Lignin-based cementing microcapsule wall-fixing agent for environment-friendly water-based drilling fluid as well as preparation method and application of lignin-based cementing microcapsule wall-fixing agent

Abstract

The invention provides a lignin-based cementing microcapsule wall-fixing agent for environment-friendly water-based drilling fluid as well as a preparation method and application of the lignin-based cementing microcapsule wall-fixing agent, and belongs to the technical field of oilfield chemistry. The preparation method comprises the following steps: firstly, carrying out epoxidation modification on bisphenol A diglycidyl ether, simultaneously introducing polyethylene glycol to obtain an epoxy emulsifier, introducing an epoxy alkyl group to a lignin main chain to obtain LEP, preparing a WLEP emulsion from the LEP and the epoxy emulsifier by adopting a phase inversion method, and finally, packaging the WLEP emulsion by adopting an in-situ polymerization method to obtain the solid wall microcapsule. The microcapsule wall-fixing agent can rapidly permeate into fractured rock stratum apertures due to good rheological property, and hydrogen bonds with relatively strong bond energy are formed between the wall-fixing agent and rock particle surfaces through hydroxyl groups in lignin, so that the mechanical property of well wall rocks is obviously improved, and the rapid and strong adhesion wall-fixing capability of the microcapsule wall-fixing agent after shell breaking is realized; the cementing strength of the wall fixing agent and rock particles is improved, and the well wall stability in the broken rock stratum drilling process is enhanced.

Description

Technical Field

[0001] The invention relates to an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent and a preparation method and application thereof, belonging to the technical field of oilfield chemistry. Background Art

[0002] Wellbore instability accidents have occurred frequently since humans began to exploit oil. The problem of wellbore instability in broken formations has become increasingly prominent, mainly due to the development of micro-cracks and fractures in the formation. During the drilling process, water-based drilling fluids can easily enter the deep formation along the pores and fractures, causing serious wellbore collapse, drill sticking and other accidents, leading to significant economic losses. In recent years, with the rapid development of drilling technology at home and abroad, drilling depths have continued to increase, and the complexity of the formations encountered has gradually increased; at the same time, with the rapid development of the oil industry, the advancement of environmental protection concepts and the promotion of environmental protection, higher requirements have been placed on drilling fluid technology. Therefore, the research and development of high-performance, environmentally friendly water-based drilling fluid additives and systems that can effectively stabilize the wellbore has become the focus of current research.

[0003] Previous researchers have developed some well wall stabilizers that show certain wall-fixing properties. These well wall stabilizers improve the mechanical properties of the well wall rock and prevent the well wall from collapsing by forming adhesive substances on the rock surface and in microcracks. For example, patent document CN106634884A discloses a bionic wall-fixing agent for drilling fluid, which introduces bionic groups with adhesive properties to form a highly adhesive bionic shell on the shale surface, thereby improving the wall-fixing effect. Patent document CN108395529A discloses a modified resin drilling fluid wall-fixing agent. Although this wall-fixing agent can effectively reduce filtration loss and has good biodegradability, no further research has been conducted on its cementing and wall-fixing properties. Patent document CN116063991B discloses an adhesive cementing wall-fixing agent suitable for shale formations. This wall-fixing agent is rapidly cross-linked and cemented to the rock surface under the action of a promoter, thereby improving the cohesive bonding strength between rock microcracks and bedding, thereby achieving the purpose of maintaining well wall stability. However, the three aforementioned wall-fixing agents are dispersed in the drilling fluid system, are easily diluted by the drilling fluid, and form a cementing effect with the solid phase in the drilling fluid system, resulting in low mechanical bonding strength for the broken rock and ineffective wall-fixing. Current research shows that most wall-fixing agents have low mechanical bonding strength for broken rock and poor environmental performance. When used in high-density water-based drilling fluids containing soil phases, they can also lead to increased viscosity, poor bonding performance, and severe pollution.

[0004] In summary, achieving environmentally friendly, strong cementation of rock fractures, and low cost performance in drilling fluids remains a significant challenge. Therefore, there is an urgent need to develop high-performance drilling fluid cementing agents to provide technical support for wellbore stabilization in fractured rock formations. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention provides an environmentally friendly lignin-based cementing microcapsule wall-fixing agent for water-based drilling fluids, as well as its preparation method and application. The invention first epoxidizes bisphenol A diglycidyl ether and simultaneously introduces polyethylene glycol (PEG) of a specific molecular weight as a hydrophilic group and soft segment to produce an epoxy emulsifier (EM). Next, an adhesive (LEP) is produced by introducing cycloalkylene oxide groups into the lignin backbone. A WLEP emulsion is prepared using a phase inversion method with the LEP adhesive and the epoxy emulsifier (EM). The WLEP emulsion is then encapsulated using an in-situ polymerization method to produce mechanically triggered release microcapsules with solid walls. The numerous rigid aromatic benzene rings in the lignin molecular structure enhance the mechanical tensile strength and thermal stability of the resin adhesive. Furthermore, microencapsulation prevents contact between the adhesive and drilling fluid, improving its bonding properties to wellbore pores and fractures. Under the combined action of downhole pressure difference and capillary force, the microcapsules can migrate into the cracks in the well wall, break under the action of stress, release adhesive, and tightly bond the cracks in the well wall.

