An organic silicon microgel borehole strengthening agent for ultra-deep well drilling fluid and a preparation method and application thereof

Abstract

The present application relates to a kind of organic silicon microgel borehole strengthening agent for ultra-deep well drilling fluid and its preparation method and application, belong to the drilling fluid chemistry field of petroleum industry;The present application is first prepared with vinyl-containing organic silicon nanometer microspheres, with vinyl-containing organic silicon nanometer microspheres as primary micro-nucleus, functional monomer is selected and grafted copolymerization is carried out on the surface of vinyl-containing organic silicon nanometer microspheres, to obtain organic silicon microgel borehole strengthening agent, applicable to ultra-deep well drilling fluid, the strengthening agent can effectively block stratum micro-nanometer hole gap, delay the tendency of drilling fluid under the action of drilling positive pressure difference into stratum;In addition, it has high glass transition temperature, when being at glass transition temperature, it will be converted into viscous rubber state to improve the cementation solid wall effect to rock, improve rock strength, effectively improve borehole stability.

Description

Technical Field

[0001] This invention relates to an organosilicon microgel wellbore enhancer for ultra-deep well drilling fluid, its preparation method and application, belonging to the field of drilling fluid chemistry in the petroleum industry. Background Technology

[0002] As my country's exploration and development of traditional shallow and medium-depth oil and gas reservoirs enters the middle and late stages, efforts to alleviate this contradiction are gradually increasing in the exploration and development of deep and ultra-deep oil and gas reservoirs. my country possesses abundant deep and ultra-deep oil and gas reserves. Taking the Sichuan Basin and Tarim Basin as examples, the ultra-deep gas-bearing reserves in the Sichuan Basin alone are 6×10⁻⁶. 12 m 3 The Tarim Basin has ultra-deep oil reserves of 1×10⁻⁶. 9 Numerous domestic and international drilling results indicate that deep and ultra-deep formations face significant challenges due to harsh conditions such as high temperature, high pressure, and long-distance drilling. Regarding high-temperature conditions, drilling fluid clay undergoes severe dehydration, drilling fluid treatment agents experience high-temperature degradation, and desorbents exhibit high-temperature cross-linking. These problems lead to difficulties in controlling the rheological properties of the drilling fluid system, a significant increase in filtration loss, and other serious issues, severely impacting wellbore stability.

[0003] Drilling fluid plugging agents, as one of the core drilling fluid treatment agents used in deep and ultra-deep well drilling operations, have been extensively studied. Currently, commonly used drilling fluid treatment agents are mainly classified into inorganic (calcium carbonate, silica, graphite, etc.), organic (polymers, organic fibers, etc.), and organic-inorganic hybrid plugging agents. Conventional inorganic plugging agents primarily prevent drilling fluid intrusion by physically filling and sealing micropores and fractures in the formation, thus stabilizing the wellbore; however, their functionality is often relatively limited. While organic plugging agents possess good deformation-sealing performance, they suffer from poor temperature resistance and limited effectiveness in deep and ultra-deep wells. Organic-inorganic hybrid plugging agents, although combining the functional characteristics of both, can effectively improve the sealing efficiency of formation micropores and fractures, but they cannot effectively improve rock cohesion, thus limiting their effect on improving wellbore stability.

[0004] Patent document CN118027316A discloses a high-temperature resistant and saturated salt-resistant nano-plugging agent and its preparation method. It utilizes diphenylmethane diisocyanate to modify nano-SiO2, and modifies the surface of the nano-SiO2 through surface grafting modification. Subsequently, a high-temperature resistant and saturated salt-resistant nano-plugging agent is prepared via free radical polymerization. This plugging agent can withstand temperatures up to 200℃ and exhibits good high-temperature stability. Patent document CN114381246A discloses a high-temperature resistant modified hexagonal boron nitride nano-plugging agent and a water-based drilling fluid. This plugging agent is prepared from nano-hexagonal boron nitride (80-100nm), amino-containing silane coupling agents, diene alcohols, bis-primary amines, and alkene-containing sulfonic acid compounds as raw materials. It withstands temperatures up to 150℃ and exhibits excellent particle size stability at high temperatures. The above methods all prepare organic-inorganic composite materials with inorganic materials as the core and organic materials as the shell. Although they have good high-temperature stability, their performance improvement of drilling fluid is mainly in the sealing and filtration reduction performance. The effect on rock strength at high temperature is not involved, and the effect is singular. Summary of the Invention

[0005] To address the shortcomings of existing technologies, especially the deterioration of plugging agent performance and the limited functionality of drilling fluids at high temperatures (greater than 180°C) during ultra-deep formation drilling, this invention provides an organosilicon microgel wellbore enhancer for ultra-deep well drilling fluids, its preparation method, and its application.

[0006] This invention prepares an organosilicon microgel wellbore enhancer through hydrolysis condensation reaction and free radical polymerization reaction, which is suitable for ultra-deep well drilling fluid. This enhancer can effectively seal the micro- and nano-pores of the formation and delay the tendency of drilling fluid to enter the formation under the action of drilling positive pressure differential. In addition, it has a high glass transition temperature. When it is at the glass transition temperature, it will transform into a viscous rubber state, thereby enhancing the cementation and wall consolidation effect on the rock, increasing the rock strength, and effectively improving the wellbore stability.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] A method for preparing an organosilicon microgel wellbore enhancer for ultra-deep well drilling fluid includes the following steps:

[0009] (1) Preparation of vinyl organosilicon nanospheres

[0010] Emulsifier a and xanthan gum were added to deionized water in sequence and stirred at high speed to obtain a mixture. Organosilicon mixed monomers were added to the mixture and stirred at high speed. The mixture was then heated in a water bath to react. After the reaction, the mixture was centrifuged and the resulting solid phase was washed with ethanol and petroleum ether respectively and centrifuged to obtain organosilicon nanospheres containing vinyl groups.

