Nano composite material blocking agent as well as preparation method and application thereof

Abstract

The invention provides a nano composite material blocking agent as well as a preparation method and application thereof. The blocking agent comprises the following components: an inorganic layered material, a polymer monomer, an auxiliary agent system of the polymer monomer and a free radical initiator. The nano composite material blocking agent is prepared by the following steps: forming a mixed system by an inorganic layered material, a polymer monomer and an auxiliary agent system thereof, initiating an in-situ polymerization reaction by a free radical initiator, and compounding. The plugging agent has good self-expansion performance and can effectively plug a loose sandstone hydrocarbon reservoir and prevent the hydrocarbon reservoir from being damaged; the nano-composite plugging agent has high mechanical strength, high-temperature and high-pressure viscoelastic deformability and plugging strength, and can generate a high-temperature and high-pressure resistant plugging effect in drilling engineering under deep and ultra-deep environmental conditions; compared with the prior art, the preparation method has the advantages that the nano-structure reinforced phase is adopted, the controllable high-sphericity, high-expansion-degree and high-temperature-resistant multifunctional nano-composite microspheres are designed, and the preparation method is simple, easy to implement, low in cost and high in efficiency.

Description

Technical Field

[0001] This invention relates to the field of sealing technology for fluid leakage and cross-contamination in petroleum engineering, and more specifically, to a nanocomposite sealing agent, its preparation method, and its application. Background Technology

[0002] Fluid loss and leakage in existing oil and gas projects are common problems. Current technologies employ various sealing agents and plugging techniques to temporarily resolve leakage or leakage issues based on the leakage or leakage situation in drilling, fracturing, cementing, and other projects. However, these methods typically do not consider the continued existence of leakage problems during subsequent well production, leading to repeated leakage control and reduced production efficiency in oil and gas extraction.

[0003] Existing technologies also employ micron- and millimeter-scale macroscopic plugging agents to address on-site leakage or cross-flow problems. Because these particles are difficult to penetrate the micropores and fissures of deep, low-permeability reservoirs, they primarily accumulate on the outer surfaces of these micropores and fissures, temporarily sealing leakage or cross-flow. However, this temporary plugging is prone to failure as oil and gas well projects extend, increasing the movement resistance of engineering equipment and potentially leading to wellbore instability. Furthermore, existing plugging technologies for deep oil and gas exploration and development projects represent a global challenge and a critical problem that my country's oil and gas engineering sector particularly needs to address.

[0004] In deep oil and gas engineering, existing technologies use macroscopic plugging agents at the micron and millimeter scale. Under the high temperature and pressure of deep wells, these plugging agents deform and enter the small pores and fractures of the reservoir, producing a relative sealing effect. However, as the engineering cycle extends, these plugging agent particles degrade, leading to the failure of sealing and plugging of the entire reservoir, especially the small pores and fractures.

[0005] Existing technologies target deep, high-temperature, and high-pressure conditions, studying the sealing characteristics of simulated particulate plugging agents and the viscoelastic penetration behavior of their compositions into the micropores and fissures of reservoirs. Through a highly active nanoparticle system, gap-filling, strong adsorption, and composite effects are generated on the walls of micropores and fissures, significantly increasing the resistance to fracture slippage. This also creates a tightly connected, integrated compaction effect on small-scale pores and fissures in the underground reservoir, bringing the permeability of micropores and fissures close to zero, thereby blocking the migration of gas molecules in the micropore and fissure channels or creating a barrier-like sealing effect.

[0006] Among the various plugging materials in the prior art, polymer microspheres and microscale silica-reinforced microspheres possess properties such as controllable size, viscoelasticity, deformability, and water absorption (see Tang X, Yang H, Gao Y, et al. Preparation of a micron-size silica-reinforced polymer microsphere and evaluation of its properties as a plugging agent. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2018, 547: 8-18.). However, the aforementioned polymer microspheres exhibit poor mechanical properties, heat resistance, and salt resistance, while the microscale silica-reinforced microspheres have poor chemical bonding strength. These microsphere systems have limitations in applications involving high temperature, high shear, and complex channel environments. Summary of the Invention

[0007] In view of this, the present invention proposes a nanocomposite sealing agent, comprising the following components: inorganic layered material, polymer monomer and its auxiliary agent system, and free radical initiator.