[0006] The technical solutions of the present invention are as follows: A method for preparing an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent comprises the following steps: (1) Bisphenol A diglycidyl ether (BADGE) and polyethylene glycol (PEG) are mixed evenly, and the temperature is raised to react until the polyethylene glycol is completely melted, a catalyst is added, and the temperature is continued to rise to react; after the reaction is completed, an epoxy emulsifier (EM) is obtained; (2) Alkali lignin, palladium carbon (Pd / C) and ethanol are uniformly mixed and reacted in a H2 atmosphere at a pressure of 2-6 MPa; lignin depolymerization product (PL) is obtained by filtration, washing and drying; (3) The lignin depolymer (PL) is dissolved in epichlorohydrin (ECH), benzyltriethylammonium chloride (TEBAC) is added as a catalyst to react, and then NaOH is added to react; after the reaction is completed, the excess epichlorohydrin is removed by centrifugation and washing to obtain the adhesive LEP; (4) mixing the adhesive LEP prepared in step (3) and the epoxy emulsifier (EM) prepared in step (1), heating the mixture for reaction, cooling the mixture, and then adding deionized water for emulsification to form a WLEP emulsion; (5) adding melamine, urea and formaldehyde solution into deionized water, adjusting the pH of the system to between 8 and 9, and reacting to obtain a prepolymer solution; (6) The emulsifier polyethylene-maleic anhydride (EMA) is mixed with the WLEP emulsion, stirred and emulsified to obtain an oil-in-water emulsion system; the prepolymer solution of step (5) is then added to the oil-in-water emulsion system to react; after the reaction is completed, the lignin-based cemented microcapsule wall-fixing agent for an environmentally friendly water-based drilling fluid is obtained by filtering, washing, and drying.

[0007] According to a preferred embodiment of the present invention, in step (1), the average molecular weight of the polyethylene glycol (PEG) is 800-4000, more preferably 2000.

[0008] According to the present invention, preferably, in step (1), the mass ratio of bisphenol A diglycidyl ether (BADGE) to polyethylene glycol (PEG) is 1:1-6, further preferably, the mass ratio of bisphenol A diglycidyl ether to polyethylene glycol (PEG) is 1:1-4, and most preferably, the mass ratio of bisphenol A diglycidyl ether (BADGE) to polyethylene glycol (PEG) is 1:2.

[0009] According to the preferred embodiment of the present invention, in step (1), after bisphenol A diglycidyl ether (BADGE) and polyethylene glycol (PEG) are uniformly mixed, the temperature of the temperature-raising reaction is 60-110°C, more preferably 90°C.

[0010] According to the preferred embodiment of the present invention, the catalyst in step (1) is concentrated H2SO4 with a mass fraction of 98%; the mass ratio of the catalyst to bisphenol A diglycidyl ether (BADGE) is 0.1-0.5:10.

[0011] According to the preferred embodiment of the present invention, in step (1), after adding the catalyst, the temperature of the reaction is continued to be 100-150°C, more preferably 130°C; after adding the catalyst, the time of the reaction is continued to be 3-6h, more preferably 4h.

[0012] According to the present invention, preferably, in step (2), the mass ratio of the alkaline lignin to palladium carbon (Pd / C) is 160:1-6, further preferably, the mass ratio of the alkaline lignin to palladium carbon (Pd / C) is 160:1-4, and most preferably, the mass ratio of the alkaline lignin to palladium carbon (Pd / C) is 160:3.2; the mass fraction of palladium in the palladium carbon (Pd / C) is 10%.

[0013] According to the present invention, preferably, in step (2), the ratio of the mass of the alkali lignin to the volume of ethanol is 160g:200-300mL, further preferably, the ratio of the mass of the alkaline lignin to the volume of ethanol is 160g:250-300mL, and most preferably, the ratio of the mass of the alkaline lignin to the volume of ethanol is 160g:270mL.

[0014] According to the present invention, preferably, in step (2), the reaction temperature is 200-300°C, more preferably 275°C; The reaction time is 4-8 hours, more preferably 6 hours.

[0015] According to the preferred embodiment of the present invention, the washing in step (2) is performed by washing with ethanol for 2-4 times, and the drying is performed at 50-60° C. to a constant weight.

