A scale inhibitor for well control fluid, its preparation method and its application

Abstract

This invention provides a method for preparing a scale inhibitor for well control fluid. The preparation method includes the following steps: S1, maleic anhydride, sodium hypophosphite, and deionized water are mixed evenly and reacted at 60-70℃ for 1-1.5 hours, then cooled to room temperature; S2, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride are added sequentially to the cooled solution obtained in step S1. After complete dissolution, a reaction system is formed, and the pH of the reaction system is adjusted to 6-8 with NaOH; S3, the reaction system is placed in a 60-75℃ water bath, ammonium persulfate is added as an initiator, and the reaction is carried out at a constant temperature for 6-7 hours, then cooled to room temperature to obtain the scale inhibitor for well control fluid. The scale inhibitor for well control fluid obtained by the preparation method provided by this invention has the advantages of being environmentally friendly, non-corrosive, and not causing damage to the environment. Furthermore, it has a good scale inhibition effect on CaCO3, with a scale inhibition rate of over 91%, and can be used as a scale inhibitor for well control fluids without solid phase brine.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of the preparation method of scale inhibitors, and particularly relates to a well killing fluid scale inhibitor, a preparation method and application thereof. BACKGROUND

[0002] In the process of oilfield exploitation, when there is a problem in the wellbore, well repair operation is needed. In the well repair operation, in order to ensure the safety of well repair, a well killing fluid is usually injected into the wellbore to balance the formation pressure, so as to ensure the smooth operation of well repair construction. The use of the well killing fluid can balance the formation pressure and protect the oil and gas layer.

[0003] The existing related well killing fluid is mainly divided into high-density solid-phase well killing fluid and solid-phase-free well killing fluid. The high-density solid-phase well killing fluid mainly improves the system density by adding iron ore powder, barite powder and the like. The density of the formed well killing fluid system can reach 2.6 g / cm 3 , but the solid phase is easy to produce sedimentation in the formation and cause damage to the formation. The solid-phase-free brine system mainly relies on calcium bromide, zinc bromide, formate and zinc chloride to weight the well killing fluid, so as to form a high-density solid-phase-free brine well killing fluid, thus avoiding the problems of sedimentation of weighting agents and excessive solid content.

[0004] In the use of the solid-phase-free brine well killing fluid, although the formate system has excellent performance, the use cost is high, which increases the construction cost of oilfield development operation. The use of the brine system can reduce the use cost of the well killing fluid while ensuring the construction effect of the well killing fluid. The brine system can improve the density of the well killing fluid by adding inorganic salts, and can make the density of the well killing fluid reach the construction requirement according to the on-site water injection construction conditions. The brine system has the advantages of convenient construction and low use cost. However, the brine system contains a large amount of Ca 2+ When HCO 3- and / or CO3 2- ions exist in the formation, scaling problems are easy to occur in the wellbore and the formation under the action of high temperature, which causes damage to the formation and thus leads to production reduction. SUMMARY

[0005] In view of the above problems in the prior art, the present application provides a well killing fluid scale inhibitor, a preparation method and application thereof. The scale inhibitor is used in the brine system well killing fluid for water injection well repair operation, has good scale inhibition effect on calcium carbonate scale of the brine system well killing fluid, and has low construction cost, so that the construction effect of the brine system well killing fluid added with the scale inhibitor is comparable to that of the formate system well killing fluid.

[0006] The specific application content is as follows:

[0007] In a first aspect, the present application provides a preparation method of a well killing fluid scale inhibitor, which comprises the following preparation steps:

[0008] S1. Mix maleic anhydride, sodium hypophosphite, and deionized water thoroughly, and react at 60-70℃ for 1-1.5 hours, then cool to room temperature.

[0009] S2. Add acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, allyl polyethylene glycol and octadecyl dimethyl allyl ammonium chloride sequentially to the cooled solution obtained in step S1. After complete dissolution, a reaction system is formed. Adjust the pH of the reaction system to 6-8 with NaOH.

[0010] S3. Place the reaction system in a water bath at 60-75℃, add the initiator ammonium persulfate, react at a constant temperature for 6-7 hours, and then cool to room temperature to obtain the scale inhibitor for the well control fluid.

