Composite gel plugging agent

Abstract

The invention relates to a composite gel plugging agent, and belongs to the technical field of oil and gas field plugging agents. When the composite gel plugging agent is used for plugging water, the acrylamide monomer and the polymerization cross-linking agent can form a polymer matrix under the action of the initiator, meanwhile, due to the existence of the solid particles, the composite gel composed of a polymer and the solid particles can be finally formed, the solid particles can improve the strength of the gel, and the water plugging effect is improved. The silane coupling agent is arranged between solid particles and an organic polymer interface, and a binding layer of organic matrix-silane coupling agent-solid particles can be formed, that is, part of active groups of the silane coupling agent can form covalent bonds with the surfaces of the solid particles, and part of active groups of the silane coupling agent can participate in cross-linking, so that the solid particles can be crosslinked. Therefore, the bonding strength and viscoelasticity between the solid particles and the organic polymer are improved, and the viscoelasticity, the expansion coefficient, the strength, the toughness and the temperature resistance of the plugging agent are further improved.

Description

Technical Field

[0001] The present invention relates to a composite gel plugging agent, belonging to the technical field of oil and gas field plugging agents. Background Art

[0002] In order to effectively control the water channeling of dominant water channels such as reservoir fractures or strong water absorption layers, gel plugging agents are often used to plug them, improve the swept volume of water injection, and thus improve the overall water flooding development effect. Using a gel formed by mixing acrylamide monomers, initiators (such as ammonium persulfate or azo compounds), and crosslinking agents and crosslinking underground is a common method for plugging such dominant water channels. However, although the gel used in this method has a certain strength, its toughness is poor and it is easy to break, resulting in premature breakthrough of the injected water.

[0003] In order to improve the strength and toughness of acrylamide-based gel plugging agents, Chinese patent document CN102516431A discloses a macromolecular crosslinking agent for acrylamide gel for water plugging and its preparation method. This patent document mainly starts from the crosslinking agent to improve the strength of acrylamide-based gel plugging agents. Using the new crosslinking agent disclosed in this patent document can improve the toughness and tensile strength of acrylamide-based gel plugging agents, but its temperature resistance is poor, and its compressive strength can only reach about 12 MPa, still unable to meet the use requirements. Chinese patent document CN110628399A discloses a plugging agent for plugging fractures and its plugging method. The plugging agent disclosed in this patent document includes a first component and a second component. The first component includes a first reactive polymer, a polymerization monomer, a crosslinking agent, and an initiator; the second component includes insoluble solid particles and a polymer solution. Using the above plugging agent can not only effectively plug the reservoir fractures, but also the formed three-dimensional network plugging system of organic gel-particles has high plugging strength and erosion resistance. However, the composition of the plugging agent disclosed in this patent document is complex, inconvenient to use, and the formed plugging system has poor toughness, small compressive strength, and is easy to break. Summary of the Invention

[0004] The purpose of the present invention is to provide a composite gel plugging agent, which can solve the problems of small compressive strength and easy breakage existing in current acrylamide-based gel plugging agents.

[0005] In order to achieve the above purpose, the technical solution adopted by the composite gel plugging agent of the present invention is as follows:

[0006] A composite gel plugging agent, comprising an acrylamide monomer, a polymerization crosslinking agent, an initiator, solid particles, a silane coupling agent and water; the mass ratio of the acrylamide monomer, the polymerization crosslinking agent, the solid particles and the silane coupling agent is (13-16):(0.04-0.06):(9-13):(0.1-0.5), and the solid particles are one or any combination of insoluble inorganic particles, insoluble biomass particles and insoluble biomass fibers.

[0007] The composite gel plugging agent of the present invention is a pioneering invention. When the composite gel plugging agent of the present invention is used for water plugging, the acrylamide monomer and the polymerization crosslinking agent can form a polymer matrix under the action of the initiator. At the same time, due to the presence of solid particles, a composite gel composed of a polymer and solid particles can be finally formed (as shown in Figure 1 ). The solid particles can improve the strength of the gel. The silane coupling agent is located between the interface of the solid particles and the organic polymer, and a bonding layer of organic matrix-silane coupling agent-solid particles can be formed. That is, some active groups of the silane coupling agent can form covalent bonds with the surface of the solid particles, and at the same time, some active groups of the silane coupling agent can participate in crosslinking, thereby improving the bonding strength and viscoelasticity between the solid particles and the organic polymer, and further improving the viscoelasticity, expansion coefficient, strength, toughness and temperature resistance of the plugging agent. Therefore, when the gel plugging agent of the present invention is used for water plugging, a composite gel with high strength, toughness and temperature resistance can be formed underground through reaction crosslinking, and then the effect of plugging large pore channels and fractures can be achieved.

