A thermally degradable hydrogel for temporary plugging under pressure

A technology of thermal degradation and hydrogel, which is applied in the direction of chemical instruments and methods, drilling compositions, etc., can solve the problems that have not been proposed, the limited conditions for environment-sensitive gels to be regulated, and the inability to effectively regulate them. The effect of high viscoelasticity

Active Publication Date: 2022-06-17
YANGTZE UNIVERSITY
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0005] However, in the field of pressure-filled temporary plugging in wells, due to the contradiction between the pressure-bearing capacity of gel slugs and gel-breaking performance, and the conditions that can be adjusted for environment-sensitive gels in wells are very limited, such as light, electricity, magnetism and Factors such as pH value cannot be effectively adjusted in the downhole environment
Therefore, the downhole self-breaking gel in the field of fracturing is not suitable for the field of temporary plugging under pressure in the well. At present, the concept of self-breaking gel has not been proposed in this field, and most of them adopt the method of physical gel breaking

Method used

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  • A thermally degradable hydrogel for temporary plugging under pressure
  • A thermally degradable hydrogel for temporary plugging under pressure

Examples

Experimental program
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Effect test

Embodiment 1

[0026] In this embodiment, the preparation method of thermally degradable gel comprises the following steps:

[0027] Step 1. Mix 2.0g acrylamide, 1.4g 2-acrylamide-2-methylpropanesulfonic acid, 0.4g n-butyl methacrylate, 0.4g acryloyloxyethyltrimethylammonium chloride and 20g water, stirring to dissolve;

[0028] Step 2. Place the mixed solution in a constant temperature reactor, set the reaction temperature to 22°C, continue stirring and feed N 2 ;

[0029] Step 3. 0.02g reducing agent 2,2'-azobis-(methyl 2-methylpropionate) and 0.06g potassium persulfate-sodium bisulfite (both mol of potassium persulfate and sodium bisulfite) The ratio of 1:1) was added to the above mixed solution, and in a dark environment, stirring was continued at constant temperature for 1h;

[0030] Step 4. After the above reaction product is cooled to room temperature, it is placed in a mixed solution with a mass ratio of ethanol and acetone of 1:1 to wash and precipitate several times to remove un...

Embodiment 2

[0036] In this embodiment, the preparation method of thermally degradable gel comprises the following steps:

[0037] Step 1. Mix 1.0g acrylamide, 2.2g N,N'-methylenebisacrylamide, 1.4g vinyl acetate and 25g water, stir to dissolve;

[0038] Step 2. Place the mixed solution in a constant temperature reactor, set the reaction temperature to 28°C, continue stirring and feed N 2 ;

[0039] Step 3. Add 0.03g reducing agent 2,2'-azo[2-methyl-N-(2-hydroxyethyl)propionamide] and 0.56g cerium ammonium nitrate to the above mixed solution, in a dark environment , continue stirring at constant temperature for 1.5h;

[0040]Step 4. After the above reaction product is cooled to room temperature, it is placed in the mixed solution of methanol and acetone with a mass ratio of 1:1 to wash and precipitate several times to remove unreacted initiators, monomers and oligomers;

[0041] Step 5. When drying under reduced pressure until the weight is constant, a white powdery solid, i.e., a therm...

Embodiment 3

[0044] In this embodiment, the preparation method of thermally degradable gel comprises the following steps:

[0045] Step 1. Mix 3.5g acrylamide, 1.2g N,N'-methylenebisacrylamide, 1.6g acryloxyethyldimethylbenzyl ammonium chloride and 22g water, stir to dissolve;

[0046] Step 2. Place the mixed solution in a constant temperature reactor, set the reaction temperature to 32°C, continue stirring and feed N 2 ;

[0047] Step 3. Add 0.04g of reducing agent 2,2'-azobis-(methyl 2-methylpropionate) and 0.64g of ceric ammonium nitrate to the above mixed solution, and continue stirring at constant temperature for 2h in a dark environment;

[0048] Step 4. After cooling the above reaction product to room temperature, place it in acetone for washing and precipitation several times to remove unreacted initiator, monomer and oligomer;

[0049] Step 5. When drying under reduced pressure until the weight is constant, a white powdery solid, i.e., a thermally degraded polymer, is obtained; ...

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Abstract

The invention provides a thermally degradable hydrogel for temporary plugging under pressure. The thermally degradable hydrogel for temporary plugging under pressure uses monomers, azo-type reducing agents and oxidants as raw materials, and the azo-type reducing agents are There are two different types of functional groups, one is the thermally degradable azo group, and the other is the functional group at both ends that is easy to react with the oxidant, and each of the two ends generates a free radical, which can be combined with Vinyl monomers are polymerized and linked into long polymer chains. In the present application, the unstable azo group is introduced into the long chain of the polymer by adopting redox method, so the unstable long chain polymer containing the azo group is prepared, and the gel material is endowed with high viscoelasticity (10 6 mPa.s) at the same time, making it thermally self-degradable, which can effectively realize the temporary plugging of the gel slug in the wellbore under pressure, and the temporary plugging time under pressure can reach up to 50h, and then gradually complete the degradation into a fluid state.

Description

technical field [0001] The invention relates to the technical field of oil under pressure operation, in particular to a thermal self-degradable temporary plugging hydrogel for under pressure operation. Background technique [0002] Pressurized operation is an operation method of tripping down the pipe string and downhole tools under the condition of wellhead pressure. It can realize downhole operation without changing the pressure in the well, which is very important for protecting reservoirs, improving water injection efficiency and oil and gas recovery. rate is significant. The plugging technology in the process of pressurization mainly includes mechanical plugging and chemical plugging in the wellbore. When the well wall is seriously polluted, a large amount of dead oil and dead wax are attached, or there are problems such as tubing scaling, corrosion perforation, long-section porous tubing strings or oil-water wells in tool strings, etc., when mechanical plugging cannot...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C08F220/56C08F220/58C08F220/18C08F220/34C08F222/38C08F218/08C08F220/54C08F226/02C09K8/508C09K8/516
CPCC08F220/56C08F222/385C08F218/08C08F220/58C09K8/5083C09K8/516C08F220/54C08F226/02
Inventor 程立廖锐全李振汪瀛
Owner YANGTZE UNIVERSITY
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