[0011] Optionally, the molar ratio of maleic anhydride, sodium hypophosphite, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, allyl polyethylene glycol and octadecyl dimethyl allyl ammonium chloride is (10-15):(10-15):(5-10):(8-15):(1-2):(0.05-0.1).

[0012] Optionally, the molar ratio of maleic anhydride, sodium hypophosphite, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride is 12:12:10:15:1:0.1.

[0013] Optionally, the total mass of the maleic anhydride, the sodium hypophosphite, the acrylic acid, the 2-acrylamide-2-methylpropanesulfonic acid, the allyl polyethylene glycol, and the octadecyldimethylallyl ammonium chloride accounts for 35-45% of the total mass of the reaction system.

[0014] Optionally, the total mass of the maleic anhydride, the sodium hypophosphite, the acrylic acid, the 2-acrylamido-2-methylpropanesulfonic acid, the allyl polyethylene glycol, and the octadecyldimethylallyl ammonium chloride accounts for 40% of the total mass of the reaction system.

[0015] Optionally, the NaOH is in the form of small solid particles.

[0016] Optionally, the initiator ammonium persulfate accounts for 0.8%-1.2% of the total mass of the reaction system.

[0017] Optionally, the initiator ammonium persulfate accounts for 1.0% of the total mass of the reaction system.

[0018] In a second aspect, the present invention provides a scale inhibitor for well-killing fluid obtained by the preparation method described in the first aspect above.

[0019] Thirdly, the present invention provides an application of the scale inhibitor obtained by the preparation method described in the first aspect as a scale inhibitor for a solid-free brine-free well control fluid.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] This invention provides a method for preparing a scale inhibitor for well control fluid, specifically comprising: S1, mixing maleic anhydride, sodium hypophosphite, and deionized water evenly, reacting at 60-70℃ for 1-1.5h, and then cooling to room temperature; S2, adding acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride sequentially to the cooled solution obtained in step S1, and forming a reaction system after complete dissolution, adjusting the pH of the reaction system to 6-8 with NaOH; S3, placing the reaction system in a 60-75℃ water bath, adding ammonium persulfate as an initiator, reacting at a constant temperature for 6-7h, and then cooling to room temperature to obtain the scale inhibitor for well control fluid. This invention first reacts maleic anhydride monomer with sodium hypophosphite monomer to generate a polymer intermediate. Then, four monomers—acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethylallyl ammonium chloride—are added to the obtained polymer intermediate. After adjusting the pH, cross-linking polymerization occurs between the monomers under the action of ammonium persulfate initiator and at a suitable temperature, generating the aforementioned kill fluid scale inhibitor. This kill fluid scale inhibitor has the advantages of being environmentally friendly, non-corrosive, and not causing damage to the environment. Furthermore, it has a good scale inhibition effect on CaCO3, with an inhibition rate of over 91%, and can be used as a scale inhibitor for kill fluids in solid-free brine systems. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A flowchart illustrating the preparation method of the scale inhibitor for well control fluid provided in an embodiment of the present invention is shown. Detailed Implementation

[0024] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0025] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0026] In a first aspect, the present invention provides a method for preparing a scale inhibitor for well control fluid. Figure 1 A flowchart illustrating the preparation method of the scale inhibitor for well-killing fluid provided in this embodiment of the invention is shown, as follows: Figure 1 As shown, the preparation method includes the following preparation steps:

[0027] S1. Mix maleic anhydride, sodium hypophosphite, and deionized water thoroughly, and react at 60-70℃ for 1-1.5 hours, then cool to room temperature.

[0028] In this step, the mixture of maleic anhydride and sodium hypophosphite is subjected to the first synthesis reaction in a water bath at 60-70°C, generating a polymer intermediate. The specific structural formula of this polymer intermediate is shown in Formula I below:

[0029]

[0030] S2. Add acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, allyl polyethylene glycol and octadecyl dimethyl allyl ammonium chloride sequentially to the cooled solution obtained in step S1. After complete dissolution, a reaction system is formed. Adjust the pH of the reaction system to 6-8 with NaOH.

