CN110357995A - A kind of low-molecular weight polymer and preparation method thereof that end is function modified - Google Patents

Abstract

The invention relates to a low-molecular-weight polymer with terminal function modification and a preparation method thereof. The method is to carry out a copolymerization reaction of a low-molecular-weight polymer monomer and a RAFT chain transfer agent in the presence of an initiator through a radical polymerization method to obtain A low-molecular-weight polymer with terminal functional modification; the low-molecular-weight polymer monomer is a betaine type amphiphilic polymer monomer, an acrylamide monomer, a quaternary ammonium salt type long carbon chain association monomer, 2-acrylamide- One or more of 2‑methylpropanesulfonic acids; the two ends of the formed polymer are respectively for 1‑3 and Functional group, n is 2-4, so that the ends of polymerized monomers can be connected to each other through the non-covalent interaction of host-guest inclusion. The molecular weight of the polymer is controlled below 1 million, and the underground of the solution quickly recovers and increases viscosity after shearing.

Description

A kind of terminal function modified low molecular weight polymer and preparation method thereof

technical field

The invention belongs to the technical field of polymer material preparation, and in particular relates to a low-molecular-weight polymer with terminal function modification and a preparation method thereof.

Background technique

The information disclosed in this background section is only intended to increase the understanding of the general background of the present invention, and is not necessarily taken as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

Reservoirs in my country have strong heterogeneity, low recovery factor, and great chemical flooding potential. As the main body of domestic waterflood development oilfields enters the "double high" development stage with high water cut and high recovery degree, polymer flooding, as an important chemical flooding enhanced oil recovery technology, has been industrialized and developed rapidly in my country, and has become the first stage of this stage. It is an important technical means of oil field "stabilizing oil and controlling water". Conventional polymer oil displacement agent partially hydrolyzed polyacrylamide (HPAM) has the problem of poor temperature and salt resistance and shear resistance, so amphiphilic polymers containing hydrophobic groups have been developed.

However, existing polymer systems, despite their improved performance, are not fully suitable for offshore oilfields. It is difficult for polymers to meet the fast dissolution requirements of offshore platforms. The space of the offshore platform is small, it is difficult to improve the polymer dissolution effect by increasing the aging tank or prolonging the aging time. The injection pressure of the polymer solution is too high or even blocks the formation. In addition, the offshore platform has a large well spacing, and the polymer is easily sheared and degraded during the migration process, resulting in viscosity loss. In order to achieve the target viscosity, the amount or molecular weight of the polymer needs to be increased, which undoubtedly increases the dissolution time and corresponding economic costs.

The high molecular weight of the polymer is the main reason for its low dissolution rate. For the polymer formed by covalent linkage, it is difficult to completely solve the above key problems by simply reducing the molecular weight. The difficulties are mainly reflected in: First, the molecular weight distribution of polymers obtained by conventional polymerization methods such as free radical polymerization is wide, and it is difficult to effectively control the molecular weight. Second, although lowering the molecular weight can enhance polymer solubility, it also reduces the hydrodynamic radius of the polymer, thereby weakening its viscosity-increasing ability. The inventors have found that reducing polymer molecular weight while maintaining polymer viscosity is a difficult problem in current technology.

Contents of the invention

In view of the problems existing in the above prior art, an object of the present invention is to provide a low-molecular-weight polymer with terminal functional modification and a preparation method thereof. The polymer has viscosity-increasing properties similar to conventional high-molecular-weight polymers, and has molecular weight controllability, instant solubility and viscosity-shear recovery, and has great application potential. The polymer is synthesized by the method of reversible addition-fragmentation chain transfer (RAFT). With the help of supramolecular chemistry, small molecular units are connected into chain aggregates through non-covalent bonds to form a supramolecular polymer.

In order to solve the above technical problems, the technical solution of the present invention is:

In the first aspect, a method for preparing a low-molecular-weight polymer with terminal functional modification, the method is to carry out a copolymerization reaction of a low-molecular-weight polymer monomer and a RAFT chain transfer agent in the presence of an initiator through a free radical polymerization method to obtain Low-molecular-weight polymers with terminal functional modifications;

The low molecular weight polymerizable monomer is one or more of betaine type monomer, acrylamide monomer, quaternary ammonium salt type long carbon chain associated monomer, 2-acrylamide-2-methylpropanesulfonic acid ;

RAFT chain transfer agent is based on dithioester type RAFT chain transfer agent, forming a series of RAFT chain transfer agents with host-guest inclusion and π-π conjugated non-covalent bond functional groups.

