CN106916578A - A high temperature resistant weak gel profile control agent and its preparation method - Google Patents

Abstract

The invention discloses a high-temperature-resistant weak gel type profile control agent and a preparation method thereof, belonging to the field of chemical water shutoff profile control agents. The high-temperature resistant weak gel type profile control agent comprises: partially hydrolyzed polyacrylamide with the concentration of 0.8g/L-2.5g/L, modified phenolic resin with the concentration of 0.6g/L-2.0g/L, auxiliary agent with the concentration of 0.5g/L-2.0g/L and water. Adding phenol into a reaction kettle, heating to 45-55 ℃, adding an alkaline catalyst while stirring, preserving heat for 10-30min, dripping a formaldehyde solution, quickly heating to 70-90 ℃, preserving heat for 3-5h, finally adding urea, uniformly mixing, and preserving heat for 10-30min to obtain the modified phenolic resin. The mol ratio of the phenol to the formaldehyde in the formaldehyde solution is 1:2.7-3.3, and the dosage of the urea is 1-5% of the total mass of the phenol and the formaldehyde solution. Mixing aluminum chloride and oxalic acid, dissolving with water, adding ammonium chloride, reacting under stirring at pH of 6-8, and removing water to obtain the final product. The mol ratio of the aluminum chloride, the oxalic acid and the ammonium chloride is 1 (15-30) to (70-90). The high temperature resistant weak gel type profile control agent can resist the high temperature of 90-110 ℃ and has long effective period.

Description

A high temperature resistant weak gel profile control agent and its preparation method

technical field

The invention relates to the field of chemical water plugging profile control agents, in particular to a high temperature resistant weak gel profile control agent and a preparation method thereof.

Background technique

At present, most oil fields in my country use water injection to develop oil fields. In the later stage of development, due to the heterogeneity of the formation, 80% to 90% of the water injected into the oil layer is absorbed by the high-permeability formation with a small thickness, resulting in water injection. The profile is very uneven, reducing the recovery efficiency of the reservoir. In order to adjust the uniformity of the water injection profile, increase the sweep coefficient of the injected water, and play the role of the medium and low permeability formations, so as to improve the oil recovery rate, it is necessary to block the high permeability formations to a certain extent. The chemical agents used for the blockage called a profile control agent. When the profile control agent is a weak gel system, it not only has a certain strength, which can play a role in sealing the high permeability formation, but also has a certain fluidity, and can slowly move to the deep formation in the high permeability formation channel. It has good profile control effect. Therefore, it is very necessary to provide a profile control agent with a weak gel system.

The prior art provides a weak gel type profile control agent, by mixing the following substances in parts by mass: 0.1-0.3 parts of polyacrylamide, 0.05-0.2 parts of urotropine, 0.005-0.03 parts of resorcinol 0.05 to 0.2 parts of ammonium chloride, 0.01 to 0.05 parts of sodium bicarbonate, 0.05 to 0.15 parts of glacial acetic acid, and 100 parts of water. After mixing, adjust the pH of the solution to 5, bake at 60-90°C to obtain weak Gel type profile control agent.

The inventor finds that the prior art has at least the following technical problems:

The weak gel profile control agent provided by the prior art can only meet the profile control requirements when the formation temperature is 60-90°C. When the formation temperature is higher than 90°C, the weak gel profile control agent has poor high temperature resistance And the validity period is short, which cannot meet the profile control of water injection in high-temperature formations.

Contents of the invention

The technical problem to be solved by the present invention is to provide a high temperature-resistant and long-term weak gel profile control agent and its preparation method. The specific technical scheme is as follows:

On the one hand, the embodiment of the present invention provides a high temperature resistant weak gel profile control agent, comprising: partially hydrolyzed polyacrylamide, modified phenolic resin, auxiliary agent and water; the concentration of the partially hydrolyzed polyacrylamide is 0.8g /L-2.5g/L, the concentration of the modified phenolic resin is 0.6g/L-2.0g/L, and the concentration of the additive is 0.5g/L-2.0g/L.

Described modified phenolic resin is prepared by following method:

Add phenol into the reaction kettle, heat to 45-55°C, then add alkaline catalyst while stirring, keep warm for 10-30min, then drop formaldehyde solution, rapidly raise the temperature to 70-90°C, keep warm for 3-5h, and finally add urea, mixed uniformly and then kept warm for 10-30min to obtain the modified phenolic resin. The mass concentration of the formaldehyde solution is 25-35%, the molar ratio of the phenol to the formaldehyde in the formaldehyde solution is 1:2.7-3.3, and the urea consumption is 1% of the total mass of the phenol and the formaldehyde solution. -5%.