[0008] Furthermore, the inorganic layered material is at least one of bentonite, diatomite, lithium saponite, sepiolite, or montmorillonite.

[0009] Furthermore, the polymer monomer is at least two of acrylamide (AM), acryloylmorpholine, acrylic acid (AA), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS).

[0010] Furthermore, the polymer monomer auxiliary system is an emulsion suspension reaction system formed by dispersing an emulsifier in an organic solvent, wherein the emulsifier is at least one of Span-80, industrial Tween-60, and industrial polymeric alcohol.

[0011] Furthermore, the free radical initiator includes an initiator and a crosslinking agent; the initiator is at least one selected from persulfate, sodium bisulfite, sodium sulfite, and diisobutyronitrile peroxide; the crosslinking agent is N,N-methylenebisacrylamide.

[0012] Furthermore, the inorganic layered material is pretreated with an organic intercalating agent; the organic intercalating agent is at least one of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate.

[0013] Furthermore, after pretreatment, the interlayer spacing of the inorganic layered material is greater than or equal to 1.90 nm.

[0014] A second aspect of the present invention provides a method for preparing a nanocomposite sealing agent, comprising the following steps:

[0015] Step 1: Pretreatment of inorganic layered materials. Add deionized water to fully swell to obtain a suspension. Adjust the pH value of the suspension, then add an intercalating agent and stir evenly. Heat the mixture to react and obtain the pretreated inorganic layered materials.

[0016] Step 2: Prepare the polymer monomer and auxiliary agent system, prepare the emulsion suspension reaction system, then prepare the monomer polymer aqueous phase system, and mix the two together;

[0017] Step 3: Prepare the blocking agent by adding the treated inorganic layered material to the monomer polymer and its additive system, stirring thoroughly and adjusting the pH value, and then adding a free radical initiator to initiate the reaction product.

[0018] Furthermore, the interlayer spacing of the pretreated inorganic layered material is greater than or equal to 1.90 nm.

[0019] The present invention provides a nanocomposite plugging agent with the following beneficial technical effects: This plugging agent is prepared by an in-situ polymerization reaction and composite method using inorganic layered materials, polymer monomers, and their additives, initiated by free radicals. It possesses excellent self-expansion properties and can effectively plug loose sandstone oil and gas reservoirs, preventing damage to the reservoirs. The nanocomposite plugging agent exhibits high mechanical strength, high-temperature and high-pressure viscoelastic deformation, and plugging strength, enabling it to produce a high-temperature and high-pressure resistant plugging effect in deep and ultra-deep drilling environments. Compared with existing technologies, the present invention uses a nanostructured reinforcing phase to design controllable high sphericity, expansion, and high-temperature resistant multifunctional nanocomposite microspheres, offering simplicity, low cost, and high efficiency.

[0020] The third aspect of the present invention proposes the application of a nanocomposite material plugging agent, which is used in the process of plugging leaks or blocking oil, gas and water leakage in deep oil and gas engineering.

[0021] Furthermore, the nanocomposite sealing agent, in combination with layered silicates, is used in deep oil and gas engineering for plugging leaks or as a barrier sealing process to prevent oil, gas and water leakage.

[0022] The present invention provides an application of a nanocomposite sealing agent that solves the problems of poor mechanical properties, poor heat resistance, poor salt resistance, and poor chemical bonding strength of the polymer microspheres used in the past, and overcomes the limitations of previous applications in high temperature, high shear and complex channel environments. Attached Figure Description

[0023] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0024] Figure 1 Table 1 shows the thermogravimetric loss characteristics of the intercalation reaction modified layered silicate in this invention.

[0025] Figure 2 Table 2 shows the particle size and water absorption swelling properties of the nanocomposite sealing agent in this invention;

[0026] Figure 3 Table 3 shows the thermogravimetric loss characteristics of the nanocomposite sealing agent in this invention;

[0027] Figure 4 Table 4 shows the 20-hour continuous water absorption and swelling rate of the nanocomposite sealing agent in this invention.

