Cationic graft copolymer flocculant for water-based waste drilling fluid and preparation method thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA NAT PETROLEUM CORP
- Filing Date
- 2022-08-09
- Publication Date
- 2026-06-23
Abstract
Description
Technical Field
[0001] This invention belongs to the field of drilling fluid technology in the petroleum industry, specifically relating to a cationic graft copolymer flocculant for water-based waste drilling fluid and its preparation method. Background Technology
[0002] Drilling fluid is one of the key fluids for maintaining formation pressure balance, wellbore stability, drill cuttings suspension and carrying, and drill bit cooling. During the drilling process, each oil and gas well generates more than 150-300 cubic meters of waste drilling fluid. 3 The treatment of waste drilling fluid is challenging. With my country's increasing emphasis on building a resource-saving and environmentally friendly society, the effective treatment of waste drilling fluid has become a key research focus.
[0003] Currently, waste drilling fluid treatment technologies include thermal treatment, reinjection, microbial treatment, and chemically enhanced solid-liquid separation. Thermal treatment primarily aims to decompose pollutants through high-temperature incineration. However, in practice, this method is gradually being phased out due to the high temperatures required for incineration and the potential for generating new pollutants. Reinjection cannot effectively eliminate pollutants, and its high cost limits its widespread application in waste drilling fluid treatment both domestically and internationally. Microbial treatment involves cultivating and introducing degrading bacteria to degrade waste drilling fluid. However, due to the relatively high selectivity of bacterial strains and the complex composition of waste drilling fluid, it is difficult to guarantee the full effectiveness of microbial degradation, and its applicability needs improvement. Chemically enhanced solid-liquid separation is one of the core technologies for treating waste drilling fluid at present. The application of chemically enhanced solid-liquid separation technology can achieve the separation of the two phases of well fluid. By flocculating the suspended matter in waste drilling mud, the solid and liquid phases of drilling mud can be effectively separated. Some researchers have used orange peel and grapefruit peel for flocculation treatment and found that under the premise of 40℃, the optimal flocculation effect can be obtained by controlling the addition of these two flocculants at about 3%. However, the removal rate of suspended matter is still not very high. Therefore, there is an urgent need to provide a flocculant with a high removal rate of suspended matter. Summary of the Invention
[0004] To address the above-mentioned problems, the present invention aims to provide a cationic graft copolymer flocculant for water-based waste drilling fluid with high suspended solids removal rate and its preparation method.
[0005] To achieve the above objectives, the present invention provides the following technical solution:
[0006] This invention discloses a method for preparing a cationic graft copolymer flocculant for water-based waste drilling fluid, the specific steps of which are as follows:
[0007] (1) Synthesis of nano-crosslinking agent: γ-methacryloxypropyltrimethoxysilane was added to a mixture containing ethanol and water, followed by the addition of nanocellulose crystals. The mixture was placed in a water bath for reaction, and the resulting product was processed to obtain the nano-crosslinking agent.
[0008] (2) Gelatinization of starch: After heating deionized water and starch to gelatinize, cool and set aside.
[0009] (3) Synthesis of graft copolymer: N,N-diethylacrylamide, nano-crosslinking agent, hydrophobic monomer, cationic polymerizing monomer, emulsifier and initiator are slowly added to the gelatinized starch to carry out the reaction. The product obtained from the reaction is processed to obtain a cationic graft copolymer flocculant for water-based waste drilling fluid.
[0010] Furthermore, the specific process of step (1) is as follows:
[0011] γ-methacryloxypropyltrimethoxysilane was measured and added to a three-necked flask containing a mixture of ethanol and water. The mixture was stirred at low speed at room temperature for 2-4 hours. Then, nanocellulose crystals were added to the three-necked flask and placed in a water bath at 35-45℃ and 75-150 r / min for 10-15 hours. The resulting product was centrifuged, washed several times with anhydrous ethanol, and dried to constant weight to obtain the nano-crosslinking agent.
[0012] Further, in step (1), the volume ratio of γ-methacryloxypropyltrimethoxysilane to the mixture containing ethanol and water is 1:(8-12), the volume ratio of water to ethanol is 1:(2-4), and the amount of nanocellulose crystals added per 10 mL of γ-methacryloxypropyltrimethoxysilane is 10-15 g.
[0013] Furthermore, the specific process of step (2) is as follows:
[0014] Add deionized water and starch to a four-necked flask equipped with a stirrer, condenser and thermometer. Raise the temperature to 70-90℃ and gelatinize for 20-35 minutes. After gelatinization, cool to 50-60℃ and set aside.