[0011] (2) Preparation of organosilicon microgel wellbore enhancer

[0012] Using the vinyl-containing organosilicon nanospheres obtained in step (1) as the primary micronucleus, functional monomers are selected to perform graft copolymerization on the surface of the vinyl organosilicon nanospheres to obtain organosilicon microgel well wall reinforcing agent.

[0013] According to a preferred embodiment of the present invention, in step (1), emulsifier a is emulsifier OS (MS-1).

[0014] According to a preferred embodiment of the present invention, in step (1), the mass-to-volume ratio of emulsifier a to deionized water is 0.5-2.0:100, in g / mL.

[0015] According to a preferred embodiment of the present invention, in step (1), the mass ratio of xanthan gum to emulsifier a is (0.01-0.04):(0.5-2.0).

[0016] According to a preferred embodiment of the present invention, in step (1), the organosilicon mixed monomer is a mixture of vinyltriethoxysilane and triethoxysilane, and the mass ratio of vinyltriethoxysilane to triethoxysilane is 1:(2-6).

[0017] According to a preferred embodiment of the present invention, in step (1), the mass ratio of organosilicon mixed monomers to emulsifier a is (20-30): (0.5-2.0).

[0018] According to a preferred embodiment of the present invention, in step (1), the high-speed stirring speed is 800-1500 r / min and the stirring time is 10-30 min.

[0019] According to a preferred embodiment of the present invention, in step (1), the water bath heating temperature is 30-50°C and the heating time is 6-12 hours.

[0020] According to a preferred embodiment of the present invention, the specific method for graft copolymerization on the surface of vinyl organosilicon nanospheres in step (2) is as follows:

[0021] 1) Emulsifier b, sodium styrene sulfonate, and crosslinking agent N N-methylenebisacrylamide were added sequentially to deionized water and stirred at high speed at room temperature to obtain an aqueous phase; butyl acrylate, acrylic acid, vinyl-containing organosilicon nanospheres from step (1) and emulsifier c were mixed evenly to obtain an oil phase;

[0022] 2) Slowly add the oil phase to the aqueous phase and stir at high speed. Once all the oil phase has been added to the aqueous phase, stir at high speed to obtain a stable oil-in-water emulsion. Stir and heat the oil-in-water emulsion, add an initiator, and react at room temperature to obtain an organosilicon microgel wellbore reinforcing agent.

[0023] According to a preferred embodiment of the present invention, in step 1), the emulsifier b is Tween 80.

[0024] According to a preferred embodiment of the present invention, in step 1), the mass ratio of emulsifier b, sodium styrene sulfonate, and crosslinking agent N N-methylenebisacrylamide is (1.0-2.0):(2-5):(0.02-0.05).

[0025] According to a preferred embodiment of the present invention, in step 1), the mass-to-volume ratio of emulsifier b to water is (1.0-2.0):100, in g / mL.

[0026] According to a preferred embodiment of the present invention, in step 1), the mass ratio of butyl acrylate, acrylic acid, and vinyl-containing organosilicon nanospheres is (6-11):(3-7):(4-8).

[0027] According to a preferred embodiment of the present invention, in step 1), the emulsifier c is Span 80.

[0028] According to a preferred embodiment of the present invention, in step 1), the mass ratio of the vinyl-containing organosilicon nanospheres to the emulsifier c is (4-8):(0.3-0.7).

[0029] According to a preferred embodiment of the present invention, in step 1), the high-speed stirring speed is 800-1500 r / min and the stirring time is 10-30 min.

[0030] According to a preferred embodiment of the present invention, in step 2), after all the oil phase is added to the aqueous phase, the mixture is stirred at high speed for 20 minutes at 3000 r / min using a shear emulsifier.

[0031] The shear emulsifier is applied according to existing techniques in the art.

[0032] According to a preferred embodiment of the present invention, in step 2), the heating temperature for stirring is 60-80°C, and the stirring speed is 300 r / min.

[0033] According to a preferred embodiment of the present invention, in step 2), the initiator is azobisisobutyronitrile with a mass fraction of 30%.

[0034] According to a preferred embodiment of the present invention, in step 2), the mass ratio of the vinyl-containing organosilicon nanospheres to the initiator is (4-8):(2.5-5).

[0035] An organosilicon microgel wellbore enhancer for ultra-deep well drilling fluid is prepared by the above method.

[0036] The above-mentioned organosilicon microgel wellbore enhancer for ultra-deep well drilling fluid is added to the drilling fluid to improve the plugging effect of conventional wells and ultra-deep wells in oil drilling operations. The amount of enhancer added is 2%-4% of the weight of the drilling fluid.

[0037] The organosilicon microgel wellbore strengthener for ultra-deep well drilling fluid of the present invention will transform into a viscoelastic state when the bottom hole temperature is within the glass transition temperature range of the wellbore strengthener, thereby playing a role in bonding rocks and improving rock strength.

[0038] The beneficial effects of the present invention through the above technical solution are as follows:

[0039] 1. In the drilling fluid of the present invention, the organosilicon microgel wellbore enhancer is a continuous phase in water-based drilling fluid. The wellbore enhancer particles are extremely dispersed and will not agglomerate at high temperatures. When in a high-temperature well section (i.e., the glass transition temperature of the wellbore enhancer), the drilling fluid forms a mud cake on the well wall under the action of pressure difference in the wellbore. A large number of wellbore enhancer particles will aggregate together and thus change from a glassy state to a rubbery state under high temperature, producing a cementing and wall-solidifying effect on the well wall rock. Therefore, the wellbore enhancer of the present invention has high particle dispersion stability after high-temperature aging. The D50 change rate before and after aging at 220℃ is only 2.8%, which shows excellent high-temperature dispersion stability.

