阅读说明：本技术 粒度、强度可控型聚合物颗粒及其制备方法 (Particle size and strength controllable polymer particles and preparation method thereof ) 是由 李翔 于萌 铁磊磊 鞠野 于 2021-08-10 设计创作，主要内容包括：本发明提供了一种聚合物凝胶,其采用包括浓度是9000～15000ppm的乳液型聚丙烯酰胺溶液、交联剂和促交剂以及可选地pH调节剂的原料制成；其中,聚丙烯酰胺溶液、交联剂和促交剂的重量比是1:(0.28～0.34):(0.14～0.3)。本发明还提供了一种粒度、强度可控型聚合物颗粒,通过将前述聚合物凝胶在线研磨而制备得到。借助本发明,不仅能够降低生产成本,而且能够实现聚合物颗粒与地层的良好匹配。(The invention provides a polymer gel which is prepared from raw materials including 9000-15000 ppm emulsion type polyacrylamide solution, a cross-linking agent, a cross-linking promoter and optionally a pH regulator; wherein the weight ratio of the polyacrylamide solution to the cross-linking agent to the crosslinking promoter is 1 (0.28-0.34) to (0.14-0.3). The invention also provides polymer particles with controllable granularity and strength, which are prepared by grinding the polymer gel on line. By means of the invention, not only can the production cost be reduced, but also good matching of the polymer particles and the formation can be realized.)

1. The polymer gel is characterized by being prepared from raw materials including a polyacrylamide solution with a concentration of 9000-15000 ppm, a crosslinking agent, a crosslinking promoter and optionally a pH regulator;

wherein the weight ratio of the emulsion polyacrylamide solution to the cross-linking agent to the crosslinking promoter is 1 (0.28-0.34) to 0.14-0.3.

2. The polymer gel of claim 1, wherein the polyacrylamide has a degree of hydrolysis of no more than 10%.

3. The polymer gel of claim 1, wherein the crosslinker is a phenolic resin crosslinker.

4. The polymer gel of claim 1, wherein the crosslinking promoter is any one or more of polyethyleneimine, ammonium acetate and ammonium chloride having a molecular weight of 1200-1800.

5. The polymer gel of claim 1, wherein the pH adjusting agent is any one or more of oxalic acid, citric acid, sodium carbonate, and sodium bicarbonate.

6. The method of preparing a polymer gel according to any one of claims 1 to 5, comprising:

(1) dissolving polyacrylamide in water to obtain an emulsion polyacrylamide solution with the concentration of 9000-15000 ppm;

(2) and sequentially adding a cross-linking agent and a crosslinking promoter into the polyacrylamide solution according to a ratio, and stirring to generate a glue reaction.

7. The preparation method according to claim 6, wherein in the step (2), the gelling reaction is performed at a pH of 7 to 8 and a temperature of 40 ℃ to 65 ℃.

8. A polymer particle having a controllable particle size and strength, which is prepared by on-line grinding of the polymer gel according to any one of claims 1 to 5.

9. The particle size, strength controllable polymer particles of claim 8, wherein the polymer particles have a particle size of 100 to 300 μm, 2 to 10 μm, or 10 to 30 μm.

Technical Field

The invention relates to the technical field of offshore oilfield development, in particular to a dispersed polymer particle with controllable granularity and strength and a preparation method thereof.

Background

In recent years, the traditional polymer microspheres play a very important role in oil and water stabilization and control of offshore oil fields in medium and high water periods, but also have some problems. The existing preparation method of the polymer microsphere mainly comprises emulsion polymer, dispersion polymerization and the like, and the particle size of the prepared polymer microsphere is nano-scale, submicron-scale or micron-scale. The microsphere has a wider particle size distribution range, so that the microsphere has poor matching with the pore throat and the field construction effect is influenced. In addition, when the hydration and expansion time of the microspheres is longer, the strength is reduced, and the plugging strength is limited. In addition, a large amount of surfactant is used in the preparation process, which increases the cost.

