Latex flexibilizer for deep well cementation as well as preparation method and application of latex flexibilizer

Abstract

The invention provides a latex flexibilizer for deep well cementation and a preparation method and application thereof.The preparation method comprises the steps that S1, 25-30% of low-molecular-weight liquid polybutadiene, 35-40% of styrene, an emulsifier and water are mixed, high-pressure homogenization and shear emulsification are conducted, and monomer microdroplet emulsion is prepared; the preparation method comprises the following steps: dissolving 10-20% of 2-acrylamido-2-methylpropanesulfonic acid and an equal amount of carboxyl-containing hydrophilic monomer in water to obtain a mixed solution of AMPS and the hydrophilic monomer; s2, heating the monomer microdroplet emulsion with the volume fraction of 15-30% to 60-80 DEG C, and reacting under the conditions of a certain initiator and the like to obtain a reaction solution; and S3, mixing the AMPS and hydrophilic monomer mixed solution, the residual monomer microdroplet emulsion and the reaction solution, and carrying out a constant-temperature reaction to prepare the latex flexibilizer for deep well cementing. The latex flexibilizer prepared by the invention is high in stability, resistant to temperature and salt, and beneficial to application in toughening of deep well cementing cement.

Description

Technical Field

[0001] The invention relates to the technical field of well cementing, and in particular to a latex toughening agent for deep well cementing, and a preparation method and application thereof. Background Art

[0002] Cementing is a key link between drilling and subsequent mining. In this process, cement is injected between the casing and the formation. The cement ring formed mainly plays the role of supporting and protecting the casing and isolating the interlayer fluid. The cracking of cement stone can easily cause interlayer fluid crossflow and casing corrosion, thus affecting cementing safety. As a low-cost, high-strength material, cement can play a good supporting role. However, its high brittleness makes the cement ring very easy to crack in the complex temperature and pressure changes at the bottom of the well and during the fracturing process.

[0003] Toughening agents can use their own elastic and toughness characteristics to improve the ability of cement to withstand deformation and avoid structural failure caused by cracking. Currently common toughening agents include fibers, rubbers, etc., which can dissipate external force impacts by bridging hydration products and their own toughness, thereby improving the toughness of cement on a macro scale. Liquid latex is a micro-scale toughening agent that can be adsorbed on the surface of cement particles and form a polymer film between hydration products to improve the toughness of cement and prevent structural cracking caused by external loads.

[0004] At present, the commonly used toughening latexes are styrene acrylic latex and styrene butadiene latex, but in the application process, they need to be used together with stabilizers to solve the problem of poor stability. With the gradual deepening of oil and gas exploration, the complex downhole environment has put forward higher requirements for the stability and temperature and salt resistance of latex. Styrene acrylic latex and styrene butadiene latex have poor stability in high temperature and alkaline environments and are easy to decompose. In addition, the demulsification of latex in a high-salt environment greatly reduces the toughening performance of latex. Summary of the invention

[0005] In view of this, the present invention provides a latex toughening agent for deep well cementing, a preparation method and an application thereof. The latex toughening agent prepared by the present invention has high stability, temperature resistance and salt resistance, and is conducive to application in the toughening of deep well cementing cement.

[0006] The present invention provides a method for preparing a latex toughening agent for deep well cementing, comprising the following steps:

[0007] S1, mixing 25%-30% by mass of low molecular weight liquid polybutadiene, 35%-40% by mass of styrene, an emulsifier and water, stirring, and then subjecting the obtained mixture to high pressure homogenization and shear emulsification to obtain a monomer microdroplet emulsion;

[0008] Dissolving 10% to 20% by mass of 2-acrylamido-2-methylpropanesulfonic acid and an equal amount of a carboxyl group-containing hydrophilic monomer in water, and adjusting the pH value to a range of 8 to 10 to obtain a mixed solution of AMPS and the hydrophilic monomer;

[0009] S2, heating 15%-30% volume fraction of the monomer micro-emulsion to 60-80° C., reacting in the presence of a persulfate initiator to obtain a reaction solution;

[0010] S3, mixing the AMPS and hydrophilic monomer mixed solution, the remaining monomer micro-droplet emulsion and the reaction solution, and reacting them at a constant temperature to obtain a latex toughening agent for deep well cementing.

[0011] Preferably, in step S1, the carboxyl group-containing hydrophilic monomer is selected from one or more of itaconic acid, acrylic acid and maleic acid.