The auxiliary agent is prepared by the following method:

Aluminum chloride and oxalic acid are mixed and dissolved in water, then ammonium chloride is added, the pH of the reaction system is 6-8 and the reaction is carried out under stirring, and finally the auxiliary agent is obtained after dehydration. The molar ratio of the aluminum chloride, oxalic acid and ammonium chloride is 1:(15-30):(70-90).

On the other hand, the embodiment of the present invention also provides a method for preparing the high temperature resistant weak gel type profile control agent, including:

Step a, prepare modified phenolic resin

Add phenol into the reaction kettle, heat to 45-55°C, then add alkaline catalyst while stirring, keep warm for 10-30min, then drop formaldehyde solution, rapidly raise the temperature to 70-90°C, keep warm for 3-5h, and finally add urea, mixed uniformly and then kept warm for 10-30min to obtain the modified phenolic resin. The mass concentration of described formaldehyde solution is 25-35%, and the molar ratio of described phenol and formaldehyde in described formaldehyde solution is 1:2.7-3.3, and described urea is described phenol and described formaldehyde solution total mass 1-1. 5%.

Step b, preparation auxiliary agent

Aluminum chloride and oxalic acid are mixed and dissolved in water, then ammonium chloride is added, the pH of the reaction system is 6-8 and the reaction is carried out under stirring, and finally the auxiliary agent is obtained after dehydration. The molar ratio of the aluminum chloride, oxalic acid and ammonium chloride is 1:(15-30):(70-90).

Step c. Preparation of high temperature resistant weak gel type profile control agent

Prepare an aqueous solution of partially hydrolyzed polyacrylamide, then add the modified phenolic resin and the auxiliary agent to the aqueous solution of partially hydrolyzed polyacrylamide, mix well and put it in a constant temperature and humidity box, at 90-110°C Under constant temperature treatment, the high temperature resistant weak gel type profile control agent is obtained. In the high temperature resistant weak gel type profile control agent, the concentration of the partially hydrolyzed polyacrylamide is 0.8g/L-2.5g/L, and the concentration of the modified phenolic resin is 0.6g/L-2.0g/L L, the concentration of the auxiliary agent is 0.5g/L-2.0g/L.

Specifically, preferably, the basic catalyst is sodium hydroxide.

Specifically, preferably, the amount of the basic catalyst used is 2-10% of the total mass of the formaldehyde solution and the phenol.

Specifically, preferably, in the step a, the total time required for dripping the formaldehyde solution is 10-60min.

Specifically, as a preference, in the step b, the pH of the reaction system is adjusted to 6-8 with ammonia water.

Specifically, as a preference, in the step c, the constant temperature treatment time is 8-40h.

Specifically, as a preference, in the step c, the relative air humidity of the constant temperature and humidity chamber is 1-3%.

Specifically, as a preference, in the step c, preparing the aqueous solution of the partially hydrolyzed polyacrylamide includes: adding the partially hydrolyzed polyacrylamide into water, stirring and aging for 2-4 hours to obtain the partially hydrolyzed polyacrylamide aqueous solution.

The beneficial effects brought by the technical solution provided by the embodiments of the present invention are:

The high temperature resistant weak gel type profile control agent provided by the embodiment of the present invention uses partially hydrolyzed polyacrylamide as the main agent, through the cross-linking reaction of the modified phenolic resin and the main agent, and under the compounding action of the auxiliary agent, the formed The high-temperature-resistant weak gel profile control agent can withstand high temperatures of 90-110°C and has a long validity period. Among them, by adding urea in the preparation process of the modified phenolic resin, it can react with free formaldehyde, thereby reducing the free formaldehyde in the phenolic resin, and the obtained profile control agent is more environmentally friendly. At the same time, urea also acts as a stabilizer. Inhibit the decomposition of the weak gel system, make the weak gel system gel 30 days, under the high temperature condition of formation temperature of 90-110 ℃, its viscosity can still maintain at 70-80% of the original, to ensure its long validity period. The reaction speed between the partially hydrolyzed polyacrylamide and the modified phenolic resin is accelerated by the auxiliary agent, so that the preparation of the high temperature resistant weak gel profile control agent is quicker. It can be seen that the high-temperature-resistant weak gel profile control agent provided by the embodiment of the present invention can withstand high temperatures of 90-110°C, has a long validity period, and has a simple and quick preparation method, which is convenient for large-scale popularization and application.

detailed description

In order to make the purpose, technical solution and advantages of the present invention clearer, the implementation manners of the present invention will be further described in detail below.

