Polyanionic cellulose modified delayed expansion plugging agent and preparation method thereof

Abstract

The invention relates to the field of well drilling plugging agents, and particularly discloses a polyanionic cellulose modified delayed expansion plugging agent and a preparation method thereof. The delayed expansion plugging agent is prepared from the following raw materials: water-swellable particles, water and polyanionic cellulose; the preparation system of the water-swellable particles comprises reactants and a solvent, wherein the reactants comprise the following raw materials in percentage by mass: 45-65% of a polymeric monomer containing acylamino, 0.1-0.2% of an initiator, 0.1-0.3% of a cross-linking agent and the balance of an inorganic reinforcing agent; the preparation method comprises the following steps: mixing a polymeric monomer containing an amide group, an initiator, a cross-linking agent and an inorganic reinforcing agent for reaction, and drying and crushing a reaction product to obtain water-swellable particles; the preparation method comprises the following steps: taking water as a binder, spraying the water to the surfaces of the water-swellable particles, then mixing polyanionic cellulose with the wet water-swellable particles, carrying out rolling ball granulation, and sieving to obtain the delayed expansion plugging agent. The delayed expansion plugging agent disclosed by the invention has the advantage of excellent delayed plugging performance.

Description

Technical Field

[0001] The present application relates to the field of drilling plugging agents, and more specifically, to a polyanionic cellulose-modified delayed expansion plugging agent and a preparation method thereof. Background Art

[0002] Lost circulation is the most common drilling accident. Fluctuations in formation pressure can easily form micron- to meter-sized cracks, leading to significant losses and hindering drilling progress. According to statistics, global losses from lost circulation accidents reach billions of dollars annually. Therefore, predicting the location of lost circulation and rapidly addressing it are crucial for reducing drilling costs and are a key topic in the drilling industry.

[0003] Traditional drilling plugging materials include fruit shells, inorganic mineral particles, and bentonite. Due to their simple structures, these plugging agents sometimes do not adapt well to crack sizes and cannot penetrate deep enough to plug leaks. With technological advancements, new water-swelling plugging materials have become a hot topic of research. These plugging materials are compact, making them easy to transport and store. However, they expand significantly after absorbing water, making them highly adaptable to cracks of varying sizes and offering promising application prospects.

[0004] However, most current water-swelling plugging agents absorb and expand too quickly, expanding immediately after being added to the plugging slurry. This makes it difficult to achieve the goal of plugging deep into the cracks before expanding and plugging. Therefore, developing a water-swelling plugging agent with delayed expansion is an urgent problem. Summary of the Invention

[0005] In order to obtain a water-absorbent plugging agent with delayed expansion function, the present application provides a polyanionic cellulose-modified delayed expansion plugging agent and a preparation method thereof.

[0006] In the first aspect, the present application provides a polyanionic cellulose modified delayed expansion plugging agent, which adopts the following technical solution:

[0007] A polyanionic cellulose modified delayed swelling plugging agent, comprising water-swellable particles and a polyanionic cellulose layer coated on the surface of the water-swellable particles;

[0008] The delayed expansion plugging agent comprises the following raw materials in parts by weight: 1 part of water-swellable particles, 0.3-0.6 parts of water, and 0.6-1.2 parts of polyanionic cellulose;

[0009] The preparation system of the water-swellable particles includes reactants and a solvent, wherein the reactants include the following raw materials in the following mass percentages:

[0010] 45-65% of polymer monomers containing amide groups,

[0011] Initiator 0.1-0.2%,

[0012] Cross-linking agent 0.1-0.3%,

[0013] The rest are inorganic reinforcing agents.

[0014] By adopting the above technical solution, the polymer monomer containing an amide group reacts under the action of an initiator, a cross-linking agent and an inorganic reinforcing agent to generate water-swellable particles, and the surface of the water-swellable particles has abundant electropositive amide groups; using water as a binder, under the action of water molecules, the electropositive water-swellable particles and the polyanionic cellulose with electronegative groups undergo electrostatic interaction, and the polyanionic cellulose is adsorbed and coated on the surface of the water-swellable particles, forming a delayed expansion plugging agent with a core-shell structure.

[0015] Polyanionic cellulose has excellent film-forming and water-blocking properties. When the delayed expansion plugging agent enters the cracks and comes into contact with water, the polyanionic cellulose coating layer can form a water-blocking shielding layer, inhibiting water molecules from entering the water-absorbing and swellable particles too quickly; polyanionic cellulose dissolves in water and slowly falls off from the water-absorbing and swellable particles, which can control the water absorption and expansion rate of the water-absorbing and swellable particles to gradually increase, thereby achieving the effect of delayed expansion and plugging.

[0016] The present application controls the mass ratio of water-absorbent swellable particles and polyanionic cellulose so that the time-delaying swellable particles have a good time-delaying effect, and can control the coating thickness of the polyanionic cellulose to achieve controllable time-delaying effect; thereby reducing the possibility of insufficient polyanionic cellulose coating resulting in poor time-delaying effect and difficulty for the plugging agent to penetrate deep into the cracks.