[0015] Furthermore, in step (2), the mass ratio of deionized water to starch is 20:(1-2).
[0016] Furthermore, the specific process of step (3) is as follows:
[0017] N,N-diethylacrylamide, nano-crosslinking agent, hydrophobic monomer, cationic polymerizing monomer, emulsifier, and 5% (w / w) initiator were slowly added to the gelatinized starch. The stirring speed was set to 150-250 r / min, nitrogen gas was purged for 15-30 min, and the reaction was carried out at 50-60℃ for 3-5 h. After the reaction was completed, the mixture was naturally cooled to room temperature. The product was precipitated with acetone, filtered, and washed. Then it was dried at 80℃ to constant weight, pulverized, and sieved to obtain a cationic graft copolymer flocculant for water-based waste drilling fluid.
[0018] Further, in step (3), the mass ratio of starch, N,N-diethylacrylamide, nano-crosslinking agent, hydrophobic monomer, cationic polymerizing monomer, emulsifier and initiator with a mass fraction of 5% is (10-20): (5-10): (4-7): (1-4): (8-16): (0.5-2): (1-3).
[0019] Furthermore, in step (2), the starch is one of corn starch, tapioca starch, or potato starch, and the average molecular weight of the starch is 50,000-80,000.
[0020] Furthermore, in step (3), the cationic polymerization monomer is two of the following: acryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, ethyl methacrylate trimethyl ammonium chloride, and acryloyloxyethyl trimethyl ammonium chloride.
[0021] Furthermore, in step (3), the hydrophobic monomer is one of ethyl butyrate, butyl acrylate, and ethyl acetate.
[0022] Furthermore, in step (3), the emulsifier is one of emulsifier OP-4, emulsifier OP-10, or Tween 60.
[0023] Furthermore, in step (3), the initiator is one or two of potassium persulfate, sodium bisulfite, benzoyl peroxide, diisopropylbenzene peroxide, and dodecyl peroxide.
[0024] The present invention also discloses a cationic graft copolymer flocculant for water-based waste drilling fluid prepared by the above preparation method.
[0025] The beneficial effects of this invention are as follows:
[0026] This invention synthesizes a water-based cationic graft copolymer flocculant for waste drilling fluid using starch, acrylamide, and cationic monomers via a graft copolymerization reaction. This flocculant exhibits excellent performance; it can interact with suspended solids in waste drilling mud through adsorption bridging and electrostatic attraction, effectively causing the suspended solids to settle and achieving effective solid-liquid separation. Its specific advantages are as follows:
[0027] Advantage 1: The synthesis of nano-crosslinking agents can cause micro-crosslinking between flocculant monomers, generating a certain spatial network structure, thereby increasing the flocculation effect of flocculants on water-based drilling fluid waste.
[0028] Advantage 2: The developed cationic graft copolymer flocculant for water-based waste drilling fluid contains positively charged active groups and polar groups, which can generate charge neutralization and hydrogen bonding with waste particles in the drilling fluid, effectively flocculating water-based drilling fluid waste.
[0029] Advantage 3: The developed water-based waste drilling fluid cationic graft copolymer flocculant, at an addition of 0.2%, achieved a CODcr removal rate of 90.9% for waste drilling mud, with residual turbidity of 15.3 NTU and suspended solids of 94.3%.
[0030] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description and claims. Specific Implementation
[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0032] Example 1
[0033] A method for preparing a cationic graft copolymer flocculant for water-based waste drilling fluid, the specific steps of which are as follows:
[0034] (1) Synthesis of nano-crosslinking agent: 10 mL of γ-methacryloxypropyltrimethoxysilane (KH570) was added to a three-necked flask containing 100 mL of a mixture of ethanol and water (ethanol to water volume ratio of 7:3). The mixture was stirred at room temperature for 3 h. Then, 12 g of nano-cellulose crystals were added to the three-necked flask, and the mixture was placed in a water bath at 40 °C and 100 r / min for 12 h. The resulting product was centrifuged, washed several times with anhydrous ethanol, and dried to constant weight to obtain the nano-crosslinking agent.
[0035] (2) Gelatinization of starch: Add 200 mL of deionized water and 12 g of corn starch to a four-necked flask equipped with a stirrer, condenser and thermometer. Raise the temperature to 80 °C and gelatinize for 30 min. After gelatinization, cool to 55 °C.