In some embodiments, the RAFT chain transfer agent is represented by formula I,

Wherein α-CD is α-cyclodextrin, m is 1-3, n is 2-4.

In some embodiments, the structure of the betaine-type monomer is shown in formula II,

In some embodiments, the structural formula of the quaternary ammonium salt type long carbon chain associated monomer is:

n ₁ is 11-17; or _n2 is 11-17.

In some embodiments, the structural formula of the acrylamide monomer is

In the present invention, the end of the polymer monomer is modified by a chain transfer agent, so that the two ends of the formed polymer are respectively for 1-3 and Functional group, n is 2-4, so that the ends of polymerized monomers can be connected to each other through the non-covalent interaction of host-guest inclusion.

The preparation method of the above-mentioned low-molecular-weight polymer modified by terminal function, the specific steps are:

Dissolving the low molecular weight monomer and RAFT chain transfer agent in deionized water, heating at a constant temperature, blowing nitrogen gas, and injecting the initiator, the product obtained after the reaction is washed and purified with ethanol, and dried in vacuum to obtain a low molecular weight polymer.

In some embodiments, the mass concentration of low molecular weight polymerized monomers is 15% to 30%; in some embodiments, the amount of initiator accounts for 0.01% to 0.1% of the total mass of monomers; in some embodiments, RAFT chain transfer agent The mass concentration is 0.01% to 0.2%. The invention optimizes the structure of the polymer and introduces a strong hydrophilic group or a strong hydrophobic group to synthesize a functionalized low-molecular polymer suitable for different oil reservoir conditions and modified at the end. The mass concentration in the above range is most suitable for the synthesis of low molecular weight polymers.

In some embodiments, the initiation temperature of the copolymerization reaction is 35°C to 45°C, and the reaction time is 5-7h; in some embodiments, the copolymerization reaction is carried out under the protection of an inert gas; in some embodiments, the initiator is Azobisisobutyronitrile (AIBN).

The second aspect provides the low-molecular-weight polymer with terminal function modification obtained by the above-mentioned preparation method, and the molecular weight is less than 1 million.

In some embodiments, the monomer is an acrylamide monomer, and the obtained low molecular weight polymer is shown in formula V,

Wherein, m is 1-3, and n is 2-4.

The reaction scheme is as follows:

In some embodiments, the monomers are betaine type monomers, acrylamide monomers, and quaternary ammonium salt type long carbon chain associated monomers, and the obtained low molecular weight polymers are shown in formula VI or VII,

Wherein, m is 1-3, and n is 2-4.

In some embodiments, the monomer is a quaternary ammonium salt type long carbon chain associative monomer and an acrylamide monomer, and the obtained low molecular weight polymer is shown in formula VIII,

R is a C ₁₂ -C ₄₀ straight chain or branched chain alkyl group, wherein m is 1-3 and n is 2-4.

In some embodiments, the monomer is 2-acrylamide-2-methylpropanesulfonic acid, and the obtained low molecular weight polymer is shown in formula IX,

Wherein, m is 1-3, and n is 2-4.

Compared with the existing polymer system with poor dissolution effect and large viscosity loss, the new low-molecular-weight polymer with terminal function modification mentioned in the present invention has molecular weight controllability, instant solubility and shear recovery. The principle is to use a dithioester-type high-efficiency chain transfer agent to synthesize a terminal low-molecular-weight polymer with a controlled molecular weight by using the reversible addition-fragmentation chain transfer (RAFT) method. With the help of supramolecular polymer chemistry, the host-guest inclusion complex will The small molecular units are connected into chain aggregates through non-covalent bonds, forming supramolecular polymers and exhibiting a viscosity-increasing ability similar to that of traditional covalent polymers. By controlling the amount of RAFT chain transfer agent, the number of polymer chains is regulated, so as to control the molecular weight of the polymer below 1 million, and ensure the rapid dissolution of the polymer (25°C, <30min). In addition, the new low-molecular-weight polymers are connected by dynamic reversible non-covalent bonds, which avoids the shortcomings of traditional polymers that cannot be recovered after the covalent bonds are broken and degraded after high-speed shearing, and realizes the underground rapid recovery and viscosity increase of the solution after shearing.

In the third aspect, the application of the above-mentioned low molecular weight polymer in a displacement control agent or an oil displacement agent.

In the fourth aspect, a drive control agent includes the above-mentioned low molecular weight polymer.