In the first aspect, the embodiment of the present invention provides a high temperature resistant weak gel profile control agent, which includes: partially hydrolyzed polyacrylamide, modified phenolic resin, additives and water. In the profile control agent, the concentration of partially hydrolyzed polyacrylamide is 0.8g/L-2.5g/L (such as 0.8, 1.2, 1.5, 2.0, 2.2, 2.5g/L), and the concentration of modified phenolic resin is 0.6g /L-2.0g/L (such as 0.6, 1.0, 1.4, 1.6, 2.0g/L), the concentration of additives is 0.5g/L-2.0g/L (such as 0.5, 0.8, 1.2, 1.6, 2.0g/L L).

Specifically, the modified phenolic resin is prepared by the following method:

Add phenol into the reaction kettle, heat to 45-55°C, then add alkaline catalyst while stirring, keep warm for 10-30min, then drop formaldehyde solution, rapidly raise the temperature to 70-90°C, keep warm for 3-5h, and finally add urea, mixed evenly and kept warm for 10-30min to obtain modified phenolic resin. The mass concentration of the formaldehyde solution is 25-35%, the molar ratio of phenol to formaldehyde in the formaldehyde solution is 1:2.7-3.3, and the amount of urea is 1-5% of the total mass of the phenol and formaldehyde solution.

The auxiliary agent is prepared by the following method:

Aluminum chloride and oxalic acid are mixed and dissolved in water, then ammonium chloride is added, the pH of the reaction system is 6-8 and the reaction is carried out in a stirring state, and finally the water is removed to obtain the auxiliary agent. The molar ratio of aluminum chloride, oxalic acid and ammonium chloride is 1:(15-30):(70-90).

The high temperature resistant weak gel type profile control agent provided by the embodiment of the present invention uses partially hydrolyzed polyacrylamide as the main agent, realizes the crosslinking reaction with the main agent through modified phenolic resin, and under the compounding action of the auxiliary agent, the obtained The formed high temperature resistant weak gel profile control agent can withstand high temperature of 90-110°C and has a long validity period. Among them, by adding urea in the preparation process of the modified phenolic resin, it can react with free formaldehyde, thereby reducing the free formaldehyde in the phenolic resin, and the obtained profile control agent is more environmentally friendly. At the same time, urea also acts as a stabilizer. Inhibit the decomposition of the weak gel system, make the weak gel system gel 30 days, under the high temperature condition of formation temperature of 90-110 ℃, its viscosity can still maintain at 70-80% of the original, to ensure its long validity period. The reaction speed between the partially hydrolyzed polyacrylamide and the modified phenolic resin is accelerated by the auxiliary agent, so that the preparation of the high temperature resistant weak gel profile control agent is quicker. It can be seen that the high-temperature-resistant weak gel profile control agent provided by the embodiment of the present invention can withstand high temperatures of 90-110°C, has a long validity period, and has a simple and quick preparation method, which is convenient for large-scale popularization and application.

In the second aspect, the embodiment of the present invention also provides a method for preparing the high temperature resistant weak gel type profile control agent, comprising the following steps:

Step 101, preparing modified phenolic resin

Add phenol into the reaction kettle, heat to 45-55°C, such as 45°C, 48°C, 50°C, 53°C, 55°C, then add the basic catalyst while stirring, and keep warm for 10-30min, for example, keep warm for 10min, 15min , 20min, 25min, 30min, then drop formaldehyde solution, rapidly raise the temperature to 70-90°C, such as 70°C, 75°C, 80°C, 85°C, 90°C, keep warm for 3-5h, such as 3h, 4h, 5h, to get For the phenolic resin, add urea at the end, mix well and keep warm for 10-30min, such as 10min, 15min, 20min, 25min, 30min, to obtain the modified phenolic resin.