[0012] Preferably, in step S1, the mass fractions of the low molecular weight liquid polybutadiene, styrene and emulsifier are 26% to 28%, 36% to 38% and 2.2% to 3.5% respectively.

[0013] Preferably, in step S1, the emulsifier is selected from one or more of dodecyl sulfate, dodecylbenzene sulfonate and hexadecyltrimethylammonium halide.

[0014] Preferably, in step S2, the persulfate initiator is selected from potassium persulfate and / or ammonium persulfate.

[0015] Preferably, in step S2, the amount of the persulfate initiator is 3%-5% by mass of the system, and the reaction solution is obtained after reacting for 0.5-1.5 hours.

[0016] Preferably, in step S3, the isothermal reaction time is 2-3 hours, and the latex toughening agent for deep well cementing is obtained by cooling at room temperature.

[0017] The invention provides a latex toughening agent for deep well cementing obtained by the preparation method described above, wherein the latex particle size is 100-160 nm.

[0018] The present invention provides the use of the latex toughening agent for deep well cementing as described above in toughening oil well cement.

[0019] Compared with the prior art, the present invention first prepares a monomer micro-droplet emulsion with a certain proportion of low molecular weight liquid polybutadiene and styrene, and simultaneously adopts 2-acrylamido-2-methylpropane sulfonic acid and an equal amount of carboxyl-containing hydrophilic monomers, and mainly improves the performance structure of the final latex through functional monomer modification. In addition, the present invention reacts the monomer micro-droplet emulsion in steps, and finally obtains a milky latex emulsion, which is a latex toughening agent for deep well cementing. The method of the present invention prepares a heat-resistant and salt-resistant styrene-butadiene latex toughening agent, whose thermal decomposition temperature is greater than 200°C and the particle size can be around 150nm. Experiments show that the latex toughening agent for deep well cementing has a good toughening effect on cement. The heat-resistant and salt-resistant latex toughening agent provided by the present invention has good salt resistance and good freeze-thaw stability.

[0020] In addition, the present invention has low cost, simple process flow and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a thermogravimetric diagram of a temperature-resistant and salt-resistant latex toughening agent prepared in Example 1;

[0022] Figure 2 The particle size distribution diagram of the latex toughening agent prepared in the comparative example and Example 1;

[0023] Figure 3 1 is the stress-strain curve of the latex prepared in the comparative example and example 1. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below in conjunction with specific embodiments. The description in this section is only exemplary and explanatory and should not have any limiting effect on the scope of protection of the present invention.

[0025] The present invention provides a method for preparing a latex toughening agent for deep well cementing, comprising the following steps:

[0026] S1, mixing 25%-30% by mass of low molecular weight liquid polybutadiene, 35%-40% by mass of styrene, an emulsifier and water, stirring, and then subjecting the obtained mixture to high pressure homogenization and shear emulsification to obtain a monomer microdroplet emulsion;

[0027] Dissolving 10% to 20% by mass of 2-acrylamido-2-methylpropanesulfonic acid and an equal amount of a carboxyl group-containing hydrophilic monomer in water, and adjusting the pH value to a range of 8 to 10 to obtain a mixed solution of AMPS and the hydrophilic monomer;

[0028] S2, heating 15%-30% volume fraction of the monomer micro-emulsion to 60-80° C., reacting in the presence of a persulfate initiator to obtain a reaction solution;

[0029] S3, mixing the AMPS and hydrophilic monomer mixed solution, the remaining monomer micro-droplet emulsion and the reaction solution, and reacting them at a constant temperature to obtain a latex toughening agent for deep well cementing.

[0030] In order to solve the problems of poor stability, low temperature resistance and low salt resistance of existing toughening agents, the purpose of the present invention is to provide a latex toughening agent for deep well cementing with excellent performance and a preparation method thereof.

[0031] In the embodiment of the present invention, 25%-30% of the total mass of low molecular weight liquid polybutadiene (LPB), 35%-40% of styrene (St), and 2.2%-3.5% of emulsifier are weighed and added to water. After magnetic stirring, the obtained mixture can be added to an ultra-high pressure homogenizer for shear emulsification to obtain a stable and uniformly dispersed monomer microemulsion (which can be referred to as a monomer microemulsion).

[0032] Specifically, the molecular weight of the low molecular weight liquid polybutadiene is between 1000 and 2000. The emulsifier can be some long chain anion type, long chain quaternary ammonium salt cation type emulsifying surfactant, preferably selected from one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and hexadecyltrimethylammonium bromide. In a preferred embodiment of the present invention, the mass fractions of the low molecular weight liquid polybutadiene, styrene and emulsifier are 26% to 28%, 36% to 38%, 2.2% to 3.5%, and further 26%, 38% and 2.5%, respectively. In addition, the pressure of the high pressure homogenization and shear emulsification can be 1000 bar.