The above-mentioned displacing agent includes 0.05-10.00% of the low-molecular-weight polymer, 0.1-10.00% of the surfactant, and the rest is water.

The synergistic effect of low molecular weight polymers and surfactants is hydrophobic association. The surfactant forms spherical micelles or rod micelles in the polymer solution, constructs a weak gel system with micellar synergistic polymer association, and strengthens the viscosity-increasing effect of the system at low concentrations.

In some embodiments, 0.1-2% of low-molecular-weight amphiphilic polymer, 1%-2% of surfactant, and the rest is water.

In some embodiments, one of cationic surfactants, anionic surfactants, nonionic surfactants, or zwitterionic surfactants; preferably Tween 80, OP-10, glucoside, alkyl One of sodium benzenesulfonate and nonylphenol polyoxyethylene ether.

The preparation method of above-mentioned regulating and displacing agent, concrete steps are:

The low-molecular-weight amphiphilic polymer is added to distilled water, and then a surfactant is added and mixed to obtain a weak gel system for oilfield adjustment and flooding.

Description of drawings

The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present application, and the schematic embodiments of the present invention and their descriptions are used to explain the present invention, and do not constitute improper limitations to the present invention.

Figure 1 shows the change of water content at the outlet with displacement time;

Fig. 2 is a diagram showing the variation of recovery factor with displacement time;

Fig. 3 is the nuclear magnetic spectrum of the low molecular weight polymer prepared by embodiment 1;

Fig. 4 is the nuclear magnetic spectrum of the low molecular weight polymer prepared in embodiment 3.

Beneficial effects of the present invention:

(1) The novel low-molecular-weight polymer with terminal functional modification in the present invention has good stability and universal applicability.

(2) The novel low-molecular-weight polymer with terminal functional modification in the present invention has both low molecular weight and self-assembly ability, and forms a supramolecular polymer through non-covalent interaction between polymer molecules, which has conventional high-molecular-weight polymerization Thickening properties of substances.

(3) The novel low-molecular-weight polymer with terminal functional modification in the present invention has instant solubility and shear recovery, and can be connected to each other through host-guest inclusion to form an instant supramolecular polymer with shear recovery properties .

(4) The novel low-molecular-weight polymer with terminal function modification in the present invention has molecular weight controllability, and the molecular weight of the polymer can be precisely regulated by using the RAFT method, so that the target molecular weight and molecular weight distribution can be obtained. polymer products.

(5) The present invention uses terminally functionalized amphiphilic polymers as construction units to construct supramolecular polymers through non-covalent bond forces such as electrostatic interactions and hydrophobic associations, and further cooperates with surfactants to construct weak gel systems , to overcome the problem of easy shear denaturation of the traditional gel system, and the system also has a good viscosity-increasing effect at low concentrations. The terminal functionalized amphiphilic polymer-based weak gel system of the present invention can effectively perform profile control and water plugging, and plug high-permeability layers, thereby increasing the swept volume of injected water, stabilizing oil and controlling water.

(6) The preparation method of the present invention is simple, practical and easy to popularize.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the present invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It should be noted that the terminology used here is only for describing specific implementations, and is not intended to limit the exemplary implementations according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof. Below in conjunction with embodiment the present invention is further described

Example 1:

Accurately weigh a certain amount of acrylamide monomer and RAFT chain transfer agent and dissolve in a certain amount of deionized water, the mass concentration of acrylamide monomer is 25%, the mass concentration of RAFT chain transfer agent is 0.05%, and then placed in 250mL In a three-neck flask, stir continuously to dissolve it. The three-neck flask was placed in a constant temperature water bath, N ₂ was passed through and stirred for 0.5 hours until the solution was clear. The initiator is azobisisobutyronitrile (AIBN) injected with a syringe, and the amount of the initiator is 0.05% of the total mass of the monomers. Raise the temperature to 40°C, continue to feed N ₂ and keep stirring, seal the three-necked flask and place it for 6 hours, and finally obtain a transparent gel-like product, take it out and cut it into small pieces, purify it with ethanol precipitation three times, and vacuum-dry and granulate the low-molecular-weight polymer product, the calculated yield is about 92%, and the polymer shown in formula V is obtained. Its nuclear magnetic spectrum is shown in Figure 3, and j in Figure 3 represents α-cyclodextrin.