[0016] According to the present invention, preferably, in step (3), the ratio of the mass of the lignin depolymer to the volume of epichlorohydrin is 100 g:500-1500 mL, further preferably, the ratio of the mass of the lignin depolymer to the volume of epichlorohydrin is 100 g:800-1200 mL, and most preferably, the ratio of the mass of the lignin depolymer to the volume of epichlorohydrin is 100 g:1000 mL.

[0017] According to the present invention, preferably, in step (3), the mass ratio of the lignin depolymerization product to benzyltriethylammonium chloride (TEBAC) is 100:1-6, further preferably, the mass ratio of the lignin depolymerization product to benzyltriethylammonium chloride (TEBAC) is 100:1-3, and most preferably, the mass ratio of the lignin depolymerization product to benzyltriethylammonium chloride (TEBAC) is 100:2.

[0018] According to the preferred embodiment of the present invention, in step (3), the reaction temperature after adding benzyltriethylammonium chloride (TEBAC) is 100-120° C., and the reaction time is 4-6 h.

[0019] According to the present invention, preferably, in step (3), the mass ratio of the lignin depolymerization product to NaOH is 100:26-40, further preferably, the mass ratio of the lignin depolymerization product to NaOH is 100:26-32, and most preferably, the mass ratio of the lignin depolymerization product to NaOH is 100:30; the NaOH is added to the system at 50-70°C.

[0020] According to the preferred embodiment of the present invention, in step (3), after adding NaOH, the reaction temperature is 50-70° C., and the reaction time is 4-6 h.

[0021] According to the preferred embodiment of the present invention, in step (3), the washing is performed by using deionized water until the filtrate is neutral; and the excess epichlorohydrin is removed by distillation under reduced pressure at 100-150°C, more preferably at 120°C.

[0022] According to the present invention, preferably, in step (4), the mass ratio of the adhesive LEP to the epoxy emulsifier is 10:1-8, further preferably, the mass ratio of the adhesive LEP to the epoxy emulsifier is 10:1-5, and most preferably, the mass ratio of the adhesive LEP to the epoxy emulsifier is 10:3.

[0023] According to the preferred embodiment of the present invention, in step (4), the temperature for the reaction between the adhesive LEP and the epoxy emulsifier is 100-160°C, more preferably 140°C.

[0024] According to the preferred embodiment of the present invention, in step (4), the reaction time of the adhesive LEP and the epoxy emulsifier is 3-6 hours, more preferably 4 hours.

[0025] According to the present invention, the cooling in step (4) is preferably cooling to a temperature of 80-100°C, more preferably to 90°C.

[0026] According to the preferred embodiment of the present invention, in step (4), the ratio of the volume of the deionized water to the mass of the adhesive LEP is 20-60 mL:20 g, more preferably 40 mL:20 g; the deionized water is added while stirring at a speed of 500-1000 rpm.

[0027] Preferably, according to the present invention, in step (5), the mass ratio of melamine, urea and formaldehyde solution is 5:1-8:10-16, further preferably, the mass ratio of melamine, urea and formaldehyde solution is 5:1-4:10-14, and most preferably, the mass ratio of melamine, urea and formaldehyde solution is 5:2:12; the mass concentration of the formaldehyde solution is 37wt%.

[0028] Preferably, according to the present invention, in step (5), the ratio of the mass of melamine to the volume of deionized water is 10 g:50-100 mL.

[0029] Preferably, according to the present invention, in step (5), triethanolamine is used to maintain the pH of the system between 8 and 9.

[0030] According to the preferred embodiment of the present invention, in step (5), the reaction temperature is 50-100°C, more preferably 70°C; the reaction time is 1-4h, more preferably 2h; and the stirring speed during the reaction is 200-500rpm, more preferably 300rpm.

[0031] According to the preferred embodiment of the present invention, the ratio of the mass of the emulsifier polyethylene-maleic anhydride (EMA) to the volume of the WLEP emulsion in step (6) is 1-5 g:4-10 mL, and more preferably 1-3 g:5-8 mL.

[0032] Preferably, according to the present invention, in step (6), after the emulsifier polyethylene-maleic anhydride (EMA) is mixed with the WLEP emulsion, the temperature for stirring and emulsifying is 80-100°C; the time for stirring and emulsifying is 1-3 hours, more preferably 1.5 hours; and the stirring speed for stirring and emulsifying is 300-700 rpm, more preferably 500 rpm.

[0033] According to the present invention, preferably, the volume ratio of the prepolymer solution to the WLEP emulsion in step (6) is 1-3:1, more preferably 2:1.

[0034] According to the preferred embodiment of the present invention, the reaction temperature in step (6) is 50-90°C, more preferably 70°C; the reaction time is 2-5h, more preferably 3.5h; and the stirring speed during the reaction is 300-700rpm, more preferably 500rpm.