Some studies have been made to solve the above problems. For example:

the Chinese patent application with the application number of 201410435856.1 discloses a temperature-resistant and salt-resistant HPAM/Cr³⁺The phenolic aldehyde composite crosslinking weak gel profile control water shutoff agent comprises the following components: 0.10 to 0.20 percent of partially hydrolyzed polyacrylamide, 0.001 to 0.008 percent of metal cross-linking agent, 0.02 to 0.08 percent of organic cross-linking agent, 0.05 to 0.6 percent of pH regulator and the balance of water.

Chinese patent application with application number 201610813581.X discloses a low-temperature salt-resistant cross-linked polymer weak gel profile control and flooding agent, which comprises the following components: 0.08-0.3 part of anionic polyacrylamide, 0.1-5 parts of organic metal composite cross-linking agent, 0.1-2 parts of pH regulator and 100 parts of oilfield produced water.

However, due to unreasonable selection of components, limitation of preparation process and the like, the polymer profile control agent disclosed in the above patent application has problems of ineffective control of particle size and strength, uneven particle strength and the like, and thus the above problems cannot be effectively solved.

Therefore, it is highly desirable to provide a dispersed polymer microsphere technology with controllable strength and particle size, which can ensure the effective application thereof in reservoirs with different degrees of mineralization and different permeabilities.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide the dispersed polymer particles with controllable strength and granularity, which can ensure the effective application of the dispersed polymer particles in reservoirs with different degrees of mineralization and different permeabilities.

The technical scheme of the invention is as follows:

in one aspect, the invention provides a polymer gel, which is prepared from raw materials including 9000-15000 ppm emulsion polyacrylamide solution, a crosslinking agent, a crosslinking promoter and optionally a pH regulator;

wherein the weight ratio of the polyacrylamide solution to the cross-linking agent to the crosslinking promoter is 1 (0.28-0.34) to (0.14-0.3).

Preferably, the polyacrylamide has a degree of hydrolysis not exceeding 10%.

Preferably, the crosslinking agent is a phenolic resin crosslinking agent.

Preferably, the crosslinking promoter is one or more of polyethyleneimine, ammonium acetate and ammonium chloride with the molecular weight of 1200-1800.

Preferably, the pH adjusting agent is any one or more of oxalic acid, citric acid, sodium carbonate and sodium bicarbonate.

In another aspect, the present invention provides a method for preparing the polymer gel, comprising:

(1) dissolving polyacrylamide in water to obtain an emulsion polyacrylamide solution with the concentration of 9000-15000 ppm;

(2) and sequentially adding a cross-linking agent and a crosslinking promoter into the polyacrylamide solution according to a ratio, and stirring to generate a glue reaction.

Preferably, in the step (2), the gelling reaction is carried out at a pH value of 7-8 and a temperature of 40-65 ℃.

In another aspect, the present invention provides a particle size, strength-controllable polymer particle prepared by on-line grinding of the above-mentioned polymer gel.

Preferably, the particle size of the polymer particles is 100-300 μm, 2-10 μm or 10-30 μm.

Compared with the prior art, the invention has at least the following beneficial effects:

the invention is different from the existing microsphere system, and does not use a surfactant, thereby reducing the cost.

The invention does not adopt white oil, and adopts polyacrylamide which is not emulsion, thereby ensuring good compatibility of formation water and good injectability.

The polyacrylamide adopted by the invention has low hydrolysis degree, can ensure the temperature resistance and salt resistance of the system without adding salt-resistant and temperature-resistant groups, further reduces the cost and simultaneously ensures the gel system, namely, no precipitate is formed when the polyacrylamide as the main agent, the phenolic resin cross-linking agent and the polyethyleneimine as the cross-linking promoter are mixed.

