Nano plugging agent for shale drilling and preparation method and application thereof

Abstract

The invention provides a nano plugging agent for shale drilling and a preparation method and application thereof, the nano plugging agent for shale drilling comprises the following preparation raw materials: silane coupling agent modified nano silicon dioxide, a polymeric monomer, an emulsifier and an initiator; the polymeric monomer is one or a combination of at least two of styrene, sodium p-styrenesulfonate, acrylic acid, acrylonitrile or methyl methacrylate. The nano plugging agent for shale drilling can effectively improve the plugging rate, has the characteristics of good dispersity and stability, difficulty in breaking, strong adaptability to the sizes and shapes of pores and cracks and the like, meets the plugging requirements of shale nano-scale cracks, efficiently reduces pressure transmission and filtrate invasion, and prevents well wall instability.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas well engineering, and relates to a nano plugging agent for shale drilling, a preparation method and an application thereof. Background Art

[0002] With my country's rapid economic development, the demand for oil and gas resources continues to grow. The strategic importance of unconventional energy sources, such as shale oil and gas, continues to rise, making them a research hotspot in the oil and gas sector. Their efficient exploration and development are crucial for ensuring national energy security and optimizing the energy structure. Shale formations, characterized by their rich micro- and nano-pores and bedding, are highly water-sensitive. This interaction with drilling fluids, particularly water-based fluids, leads to a particularly prominent problem of wellbore instability, severely impacting shale drilling efficiency and costs. Improving drilling fluid performance is a key approach to maintaining wellbore stability.

[0003] Shale typically has low permeability and microscopic channels called "microcracks and pores." Effectively plugging these microcracks and nanopores, slowing pressure transmission and filtrate invasion, is a key drilling fluid technology measure for achieving wellbore stability in shale formations. Forming a fine, low-permeability mudcake on the wellbore is an effective method for mitigating filtrate invasion. However, because the particle size of these drilling fluids is larger than the pore size of the shale formation, they fail to form an effective mudcake and prevent fluid invasion. To achieve a low-permeability mudcake on shale, the additive particle size should be smaller than the pore throat size of the shale. Conventional drilling fluid plugging materials, such as ultrafine calcium carbonate, polymer plugging agents, and asphalt, typically have particle sizes in the micrometer range (1 to 100 μm), making them ineffective at plugging nanopores. Furthermore, conventional plugging agents suffer from poor dispersion stability, insufficient temperature and pressure resistance, and ineffective wellbore wall solidification. Therefore, only by using micro-nano-scale plugging agents with a certain strength can a dense pressure-bearing plugging layer be truly formed inside the shale, effectively preventing pressure transmission and filtrate intrusion, and achieving the purpose of strengthening and stabilizing the shale well wall.

[0004] Therefore, providing a nano plugging agent with good hydrophilicity and strong plugging ability is of great significance to meet the needs of shale formation oil and gas drilling. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a nano plugging agent for shale drilling and a preparation method and application thereof.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In one aspect, the present invention provides a nano plugging agent for shale drilling, the raw materials for its preparation include the following components: nano silicon dioxide modified by a silane coupling agent, a polymer monomer, an emulsifier and an initiator;

[0008] The polymerizable monomer is one or a combination of at least two of styrene, sodium styrene sulfonate, acrylic acid, acrylonitrile or methyl methacrylate.

[0009] The nano-plugging agent for shale drilling of the present invention has a "core-shell" structure. It can form a shale-tightening plugging layer through "adsorption-bridging-filling", effectively improving the plugging rate. At the same time, it has good dispersibility and stability, is not easy to break, and has strong adaptability to the size and shape of pores and cracks. It meets the plugging needs of shale nanoscale cracks, effectively reduces pressure transmission and filtrate intrusion, and prevents wellbore instability. The nano-plugging agent for shale drilling of the present invention can not only ensure the plugging pressure bearing capacity of the nano-plugging agent for shale drilling, but also improve the deformable filling-plugging effect of the nano-plugging agent for shale drilling, which can effectively plug the pores and cracks of the formation, slow down the pressure transmission, reduce the loss of water-based drilling fluid, and achieve the purpose of significantly improving the stability of the shale wellbore.

[0010] Preferably, the polymerizable monomer is a mixture of styrene and methyl methacrylate.

[0011] Preferably, the mass ratio of styrene to methyl methacrylate in the mixture is 1-1.1:1, for example 1:1, 1.05:1, 1.08:1 or 1:1.

