is new is that it contains polyacrylamide or carboxymethyl cellulose as a water-soluble polymer, chromium acetate or chromium potassium alum as a salt of a polyvalent metal, and additionally urea-formaldehyde resin in the following ratio of components, wt.%:

specified water soluble polymer 0.3-1.0 specified polyvalent metal salt 0.03-0.1 ammonium chloride 0.2-1.0 urea-formaldehyde resin 1.0-10.0 water rest

The increase in the strength and adhesion characteristics of the gel-forming composition is due to additional structuring by the molecules of the urea-formaldehyde resin of polyacrylamide or carboxymethyl cellulose with salts of chromium acetate or chromium-potassium alum and ammonium chloride. As a result of this reaction, a cross-linked gel is formed, which is a strong structure with a pronounced synergistic effect with a certain ratio of components.

Thus, urea-formaldehyde resin appears in a new quality as an additional structuring agent and its use in a gel-forming composition provides a gel with high insulating properties, allows you to expand the resources of the original ingredients and preserves the resulting structure of a cross-linked gel with simultaneous regulation of gelation and viscosity, improving the quality of regulation of the injectivity profile injection wells, which allows to expand the functionality of gelling with pose.

In the preparation of the gelling composition, the following reagents are used:

as a water soluble polymer:

- polyacrylamide (PAA) - domestic according to TU 6-16-2531-81, TU 6-01-1049-81, TU 14-6-121-75, imported with a molecular weight of (3-15) · 10 ⁶ ;

- carboxymethyl cellulose (CMC) according to TU 6-55-36-90, TU 2231-002-50277563-2000, imported - TYLOSE ЕНМ, ЕНН brands;

as a salt of polyvalent metals:

- chromium acetate according to TU 6-00204197-263-97 as amended. No. 1, TU 2499-001-50635131-00 is a low-viscosity 50% aqueous solution of dark green color;

- potassium alum according to GOST 4162-79.

Ammonium chloride - GOST 3773-00.

Urea-formaldehyde resin according to GOST 14231-88.

The analysis of patent and scientific and technical information made it possible to draw a conclusion about the absence of a gel-forming composition, which is characterized by characteristics identical to the set of essential features of the claimed composition, and the influence of distinctive features on the specified technical result has not been established, therefore, the proposed gel-forming composition meets the criteria of "novelty" and "inventive step".

The proposed gelling composition is prepared as follows.

A water-soluble polymer (PAA or CMC) is prepared by dosing into water of any density with stirring for one hour. Then, the salt of the polyvalent cation (chromium acetate or chromium potassium alum), urea-formaldehyde resin is introduced into the resulting solution and mixed for 30 minutes. Prepare a 20% solution of ammonium chloride in advance until completely dissolved. Then, a certain amount of a 20% solution of ammonium chloride is added to the previously prepared composition, stirred for 10-20 minutes and left to gel for a while.

The prepared solutions are used to determine the gelation time (structuring), to determine the viscosity and strength of the composition. The gelation start time and viscosity are determined by a standard method. Strength is estimated by the shear strength of the gel at a shear rate of 1.5 s ^-1 measured on a Reotest-2 rotational viscometer. The measurement results are shown in table 1.