[0040] 2. The drilling fluid organosilicon microgel wellbore enhancer of the present invention has a particle size in the nano-microscale (92.3-425.6nm), and can have good plugging performance for microporous filter membranes of different particle size (0.1-1μm); it has excellent high temperature resistance, and still has plugging performance for microporous filter membranes of different particle size after aging at 220℃ for 16h.

[0041] 3. The glass transition temperature of the organosilicon microgel wellbore enhancer for drilling fluid of the present invention is 198.6°C. When the treatment agent is at its glass transition temperature, it can change from a glassy state to a high-viscosity rubber state, thereby improving the sealing performance of the well wall and the cementing performance of the rock.

[0042] Attached Description

[0043] Figure 1 This is a SEM image of the organosilicon microgel wellbore enhancer prepared in Example 1. Detailed Implementation

[0044] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0045] Example 1

[0046] The preparation method of organosilicon microgel wellbore enhancer for ultra-deep well drilling fluids includes the following steps:

[0047] (1) Preparation of vinyl organosilicon nanospheres

[0048] Measure 100 ml of deionized water and add it to a beaker. Then add 1.0 g of emulsifier OS (MS-1) and stir at high speed for 20 min. Add 0.025 g of xanthan gum (XC, acting as a dispersing stabilizer) to the beaker and stir at high speed for 20 min to fully dissolve the xanthan gum. Then weigh 24 g of organosilicon mixed monomers (vinyltriethoxysilane and triethoxysilane in a mass ratio of 1:3), stir and mix evenly at room temperature, and add it to the above beaker. Maintain a stirring speed of 1000 r / min and continue stirring for 20 min. Finally, transfer the above solution system to a three-necked flask and place it in a water bath at 40 °C for 8 h. After the reaction is completed, centrifuge and wash the lower solid phase twice with ethanol and petroleum ether, respectively, to obtain organosilicon nanospheres containing vinyl groups.

[0049] (2) Preparation of organosilicon microgels

[0050] Using the vinyl organosilicon nanospheres prepared in step (1) as the primary micronucleus, and simultaneously selecting functional monomers to graft copolymerize on the surface of the vinyl organosilicon nanospheres to obtain an organosilicon microgel well wall reinforcing agent, the specific method is as follows:

[0051] Measure 120 mL of deionized water into a beaker. Add 1.25 g of Tween 80, 3.5 g of sodium styrene sulfonate, and 0.035 g of crosslinking agent N,N-methylenebisacrylamide to the beaker sequentially. Stir at high speed for 20 min at room temperature to obtain the aqueous phase. Weigh 10 g of butyl acrylate, 5.5 g of acrylic acid, 5.5 g of vinyl silicone nanospheres, and 0.45 g of Span 80 sequentially into a 50 mL beaker and stir at high speed until homogeneous to obtain the oil phase. Slowly add the oil phase to the aqueous phase while stirring at high speed. Once all the oil phase has been added to the aqueous phase, use a shear emulsifier and stir at 3000 rpm for 20 min to obtain a stable oil-in-water emulsion. The above emulsion was transferred to a three-necked flask, the heating temperature was set to 70°C, and the stirring speed was 300 r / min. When the system temperature reached 70°C, 3.5 g of initiator (30% by mass of azobisisobutyronitrile) was added. The reaction was carried out at room temperature for 8 h to obtain organosilicon microgel wellbore enhancer.

[0052] SEM images of the prepared organosilicon microgel wellbore enhancer are shown below. Figure 1 .

[0053] Example 2

[0054] The preparation method of organosilicon microgel wellbore enhancer for ultra-deep well drilling fluids includes the following steps:

[0055] (1) Preparation of vinyl organosilicon nanospheres

[0056] Measure 100 ml of deionized water and add it to a beaker. Then add 1.0 g of emulsifier OS (MS-1) and stir at high speed for 20 min. Add 0.01 g of xanthan gum (XC, acting as a dispersant and stabilizer) to the beaker and stir at high speed for 20 min to fully dissolve the xanthan gum. Then weigh 24 g of organosilicon mixed monomers (vinyltriethoxysilane and triethoxysilane in a mass ratio of 1:3), stir and mix evenly at room temperature, and add it to the beaker. Maintain a stirring speed of 1000 r / min and continue stirring for 20 min. Finally, transfer the above solution system to a three-necked flask and place it in a water bath at 40 °C for 8 h. After the reaction is completed, centrifuge and wash the lower solid phase twice with ethanol and petroleum ether, respectively, to obtain organosilicon nanospheres containing vinyl groups.

[0057] (2) Preparation of organosilicon microgels

[0058] Using the vinyl organosilicon nanospheres prepared in step (1) as the primary micronucleus, and simultaneously selecting functional monomers to graft copolymerize on the surface of the vinyl organosilicon nanospheres to obtain an organosilicon microgel well wall reinforcing agent, the specific method is as follows:

[0059] Measure 120 mL of deionized water into a beaker. Add 1.25 g of Tween 80, 3.5 g of sodium styrene sulfonate, and 0.035 g of crosslinking agent N,N-methylenebisacrylamide to the beaker sequentially. Stir at high speed for 20 min at room temperature to obtain the aqueous phase. Weigh 10 g of butyl acrylate, 5.5 g of acrylic acid, 5.5 g of vinyl silicone nanospheres, and 0.45 g of Span 80 sequentially into a 50 mL beaker and stir at high speed until homogeneous to obtain the oil phase. Slowly add the oil phase to the aqueous phase while stirring at high speed. Once all the oil phase has been added to the aqueous phase, use a shear emulsifier and stir at 3000 rpm for 20 min to obtain a stable oil-in-water emulsion. The above emulsion was transferred to a three-necked flask, the heating temperature was set to 70°C, and the stirring speed was 300 r / min. When the system temperature reached 70°C, 3.5 g of initiator (30% by mass of azobisisobutyronitrile) was added. The reaction was carried out at room temperature for 8 h to obtain organosilicon microgel wellbore enhancer.