[0017] Preferably, the polymerizable monomer containing an amide group is selected from one or more of acrylamide, methacrylamide, and 2-acrylamido-2-methylpropanesulfonic acid.

[0018] Preferably, the amide group-containing polymerizable monomer is a mixture of any two of acrylamide, methacrylamide, and 2-acrylamido-2-methylpropanesulfonic acid in a mass ratio of 1:1.

[0019] Preferably, the initiator is selected from one or both of sodium sulfite and ammonium persulfate.

[0020] Preferably, the initiator is a mixture of sodium sulfite and ammonium persulfate in a mass ratio of 1:1.

[0021] Preferably, the cross-linking agent is N,N-methylenebisacrylamide.

[0022] Preferably, the inorganic reinforcing agent is selected from one or more of bentonite, kaolin, and ultrafine calcium carbonate.

[0023] Preferably, the degree of polymerization of the polyanionic cellulose is 300-2000.

[0024] By adopting the above technical solution, when the degree of polymerization of the polyanionic cellulose is low, the viscosity of the polyanionic cellulose coating is low. When the time-delay expansion plugging agent enters the water, the polyanionic cellulose coating is easier to fall off from the water-absorbing and swelling particles, thereby obtaining a shorter delay effect; when the degree of polymerization of the polyanionic cellulose is high, the viscosity of the polyanionic cellulose coating is high, thereby making it more difficult for the coating to fall off and obtaining a longer delay effect. Therefore, by controlling the degree of polymerization of the polyanionic cellulose, the delay can be controlled to a certain extent.

[0025] Preferably, the solvent is water, and the mass of the solvent is 2-3 times the total mass of the reactants.

[0026] In a second aspect, the present application provides a method for preparing a polyanionic cellulose-modified delayed expansion plugging agent, which adopts the following technical solution:

[0027] A method for preparing a polyanionic cellulose modified delayed expansion plugging agent comprises the following steps:

[0028] According to the proportion, the polymer monomer containing an amide group, an initiator, a cross-linking agent, an inorganic reinforcing agent, and a solvent are mixed and put into a reaction kettle. In an inert atmosphere, the mixture is stirred and reacted at 4-8°C for 20-40 minutes. The mixture is then heated to 35-50°C and stirred and reacted for 50-80 minutes. The mixture is allowed to stand and the reaction product is separated. The reaction product is dried and crushed to obtain water-swellable particles.

[0029] Water is used as a binder and sprayed onto the surface of water-swellable particles according to a certain ratio. Polyanionic cellulose and the wet water-swellable particles are then mixed to form granules by rolling balls. After screening, a polyanionic cellulose-modified delayed expansion plugging agent is obtained.

[0030] By adopting the above technical solution, the polymer monomer containing an amide group reacts under the action of an initiator, a cross-linking agent and an inorganic reinforcing agent to generate water-absorbing and swellable particles. Water is then used as a binder to electrostatically adsorb the polyanionic cellulose, so that the polyanionic cellulose is coated on the surface of the water-absorbing and swellable particles to form a coating layer with a water-blocking shielding effect, thereby inhibiting water molecules from entering the plugging agent too quickly and achieving a delayed plugging effect.

[0031] Preferably, the preparation method of the polyanionic cellulose modified delayed expansion plugging agent specifically includes:

[0032] 1 part by mass of water-swellable particles is put into a ball rolling machine, 0.1-0.2 parts by mass of water is sprayed into the particles under rolling conditions, and then 0.2-0.4 parts by mass of polyanionic cellulose is added. The steps of spraying water and adding polyanionic cellulose are repeated alternately until the amount of water and polyanionic cellulose reaches the formulated amount, and the product is sieved out to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

[0033] By adopting the above technical solution, polyanionic cellulose can be evenly attached to the surface of the water-swellable particles through multiple small-scale coating, thereby improving the uniformity and coating adequacy of the polyanionic cellulose coating layer and ensuring that the delayed expansion plugging agent has a better delay effect.

[0034] In summary, this application has the following beneficial effects:

[0035] 1. This application uses polyanionic cellulose to coat and modify the water-swellable particles. Polyanionic cellulose has excellent film-forming and water-blocking properties. When the delayed expansion plugging agent enters the cracks and comes into contact with water, the polyanionic cellulose coating can form a water-blocking barrier, inhibiting water molecules from entering the water-swellable particles too quickly. The polyanionic cellulose dissolves in water and slowly falls off the water-swellable particles, controlling the water absorption and expansion rate of the water-swellable particles to gradually increase, thereby achieving the effect of delayed expansion and plugging.

[0036] 2. This application controls the mass ratio of water-swellable particles to polyanionic cellulose, so that the time-delaying swelling particles have a good delay effect. By controlling the coating thickness of the polyanionic cellulose, the delay effect can be controlled. This reduces the possibility that insufficient polyanionic cellulose coating will lead to poor delay effect and the plugging agent will have difficulty penetrating deep into the cracks.