[0035] According to the present invention, preferably, in step (6), when the prepolymer system and the oil-in-water emulsion system react, a 0.2 mol / L hydrochloric acid solution is used to control the pH value of the system to 4-5, more preferably 4.5-4.8.

[0036] According to the preferred embodiment of the present invention, the washing in step (6) is performed by washing with deionized water for 3-5 times; and the drying is performed at 40-60° C. for 20-30 hours.

[0037] The present invention also provides an environmentally friendly lignin-based cemented microcapsule wall-solidifying agent for water-based drilling fluid, which is prepared by the above-mentioned preparation method.

[0038] According to the present invention, the above-mentioned environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent is used in water-based drilling fluid, and the addition amount of the environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent is 3-6wt%.

[0039] The technical features and beneficial effects of the present invention are as follows: 1. This invention incorporates lignin depolymerization products into epichlorohydrin (ECH) to introduce alkylene oxide groups into the lignin backbone, effectively improving the interfacial compatibility and enhancing the mechanical and thermal properties of lignin-based adhesives. Furthermore, lignin-based epoxy resins cure more quickly than pure bisphenol A (BADGE)-based epoxy resins. The introduction of polyethylene glycol (PEG) of varying molecular weights facilitates the dispersion of the epoxy resin and improves the toughness of the cured adhesive.

[0040] 2. The lignin-based cemented microcapsule wall fixing agent of the present invention is mechanically broken under the action of downhole stress, which delays the release of adhesive and prevents the adhesive from solidifying before entering the rock pores, allowing more adhesive to act on the microcracks and tiny pores of the rock, thereby improving the efficiency of the wall fixing agent.

[0041] 3. The lignin-based cementing microcapsule wall fixing agent of the present invention introduces the hydroxyl group of lignin to form a strong hydrogen bond between the wall fixing agent and the surface of the rock particles, significantly improving the mechanical properties of the well wall rock; the lignin, epoxy group and the polar group of bisphenol A diglycidyl ether (BADGE) form a strong covalent bond, realizing the rapid and strong adhesion and wall fixing ability of the microcapsule wall fixing agent after the shell is broken; the wall fixing agent released after the capsule is broken penetrates into the pores of the porous rock to form a dense cementing network structure, thereby improving the mechanical bonding strength between the wall fixing agent and the rock particles, and effectively improving the well wall stability of the broken rock layer by optimizing the synergistic effect of each monomer. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 IR spectra of the adhesive LEP obtained in Example 1 and the alkali lignin used.

[0043] Figure 2 This is a physical picture of the environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-solidifying agent prepared in Example 1.

[0044] Figure 3 This is a TEM image of the environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-solidifying agent prepared in Example 1. DETAILED DESCRIPTION

[0045] The technical solutions of the present invention are described clearly and completely below with reference to specific embodiments. Obviously, the embodiments described are only a portion of the embodiments of the present invention, and not all of them. The raw materials used in the examples are conventional and commercially available; the methods described are based on prior art unless otherwise specified. All other examples improved or modified by persons of ordinary skill in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0046] The mass fraction of palladium in the palladium carbon (Pd / C) used in the examples is 10%.

[0047] The emulsifier polyethylene-maleic anhydride (EMA) used in the examples has a grafting rate of 1.2% and an average molecular weight of 100,000. Example 1

[0048] A method for preparing an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent comprises the following steps: (1) Add 10 g of bisphenol A diglycidyl ether (BADGE) and 20 g of polyethylene glycol (average molecular weight of 2000) into a three-necked flask, stir evenly, and heat to 90 °C to react until the polyethylene glycol is completely melted; then raise the temperature to 130 °C, and drop 0.3 g of 98% H2SO4 as a catalyst (drop rate of 1 mL / min). After the addition is completed, react at 130 °C for 4 h. After the reaction is completed, epoxy emulsifier (EM) is obtained.

[0049] (2) 160 g of alkali lignin, 3.2 g of palladium carbon (Pd / C) and 270 mL of ethanol were added to an autoclave equipped with a magnetic stirrer. When the atmosphere in the autoclave was completely replaced by H2, the pressure was increased and maintained at 4.5 MPa. The temperature was raised to 275 °C and the reaction was continuously stirred at a speed of 800 rpm for 6 h. After the reaction was completed, the solid was filtered and washed three times with ethanol. It was then dried at 50 °C to constant weight to obtain lignin depolymerization product (PL).