[0060] Example 3

[0061] The preparation method of organosilicon microgel wellbore enhancer for ultra-deep well drilling fluids includes the following steps:

[0062] (1) Preparation of vinyl organosilicon nanospheres

[0063] Measure 100 ml of deionized water and add it to a beaker. Then add 1.0 g of emulsifier OS (MS-1) and stir at high speed for 20 min. Add 0.025 g of xanthan gum (XC, acting as a dispersant and stabilizer) to the beaker and stir at high speed for 20 min to fully dissolve the xanthan gum. Then weigh 20 g of organosilicon mixed monomers (vinyltriethoxysilane and triethoxysilane in a mass ratio of 1:3), stir and mix evenly at room temperature, and add it to the beaker. Maintain a stirring speed of 1000 r / min and continue stirring for 20 min. Finally, transfer the above solution system to a three-necked flask and place it in a water bath at 40 °C for 8 h. After the reaction is completed, centrifuge and wash the lower solid phase twice with ethanol and petroleum ether, respectively, to obtain organosilicon nanospheres containing vinyl groups.

[0064] (2) Preparation of organosilicon microgels

[0065] Using the vinyl organosilicon nanospheres prepared in step (1) as the primary micronucleus, and simultaneously selecting functional monomers to graft copolymerize on the surface of the vinyl organosilicon nanospheres to obtain an organosilicon microgel well wall reinforcing agent, the specific method is as follows:

[0066] Measure 120 mL of deionized water into a beaker. Add 1.25 g of Tween 80, 3.5 g of sodium styrene sulfonate, and 0.035 g of crosslinking agent N,N-methylenebisacrylamide to the beaker sequentially. Stir at high speed for 20 min at room temperature to obtain the aqueous phase. Weigh 10 g of butyl acrylate, 5.5 g of acrylic acid, 5.5 g of vinyl silicone nanospheres, and 0.45 g of Span 80 sequentially into a 50 mL beaker and stir at high speed until homogeneous to obtain the oil phase. Slowly add the oil phase to the aqueous phase while stirring at high speed. Once all the oil phase has been added to the aqueous phase, use a shear emulsifier and stir at 3000 rpm for 20 min to obtain a stable oil-in-water emulsion. The above emulsion was transferred to a three-necked flask, the heating temperature was set to 70°C, and the stirring speed was 300 r / min. When the system temperature reached 70°C, 3.5 g of initiator (30% by mass of azobisisobutyronitrile) was added. The reaction was carried out at room temperature for 8 h to obtain organosilicon microgel wellbore enhancer.

[0067] Example 4

[0068] The preparation method of organosilicon microgel wellbore enhancer for ultra-deep well drilling fluids includes the following steps:

[0069] (1) Preparation of vinyl organosilicon nanospheres

[0070] Measure 100 ml of deionized water and add it to a beaker. Then add 1.0 g of emulsifier OS (MS-1) and stir at high speed for 20 min. Add 0.025 g of xanthan gum (XC, acting as a dispersing stabilizer) to the beaker and stir at high speed for 20 min to fully dissolve the xanthan gum. Then weigh 24 g of organosilicon mixed monomers (vinyltriethoxysilane and triethoxysilane in a mass ratio of 1:3), stir and mix evenly at room temperature, and add it to the above beaker. Maintain a stirring speed of 1000 r / min and continue stirring for 20 min. Finally, transfer the above solution system to a three-necked flask and place it in a water bath at 40 °C for 8 h. After the reaction is completed, centrifuge and wash the lower solid phase twice with ethanol and petroleum ether, respectively, to obtain organosilicon nanospheres containing vinyl groups.

[0071] (2) Preparation of organosilicon microgels

[0072] Using the vinyl organosilicon nanospheres prepared in step (1) as the primary micronucleus, and simultaneously selecting functional monomers to graft copolymerize on the surface of the vinyl organosilicon nanospheres to obtain an organosilicon microgel well wall reinforcing agent, the specific method is as follows:

[0073] Measure 120 mL of deionized water into a beaker. Add 1.25 g of Tween 80, 2.0 g of sodium styrene sulfonate, and 0.035 g of crosslinking agent N,N-methylenebisacrylamide to the beaker sequentially. Stir at high speed for 20 min at room temperature to obtain the aqueous phase. Weigh 10 g of butyl acrylate, 5.5 g of acrylic acid, 5.5 g of vinyl silicone nanospheres, and 0.45 g of Span 80 sequentially into a 50 mL beaker and stir at high speed until homogeneous to obtain the oil phase. Slowly add the oil phase to the aqueous phase while stirring at high speed. Once all the oil phase has been added to the aqueous phase, use a shear emulsifier and stir at 3000 rpm for 20 min to obtain a stable oil-in-water emulsion. The above emulsion was transferred to a three-necked flask, the heating temperature was set to 70°C, and the stirring speed was 300 r / min. When the system temperature reached 70°C, 3.5 g of initiator (30% by mass of azobisisobutyronitrile) was added. The reaction was carried out at room temperature for 8 h to obtain organosilicon microgel wellbore enhancer.