[0031] S3. Place the reaction system in a water bath at 60-75℃, add the initiator ammonium persulfate, react at a constant temperature for 6-7 hours, and then cool to room temperature to obtain the scale inhibitor for the well control fluid.

[0032] In specific implementations of steps S2 and S3, the remaining four monomers—acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride—as well as an initiator are further added to the mixed system containing the polymer intermediate. NaOH is used to adjust the pH of the mixed system, so that the polymer intermediate and the above four monomers undergo a second-step synthesis reaction, cross-linking and polymerizing to form the scale inhibitor for well control fluid described in this invention.

[0033] In specific implementation, during the second-step synthesis reaction, the selected pH value was experimentally verified and discussed. It was found that adjusting the pH of the mixed system with NaOH between 6 and 8 was most suitable. Too low a pH (below 6) or too high a pH (above 8) was detrimental to the cross-linking polymerization between monomers and polymer intermediates. When the pH was below 6, the role of the carboxyl and phosphate groups carried by the monomers in the cross-linking polymerization was inhibited. When the pH was above 8, the alkaline environment caused some monomers involved in the cross-linking polymerization to decompose and some products to be released. Verification by the embodiments of this invention revealed that the optimal pH value should be controlled at 7.

[0034] Formula II below gives the overall chemical reaction formula of the scale inhibitor for well control fluid formed by the polymerization of maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, allyl polyethylene glycol and octadecyl dimethyl allyl ammonium chloride.

[0035]

[0036] In some embodiments, the molar ratio of the maleic anhydride, the sodium hypophosphite, the acrylic acid, the 2-acrylamido-2-methylpropanesulfonic acid, the allyl polyethylene glycol, and the octadecyl dimethyl allyl ammonium chloride participating in the reaction of Formula II above can be (10-15):(10-15):(5-10):(8-15):(1-2):(0.05-0.1);

[0037] As a reference example, the molar ratio of the maleic anhydride, the sodium hypophosphite, the acrylic acid, the 2-acrylamido-2-methylpropanesulfonic acid, the allyl polyethylene glycol, and the octadecyl dimethyl allyl ammonium chloride participating in the reaction of Formula II above can be 15:15:5:8:2:0.05.

[0038] As a reference example, the molar ratio of maleic anhydride, sodium hypophosphite, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride participating in the above reaction formula II can also be 15:15:10:15:1:0.1.

[0039] As a reference example, the molar ratio of maleic anhydride, sodium hypophosphite, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride participating in the above reaction formula II can also be 12:12:5:10:1.5:0.08.

[0040] As a reference example, the molar ratio of maleic anhydride, sodium hypophosphite, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride participating in the above reaction formula II can also be 12:12:10:15:1:0.1.

[0041] As a reference example, the molar ratio of maleic anhydride, sodium hypophosphite, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride participating in the above reaction formula II can also be 15:15:10:15:1:0.1.

[0042] The preferred molar ratio of the maleic anhydride, sodium hypophosphite, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride provided in this embodiment of the invention is 12:12:10:15:1:0.1.

[0043] In some embodiments, the total mass of the maleic anhydride, sodium hypophosphite, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyldimethylallyl ammonium chloride participating in the reaction of Formula II above accounts for 35-45% of the total mass of the reaction system; preferably, the total mass of the maleic anhydride, sodium hypophosphite, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyldimethylallyl ammonium chloride accounts for 40% of the total mass of the reaction system.

[0044] In some implementations, the NaOH used to adjust the pH can be in the form of small solid particles.

[0045] In some embodiments, the initiator ammonium persulfate accounts for 0.8%-1.2% of the total mass of the reaction system; preferably, the initiator ammonium persulfate accounts for 1.0% of the total mass of the reaction system.

[0046] This invention provides a method for preparing a scale inhibitor for well control fluid. First, maleic anhydride monomer reacts with sodium hypophosphite monomer to generate a polymer intermediate. Then, four monomers—acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride—are added to the obtained polymer intermediate. After adjusting the pH, cross-linking polymerization occurs between the monomers under the action of ammonium persulfate initiator and at a suitable temperature to generate the scale inhibitor for well control fluid.

