An environmentally-friendly drilling fluid filtrate reducer based on mangosteen shell modification and a preparation method thereof

Abstract

The application discloses an environment-friendly drilling fluid filtrate reducer based on mangosteen shell modification and a preparation method thereof. The environment-friendly drilling fluid filtrate reducer is obtained by grafting copolymerization of activated mangosteen shells obtained by oxidation and carboxymethylation modification of mangosteen shell powder, and functional monomers and crosslinking agents. The application uses waste mangosteen shells as raw materials, and prepares a green drilling filtrate reducer with efficient filtrate reduction performance and excellent environmental protection through three-step reactions of 'oxidation-carboxymethylation-polymerization'. The green drilling filtrate reducer has excellent filtrate reduction capacity and good rheological regulation in a wide temperature range (normal temperature to 200 DEG C), and has the characteristics of low toxicity and easy biodegradation, thereby filling the technical blank of bio-based filtrate reducers in the field.

Description

Technical Field

[0001] This invention belongs to the field of organic additives used in drilling compositions, specifically relating to an environmentally friendly drilling fluid filtration reducer based on mangosteen shell modification and its preparation method. Background Technology

[0002] In green drilling operations, drilling fluid (flushing fluid) plays a crucial role in carrying cuttings, stabilizing the wellbore, cooling and lubricating the drill bit, and balancing formation pressure. Filtration reducers, as one of the core treatment agents in drilling fluid, primarily reduce the amount of free water lost from the drilling fluid to the formation, helping to form a thin and dense mud cake. This effectively prevents wellbore instability, stuck pipe, and other accidents, ensuring safe and efficient drilling operations.

[0003] With increasingly stringent global environmental regulations and a growing emphasis on sustainable development, synthetic polymer-based fluid loss reducers (such as polyacrylamide and its derivatives) used in traditional drilling fluid systems have revealed problems such as poor biodegradability and high potential ecotoxicity risks, particularly limiting their application in environmentally sensitive areas (such as water sources and ecological protection zones). Therefore, research and development has shifted towards widely available and renewable natural bio-based materials, such as starch and cellulose derivatives. However, these natural polymers generally suffer from insufficient temperature and salt resistance, and are prone to biodegradation or performance failure in high-temperature and high-salt formations, limiting their application under complex drilling conditions.

[0004] Based on this, the present invention uses waste mangosteen shells as raw materials, makes full use of their special structure, increases their active sites through modification, and copolymerizes them with an appropriate amount of functional monomers to prepare a green drilling filtration reducer that has both high efficiency in reducing filtration loss and excellent environmental protection. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing an environmentally friendly drilling fluid filtration reducer based on mangosteen shell modification and its preparation method. This environmentally friendly drilling fluid filtration reducer has excellent filtration reduction performance and is suitable for high-temperature and high-salt drilling conditions.

[0006] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0007] The first aspect of this invention provides an environmentally friendly drilling fluid filtration reducer based on modified mangosteen shell, which is obtained by graft copolymerization of activated mangosteen shell obtained by oxidation and carboxymethylation of mangosteen shell powder with functional monomers and crosslinking agents.

[0008] According to the above scheme, the functional monomers are acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), itaconic acid (IA), and dimethylaminoethyl methacrylate (DMAEMA), and the crosslinking agent is N,N-methylenebisacrylamide (MBA).

[0009] According to the above scheme, the mass ratio of activated mangosteen shell to acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, itaconic acid, and dimethylaminoethyl methacrylate is 10-12:5-8:2-3:1:1-2, and the amount of N,N-methylenebisacrylamide is 1.5-3% of the total mass of the functional monomers.

[0010] The second aspect of this invention provides a method for preparing the above-mentioned environmentally friendly drilling fluid filtration reducer based on mangosteen shell modification, the specific steps of which are as follows:

[0011] 1) Preparation of activated mangosteen shell: Mangosteen shell powder was mixed with KMnO4 solution for oxidation reaction, followed by solid-liquid separation. The obtained solid was washed and dried to obtain oxidized mangosteen shell. The obtained oxidized mangosteen shell was then modified by carboxymethylation to obtain activated mangosteen shell.

[0012] 2) Preparation of environmentally friendly drilling fluid filtration reducer: The activated mangosteen shell obtained in step 1) is subjected to graft copolymerization reaction with functional monomers and crosslinking agents, and then post-processed to obtain an environmentally friendly drilling fluid filtration reducer based on mangosteen shell modification.

[0013] According to the above scheme, the mangosteen shell powder in step 1) has a mesh size of 100-300 mesh.

[0014] According to the above scheme, the concentration of the KMnO4 solution in step 1) is 1-2wt%, and the mass-to-volume ratio of the mangosteen shell powder to the KMnO4 solution is 0.1-0.2g / mL.

[0015] According to the above scheme, the oxidation reaction conditions for step 1) are: stir the reaction at room temperature (20-35℃) for 8-10 hours, and then let it stand for 10-12 hours.

[0016] According to the above scheme, step 1) of modifying oxidized mangosteen shells by carboxymethylation is as follows: disperse oxidized mangosteen shells in ethanol at 40-45℃, add NaOH, react for 30-40 minutes, then add chloroacetic acid ethanol solution, adjust the pH of the system to 7-8, react at 40-45℃ for 3-4 hours, separate the solid and liquid of the reaction solution, and finally wash and dry the obtained solid product.