[0074] Example 5

[0075] The preparation method of organosilicon microgel wellbore enhancer for ultra-deep well drilling fluids includes the following steps:

[0076] (1) Preparation of vinyl organosilicon nanospheres

[0077] Measure 100 ml of deionized water and add it to a beaker. Then add 1.0 g of emulsifier OS (MS-1) and stir at high speed for 20 min. Add 0.025 g of xanthan gum (XC, acting as a dispersing stabilizer) to the beaker and stir at high speed for 20 min to fully dissolve the xanthan gum. Then weigh 24 g of organosilicon mixed monomers (vinyltriethoxysilane and triethoxysilane in a mass ratio of 1:3), stir and mix evenly at room temperature, and add it to the above beaker. Maintain a stirring speed of 1000 r / min and continue stirring for 20 min. Finally, transfer the above solution system to a three-necked flask and place it in a water bath at 40 °C for 8 h. After the reaction is completed, centrifuge and wash the lower solid phase twice with ethanol and petroleum ether, respectively, to obtain organosilicon nanospheres containing vinyl groups.

[0078] (2) Preparation of organosilicon microgels

[0079] Using the vinyl organosilicon nanospheres prepared in step (1) as the primary micronucleus, and simultaneously selecting functional monomers to graft copolymerize on the surface of the vinyl organosilicon nanospheres to obtain an organosilicon microgel well wall reinforcing agent, the specific method is as follows:

[0080] Measure 120 mL of deionized water into a beaker. Add 1.25 g of Tween 80, 3.5 g of sodium styrene sulfonate, and 0.035 g of crosslinking agent N,N-methylenebisacrylamide to the beaker sequentially. Stir at high speed for 20 min at room temperature to obtain the aqueous phase. Weigh 6 g of butyl acrylate, 5.5 g of acrylic acid, 5.5 g of vinyl silicone nanospheres, and 0.45 g of Span 80 sequentially into a 50 mL beaker and stir at high speed until homogeneous to obtain the oil phase. Slowly add the oil phase to the aqueous phase while stirring at high speed. Once all the oil phase has been added to the aqueous phase, use a shear emulsifier and stir at 3000 rpm for 20 min to obtain a stable oil-in-water emulsion. The above emulsion was transferred to a three-necked flask, the heating temperature was set to 70°C, and the stirring speed was 300 r / min. When the system temperature reached 70°C, 3.5 g of initiator (30% by mass of azobisisobutyronitrile) was added. The reaction was carried out at room temperature for 8 h to obtain organosilicon microgel wellbore enhancer.

[0081] Example 6

[0082] The preparation method of organosilicon microgel wellbore enhancer for ultra-deep well drilling fluids includes the following steps:

[0083] (1) Preparation of vinyl organosilicon nanospheres

[0084] Measure 100 ml of deionized water and add it to a beaker. Then add 1.0 g of emulsifier OS (MS-1) and stir at high speed for 20 min. Add 0.025 g of xanthan gum (XC, acting as a dispersing stabilizer) to the beaker and stir at high speed for 20 min to fully dissolve the xanthan gum. Then weigh 24 g of organosilicon mixed monomers (vinyltriethoxysilane and triethoxysilane in a mass ratio of 1:3), stir and mix evenly at room temperature, and add it to the above beaker. Maintain a stirring speed of 1000 r / min and continue stirring for 20 min. Finally, transfer the above solution system to a three-necked flask and place it in a water bath at 40 °C for 8 h. After the reaction is completed, centrifuge and wash the lower solid phase twice with ethanol and petroleum ether, respectively, to obtain organosilicon nanospheres containing vinyl groups.

[0085] (2) Preparation of organosilicon microgels

[0086] Using the vinyl organosilicon nanospheres prepared in step (1) as the primary micronucleus, and simultaneously selecting functional monomers to graft copolymerize on the surface of the vinyl organosilicon nanospheres to obtain an organosilicon microgel well wall reinforcing agent, the specific method is as follows:

[0087] Measure 120 mL of deionized water into a beaker. Add 1.25 g of Tween 80, 3.5 g of sodium styrene sulfonate, and 0.035 g of crosslinking agent N,N-methylenebisacrylamide to the beaker sequentially. Stir at high speed for 20 min at room temperature to obtain the aqueous phase. Weigh 10 g of butyl acrylate, 3 g of acrylic acid, 5.5 g of vinyl silicone nanospheres, and 0.45 g of Span 80 sequentially into a 50 mL beaker and stir at high speed until homogeneous to obtain the oil phase. Slowly add the oil phase to the aqueous phase while stirring at high speed. Once all the oil phase has been added to the aqueous phase, use a shear emulsifier and stir at 3000 rpm for 20 min to obtain a stable oil-in-water emulsion. The above emulsion was transferred to a three-necked flask, the heating temperature was set to 70°C, and the stirring speed was 300 r / min. When the system temperature reached 70°C, 3.5 g of initiator (30% by mass of azobisisobutyronitrile) was added. The reaction was carried out at room temperature for 8 h to obtain organosilicon microgel wellbore enhancer.

[0088] Example 7

[0089] The preparation method of organosilicon microgel wellbore enhancer for ultra-deep well drilling fluids includes the following steps:

[0090] (1) Preparation of vinyl organosilicon nanospheres

[0091] Measure 100 ml of deionized water and add it to a beaker. Then add 1.0 g of emulsifier OS (MS-1) and stir at high speed for 20 min. Add 0.025 g of xanthan gum (XC, acting as a dispersing stabilizer) to the beaker and stir at high speed for 20 min to fully dissolve the xanthan gum. Then weigh 24 g of organosilicon mixed monomers (vinyltriethoxysilane and triethoxysilane in a mass ratio of 1:3), stir and mix evenly at room temperature, and add it to the above beaker. Maintain a stirring speed of 1000 r / min and continue stirring for 20 min. Finally, transfer the above solution system to a three-necked flask and place it in a water bath at 40 °C for 8 h. After the reaction is completed, centrifuge and wash the lower solid phase twice with ethanol and petroleum ether, respectively, to obtain organosilicon nanospheres containing vinyl groups.