[0036] (3) Synthesis of graft copolymer: 7g N,N-diethylacrylamide, 5.5g nano-crosslinking agent, 3g butyl acrylate, 5g acryloyloxyethyl dimethyl benzyl ammonium chloride, 7g methacryloyloxyethyl trimethyl ammonium chloride, 1g emulsifier OP-10 and 1.5g potassium persulfate with a mass fraction of 5% were slowly added to the four-necked flask in (2) above. The stirring speed was set to 200r / min, nitrogen gas was purged for 20min, and the reaction was carried out at 55℃ for 4h. After the reaction was completed, the product was naturally cooled to room temperature. The product was precipitated with acetone, filtered and washed, and then dried at 80℃ to constant weight. It was then crushed and passed through a 100-mesh sieve to obtain a cationic graft copolymer flocculant for water-based waste drilling fluid.
[0037] In this mixture, butyl acrylate is a hydrophobic monomer, acryloyloxyethyl dimethyl benzyl ammonium chloride and methacryloyloxyethyl trimethyl ammonium chloride are cationic polymerization monomers, and potassium sulfate is an initiator.
[0038] Example 2
[0039] A method for preparing a cationic graft copolymer flocculant for water-based waste drilling fluid, the specific steps of which are as follows:
[0040] (1) Synthesis of nano-crosslinking agent: 10 mL of γ-methacryloxypropyltrimethoxysilane (KH570) was added to a three-necked flask containing 100 mL of a mixture of ethanol and water (ethanol to water volume ratio of 7:3). The mixture was stirred at room temperature for 3 h. Then, 12 g of nano-cellulose crystals were added to the three-necked flask, and the mixture was placed in a water bath at 40 °C and 100 r / min for 12 h. The resulting product was centrifuged, washed several times with anhydrous ethanol, and dried to constant weight to obtain the nano-crosslinking agent.
[0041] (2) Gelatinization of starch: Add 200mL of deionized water and 18g of corn starch to a four-necked flask equipped with a stirrer, condenser and thermometer. Raise the temperature to 80℃ and gelatinize for 30min. After gelatinization, cool to 55℃.
[0042] (3) Synthesis of graft copolymer: 7g N,N-diethylacrylamide, 5.5g nano-crosslinking agent, 3g butyl acrylate, 5g acryloyloxyethyl dimethyl benzyl ammonium chloride, 7g methacryloyloxyethyl trimethyl ammonium chloride, 1g emulsifier OP-10 and 1.5g potassium persulfate with a mass fraction of 5% were slowly added to the four-necked flask in (2) above. The stirring speed was set to 200r / min, nitrogen gas was purged for 20min, and the reaction was carried out at 55℃ for 4h. After the reaction was completed, the product was naturally cooled to room temperature. The product was precipitated with acetone, filtered and washed, and then dried at 80℃ to constant weight. It was then crushed and passed through a 100-mesh sieve to obtain a cationic graft copolymer flocculant for water-based waste drilling fluid.
[0043] Example 3
[0044] A method for preparing a cationic graft copolymer flocculant for water-based waste drilling fluid, the specific steps of which are as follows:
[0045] (1) Synthesis of nano-crosslinking agent: 10 mL of γ-methacryloxypropyltrimethoxysilane (KH570) was added to a three-necked flask containing 100 mL of a mixture of ethanol and water (ethanol to water volume ratio of 7:3). The mixture was stirred at room temperature for 3 h. Then, 12 g of nano-cellulose crystals were added to the three-necked flask, and the mixture was placed in a water bath at 40 °C and 100 r / min for 12 h. The resulting product was centrifuged, washed several times with anhydrous ethanol, and dried to constant weight to obtain the nano-crosslinking agent.
[0046] (2) Gelatinization of starch: Add 200 mL of deionized water and 12 g of corn starch to a four-necked flask equipped with a stirrer, condenser and thermometer. Raise the temperature to 80 °C and gelatinize for 30 min. After gelatinization, cool to 55 °C.
[0047] (3) Synthesis of graft copolymer: 7g N,N-diethylacrylamide, 7g nano-crosslinking agent, 3g butyl acrylate, 5g acryloyloxyethyl dimethyl benzyl ammonium chloride, 7g methacryloyloxyethyl trimethyl ammonium chloride, 1g emulsifier OP-10 and 1.5g potassium persulfate with a mass fraction of 5% were slowly added to the four-necked flask in (2) above. The stirring speed was set to 200r / min, nitrogen gas was purged for 20min, and the reaction was carried out at 55℃ for 4h. After the reaction was completed, the product was naturally cooled to room temperature. The product was precipitated with acetone, filtered and washed, and then dried at 80℃ to constant weight. It was then crushed and passed through a 100-mesh sieve to obtain a cationic graft copolymer flocculant for water-based waste drilling fluid.