The invention can adjust the size and the strength of polymer particles at any time according to the condition of an operation site, thereby ensuring that the system realizes the matching according to the permeability of a stratum and the development characteristics of a pore canal.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. In the drawings:

FIG. 1 shows the results of the effect test of example 4, in which the blocking rate varied with the concentration of the control agent.

FIG. 2 shows the result of the change of the injection pressure of the polymer particles with the PV number in the effect test of example 4.

Detailed Description

The present invention will be described in detail with reference to the following embodiments in order to fully understand the objects, features and effects of the invention, but the present invention is not limited thereto. The process of the present invention employs conventional methods or apparatus in the art, except as described below.

In a first aspect, the present invention provides a polymer gel, which uses raw materials including a polyacrylamide solution, a cross-linking agent and a crosslinking promoter, and optionally, the raw materials further include a pH adjuster. Wherein the weight ratio of the polyacrylamide solution to the cross-linking agent to the crosslinking promoter is 1 (0.28-0.34) to (0.14-0.3).

In the invention, the concentration of the emulsion type polyacrylamide solution is 9000-15000 ppm, the adopted polyacrylamide (HPAM) has low hydrolysis degree, and the hydrolysis degree is below 10%.

The inventor of the invention discovers through research that when the polymer microspheres used in the oil-stabilizing and water-controlling water of the offshore oilfield in the medium-high water-containing period are prepared, if only the polymer, the cross-linking agent and the cross-linking promoter are used, a phenomenon can occur, namely when the polymer, the cross-linking agent and the cross-linking promoter are mixed together, white insoluble substances can appear quickly once the three are stirred, and the mixture is in a white flocculent state. The inventors have analyzed that the reason why the crosslinking reaction speed is too fast is mainly considered. This can lead to uneven particle strength when the polymer gel is subsequently ground into particles. In order to avoid this, the inventors of the present invention proposed that the polyacrylamide used in the present invention is an emulsion polymer, whereby the crosslinking reaction speed can be retarded to some extent. The emulsion polymer is adopted, so that the dispersion can be directly carried out, curing is not needed, the production space and the operation space of the platform can be reduced, the dispersion effect is good, the dispersion time is short, fish eyes cannot be formed, and the effect is further ensured on the basis of saving manpower and space.

The emulsion type polyacrylamide adopted by the invention can be prepared by a conventional inverse emulsion polymerization method. As a specific example, inverse emulsion polymerization generally comprises the following parts: oil phase, water phase, surfactant and initiator. Wherein the oil phase can be a non-polar solvent insoluble in water, such as benzene, toluene, xylene, white oil, solvent oil, etc.; the water phase is mainly monomer aqueous solution, takes acrylamide as a main body, and other water-soluble monomers are added according to the use requirement, such as: acrylic acid, methacrylic acid, etc.; the surfactant can be used singly or in a plurality of combinations, and the general HLB (hydrophilic-lipophilic balance) value is between 3 and 7; the initiator can be oil soluble or water soluble, and the polymerization can be initiated in various ways, and if thermal initiation is used, the initiator is ammonium persulfate.

The emulsion-type polyacrylamide used in the present invention is composed of acrylamide and acrylic acid, and has a degree of hydrolysis of 10% or less (preferably 3% to 7%, for example, 3%, 4%, 5%, 6%, or 7%), and a molecular weight of 800 to 1400 million (for example, 800 million, 850 million, 900 million, 950 million, 1000 million, 1050 million, 1100 million, 1150 million, 1200 million, 1250 million, 1300 million, 1350 million, or 1400 million). The emulsion-type polyacrylamide used in the invention can be obtained by market purchase, such as Eisen, France, environmental protection science and technology Limited, general industry, Shanghai, and the like.