[0092] (2) Preparation of organosilicon microgels

[0093] Using the vinyl organosilicon nanospheres prepared in step (1) as the primary micronucleus, and simultaneously selecting functional monomers to graft copolymerize on the surface of the vinyl organosilicon nanospheres to obtain an organosilicon microgel well wall reinforcing agent, the specific method is as follows:

[0094] Measure 120 mL of deionized water into a beaker. Add 1.25 g of Tween 80, 3.5 g of sodium styrene sulfonate, and 0.035 g of crosslinking agent N,N-methylenebisacrylamide to the beaker sequentially. Stir at high speed for 20 min at room temperature to obtain the aqueous phase. Weigh 10 g of butyl acrylate, 5.5 g of acrylic acid, 4.0 g of vinyl silicone nanospheres, and 0.45 g of Span 80 sequentially into a 50 mL beaker and stir at high speed until homogeneous to obtain the oil phase. Slowly add the oil phase to the aqueous phase while stirring at high speed. Once all the oil phase has been added to the aqueous phase, use a shear emulsifier and stir at 3000 rpm for 20 min to obtain a stable oil-in-water emulsion. The above emulsion was transferred to a three-necked flask, the heating temperature was set to 70°C, and the stirring speed was 300 r / min. When the system temperature reached 70°C, 3.5 g of initiator (30% by mass of azobisisobutyronitrile) was added. The reaction was carried out at room temperature for 8 h to obtain organosilicon microgel wellbore enhancer.

[0095] Comparative Example 1

[0096] The preparation method of the organosilicon microgel wellbore enhancer for ultra-deep well drilling fluid as described in Example 1 differs in that:

[0097] In step (2), sodium styrene sulfonate is not added to the aqueous phase.

[0098] Comparative Example 2

[0099] The preparation method of the organosilicon microgel wellbore enhancer for ultra-deep well drilling fluid as described in Example 1 differs in that:

[0100] In step (2), butyl acrylate is not added to the oil phase.

[0101] Comparative Example 3

[0102] The preparation method of the organosilicon microgel wellbore enhancer for ultra-deep well drilling fluid as described in Example 1 differs in that:

[0103] In step (2), no acrylic acid is added to the oil phase.

[0104] Comparative Example 4

[0105] The preparation method of the organosilicon microgel wellbore enhancer for ultra-deep well drilling fluid as described in Example 1 differs in that:

[0106] In step (2), no vinyl organosilicon microspheres are added to the oil phase.

[0107] Test case

[0108] The organosilicon microgel wellbore enhancers prepared in each embodiment and comparative example were evaluated as follows: their impact on drilling fluid performance, particle size distribution, microporous membrane plugging properties, and wall-binding properties.

[0109] (1) Impact on drilling fluid properties

[0110] Measure 400 mL of clean water and add it to a high-speed stirring cup. Then add 0.56 g of sodium carbonate and stir for 20 min. After that, add 16 g of drilling fluid grade bentonite to the high-speed stirring cup and stir at high speed for 40 min. After stirring at low speed at room temperature for 24 h, a 4% drilling fluid-based slurry is obtained.

[0111] Following the above method, multiple 4% drilling fluid base slurries were prepared. 2% by mass of the organosilicon microgel wellbore enhancer prepared in each example and comparative example was added to the drilling fluid base slurry. The mixture was stirred at room temperature for 40 minutes. The rheological and filtration properties of the drilling fluid were measured using a six-speed rotational viscometer and a medium-pressure filtration meter. Subsequently, each slurry sample was placed in an aging tank and aged at 220°C for 16 hours in a roller furnace. After cooling to room temperature, the rheological and filtration properties of the drilling fluid sample were measured. The test results are shown in Table 1. Both AV (apparent viscosity) and PV (plastic viscosity) reflect the rheological properties of the base slurry.

[0112] Table 1. High-temperature leakage rate results of phase change thermal storage microcapsules

[0113]

[0114]

[0115] Table 1 shows the effects of each example and comparative sample on the rheological and filtration properties of the drilling fluid sample.

[0116] As shown in Table 1, the wellbore enhancers prepared in Examples 1-7 of this invention had virtually no effect on the rheological properties of the base slurry before and after hot rolling at 220℃ for 16 hours, while effectively reducing the API filtration loss of the base slurry. Before hot rolling, the filtration loss was 13-15 mL, and after hot rolling at 240℃, the filtration loss was controlled at 28-31.5 mL, indicating that the wellbore enhancers of this invention have excellent high-temperature dispersion stability and good temperature resistance. However, Comparative Example 1 did not add sodium styrene sulfonate, which affected the hydration characteristics and high-temperature resistance of the wellbore enhancer in water, resulting in weakened clay dispersibility, which in turn caused increased viscosity and filtration loss in the drilling fluid. Comparative Example 2 did not add butyl acrylate, which affected the external encapsulation of the vinyl organosilicon microspheres in reaction step (2), thus weakening the filtration loss reduction effect of the organosilicon microgel on the drilling fluid. Comparative Example 3 did not include acrylic acid, which affected the hydration characteristics of the wellbore enhancer in water, weakening the dispersibility of the clay and consequently causing increased viscosity and filtration loss in the drilling fluid. Comparative Example 4 did not include vinyl organosilicon microspheres, which affected the grafting efficiency of the organic monomers on the surface of the organosilicon microspheres in step (2), thus affecting the particle size distribution of the final material and resulting in poor filtration loss reduction.