[0037] 3. The method of the present application preferably adopts a method of multiple small-scale coating to enable the polyanionic cellulose to be evenly attached to the surface of the water-swellable particles, thereby improving the uniformity and adequacy of the polyanionic cellulose coating layer and ensuring that the delayed expansion plugging agent has a better delay effect. DETAILED DESCRIPTION

[0038] To further help understand the technical solution of the present invention, the following provides several specific implementation examples to describe the technical solution of the present invention in more detail. All of these described embodiments are only some embodiments of the present invention, not all.

[0039] The following specific embodiments may be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments; and the reaction devices, monomers, compounds, inorganic reinforcing agents, etc. involved in the following embodiments are all commercially available.

[0040] The following specific embodiments may be combined with each other, and the same or similar concepts or processes therein may not be described in detail in some embodiments.

[0041] The following examples are further explanations of the present invention, but the present invention is not limited thereto. Unless otherwise specified in the examples, the percentages are all by mass.

[0042] Example

[0043] Example 1

[0044] This embodiment discloses a polyanionic cellulose modified delayed expansion plugging agent, the preparation method of which is as follows:

[0045] 45 g of acrylamide, 45 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.2 g of initiator, 0.2 g of cross-linking agent, 109.6 g of bentonite, and 500 g of deionized water were placed in a reactor, stirred and reacted at 5° C. for 30 min in a nitrogen atmosphere, then heated to 40° C., stirred and reacted for 60 min, and then allowed to stand for a long time. The product was separated, dried, and crushed into 10 meshes to obtain water-swellable particles;

[0046] 500 g of water-swellable particles were put into a ball rolling machine, 150 g of deionized water was sprayed into the particles under rolling conditions to wet the surface of the water-swellable particles, 300 g of polyanionic cellulose was sprinkled into the particles, and the particles were fully rolled and passed through a 10-mesh sieve to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

[0047] In this embodiment, the initiator is prepared by mixing sodium sulfite and ammonium persulfide in a mass ratio of 1:1, the crosslinking agent is NN methylene bisacrylamide, and the degree of polymerization of the polyanionic cellulose is 300.

[0048] Example 2

[0049] The only difference between this embodiment and embodiment 1 is that the preparation method of the polyanionic cellulose modified delayed expansion plugging agent is as follows:

[0050] 45 g of acrylamide, 45 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.2 g of initiator, 0.2 g of cross-linking agent, 109.6 g of bentonite, and 500 g of deionized water were placed in a reactor, stirred and reacted at 5° C. for 30 min in a nitrogen atmosphere, then heated to 40° C., stirred and reacted for 60 min, and then allowed to stand for a long time. The product was separated, dried, and crushed into 10 meshes to obtain water-swellable particles;

[0051] 500 g of water-swellable particles were placed in a ball rolling machine. 50 g of deionized water was sprayed onto the surface of the water-swellable particles while the particles were rolled. 100 g of polyanionic cellulose with a degree of polymerization of 300 was sprinkled into the particles, and the particles were fully rolled. While keeping the amounts of water and polyanionic cellulose added each time unchanged, deionized water was sprayed and polyanionic cellulose was sprinkled alternately while the particles were rolled. This was repeated three times in total. After fully rolling, the particles were passed through a 10-mesh sieve to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

[0052] Example 3

[0053] The only difference between this embodiment and embodiment 2 is that the preparation method of the polyanionic cellulose modified delayed expansion plugging agent is as follows:

[0054] 45 g of acrylamide, 45 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.2 g of initiator, 0.2 g of cross-linking agent, 109.6 g of bentonite, and 500 g of deionized water were placed in a reactor, stirred and reacted at 5° C. for 30 min in a nitrogen atmosphere, then heated to 40° C., stirred and reacted for 60 min, and then allowed to stand for a long time. The product was separated, dried, and crushed into 10 meshes to obtain water-swellable particles;

[0055] 500 g of water-swellable particles were placed in a ball rolling machine. 50 g of deionized water was sprayed onto the surface of the water-swellable particles while the particles were rolled. 100 g of polyanionic cellulose with a degree of polymerization of 300 was sprinkled into the particles, and the particles were fully rolled. The amount of water and polyanionic cellulose added each time was kept constant, and deionized water was sprayed and polyanionic cellulose was sprinkled alternately while the particles were rolled. This was repeated 5 times in total. The particles were passed through a 10-mesh sieve after full rolling to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

[0056] Example 4

[0057] The only difference between this embodiment and embodiment 2 is that the preparation method of the polyanionic cellulose modified delayed expansion plugging agent is as follows:

[0058] 45 g of acrylamide, 45 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.2 g of initiator, 0.2 g of cross-linking agent, 109.6 g of bentonite, and 500 g of deionized water were placed in a reactor, stirred and reacted at 5° C. for 30 min in a nitrogen atmosphere, then heated to 40° C., stirred and reacted for 60 min, and then allowed to stand for a long time. The product was separated, dried, and crushed into 10 meshes to obtain water-swellable particles;