[0012] Preferably, the silane coupling agent is selected from at least one of γ-aminopropyltriethoxysilane (KH-550), γ-methacryloxypropyltrimethoxysilane (KH-570), and vinyltrimethoxysilane (KH-171), and more preferably γ-aminopropyltriethoxysilane (KH-550).

[0013] Preferably, the particle size of the nano-silica is 5 to 50 nm, for example, 5 nm, 8 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm or 50 nm.

[0014] Preferably, the preparation method of the silane coupling agent-modified nano-silica comprises the following steps:

[0015] The nano-silica and the silane coupling agent are added into a solvent, mixed and reacted to obtain the nano-silica modified by the silane coupling agent.

[0016] Preferably, the mass ratio of the nano-silica to the silane coupling agent is 1:(10-25), for example, 1:10, 1:13, 1:15, 1:18, 1:20, 1:21, 1:22, 1:23, 1:24 or 1:25.

[0017] Preferably, the solvent is anhydrous ethanol.

[0018] Preferably, the reaction temperature is 50-80°C, such as 50°C, 55°C, 58°C, 60°C, 65°C, 70°C, 75°C or 80°C, preferably 60-75°C, and the reaction time is 4-6h, such as 4h, 4.5h, 5h, 5.5h or 6h, preferably 4-5h.

[0019] Preferably, the mass ratio of the silane coupling agent-modified nano-silica to the polymerized monomer is (6-10):1, for example, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1 or 10:1.

[0020] Preferably, the mass ratio of the emulsifier to the modified nano-silica is 1:(15-20), for example, 1:15, 1:16, 1:17, 1:18, 1:19 or 1:20.

[0021] Preferably, the emulsifier includes an anionic surfactant and a nonionic surfactant.

[0022] Preferably, the anionic surfactant is selected from at least one of sodium dodecyl sulfate (SDS), sodium dodecylbenzenesulfonate (SDBS), and sodium hexametaphosphate (SHMP), and more preferably sodium dodecylbenzenesulfonate (SDBS).

[0023] Preferably, the nonionic surfactant is selected from at least one of octylphenol polyoxyethylene ether (OP-4), octylphenol polyoxyethylene ether (OP-10), and alkylphenol polyoxyethylene ether (TX-10), and more preferably octylphenol polyoxyethylene ether (OP-4).

[0024] Preferably, the mass ratio of the anionic surfactant to the nonionic surfactant is (1-1.1):1, such as 1:1, 1.05:1, 1.08:1 or 1.1:1.

[0025] Preferably, the initiator is selected from at least one of potassium persulfate, ammonium persulfate or azobisisobutyronitrile (AIBN), more preferably ammonium persulfate.

[0026] Preferably, the mass ratio of the initiator to the polymerization monomer is 1:(20-24), for example, 1:20, 1:21, 1:22, 1:23 or 1:24.

[0027] In a second aspect, the present invention provides a method for preparing the nano plugging agent for shale drilling as described above, the preparation method comprising the following steps:

[0028] (1) dispersing nano-silica modified with a silane coupling agent, a polymerizable monomer, and an emulsifier in a solvent, heating the solvent to react, and obtaining a reaction solution;

[0029] (2) Adding an initiator to the reaction solution of step (1) to carry out a reaction to obtain the nano plugging agent for shale drilling.

[0030] Preferably, the dispersion in step (1) is carried out by ultrasonic dispersion.

[0031] Preferably, the solvent in step (1) is water, preferably deionized water.

[0032] Preferably, the temperature rising reaction in step (1) is to rise to 60-85°C, for example, 60°C, 63°C, 65°C, 68°C, 70°C, 73°C, 75°C, 78°C, 80°C, 83°C or 85°C, preferably 70-80°C, and the reaction time is 1-3h, for example, 1h, 1.5h, 2h, 2.5h or 3h, preferably 1-2h.

[0033] Preferably, the reaction temperature in step (2) is 60-85°C, for example, 60°C, 63°C, 65°C, 68°C, 70°C, 73°C, 75°C, 78°C, 80°C, 83°C or 85°C, and the reaction time is 1-3h, for example, 1h, 1.5h, 2h, 2.5h or 3h, preferably 2-3h.

[0034] On the other hand, the present invention provides the use of the nano-sealing agent for shale drilling as described above in sealing cracks in a shale formation well wall.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The nano plugging agent for shale drilling provided by the present invention has good dispersion stability and is not easy to agglomerate or aggregate.