[0047] In a second aspect, the present invention provides a scale inhibitor for well-killing fluid obtained by the preparation method described in the first aspect above.

[0048] The scale inhibitor for kill fluids obtained by the preparation method described in the first aspect of this invention has the advantages of being environmentally friendly, non-corrosive, and not causing damage to the environment. Furthermore, it exhibits good scale inhibition effect on CaCO3, with an inhibition rate of over 91%, and can be used as a scale inhibitor for kill fluids in solid-free brine systems.

[0049] Thirdly, the present invention provides an application of the scale inhibitor obtained by the preparation method described in the first aspect as a scale inhibitor for a solid-free brine-free well control fluid.

[0050] The scale inhibitor for kill fluid obtained by the preparation method described in the first aspect of the present invention can be used as a scale inhibitor for kill fluid without solid phase brine, and its application effect is excellent, with a scale inhibition rate of over 91%.

[0051] To enable those skilled in the art to more clearly understand the present invention, the following embodiments are provided to illustrate in detail the scale inhibitor for well control fluid, its preparation method, and its application.

[0052] Example 1

[0053] Step 1: Mix maleic anhydride, sodium hypophosphite, and deionized water thoroughly, place in a 65°C water bath, react for 1 hour, and then cool to room temperature.

[0054] Step 2: Continue to add four monomers to the reaction system in sequence: acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride. The molar ratio of maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride (DMAAC-18) monomers is 15:15:5:8:2:0.05.

[0055] Step 3: Continue adding ammonium persulfate as the initiator to the reaction system. Adjust the pH of the reaction system to 6 using NaOH as solid particles, and place the reaction system in a 65℃ water bath for 6.5 hours. The amount of ammonium persulfate added is 1.2% of the total mass of the reaction system; the combined mass of the six monomers—maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500)-dimethylallyl ammonium chloride (DMAAC-18)—is 35% of the total mass of the reaction system.

[0056] Example 2

[0057] Step 1: Mix maleic anhydride, sodium hypophosphite, and deionized water thoroughly, place in a 65°C water bath, react for 1 hour, and then cool to room temperature.

[0058] Step 2: Continue to add four monomers to the reaction system in sequence: acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride. The molar ratio of maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500) dimethyl allyl ammonium chloride (DMAAC-18) monomers is 15:15:10:15:1:0.1.

[0059] Step 3: Continue adding ammonium persulfate as the initiator to the reaction system. Adjust the pH of the reaction system to 7 using NaOH as solid particles, and place the reaction system in a 65℃ water bath for 6.5 hours. The amount of ammonium persulfate added is 1% of the total mass of the reaction system; the combined mass of the six monomers—maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500)-dimethylallyl ammonium chloride (DMAAC-18)—is 40% of the total mass of the reaction system.

[0060] Example 3

[0061] Step 1: Mix maleic anhydride, sodium hypophosphite, and deionized water thoroughly, place in a 70°C water bath, react for 1 hour, and then cool to room temperature.

[0062] Step 2: Continue to add four monomers to the reaction system in sequence: acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride. The molar ratio of maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500) dimethyl allyl ammonium chloride (DMAAC-18) monomers is 15:15:8:12:2:0.1.

[0063] Step 3: Continue adding ammonium persulfate as the initiator to the reaction system. Adjust the pH of the reaction system to 7 using NaOH as solid particles, and place the reaction system in a 70℃ water bath for 6.5 hours. The amount of ammonium persulfate added is 1% of the total mass of the reaction system; the combined mass of the six monomers—maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500)-dimethylallyl ammonium chloride (DMAAC-18)—is 40% of the total mass of the reaction system.

[0064] Example 4

[0065] Step 1: Mix maleic anhydride, sodium hypophosphite, and deionized water thoroughly, place in a 70°C water bath, react for 1 hour, and then cool to room temperature.

[0066] Step 2: Continue to add four monomers to the reaction system in sequence: acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride. The molar ratio of maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500) dimethyl allyl ammonium chloride (DMAAC-18) monomers is 12:12:5:10:1.5:0.08.

