Temperature-resistant and salt-resistant gel for deep plugging control and preparation method of temperature-resistant and salt-resistant gel

Abstract

The invention relates to a temperature-resistant and salt-resistant gel for deep plugging and a preparation method thereof. The gel comprises a main agent, a cross-linking agent, a cross-linking promoting agent, a reinforcing agent, a stabilizing agent and water. The main agent is an acrylamide / 2-acrylamide-2-methylpropanesulfonic acid / N-vinyl pyrrolidone (AM / AMPS / NVP) terpolymer, the temperature-resistant and salt-resistant gel for deep plugging control is suitable for oil reservoirs with the temperature of 110-130 DEG C and the formation water mineralization degree of 5 * 10 < 5 >-10 * 10 < 5 > mg / L, the gelling time is controllable within 73-98 hours, the gel strength after gelling is high, the thermal stability is good, and the temperature-resistant and salt-resistant gel for deep plugging control is suitable for the oil reservoirs with the temperature of 110-130 DEG C and the formation water mineralization degree of 5 * 10 < 5 >-10 * 10 < 5 > mg / L. And long-time deep effective plugging of high-temperature and high-salt oil reservoirs can be realized.

Description

Technical Field

[0001] The present invention relates to the field of oilfield chemistry, and specifically relates to a gel for deep profile control and water plugging with temperature and salt resistance, which can be used as a water plugging agent for deep profile control and water plugging in high-temperature, high-salt and high-water-cut oilfields. Background Art

[0002] Most of the high-water-cut oilfields in the eastern part of China have entered the late stage of water flooding development. Long-term water injection development has led to the emergence of high-permeability water channeling channels in the reservoir. During the late stage of water flooding, the injected water mainly channels along the high-permeability channels, resulting in a significant reduction in the water flooding sweep efficiency and a sharp decrease in the water flooding recovery rate. At the same time, a large amount of water production from oil wells increases the burden and cost of produced fluid treatment, directly affecting the economic benefits of oilfield development. Profile control and water plugging technology is the main technology for water control and oil stabilization in high-water-cut oilfields, and the key lies in the performance of the profile control and water plugging agent. Among them, gel-based profile control and water plugging agents are the most commonly used and widely applicable profile control and water plugging agents in oilfields at present. However, the application of gel-based profile control and water plugging agents in harsh reservoir conditions such as high temperature and high salt still faces many technical difficulties, mainly reflected in the following aspects: (1) The structure of the polymer in the gel will be damaged under high-temperature and high-salt conditions, resulting in varying degrees of degradation of the polymer, so that the gel strength cannot meet the plugging requirements; (2) The volume of the gel will shrink in high-temperature and high-salinity formation water, accompanied by dehydration phenomenon, so that the stability of the plugging agent cannot meet the normal profile control and water plugging requirements; (3) The gelation time of gel-based plugging agents shortens with the increase of temperature, and conventional gel-based plugging agents are prone to gelation in the wellbore or near-wellbore areas, unable to meet the requirements of deep profile control and water plugging. Therefore, the above problems are all technical problems that need to be solved by gel-based deep profile control and water plugging agents in high-temperature and high-salt reservoirs.

[0003] Patent CN110790959A discloses a water-soluble phenolic resin crosslinking agent for low-temperature and rapid gelation of gel and its preparation method and application. The above plugging agent uses water-soluble phenolic resin to crosslink with the polymer too quickly, with a short gelation time, weak gel strength, and poor stability, unable to meet the technical requirements of deep profile control and water plugging.

[0004] Patent CN103232839A discloses a water plugging agent suitable for water plugging and profile control in high-temperature and high-salt reservoirs. The plugging agent uses a phenolic crosslinking agent and is applicable to oil reservoirs at 90-150°C, with high gelation strength, but the gelation time is less than 48h, unable to meet the requirements of deep profile control.