[0048] Example 4
[0049] A method for preparing a cationic graft copolymer flocculant for water-based waste drilling fluid, the specific steps of which are as follows:
[0050] (1) Synthesis of nano-crosslinking agent: 10 mL of γ-methacryloxypropyltrimethoxysilane (KH570) was added to a three-necked flask containing 100 mL of a mixture of ethanol and water (ethanol to water volume ratio of 7:3). The mixture was stirred at room temperature for 3 h. Then, 12 g of nano-cellulose crystals were added to the three-necked flask, and the mixture was placed in a water bath at 40 °C and 100 r / min for 12 h. The resulting product was centrifuged, washed several times with anhydrous ethanol, and dried to constant weight to obtain the nano-crosslinking agent.
[0051] (2) Gelatinization of starch: Add 200 mL of deionized water and 12 g of corn starch to a four-necked flask equipped with a stirrer, condenser and thermometer. Raise the temperature to 80 °C and gelatinize for 30 min. After gelatinization, cool to 55 °C.
[0052] (3) Synthesis of graft copolymer: 7g N,N-diethylacrylamide, 5.5g nano-crosslinking agent, 2g butyl acrylate, 5g acryloyloxyethyl dimethyl benzyl ammonium chloride, 7g methacryloyloxyethyl trimethyl ammonium chloride, 1g emulsifier OP-10 and 1.5g potassium persulfate with a mass fraction of 5% were slowly added to the four-necked flask in (2) above. The stirring speed was set to 200r / min, nitrogen gas was purged for 20min, and the reaction was carried out at 55℃ for 4h. After the reaction was completed, the product was naturally cooled to room temperature. The product was precipitated with acetone, filtered and washed, and then dried at 80℃ to constant weight. It was then crushed and passed through a 100-mesh sieve to obtain a cationic graft copolymer flocculant for water-based waste drilling fluid.
[0053] Example 5
[0054] A method for preparing a cationic graft copolymer flocculant for water-based waste drilling fluid, the specific steps of which are as follows:
[0055] (1) Synthesis of nano-crosslinking agent: 10 mL of γ-methacryloxypropyltrimethoxysilane (KH570) was added to a three-necked flask containing 100 mL of a mixture of ethanol and water (ethanol to water volume ratio of 7:3). The mixture was stirred at room temperature for 3 h. Then, 12 g of nano-cellulose crystals were added to the three-necked flask, and the mixture was placed in a water bath at 40 °C and 100 r / min for 12 h. The resulting product was centrifuged, washed several times with anhydrous ethanol, and dried to constant weight to obtain the nano-crosslinking agent.
[0056] (2) Gelatinization of starch: Add 200 mL of deionized water and 12 g of corn starch to a four-necked flask equipped with a stirrer, condenser and thermometer. Raise the temperature to 80 °C and gelatinize for 30 min. After gelatinization, cool to 55 °C.
[0057] (3) Synthesis of graft copolymer: 7g N,N-diethylacrylamide, 5.5g nano-crosslinking agent, 2g butyl acrylate, 3g acryloyloxyethyl dimethyl benzyl ammonium chloride, 5g methacryloyloxyethyl trimethyl ammonium chloride, 1g emulsifier OP-10 and 1.5g potassium persulfate with a mass fraction of 5% were slowly added to the four-necked flask in (2) above. The stirring speed was set to 200r / min, nitrogen gas was purged for 20min, and the reaction was carried out at 55℃ for 4h. After the reaction was completed, the product was naturally cooled to room temperature. The product was precipitated with acetone, filtered and washed, and then dried at 80℃ to constant weight. It was then crushed and passed through a 100-mesh sieve to obtain a cationic graft copolymer flocculant for water-based waste drilling fluid.
[0058] Example 6
[0059] The technical solution adopted is:
[0060] As described in Example 1, except that the amount of emulsifier OP-10 added in step (3) is reduced to 0.5g.
[0061] Example 7
[0062] The technical solution adopted is:
[0063] As described in Example 1, except that in step (3), the amount of 5% potassium persulfate initiator added is reduced to 1.0g.
[0064] Comparative Example 1
[0065] The technical solution adopted is:
[0066] As described in Example 1, the difference is that corn starch is not added during the synthesis of the flocculant.