[0059] 500 g of water-swellable particles were placed in a ball rolling machine. 50 g of deionized water was sprayed onto the surface of the water-swellable particles while the particles were rolled. 100 g of polyanionic cellulose with a degree of polymerization of 300 was sprinkled into the particles, and the particles were fully rolled. The amount of water and polyanionic cellulose added each time was kept constant, and deionized water was sprayed and polyanionic cellulose was sprinkled alternately while the particles were rolled. This was repeated 6 times in total. The particles were passed through a 10-mesh sieve after full rolling to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

[0060] Example 5

[0061] The only difference between this embodiment and embodiment 3 is that the preparation method of the delayed expansion plugging agent modified with polyanionic cellulose is as follows:

[0062] 45 g of acrylamide, 45 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.2 g of initiator, 0.2 g of cross-linking agent, 109.6 g of bentonite, and 500 g of deionized water were placed in a reactor, stirred and reacted at 5° C. for 30 min in a nitrogen atmosphere, then heated to 40° C., stirred and reacted for 60 min, and then allowed to stand for a long time. The product was separated, dried, and crushed into 10 meshes to obtain water-swellable particles;

[0063] 500 g of water-swellable particles were placed in a ball rolling machine. 50 g of deionized water was sprayed onto the surface of the water-swellable particles while the particles were rolled. 100 g of polyanionic cellulose with a degree of polymerization of 500 was sprinkled into the particles, and the particles were fully rolled. The amount of water and polyanionic cellulose added each time was kept constant, and deionized water was sprayed and polyanionic cellulose was sprinkled alternately while the particles were rolled. This was repeated 5 times in total. The particles were passed through a 10-mesh sieve after full rolling to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

[0064] Example 6

[0065] The only difference between this embodiment and embodiment 3 is that the preparation method of the delayed expansion plugging agent modified with polyanionic cellulose is as follows:

[0066] 45 g of acrylamide, 45 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.2 g of initiator, 0.2 g of cross-linking agent, 109.6 g of bentonite, and 500 g of deionized water were placed in a reactor, stirred and reacted at 5° C. for 30 min in a nitrogen atmosphere, then heated to 40° C., stirred and reacted for 60 min, and then allowed to stand for a long time. The product was separated, dried, and crushed into 10 meshes to obtain water-swellable particles;

[0067] 500 g of water-swellable particles were placed in a ball rolling machine. 50 g of deionized water was sprayed onto the surface of the water-swellable particles while the particles were rolled. 100 g of polyanionic cellulose with a degree of polymerization of 1000 was sprinkled into the particles, and the particles were fully rolled. The amount of water and polyanionic cellulose added each time was kept constant, and deionized water was sprayed and polyanionic cellulose was sprinkled alternately while the particles were rolled. This was repeated 5 times in total. The particles were passed through a 10-mesh sieve after full rolling to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

[0068] Example 7

[0069] The only difference between this embodiment and embodiment 3 is that the preparation method of the delayed expansion plugging agent modified with polyanionic cellulose is as follows:

[0070] 45 g of acrylamide, 45 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.2 g of initiator, 0.2 g of cross-linking agent, 109.6 g of bentonite, and 500 g of deionized water were placed in a reactor, stirred and reacted at 5° C. for 30 min in a nitrogen atmosphere, then heated to 40° C., stirred and reacted for 60 min, and then allowed to stand for a long time. The product was separated, dried, and crushed into 10 meshes to obtain water-swellable particles;

[0071] 500 g of water-swellable particles were placed in a ball rolling machine. 50 g of deionized water was sprayed onto the surface of the water-swellable particles while the particles were rolled. 100 g of polyanionic cellulose with a degree of polymerization of 2000 was sprinkled into the particles, and the particles were fully rolled. The amount of water and polyanionic cellulose added each time was kept constant, and deionized water was sprayed and polyanionic cellulose was sprinkled alternately while the particles were rolled. This was repeated 5 times in total. The particles were passed through a 10-mesh sieve after full rolling to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

[0072] Example 8

[0073] The only difference between this embodiment and embodiment 2 is that the preparation method of the polyanionic cellulose modified delayed expansion plugging agent is as follows:

[0074] 55 g of acrylamide, 55 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.3 g of initiator, 0.4 g of cross-linking agent, 89.3 g of bentonite, and 500 g of deionized water were placed in a reactor. The mixture was stirred and reacted at 5° C. for 30 min in a nitrogen atmosphere. The mixture was then heated to 40° C. and stirred and reacted for 60 min. The mixture was then allowed to stand for a long time. The product was separated, dried, and crushed into 10 meshes to obtain water-swellable particles.