[0067] Step 3: Continue adding ammonium persulfate as the initiator to the reaction system. Adjust the pH of the reaction system to 7 using NaOH as solid particles, and place the reaction system in a 70℃ water bath for 6.5 hours. The amount of ammonium persulfate added is 1.2% of the total mass of the reaction system; the combined mass of the six monomers—maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500)-dimethylallyl ammonium chloride (DMAAC-18)—is 40% of the total mass of the reaction system.

[0068] Example 5

[0069] Step 1: Mix maleic anhydride, sodium hypophosphite, and deionized water thoroughly, place in a 65°C water bath, react for 1 hour, and then cool to room temperature.

[0070] Step 2: Continue to add four monomers to the reaction system in sequence: acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride. The molar ratio of maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500) dimethyl allyl ammonium chloride (DMAAC-18) monomers is 12:12:10:15:1:0.1.

[0071] Step 3: Continue adding ammonium persulfate as the initiator to the reaction system. Adjust the pH of the reaction system to 7 using NaOH as solid particles, and place the reaction system in a 70℃ water bath for 6.5 hours. The amount of ammonium persulfate added is 1.2% of the total mass of the reaction system; the combined mass of the six monomers—maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500)-dimethylallyl ammonium chloride (DMAAC-18)—is 40% of the total mass of the reaction system.

[0072] Example 6

[0073] Step 1: Mix maleic anhydride, sodium hypophosphite, and deionized water thoroughly, place in a 65°C water bath, react for 1 hour, and then cool to room temperature.

[0074] Step 2: Continue to add four monomers to the reaction system in sequence: acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride. The molar ratio of maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500) dimethyl allyl ammonium chloride (DMAAC-18) monomers is 15:15:10:15:1:0.1.

[0075] Step 3: Continue adding ammonium persulfate as the initiator to the reaction system. Adjust the pH of the reaction system to 8 using NaOH as solid particles, and place the reaction system in a 70℃ water bath for 6.5 hours. The amount of ammonium persulfate added is 1.0% of the total mass of the reaction system; the combined mass of the six monomers—maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500)-dimethylallyl ammonium chloride (DMAAC-18)—is 35% of the total mass of the reaction system.

[0076] Comparative Example 1

[0077] Step 1: Mix maleic anhydride, sodium hypophosphite, and deionized water thoroughly, place in a 65°C water bath, react for 1 hour, and then cool to room temperature.

[0078] Step 2: Continue to add four monomers to the reaction system in sequence: acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride. The molar ratio of maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500) dimethyl allyl ammonium chloride (DMAAC-18) monomers is 12:12:10:15:1:0.1.

[0079] Step 3: Continue adding ammonium persulfate as the initiator to the reaction system. Adjust the pH of the reaction system to 5 using NaOH as solid particles, and place the reaction system in a 70℃ water bath for 6.5 hours. The amount of ammonium persulfate added is 1.2% of the total mass of the reaction system; the combined mass of the six monomers—maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500)-dimethylallyl ammonium chloride (DMAAC-18)—is 40% of the total mass of the reaction system.

[0080] Comparative Example 2

[0081] Step 1: Mix maleic anhydride, sodium hypophosphite, and deionized water thoroughly, place in a 65°C water bath, react for 1 hour, and then cool to room temperature.

[0082] Step 2: Continue to add four monomers to the reaction system in sequence: acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride. The molar ratio of maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500) dimethyl allyl ammonium chloride (DMAAC-18) monomers is 12:12:10:15:1:0.1.

[0083] Step 3: Continue adding ammonium persulfate as the initiator to the reaction system. Adjust the pH of the reaction system to 4 using NaOH as solid particles, and place the reaction system in a 70℃ water bath for 6.5 hours. The amount of ammonium persulfate added is 1.2% of the total mass of the reaction system; the combined mass of the six monomers—maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500)-dimethylallyl ammonium chloride (DMAAC-18)—is 40% of the total mass of the reaction system.