[0005] Therefore, it is of great significance to develop a gel plugging agent suitable for deep profile control and water plugging with temperature and salt resistance for water control and oil stabilization in high-temperature and high-salt reservoirs during the high-water-cut period and improving the recovery rate in the late stage of water flooding. Summary of the Invention

[0006] In view of the deficiencies of the prior art, especially under the conditions of high-temperature and high-salinity reservoirs, the gel-like profile control and plugging agents have a fast gelation time and poor stability, making it difficult to meet the requirements of deep profile control and plugging in the formation. The present invention provides a gel for high-temperature and high-salinity deep profile control and plugging at a reservoir temperature of 110-130°C and a formation water salinity of 5×10 5 ~10×10 5 mg / L, and a preparation method thereof.

[0007] The technical solution of the present invention is as follows:

[0008] In a first aspect of the present invention, there is provided a gel for high-temperature and high-salinity deep profile control and plugging, which comprises a main agent, a crosslinking agent, a crosslinking promoter, a reinforcing agent, a stabilizer and water, and the mass percentage composition is as follows:

[0009] The main agent is 0.4% - 1.0%, and the main agent is an acrylamide / 2-acrylamido-2-methylpropanesulfonic acid / N-vinylpyrrolidone (AM / AMPS / NVP) terpolymer;

[0010] The crosslinking agent is 0.3% - 0.8%;

[0011] The crosslinking promoter is 0.02% - 0.06%;

[0012] The reinforcing agent is 1.0% - 2.0%;

[0013] The stabilizer is 0.2% - 0.6%;

[0014] The sum of the mass percentages of each component is 100%.

[0015] In the acrylamide / 2-acrylamido-2-methylpropanesulfonic acid / N-vinylpyrrolidone (AM / AMPS / NVP) terpolymer of the present invention, the NVP with a cyclic structure can not only enhance the high-temperature stability of the terpolymer, but also effectively protect the adjacent acrylamide groups from hydrolysis at high temperatures, and has better high-temperature resistance than partially hydrolyzed polyacrylamide (HPAM) and acrylamide / 2-acrylamido-2-methylpropanesulfonic acid (AM-AMPS) binary copolymers.

[0016] According to the present invention, preferably, the relative molecular weight of the acrylamide / 2-acrylamido-2-methylpropanesulfonic acid / N-vinylpyrrolidone (AM / AMPS / NVP) terpolymer is 3 million - 8 million, more preferably 5 million; the hydrolysis degree is 20% - 30%, more preferably 25 - 30%.

[0017] According to the present invention, preferably, the crosslinking agent is melamine resin, which can undergo a slow decomposition reaction under high-temperature conditions, and the generated hydroxymethyl can crosslink with the amide groups on the polymer chain, thereby prolonging the gelation time of the gel.

[0018] According to the present invention, preferably, the crosslinking accelerator is one of phenol, resorcinol, and hydroquinone. The crosslinking accelerator in the present invention can undergo a secondary crosslinking reaction with the unreacted amide groups on the polymer chain, thereby increasing the gel network density of further crosslinking and enhancing the gel strength.

[0019] According to the present invention, preferably, the crosslinking accelerator is hydroquinone.

[0020] According to the present invention, preferably, the reinforcing agent is a nano-silica dispersion. The reinforcing agent in the present invention can form hydrogen bonds with the acrylamide groups on the polymer molecules, increasing the density of the gel three-dimensional network structure. At the same time, after the nano-silica particles are adsorbed on the polymer molecules, a certain steric hindrance can be formed. On the one hand, it can delay the crosslinking reaction rate of the gel, and on the other hand, it can delay the further hydrolysis and oxidative degradation of the acrylamide groups, thereby enhancing the gel strength and stability.

[0021] According to the present invention, preferably, the effective content of the nano-silica dispersion is 30%, and the particle size is 10 nm to 30 nm.

[0022] According to the present invention, preferably, the particle size is 10 - 20 nm.