[0075] 500 g of water-swellable particles were placed in a ball rolling machine. 50 g of deionized water was sprayed onto the surface of the water-swellable particles while the particles were rolled. 100 g of polyanionic cellulose with a degree of polymerization of 300 was sprinkled into the particles, and the particles were fully rolled. While keeping the amounts of water and polyanionic cellulose added each time unchanged, deionized water was sprayed and polyanionic cellulose was sprinkled alternately while the particles were rolled. This was repeated three times in total. After fully rolling, the particles were passed through a 10-mesh sieve to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

[0076] Example 9

[0077] The only difference between this embodiment and embodiment 2 is that the preparation method of the polyanionic cellulose modified delayed expansion plugging agent is as follows:

[0078] 55 g of acrylamide, 55 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.3 g of initiator, 0.4 g of cross-linking agent, 89.3 g of kaolin, and 500 g of deionized water were placed in a reactor, stirred and reacted at 5° C. for 30 min in a nitrogen atmosphere, then heated to 40° C., stirred and reacted for 60 min, and then allowed to stand for a long time. The product was separated, dried, and crushed into 10 meshes to obtain water-swellable particles;

[0079] 500 g of water-swellable particles were placed in a ball rolling machine. 50 g of deionized water was sprayed onto the surface of the water-swellable particles while the particles were rolled. 100 g of polyanionic cellulose with a degree of polymerization of 500 was sprinkled into the particles, and the particles were fully rolled. While keeping the amounts of water and polyanionic cellulose added each time unchanged, deionized water was sprayed and polyanionic cellulose was sprinkled alternately while the particles were rolled. This was repeated three times in total. After fully rolling, the particles were passed through a 10-mesh sieve to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

[0080] Example 10

[0081] The only difference between this embodiment and embodiment 2 is that the preparation method of the polyanionic cellulose modified delayed expansion plugging agent is as follows:

[0082] 55 g of acrylamide, 55 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.3 g of initiator, 0.4 g of cross-linking agent, 89.3 g of kaolin, and 500 g of deionized water were placed in a reactor, stirred and reacted at 5° C. for 30 min in a nitrogen atmosphere, then heated to 40° C., stirred and reacted for 60 min, and then allowed to stand for a long time. The product was separated, dried, and crushed into 10 meshes to obtain water-swellable particles;

[0083] 500 g of water-swellable particles were placed in a ball rolling machine. 50 g of deionized water was sprayed onto the surface of the water-swellable particles while the particles were rolled. 100 g of polyanionic cellulose with a degree of polymerization of 1000 was sprinkled into the particles, and the particles were fully rolled. While keeping the amounts of water and polyanionic cellulose added each time unchanged, deionized water was sprayed and polyanionic cellulose was sprinkled alternately while the particles were rolled. This was repeated three times in total. After fully rolling, the particles were passed through a 10-mesh sieve to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

[0084] Example 11

[0085] The only difference between this embodiment and embodiment 2 is that the preparation method of the polyanionic cellulose modified delayed expansion plugging agent is as follows:

[0086] 65 g of acrylamide, 65 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.4 g of initiator, 0.6 g of cross-linking agent, 69 g of bentonite, and 500 g of deionized water were placed in a reactor, stirred and reacted at 5° C. for 30 min in a nitrogen atmosphere, then heated to 40° C., stirred and reacted for 60 min, and then allowed to stand for a long time. The product was separated, dried, and crushed into 10 meshes to obtain water-swellable particles;

[0087] 500 g of water-swellable particles were placed in a ball rolling machine. 50 g of deionized water was sprayed onto the surface of the water-swellable particles while the particles were rolled. 100 g of polyanionic cellulose with a degree of polymerization of 1000 was sprinkled into the particles, and the particles were fully rolled. While keeping the amounts of water and polyanionic cellulose added each time unchanged, deionized water was sprayed and polyanionic cellulose was sprinkled alternately while the particles were rolled. This was repeated three times in total. After fully rolling, the particles were passed through a 10-mesh sieve to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

[0088] Example 12

[0089] The only difference between this embodiment and embodiment 2 is that the preparation method of the polyanionic cellulose modified delayed expansion plugging agent is as follows:

[0090] 65 g of acrylamide, 65 g of methacrylamide, 0.4 g of initiator, 0.6 g of cross-linking agent, 69 g of ultrafine calcium carbonate, and 500 g of deionized water were placed in a reactor, stirred and reacted at 5° C. for 30 min in a nitrogen atmosphere, then heated to 40° C., stirred and reacted for 60 min, and then allowed to stand for a long time. The product was separated, dried, and crushed into 10 meshes to obtain water-swellable particles;

[0091] 500 g of water-swellable particles were placed in a ball rolling machine. 50 g of deionized water was sprayed onto the surface of the water-swellable particles while the particles were rolled. 100 g of polyanionic cellulose with a degree of polymerization of 2000 was sprinkled into the particles, and the particles were fully rolled. While keeping the amounts of water and polyanionic cellulose added each time unchanged, deionized water was sprayed and polyanionic cellulose was sprinkled alternately while the particles were rolled. This was repeated three times in total. After fully rolling, the particles were passed through a 10-mesh sieve to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

[0092] Example 13

[0093] The only difference between this embodiment and embodiment 2 is that the preparation method of the polyanionic cellulose modified delayed expansion plugging agent is as follows:

[0094] 65 g of 2-acrylamido-2-methylpropanesulfonic acid, 65 g of methacrylamide, 0.4 g of initiator, 0.6 g of cross-linking agent, 69 g of bentonite, and 500 g of deionized water were placed in a reactor, stirred and reacted at 5° C. for 30 min in a nitrogen atmosphere, then heated to 40° C., stirred and reacted for 60 min, and then allowed to stand for a long time. The product was separated, dried, and crushed into 10 meshes to obtain water-swellable particles;

[0095] 500 g of water-swellable particles were placed in a ball rolling machine. 50 g of deionized water was sprayed onto the surface of the water-swellable particles while the particles were rolled. 100 g of polyanionic cellulose with a degree of polymerization of 2000 was sprinkled into the particles, and the particles were fully rolled. While keeping the amounts of water and polyanionic cellulose added each time unchanged, deionized water was sprayed and polyanionic cellulose was sprinkled alternately while the particles were rolled. This was repeated three times in total. After fully rolling, the particles were passed through a 10-mesh sieve to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

[0096] Example 14

[0097] The only difference between this embodiment and embodiment 2 is that the preparation method of the polyanionic cellulose modified delayed expansion plugging agent is as follows:

[0098] 60 g of acrylamide, 30 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.2 g of initiator, 0.2 g of cross-linking agent, 109.6 g of bentonite, and 500 g of deionized water were placed in a reactor. The mixture was stirred at 5° C. for 30 min in a nitrogen atmosphere. The mixture was then heated to 40° C. and stirred for 60 min. The mixture was then allowed to stand for a long time. The product was separated, dried, and crushed into 10 meshes to obtain water-swellable particles.

[0099] 500 g of water-swellable particles were placed in a ball rolling machine. 50 g of deionized water was sprayed onto the surface of the water-swellable particles while the particles were rolled. 100 g of polyanionic cellulose with a degree of polymerization of 300 was sprinkled into the particles, and the particles were fully rolled. While keeping the amounts of water and polyanionic cellulose added each time unchanged, deionized water was sprayed and polyanionic cellulose was sprinkled alternately while the particles were rolled. This was repeated three times in total. After fully rolling, the particles were passed through a 10-mesh sieve to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

[0100] Example 15

[0101] The only difference between this embodiment and embodiment 13 is that the preparation method of the polyanionic cellulose modified delayed expansion plugging agent is as follows:

[0102] 80 g of 2-acrylamido-2-methylpropanesulfonic acid, 50 g of methacrylamide, 0.4 g of initiator, 0.6 g of cross-linking agent, 69 g of bentonite, and 500 g of deionized water were placed in a reactor, stirred and reacted at 5° C. for 30 min in a nitrogen atmosphere, then heated to 40° C., stirred and reacted for 60 min, and then allowed to stand for a long time. The product was separated, dried, and crushed into 10 meshes to obtain water-swellable particles;

[0103] 500 g of water-swellable particles were placed in a ball rolling machine. 50 g of deionized water was sprayed onto the surface of the water-swellable particles while the particles were rolled. 100 g of polyanionic cellulose with a degree of polymerization of 2000 was sprinkled into the particles, and the particles were fully rolled. While keeping the amounts of water and polyanionic cellulose added each time unchanged, deionized water was sprayed and polyanionic cellulose was sprinkled alternately while the particles were rolled. This was repeated three times in total. After fully rolling, the particles were passed through a 10-mesh sieve to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

[0104] Comparative Example

[0105] Comparative Example 1

[0106] The only difference between this comparative example and Example 1 is that this comparative example discloses a conventional plugging agent, and the preparation method is as follows:

[0107] 45 g of acrylamide, 45 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.2 g of initiator, 0.2 g of cross-linking agent, 109.6 g of bentonite, and 500 g of deionized water were put into a reactor, stirred and reacted at 5°C in a nitrogen atmosphere for 30 minutes, then heated to 40°C, stirred and reacted for 60 minutes, and then allowed to stand fully. The product was separated and dried, and crushed to 10 mesh to obtain a plugging agent.

[0108] In this comparative example, the initiator is prepared by mixing sodium sulfite and ammonium persulfate in a mass ratio of 1:1, and the cross-linking agent is NN methylenebisacrylamide.

[0109] Comparative Example 2

[0110] The only difference between this comparative example and Example 1 is that this application discloses a conventional plugging agent, and the preparation method is as follows:

[0111] 45 g of acrylamide, 45 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.2 g of initiator, 0.2 g of cross-linking agent, 109.6 g of bentonite, 300 g of polyanionic cellulose with a degree of polymerization of 300, and 1600 g of deionized water were put into a reactor. In a nitrogen atmosphere, the mixture was stirred and reacted at 5°C for 30 minutes. The temperature was then raised to 40°C, and the mixture was stirred and reacted for 60 minutes. The mixture was then allowed to stand for a long time. The product was separated, dried, and crushed to 10 mesh to obtain a plugging agent.