[0050] (3) 100 g of lignin depolymer (PL) was dissolved in 1000 mL of epichlorohydrin (ECH), 2 g of benzyltriethylammonium chloride (TEBAC) was added as a catalyst, and the mixture was reacted at 110 °C for 5 hours; then, the mixture was cooled to 60 °C, 30 g of solid NaOH was added, and the mixture was reacted at 60 °C for 5 hours; after the reaction was completed, the mixture was centrifuged, and the precipitate was washed with deionized water until the filtrate was neutral. The excess epichlorohydrin was removed by reduced pressure distillation at 120 °C to obtain the adhesive LEP; (4) 20 g of the adhesive LEP obtained in step (3) and 6 g of the epoxy emulsifier (EM) obtained in step (1) were added to a three-necked flask and stirred at 140°C for 4 h; then the system was cooled to 90°C and 40 mL of deionized water was added at a speed of 800 rpm for emulsification to form a WLEP emulsion; (5) 5 g of melamine (M), 2 g of urea (U) and 12 g of formaldehyde solution (concentration of 37 wt%, F) were added to 80 mL of deionized water, and triethanolamine was then added to maintain the pH of the system between 8 and 9. The reaction was carried out at 70 °C and 300 rpm for 70 min to obtain a MUF prepolymer solution. (6) 9 g of emulsifier polyethylene-maleic anhydride (EMA) was uniformly mixed with 15 mL of the WLEP emulsion obtained in step (4) and then transferred to a flask. The mixture was stirred and emulsified at 90°C and a stirring speed of 500 rpm for 1.5 hours to emulsify the entire system into tiny oil droplets, forming a uniformly dispersed water-in-oil emulsion system. Subsequently, 30 mL of the MUF prepolymer system obtained in step (5) was added to the above-mentioned water-in-oil emulsion system and reacted at 70°C and a stirring speed of 500 rpm for 3.5 hours. During the reaction, 0.2 mol / L hydrochloric acid solution was used to control the pH of the system between 4.5 and 4.8. After the reaction, the precipitate was filtered and washed with deionized water three times. It was then dried at 50°C for 24 hours to obtain microcapsules-WLEP@MUF, which is an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent A1.

[0051] The infrared spectrum of LEP obtained in this example is as follows Figure 1 As shown by Figure 1 It can be seen that at 798cm -1 , 850cm -1 An absorption peak appears near 1241cm, which is caused by the stretching vibration of the C-Cl bond in the molecule. It can be confirmed that there is a chlorinated structure, that is, the chlorohydroxyl structure (-CH(OH)CH2Cl) is successfully introduced; -1 There is an absorption peak near 1319cm, which is caused by the asymmetric stretching vibration of COC in the molecule, confirming the introduction of epoxy group (-CH(O)CH-); -1 、1427cm -1 There is an absorption peak near 3277cm, which is caused by the bending vibration of the CH bond in the molecule; -1 、3512cm -1 An absorption peak appears near the epoxidation site, which is attributed to the stretching vibration of the new hydroxyl (OH) group generated after the epoxy ring opens. The above results indicate that the new target functional group has been successfully introduced into the alkali lignin, and the epoxidation modification of lignin is successful.

[0052] The physical picture of the environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent obtained in this embodiment is as follows: Figure 2 As shown in the TEM image Figure 3 As shown, through Figure 3 It can be seen that the obtained wall-solidifying agent is a microcapsule structure. Example 2

[0053] A method for preparing an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent is as described in Example 1, except that the molecular weight of the polyethylene glycol added in step (1) is 800, thereby obtaining an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent A2. Example 3

[0054] A method for preparing an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent is as described in Example 1, except that the molecular weight of the polyethylene glycol added in step (1) is 4000, thereby obtaining an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent A3. Example 4

[0055] A method for preparing an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent is as described in Example 1, except that the mass of polyethylene glycol (average molecular weight of 2000) in step (1) is 40 g, and an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent A4 is obtained. Example 5

[0056] A method for preparing an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent is as described in Example 1, except that the mass of palladium carbon (Pd / C) in step (2) is 4 g, and an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent A5 is obtained. Example 6

[0057] A method for preparing an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent is as described in Example 1, except that in step (3), the mass of benzyltriethylammonium chloride (TEBAC) is 3 g, and the mass of solid NaOH is 32 g, thereby obtaining an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent A6. Example 7

[0058] A method for preparing an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent is as described in Example 1, except that in step (4), the mass of the epoxy emulsifier (EM) is 10 g and the volume of deionized water is 60 mL, thereby obtaining an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent A7. Example 8

[0059] A method for preparing an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent is as described in Example 1, except that the mass of the emulsifier polyethylene-maleic anhydride (EMA) in step (6) is 6 g, and an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent A8 is obtained. Example 9

[0060] A method for preparing an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent is as described in Example 1, except that in step (5), the mass of melamine (M) is 5 g, the mass of urea (U) is 2 g, and the mass of formaldehyde solution (concentration of 37 wt%, F) is 12 g, thereby obtaining an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent A9. Comparative Example 1