Table 1 No pp Gel-forming composition, wt. % The time of gelation., Days The viscosity of the beginning., MPa · s Shear strength, Pa Water growth. polym. Stapler Chlorine. ammon. Kar-bam. resin forms Water Clay PAA CMC Ats.khr. Chrome mocha one 2 3 four 5 6 7 8 9 10 eleven 12 one 0.1 0,03 - - 99.87 - - 7.6 no gel 2 0.1 0,03 0.2 - 99.67 - - 8.1 no gel 3 0.1 0,03 0.2 1,0 98.67 - - 8.4 no gel four 0.3 0.01 - - 99.69 - - 6.8 - 5 0.3 0,03 - - 99.67 - 3-4 10 200 6 0.3 0,03 0.2 - 99.47 - 3-4 fifteen 310 7 0.3 0,03 0.2 0.5 98.97 - 3-4 fourteen 320 8 0.3 0,03 0.2 1,0 98.47 - 3-4 fourteen 430 9 0.3 0,03 0.2 3.0 96.47 - 3-4 fourteen 530 10 0.3 0,03 0.2 5,0 94.47 - 3-4 fifteen 610 eleven 0.3 0,03 0.2 10.0 89.47 - 2-3 twenty 1000 12 0.3 0,03 0.5 - 99.17 - 3 fourteen 350 13 0.3 0,03 0.5 0.5 98.67 - 3 fourteen 365 fourteen 0.3 0.06 0.5 1,0 98.14 - 2-3 fifteen 560 fifteen 0.3 0.06 0.5 3.0 96.14 - 2-3 16 830 16 0.3 0.06 0.5 5,0 94.14 - 2-3 16 950 17 0.3 0.06 0.5 10.0 89.14 - 2-3 16 1300 eighteen 0.3 0.01 - - 99.69 - - 7.5 no gel 19 0.3 0.01 0.2 - 99.49 - - 8.0 no gel twenty 0.3 0.01 0.2 3.0 96.49 - - 8.5 no gel 21 0.5 0.1 - - 99,4 - 3 23 880 22 0.5 0.1 0.2 - 99,2 - 2-3 thirty 895 23 0.5 0.1 0.2 5,0 94.2 - 2-3 thirty 1100 24 0.5 0.1 0.5 5,0 93.9 - 1-2 35 1560 25 0.5 0.1 0.8 5,0 93.6 - 2-2.5 34 1560 26 0.5 0.1 1,0 5,0 93,4 - 1-2,5 35 1500 27 0.5 0.1 0.5 - 98.9 - 2 27 895 28 0.5 0.1 0.5 0.5 98.4 - 2 28 900 29th 0.5 0.1 0.5 1,0 97.9 - 1-2 26 1200 thirty 0.5 0.1 0.5 3.0 95.9 - 1-2 thirty 1360 31 0.5 0.1 0.5 10.0 88.9 - 1-1.5 35 2000 32 0.5 0.1 0.5 15.0 83.9 - 1-1.5 35 1950 33 0.5 0.1 0.5 20,0 78.9 - 1-1.5 36 1980 34 0.5 0.1 0.1 3.0 96.3 - 3 24 1875 35 1,0 0.1 0.5 5,0 93,4 - one 75 2450 36 1,0 0.1 1,0 5,0 92.9 - one 85 2745 37 1,0 0.1 1,0 10.0 87.9 - one 90 3100 38 1,0 0.1 1,0 15.0 82.9 - one 125 3700 39 1,1 0.1 1,0 10.0 87.8 - one 125 3250 40 1,5 0.1 1,0 10.0 87.4 - one 155 3945

Continuation of table 1 one 2 3 four 5 6 7 8 9 10 eleven 12 41 0.1 0,03 0.2 1,0 98.67 - - 4.3 no gel 42 0.3 0,03 - - 99.67 - 5-6 7.2 175 43 0.3 0,03 0.2 - 99.47 - 5-6 7.5 180 44 0.3 0,03 0.2 5,0 94.47 - four 13 480 45 0.3 0,03 0.2 5,0 94.47 - 4-5 12.5 470 46 0.5 0.1 0.2 5,0 94.2 - four 25 1200 47 0.5 0.1 0.2 10.0 89.2 - 3,5 35 1450 48 1,0 0.1 0.2 5,0 93.7 - 3 70 1950 49 1,5 0.1 0.2 5,0 93.2 - 3 135 2700 fifty 0.3 0,03 - - 97.67 2.0 flocculation - - 51 0.5 0.1 - - 97.4 2.0 flocculation - - 52 0.5 0.1 - - 94.4 5,0 flocculation - - 53 0.3 0,03 - - 97.67 2.0 flocculation - - 54 0.5 0.1 - - 97.4 2.0 flocculation - -

From table 1 it is seen that the properties of the gel depend on the quantitative content of the components of the composition. The optimal concentrations of the components are the compositions (8-11, 14-17, 23-26, 29-31, 34-37, 44-47), while the water-soluble polymer 0.3-1.0 wt.%, Salts of polyvalent metals 0 , 03-0.1 wt.%, Ammonium chloride 0.2-1.0 wt.%, Urea-formaldehyde resin 1.0-10.0 wt.%, Water - the rest.

When the content of the urea-formaldehyde resin is less than 1.0 wt.%, The shear strength of the gel is 320 Pa (composition 7) and does not significantly differ from the prototype 310 Pa (composition 6).

With the introduction of urea-formaldehyde resin, the shear strength of the proposed composition increases compared to the prototype (compositions 6, 12), additional structuring and an increase in adhesive properties occur.

When the content of the water-soluble polymer is less than 0.3 wt.% And salts of polyvalent cations less than 0.03 wt.%, Gel formation does not occur and when mixed with urea-formaldehyde resin does not lead to the formation of a strong composition (compositions 3, 20.41) and does not provide an increase insulation work.

The increase in the content of water-soluble polymer is more than 1.0 wt.%, And urea-formaldehyde resin more than 10 wt.% Is impractical from an economic point of view, as well as from a technological point of view due to the high cost of the reagents and high viscosity of the compositions (more than 100 MPa · s). When injected into the reservoir, such a gelling composition does not allow penetration into the porous medium.