[0067] Comparative Example 2
[0068] The technical solution adopted is:
[0069] As described in Example 1, the difference is that no nano-crosslinking agent is added during the synthesis of the flocculant.
[0070] Comparative Example 3
[0071] The technical solution adopted is:
[0072] As described in Example 1, the difference is that no hydrophobic monomers are added during the synthesis of the flocculant.
[0073] Comparative Example 4
[0074] The technical solution adopted is:
[0075] As described in Example 1, the difference is that no cationic monomer is added during the synthesis of the flocculant.
[0076] The flocculants synthesized in Examples 1-7 and Comparative Examples 1-4 were evaluated as follows:
[0077] (1) CODcr content determination
[0078] 100g of waste oil drilling mud was weighed into a beaker at room temperature, and 0.2% of the flocculant samples from the examples and comparative examples were added. The mixture was stirred (200r / min) for 5 minutes and allowed to stand for 20 minutes. The CODcr content of the supernatant was determined by potassium dichromate reflux titration (GB T11914-89). The experimental results are shown in Table 1.
[0079] Table 1. Experimental results of CODcr content
[0080] category Increase / % Removal rate / % Example 1 0.2 90.9 Example 2 0.2 86.3 Example 3 0.2 85.5 Example 4 0.2 86.2 Example 5 0.2 84.4 Example 6 0.2 83.9 Example 7 0.2 83.2 Comparative Example 1 0.2 25.5 Comparative Example 2 0.2 24.5 Comparative Example 3 0.2 30.4 Comparative Example 4 0.2 21.2
[0081] As shown in Table 1, the CODcr removal rate of the samples with flocculants added to the waste drilling mud exceeded 85%, and the flocculation effect was significant. This was mainly due to the increased probability of contact and collision between the flocculant and the suspended matter in the drilling mud, which enhanced the adsorption and bridging effect and facilitated the formation, growth and sedimentation of flocs.
[0082] Compared to Example 1, Example 2, with its increased starch content, resulted in a larger molecular weight flocculant with poorer solubility in aqueous solution. In Comparative Example 1, without added starch, the CODcr removal rate was only 25.5%. The absence of corn starch reduced the flocculant's molecular weight, significantly weakening its adsorption and bridging effects, thus reducing its flocculation efficiency for suspended solids in the slurry. Compared to Example 1, Example 3, with its increased nano-crosslinking agent, resulted in a flocculant with poor water solubility and a CODcr removal rate of 85.5%. In Comparative Example 2, without the nano-crosslinking agent, the CODcr removal rate was only 24.5%. The polymerization of the flocculant prevented effective grafting of starch onto the polymer structure, similarly leading to a significant reduction in the flocculation efficiency for suspended solids in the slurry. Compared to Example 1, Example 4 and Comparative Example 3 reduced the amount of hydrophobic monomer, resulting in CODcr removal rates of 86.2% and 25.5%, respectively. The introduction of hydrophobic groups into the flocculant molecular chain causes aggregation due to hydrophobic interactions, leading to intramolecular and intermolecular associations within the macromolecular chains. This encapsulates some nanoparticle waste within the molecular chains, improving the flocculation effect. However, the amount of hydrophobic monomer should be kept moderate; excessive addition will reduce the flocculant's solubility in water. Since the organic particles in waste drilling fluid are typically negatively charged, cationic polymeric flocculants can neutralize their charge and act as adsorption bridges, causing the particles to lose stability, flocculate, and aid in sedimentation. Compared to Example 1, Example 5 and Comparative Example 4 reduced the amount of cationic monomer, resulting in a weakened flocculation effect of the flocculant on organic particles. Compared to Example 1, the CODcr removal rate in Example 6 was significantly reduced to 83.9% due to the reduced amount of emulsifier OP-10. This reduction is mainly because the decrease in emulsifier affects the stability of the emulsion, thereby weakening the flocculant performance. Similarly, in Example 7, the flocculant performance was weakened due to the reduced initiator amount, primarily because the lower initiator amount led to a decrease in polymerization efficiency.
[0083] (2) Turbidity test
[0084] 100g of waste oil drilling mud was weighed into a beaker at room temperature, and 0.2% of the flocculant samples from the examples and comparative examples was added. The mixture was stirred (200r / min) for 5 minutes, allowed to stand for 20 minutes, and the supernatant was taken and measured for residual turbidity using a turbidimeter. The experimental results are shown in Table 2.