[0037] (2) The nano plugging agent for shale drilling provided by the present invention has the characteristics of strong adaptability to the size and shape of pores and cracks in shale formations.

[0038] (3) The nano plugging agent for shale drilling provided by the present invention has strong pressure bearing capacity, can effectively improve the plugging rate, slow down the intrusion of drilling fluid into the reservoir, and significantly improve the stability of the shale formation well wall.

[0039] (4) The raw materials of the nano plugging agent for shale drilling provided by the present invention are low-cost and easy to obtain, the preparation method is simple and easy, the reaction conditions are mild and easy to control, and it is easy to achieve large-scale production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is the particle size distribution diagram of the plugging agent prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0042] Unless otherwise specified, the materials used in the examples can be obtained from commercial sources.

[0043] Example 1

[0044] This embodiment provides a nano plugging agent for shale drilling. The preparation method of the nano plugging agent for shale drilling is as follows:

[0045] 1) Disperse 2 parts of dried nano-silica (5-50 nm, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) in 100 parts of anhydrous ethanol and ultrasonically disperse for 1 hour; dissolve 0.2 parts of silane coupling agent KH550 in 20 parts of anhydrous ethanol and magnetically stir for 1 hour;

[0046] 2) The two solutions in step 1) were sequentially added to a reaction vessel, mechanically stirred, and heated to 70° C. After reacting for 4 hours, heating was stopped. The reaction product was washed three times with anhydrous ethanol and vacuum dried at 70° C. to obtain modified nano-silica.

[0047] 3) In another reaction vessel equipped with a condenser, a stirrer, and a thermometer, add 100 parts of deionized water, 1 part of sodium lauryl sulfate, 1 part of octylphenol polyoxyethylene ether-4, 30 parts of modified nano-silica, 2 parts of styrene, and 2 parts of methyl methacrylate in this order, and ultrasonically disperse for 1 hour; under mechanical stirring, heat to 75°C and maintain the temperature for 1 hour;

[0048] 4) Add 0.2 parts of ammonium persulfate as an initiator, initiate the reaction for 2 hours, stop heating, and allow the mixture to cool naturally in air to obtain nano-plugging agent A1 for shale drilling based on modified nano-silica.

[0049] The nanometer plugging agent prepared in this example was characterized using a Malvern NanoSizer. Figure 1 As shown, it can be seen that the particle diameter is mainly distributed in the range of 80-150 nm.

[0050] Example 2

[0051] This embodiment provides a nano plugging agent for shale drilling used in drilling fluid. The preparation method of the nano plugging agent for shale drilling used in drilling fluid is as follows:

[0052] 1) Disperse 2 parts of dried nano-silica (5-50 nm, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) in 100 parts of anhydrous ethanol and ultrasonically disperse for 1 hour; dissolve 0.15 parts of silane coupling agent KH550 in 20 parts of anhydrous ethanol and magnetically stir for 2 hours;

[0053] 2) The two solutions in step 1) were sequentially added to a reaction vessel, mechanically stirred, and heated to 75° C. After reacting for 5 h, heating was stopped. The reaction product was washed three times with anhydrous ethanol and vacuum dried at 70° C. to obtain modified nano-silica.

[0054] 3) In another reaction vessel equipped with a condenser, a stirrer, and a thermometer, add 100 parts of deionized water, 1 part of sodium lauryl sulfate, 1 part of octylphenol polyoxyethylene ether-4, 35 parts of modified nano-silica, 2.2 parts of styrene, and 2 parts of methyl methacrylate in this order, and ultrasonically disperse for 1.5 hours; under mechanical stirring, heat to 75°C and maintain the temperature for 1 hour;

[0055] 4) Add 0.2 parts of ammonium persulfate as an initiator, initiate the reaction for 2.5 hours, stop heating, and allow the mixture to cool naturally in air to obtain a nano-plugging agent A2 for shale drilling based on modified nano-silica.

[0056] Example 3

[0057] This embodiment provides a nano plugging agent for shale drilling used in drilling fluid. The preparation method of the nano plugging agent for shale drilling used in drilling fluid is as follows:

[0058] 1) Disperse 2 parts of dried nano-silica (5-50 nm, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) in 100 parts of anhydrous ethanol and ultrasonically disperse for 1 hour; dissolve 0.25 parts of silane coupling agent KH550 in 20 parts of anhydrous ethanol and magnetically stir for 1 hour;

[0059] 2) The two solutions in step 1) were sequentially added to a reaction vessel, mechanically stirred, and heated to 80° C. After reacting for 4.5 hours, heating was stopped. The reaction product was washed three times with anhydrous ethanol and then vacuum-dried at 70° C. to obtain modified nano-silica.