In the present invention, as mentioned above, the emulsion type polyacrylamide has a low degree of hydrolysis, which is 10% or less, thus ensuring that the cationic polyethyleneimine does not form white flocs when mixed with the phenolic resin crosslinking agent and the emulsion type polyacrylamide having a low degree of hydrolysis. In addition, the oil phase and the surfactant contained in the emulsion polyacrylamide can further enhance the dispersion effect and prevent the generation of floccules. In addition, the emulsion type polyacrylamide with low hydrolysis degree is adopted, so that the final polymer particles are not easily influenced by the mineralization degree, a large amount of temperature-resistant and salt-resistant groups do not need to be added, and the cost is reduced.

In the present invention, the crosslinking agent is a phenolic resin crosslinking agent. The phenolic resin crosslinking agent is commercially available, for example, Binzhou Toutai technology development Co., Ltd, Dongying Jia New Material Co., Ltd, Jinan Dongfeng chemical Co., Ltd, Shanghai Australian industry Co., Ltd, and the like. The invention has no special requirements on the phenolic resin cross-linking agent, and the commercially available phenolic resin cross-linking agent can be applied to the invention. The phenolic resin cross-linking agent can effectively promote cross-linking and realize gelling.

In the present invention, the crosslinking promoter is any one or more of polyethyleneimine, ammonium acetate and ammonium chloride. Preferably, the crosslinking promoter is Polyethyleneimine (PEI).

The inventor of the invention researches the gelling property of different crosslinking promoters on HPAM/phenolic resin crosslinking agent systems (taking the example that the basic composition is 0.9 percent of HPAM (emulsion type) +0.3 percent of phenolic crosslinking agent +0.05 to 0.3 percent of crosslinking promoter). The research shows that the cross-linking promoter comprising both polyphenol and m-phenylenediamine can cross-link the phenolic resin gel system at 50 ℃ and has gel strength less than 10000mPa & s. The inventor analyzes the reason, and thinks that the self-polymerization product generated by the reaction of the polyphenol and the m-phenylenediamine and the phenolic resin cross-linking agent finally reduces the jelly strength because of the reduction of the actual cross-linking groups. In order to improve the gel-forming strength, the inventors have conducted intensive studies on different types of crosslinking promoters, and selected polyethyleneimine, ammonium acetate and ammonium chloride as the crosslinking promoters to be applied to the present invention from among a plurality of crosslinking promoters. Also, preferably, PEI is chosen as the traffic promoter of the present invention.

The crosslinking promoter PEI is a cationic polymer with higher branching degree, contains a large number of primary and secondary amine low-temperature active groups, and the structure of PEI is as follows:

more preferably, the molecular weight of the PEI employed in the present invention is 1200-1800, for example, 1200, 1300, 1400, 1500, 1600, 1700 or 1800, and the like. The inventor finds that compared with PEI with other molecular weight (for example, molecular weight of 1 ten thousand and 7 ten thousand), PEI with molecular weight of 1200-1800 can greatly improve gelling reaction speed and gelling strength of emulsion polyacrylamide and realize better water dispersibility.

Specifically, the PEI crosslinking promoter can promote the low-temperature crosslinking (for example, 50 ℃) of a phenolic resin gel system, and the gel forming strength is up to 20000-50000mPa & s. The crosslinking promoter PEI not only can form a micro-crosslinking structure of a reaction system through the ion adsorption effect of a cation group and anion HPAM of the crosslinking promoter PEI, free aldehyde in the crosslinking agent and hydroxymethyl phenol with low polymerization degree, but also can replace part of amide groups of the HPAM by primary amine and secondary amine with higher activity on a molecular chain, thereby increasing the low-temperature crosslinking reaction activity of the HPAM, promoting the HPAM and the hydroxymethyl phenol of the crosslinking agent to generate covalent crosslinking to form a net frame structure, and finally obviously improving the low-temperature gel forming strength of the phenolic resin gel system.

In the invention, the pH regulator is an optional component and has the main function of enabling the pH value of the gel system to be in a range of 7-8 (weak alkalinity), so the use amount of the pH regulator is subject to the condition that the pH value of the gel system can meet the range of 7-8. The pH value of the gel system is within 7-8, so that the reaction speed can be effectively delayed, and the over-high crosslinking reaction speed is avoided. The pH regulator may be any one or more of oxalic acid, citric acid, sodium carbonate and sodium bicarbonate.