[0085] Table 2. Results of Turbidity Test
[0086] category Increase / % Residual turbidity / NTU Example 1 0.2 15.3 Example 2 0.2 22.6 Example 3 0.2 23.8 Example 4 0.2 23.7 Example 5 0.2 24.6 Example 6 0.2 25.9 Example 7 0.2 25.2 Comparative Example 1 0.2 82.7 Comparative Example 2 0.2 84.8 Comparative Example 3 0.2 80.5 Comparative Example 4 0.2 92.4
[0087] As shown in Table 2, the residual turbidity of the samples with flocculants added to the waste drilling mud was less than 25 NTU, indicating a significant flocculation effect. This is mainly because the flocculant can interact with suspended solids and solid particles in the waste drilling mud. The particles aggregate through bridging and electrostatic attraction, causing them to grow larger and settle.
[0088] Compared to Example 1, Comparative Example 1, which did not add corn starch in its flocculant synthesis, had a residual turbidity as high as 82.7 NTU. This is because reducing the amount of corn starch significantly weakens the adsorption and bridging effect of the flocculant, resulting in ineffective settling of suspended matter in the drilling mud and an inability to effectively reduce residual turbidity. Compared to Example 1, Comparative Example 2, which did not add a nano-crosslinking agent, had a residual turbidity as high as 84.8 NTU. Reducing the amount of nano-crosslinking agent reduces the efficiency of corn starch grafting onto the polymer, weakening the flocculant's effect. Compared to Example 1, Comparative Example 3, which did not add a hydrophobic monomer, had a residual turbidity of 80.5 NTU. Reducing the amount of hydrophobic monomer also affects the flocculant's effect. Compared to Example 1, Examples 5 and 4 reduced the amount of cationic monomer, which weakens the interaction between the flocculant and negatively charged suspended matter in the waste drilling mud, reducing effective settling performance. Compared to Example 1, Examples 6 and 7 reduced the amounts of emulsifier and initiator, respectively, affecting the emulsion stability and polymerization rate during synthesis, resulting in a certain weakening of the flocculant's effect.
[0089] (3) Determination of suspended solids (SS content)
[0090] Take 100 mL of waste drilling fluid and add it to a stoppered graduated cylinder with a range of 100 mL. Add 0.2% of the flocculant samples from the examples and comparative examples. Shake the cylinder upside down 20 times and let it stand for 30 min. Then, measure the suspended solids (SS) content in the supernatant. The experimental results are shown in Table 3.
[0091] Table 3. Experimental results of suspended solids (SS content)
[0092] category Increase / % Suspended solids removal rate / % Example 1 0.2 94.3 Example 2 0.2 89.5 Example 3 0.2 88.5 Example 4 0.2 87.8 Example 5 0.2 86.4 Example 6 0.2 85.1 Example 7 0.2 84.5 Comparative Example 1 0.2 20.4 Comparative Example 2 0.2 21.8 Comparative Example 3 0.2 31.3 Comparative Example 4 0.2 19.6
[0093] As shown in Table 3, the removal rate of suspended solids in the waste drilling mud samples with the flocculant of the examples exceeded 85%, and the effective flocculation effect was significant. This is mainly because the flocculant can adsorb and bridge with the suspended solids in the waste drilling mud, causing the suspended solids particles to connect together, agglomerate and become larger, and then settle due to gravity.
[0094] Compared to Example 1, Comparative Example 1, which did not add corn starch, had a suspended solids removal rate of only 20.4%. This is because the absence of starch resulted in a lower molecular weight of the flocculant, significantly weakening its adsorption and bridging effect, leading to ineffective sedimentation of suspended solids in the drilling mud and affecting the flocculation effect. Compared to Example 1, Comparative Example 2, which did not add a nano-crosslinking agent, had a suspended solids removal rate of only 21.8%. The reduced amount of nano-crosslinking agent prevented starch from effectively grafting onto the polymer structure and weakened the crosslinking degree between the monomers, affecting the flocculant's effectiveness. Compared to Example 1, reducing the amount of hydrophobic monomers in Example 4 and Comparative Example 3 also affected the flocculant's efficiency in removing waste. Compared to Example 1, reducing the amount of cationic monomers in Example 5 and Comparative Example 4 resulted in suspended solids removal rates of 86.4% and 19.6%, respectively. The flocculant's effectiveness was significantly reduced because the lower cationic monomer content reduced the charge interaction between the flocculant and negatively charged substances in the waste drilling mud, hindering effective flocculation of the waste and reducing the suspended solids removal rate. Compared to Example 1, Example 6 reduced the amount of emulsifier, achieving a suspended solids removal rate of 85.1%, but the flocculant effect was significantly weakened. This is because reducing the amount of emulsifier affects the stability of the emulsion. Compared to Example 1, Example 7 reduced the amount of initiator, achieving a suspended solids removal rate of 84.5%, but the flocculant effect was significantly weakened. This is because reducing the amount of initiator affects the polymerization rate.