Wherein, the mass concentration of formaldehyde solution is 25-35%, preferably 30%, and the mol ratio of formaldehyde in phenol and formaldehyde solution is 1:2.7-3.3, such as 1:2.7, 1:2.9, 1:3.1, 1:3.3 , urea is 1-5% of the total mass of phenol and formaldehyde solution, such as 1%, 2%, 3%, 4%, 5%. In step 101, urea is used to modify the phenolic resin. After the urea reacts with free formaldehyde, the free formaldehyde in the phenolic resin is reduced to obtain a more environmentally friendly profile control agent. At the same time, urea also acts as a stabilizer to inhibit the weak gel The decomposition of the system improves the durability of the weak gel profile control agent, so that after 30 days of gelation, the viscosity can still be maintained at the original 70-80 under the high temperature condition of the formation temperature of 90-110°C %, thus having a longer validity period.

In the high temperature resistant weak gel type profile control agent provided in the embodiment of the present invention, the modified phenolic resin is used as a crosslinking agent, which can act as a bridge between linear molecules so that multiple linear molecules are bonded and crosslinked Form a network structure, promote or regulate the formation of covalent bonds or ionic bonds between polymer molecular chains, and transform monomers, linear polymers or prepolymers in solution into three-dimensional network structures, that is, form weak gel systems , so as to play a sealing role in the high permeability formation. At the same time, the weak gel system has a certain fluidity, and can slowly move to the deep part of the formation in the channel of the high-permeability formation, achieving the effect of control and flooding. Therefore, the high temperature resistant weak gel profile control agent provided by the embodiment of the present invention has better profile control effect.

Specifically, the basic catalyst used in step 101 is sodium hydroxide, which can promote the reaction of phenol and formaldehyde and increase the reaction rate. The amount of basic catalyst is 2-10% of the total mass of formaldehyde solution and phenol, such as 2%, 5%, 8%, 10%.

Step 102, preparing auxiliary agent

Aluminum chloride and oxalic acid are mixed and dissolved in water, then ammonium chloride is added, the pH of the reaction system is 6-8 and the reaction is carried out in a stirring state, and finally the water is removed to obtain the auxiliary agent. Wherein, the molar ratio of aluminum chloride, oxalic acid and ammonium chloride is 1:(15-30):(70-90), such as 1:15:70, 1:23:80, 1:30:90.

Through the above additives, the rate of the crosslinking reaction between the modified phenolic resin and the partially hydrolyzed polyacrylamide can be accelerated, the condensation ratio of the hydroxyl group and the partially hydrolyzed polyacrylamide can be increased, and the reaction can be fully carried out.

Specifically, in step 102, the total time required for dropping the formaldehyde solution is 10-60min, that is, the formaldehyde solution should be added dropwise within 10-60min (such as 10min, 20min, 30min, 40min, 50min, 60min) to ensure that the phenol The reaction with formaldehyde goes to completion.

Specifically, in step 102, when adjusting the pH of the reaction system, ammonia water can be used to adjust it until the pH of the reaction system is in the range of 6-8, ensuring that the auxiliary agent is neutral can improve the stability of the auxiliary agent and avoid The acidity and alkalinity of additives affect the cross-linking reaction of modified phenolic resin and partially hydrolyzed polyacrylamide.

Step 103, preparing high temperature resistant weak gel type profile control agent

Prepare an aqueous solution of partially hydrolyzed polyacrylamide, then add modified phenolic resin and additives to the aqueous solution of partially hydrolyzed polyacrylamide, mix them uniformly, put them in a constant temperature and humidity box, and perform constant temperature treatment at 90-110°C to obtain High temperature resistant weak gel profile control agent. In the high temperature resistant weak gel type profile control agent, the concentration of partially hydrolyzed polyacrylamide is 0.8g/L-2.5g/L (such as 0.8, 1.2, 1.5, 2.0, 2.2, 2.5g/L), modified phenolic resin The concentration of additives is 0.6g/L-2.0g/L (such as 0.6, 1.0, 1.4, 1.6, 2.0g/L), and the concentration of additives is 0.5g/L-2.0g/L (such as 0.5, 0.8, 1.2, 1.6, 2.0g/L). The concentration of the modified phenolic resin is 0.6g/L-2.0g/L, and the concentration of the additive is 0.5g/L-2.0g/L.

Specifically, in step 103, the constant temperature treatment time is 8-40h, such as 8h, 10h, 15h, 20h, 25h, 30h, 35h, 40h, etc., and the relative air humidity of the constant temperature and humidity box is 1-3%, such as 1%. , 2%, 3%, to maintain the reaction rate. The product forms a weak gel and has a certain humidity, suitable for existence in the formation environment of 90-110°C.