[0061] A method for preparing a wall-fixing agent is as described in Example 1, except that the catalyst added in step (3) is tetrabutylammonium hydrogen sulfate, to obtain a wall-fixing agent B1. Comparative Example 2

[0062] A method for preparing a wall-fixing agent is as described in Example 1, except that dealkalized lignin is added in step (2) to obtain a wall-fixing agent B2. Comparative Example 3

[0063] A method for preparing a wall-fixing agent is as described in Example 1, except that the encapsulation process of step (5) and step (6) is not performed, and WLEP emulsion is obtained as the wall-fixing agent B3. Test Example 1

[0064] The wall-solidifying agents prepared in the examples and comparative examples were evaluated for their performance as follows: 1. Test of the bonding strength of wall solidifier on rock Lap shear strength test: According to the "Determination of tensile shear strength of adhesives" (GB7124-2008) and the "Determination of chemical resistance of adhesives" (GB / T13353-92), a 2% by mass aqueous solution of a wall-fixing agent was evenly applied to the single lap joint surface of an artificial lap joint specimen (rock slice) (the blank control group was treated with clean water). The lap joint specimen was pressed under 10 MPa for 2 hours, then immersed in air and water at 50°C for 24 hours. Then, a tensile force was applied parallel to the lap joint surface and in the direction of the specimen's principal axis to test the maximum load that the specimen could withstand in air and water. Test of cementation compressive strength: add 20g of wall solidifying agent to 80mL of water, stir at a speed of 4000r / min for 20min, age at 150℃ for 16h, take 10mL of the aged solution and slowly add it to 90g of shale powder passing through a 100-mesh sieve, stir at a speed of 100r / min for 20min, so that the wall solidifying agent and the powder of the broken rock formation are evenly mixed (the water treatment is the blank control group). The above mixture is loaded into a mold, pressed at a pressure of 10MPa for 20min, and pressed into a core column with a height of 10cm and a diameter of 1cm. Two copies of the above core column are prepared, one is directly tested for uniaxial compressive strength, and the other is dried in an oven at 100℃ to constant weight and then subjected to uniaxial compressive strength test; The test results are shown in Table 1.

[0065] Table 1 Test on the cementing strength of rock by adding the wall-fixing agent prepared in the examples and comparative examples

[0066] From the test results in Table 1, it can be seen that compared with clear water, the lap shear strength and uniaxial compressive strength of the rock after treatment with the wall fixing agent are significantly improved. Among them, the wall fixing agent in Example 1 has the best bonding performance for rocks: the lap shear strength in air is 2.376MPa, and the shear strength in water is 1.957MPa; the uniaxial compressive strength of the core before drying is 2.441MPa, and the uniaxial compressive strength after drying is 5.762MPa. Example 2 and Example 3 are lignin-based cementing microcapsule wall fixing agents prepared using polyethylene glycol with a molecular weight of 800 and polyethylene glycol with a molecular weight of 4000, respectively. Compared with Example 1, the bonding strength of Examples 2 and 3 to rocks is reduced. As the molecular weight of polyethylene glycol increases from 800 to 2000, the extension and cross-linking of its chain increase, and the flexible polyethylene glycol chain is conducive to the dissipation of polymer energy, and its bonding performance will also be enhanced. However, since the epoxy groups in bisphenol A diglycidyl ether are limited, when the molecular weight is 2000 polyethylene glycol and bisphenol A diglycidyl ether have an optimal crosslinking density, when the molecular weight of polyethylene glycol is 4000g / mol, excessive crosslinking is not conducive to the fluidity of the adhesive and reduces the bonding strength. Therefore, this environmentally friendly lignin-based cementing microcapsule wall-fixing agent realizes that its bonding performance and thermal performance can be effectively adjusted by controlling the length of the polyethylene glycol chain. The phase catalyst used in Comparative Example 1 is tetrabutylammonium hydrogen sulfate, which reduces the amount of propylene oxide on the lignin main chain in the reaction product, causing it to react incompletely with subsequent bisphenol A diglycidyl ether, resulting in its adhesive properties becoming worse. The lignin used in Comparative Example 2 is dealkalized lignin, which also reduces its adhesive properties. Because dealkalized lignin contains fewer reactive sites (primarily hydroxyl groups), it cannot fully react with epichlorohydrin and bisphenol A diglycidyl ether. The wall-fixing agent formed under these conditions does not exhibit strong bonding properties for broken rock formations. Alkaline lignin is decomposed into smaller, more reactive monomers with a higher hydroxyl content. At the same time, as a polymer with a rigid benzene ring structure, the increased total hydroxyl content of lignin provides more reactive sites for reactions with epichlorohydrin and bisphenol A diglycidyl ether, which helps to increase the crosslinking density of the entire system, thereby improving the mechanical tensile properties of the material to a certain extent. This allows the synthesized adhesive to easily penetrate deep into porous rock to form a dense bonding network structure, significantly improving the adhesive properties of the wall-fixing agent in broken rock formations. In Comparative Example 3, the lignin-based adhesive was not encapsulated, and the adhesive was completely dispersed in the drilling fluid, reducing its adhesive properties. In Example 1, the adhesive is encapsulated so that the microcapsules containing the adhesive enter the cracks and break under the action of stress, completing the curing process of the adhesive in the cracks of the rock, thereby greatly improving the efficiency of the adhesive.