The crosslinking promoter and the pH regulator adopted in the invention can be purchased in the market, and the invention has no special requirement.

The polymer gel of the invention can be prepared by the following method:

(1) dissolving polyacrylamide in water to obtain an emulsion type polyacrylamide solution with the concentration of 9000-15000 ppm; the water can be tap water or oil field reinjection sewage and the like.

(2) And (2) adding a crosslinking agent and a crosslinking promoter into the polyacrylamide solution in sequence according to the proportion, adding a pH regulator to ensure that the pH value is in the range of 7-8, and carrying out gelling reaction at the temperature of 40-65 ℃ under the stirring condition (for example, the rotating speed of 400 r/min) so as to obtain the polymer gel with the viscosity of 1-10 ten thousand mPa & s.

In a second aspect, the present invention provides a particle size, strength-controllable polymer particle. The polymer particles are prepared by in-line grinding of polymer gels.

The polymer particles can be prepared in an online grinding mode, a screening instrument is arranged on equipment, and particles with different particle sizes are screened according to actual stratum conditions, so that the particles injected into an oil well are particles with preset sizes required by actual production, and the particle size and the strength of the polymer particles can be controlled.

The particle size of the polymer particles can be selected from the range of 100 to 300 μm, 2 to 10 μm, or 10 to 30 μm.

As a specific example, in actual production, a first type of microspheres can be produced in-line in a first slug to plug the large channels; then, in the second slug, producing microspheres with a second particle size, producing microspheres with a smaller particle size, and plugging secondary pore canals; in addition, for relatively hypotonic sites, microspheres of a third size are used, which serve as effective motivating. The details are shown in the following table:

type (B)	Initial size (μm)	Final aggregate size (μm)	Adaptation of the formation
				(1)	100～300	1000～3000	8000～15000mD
(2)	10～30	100～200	3000～8000mD
				(3)	2～10	20～80	200～3000mD

The inventor finds that the particle size of the particles is 10-30 mu m, the concentration is 9000-15000 mg/L, and the particle is an optimal formula of a plugging system aiming at the development characteristics (3000-8000 mD) of common large pore canal strata of offshore oil fields.

Examples

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.

The emulsion polyacrylamide used in the following examples was purchased from Shanghai general environmental protection science and technology Co., Ltd, the effective content was 28% -35%, and the molecular weight was 800-1200 ten thousand.

The phenolic resin cross-linking agent adopted in the following embodiments is purchased from Shanghai Australian Kogyo Co., Ltd, the effective content is 3.5-4.5%, and the pH value is 6-9.

The PET used in the following examples is EPOMIN, a product produced by Japan catalyst Co., Ltd, which is a proxy of Han-Luo New materials Co., Ltd, and PEI having product designations SP-012 and SP-018 are used in the following examples 1, 2 and 3, respectively, and the basic information is as follows:

product brand	SP-012, example 1	SP-018, examples 2 and 3
			Molecular weight	1200	1800
Effective content, wt%	＞98	＞98
			Viscosity, mPa.s-25 deg.C	3500-7500	8500-15000

Example 1

The polymer particles of this example were prepared as follows:

(1) adding emulsion polyacrylamide (the hydrolysis degree is 7%) into tap water to prepare a polyacrylamide solution with the mass concentration of 15000 ppm;

(2) sequentially adding the phenolic resin cross-linking agent and the PEI into 100mL of polyacrylamide solution according to the weight ratio of 1:0.28:0.2 of the polyacrylamide solution, mixing, adjusting the pH value of the mixture to be 7-8 by adopting oxalic acid and sodium bicarbonate, uniformly stirring at the rotation speed of 400r/min for 15 minutes at the temperature of 50 ℃, standing at constant temperature for 12 hours, and testing the gel viscosity to be 5 ten thousand mPas.