Specifically, in step 103, preparing the aqueous solution of partially hydrolyzed polyacrylamide includes: slowly adding partially hydrolyzed polyacrylamide into water, and stirring properly to avoid solidification, and the stirring should not be too violent, so as not to cause polymer degradation and affect the use effect , It is advisable to stir and mature for 2-4h, such as 2h, 2.5h, 3h, 3.5h, 4h. An aqueous solution of partially hydrolyzed polyacrylamide is obtained. Use a freshly prepared aqueous solution of partially hydrolyzed polyacrylamide to avoid its performance gradually decreasing with the water quality and the extension of time.

The following will be further elaborated by specific examples:

Example 1

In this example, the modified phenolic resin and additives used in the profile control agent were firstly prepared, as follows:

1), preparation of modified phenolic resin

Add 18.0 g of phenol into the reactor, heat to 50° C., and then add 3.6 g of NaOH with a mass concentration of 10% as a catalyst while stirring. After 10 minutes of heat preservation, 18 g of formaldehyde solution with a mass concentration of 30% was added dropwise within 35 minutes, the temperature was rapidly raised to 70°C, and the temperature was kept for 3 hours. Finally, 4 g of urea was added, mixed evenly, kept warm for 10 min, and cooled to room temperature to obtain a modified phenolic resin.

2), Preparation Auxiliary

Mix 1.34g of aluminum chloride and 18g of oxalic acid and dissolve in water, then add 42.76g of ammonium chloride, stir evenly, adjust the pH of the reaction system to about 7 with ammonia water, remove the water after the reaction, and obtain the auxiliary agent.

3) Prepare an aqueous solution of fresh partially hydrolyzed polyacrylamide

Example 2

In this example, the modified phenolic resin, additives, and partially hydrolyzed polyacrylamide aqueous solution provided in Example 1 were mixed evenly, and placed in a constant temperature and humidity chamber, and kept at 90°C and a relative humidity of 1%. treatment to obtain a high temperature resistant weak gel profile control agent. Wherein, the content of each component in the high temperature resistant weak gel type profile control agent is as follows:

The concentration of partially hydrolyzed polyacrylamide is 0.8g/L, the concentration of modified phenolic resin is 0.6g/L, and the concentration of additives is 0.5g/L.

The initial viscosity of the prepared high-temperature-resistant weak gel type profile control agent was measured, which was 1223mPa·s, and then it was placed in a jar with a stopper, and the gelation situation was observed. After being placed in the jar for 30 days, Then the viscosity of the profile control agent was measured, and it was 966mPa·s. It can be seen that the high temperature resistant weak gel profile control agent prepared in this example has a good effect.

Example 3

In this example, the modified phenolic resin, additives, and partially hydrolyzed polyacrylamide aqueous solution provided in Example 1 were mixed evenly, and placed in a constant temperature and humidity chamber, and subjected to constant temperature treatment at 110°C and a relative humidity of 2%. , to obtain high temperature resistant weak gel profile control agent. Wherein, the content of each component in the high temperature resistant weak gel type profile control agent is as follows:

The concentration of partially hydrolyzed polyacrylamide is 2.5g/L, the concentration of modified phenolic resin is 2.0g/L, and the concentration of additives is 2.0g/L.

The initial viscosity of the prepared high-temperature-resistant weak gel type profile control agent was measured, and it was 1857mPa·s, and then it was placed in a jar with a stopper, and the gelation situation was observed. After being placed in the jar for 30 days, Then the viscosity of the profile control agent was measured, and it was 1318mPa·s. It can be seen that the high temperature resistant weak gel profile control agent prepared in this example has a good effect.

Example 4

In this example, the modified phenolic resin, additives, and partially hydrolyzed polyacrylamide aqueous solution provided in Example 1 were mixed evenly, and placed in a constant temperature and humidity box, and subjected to constant temperature treatment at 100°C and a relative humidity of 3%. , to obtain high temperature resistant weak gel profile control agent. Wherein, the content of each component in the high temperature resistant weak gel type profile control agent is as follows:

The concentration of partially hydrolyzed polyacrylamide is 1.7g/L, the concentration of modified phenolic resin is 1.3g/L, and the concentration of additives is 1.2g/L.

The initial viscosity of the prepared high-temperature-resistant weak gel type profile control agent was measured, and it was 1682mPa·s, and then it was placed in a jar with a stopper, and the gelation situation was observed. After being placed in the jar for 30 days, Then the viscosity of the profile control agent was measured, and it was 1228mPa·s. It can be seen that the high temperature resistant weak gel profile control agent prepared in this example has a good effect.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in this invention. within the scope of protection of the invention.

