CN113429957B

CN113429957B - Polymer particles with controllable granularity and strength and preparation method thereof

Info

Publication number: CN113429957B
Application number: CN202110912309.8A
Authority: CN
Inventors: 李翔; 于萌; 铁磊磊; 鞠野
Original assignee: China Oilfield Services Ltd
Current assignee: China Oilfield Services Ltd
Priority date: 2021-08-10
Filing date: 2021-08-10
Publication date: 2022-12-02
Anticipated expiration: 2041-08-10
Also published as: CN113429957A

Abstract

The invention provides a polymer gel, which is prepared from raw materials comprising 9000-15000 ppm of emulsion type polyacrylamide solution, a cross-linking agent, a crosslinking promoter and optionally a pH regulator; wherein, the weight ratio of the polyacrylamide solution to the cross-linking agent to the cross-linking 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.

Description

Polymer particles with controllable granularity and strength and preparation method thereof

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 invention patent application with the application number of 201410435856.1 discloses a temperature-resistant and salt-resistant HPAM/Cr ³⁺ 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 made from raw materials comprising an emulsion polyacrylamide solution at a concentration of 9000-15000 ppm, a cross-linking agent, a cross-linking promoter, and optionally a pH adjusting agent;

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

Preferably, the polyacrylamide has a degree of hydrolysis of no more than 10%.

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

Preferably, the crosslinking promoter is any one or more of polyethyleneimine, ammonium acetate and ammonium chloride with a 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 cross-linking promoter into the polyacrylamide solution according to a ratio, and stirring to generate a gel reaction.

Preferably, in step (2), the gelling reaction takes place at a pH of from 7 to 8 and at a temperature of from 40 ℃ to 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 polymer particles have a particle size of 100 to 300. Mu.m, 2 to 10 μm or 10 to 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 plugging rate in the effect test performed in example 4 as a function of 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 conducted in 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 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, wherein the polymer gel uses raw materials including a polyacrylamide solution, a cross-linking agent and a cross-linking promoter, and optionally, the raw materials further include a pH regulator. Wherein, the weight ratio of the polyacrylamide solution, the cross-linking agent and the crosslinking promoter is 1 (0.28-0.34) to (0.14-0.3).

In the present invention, the concentration of the emulsion type polyacrylamide solution is 9000 to 15000ppm, and the adopted polyacrylamide (HPAM) has a low degree of hydrolysis, and the degree of hydrolysis is 10% or less.

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, acrylamide is taken 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 value (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 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, tokyo Toutai technology development Co., ltd., dongxing Jia New Material Co., ltd., jinan Dongfeng chemical industry Co., ltd., shanghai Macao Industrial 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 inventors of the present invention have studied the gelling properties of different types of crosslinking promoters for HPAM/phenolic resin crosslinking agent systems (taking the basic composition of 0.9% HPAM (emulsion type) +0.3% phenolic crosslinking agent + 0.05-0.3% crosslinking promoter as an example). 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 from 1200 to 1800, e.g., 1200, 1300, 1400, 1500, 1600, 1700 or 1800, etc. The inventors have found through studies that the gelling reaction rate and gelling strength of emulsion-type polyacrylamide can be greatly improved and better water dispersibility can be achieved with PEI having a molecular weight of 1200 to 1800, as compared to PEI having other molecular weights (e.g., molecular weights of 1 ten thousand and 7 ten thousand).

Specifically, the PEI crosslinking promoter can promote the low-temperature crosslinking (such as 50 ℃) of a phenolic resin gel system, and the gel forming strength is as high as 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 mainly has the function of ensuring that the pH value of a gel system is in a range of 7-8 (weak alkalinity), so the use amount of the pH regulator is based on the condition that the pH value of the gel system can meet the pH value of 7-8. The pH value of the gel system is in the range of 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 requirements.

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.

(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 under the stirring condition (for example, the rotating speed of 400 r/min) at the temperature of 40-65 ℃ to obtain the polymer gel with the viscosity of 1-10 ten thousand mPa & s.

In a second aspect, the present invention provides a polymer particle having a controllable size and strength. 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 may be selected in the range of 100 to 300. Mu.m, 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 macropores; 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:

types of	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 aiming at the development characteristics (3000-8000 mD) of common large pore canal stratum of offshore oil field, the particle size is 10-30 mu m, the concentration is 9000-15000 mg/L, and the plugging agent is a preferable formula of a plugging system.

Examples

The invention is further illustrated by the following examples, which are not intended to limit the invention thereto. Experimental procedures without specifying specific conditions in the following examples were selected in accordance with conventional procedures and conditions, or in accordance with commercial instructions.

The emulsion polyacrylamide used in the following examples was purchased from environmental protection technologies, inc., exemplary Shanghai, having an effective content of 28-35% and a molecular weight of 800-1200 ten thousand.

The phenolic resin cross-linking agent adopted in the following examples 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) Adding a phenolic resin cross-linking agent and PEI into 100mL of polyacrylamide solution according to the weight ratio of 1: 0.28.

(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) Adding a phenolic resin cross-linking agent and PEI into 100mL of polyacrylamide solution according to the weight ratio of 1.

(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) Adding a phenolic resin cross-linking agent and PEI into 100mL of polyacrylamide solution in a weight ratio of 1.

(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 (5000 mg/L) with injection of water, and mixed well with stirring.

(3) Preparation of 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 stabilizes, the 2-4PV system is continuously injected, pressure data is recorded and the drag coefficient is calculated, drag coefficient = 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 = subsequent water drive pressure/water drive injection pressure.

The results were as follows:

1. designing the concentration: under the condition that the speed of the channeling channel is 12.3m/D and the injection performance is guaranteed, the optimization result of the blocking rate along with the concentration is shown in figure 1 under the condition that K = 9.3D. The concentration for plugging the high-permeability strip is 4000-6000mg/L by combining the water channeling speed of a production well and considering the influences of factors such as dilution loss and the like.

2. Injectability and plugging: 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 5900mg/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-adjusting construction, the dispersed colloidal particles can not form aggregates under the continuous injection condition and can be moved 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.

Claims

1. A polymer gel, characterized in that the polymer gel is made from raw materials comprising a polyacrylamide solution with a concentration of 9000-15000 ppm, a cross-linking agent and a cross-linking promoter, and optionally a pH adjusting agent;

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;

wherein the degree of hydrolysis of the polyacrylamide is no more than 10%;

wherein the crosslinking promoter is polyethyleneimine with the molecular weight of 1200-1800.

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

3. 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.

4. A method of preparing a polymer gel according to any one of claims 1 to 3, comprising:

5. The process according to claim 4, wherein in step (2), the gelling reaction occurs at a pH of 7 to 8 and a temperature of 40 ℃ to 65 ℃.

6. A polymer particle of controllable size and strength, which is prepared by in-line grinding of a polymer gel according to any one of claims 1 to 3.

7. The particle-size, strength-controllable polymer particles of claim 6, wherein the polymer particles have a particle size of 100 to 300 μm, 2 to 10 μm, or 10 to 30 μm.