[0095] The above experimental results demonstrate that the water-based flocculant for waste drilling fluid of the present invention has the following advantages:
[0096] Advantage 1: The synthesis of nano-crosslinking agents can cause micro-crosslinking between flocculant monomers, generating a certain spatial network structure, thereby increasing the flocculation effect of flocculants on water-based drilling fluid waste.
[0097] Advantage 2: The developed flocculant for water-based waste drilling fluid contains positively charged active groups and polar groups, which can neutralize the charge and form hydrogen bonds with the waste particles in the drilling fluid, effectively flocculating the waste in the water-based drilling fluid.
[0098] Advantage 2: The developed water-based flocculant for waste drilling fluid achieved a CODcr removal rate of 90.9% after treatment of waste drilling mud at an addition of 0.2%, with residual turbidity of 15.3 NTU and suspended solids of 94.3%.
[0099] It should be noted that the corn starch in Example 1 can be replaced with either tapioca starch or potato starch.
[0100] In Example 1, the cationic monomer can be replaced with two of the following: acryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, ethyl methacrylate trimethyl ammonium chloride, and acryloyloxyethyl trimethyl ammonium chloride.
[0101] The hydrophobic monomer in Example 1 can be replaced with one of ethyl butyrate or ethyl acetate.
[0102] The emulsifier in Example 1 can be replaced with one of emulsifiers OP-4 and Tween 60.
[0103] The initiator in Example 1 can be replaced with one or two of potassium persulfate, sodium bisulfite, benzoyl peroxide, diisopropylbenzene peroxide, and dodecyl peroxide.
[0104] Specifically, in the preparation methods of Examples 1-7 of the present invention, the specific conditions of each step can be adjusted according to the actual situation, and the following conditions can be met after adjustment:
[0105] The specific process of step (1) is as follows:
[0106] Measure γ-methacryloxypropyltrimethoxysilane and add it to a three-necked flask containing a mixture of ethanol and water. Stir at room temperature for 2-4 hours. Then add nanocellulose crystals to the three-necked flask and place it in a water bath at 35-45℃ and 75-150r / min for 10-15 hours. Centrifuge the product, wash it several times with anhydrous ethanol, and dry it to constant weight to obtain the nano crosslinking agent. In step (1), the volume ratio of γ-methacryloxypropyltrimethoxysilane to the mixture containing ethanol and water is 1: (8-12), the volume ratio of water to ethanol is 1: (2-4), and the amount of nanocellulose crystals added to each 10mL of γ-methacryloxypropyltrimethoxysilane is 10-15g.
[0107] The specific process of step (2) is as follows:
[0108] Add deionized water and starch to a four-necked flask equipped with a stirrer, condenser and thermometer. Raise the temperature to 70-90℃ and gelatinize for 20-35 minutes. After gelatinization, cool to 50-60℃ and set aside. In step (2), the mass ratio of deionized water to starch is 20:(1-2).
[0109] The specific process of step (3) is as follows:
[0110] N,N-diethylacrylamide, nano-crosslinking agent, hydrophobic monomer, cationic polymerizing monomer, emulsifier, and 5% initiator were slowly added to the gelatinized starch. The stirring speed was set to 150-250 r / min, nitrogen gas was purged for 15-30 min, and the reaction was carried out at 50-60℃ for 3-5 h. After the reaction was completed, the product was naturally cooled to room temperature. The product was precipitated with acetone, filtered and washed, and then dried at 80℃ to constant weight. It was then crushed and sieved to obtain a cationic graft copolymer flocculant for water-based waste drilling fluid. In step (3), the mass ratio of starch, N,N-diethylacrylamide, nano-crosslinking agent, hydrophobic monomer, cationic polymerizing monomer, emulsifier, and 5% initiator was (10-20): (5-10): (4-7): (1-4): (8-16): (0.5-2): (1-3).