[0067] 2. Effect of wall solidifier on rheological and filtration properties of base slurry before and after aging 4% base slurry preparation: add 16g bentonite and 0.56g anhydrous sodium carbonate to 400mL water, stir thoroughly at 8000rpm at room temperature for 2h, seal and let stand at room temperature for 24h; Drilling fluid preparation: Take 400 mL of 4% bentonite-based slurry, add 8 g of the prepared wall-fixing agent, and stir at 6000 r / min for 20 min; Drilling fluid aging: The drilling fluid samples were placed in a roller furnace at an aging temperature of 150°C for 16 h. The rheological and filtration properties of the drilling fluids were tested according to the American Petroleum Institute (API) standard (API RP 13B 1, 2009). The test results are shown in Table 2.

[0068] Table 2 Rheological and filtration performance data of drilling fluids obtained by adding wall-fixing agents prepared in Examples and Comparative Examples

[0069] The test results in Table 2 show that the addition of the environmentally friendly cementitious wall-fixing agent prepared in Example 1 significantly improved the apparent viscosity (AV), plastic viscosity (PV), and dynamic shear force (YP) of the drilling fluid before and after aging. A strong physical bond and dense structural layer formed on the surface of the clay particles, improving the rheological properties of the drilling fluid and enhancing the density of the mud cake, thereby reducing the filtration vector of the drilling fluid. However, the rheological properties of all comparative examples deteriorated to varying degrees, and the fluid loss reduction effect was also reduced to a certain extent.

[0070] In summary, the environmentally friendly lignin-based cemented microcapsule wall-fixing agent for water-based drilling fluids prepared in this invention maintains excellent wall-fixing capabilities even after aging at high temperature (150°C), effectively enhancing the stability of the wellbore in fractured rock formations during drilling. Furthermore, it has a certain filtration loss reduction effect on drilling fluids.

[0071] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0072] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0073] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent, characterized in that: The steps are as follows: (1) Bisphenol A diglycidyl ether and polyethylene glycol are uniformly mixed, and the temperature is raised to react until the polyethylene glycol is completely melted, a catalyst is added, and the temperature is continued to be raised to react; after the reaction is completed, an epoxy emulsifier is obtained; the mass ratio of the bisphenol A diglycidyl ether to the polyethylene glycol is 1:1-6; the catalyst is concentrated H2SO4 with a mass fraction of 98%; the mass ratio of the catalyst to the bisphenol A diglycidyl ether is 0.1-0.5:10; (2) Alkali lignin, palladium carbon and ethanol are uniformly mixed and reacted in a H2 atmosphere at a pressure of 2-6 MPa; lignin depolymerization products are obtained by filtration, washing and drying; the mass ratio of alkali lignin to palladium carbon is 160:1-6; the mass ratio of alkali lignin to ethanol is 160 g:200-300 mL; (3) dissolving the lignin depolymer in epichlorohydrin, adding benzyltriethylammonium chloride as a catalyst to react, and then adding NaOH to react; after the reaction is completed, the excess epichlorohydrin is removed by centrifugation and washing to obtain the adhesive LEP; the mass ratio of the lignin depolymer to the volume of epichlorohydrin is 100g:500-1500mL; the mass ratio of the lignin depolymer to benzyltriethylammonium chloride is 100:1-6; the mass ratio of the lignin depolymer to solid NaOH is 100:26-40; (4) The adhesive LEP of step (3) and the epoxy emulsifier prepared in step (1) are mixed and heated for reaction. After cooling, deionized water is added for emulsification to form a WLEP emulsion; the mass ratio of the adhesive LEP to the epoxy emulsifier is 10:1-8; the volume ratio of the deionized water to the mass of the adhesive LEP is 20-60 mL:20 g; (5) Adding melamine, urea and formaldehyde solution to deionized water, adjusting the pH of the system to between 8 and 9, and reacting to obtain a prepolymer solution; the mass ratio of melamine, urea and formaldehyde is 5:1-8:10-16; the mass ratio of melamine to deionized water is 10 g:50-100 mL; (6) The emulsifier polyethylene-maleic anhydride is mixed with the WLEP emulsion, stirred and emulsified to obtain an oil-in-water emulsion system; the prepolymer solution of step (5) is then added to the oil-in-water emulsion system to react; after the reaction is completed, the mixture is filtered, washed, and dried to obtain an environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall solidifying agent; the mass ratio of the emulsifier polyethylene-maleic anhydride to the volume of the WLEP emulsion is 1-5 g:4-10 mL; the volume ratio of the prepolymer solution of step (5) to the WLEP emulsion is 1-3:

1.