[0033] After obtaining the monomer micro-emulsion, the embodiment of the present invention injects 15%-30% volume fraction of the monomer micro-emulsion into the reaction container, stirs and heats to 60-80°C; then, preferably, add 3%-5% by mass fraction of the initiator solution to the reaction system, preferably reacting for 0.5-1.5h. The initiator solution is mainly composed of persulfate initiators, specifically potassium persulfate and / or ammonium persulfate; the amount of the initiator solution is appropriate to induce the monomer micro-emulsion reaction to obtain the reaction solution.

[0034] In addition, in the embodiment of the present invention, 10%-20% by mass of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and an equal amount of a carboxyl-containing hydrophilic monomer are dissolved in water (distilled water is generally used in the laboratory, with water as the balance, totaling 100%), and the pH value thereof is adjusted to a range of 8 to 10 to obtain an AMPS and hydrophilic monomer solution. The carboxyl-containing hydrophilic monomer may be a short-chain hydrophilic substance containing a carboxyl group, preferably selected from one or more of itaconic acid, acrylic acid and maleic acid, which is mainly beneficial to the functional group-modified latex toughening agent.

[0035] In a specific embodiment of the present invention, the AMPS is reacted with the hydrophilic monomer solution, the remaining monomer micro-droplet emulsion and the reaction solution, preferably at a constant temperature for 2-3 hours, and then cooled to room temperature to obtain a milky latex emulsion, which is a latex toughening agent for deep well cementing.

[0036] The method of the invention has the characteristics of low cost, simple process flow and the like, and is suitable for industrial production.

[0037] Another object of the present invention is to provide a latex toughening agent with high stability, temperature resistance and salt resistance for use in toughening oil well cement.

[0038] The present invention provides a latex toughening agent for deep well cementing obtained by the preparation method described above, wherein the latex particle size is 100-160 nm, and further about 150 nm. The heat-resistant and salt-resistant styrene-butadiene latex prepared by the method of the embodiment of the present invention has a thermal decomposition temperature greater than 200°C, excellent stability and other properties, and is conducive to the application in the toughening of oil well cement and the like.

[0039] In order to further understand the present application, the latex toughening agent for deep well cementing and its preparation method provided by the present application are described in detail below in combination with specific examples. The raw materials of the present invention are commercially available; the molecular weight of low molecular weight liquid polybutadiene (LPB) is between 1000-2000.

[0040] Example 1

[0041] A method for preparing a latex toughening agent for deep well cementing comprises the following steps:

[0042] (1) Weigh 25% of the total mass of liquid polybutadiene (LPB) with a molecular weight of 2000, 38% of styrene (St), and 2.6% of sodium dodecyl sulfate and add them into water. After magnetic stirring, add the obtained mixture into an ultra-high pressure homogenizer for shear emulsification (pressure 1000 bar) to obtain a stable and uniformly dispersed monomer microemulsion. (2) Inject 20% volume fraction of the monomer microemulsion into a 500 ml four-necked flask, stir and heat to 80°C, then add 4% mass fraction of ammonium persulfate solution dropwise into the reaction system, react for 1 hour, and obtain a reaction solution.

[0043] (3) 10% by mass of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and an equal amount of acrylic acid are dissolved in distilled water, and the pH value thereof is adjusted to within a range of 9 to obtain a mixed solution of AMPS and acrylic acid.

[0044] (4) The AMPS and acrylic acid mixed solution, the remaining monomer micro-emulsion, and the reaction solution are uniformly added dropwise to the reaction bottle. After the addition is completed, the mixture is reacted at a constant temperature for 2.5 hours and cooled to room temperature to obtain a milky white latex toughening agent.

[0045] Example 2

[0046] A method for preparing a latex toughening agent for deep well cementing comprises the following steps:

[0047] (1) 30% of the total mass of liquid polybutadiene (LPB) with a molecular weight of 2000, 39% of styrene (St), and 3.4% of sodium dodecylbenzene sulfonate were weighed and added to water. After magnetic stirring, the resulting mixture was added to an ultra-high pressure homogenizer for shear emulsification (pressure 1000 bar) to obtain a stable and uniformly dispersed monomer microemulsion.