[0028] Figure 5 Table 5 shows the sealing characteristics of the nanocomposite sealing agent in this invention;

[0029] Figure 6 This is a SEM image of the surface morphology of the nanocomposite microsphere plugging agent and the exfoliation morphology of PAAA / 0.5% O-Mt microspheres in this invention;

[0030] Figure 7 This is a diagram showing the core sealing characteristics of the nanocomposite microsphere plugging agent in this invention. Detailed Implementation

[0031] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] The nanocomposite sealing agent disclosed in this invention is a mixture of inorganic layered materials, polymer monomers and their additives, which is prepared by in-situ polymerization reaction initiated by a free radical initiator and a composite method.

[0033] The preparation method of the nanocomposite sealing agent is carried out according to the following process:

[0034] Step 1: Pretreatment of inorganic layered materials. Add deionized water to fully swell to obtain a suspension. Adjust the pH value of the suspension, then add an intercalating agent and stir evenly. Heat the mixture to react and obtain the pretreated inorganic layered materials.

[0035] Step 2: Prepare the polymer monomer and auxiliary agent system, prepare the emulsion suspension reaction system, then prepare the monomer polymer aqueous phase system, and mix the two together;

[0036] Step 3: Prepare the blocking agent by adding the treated inorganic layered material to the monomer polymer and its additive system, stirring thoroughly and adjusting the pH value, and then adding a free radical initiator to initiate the reaction product.

[0037] The inorganic layered material used, after pretreatment with an intercalating agent, has an interlayer spacing of not less than 1.90 nm. It is combined with the multi-component polymer monomers to form a 60% concentration emulsion suspension system, and then mixed with a 0.5-2.0% concentration initiator and a 1.0-3.0% concentration crosslinking agent system to form a homogeneous reaction system. Then, a polymerization reaction and composite process are initiated at room temperature to obtain the aforementioned nanocomposite sealing agent.

[0038] The inorganic layered material is an inorganic layered material product, such as at least one of bentonite, diatomite, lithium saponite, sepiolite, or montmorillonite (or montmorillonite), which has a common crystal layer structure and different ordered stacking morphologies of crystal layers; preferably, the inorganic layered material is a mixture of the above-listed materials.

[0039] The inorganic layered material uses an organic surface treatment agent or an organic intercalating agent, which is an organic molecule with surface activity. In this embodiment, industrial sodium dodecyl sulfate or sodium dodecylbenzene sulfonate is used as the surface active molecule. Preferably, a mixture of the two is used to treat the inorganic layered material to improve its performance.

[0040] In the preparation method of the nanocomposite sealing agent, the emulsion suspension reaction system is formed by mixing according to the mass ratio. The emulsion suspension reaction system is an oil phase emulsion suspension system formed by dispersing the emulsifier in solvents such as cyclohexane, pentane, and industrial white oil. Preferably, an oil phase emulsion suspension system in which several solvents are mixed arbitrarily is selected.

[0041] The emulsion suspension reaction system is selected from industrial emulsifiers such as Span-80, Tween-60, and industrial polymeric alcohols; preferably, it is an arbitrary mixture of several industrial emulsifiers, dispersed in the oil phase, and formed into an emulsion suspension by mechanical stirring and shearing, and then mixed with industrial monomers, which are selected from acrylamide (AM), acryloylmorpholine, acrylic acid (AA), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS); preferably, two or more of the industrial monomers are selected to form a comonomer, which is fully dispersed and mixed in deionized water and the pH of the mixture is adjusted to neutral to form the emulsion suspension reaction system.

[0042] In the emulsion suspension reaction system, a polymerization reaction is initiated using a ternary or higher copolymer monomer and an initiator; the initiator is selected from persulfate, sodium bisulfite, sodium sulfite, and diisobutyronitrile peroxide; preferably, a mixture of the initiators is used, and the reaction is carried out under controlled temperature conditions starting from room temperature.

[0043] This embodiment discloses a method for preparing a nanocomposite sealing agent, comprising the following synthesis process:

[0044] First, Na-Mt was added to deionized water and allowed to swell completely to obtain a Na-Mt suspension. The pH of the suspension was adjusted with HCl solution. Simultaneously, sodium dodecyl sulfonate (SLS), with an industrial Na-Mt cation exchange capacity, was added to deionized water and stirred to dissolve into a homogeneous aqueous solution. The SLS aqueous solution was then slowly added to the Na-Mt suspension and stirred until homogenized. The water bath temperature was slowly increased, and the reaction was carried out under a N2 atmosphere. After post-treatment and drying and pulverization, a powder sample was obtained.