[0023] According to the present invention, preferably, the stabilizer is one of sodium nitrite, sodium sulfite, and thiourea

[0024] According to the present invention, preferably, the stabilizer is thiourea. Its main function is to react with the dissolved oxygen in water, reducing the dissolved oxygen content in water, thereby reducing the oxidative degradation of the polymer and further improving the gel stability.

[0025] According to the present invention, preferably, the water is formation water with a salinity of 5×10 5 ~10×10 5 mg / L.

[0026] According to the present invention, preferably, for the temperature- and salt-resistant deep profile control gel, at a reservoir temperature of 110 - 130 °C and a formation water salinity of 5×10 5 ~10×10 5 mg / L, the gelation time of the gel can be controlled within 73 hours to 98 hours. After gelation, the storage modulus is 12.6 Pa to 27.8 Pa, and the dehydration rate is less than 10% after aging at 130 °C for 180 days.

[0027] According to the present invention, preferably, the temperature- and salt-resistant deep profile control gel has the following mass percentage composition:

[0028] Acrylamide / 2-acrylamido-2-methylpropanesulfonic acid / N-vinylpyrrolidone (AM / AMPS / NVP) terpolymer 0.6% - 0.8%;

[0029] Melamine resin 0.3% - 0.6%;

[0030] Hydroquinone 0.02% - 0.05%;

[0031] Nano - silica dispersion 1.0 - 1.5%;

[0032] Thiourea 0.3% - 0.5%;

[0033] The balance is water;

[0034] The sum of the mass percentages of each component is 100%.

[0035] In the second aspect of the present invention, a preparation method of a gel for deep profile control with temperature and salt resistance is provided, including the following steps:

[0036] Add a cross - linker, a cross - linking promoter, a strengthening agent and a stabilizer to water in proportion, stir evenly, and then slowly add the main agent under stirring conditions, and stir at room temperature for 3 hours until completely dissolved; thus, a gel - forming liquid is obtained.

[0037] According to the present invention, the temperature of the high - temperature reservoir is 110°C - 130°C.

[0038] The present invention also provides the application of the gel for deep profile control with temperature and salt resistance in oilfield exploitation.

[0039] Preferably, the present invention provides the application of the gel for deep profile control with temperature and salt resistance as a water - plugging agent for deep profile control and plugging in high - temperature, high - salinity and high - water - cut oilfields.

[0040] The beneficial effects of the present invention are as follows:

[0041] (1) The gel for deep profile control and plugging with temperature and salt resistance of the present invention is applicable to deep profile control and plugging in high - temperature and high - salinity reservoirs with reservoir temperatures of 110 - 130°C and formation water salinity of 5×10 4 - 10×10 4 mg / L, and has a good effect of reducing water production and increasing oil production.

[0042] (2) The gel for deep profile control and plugging with temperature and salt resistance of the present invention has excellent performance, has the advantages of controllable gel - forming time, high strength after gel - forming and good thermal stability under high - temperature and high - salinity conditions, and can effectively plug high - temperature and high - salinity reservoirs for a long time.

[0043] (3) Under the conditions of high - temperature and high - salinity reservoirs, the gel for deep profile control and plugging with temperature and salt resistance of the present invention has a relatively long gel - forming time, adjustable gel - forming strength, can enter formations at different depths to form gels, realize plugging of high - permeability water - channeling channels in the deep formation, expand the subsequent water - flooding sweep coefficient, and thus improve the water - flooding recovery rate. Specific embodiments

[0044] The endpoints and any values disclosed in this text for ranges are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this text.

[0045] The first aspect of the present invention provides a gel for deep profile control and plugging resistant to temperature and salt. The gel is composed of a main agent, a crosslinking agent, a crosslinking promoter, a reinforcing agent, a stabilizer, and water, and the mass percentage composition is as follows:

[0046] The main agent is 0.4% - 1.0%, and the main agent is an acrylamide / 2-acrylamido-2-methylpropanesulfonic acid / N-vinylpyrrolidone (AM / AMPS / NVP) terpolymer;

[0047] The crosslinking agent is 0.3% - 0.8%;

[0048] The crosslinking promoter is 0.02% - 0.06%;

[0049] The reinforcing agent is 1.0% - 2.0%;

[0050] The stabilizer is 0.2% - 0.6%;

[0051] The sum of the mass percentages of each component is 100%.