[0008] The acrylamide monomers used for the gel plugging agent are all applicable to the present invention. For example, the acrylamide monomer is acrylamide, methacrylamide.

[0009] Preferably, the polymerization crosslinking agent is N,N-alkylenediacrylamide. For example, the polymerization crosslinking agent is N,N-methylenebisacrylamide, N,N-ethylenebisacrylamide, N,N-propylenebisacrylamide. Compared with other types of polymerization crosslinking agents, selecting N,N-alkylenediacrylamide as the polymerization crosslinking agent can further improve the strength and temperature resistance of the plugging agent.

[0010] The type of the initiator can be selected according to the formation temperature and the time required to form the gel. Preferably, the initiator is a persulfate. For example, the persulfate is ammonium persulfate and / or alkali metal persulfate. The alkali metal persulfate is potassium persulfate, sodium persulfate. Compared with other types of initiators, selecting a persulfate initiator has better stability, water solubility and strong oxidizing property.

[0011] To effectively improve the strength and toughness of the gel plugging agent, preferably, the insoluble inorganic particles are selected from one or any combination of bentonite, fly ash, alumina, quartz sand, silica, and cement powder. Preferably, the insoluble biomass particles are wood particles. Preferably, the insoluble biomass fibers are wood fibers. Using the above-mentioned industrial waste residues or forestry waste residues such as insoluble inorganic particles, wood particles, and wood fibers as the filling materials of the plugging agent has the advantages of cheap and easily available raw materials, and at the same time realizes the reuse of resources, reduces the economic cost while ensuring the application effect in the oilfield, meets the requirements of economic and efficient development of the oilfield, and reduces environmental pollution.

[0012] To further improve the stability and strength of the gel plugging agent, preferably, the average particle size of the insoluble inorganic particles is 1 - 5 μm, the average diameter of the insoluble biomass fibers is 1 - 5 μm, and the average length is 1 - 5 μm.

[0013] Preferably, the silane coupling agent is a vinyl silane coupling agent, an amino silane coupling agent, or a mercapto silane coupling agent. Further preferably, the vinyl silane coupling agent is a vinyl trialkoxysilane. For example, the vinyl silane coupling agent is vinyl triethoxysilane, vinyl trimethoxysilane, or vinyl tris(β - methoxyethoxy)silane. Further preferably, the amino silane coupling agent is an aminoalkyl trialkoxysilane. For example, the amino silane coupling agent is γ - aminopropyltriethoxysilane or γ - aminopropyltrimethoxysilane. Further preferably, the mercapto silane coupling agent is a mercaptoalkyl trialkoxysilane. For example, the mercapto silane coupling agent is γ - mercaptopropyltrimethoxysilane or γ - mercaptopropyltriethoxysilane. Compared with other types of silane coupling agents, when vinyl silane coupling agents, amino silane coupling agents, and mercapto silane coupling agents are selected, the vinyl, amino, and mercapto groups in the silane coupling agent can participate in the acrylamide gel reaction to improve the cross - linking degree.

[0014] To increase the service life of the gel plugging agent and prevent the gel plugging agent from gelling prematurely, preferably, the composite gel plugging agent further includes a retarder. Retarders applicable to acrylamide - based gel plugging agents are all applicable to the present invention. For example, the retarder is a ferricyanide. Preferably, the ferricyanide is an alkali metal ferricyanide salt. For example, the ferricyanide is potassium ferricyanide or sodium ferricyanide. Using ferricyanide can better control the gelation time of the plugging agent.

[0015] To ensure that the gel plugging agent has both a relatively fast crosslinking reaction and a relatively long gelation time, preferably, the mass ratio of the acrylamide monomer, polymerization crosslinking agent, initiator, solid particles, silane coupling agent, and retarder is (13 - 16):(0.04 - 0.06):(0.02 - 0.05):(9 - 13):(0.1 - 0.5):(0.01 - 0.02).

[0016] To ensure that the composite gel plugging agent has good fluidity and pumpability and improve the construction effect, preferably, the mass fraction of the acrylamide monomer in the composite gel plugging agent is 13 - 16%. Brief Description of the Drawings

[0017] Figure 1 It is a schematic structural diagram of the composite gel formed by the composite gel plugging agent of the present invention. Detailed Embodiments

[0018] The technical solutions of the present invention will be further described below in conjunction with specific embodiments.