[0045] Secondly, the oil phase system is prepared; the emulsifier Span-80 is dispersed in the organic solvent cyclohexane (CYH) and dissolved to form an oil phase emulsion dispersion system, which is then transferred to a reactor equipped with a reflux condenser and placed in a digital display constant temperature water bath.

[0046] Next, the aqueous phase system was prepared. Acrylamide (AM), acrylic acid (AA), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) monomers were sequentially added to deionized water and stirred to fully disperse them, forming an aqueous phase dispersion system. N,N-methylenebisacrylamide (MBA) monomer was then added under stirring, and the mixture was stirred to further disperse it, forming an aqueous phase reaction system. The mixture was then stirred until homogeneous and transferred to an oil phase dispersion system. The stirring speed was adjusted while reflux was applied, and nitrogen gas was introduced into the reactor to remove oxygen. Then, potassium persulfate (KPS) initiator was weighed and slowly added to the reaction system in the reactor. The stirring speed was adjusted to control the water bath temperature, and the reaction continued, resulting in a copolymer suspension product. This product was then demulsified and precipitated, vacuum filtered, dried in a forced-air oven, and ground to obtain PAAA material powder particles.

[0047] Finally, using the oil-phase system and aqueous-phase system for preparing PAAA, the modified montmorillonite (O-Mt) of the specified mass fraction was added, followed by deionized water. The mixture was stirred thoroughly to form an aqueous dispersion system with a pH of 6-7. N,N-methylenebisacrylamide (MBA) was then added to the oil-phase dispersion system to form a uniformly mixed reaction system. After reflux, nitrogen purging, and uniform mixing, an appropriate amount of potassium persulfate (KPS) was added to initiate the reaction and obtain the product. After demulsification and precipitation with anhydrous ethanol, the product was dried and ground to obtain the nanocomposite powder sample PAAA / O-Mt.

[0048] The nanocomposite sealing agent obtained by the above method can be used alone for leak plugging in deep oil and gas engineering or for barrier sealing processes that block oil, gas and water leakage; preferably, the nanocomposite sealing agent microsphere particles, in combination with layered silicates, are used for leak plugging in deep oil and gas engineering or for barrier sealing processes that block oil, gas and water leakage.

[0049] The following specific examples and comparative examples are used to test the sealing performance of a nanocomposite sealing agent obtained by the above method.

[0050] Example 1

[0051] The procedure for reacting sodium dodecyl sulfonate (SLS) with layered silicate montmorillonite (Na-Mt) is as follows:

[0052] First, 2.5 g of Na-Mt was added to deionized water and allowed to swell completely to obtain a Na-Mt suspension. The pH of the suspension was adjusted to 1.0 using 2 mol / L HCl solution. Simultaneously, sodium dodecyl sulfate (SLS) equivalent to 1.0 times the cation exchange capacity of industrial Na-Mt was weighed and added to 25 mL of deionized water and stirred to dissolve into a homogeneous aqueous solution. The SLS aqueous solution was then slowly added to the Na-Mt suspension and stirred until homogenized. The stirring speed was then adjusted to 400 r / min, and the water bath temperature was slowly increased to 80 °C. After reacting for 8 hours under a N2 atmosphere, the reaction solution was neutralized with 1 mol / L NaOH solution to bring the pH to 7.0. Finally, the product was washed, filtered, dried, and aged overnight. The resulting product was then washed three times with deionized water. The washing product was then dried in a forced-air oven at 70°C for 36 hours. The dried sample was then pulverized, ground, and sieved through a 200-mesh (74 μm) sieve to obtain a powder sample, designated as the O-Mt sample. The thermogravimetric characteristics of this sample were tested using the TGA-DTG method. (See [reference needed]). Figure 1-4 The corresponding tables 1-4 show that the interlayer spacing of the XRD-tested interlayer structure is 1.90 nm.

[0053] Comparative Example 1

[0054] A mechanical mixture of sodium dodecyl sulfonate (SLS) and layered silicate montmorillonite (Na-Mt).