[0052] In the acrylamide / 2-acrylamido-2-methylpropanesulfonic acid / N-vinylpyrrolidone (AM / AMPS / NVP) terpolymer of the present invention, the NVP with a cyclic structure can not only enhance the high-temperature stability of the terpolymer, but also effectively protect the adjacent acrylamide groups from being easily hydrolyzed at high temperatures, and has better temperature resistance than partially hydrolyzed polyacrylamide (HPAM) and acrylamide / 2-acrylamido-2-methylpropanesulfonic acid (AM-AMPS) binary copolymer.

[0053] According to the present invention, preferably, the relative molecular weight of the acrylamide / 2-acrylamido-2-methylpropanesulfonic acid / N-vinylpyrrolidone (AM / AMPS / NVP) terpolymer is 3 million - 8 million, more preferably 5 million; the hydrolysis degree is 20% - 30%, more preferably 25% - 30%.

[0054] According to the present invention, preferably, the crosslinking agent is melamine resin, which can undergo a slow decomposition reaction under high-temperature conditions, and the generated hydroxymethyl can crosslink with the amide groups on the polymer chain, thereby prolonging the gel formation time of the gel.

[0055] According to the present invention, preferably, the crosslinking accelerator is one of phenol, resorcinol, and hydroquinone. The crosslinking accelerator in the present invention can undergo a secondary crosslinking reaction with the amide groups on the polymer chain that have not participated in crosslinking, thereby increasing the gel network density of further crosslinking and enhancing the gel strength.

[0056] According to the present invention, preferably, the crosslinking accelerator is hydroquinone.

[0057] According to the present invention, preferably, the reinforcing agent is a nano-silica dispersion. The reinforcing agent in the present invention can form hydrogen bonds with the acrylamide groups on the polymer molecules, increasing the density of the gel three-dimensional network structure. At the same time, after the nano-silica particles are adsorbed on the polymer molecules, a certain steric hindrance can be formed. On the one hand, it can delay the crosslinking reaction rate of the gel, and on the other hand, it can delay the further hydrolysis and oxidative degradation of the acrylamide groups, thereby enhancing the gel strength and stability.

[0058] According to the present invention, preferably, the effective content of the nano-silica dispersion is 30%, and the particle size is 10 nm to 30 nm.

[0059] According to the present invention, preferably, the particle size is 10 - 20 nm.

[0060] According to the present invention, preferably, the stabilizer is one of sodium nitrite, sodium sulfite, and thiourea

[0061] According to the present invention, preferably, the stabilizer is thiourea. Its main function is to react with the dissolved oxygen in water, reducing the dissolved oxygen content in water, thereby reducing the oxidative degradation of the polymer and improving the gel stability.

[0062] According to the present invention, preferably, the water is formation water with a salinity of 5×10 5 ~10×10 5 mg / L.

[0063] According to the present invention, preferably, for the temperature- and salt-resistant deep profile control gel, at a reservoir temperature of 110 - 130 °C and a formation water salinity of 5×10 5 ~10×10 5 mg / L, the gelation time of the gel can be controlled within 73 hours to 98 hours. After gelation, the storage modulus is 12.6 Pa to 27.8 Pa, and the dehydration rate is less than 10% after aging at 130 °C for 180 days.