[0084] Comparative Example 3

[0085] Step 1: Mix maleic anhydride, sodium hypophosphite, and deionized water thoroughly, place in a 65°C water bath, react for 1 hour, and then cool to room temperature.

[0086] Step 2: Continue to add four monomers to the reaction system in sequence: acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride. The molar ratio of maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500) dimethyl allyl ammonium chloride (DMAAC-18) monomers is 12:12:10:15:1:0.1.

[0087] Step 3: Continue adding ammonium persulfate as the initiator to the reaction system. Adjust the pH of the reaction system to 3 using NaOH as solid particles, and place the reaction system in a 70℃ water bath for 6.5 hours. The amount of ammonium persulfate added is 1.2% of the total mass of the reaction system; the combined mass of the six monomers—maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500)-dimethylallyl ammonium chloride (DMAAC-18)—is 40% of the total mass of the reaction system.

[0088] Comparative Example 4

[0089] Step 1: Mix maleic anhydride, sodium hypophosphite, and deionized water thoroughly, place in a 65°C water bath, react for 1 hour, and then cool to room temperature.

[0090] Step 2: Continue to add four monomers to the reaction system in sequence: acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride. The molar ratio of maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500) dimethyl allyl ammonium chloride (DMAAC-18) monomers is 12:12:10:15:1:0.1.

[0091] Step 3: Continue adding ammonium persulfate as the initiator to the reaction system. Adjust the pH of the reaction system to 9 using NaOH as solid particles, and place the reaction system in a 70℃ water bath for 6.5 hours. The amount of ammonium persulfate added is 1.2% of the total mass of the reaction system; the combined mass of the six monomers—maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500)-dimethylallyl ammonium chloride (DMAAC-18)—is 40% of the total mass of the reaction system.

[0092] Comparative Example 5

[0093] Step 1: Mix maleic anhydride, sodium hypophosphite, and deionized water thoroughly, place in a 65°C water bath, react for 1 hour, and then cool to room temperature.

[0094] Step 2: Continue to add four monomers to the reaction system in sequence: acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride. The molar ratio of maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500) dimethyl allyl ammonium chloride (DMAAC-18) monomers is 12:12:10:15:1:0.1.

[0095] Step 3: Continue adding ammonium persulfate as the initiator to the reaction system. Adjust the pH of the reaction system to 10 using NaOH as solid particles, and place the reaction system in a 70℃ water bath for 6.5 hours. The amount of ammonium persulfate added is 1.2% of the total mass of the reaction system; the combined mass of the six monomers—maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500)-dimethylallyl ammonium chloride (DMAAC-18)—is 40% of the total mass of the reaction system.

[0096] Comparative Example 6

[0097] Step 1: Mix maleic anhydride, sodium hypophosphite, and deionized water thoroughly, place in a 65°C water bath, react for 1 hour, and then cool to room temperature.

[0098] Step 2: Continue to add four monomers to the reaction system in sequence: acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride. The molar ratio of maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500) dimethyl allyl ammonium chloride (DMAAC-18) monomers is 12:12:10:15:1:0.1.

[0099] Step 3: Continue adding ammonium persulfate as the initiator to the reaction system. Adjust the pH of the reaction system to 11 using NaOH as solid particles, and place the reaction system in a 70℃ water bath for 6.5 hours. The amount of ammonium persulfate added is 1.2% of the total mass of the reaction system; the combined mass of the six monomers—maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500)-dimethylallyl ammonium chloride (DMAAC-18)—is 40% of the total mass of the reaction system.

[0100] Comparative Example 7

[0101] Step 1: Mix maleic anhydride, sodium hypophosphite, and deionized water thoroughly, place in a 65°C water bath, react for 1 hour, and then cool to room temperature.

[0102] Step 2: Continue to add four monomers to the reaction system in sequence: acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl dimethyl allyl ammonium chloride. The molar ratio of maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500) dimethyl allyl ammonium chloride (DMAAC-18) monomers is 12:12:10:15:1:0.1.