[0055] Comparative Example 2

[0056] Preparation method of PAAA copolymer plugging agent:

[0057] (1) Weigh 1.6g of emulsifier Span-80 and disperse it in 110mL of organic solvent cyclohexane (CYH) and stir for 1 hour to dissolve it, forming an oil phase emulsion dispersion system. Then transfer it to a 250mL reactor equipped with a reflux condenser and place it in a digital display constant temperature water bath.

[0058] (2) Weigh 6.0 g of acrylamide (AM), 5.92 g of acrylic acid (AA), and 0.83 g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) monomer, and add them sequentially to 21 mL of deionized water. Stir for 30 minutes to fully disperse and form an aqueous dispersion system. Then neutralize the pH of the aqueous dispersion system to 6-7 with NaOH solution. Add 0.29 g of N,N-methylenebisacryloylMBA monomer while stirring, and continue stirring for 1 hour to fully disperse it.

[0059] (3) After the aqueous dispersion system prepared in (2) is continuously stirred and homogenized, it is transferred to the oil dispersion system in (1). The stirring speed is adjusted to 300 r / min, and the reflux is condensed. Nitrogen gas is introduced into the reactor for deoxygenation for 30 minutes. Then, 0.25 g of potassium persulfate (KPS) initiator is weighed and slowly added to the reaction system in the above reactor. The stirring speed is adjusted to 420 r / min, and the water bath temperature is controlled to rise to 65°C. After the reaction is continued for 6 hours, a copolymer suspension product is obtained. Anhydrous ethanol is added to the polymer suspension for demulsification and precipitation. The product is vacuum filtered and placed in a forced-air oven at 50°C for 36 hours. The dried sample is ground and sieved through a 200-mesh (74 μm) sieve to obtain a powder sample, denoted as PAAA. The thermogravimetric loss characteristics of the obtained sample are tested by the TGA-DTG method, as shown in Tables 1-4.

[0060] Example 2

[0061] Method for preparing PAAA / O-Mt copolymer nanocomposite plugging agent:

[0062] (1) An oil-phase emulsion dispersion system was prepared by following the method of comparative examples;

[0063] (2) Weigh 6.0g of acrylamide (AM), 5.92g of acrylic acid (AA), and 0.83g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) monomer, and 0.064g of reaction-modified montmorillonite (O-Mt), and add them sequentially to 26mL of deionized water. Stir for 30 minutes to fully disperse and form an aqueous dispersion system. Then neutralize the pH of the aqueous dispersion system to 6-7 with NaOH solution. Add 0.29g of N,N-methylenebisacryloylMBA monomer while stirring, and continue stirring for 1 hour to fully disperse it.

[0064] (3) Then, after the aqueous dispersion system is stirred evenly, it is poured into the oil dispersion system to form a uniformly mixed reaction system. After reflux and nitrogen deoxygenation for 30 minutes, an appropriate amount of potassium persulfate (KPS) is added to the uniformly mixed reaction system, the rotation speed is adjusted to 420 r / min, and the reaction is carried out at 65℃ for 6 hours. Then, anhydrous ethanol is added to the resulting reaction product suspension for demulsification and precipitation, followed by filtration. The filtered product is placed in a forced-air drying oven and dried at 50℃ for 36 hours. The dried sample is then crushed, ground, and sieved through a 200-mesh (74 μm) sieve to obtain a powder sample, denoted as PAAA / 0.5% O-Mt. The thermogravimetric loss characteristics of the obtained sample are tested using the TGA-DTG method, and the interlayer spacing of the interlayer structure is tested by XRD. See Appendix. Figure 1-4 The corresponding table is 1-4.

[0065] Examples 3-6

[0066] (1) Following the steps of Example 2, a polymer nanocomposite sealing agent was prepared, the only difference being that the mass ratio of the added amount of reaction-modified montmorillonite (O-Mt) to the comonomer was controlled to be 1.0%, 1.5%, 2.0% and 2.0%, respectively.

[0067] The thermogravimetric loss characteristics of the prepared samples were tested using the TGA-DTG method, and the interlayer spacing of the interlayer structure was tested using XRD. (See attached figure) Figure 1-4 The corresponding tables 1-4; surface and exfoliation morphology of the nanocomposite microsphere plugging agent, refer to... Figure 6 As shown.

[0068] (2) The procedure for evaluating the swelling properties of polymer nanocomposite plugging agents is as follows.