[0064] According to the present invention, preferably, the temperature- and salt-resistant deep profile control gel has the following mass percentage composition:

[0065] Acrylamide / 2-acrylamido-2-methylpropanesulfonic acid / N-vinylpyrrolidone (AM / AMPS / NVP) terpolymer 0.6% - 0.8%;

[0066] Melamine resin: 0.3% - 0.6%;

[0067] Hydroquinone: 0.02% - 0.05%;

[0068] Nano - silica dispersion: 1.0 - 1.5%;

[0069] Thiourea: 0.3% - 0.5%;

[0070] The balance is water;

[0071] The sum of the mass percentages of each component is 100%.

[0072] Preferably, the gel for deep - profile control with temperature and salt resistance of the present invention is composed of the following: AM / AMPS / NVP terpolymer 0.6%, melamine resin 0.3%, hydroquinone 0.03%, nano - silica dispersion 1.0%, thiourea 0.3%, and the balance is water.

[0073] Preferably, the gel for deep - profile control with temperature and salt resistance of the present invention is composed of the following: AM / AMPS / NVP terpolymer 0.7%, melamine resin 0.4%, hydroquinone 0.04%, nano - silica dispersion 1.2%, thiourea 0.4%, and the balance is water.

[0074] Preferably, the gel for deep - profile control with temperature and salt resistance of the present invention is composed of the following: AM / AMPS / NVP terpolymer 0.8%, melamine resin 0.5%, hydroquinone 0.05%, nano - silica dispersion 1.5%, thiourea 0.5%, and the balance is water.

[0075] Preferably, the salinity of the water used in all examples is 5 - 10×10 4 mg / L, and the particle size of the nano - silica dispersion is 10 - 20 nm.

[0076] In the second aspect of the present invention, a preparation method of the gel for deep - profile control with temperature and salt resistance is provided, including the following steps:

[0077] Add a cross - linker, a cross - linking accelerator, a reinforcing agent and a stabilizer to water in proportion, stir evenly, and then slowly add the main agent under stirring conditions and stir at room temperature for 3 hours until completely dissolved; thus, the gel - forming liquid is obtained.

[0078] According to the present invention, the temperature of the high - temperature reservoir is 110°C - 130°C.

[0079] The present invention also provides the application of the gel for deep - profile control with temperature and salt resistance in oilfield exploitation.

[0080] The present invention preferably provides an application of a gel for deep profile control with temperature and salt resistance in a water plugging agent for deep profile control and plugging in high-temperature, high-salt, and high-water-cut oilfields.

[0081] In addition, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combination methods.

[0082] Furthermore, any combination can be made between various different embodiments of the present invention as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

[0083] The present invention will be further described below in conjunction with specific embodiments.

[0084] In the present invention, the devices or equipment used are all conventional devices or equipment known in the art and can be purchased.

[0085] In the following examples and comparative examples, unless otherwise specified, various reagents used are commercially available chemically pure reagents.

[0086] Example 1

[0087] The gel for deep profile control with temperature and salt resistance comprises the following steps:

[0088] Add 0.3 g of melamine resin, 0.03 g of hydroquinone, 1.0 g of nano-silica dispersion, and 0.3 g of thiourea to 97.77 g of water, stir evenly, and finally slowly add 0.6 g of AM / AMPS / NVP terpolymer under stirring conditions. Stir at room temperature for 3 hours until the polymer is completely dissolved to obtain a gelling solution. Place the gelling solution in an ampoule bottle, sinter and seal it with an alcohol burner, and age it in an oven at 110 °C to obtain the gel.

[0089] Example 2

[0090] The gel for deep profile control with temperature and salt resistance comprises the following steps:

[0091] Add 0.4 g of melamine resin, 0.04 g of hydroquinone, 1.2 g of nano-silica dispersion, and 0.4 g of thiourea to 97.26 g of water, stir evenly, and finally slowly add 0.7 g of AM / AMPS / NVP terpolymer under stirring conditions. Stir at room temperature for 3 hours until the polymer is completely dissolved to obtain a gelling solution. Place the gelling solution in an ampoule bottle, sinter and seal it with an alcohol burner, and age it in an oven at 120 °C to obtain the gel.