[0117] (2) Particle size distribution

[0118] Prepare 400 mL of 2% (mass fraction) aqueous solutions of each sample from the examples and comparative examples, and sonicate at room temperature for 40 min. Use a nanoparticle size potentiometer to determine the particle size distribution of the organosilicon microgels before aging. Then, put the sample solutions into an aging tank and transfer it to a roller furnace for aging at 220°C for 16 h. After aging, cool to room temperature and use a nanoparticle size potentiometer to determine the particle size distribution of the organosilicon microgels in the aged sample solutions. The test results are shown in Table 2.

[0119] Table 2. Particle size distribution of organosilicon microgel wellbore enhancer

[0120]

[0121]

[0122] Table 2 lists the particle size distribution of the examples and comparative samples dispersed in the aqueous phase. As can be seen from the results in Table 2, the wellbore enhancers of Examples 1-7 of the present invention have particle sizes in the nano-microscale (84.3-425.6 nm) and can have good plugging performance for microporous filter membranes of different particle size scales (0.1-1 μm); they have excellent high temperature resistance and still have plugging performance for microporous filter membranes of different particle size scales after aging at 220℃ for 16 h; comparative example 1 did not add xanthan gum, which will affect the size of vinyl organosilicon microspheres in step (1) and affect the size of the final wellbore stabilizer; comparative examples 2 and 3 did not add butyl acrylate and acrylic acid, which reduced the thickness of the outer coating layer of organosilicon microgel and reduced the size of the treatment agent; comparative example 4 did not add vinyl organosilicon nanospheres, which reduced the primary micronucleus particle size and ultimately affected the size of the wellbore stabilizer before and after aging.

[0123] (3) Microporous membrane clogging

[0124] The experiment conducted in this section is a medium-pressure filtration loss experiment. The specific operating steps are as follows:

[0125] 2% (w / w) of each example and comparative sample was added to 400 mL of base slurry. Following the medium-pressure filtration loss test procedure, ordinary drilling fluid filter paper was replaced with polytetrafluoroethylene (PTFE) microporous membranes. The pore sizes of the microporous membranes were 100, 300, 500, and 1000 nm, respectively, and named PTFE-100, PTFE-300, PTFE-500, and PTFE-1000. The sealing performance of the sample solutions on the PTFE microporous membranes was measured. Simultaneously, the sample solutions were aged at 220℃ for 16 h, cooled to room temperature, and the sealing performance of the sample solutions on the PTFE microporous membranes was further measured. The experimental results are shown in Table 3.

[0126] Table 3. Blocking performance of PTFE microporous membranes by sample slurry in various examples and comparative samples.

[0127]

[0128]

[0129] Table 3 shows the effect of aging of aqueous solutions of each example and comparative example on the medium-pressure filtration performance of PTFE microporous membranes with different pore sizes. As shown in Table 3, Example 1 exhibited the best plugging and filtration reduction performance. Comparative Example 4, lacking vinyl organosilicon nanospheres, resulted in a smaller primary micronucleus particle size, ultimately affecting the plugging performance of the wellbore stabilizer on the microporous filter membrane. Comparative Example 1, lacking sodium styrene sulfonate, suffered from weakened dispersibility in water and poorer temperature resistance; therefore, after aging at 220℃ for 16 hours, the filtration loss increased, severely affecting its plugging performance on the microporous filter membrane. Comparative Examples 2 and 3, lacking butyl acrylate and acrylic acid, resulted in a reduced thickness of the outer coating layer of the organosilicon microgel, smaller agent size, and affected its plugging performance; furthermore, the absence of acrylic acid reduced its dispersibility in water, further affecting its plugging performance.

[0130] (4) Bonding and solidifying the wall

[0131] Glass transition temperature determination: The glass transition temperature of each example and comparative sample was tested using a German Netzsch DSC214 differential scanning calorimeter. The test conditions were: temperature range 40℃-300℃, heating rate 10K·min-1, nitrogen as protective gas, and gas flow rate 20.0mL·min-1.

[0132] Compressive strength determination: Select rocks with a clay mineral content greater than 10%, crush the rocks through a 50-mesh sieve, and dry them to constant weight. Weigh 50g of crushed rock, add 5g of the 10% (by mass) aqueous solution of the example or comparative example to the rock, and add 5g of water to the control group. Use a stirrer to stir the solution and rock evenly so that the solution and rock are in full contact. Add the evenly mixed rock to a special core pressing mold and press it for 5min under a pressure of 15±0.2MPa to obtain a core column with a diameter of 25mm. Place the pressed core column in a drying oven and dry it at 80℃ to constant weight and shape. Then raise the temperature of the drying oven to 220℃ and continue aging for 16h. After aging, cool it to room temperature. Finally, use an ETM type electronic universal testing machine to measure the uniaxial compressive strength of the core column. The calculation method of compressive strength is shown in formula (1).

[0133]

[0134] In the formula, Y represents the compressive strength of the core column, in MPa.

[0135] F—Axial stress in the core column, N;

[0136] r — diameter of the core column, mm.

[0137] Table 4. Glass transition temperature and its effect on the compressive strength of rocks for each example and comparative sample.