Analysis of the research results showed that the proposed composition has high strength values while maintaining the resulting structure of a crosslinked gel. The expansion of the components used does not reduce the level of indicators of the proposed composition. Allows you to adjust the timing of gelation and viscosity.

To assess the effectiveness of the insulating properties of the gel-forming composition, reduce water inflow and the quality of the regulation of the injectivity profile, experiments are carried out on bulk models of the reservoir in a generally accepted way. The reservoir model is a metal tube (50 cm long, 6.4 cm ² cross-sectional area) filled with quartz sand of a certain fraction, the change of which allows changing the permeability of the reservoir model. The formation model is first evacuated, saturated with water, the initial water permeability is determined, then gel-forming compositions are pumped in an amount of 0.5 pore volume. The model is kept for two days for complete gelation and completion of the process of adhesive interaction with the rock. Then turn over and in the opposite direction determine the permeability to water. Thus, they simulate the process of launching wells and oil production from the reservoir after conducting waterproofing works. In all experiments, the pressure drop between the ends of the reservoir model is 0.1 MPa.

The effect of isolation (E) is determined by the formula:

E = (K ₁ -K ₂ ) / K ₁ · 100%;

where K ₁ - water permeability to the injection of the proposed composition, μm ² ;

To ₂ - permeability to water after injection of the proposed composition, μm ² .

The research results are presented in table 2.

table 2 No pp Gel-forming composition, wt. % Permeability to water, microns ² The effect of isolation,% Water growth. polym. Stapler Chlorine. ammon. Urea form. resin Water before the injection of the composition after injection of the composition PAA CMC Ats.khr. Potassium chrome one 2 3 four 5 6 7 8 9 10 eleven one 0.3 0,03 0.2 1,0 98.47 12.5 0.3 98 2 0.3 0,03 0.2 3.0 96.47 12.6 0.4 97 3 0.3 0.06 0.5 3.0 96.14 12.6 0.4 97 four 0.3 0.06 0.5 5,0 94.14 12.7 0.3 98 5 0.5 0.1 0.2 5,0 94.2 12.9 0 one hundred 6 0.5 0.1 0.5 5,0 93.9 13.5 0.2 99 7 0.5 0.1 0.2 0.5 98.7 13.6 0.3 98 8 0.5 0.1 0.5 10.0 88.9 14.0 0.1 99

Table continuation one 2 3 four 5 6 7 8 9 10 eleven 9 0.3 0,03 0.2 5,0 94.47 12.6 0 one hundred 10 0.5 0.1 0.2 5,0 94.2 12.3 0.3 98 eleven 0.5 0.1 0.2 5,0 94.2 12.3 0.4 97 prototype 12 0.3 0,03 0.2 - 99.47 12,4 1,5 88 13 0.5 0.1 0.2 - 99,2 12.6 2.1 83 fourteen 0.5 0.1 0.5 - 98.9 12.6 1.9 85 fifteen 0.3 0,03 0.2 - 99.47 11.9 1,6 87

From table 2 it is seen that the proposed composition, in contrast to the prototype, has high insulation efficiency (97-100%) against 83-88% of the prototype.

Adhesion characteristics are determined by the nature of the fracture of the samples of the reservoir model. When the samples are destroyed, the proposed insulating composition is not destroyed, but preserves the structure of the crosslinked gel and remains firmly adhered to the reservoir model. The prototype composition does not form an associated structure with the reservoir model, which makes it possible to judge the increase in adhesion of the proposed insulating composition.

Thus, the test results of the proposed gelling composition indicate the possibility of obtaining gels with high strength and high adhesion to the formation rocks while maintaining the formed structure of the crosslinked gel and at the same time regulating the gelation and viscosity periods while expanding the resources of the components used.

Using the proposal allows to improve the quality of insulation work to limit water inflow into oil wells and the quality of regulation of the injectivity profile of injection work, which ensures additional oil production.

Claims (1)

A gel-forming composition for isolating water inflow into a well containing a water-soluble polymer, a polyvalent metal salt, ammonium chloride and water, characterized in that it contains polyacrylamide or carboxymethyl cellulose as a water-soluble polymer, chromium acetate or chromium potassium alum and additional carbamide as a polyvalent metal salt in the following ratio of components, wt.%: Water soluble polymer 0.3-1.0 Polyvalent Metal Salt 0.03-0.1 Ammonium chloride 0.2-1.0 Urea-formaldehyde resin 1.0-10.0 Water Rest