[0092] Example 3

[0093] The gel for deep profile control and plugging resistant to temperature and salt is composed of the following steps:

[0094] Add 0.5 g of melamine resin, 0.05 g of hydroquinone, 1.5 g of nano-silica dispersion liquid, and 0.5 g of thiourea to 96.65 g of water, stir evenly, and finally slowly add 0.8 g of AM / AMPS / NVP terpolymer under stirring conditions. Stir at room temperature for 3 hours until the polymer is completely dissolved to obtain the gelling solution. Place the gelling solution in an ampoule bottle, sinter and seal it with an alcohol burner, and age it in an oven at 130 °C to obtain the gel.

[0095] Comparative Example 1

[0096] The gel for deep profile control and plugging resistant to temperature and salt is composed of the following steps:

[0097] Add 0.3 g of melamine resin, 1.0 g of nano-silica dispersion liquid, and 0.3 g of thiourea to 97.8 g of water, stir evenly, and finally slowly add 0.6 g of AM / AMPS / NVP terpolymer under stirring conditions. Stir at room temperature for 3 hours until the polymer is completely dissolved to obtain the gelling solution. Place the gelling solution in an ampoule bottle, sinter and seal it with an alcohol burner, and age it in an oven at 110 °C to obtain the gel.

[0098] Comparative Example 2

[0099] The gel for deep profile control and plugging resistant to temperature and salt is composed of the following steps:

[0100] Add 0.3 g of melamine resin, 0.03 g of hydroquinone, and 0.3 g of thiourea to 98.77 g of water, stir evenly, and finally slowly add 0.6 g of AM / AMPS / NVP terpolymer under stirring conditions. Stir at room temperature for 3 hours until the polymer is completely dissolved to obtain the gelling solution. Place the gelling solution in an ampoule bottle, sinter and seal it with an alcohol burner, and age it in an oven at 110 °C to obtain the gel.

[0101] Comparative Example 3

[0102] The gel for deep profile control and plugging resistant to temperature and salt is composed of the following steps:

[0103] Add 0.3 g of melamine resin, 0.03 g of hydroquinone, and 1.0 g of nano-silica dispersion liquid to 98.07 g of water, stir evenly, and finally slowly add 0.6 g of AM / AMPS / NVP terpolymer under stirring conditions. Stir at room temperature for 3 hours until the polymer is completely dissolved to obtain the gelling solution. Place the gelling solution in an ampoule bottle, sinter and seal it with an alcohol burner, and age it in an oven at 110 °C to obtain the gel.

[0104] Comparative Example 4

[0105] The gel for deep profile control and plugging resistant to temperature and salt consists of the following steps:

[0106] Add 0.6 g of melamine resin, 0.05 g of hydroquinone, 1.5 g of nano-silica dispersion liquid, and 0.5 g of thiourea to 96.55 g of water, stir evenly, and finally slowly add 0.8 g of AM / AMPS copolymer under stirring conditions. Stir at room temperature for 3 hours until the polymer is completely dissolved to obtain the gel-forming solution. Place the gel-forming solution in an ampoule bottle, sinter and seal it with an alcohol burner, and age it in an oven at 130 °C to obtain the gel.

[0107] Comparative Example 5

[0108] The gel for deep profile control and plugging resistant to temperature and salt consists of the following steps:

[0109] Add 0.6 g of water-soluble phenolic resin, 0.05 g of hydroquinone, 1.5 g of nano-silica dispersion liquid, and 0.5 g of thiourea to 96.55 g of water, stir evenly, and finally slowly add 0.8 g of AM / AMPS / NVP terpolymer under stirring conditions. Stir at room temperature for 3 hours until the polymer is completely dissolved to obtain the gel-forming solution. Place the gel-forming solution in an ampoule bottle, sinter and seal it with an alcohol burner, and age it in an oven at 130 °C to obtain the gel.