[0138] sample Glass transition temperature / °C Compressive strength / MPa Cores prepared from the control group / 0.51 Example 1 198.6 4.53 Example 2 195.4 4.47 Example 3 196.8 4.43 Example 4 195.1 4.02 Example 5 186.7 4.02 Example 6 192.4 4.36 Example 7 188.6 4.13 Comparative Example 1 165.4 2.10 Comparative Example 2 154.3 1.84 Comparative Example 3 161.8 2.01 Comparative Example 4 160.3 1.97

[0139] Table 4 shows the glass transition temperature and its effect on rock compressive strength for each example and comparative sample. As shown in Table 4, the sample from Example 1 exhibited the highest glass transition temperature and the highest rate of improvement in rock compressive strength. The increase in rock compressive strength is attributed to the adhesion and consolidation effect of the wellbore strengthener at high temperatures (glass transition temperature). The glass transition temperature is one of the characteristic temperatures of polymers, marking the critical point at which the polymer material transitions from a glassy state to a highly elastic state. Therefore, a suitable glass transition temperature significantly improves the deformation sealing performance of the plugging agent. The core sample from the control group, prepared using water, had a compressive strength of only 0.51 MPa after high-temperature aging. Comparative Example 1, without the addition of sodium styrene sulfonate, had a greater impact on both the glass transition temperature and rock compressive strength because the absence of sodium styrene sulfonate reduced its high-temperature resistance. Comparative Example 2, lacking butyl acrylate (containing flexible segment monomers), significantly weakened the glass transition temperature of the wellbore strengthener and its effect on improving the compressive strength of the prepared rock. This is because polymers with potentially suitable glass transition temperatures typically contain flexible segment monomers, and the required dosage is relatively high. Comparative Example 3, lacking acrylic acid, affected the ratio of flexible segments to rigid structures in the wellbore strengthener, thus affecting the glass transition temperature. Comparative Example 4, lacking vinyl silicone microspheres, affected the polymer's coating on the micro-core surface in step (2) of the reaction.

[0140] Based on the comprehensive evaluation of the above four experiments, it is concluded that the sample of Example 1 has the best sealing and wall-consolidation performance, has a high softening point, is suitable for ultra-deep well drilling operations, and can effectively improve rock cohesion and increase rock strength.

[0141] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing an organic silica microgel borehole strengthening agent for ultra-deep well drilling fluid, comprising the following steps: (1) Preparation of vinyl organic silica nanoballs Add emulsifier a and xanthan gum to deionized water in sequence, and stir at high speed to obtain a mixed solution. Add organic silica mixed monomers to the mixed solution, stir at high speed, and then heat in a water bath for reaction. After reaction, centrifuge the obtained solid phase, and then clean and centrifuge the solid phase with ethanol and petroleum ether to obtain vinyl-containing organic silica nanoballs. The mass / volume ratio of emulsifier a to deionized water is 0.5-2.0:100, in units of g / mL. The mass ratio of xanthan gum to emulsifier a is (0.01-0.04):(0.5-2.0). The organic silica mixed monomers are a mixture of vinyl triethoxysilane and triethoxysilane, and the mass ratio of vinyl triethoxysilane to triethoxysilane is 1:(2-6). The mass ratio of the organic silica mixed monomers to emulsifier a is (20-30):(0.5-2.0). The stirring speed is 800-1500 r / min, the stirring time is 10-30 min, the water bath heating temperature is 30-50°C, and the heating time is 6-12 h. (2) Preparation of the organic silica microgel borehole strengthening agent Use the vinyl-containing organic silica nanoballs prepared in step (1) as primary micro-nuclei, and graft copolymerize functional monomers on the surface of the vinyl-containing organic silica nanoballs to obtain an organic silica microgel borehole strengthening agent. The specific method for graft copolymerization on the surface of the vinyl-containing organic silica nanoballs is as follows: 1) Add emulsifier b, sodium styrene sulfonate, and crosslinking agent N,N-methylenebisacrylamide to deionized water in sequence, and stir at high speed at room temperature to obtain an aqueous phase. Mix butyl acrylate, acrylic acid, the vinyl-containing organic silica nanoballs of step (1), and emulsifier c uniformly to obtain an oil phase. The mass ratio of emulsifier b to sodium styrene sulfonate to crosslinking agent N,N-methylenebisacrylamide is (1.0-2.0):(2-5):(0.02-0.05). The mass / volume ratio of emulsifier b to water is (1.0-2.0):100, in units of g / mL. The mass ratio of butyl acrylate to acrylic acid to the vinyl-containing organic silica nanoballs is (6-11):(3-7):(4-8). Emulsifier c is Span 80. The mass ratio of the vinyl-containing organic silica nanoballs to emulsifier c is (4-8):(0.3-0.7). The stirring speed is 800-1500 r / min, and the stirring time is 10-30 min. 2) Slowly add the oil phase to the aqueous phase and stir at high speed. After the oil phase is completely added to the aqueous phase, stir at high speed to obtain a stable oil-in-water emulsion. Stir and heat the oil-in-water emulsion, add an initiator, and react at room temperature to obtain an organic silica microgel borehole strengthening agent.

2. The production method according to claim 1, characterized by, In step 2), after the oil phase is added into the water phase, a shear emulsifier is used to stir at a high speed of 3000 r / min for 20 min, the stirring and heating temperature is 60-80℃, the stirring speed is 300 r / min, the initiator is 30% azobisisobutyronitrile by mass fraction, and the mass ratio of the vinyl-containing silicone nanometer microspheres to the initiator is (4-8):(2.5-5).

3. A silicone microgel borehole strengthening agent for ultra-deep well drilling fluid, which is prepared by the method of claim 1.

4. Application of the silicone microgel borehole strengthening agent for ultra-deep well drilling fluid of claim 3, which is added into the drilling fluid and used for improving the plugging effect of conventional wells and ultra-deep and super-deep well drilling fluids in oil drilling operations, and the added amount of the strengthening agent is 2%-4% of the weight of the drilling fluid.

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