[0103] Step 3: Continue adding ammonium persulfate as the initiator to the reaction system. Adjust the pH of the reaction system to 12 using NaOH as solid particles, and place the reaction system in a 70℃ water bath for 6.5 hours. The amount of ammonium persulfate added is 1.2% of the total mass of the reaction system; the combined mass of the six monomers—maleic anhydride, sodium hypophosphite acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl polyethylene glycol, and octadecyl (APEG500)-dimethylallyl ammonium chloride (DMAAC-18)—is 40% of the total mass of the reaction system.

[0104] Experimental example:

[0105] Step 1: Synthesize the scale inhibitor for well control fluid according to the preparation process and formulation requirements provided in Examples 1-6 and Comparative Examples 1-7 of this invention, and set it aside for use.

[0106] Step 2: Prepare the simulated saline solution required for the evaluation experiment.

[0107] Preparation of saline solution a: Accurately weigh 11.09±0.01g of anhydrous CaCl2, dissolve and dilute it with deionized water, and then make up to 1000mL to prepare a CaCl2 solution;

[0108] Preparation of saline solution b: Accurately weigh 11.09±0.01g of NaCO3, dissolve and dilute it with deionized water, and then make up to 1000mL to prepare a NaCO3 solution;

[0109] Preparation of scale inhibitor solution: Accurately weigh 5.00±0.01g of the scale inhibitor prepared in the example, dissolve and dilute it with deionized water, and then make up to 100mL to prepare a scale inhibitor solution.

[0110] Step 3: Prepare the experimental and blank solutions required for the evaluation experiment.

[0111] Preparation of scale inhibitor experimental group: Measure 200mL of deionized water into a 250mL volumetric flask, add 6.00mL of the above-mentioned saline a (CaCl2 solution) and 5mL of scale inhibitor solution in sequence, shake the volumetric flask slowly to mix it evenly and let it stand for 10min, then slowly add 6.00mL of the above-mentioned saline b (NaCO3 solution), and make up the solution volume to 250mL with deionized water. After mixing the solution evenly, transfer it to a 250mL screw-top bottle for later use;

[0112] Preparation of blank group 1: Measure 200 mL of deionized water into a 250 mL volumetric flask, add 6.00 mL of the above-mentioned saline a (CaCl2 solution) in sequence, slowly shake the volumetric flask to mix it evenly and let it stand for 10 min, then slowly add 6.00 mL of the above-mentioned saline b (NaCO3 solution), and make up the solution volume to 250 mL with deionized water. After mixing the solution evenly, transfer it to a 250 mL screw-top bottle for later use.

[0113] Preparation of blank group 2: Measure 200mL of deionized water into a 250mL volumetric flask, add 6.00mL of the above saline a (CaCl2 solution) in sequence, shake the volumetric flask slowly to mix it evenly and let it stand for 10min, add deionized water to make up the solution volume to 250mL, mix the solution evenly and transfer it to a 250mL screw bottle for later use.

[0114] Step 4: Place the flasks containing the experimental and blank solutions from the previous step in a constant temperature water bath at 90±0.5℃ for 30 minutes. Open the caps to release the gas, then close the caps and continue to place the flasks for 12 hours. After the process, remove the flasks and allow them to cool to room temperature.

[0115] Step 5: Filter the clear liquid from the top of the thread-sealed bottle using medium-speed qualitative filter paper. Collect the filtrate in a clean, dry conical flask and titrate it with a 0.005 mol / L EDTA standard solution according to GB / T 7476. The EDTA standard solution (0.005 mol / L) is prepared and standardized according to the method specified in GB / T 601.

[0116] The scale inhibition rate x (%) of the CaCO3 scale inhibitor is calculated according to formula (1):

[0117]

[0118] In the formula:

[0119] V 阻垢剂 —Ca in the titration solution with added scale inhibitor 2+ The volume of EDTA standard solution consumed at the concentration, in mL (milliliters);

[0120] V 空白1 —Ca in the titration solution of blank group 1 2+ The volume of EDTA standard solution consumed at the concentration, in mL (milliliters);

[0121] V 空白2 —Ca in the titration solution of blank group 2 2+ The volume of EDTA standard solution consumed at the concentration, in mL (milliliters);

[0122] Table 1 below shows the experimental results of evaluating the scale inhibition rate of the kill fluid scale inhibitors on CaCO3 obtained by the preparation methods provided in Examples 1-6 and Comparative Examples 1-7 of the present invention:

[0123] Table 1. Experimental results evaluating the scale inhibition rate of the kill fluid scale inhibitors obtained by the preparation methods provided in Examples 1-6 and Comparative Examples 1-7 on CaCO3.