[0110] Test Example 1

[0111] Use the gels for deep profile control and plugging resistant to temperature and salt prepared in Examples 1 to 3 and Comparative Examples 1 to 4 to measure the gelation time of the gel, the storage modulus after aging for 5 days after gelation, and the dehydration rate after aging for 90 days.

[0112] (1) Pour 50 g of the gel-forming solution into a heat-resistant glass tube with a stopper and age it to form a gel in an oven. Take out the glass tube at regular intervals and invert it; it can be observed that the fluidity of the gel gradually weakens with the aging time. When the upper edge of the gel cannot touch the stopper of the glass tube after inverting the glass tube, it is regarded that the gel has formed, and the aging time at this time is recorded as the gelation time.

[0113] (2) Take out the gel after aging for 5 days and use an Anton Paar MCR 92 shear rheometer to measure the storage modulus of the gel at 1% strain and 1 Hz frequency.

[0114] (3) Take out the glass tube after aging for 90 days, weigh the mass of the water in the glass tube, and measure the dehydration rate of the gel:

[0115] Dehydration rate = mass of water / 50 g × 100%

[0116] The experimental results are shown in Table 1.

[0117] Table 1 Experimental results of gelation performance investigation

[0118]

[0119]

[0120] As can be seen from the experimental results in Table 1, in Examples 1 to 3, with the increase in the concentration of the polymer agent in the gel-forming solution and the increase in the aging temperature, the gelation time of the gel decreases, the storage modulus increases, and the dehydration rate is still less than 10%, indicating good gel stability. In Comparative Example 1, hydroquinone, the gelation-promoting crosslinking agent, was not added, and the gel stability deteriorated significantly at 110°C, with a dehydration rate higher than 20% after 90 days. In Comparative Example 2, nano-silica reinforcing agent was not added, resulting in a relatively low gelation strength of the gel, and gel breaking occurred after 90 days of aging. In Comparative Example 3, thiourea stabilizer was not added, leading to a decrease in the gelation strength and stability of the gel, and the dehydration rate reached more than 30% after 90 days of aging. The gel prepared with the AM / AMPS copolymer as the polymer in Comparative Example 4 broke down after 90 days at 130°C, and its long-term stability was significantly worse than that of Example 3. The gel prepared with water-soluble phenolic resin as the crosslinking agent in Comparative Example 5 had a gelation time of only 16 h at 130°C and broke down after 90 days. In Example 3, the AM / AMPS / NVP terpolymer was used as the polymer and melamine resin was used as the crosslinking agent, and hydroquinone gelation-promoting crosslinking agent, nano-silica reinforcing agent and thiourea stabilizer were added. At 130°C, not only a relatively long gelation time was ensured, but also the gelation strength was significantly improved, and the gel stability was significantly enhanced, meeting the requirements for deep profile control and plugging in high-temperature and high-salinity reservoirs.

[0121] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A gel for deep profile control and plugging resistant to temperature and salt, characterized in that, the gel comprises a main agent, a crosslinking agent, a crosslinking promoter, a reinforcing agent, a stabilizer and water, and the mass percentage composition is as follows: the main agent is 0.4% - 1.0%, and the main agent is acrylamide / 2-acrylamido-2-methylpropanesulfonic acid / N-vinylpyrrolidone (AM / AMPS / NVP) terpolymer; the crosslinking agent is 0.3% - 0.8%; the crosslinking promoter is 0.02% - 0.06%; the reinforcing agent is 1.0% - 2.0%; the stabilizer is 0.2% - 0.6%; the sum of the mass percentages of each component is 100%.

2. The gel for deep profile control and plugging resistant to temperature and salt according to claim 1, characterized in that, the relative molecular weight of the acrylamide / 2-acrylamido-2-methylpropanesulfonic acid / N-vinylpyrrolidone (AM / AMPS / NVP) terpolymer is 3 million - 8 million.

3. The gel for deep profile control and plugging resistant to temperature and salt according to claim 2, characterized in that, the relative molecular weight of the terpolymer is 5 million.