[0069] First, weigh 0.2g of the dried powder sample from Examples 3-6 and place it in a dry cloth bag that can hold 1g of tea leaves. Then, immerse the sample bag in a beaker containing 20mL of deionized water or 100mL of salt solution and seal it. Transfer the beaker to a digital display constant temperature water bath and adjust the temperature to allow the sample to swell at 30°C for a certain period of time until equilibrium is reached. After swelling saturation and completion, remove the entire cloth bag from the water or salt solution and hang it to remove excess liquid, then weigh it again. Repeat the above steps three times for each sample experiment, and take the average of the three experimental results to calculate the water absorption swelling rate Pr of the powder sample as follows:

[0070] P r =(m t -m0) / m (1)

[0071] In the formula, m t m0 and m0 represent the mass of the bag before and after swelling at the same humidity, respectively, and m represents the mass of the dried sample powder.

[0072] The swelling rate of the polymer nanocomposite sealing agent increased rapidly after 24 hours of water absorption, and gradually increased after 60 hours. The swelling rate of the nanocomposite material was lower than that of the pure polymer material, and the swelling rate decreased with increasing O-Mt content. (See Appendix) Figure 1-5 The corresponding tables are 1-5.

[0073] (3) The experimental procedure for the swelling of polymer nanocomposite sealing agents in CaCl2 salt solution is as follows.

[0074] Weigh 0.2g of polymer nanocomposite plugging agent, add CaCl2 solution and stir to suspend. Record the swelling data of the plugging agent sample for 20h according to the method of (1). The swelling rate is lower than that in water and NaCl solution, as shown in Table 1-5.

[0075] Example 7

[0076] The experimental evaluation procedure for core sealing and leakage prevention of nanocomposite sealing agents is as follows.

[0077] (1) Disperse 0.4 wt.% Na2CO3 and 6.0 wt.% Na-Mt in deionized water and stir overnight to obtain a base slurry; then, under continuous stirring, disperse the microsphere plugging agent of Example 2 in the base slurry to prepare a microsphere suspension with a concentration of 1500 mg / L. The plugging experiment was carried out as follows:

[0078] (2) Prepare artificial rock cores (permeability 0.189 μm). 2 Vacuum and saturated water experiments were conducted to measure the porosity and permeability of the selected rock cores, which were then dried in a forced-air oven.

[0079] (3) Select a rock core with a suitable initial permeability, measure its diameter and length, put it in water and evacuate it; then, install it in a multi-functional rock core sealing instrument and measure the water phase permeability K1 of the rock core.

[0080] (4) Turn on the horizontal flow pump connected to the DYQ2 test device, adjust the injection rate to 0.4 mL / min, inject 0.5 PV of water into the core to be tested, observe the change of the injection pressure curve until a smooth curve is formed, and record the pressure at this time as P1;

[0081] (5) Open the switching valve to switch to the microsphere suspension storage tank, and continue to inject 2.5PV of the prepared microsphere suspension into the above-mentioned water-injected rock core at the same injection rate;

[0082] (6) Then, switch back to the water storage tank and inject water at the same rate. Record the pressure at this time as P2, and calculate the water phase permeability K2 of the core after subsequent water injection. Calculate the permeability K value, plugging rate η, and residual resistance coefficient using the following formulas:

[0083]

[0084] In the formula, Q is the fluid flow rate within the rock core, in cm. 3 / s; L is the core length, cm; μ is the fluid viscosity within the core, μ = 1 mPa·s; A is the cross-sectional area of ​​the core, cm². 2 ΔP is the pressure difference between the two ends of the core after the injection of the sealing agent or during subsequent water injection, ΔP = P1 - P2 kPa; K1 is the initial permeability of the core, μm. 2 K2 is the permeability of the core sample after subsequent water injection, in μm. 2 FR is the residual drag coefficient, which is dimensionless.

[0085] Analysis of core plugging test results, see appendix. Figure 7 As shown, during the first water injection stage, the injection pressure gradually reaches equilibrium, and the injected water flows stably in the core pores. After the addition of the microsphere suspension, the injection pressure begins to fluctuate and rise. Under the injection pressure, the pure polymer microspheres in the core pores continuously move, adhere, and accumulate, forming blockages, leading to an increase in injection pressure. When the pressure is high enough, the microspheres are transported forward by the water flow, accumulating and blocking at deeper depths, causing the injection pressure to rise again. Moreover, the water-absorbing and expanding microspheres generate even greater injection pressure at deeper depths.