[0048] (2) A 29% volume fraction of the monomer microemulsion was injected into a 500 ml four-necked flask, stirred and heated to 60° C., and then a 3% mass fraction of potassium persulfate solution was added dropwise to the reaction system and reacted for 0.5 h to obtain a reaction solution.

[0049] (3) 20% by mass of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and an equal amount of itaconic acid are dissolved in distilled water, and the pH value thereof is adjusted to a range of 8 to 10 to obtain a mixed solution of AMPS and itaconic acid.

[0050] (4) The mixed solution of AMPS and itaconic acid, the remaining monomer microemulsion, and the reaction solution are uniformly added dropwise to the reaction bottle. After the addition is completed, the mixture is reacted at a constant temperature for 2 hours and cooled to room temperature to obtain a milky white latex toughening agent.

[0051] Example 3

[0052] A method for preparing a latex toughening agent for deep well cementing comprises the following steps:

[0053] (1) 28% of the total mass of liquid polybutadiene (LPB) with a molecular weight of 1000, 35% of styrene (St), and 2.2% of hexadecyltrimethylammonium bromide were weighed and added to water. After magnetic stirring, the resulting mixture was added to an ultra-high pressure homogenizer for shear emulsification (pressure 1000 bar) to obtain a stable and uniformly dispersed monomer microemulsion.

[0054] (2) A 15% volume fraction of the monomer microemulsion was injected into a 500 ml four-necked flask, stirred and heated to 70° C., and then a 5% mass fraction of ammonium persulfate solution was added dropwise to the reaction system and reacted for 1.2 h to obtain a reaction solution.

[0055] (3) 15% by mass of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and an equal amount of maleic acid are dissolved in distilled water, and the pH value thereof is adjusted to a range of 8 to 10 to obtain a mixed solution of AMPS and maleic acid.

[0056] (4) The mixed solution of AMPS and maleic acid, the remaining monomer microemulsion, and the reaction solution are uniformly added dropwise to the reaction bottle. After the addition is completed, the mixture is reacted at a constant temperature for 2.5 hours and cooled to room temperature to obtain a latex toughening agent for deep well cementing.

[0057] Example 4

[0058] A method for preparing a latex toughening agent for deep well cementing comprises the following steps:

[0059] (1) Weighing 26% of the total weight of liquid polybutadiene (LPB) with a molecular weight of 1000, 36% of styrene (St), and 2.3% of an emulsifier, and adding them into water, after magnetic stirring, the mixture is added into an ultra-high pressure homogenizer for shear emulsification to obtain a stable and uniformly dispersed monomer microemulsion.

[0060] (2) A 19% volume fraction of the monomer microemulsion was injected into a 500 ml four-necked flask, stirred and heated to 80° C., and then a 4% mass fraction of potassium persulfate solution was added dropwise to the reaction system and reacted for 1 hour to obtain a reaction solution.

[0061] (3) 18% by mass of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and an equal amount of acrylic acid were dissolved in distilled water, and the pH value was adjusted to a range of 8 to 10.

[0062] (4) The mixed solution of AMPS and hydrophilic monomer, the remaining monomer microemulsion, and the reaction solution are uniformly added dropwise to the reaction bottle. After the addition is completed, the mixture is reacted at a constant temperature for 3 hours and cooled to room temperature to obtain a latex toughening agent for deep well cementing.

[0063] Comparison example:

[0064] (1) 26% of the total weight of liquid polybutadiene (LPB) with a molecular weight of 2000, 38% of styrene (St), and 2.6% of an emulsifier were added to water. After magnetic stirring, the resulting mixture was added to an ultra-high pressure homogenizer for shear emulsification to obtain a stable and uniformly dispersed monomer microemulsion.

[0065] (2) A 20% volume fraction of the monomer microemulsion was injected into a 500 ml four-necked flask, stirred and heated to 80° C., and then 4% by mass of potassium persulfate was added dropwise to the reaction system and reacted for 1 hour to obtain a reaction solution.

[0066] (3) 15% by mass of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) was dissolved in distilled water, and the pH value thereof was adjusted to within the range of 9.

[0067] (4) AMPS, the remaining monomer microemulsion, and the reaction solution are uniformly added dropwise to the reaction bottle. After the addition is completed, the reaction is carried out at a constant temperature for 2.5 hours and then cooled to room temperature to obtain a milky white latex emulsion.

[0068] The latex emulsion obtained in the embodiment of the present invention was tested for performance, and the results are as follows.

[0069] Figure 1 This is a thermogravimetric diagram of a heat-resistant and salt-resistant latex toughening agent prepared in Example 1, with a heating rate of 10°C / min. It can be seen from the figure that the thermal decomposition temperature of the prepared latex toughening agent for deep well cementing is greater than 200°C.