4. The gel for deep profile control and plugging resistant to temperature and salt according to claim 2, characterized in that, the hydrolysis degree of the terpolymer is 20% - 30%.

5. The gel for deep profile control and plugging resistant to temperature and salt according to claim 4, characterized in that, the hydrolysis degree of the terpolymer is 25 - 30%.

6. The gel for deep profile control and plugging resistant to temperature and salt according to claim 1, characterized in that, the crosslinking agent is melamine resin.

7. The gel for deep profile control and plugging resistant to temperature and salt according to claim 1, characterized in that, the crosslinking promoter is one of phenol, resorcinol and hydroquinone.

8. The gel for deep profile control and plugging resistant to temperature and salt according to claim 1, characterized in that, the crosslinking promoter is hydroquinone.

9. The gel for deep profile control and plugging resistant to temperature and salt according to claim 1, characterized in that, the reinforcing agent is nano-silica dispersion.

10. The gel for deep profile control and plugging resistant to temperature and salt according to claim 9, characterized in that, the effective content of the nano-silica dispersion is 30%, and the particle size is 10nm - 30nm.

11. The gel for deep profile control and plugging resistant to temperature and salt according to claim 10, characterized in that, the particle size is 10 - 20nm.

12. The gel for deep profile control and plugging resistant to temperature and salt according to claim 1, characterized in that, the stabilizer is one of sodium nitrite, sodium sulfite and thiourea.

13. The gel for deep profile control and plugging resistant to temperature and salt according to claim 1, characterized in that, the stabilizer is thiourea.

14. The gel for deep profile control and plugging resistant to temperature and salt according to claim 1, characterized in that, The water is formation water with a salinity of 5×10 5 ~10×10 5 mg / L.

15. The gel for deep profile control and plugging resistant to temperature and salt according to claim 1, characterized in that, the mass percentage composition is as follows: acrylamide / 2-acrylamido-2-methylpropanesulfonic acid / N-vinylpyrrolidone (AM / AMPS / NVP) terpolymer 0.6% - 0.8%; melamine resin 0.3% - 0.6%; hydroquinone 0.02% - 0.05%; nano-silica dispersion 1.0 - 1.5%; thiourea 0.3% - 0.5%; The balance is water; The sum of the mass percentages of each component is 100%.

16. The gel for deep profile control and plugging resistant to temperature and salt according to claim 15, characterized in that the mass percentage composition is as follows: AM / AMPS / NVP terpolymer 0.6%, melamine resin 0.3%, hydroquinone 0.03%, nano-silica dispersion 1.0%, thiourea 0.3%, and the balance is water.

17. The gel for deep profile control and plugging resistant to temperature and salt according to claim 15, characterized in that the mass percentage composition is as follows: AM / AMPS / NVP terpolymer 0.7%, melamine resin 0.4%, hydroquinone 0.04%, nano-silica dispersion 1.2%, thiourea 0.4%, and the balance is water.

18. The gel for deep profile control and plugging resistant to temperature and salt according to claim 15, characterized in that the mass percentage composition is as follows: AM / AMPS / NVP terpolymer 0.8%, melamine resin 0.5%, hydroquinone 0.05%, nano-silica dispersion 1.5%, thiourea 0.5%, and the balance is water.

19. The preparation method of the gel for deep profile control and plugging resistant to temperature and salt according to any one of claims 1-18, characterized in that the preparation method is as follows: adding a crosslinking agent, a crosslinking promoter, a reinforcing agent and a stabilizer to water in proportion, stirring evenly, and then slowly adding the main agent under stirring conditions, and stirring at room temperature for 3 hours until completely dissolved to obtain the gel-forming solution.

20. The application of the gel for deep profile control and plugging resistant to temperature and salt according to any one of claims 1-18 in oilfield exploitation.

21. The application of the gel for deep profile control and plugging resistant to temperature and salt according to any one of claims 1-18 as a water plugging agent.

Images