[0112] In this comparative example, the initiator is prepared by mixing sodium sulfite and ammonium persulfate in a mass ratio of 1:1, and the cross-linking agent is NN methylenebisacrylamide.

[0113] Comparative Example 3

[0114] The only difference between this comparative example and Example 2 is that the preparation method of the polyanionic cellulose modified delayed expansion plugging agent is as follows:

[0115] 45 g of acrylamide, 45 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.2 g of initiator, 0.2 g of cross-linking agent, 109.6 g of bentonite, and 500 g of deionized water were placed in a reactor, stirred and reacted at 5° C. for 30 min in a nitrogen atmosphere, then heated to 40° C., stirred and reacted for 60 min, and then allowed to stand for a long time. The product was separated, dried, and crushed into 10 meshes to obtain water-swellable particles;

[0116] 500 g of water-swellable particles were placed in a ball rolling machine. 50 g of deionized water was sprayed onto the surface of the water-swellable particles while the particles were rolled. 100 g of polyanionic cellulose with a degree of polymerization of 300 was sprinkled into the particles, and the particles were fully rolled. While keeping the amounts of water and polyanionic cellulose added each time unchanged, deionized water was sprayed and polyanionic cellulose was sprinkled alternately while the particles were rolled. This was repeated twice in total. After fully rolling, the particles were passed through a 10-mesh sieve to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

[0117] Comparative Example 4

[0118] The only difference between this comparative example and Example 2 is that the preparation method of the polyanionic cellulose modified delayed expansion plugging agent is as follows:

[0119] 45 g of acrylamide, 45 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.2 g of initiator, 0.2 g of cross-linking agent, 109.6 g of bentonite, and 500 g of deionized water were placed in a reactor, stirred and reacted at 5° C. for 30 min in a nitrogen atmosphere, then heated to 40° C., stirred and reacted for 60 min, and then allowed to stand for a long time. The product was separated, dried, and crushed into 10 meshes to obtain water-swellable particles;

[0120] 500 g of water-swellable particles were placed in a ball rolling machine. 50 g of deionized water was sprayed onto the surface of the water-swellable particles while the particles were rolled. 100 g of polyanionic cellulose with a degree of polymerization of 300 was sprinkled into the particles, and the particles were fully rolled. The amount of water and polyanionic cellulose added each time was kept constant, and deionized water was sprayed and polyanionic cellulose was sprinkled alternately while the particles were rolled. This was repeated a total of 7 times. After fully rolling, the particles were passed through a 10-mesh sieve to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

[0121] Performance testing

[0122] Test 1: Determination of water absorption and expansion capacity: Take the plugging agent samples of each embodiment and each comparative example and conduct the following test: At 25°C, use a graduated cylinder with an accurate scale to measure a certain volume of water V0, add dry plugging agent, and read the actual water scale volume V in the graduated cylinder. A , then the volume of dry plugging agent particles is V1 (V1=V A -V0). After the mixture expands in a constant temperature water bath at a set temperature for a certain period of time or absorbs water to equilibrium, pour out the remaining water in the measuring cylinder, add the initial clean water volume V0, and read the actual water scale volume V in the measuring cylinder. B At this time, the expansion volume of the plugging agent particles after absorbing water is V2 (V2 = V B =V0), and the value of V2 / V1 is the volume expansion multiple of the plugging agent sample in a certain period of time. The results are summarized in Table 1.

[0123] Test 2: Plugging Performance Test: Using a DLM-01 plugging instrument, the plugging performance of the plugging agents in each Example and Comparative Example was evaluated in accordance with the Chinese Petroleum and Natural Gas Industry Standard "SY / T 5840-2007 Laboratory Test Method for Bridging Plugging Materials for Drilling Fluids." The results are summarized in Table 2.

[0124] Table 1

[0125]

[0126] Table 2

[0127]

[0128] From Examples 1-13 and Comparative Examples 1-2 and Tables 1 and 2, it can be seen that the plugging agent prepared according to the formula and method disclosed in the present application has a good delay effect, a slow water absorption and expansion rate, and excellent plugging performance. It has an obvious plugging effect and can enter deep cracks with the fluid in the plugging slurry, thereby fully reducing liquid leakage.

[0129] In combination with Example 1 and Example 2 and with Tables 1 and 2, it can be seen that the method of spraying water in small amounts multiple times and adding polyanionic cellulose helps to improve the delay effect and plugging performance of the plugging agent. This may be because the repeated addition of small amounts of polyanionic cellulose for coating helps to improve the uniformity of the coating of the water-swellable particles with polyanionic cellulose, making the thickness of the polyanionic cellulose coating layer uniform, reducing the possibility of partial exposure of the water-swellable particles, and helping to stabilize the dissolution and shedding rate of the polyanionic cellulose.