[0060] 3) In another reaction vessel equipped with a condenser, a stirrer, and a thermometer, add 100 parts of deionized water, 1 part of sodium lauryl sulfate, 1 part of octylphenol polyoxyethylene ether-4, 40 parts of modified nano-silica, 2.2 parts of styrene, and 2.2 parts of methyl methacrylate in this order, and ultrasonically disperse for 2.5 hours; under mechanical stirring, heat to 75°C and maintain the temperature for 1 hour;

[0061] 4) Add 0.2 parts of ammonium persulfate as an initiator, initiate the reaction for 3 hours, stop heating, and allow the mixture to cool naturally in air to obtain a nano-plugging agent A3 for shale drilling based on modified nano-silica.

[0062] Example 4

[0063] This comparative example provides a nano plugging agent for shale drilling used in drilling fluid, which is prepared according to the preparation method of Example 1, except that 2 parts of methyl methacrylate in Example 1 are replaced by 2 parts of acrylic acid, and other conditions remain unchanged.

[0064] Comparative Example 1

[0065] This comparative example provides a nano plugging agent for shale drilling used in drilling fluid, which is prepared according to the preparation method of Example 1, except that methyl methacrylate is not added and other conditions remain unchanged.

[0066] Application Examples

[0067] 1) Preparation of prehydrated base slurry: Add 0.14 parts by weight of sodium carbonate and 4 parts by weight of bentonite for drilling fluid test slurry to 100 parts by weight of distilled water while stirring, stir at a high speed of 11000 r / min±300 r / min for 20 minutes, and seal and cure at 25℃±1℃ for 24 hours to prepare the base slurry.

[0068] 2) 3 wt % of the nano plugging agents for shale drilling prepared in Examples 1-4 of the present invention and Comparative Example 1 were added to the prehydrated base slurry obtained in step 1) to prepare plugging water-based drilling fluids F1-F5.

[0069] Performance Testing

[0070] To further illustrate the advanced properties of the nano plugging agents for shale drilling prepared in Examples 1-4 and Comparative Example 1, the following performance tests were conducted:

[0071] Test Example 1

[0072] According to the determination method in GB / T16783.1-2014 Field Test of Drilling Fluids in Petroleum and Natural Gas Industry Part 1: Water-Based Drilling Fluids, a six-speed rotational viscometer was used to test the values of base slurry and water-based drilling fluids F1-F5 under different conditions at rotation speeds of 600 r / min and 300 r / min, and the apparent viscosity (AV), plastic viscosity (PV) and dynamic shear force YP of the drilling fluid were calculated using the formula.

[0073] Use high temperature and high pressure filter loss tester to measure the high temperature and high pressure filter loss FL of base mud and water-based drilling fluid F1-F5 HTHP (Test temperature 150℃).

[0074] The test results of the effects of the plugging agents prepared in Examples 1-4 and Comparative Example 1 on the rheological and filtration properties of the drilling fluid are shown in Table 1.

[0075] Table 1

[0076]

[0077]

[0078] The experimental results shown in Table 1 show that after adding the nano plugging agents for shale drilling prepared in Examples 1-4 and Comparative Example 1, the apparent viscosity and plastic viscosity of the water-based drilling fluid increased slightly, and the dynamic shear force remained at 14-20 Pa, indicating that the nano plugging agents for shale drilling have little effect on the rheological properties of the water-based drilling fluid. HTHP The addition of nano plugging agent significantly reduced the flow rate, indicating that the nano plugging agent has a significant effect in reducing filtration loss.

[0079] Test Example 2

[0080] This test example was used to evaluate the plugging performance of the nano-plugging agents for shale drilling prepared in Examples 1-4 and Comparative Example 1. Natural shale cores from a specific region were used to simulate nanoporous formations. Flow rate measurements were performed and Darcy's equation was used to calculate the core permeability before and after the plugging agent was added. The plugging efficiency of the nano-plugging agents for shale drilling was calculated, and the results are reported in Table 2.