Example 2:

Accurately take a certain amount of 2-acrylamide-2-methylpropanesulfonic acid (AMPS) and RAFT chain transfer agent and dissolve it in a certain amount of deionized water, the mass concentration of monomer is 30%, the mass of RAFT chain transfer agent The concentration is 0.1%, and then placed in a 250mL three-neck flask, stirring constantly to dissolve it. The three-neck flask was placed in a constant temperature water bath, N ₂ was passed through and stirred for 0.5 hours until the solution was clear. The initiator is azobisisobutyronitrile (AIBN) injected with a syringe, and the amount of the initiator is 0.1% of the total mass of the monomers. Raise the temperature to 45°C, continue to feed N ₂ and keep stirring, seal the three-necked flask and place it for 6 hours, and finally obtain a transparent gel-like product, take it out and cut it into small pieces, purify it with ethanol precipitation three times, and vacuum-dry and granulate the low-molecular-weight polymer product. A polymer represented by formula IX is obtained.

Example 3

Accurately weigh a certain amount of betaine type monomer (formula II), acrylamide, quaternary ammonium salt type long carbon chain association monomer (formula III, _n2 is 11,) and RAFT chain transfer agent dissolved in a certain amount of In deionized water, the mass concentration of the monomer is 20%, and the mass concentration of the RAFT chain transfer agent is 0.15%, and then placed in a 250mL three-necked flask and continuously stirred to dissolve it. The three-neck flask was placed in a constant temperature water bath, N ₂ was passed through and stirred for 0.5 hours until the solution was clear. The initiator is azobisisobutyronitrile (AIBN) injected with a syringe, and the amount of the initiator is 0.05% of the total mass of the monomers. Raise the temperature to 35°C, continue to feed N ₂ and keep stirring, seal the three-necked flask and place it for 5.5 hours, and finally obtain a transparent gel-like product, take it out and cut it into small pieces, purify it with ethanol precipitation three times, and vacuum-dry and granulate the low-molecular-weight polymer product. The polymer represented by formula VII was obtained, and its nuclear magnetic spectrum is shown in FIG. 4 .

Viscosity test

The low molecular weight polymer prepared in Example 1 was placed in distilled water to prepare a 2000 ppm polymer solution, and the polymer was completely dissolved after stirring for 12 minutes. After shearing at 6rpm for 20 minutes, the measured viscosity is 6952mPa·s, and after high-speed shearing at 600rpm, the viscosity after 10min of high-speed shearing is 4179mPa·s, and after returning to 6rpm and shearing for 10min, the viscosity measured under the same conditions is 6871mPa ·s.

The low molecular weight polymer prepared in Example 3 was placed in distilled water to prepare a 2000 ppm polymer solution, and the polymer was completely dissolved after stirring for 12 minutes. After shearing at 6rpm for 20 minutes, the measured viscosity is 3350mPa·s, and after high-speed shearing at 600rpm, the viscosity after 10min of high-speed shearing is 2570mPa·s, and after returning to 6rpm and shearing for 10min, the viscosity measured under the same conditions is 3321mPa ·s.

Example 4:

This implementation example provides a construction and application process of a weak gel system for oilfield control and flooding. Add 0.20 wt% of low molecular weight polymer (the polymer shown in formula VII prepared in Example 3, polymer molecular weight is about 50×10 ⁴ ) to distilled water, stir for 10 minutes, just can make the polymer fully dissolve and mix uniformly ; Add 2wt% sodium dodecylbenzenesulfonate to the prepared polymer solution, stir for 20 minutes, ensure that the sodium dodecylbenzenesulfonate is fully dissolved and mixed evenly, and adjust the pH value of the solution to the actual condition of the reservoir . The viscosity is 25215mPa·s under the condition of 65°C and 6rpm viscometer, and the viscosity is 23171mPa·s after shearing at 3000rpm for 1min under the same conditions.

In the artificial simulated core plate (45×45×6cm, average porosity 35.86%, gas permeability of the upper layer 1750×10 ^-3 μm ² , gas permeability of the lower layer 1500×10 ^-2 μm ² ), crude oil The viscosity is 50.8mPa·s (65°C), the irreducible water saturation is 25.6%, the timing of gel injection is 80% water content, after injecting 0.1PV weak gel and continuing water flooding, the cumulative oil recovery rate is 70%, and the displacement effect is as follows: Figure 1-2.