[0130] Combining Examples 2-3, Comparative Examples 3-4, and Tables 1 and 2, it can be seen that the dosage ratio of water-swellable particles to polyanionic cellulose within the scope disclosed in this application can make the plugging agent have excellent delay performance and plugging effect, and the delay effect of the plugging agent can be adjusted by adjusting the thickness of the polyanionic cellulose coating layer, thereby achieving controllable delay. When the amount of polyanionic cellulose is too little, the polyanionic cellulose coating layer is too thin and the delay effect is poor; when the amount of polyanionic cellulose is too much, the delay effect and plugging performance of the plugging agent do not change significantly. This may be because the adsorption load of the water-swellable particles on the polyanionic cellulose reaches the maximum value, the load of the polyanionic cellulose is difficult to continue to increase, and the thickness of the coating layer reaches the limit.

[0131] Combining Example 3, Examples 5-7 and Table 1 and Table 2, it can be seen that when the degree of polymerization increases, the delay performance of the plugging agent is improved to a certain extent. By adjusting the degree of polymerization of polyanionic cellulose, the delay effect of the plugging agent can be controlled.

[0132] In combination with Example 2, Examples 8-13 and Table 1 and Table 2, it can be seen that by adjusting the amount of the reaction system of the water-swellable particles within the scope disclosed in this application, or adjusting the type of the inorganic reinforcing agent or reactive monomer within the scope disclosed in this application, the plugging agent can obtain better delay effect and plugging performance.

[0133] It can be seen from Example 2, Example 8, Example 14, Example 15 and Table 1 and Table 2 that when the mass ratio of the two reaction monomers is 1:1, the plugging agent can obtain better plugging effect and mechanical properties.

[0134] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A polyanionic cellulose modified delayed expansion plugging agent, characterized in that: The invention comprises water-swellable particles and a polyanionic cellulose layer coated on the surface of the water-swellable particles; The delayed expansion plugging agent comprises the following raw materials in parts by weight: 1 part of water-swellable particles, 0.3-0.6 parts of water, and 0.6-1.2 parts of polyanionic cellulose; The preparation system of the water-swellable particles includes reactants and a solvent, wherein the reactants include the following raw materials in the following mass percentages: 45-65% of polymer monomers containing amide groups, Initiator 0.1-0.2%, Cross-linking agent 0.1-0.3%, The rest are inorganic reinforcing agents.

2. The polyanionic cellulose modified delayed expansion plugging agent according to claim 1, characterized in that: The polymerizable monomer containing an amide group is a combination of any two selected from acrylamide, methacrylamide, and 2-acrylamido-2-methylpropanesulfonic acid.

3. The polyanionic cellulose modified delayed expansion plugging agent according to claim 2, characterized in that: The polymerizable monomer containing an amide group is a combination of any two of acrylamide, methacrylamide, and 2-acrylamido-2-methylpropanesulfonic acid in a mass ratio of 1:

1.

4. The polyanionic cellulose modified delayed expansion plugging agent according to claim 1, characterized in that: The initiator is selected from one or both of sodium sulfite and ammonium persulfate.

5. The polyanionic cellulose modified delayed expansion plugging agent according to claim 1, characterized in that: The cross-linking agent is N,N-methylenebisacrylamide.

6. The polyanionic cellulose modified delayed expansion plugging agent according to claim 1, characterized in that: The inorganic reinforcing agent is selected from one or more of bentonite, kaolin, and ultrafine calcium carbonate.

7. The polyanionic cellulose modified delayed expansion plugging agent according to claim 1, characterized in that: The degree of polymerization of the polyanionic cellulose is 300-2000.

8. The polyanionic cellulose modified delayed expansion plugging agent according to claim 1, characterized in that: The solvent is water, and the mass of the solvent is 2-3 times the total mass of the reactants.

9. A method for preparing the delayed expansion plugging agent modified with polyanionic cellulose according to any one of claims 1 to 8, characterized in that: The following steps are involved: According to the proportion, the polymer monomer containing an amide group, an initiator, a cross-linking agent, an inorganic reinforcing agent, and a solvent are mixed and put into a reaction kettle. In an inert atmosphere, the mixture is stirred and reacted at 4-8°C for 20-40 minutes. The mixture is then heated to 35-50°C and stirred and reacted for 50-80 minutes. The mixture is allowed to stand and the reaction product is separated. The reaction product is dried and crushed to obtain water-swellable particles. Water is used as a binder and sprayed onto the surface of water-swellable particles according to a proportion. Polyanionic cellulose and the wet water-swellable particles are mixed to perform ball granulation. After sieving, a polyanionic cellulose-modified delayed expansion plugging agent is obtained.

10. The method for preparing the polyanionic cellulose modified delayed expansion plugging agent according to claim 9, characterized in that: The preparation method of the polyanionic cellulose modified delayed expansion plugging agent specifically comprises: 1 part by mass of water-swellable particles is put into a ball rolling machine, 0.1-0.2 parts by mass of water is sprayed into the particles under rolling conditions, and then 0.2-0.4 parts by mass of polyanionic cellulose is added. The steps of spraying water and adding polyanionic cellulose are repeated alternately until the amount of water and polyanionic cellulose reaches the formulated amount, and the product is sieved out to obtain a polyanionic cellulose-modified delayed expansion plugging agent.

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