Claims (9)

1. a kind of high temperature resistant Weak Gels type profile control agent, including：Partially hydrolyzed polyacrylamide (PHPA), phenol-formaldehyde resin modified, auxiliary agent and water；The partially hydrolyzed polyacrylamide (PHPA) concentration is 0.8g/L-2.5g/L, and the modified phenolic resin lipid concentration is 0.6g/L-2.0g/L, and the assistant concentration is 0.5g/L-2.0g/L；

The phenol-formaldehyde resin modified is prepared via a method which to obtain：

To phenol is added in reactor, 45-55 DEG C is heated to, base catalyst is then added while stirring, after insulation 10-30min, formalin is instilled again, is rapidly heated to 70-90 DEG C, be incubated 3-5h, urea is eventually adding, 10-30min is incubated after being well mixed, obtain the phenol-formaldehyde resin modified；

The mass concentration of the formalin is 25-35%, and the phenol is 1 with the mol ratio of formaldehyde in the formalin:2.7-3.3, the amount of urea is the 1-5% of the phenol and the formalin gross mass；

The auxiliary agent is prepared via a method which to obtain：

Water dissolves are used after aluminium chloride is mixed with oxalic acid, ammonium chloride is subsequently adding, is reacted in the case where reaction system pH is 6-8 and stirring, the auxiliary agent is obtained after finally sloughing moisture；

The mol ratio of the aluminium chloride, oxalic acid and ammonium chloride is 1:(15-30):(70-90).

2. the preparation method of the high temperature resistant Weak Gels type profile control agent described in claim 1, including：

Step a, prepare phenol-formaldehyde resin modified

To phenol is added in reactor, 45-55 DEG C is heated to, base catalyst is then added while stirring, after insulation 10-30min, formalin is instilled again, is rapidly heated to 70-90 DEG C, be incubated 3-5h, urea is eventually adding, 10-30min is incubated after being well mixed, obtain the phenol-formaldehyde resin modified；

The mass concentration of the formalin is 25-35%, and the phenol is 1 with the mol ratio of formaldehyde in the formalin:2.7-3.3, the urea is the 1-5% of the phenol and the formalin gross mass；

Step b, prepare auxiliary agent

Water dissolves are used after aluminium chloride is mixed with oxalic acid, ammonium chloride is subsequently adding, is reacted in the case where reaction system pH is 6-8 and stirring, the auxiliary agent is obtained after finally sloughing moisture；

The mol ratio of the aluminium chloride, oxalic acid and ammonium chloride is 1:(15-30):(70-90)；

Step c, preparation high temperature resistant Weak Gels type profile control agent

Prepare the aqueous solution of partially hydrolyzed polyacrylamide (PHPA), then to adding the phenol-formaldehyde resin modified and the auxiliary agent in the aqueous solution of the partially hydrolyzed polyacrylamide (PHPA), it is well mixed and is put into climatic chamber, constant temperature treatment is carried out at 90-110 DEG C, the high temperature resistant Weak Gels type profile control agent is obtained；

In the high temperature resistant Weak Gels type profile control agent, the concentration of the partially hydrolyzed polyacrylamide (PHPA) is 0.8g/L-2.5g/L, and the concentration of the phenol-formaldehyde resin modified is 0.6g/L-2.0g/L, and the concentration of the auxiliary agent is 0.5g/L-2.0g/L.

3. preparation method according to claim 2, it is characterised in that the base catalyst is NaOH.

4. preparation method according to claim 2, it is characterised in that the consumption of the base catalyst is the 2-10% of the formalin and the phenol gross mass.

5. preparation method according to claim 2, it is characterised in that in the step a, the total time that instilling the formalin needs is 10-60min.

6. preparation method according to claim 2, it is characterised in that in the step b, the pH that the reaction system is adjusted with ammoniacal liquor is 6-8.

7. preparation method according to claim 2, it is characterised in that in the step c, the constant temperature process time is 8-40h.

8. preparation method according to claim 2, it is characterised in that in the step c, the relative air humidity of the climatic chamber is 1-3%.

9. preparation method according to claim 2, it is characterised in that in the step c, the aqueous solution for preparing the partially hydrolyzed polyacrylamide (PHPA) includes：The partially hydrolyzed polyacrylamide (PHPA) is added to the water, stirring curing 2-4h obtains the aqueous solution of the partially hydrolyzed polyacrylamide (PHPA).