[0019] The gel plugging agents of Examples 1 - 9 are composed of acrylamide, crosslinking agent, initiator, retarder, solid particles, silane coupling agent, and water. The crosslinking agent used in each example is N-N methylene bisacrylamide. The types of initiator, retarder, solid particles, and silane coupling agent used in each example, as well as the mass fractions of acrylamide, N-N methylene bisacrylamide, initiator, retarder, solid particles, and silane coupling agent in each example, are shown in Tables 1 - 2.

[0020] Table 1 Mass fractions of acrylamide, N-N methylene bisacrylamide, initiator, retarder, solid particles, and silane coupling agent in Examples 1 - 5

[0021]

[0022]

[0023] Note: The average particle sizes of bentonite, fly ash, alumina, quartz sand, silica, cement powder, and wood particles in Table 1 are all 1 μm, and the average diameter of wood fibers is 1 μm, and the average length is 1 μm.

[0024] Table 2 Mass fractions of acrylamide, N-N methylene bisacrylamide, initiator, retarder, solid particles, and silane coupling agent in Examples 6 - 9

[0025]

[0026]

[0027] Note: The average particle size of bentonite, fly ash, alumina, quartz sand, silica, cement powder and wood particles in Table 1 is 1 μm, the average diameter of wood fiber is 1 μm, and the average length is 1 μm.

[0028] The preparation methods of the gel plugging agents in Examples 1-9 are as follows: Add the formulated amount of acrylamide to distilled water, stir evenly, then add the formulated amounts of crosslinking agent, initiator, retarder and silane coupling agent, and stir thoroughly until completely dissolved; then add solid particles and stir thoroughly to uniformly disperse the solid particles into the solution to obtain the gel plugging agent.

[0029] Comparative Example 1

[0030] The gel plugging agent of this comparative example was prepared by the following method: Add 13 g of acrylamide to 87 g of distilled water, stir evenly, then add 0.05 g of ammonium persulfate, 0.06 g of N-N methylene bisacrylamide and 0.005 g of potassium ferrocyanide, and stir thoroughly until completely dissolved to obtain the gel plugging agent.

[0031] Comparative Example 2

[0032] The difference between the gel plugging agent of this comparative example and the gel plugging agent of Example 1 is only that the crosslinking agent used in the gel plugging agent of this comparative example is the macromolecular crosslinking agent prepared in Example 2 of Chinese Patent Document CN102516431A. The preparation method of this macromolecular crosslinking agent is as follows: Mix cyclohexane, AM aqueous solution, Span80 and Tween60 to obtain a stable acrylamide inverse microemulsion; add benzoin to the above acrylamide inverse microemulsion and irradiate with ultraviolet light for 4 h to polymerize AM monomers to obtain a polyacrylamide inverse microemulsion; add N-methylol bisacrylamide to the above polyacrylamide inverse microemulsion for chemical modification; precipitate the modified polyacrylamide inverse microemulsion with absolute ethanol, then wash the precipitate with acetone until the color turns white, and vacuum dry for 5 h to obtain a white powder, which is the macromolecular crosslinking agent; among them, the mass fraction of the AM aqueous solution is 40 wt%, and the mass fractions of each component are: cyclohexane 71 wt%, AM aqueous solution 10.2 wt%, Span80 4.8 wt%, Tween60 12.4 wt%, benzoin 0.016 wt%, N-methylol bisacrylamide 1.584 wt%.

[0033] Comparative Example 3

[0034] The difference between the gel plugging agent of this comparative example and the gel plugging agent of Example 1 is only that the silane coupling agent used in the gel plugging agent of this comparative example is G570 (γ-methacryloxypropyltrimethoxysilane).

[0035] Comparative Example 4

[0036] The difference between the gel plugging agent of this comparative example and that of Example 1 is only that the silane coupling agent used in the gel plugging agent of this comparative example is Z6030 (methacrylate-based silane coupling agent).

[0037] Experimental Example

[0038] To evaluate the performance of the gel plugging agents of each example and comparative example, the gel plugging agents of Examples 1-9 and Comparative Examples 1-4 were sealed and placed in an oven at 65 °C or 60 °C, and the gelation time was observed and recorded. Then, the solid gels formed by each gel plugging agent at 65 °C were respectively tested for compressive strength, water absorption expansion coefficient, tensile strength and temperature resistance performance according to the regulations in the enterprise standards Q / SH3135 454-2018 "Technical Requirements for Gel Plugging Agents" and Q / SHCG 99003-2017 "General Test and Evaluation Methods for Oilfield Chemical Agents - Part 3 Chemical Agents for Oil Production". The test results are shown in Table 3. In addition, the experimental results show that the gelation times of the gel plugging agents of Examples 1-2 at 65 °C are 6 h and 8 h respectively, the gelation time of the gel plugging agent of Example 3 at 60 °C is 7 h, and the gelation time of the gel plugging agent of Comparative Example 1 at 65 °C is 6 h.