[0070] The particle size distribution obtained in the control example is as follows Figure 2 a, the stress-strain curve is shown in Figure 3 As shown; the salt resistance stability is shown in Table 1, which is a characterization of the salt resistance of the latex prepared in the comparative example and Example 1; the freeze-thaw stability is shown in Table 2, which is a characterization of the freeze-thaw stability of the latex prepared in the comparative example and Example 1. Figure 2 a is the latex prepared in comparative example, Figure 2 b is a latex toughening agent for deep well cementing prepared in Example 1, and the particle sizes of both are about 150 nm.

[0071] It can be seen from Table 1 that the latex prepared in the comparative example precipitates in a saturated CaCl2 solution, while the latex toughening agent for deep well cementing prepared in Example 1 has good stability in saturated MgCl2, NaCl and CaCl2 solutions.

[0072] It can be seen from Table 2 that the latex prepared in the comparative example flocculated and settled at -15°C, while the latex toughening agent for deep well cementing prepared in Example 1 remained stable at -5°C to -15°C.

[0073] Figure 3 1 and 2 are stress-strain curves of the latex prepared in the comparative example and Example 1; it can be seen from the figure that the latex prepared in Example 1 has a higher deformation capacity and a better toughening effect.

[0074] Table 1 Salt resistance characterization of latex prepared in comparative example and example 1

[0075]

[0076] Table 2 Freeze-thaw stability characterization of the latex prepared in the comparative example and Example 1

[0077]

[0078] Experiments show that the particle size of the latex toughening agent for deep well cementing prepared in Examples 2, 3, and 4 is about 150 nm, and the high temperature stability, salt resistance, freeze-thaw stability, and toughening performance thereof are similar to those of the latex toughening agent for heat and salt resistance prepared in Example 1. In summary, the latex toughening agent for deep well cementing provided by the present invention has excellent temperature resistance, freeze-thaw stability, and salt resistance, and can improve the toughness of cement stone.

[0079] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a latex toughening agent for deep well cementing, characterized in that: The following steps are involved: S1, mixing 25%-30% by mass of low molecular weight liquid polybutadiene, 35%-40% by mass of styrene, an emulsifier and water, stirring, and then subjecting the obtained mixture to high pressure homogenization and shear emulsification to obtain a monomer microdroplet emulsion; Dissolving 10% to 20% by mass of 2-acrylamido-2-methylpropanesulfonic acid and an equal amount of a carboxyl group-containing hydrophilic monomer in water, and adjusting the pH value to a range of 8 to 10 to obtain a mixed solution of AMPS and the hydrophilic monomer; S2, heating 15%-30% volume fraction of the monomer micro-emulsion to 60-80° C., reacting in the presence of a persulfate initiator to obtain a reaction solution; S3, mixing the AMPS and hydrophilic monomer mixed solution, the remaining monomer micro-droplet emulsion and the reaction solution, and reacting them at a constant temperature to obtain a latex toughening agent for deep well cementing.

2. The preparation method according to claim 1, characterized in that: In step S1, the carboxyl group-containing hydrophilic monomer is selected from one or more of itaconic acid, acrylic acid and maleic acid.

3. The preparation method according to claim 1, characterized in that: In step S1, the mass fractions of the low molecular weight liquid polybutadiene, styrene and emulsifier are 26% to 28%, 36% to 38% and 2.2% to 3.5% respectively.

4. The preparation method according to claim 3, characterized in that: In step S1, the emulsifier is selected from one or more of dodecyl sulfate, dodecylbenzene sulfonate and hexadecyltrimethylammonium halide.

5. The preparation method according to claim 1, characterized in that: In step S2, the second persulfate initiator is selected from potassium persulfate and / or ammonium persulfate.

6. The preparation method according to any one of claims 1 to 5, characterized in that: In step S2, the amount of the persulfate initiator used is 3%-5% by mass of the system, and the reaction solution is obtained after reacting for 0.5-1.5 hours.

7. The preparation method according to claim 6, characterized in that: In step S3, the isothermal reaction time is 2-3 hours, and the latex toughening agent for deep well cementing is obtained by cooling at room temperature.

8. The latex toughening agent for deep well cementing obtained by the preparation method according to any one of claims 1 to 7, characterized in that: The latex particle size is 100 to 160 nm.

9. Use of the latex toughening agent for deep well cementing as claimed in claim 8 in toughening of oil well cement.

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