Example 5:

This implementation example provides a construction process of a weak gel system for oil field adjustment and flooding, adding 0.10wt% low molecular weight polymer (formula VIII, quaternary ammonium salt type long carbon chain association monomer molar ratio 1.5%) to distilled water , the molecular weight of the polymer is about 40×10 ⁴ ), stirring for 10 minutes, can ensure that the polymer is fully dissolved and mixed uniformly; add 1.2wt% lauryl glucoside to the prepared polymer solution, and stir for 20 minutes to ensure that the lauryl The glucoside is fully dissolved and mixed evenly, and the pH value of the solution is adjusted to the actual conditions of the reservoir. The viscosity is 19850mPa·s at 45°C and the viscometer speed is 6rpm, and the viscosity is measured under the same conditions after shearing at 2500rpm for 1min. 18734mPa·s.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. a kind of preparation method for the low-molecular weight polymer that end is function modified, it is characterised in that: the method is low molecule Polymerized monomer and RAFT agent are measured under initiator existence condition, copolyreaction is carried out by radical polymerization, is obtained The function modified low-molecular weight polymer in end；

The low-molecular-weight polymeric monomer is betaine type monomer, acrylamide monomer, quaternary Long carbon chain associating monomer, 2- One of acrylamide-2-methyl propane sulfonic is a variety of；

RAFT agent is based on double thioesters type RAFT agents, and being formed has host-guest inclusion and π-pi-conjugated non- The serial RAFT agent of covalent bond effect functional group.

2. the preparation method of the function modified low-molecular weight polymer in end according to claim 1, it is characterised in that: RAFT agent as shown in formula I,

Wherein α-CD is alpha-cyclodextrin, m For 1-3, n 2-4.

3. the preparation method of the function modified low-molecular weight polymer in end according to claim 1, it is characterised in that: tool Body step are as follows:

Low-molecular-weight polymeric monomer and RAFT agent are dissolved in deionized water, heated at constant temperature, are passed through nitrogen, injection causes Agent, the product obtained after reaction are purified by ethanol washing, and vacuum drying obtains low-molecular weight polymer；

Preferably, low-molecular-weight polymeric monomer mass concentration is 20%~30%；

Preferably, initiator amount accounts for the 0.01%~0.1% of monomer gross mass；

Preferably, RAFT agent mass concentration is 0.01%~0.2%；

Preferably, the initiation temperature of copolyreaction is 35 DEG C~45 DEG C, and the time of reaction is 5-7h；

Preferably, copolyreaction carries out under inert gas protection；

Preferably, initiator is azodiisobutyronitrile.

4. the function modified low-molecular weight polymer in the end that the described in any item preparation methods of claim 1-3 obtain；

Preferably, molecular weight is less than 1,000,000；

Preferably, monomer is acrylamide monomer, obtained low-molecular weight polymer as shown in formula IV,

Wherein, m 1- 3, n 2-4.

5. the function modified low-molecular weight polymer in end as claimed in claim 4, which is characterized in that monomer is betaine type list Body, obtained low-molecular weight polymer as shown in formula VI or formula VII,

Wherein, m 1-3, n 2-4.

6. the function modified low-molecular weight polymer in end as claimed in claim 4, which is characterized in that monomer is that quaternary is long Carbochain associating monomer and acrylamide monomer, obtained low-molecular weight polymer as shown in formula VI,

R is C₁₂-C₄₀Linear or branched alkyl group, wherein m 1-3, n 2-4.

7. the function modified low-molecular weight polymer in end as claimed in claim 4, which is characterized in that monomer is 2- acryloyl Amine -2- methyl propane sulfonic acid, obtained low-molecular weight polymer as shown in formula Ⅸ,

Wherein, m 1- 3, n 2-4.

8. the function modified low-molecular weight polymer in the described in any item ends claim 4-7 is in profile control agent or oil displacement agent Using.

9. a kind of profile control agent, which is characterized in that including the function modified low molecular weight in the described in any item ends claim 4-7 Polymer.

10. profile control agent as claimed in claim 9, which is characterized in that including stating low-molecular weight polymer 0.05~10.00%, table Face activating agent 0.1%~10.00%, remaining as water；

Preferably, low molecule amphipathic polymer 0.1~2%, surfactant 1%~2%, remaining as water；

Preferably, cationic surface active agent, anionic surfactant, nonionic surface active agent or amphoteric ion One of type surfactant；Preferably Tween80, OP-10, glucoside, sodium alkyl benzene sulfonate, nonylphenol polyoxyethylene ether One of；

Preferably, the preparation method of above-mentioned profile control agent, specific steps are as follows:

Low molecular weight amphipathic polymer is added in distilled water, surfactant mixing is then added, obtains oil field transfer drive use Weak Gels system.