(3) The gel was milled with a mill to particles having a particle size of 7.6 μm.

Example 2

The polymer particles of this example were prepared as follows:

(1) adding emulsion polyacrylamide (the hydrolysis degree is 6%) into tap water to prepare a polyacrylamide solution with the mass concentration of 9000 ppm;

(2) sequentially adding the phenolic resin cross-linking agent and PEI into 100mL of polyacrylamide solution according to the weight ratio of 1:0.34:0.3 of the polyacrylamide solution, mixing, adjusting the pH value of the mixture to 7-8 by adopting citric acid and sodium bicarbonate, uniformly stirring at 50 ℃ and the rotating speed of 400r/min for 15 minutes, standing at constant temperature for 18 hours, and testing the gel viscosity to be 1 ten thousand mPas.

(3) The gel was milled with a mill to give particles having a particle size of 20 μm.

Example 3

The polymer particles of this example were prepared as follows:

(1) adding emulsion polyacrylamide (the hydrolysis degree is 9%) into tap water to prepare a polyacrylamide solution with the mass concentration of 12000 ppm;

(2) sequentially adding the phenolic resin cross-linking agent and the PEI into 100mL of polyacrylamide solution according to the weight ratio of 1:0.28:0.14 of the polyacrylamide solution, mixing, adjusting the pH value of the mixture to be 7-8 by using oxalic acid, uniformly stirring at 50 ℃ and the rotating speed of 400r/min for 15 minutes, and waiting for 24 hours at constant temperature to obtain the gel with the viscosity of 10 ten thousand mPas.

(3) The gel was milled with a mill to particles having a particle size of 120 μm.

Example 4: effect detection

The test method comprises the following steps:

(1) and preparing injection water.

(2) Preparing a medicament system: the polymer particles (120 μm) of example 3 were prepared to a prescribed concentration (5000mg/L) with water injection, and mixed well with stirring.

(3) Preparing a core displacement experiment: and vacuumizing the rock core to saturate formation water, and calculating the pore volume.

(4) Evaluation of injectability: at 50 ℃, after the water permeability pressure is stable, continuously injecting a 2-4PV system, recording pressure data and calculating a resistance coefficient, wherein the resistance coefficient is injection pressure/water drive injection pressure.

(5) Evaluation of plugging migration: placing the core injected with the 2-4PV polymer particle system for 1 day, performing subsequent water flooding, recording pressure data (injection pressure and pressure of each pressure measuring point) and calculating a residual resistance coefficient; residual drag coefficient-the subsequent water flooding pressure/water flooding injection pressure.

The results are as follows:

1. designing the concentration: under the condition that the speed of the channeling channel is 12.3m/D and on the premise of ensuring the injectability, the optimized result of the blocking rate along with the concentration is shown in figure 1 under the condition that K is 9.3D. The concentration for plugging the high-permeability strip is 4000-6000mg/L by combining the water channeling speed of the production well and considering the influence of factors such as dilution loss.

2. Injectability and blocking: the polymer particles have good injectivity and can smoothly move in the cross flow channel model. Water channeling channel model permeability: 9.3D, the particle size of the colloidal particles for experiments is 7.6 mu m, and the water mineralization is 5900 mg/L. The resistance coefficient (PV number) of the injected particles is 3.57, which shows that the injection pressure is stable, the injection performance is very good, the plugging rate reaches 96.74 percent, and the injection particles have enough plugging capability on water channeling passages. As shown in fig. 2.

3. The polymer particles can be smoothly transported in the cross-flow channel model. In the deep adjustment construction, the dispersed colloidal particles can not form aggregates under the continuous injection condition and can move to the deep part of an oil layer under the push of subsequent fluid.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other substitutions, modifications, combinations, changes, simplifications, etc., which are made without departing from the spirit and principle of the present invention, should be construed as equivalents and included in the protection scope of the present invention.