[0039] Table 3 Compressive strength, water absorption expansion coefficient, tensile strength and temperature resistance performance of the gel plugging agents of each example and comparative example

[0040] Plugging agent Compressive strength / MPa Water absorption expansion coefficient Temperature resistance / °C Tensile strength / kPa Example 1 15 5 100 650 Example 2 17 4 98 630 Example 3 16.3 4 100 645 Example 4 16 5 101 635 Example 5 15.5 6 102 640 Example 6 15 5 99 650 Example 7 16 4 98 638 Example 8 17 4 101 642 Example 9 15 3 96 648 Comparative example 1 10 4 90 60 Comparative example 2 12 4 92 413 Comparative example 3 11 4 90 80 Comparative example 4 12 4 85 100

[0041] As can be seen from Table 3, due to the introduction of solid particles, the solid particles are evenly dispersed in the solution, and the silane coupling agent can connect the solid particles and the organic main agent through chemical bonds, thereby enhancing the strength and toughness of the gel plugging agent. In addition, the addition of solid particles can also improve the expansibility and temperature resistance of the plugging agent.

[0042] To investigate the influence of the size of the solid particles on the experimental results, the gel plugging agent was prepared repeatedly according to the preparation method of any gel plugging agent in Examples 1-9, with the difference that the size of the solid particles was adjusted. When the solid particles were bentonite, fly ash, alumina, quartz sand, silica, cement powder, or wood particles, the average particle size of the solid particles was adjusted from 1 μm to 3 μm or 5 μm. When the solid particles were wood fibers, the average diameter of the wood fibers was adjusted from 1 μm to 3 μm or 5 μm, or the average length of the wood fibers was adjusted from 1 μm to 3 μm or 5 μm. Then, the performance (compressive strength, water absorption expansion coefficient, tensile strength or temperature resistance performance) of the gel plugging agent prepared after adjusting the parameters was tested according to the above method. It was found that the performance of the gel plugging agent prepared after adjusting the parameters differed from that of the gel plugging agent prepared before adjusting the parameters by no more than 3%.

Claims

1. A composite gel plugging agent, characterized in that, It includes acrylamide monomers, polymerization crosslinking agents, initiators, solid particles, silane coupling agents and water; the mass ratio of the acrylamide monomers, polymerization crosslinking agents, solid particles and silane coupling agents is (13 - 16):(0.04 - 0.06):(9 - 13):(0.1 - 0.5), and the solid particles are one or any combination of insoluble inorganic particles, insoluble biomass particles and insoluble biomass fibers.

2. The composite gel plugging agent according to claim 1, characterized in that, The polymerization crosslinking agent is N,N-alkylenebisacrylamide.

3. The composite gel plugging agent according to claim 2, characterized in that, The polymerization crosslinking agents are N,N-methylenebisacrylamide, N,N-ethylenebisacrylamide, N,N-propylenebisacrylamide.

4. The composite gel plugging agent according to claim 1, characterized in that, The insoluble inorganic particles are selected from one or any combination of bentonite, fly ash, alumina, quartz sand, silica, cement powder; the insoluble biomass particles are wood particles; the insoluble biomass fibers are wood fibers.

5. The composite gel plugging agent according to claim 1, characterized in that, The silane coupling agents are vinyl silane coupling agents, amino silane coupling agents, mercapto silane coupling agents.

6. The composite gel plugging agent according to claim 5, characterized in that, The vinyl silane coupling agent is vinyltrialkoxysilane; the amino silane coupling agent is aminoalkyltrialkoxysilane; the mercapto silane coupling agent is mercaptoalkyltrialkoxysilane.

7. The composite gel plugging agent according to claim 6, characterized in that, The vinyl silane coupling agents are vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris(β-methoxyethoxy)silane; the amino silane coupling agents are γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane; the mercapto silane coupling agents are γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane.

8. The composite gel plugging agent according to any one of claims 1-7, characterized in that, The initiator is persulfate.

9. The composite gel plugging agent according to any one of claims 1-7, characterized in that, The composite gel plugging agent further includes a retarder; the retarder is iron cyanide; the iron cyanide is alkali metal iron cyanide salt; the mass ratio of the acrylamide monomers, polymerization crosslinking agents, initiators, solid particles, silane coupling agents and retarder is (13 - 16):(0.04 - 0.06):(0.02 - 0.05):(9 - 13):(0.1 - 0.5):(0.01 - 0.02).

10. The composite gel plugging agent according to any one of claims 1-7, characterized in that, The mass fraction of acrylamide monomers in the composite gel plugging agent is 13 - 16%.

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