[0111] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing a cationic graft copolymer flocculant for water-based waste drilling fluid, characterized in that, The specific steps are as follows: (1) Synthesis of nano-crosslinking agent: γ-methacryloxypropyltrimethoxysilane was added to a mixture containing ethanol and water, followed by the addition of nanocellulose crystals. The mixture was placed in a water bath for reaction, and the resulting product was processed to obtain the nano-crosslinking agent. (2) Gelatinization of starch: After heating deionized water and starch to gelatinize, cool and set aside; (3) Synthesis of graft copolymer: N,N-diethylacrylamide, nano-crosslinking agent, hydrophobic monomer, cationic polymerizing monomer, emulsifier and initiator are slowly added to the gelatinized starch to carry out the reaction. The product obtained from the reaction is processed to obtain a cationic graft copolymer flocculant for water-based waste drilling fluid. In step (3), the cationic monomers are two of the following: acryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, ethyl methacrylate trimethyl ammonium chloride, and acryloyloxyethyl trimethyl ammonium chloride.
2. The preparation method of the cationic graft copolymer flocculant for water-based waste drilling fluid according to claim 1, characterized in that, The specific process of step (1) is as follows: γ-Methacryloxypropyltrimethoxysilane was measured and added to a three-necked flask containing a mixture of ethanol and water. The mixture was stirred at low speed at room temperature for 2-4 hours. Then, nanocellulose crystals were added to the three-necked flask and placed in a water bath at 35-45℃ and 75-150 r / min for 10-15 hours. The resulting product was centrifuged, washed several times with anhydrous ethanol, and dried to constant weight to obtain the nano-crosslinking agent.
3. The preparation method of the cationic graft copolymer flocculant for water-based waste drilling fluid according to claim 1, characterized in that, In step (1), the volume ratio of γ-methacryloxypropyltrimethoxysilane to the mixture containing ethanol and water is 1:(8-12), the volume ratio of water to ethanol is 1:(2-4), and the amount of nanocellulose crystals added per 10 mL of γ-methacryloxypropyltrimethoxysilane is 10-15 g.
4. The preparation method of the cationic graft copolymer flocculant for water-based waste drilling fluid according to claim 1, characterized in that, The specific process of step (2) is as follows: Add deionized water and starch to a four-necked flask equipped with a stirrer, condenser and thermometer. Raise the temperature to 70-90℃ and gelatinize for 20-35 minutes. After gelatinization, cool to 50-60℃ and set aside.
5. The preparation method of the cationic graft copolymer flocculant for water-based waste drilling fluid according to claim 4, characterized in that, In step (2), the mass ratio of deionized water to starch is 20:(1-2).
6. The preparation method of the cationic graft copolymer flocculant for water-based waste drilling fluid according to claim 1, characterized in that, The specific process of step (3) is as follows: N,N-diethylacrylamide, nano-crosslinking agent, hydrophobic monomer, cationic polymerizing monomer, emulsifier, and 5% (w / w) initiator were slowly added to the gelatinized starch. The stirring speed was set to 150-250 r / min, nitrogen gas was purged for 15-30 min, and the reaction was carried out at 50-60℃ for 3-5 h. After the reaction was completed, the mixture was naturally cooled to room temperature. The product was precipitated with acetone, filtered, and washed. Then it was dried at 80℃ to constant weight, pulverized, and sieved to obtain a cationic graft copolymer flocculant for water-based waste drilling fluid.
7. The preparation method of the cationic graft copolymer flocculant for water-based waste drilling fluid according to claim 6, characterized in that, In step (3), the mass ratio of starch, N,N-diethylacrylamide, nano-crosslinking agent, hydrophobic monomer, cationic polymerizing monomer, emulsifier and initiator with a mass fraction of 5% is (10-20): (5-10): (4-7): (1-4): (8-16): (0.5-2): (1-3).
8. The preparation method of a cationic graft copolymer flocculant for water-based waste drilling fluid according to claim 1, characterized in that, In step (2), the starch is one of corn starch, tapioca starch, or potato starch, and the average molecular weight of the starch is 50,000-80,000.
9. The preparation method of the cationic graft copolymer flocculant for water-based waste drilling fluid according to claim 1, characterized in that, In step (3), the hydrophobic monomer is butyl acrylate.
10. The preparation method of the cationic graft copolymer flocculant for water-based waste drilling fluid according to claim 1, characterized in that, In step (3), the emulsifier is one of emulsifier OP-4, emulsifier OP-10, or Tween 60.
11. The preparation method of the cationic graft copolymer flocculant for water-based waste drilling fluid according to claim 1, characterized in that, In step (3), the initiator is one or two of potassium persulfate, sodium bisulfite, benzoyl peroxide, diisopropylbenzene peroxide, and dodecyl peroxide.
12. A cationic graft copolymer flocculant for water-based waste drilling fluid prepared by the preparation method according to any one of claims 1-11.