[0081] Table 2 Core permeability test results with different nano plugging agent dosages

[0082]

[0083]

[0084] As can be seen from Table 2, within the dosage range of 1% to 3%, the addition of the plugging agent has a significant effect on the permeability of the drilling fluid. When the dosage is 3%, the corresponding shale plugging rates of Example 1, Example 2, Example 3, and Example 4 are 94.03%, 93.69%, 92.93%, and 91.37%, respectively. The plugging effect is excellent and can effectively prevent the drilling fluid filtrate and solid phase from further invading the reservoir.

[0085] In summary, the nano plugging agent for shale drilling of the present invention can effectively improve the plugging rate of shale formations, reduce filtration loss, and meet the wellbore stability requirements of shale drilling.

[0086] The applicant states that while the above-described embodiments illustrate the process of the present invention, the present invention is not limited to the above-described process steps, nor does it imply that the present invention must rely on the above-described process steps for implementation. Those skilled in the art will appreciate that any improvements to the present invention, equivalent substitutions for the raw materials used, additions of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A nano plugging agent for shale drilling, characterized in that: The raw materials for preparing the nano plugging agent for shale drilling include the following components: nano silicon dioxide modified by a silane coupling agent, a polymer monomer, an emulsifier and an initiator; The polymerizable monomer is one or a combination of at least two of styrene, sodium styrene sulfonate, acrylic acid, acrylonitrile or methyl methacrylate.

2. The nano plugging agent for shale drilling according to claim 1, characterized in that: The polymerizable monomer is a mixture of styrene and methyl methacrylate; Preferably, the mass ratio of styrene to methyl methacrylate in the mixture is 1-1.1:

1.

3. The nano plugging agent for shale drilling according to claim 1 or 2, characterized in that: The silane coupling agent is selected from at least one of γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, and vinyltrimethoxysilane, and is more preferably γ-aminopropyltriethoxysilane; Preferably, the particle size of the nano-silicon dioxide is 5 to 50 nm.

4. The nano plugging agent for shale drilling according to any one of claims 1 to 3, characterized in that: The preparation method of the silane coupling agent-modified nano-silica comprises the following steps: The nano-silica and the silane coupling agent are added into a solvent, mixed and reacted to obtain the nano-silica modified by the silane coupling agent.

5. The nano plugging agent for shale drilling according to claim 4, characterized in that: The mass ratio of the nano-silica to the silane coupling agent is 1:(10-25); Preferably, the solvent is anhydrous ethanol; Preferably, the reaction temperature is 50-80°C and the reaction time is 4-6h; Preferably, the mass ratio of the nano-silica modified by the silane coupling agent to the polymerized monomer is (6-10):

1.

6. The nano plugging agent for shale drilling according to any one of claims 1 to 5, characterized in that: The mass ratio of the emulsifier to the nano-silica modified by the silane coupling agent is 1:(15-20); Preferably, the emulsifier includes an anionic surfactant and a nonionic surfactant; Preferably, the anionic surfactant is selected from at least one of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate or sodium hexametaphosphate, more preferably sodium dodecylbenzenesulfonate; Preferably, the nonionic surfactant is selected from at least one of octylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether or alkylphenol polyoxyethylene ether, more preferably octylphenol polyoxyethylene ether.

7. The nano plugging agent for shale drilling according to any one of claims 1 to 6, characterized in that: The mass ratio of the anionic surfactant to the nonionic surfactant is (1-1.1):1; Preferably, the initiator is selected from at least one of potassium persulfate, ammonium persulfate or azobisisobutyronitrile, more preferably ammonium persulfate; Preferably, the mass ratio of the initiator to the polymerization monomer is 1:(20-24).

8. The method for preparing a nano plugging agent for shale drilling according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: (1) dispersing nano-silica modified with a silane coupling agent, a polymerizable monomer, and an emulsifier in a solvent, heating the solvent to react, and obtaining a reaction solution; (2) Adding an initiator to the reaction solution in step (1) to carry out a reaction to obtain the nano plugging agent for shale drilling.

9. The preparation method according to claim 8, characterized in that The dispersion in step (1) is carried out by ultrasonic dispersion; Preferably, the solvent in step (1) is water, preferably deionized water; Preferably, the temperature of step (1) is raised to 60-85°C, preferably 70-80°C, and the reaction time is 1-3h, preferably 1-2h; Preferably, the reaction temperature in step (2) is 60-85° C., and the reaction time is 1-3 h, preferably 2-3 h.

10. Use of the nano plugging agent for shale drilling according to any one of claims 1 to 7 in plugging cracks in shale formation well walls.

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