[0124]

[0125] As shown in Table 1 above, when the pH selected during the preparation of the scale inhibitor is 6-8, the scale inhibitor obtained has a scale inhibition rate of more than 91% for CaCO3 under the conditions of a test temperature of 90℃ and a test time of 12h. This verifies that the scale inhibitor provided in Examples 1-6 of this invention has excellent scale removal effect on CaCO3.

[0126] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this invention, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0127] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0128] The above provides a detailed description of the scale inhibitor for well control fluid, its preparation method, and its application. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing a scale inhibitor for kill fluid, characterized in that, The preparation method comprises the following preparation steps: S1, uniformly mix maleic anhydride, sodium hypophosphite and deionized water, and react at 60-70 ℃ for 1-1.5 h, and then cool to room temperature; S2, add acrylic acid, 2-acrylamide-2-methylpropane sulfonic acid, allyl polyethylene glycol and octadecyl dimethyl allyl ammonium chloride into the cooled solution obtained in step S1 in sequence, and form a reaction system after complete dissolution, and adjust the pH value of the reaction system to 6-8 with NaOH; S3, place the reaction system in a 60-75 ℃ water bath, add an initiator ammonium persulfate, and react at constant temperature for 6-7 h, and then cool to room temperature to obtain the well killing fluid scale inhibitor; The molar ratio of the maleic anhydride, the sodium hypophosphite, the acrylic acid, the 2-acrylamide-2-methylpropane sulfonic acid, the allyl polyethylene glycol and the octadecyl dimethyl allyl ammonium chloride is (10-15):(10-15):(5-10):(8-15):(1-2):(0.05-0.1); The total mass percentage of the maleic anhydride, the sodium hypophosphite, the acrylic acid, the 2-acrylamide-2-methylpropane sulfonic acid, the allyl polyethylene glycol and the octadecyl dimethyl allyl ammonium chloride in the total mass of the reaction system is 35-45 %; The total mass percentage of the maleic anhydride, the sodium hypophosphite, the acrylic acid, the 2-acrylamide-2-methylpropane sulfonic acid, the allyl polyethylene glycol and the octadecyl dimethyl allyl ammonium chloride in the total mass of the reaction system is 35-45 %; 2. The method of claim 1, wherein the scale inhibitor is prepared by the steps of: The molar ratio of the maleic anhydride, the sodium hypophosphite, the acrylic acid, the 2-acrylamide-2-methylpropane sulfonic acid, the allyl polyethylene glycol and the octadecyl dimethyl allyl ammonium chloride is 12:12:10:15:1:0.

1.

3. The method of claim 1, wherein the scale inhibitor is prepared by the steps of: The total mass percentage of the maleic anhydride, the sodium hypophosphite, the acrylic acid, the 2-acrylamide-2-methylpropane sulfonic acid, the allyl polyethylene glycol and the octadecyl dimethyl allyl ammonium chloride in the total mass of the reaction system is 40 %.

4. The method of claim 1, wherein the scale inhibitor is prepared by the steps of: The NaOH is a solid small particle.

5. The method of claim 1, wherein the scale inhibitor is prepared by the steps of: The total mass percentage of the maleic anhydride, the sodium hypophosphite, the acrylic acid, the 2-acrylamide-2-methylpropane sulfonic acid, the allyl polyethylene glycol and the octadecyl dimethyl allyl ammonium chloride in the total mass of the reaction system is 35-45 %.

6. A well killing fluid scale inhibitor obtained by the preparation method in any one of claims 1-5.

7. Application of the well killing fluid scale inhibitor obtained by the preparation method in any one of claims 1-5 as a scale inhibitor for a solid-free brine well killing fluid.

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