2. The method for preparing the environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent according to claim 1, characterized in that: The average molecular weight of the polyethylene glycol in step (1) is 800-4000; the mass ratio of bisphenol A diglycidyl ether to polyethylene glycol is 1:1-4; after bisphenol A diglycidyl ether and polyethylene glycol are evenly mixed, the temperature of the temperature-raising reaction is 60-110° C.; after the catalyst is added, the temperature of the temperature-raising reaction is continued to be 100-150° C.; after the catalyst is added, the time of the temperature-raising reaction is continued to be 3-6 hours.

3. The method for preparing the environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent according to claim 1, characterized in that: In step (2), the mass ratio of alkali lignin to palladium carbon is 160:1-4; the mass fraction of palladium in the palladium carbon is 10%; the mass ratio of alkali lignin to ethanol volume is 160g:250-300mL; The reaction temperature is 200-300° C.; the reaction time is 4-8 h; the washing is performed using ethanol for 2-4 times; and the drying is performed at 50-60° C. to a constant weight.

4. The method for preparing the environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent according to claim 1, characterized in that: In step (3), the mass ratio of the lignin depolymerized product to the volume of epichlorohydrin is 100 g:800-1200 mL; the mass ratio of the lignin depolymerized product to benzyltriethylammonium chloride is 100:1-3; the reaction temperature after adding benzyltriethylammonium chloride is 100-120° C., and the reaction time is 4-6 h; The mass ratio of lignin depolymerization product to NaOH is 100:26-32, and the NaOH is added to the system at 50-70°C. After the addition of NaOH, the reaction temperature is 50-70°C, and the reaction time is 4-6 hours. The washing is performed using deionized water until the filtrate is neutral. Excess epichlorohydrin is removed by reduced pressure distillation at 100-150°C.

5. The method for preparing the environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent according to claim 1, characterized in that: In step (4), the mass ratio of the adhesive LEP to the epoxy emulsifier is 10:1-5; The temperature for the reaction of the adhesive LEP and the epoxy emulsifier is 100-160° C.; the reaction time of the adhesive LEP and the epoxy emulsifier is 3-6 hours; the cooling is cooling to a temperature of 80-100° C.; The volume ratio of the deionized water to the mass of the adhesive LEP is 40 mL:20 g; the deionized water is added while stirring at a speed of 500-1000 rpm.

6. The method for preparing the environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent according to claim 1, characterized in that: In step (5), the mass ratio of melamine, urea and formaldehyde solution is 5:1-4:10-14; the mass concentration of the formaldehyde solution is 37wt%; In step (5), triethanolamine is used to maintain the pH of the system between 8 and 9; the reaction temperature is 50-100° C.; the reaction time is 1-4 h; and the stirring speed during the reaction is 200-500 rpm.

7. The method for preparing the environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent according to claim 1, characterized in that: The ratio of the mass of the emulsifier polyethylene-maleic anhydride to the volume of the WLEP emulsion in step (6) is 1-3 g:5-8 mL; after the emulsifier polyethylene-maleic anhydride is mixed with the WLEP emulsion, the temperature for stirring and emulsifying is 80-100° C.; the time for stirring and emulsifying is 1-3 hours; and the stirring speed for stirring and emulsifying is 300-700 rpm.

8. The method for preparing the environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent according to claim 1, characterized in that: The volume ratio of the prepolymer solution to the WLEP emulsion in step (6) is 2:1; The reaction temperature is 50-90°C; the reaction time is 2-5 hours; the stirring speed during the reaction is 300-700 rpm; when the prepolymer system and the water-in-oil emulsion system react, a 0.2 mol / L hydrochloric acid solution is used to control the pH value of the system to 4-5; the washing is performed using deionized water for 3-5 times; and the drying is performed at 40-60°C for 20-30 hours.

9. An environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent, characterized in that: The preparation method is described in any one of claims 1 to 8.

10. Use of the environmentally friendly water-based drilling fluid lignin-based cemented microcapsule wall-fixing agent according to claim 9 in water-based drilling fluid, characterized in that: The addition amount of the lignin-based cemented microcapsule wall-solidifying agent for the environmentally friendly water-based drilling fluid is 3-6 wt %.

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