[0086] During the second water injection phase, the injection pressure rapidly decreased and gradually stabilized, reaching approximately 19 kPa. Compared to Comparative Example 1, the plugging rates of the 4-nanometer composite plugging agents in Examples 2 and 4 were increased by 13.5% and 18.2%, respectively, significantly improving plugging performance. Specific data can be found in the appendix. Figure 5 Table 5.

[0087] Example 8

[0088] The evaluation procedure for core plugging and channeling prevention using nanocomposite sealing agents follows the procedure in Example 7, with the only difference being that the core permeability used is 0.152. For sealing performance, see Appendix. Figure 5 Table 5.

[0089] In summary, the nanocomposite plugging agent prepared by the method disclosed in this invention uses an inorganic layered material and a polymer monomer and its additives system, prepared by free radical-initiated in-situ polymerization and composite method. It exhibits good self-expansion properties and can effectively plug loose sandstone oil and gas reservoirs, preventing damage to the reservoirs. The nanocomposite plugging agent possesses high mechanical strength, high-temperature and high-pressure viscoelastic deformation properties, and plugging strength, enabling it to generate a high-temperature and high-pressure resistant plugging effect in deep and ultra-deep drilling environments. Compared with existing technologies, this invention uses a nanostructured reinforcing phase to design controllable high sphericity, expansion, and high-temperature resistant multifunctional nanocomposite microspheres, offering simplicity, low cost, and high efficiency.

[0090] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0091] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0092] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A nanocomposite sealing agent, characterized in that, It includes the following components: inorganic layered materials, polymer monomers and their auxiliary agent system, and free radical initiators.

2. The nanocomposite sealing agent according to claim 1, characterized in that, The inorganic layered material is at least one of bentonite, diatomite, lithium saponite, sepiolite, or montmorillonite.

3. The nanocomposite sealing agent according to claim 1, characterized in that, The polymer monomer is at least two of acrylamide (AM), acryloylmorpholine, acrylic acid (AA), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS).

4. The nanocomposite sealing agent according to claim 1, characterized in that, The polymer monomer additive system is an emulsion suspension reaction system formed by dispersing an emulsifier in an organic solvent, wherein the emulsifier is at least one of Span-80, industrial Tween-60, and industrial polymeric alcohol.

5. The nanocomposite sealing agent according to claim 1, characterized in that, The free radical initiator includes an initiator and a crosslinking agent; the initiator is at least one selected from persulfate, sodium bisulfite, sodium sulfite, and diisobutyronitrile peroxide, and the crosslinking agent is N,N-methylenebisacryloyl (MBA).

6. The nanocomposite sealing agent according to claim 1, characterized in that, The inorganic layered material is pretreated with an organic intercalating agent; the organic intercalating agent is at least one of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate.

7. The nanocomposite sealing agent according to claim 6, characterized in that, After pretreatment, the interlayer spacing of the inorganic layered material is greater than or equal to 1.90 nm.

8. A method for preparing a nanocomposite sealing agent as described in any one of claims 1-7, characterized in that, This includes the following operations: Inorganic layered materials are pretreated by adding them to deionized water to fully swell and obtain a suspension. The pH value of the suspension is adjusted, and then an intercalating agent is added and stirred evenly. The mixture is heated to react and obtain the pretreated inorganic layered materials. A polymer monomer and additive system is prepared, an emulsion suspension reaction system is prepared, then an aqueous monomer-polymer system is prepared, and the two are mixed together. To prepare the blocking agent, the treated inorganic layered material is added to the monomer polymer and its additive system, stirred thoroughly and the pH value is adjusted. Then, a free radical initiator is added to initiate the reaction product.

9. The method for preparing the nanocomposite sealing agent according to claim 8, characterized in that, The interlayer spacing of the pretreated inorganic layered material is greater than or equal to 1.90 nm.

10. The application of a nanocomposite sealing agent as described in any one of claims 1 to 7, characterized in that, This sealing agent is used in the process of plugging leaks or blocking oil, gas and water leakage in deep oil and gas engineering.

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