[0017] According to the above scheme, the mass-to-volume ratio of oxidized mangosteen shell to ethanol is 0.1-0.25 g / mL, the mass ratio of NaOH to oxidized mangosteen shell is 0.6-1.5:1, and the concentration of the chloroacetic acid ethanol solution is 0.4-0.6 g / mL, wherein the mass ratio of chloroacetic acid to oxidized mangosteen shell is 0.6-1.5:1.

[0018] According to the above scheme, step 2) involves grafting and copolymerizing the activated mangosteen shell with functional monomers and crosslinking agents. The specific method is as follows: the activated mangosteen shell is uniformly dispersed in deionized water, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and itaconic acid are added, and the mixture is stirred evenly at 55-65℃. The temperature is then raised to 70-80℃, and dimethylaminoethyl methacrylate and N,N-methylenebisacrylamide are added. The mixture is stirred evenly, the pH of the system is adjusted to 8-9, an initiator is added, and the reaction is carried out at 70-80℃ for 5-7 hours.

[0019] According to the above scheme, the mass-to-volume ratio of the activated mangosteen shell to deionized water is 0.06-0.2 g / mL.

[0020] According to the above scheme, the initiator is ammonium persulfate (APS), and the amount of initiator used is 0.5-1.5% of the total mass of the functional monomers.

[0021] According to the above scheme, the post-processing method in step 2) is as follows: filter the reaction solution, wash the obtained filter residue with ethanol and dry it at 55-65℃ to constant weight.

[0022] The third aspect of this invention provides the application of the above-mentioned environmentally friendly drilling fluid filtration reducer based on mangosteen shell modification as a drilling additive.

[0023] Mangosteen shell is a major agricultural waste in tropical regions, with a huge annual output. It has a high lignin content and can maintain its structural integrity under high temperature and pressure, with a temperature resistance up to 150℃. Its phenolic hydroxyl density is 3-5 times that of ordinary plant fibers. Furthermore, it possesses a unique structure: the cell walls of mangosteen shells consist of a dense composite network of cellulose microfibrils (crystalline regions) and an amorphous matrix (hemicellulose, lignin, pectin). The microfibrils are arranged in a spiral pattern, giving the material excellent mechanical strength and deformation recovery ability. It also has micron-nano multi-level pores, including cell cavities (approximately 10-50 μm in diameter), cell wall micropores (20-500 nm), and intermolecular gaps (<10 nm). The outer layer of the mangosteen shell is a keratinized epidermis approximately 100-200 μm thick, while the inner layer is a loose sponge tissue, combining barrier function with a high specific surface area. Its surface has a rough, grooved structure with a specific surface area of ​​120-180 m². 2 / g, significantly higher than ordinary plant fiber, with fiber diameter of 5-20μm, length of 100-500μm, and moderate aspect ratio (20-50). This invention utilizes a two-stage modification process of "oxidation-carboxymethylation," combined with the high phenolic hydroxyl density on the surface of mangosteen shell fibers, to introduce a large number of active sites into the mangosteen shell skeleton structure, making it easy to disperse uniformly in water. Based on this, a multi-component copolymer is grafted, integrating various functional groups such as sulfonic acid groups, carboxyl groups, amide groups, and quaternary ammonium groups. Furthermore, it moderately crosslinks to construct a three-dimensional network structure, exhibiting excellent filtration loss reduction performance. The micron-sized pores within the mangosteen shell are used for rapid hydration, while the nano-sized pores are used for precise sealing, achieving a "dual sealing" effect. The moderate fiber length avoids the rheological property deterioration caused by long fibers and overcomes the defects of loose filter cakes formed by short fibers. The fibers intertwine to form a continuous network, and the numerous active sites on the fiber surface ensure that the fibers retain bridging ability between fragments even after crushing, which is beneficial for constructing a dense filter cake and provides stronger interfacial adsorption capacity. It can effectively seal micro-cracks (width <10μm) in reservoir rocks, forming a thin and dense filter cake.

[0024] The beneficial effects of this invention are as follows: 1. This invention uses waste mangosteen shells as raw materials and prepares a green drilling filtration reducer with both high efficiency in reducing filtration loss and excellent environmental friendliness through a three-step reaction of "oxidation-carboxymethylation-multi-component copolymerization". It exhibits excellent filtration loss reduction capacity and good rheological regulation over a wide temperature range (room temperature to 200℃), and possesses low toxicity and easy biodegradability, filling the technological gap in bio-based filtration reducers in this field. 2. The preparation method of this invention is mild, the raw materials used are common and readily available, and the production process is easy to control, realizing high-value-added resource utilization of agricultural waste, meeting the environmental protection requirements of green drilling, and possessing the potential for large-scale industrial production. Attached Figure Description

[0025] Figure 1 SEM image and elemental composition comparison diagram of the mangosteen shell powder (MS) used in the embodiments of the present invention;

[0026] Figure 2 The infrared spectra of the raw material MS used in Example 1 and the KMS, CM-KMS and MSIAA obtained in each step are compared.

[0027] Figure 3 XPS plot of MSIAA prepared in Example 1;

[0028] Figure 4 The images show the simultaneous thermal analysis (TG-DSC) test results of the raw materials used in Example 1, as well as the CM-KMS and MSIAA obtained in each step.

[0029] Figure 5A comparison chart of filtration loss at different temperatures for freshwater-based slurry, the filtration loss reducers prepared in Examples 1-4, and the filtration loss reducers in Comparative Examples 1-3. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0031] The SEM image of the mangosteen shell powder (MS) used in the embodiments of the present invention is shown below. Figure 1 As shown on the left, its surface exhibits a wrinkled appearance, mainly composed of flocculent and needle-like structures. The proportions of each element in the MS spectrum, obtained from its energy dispersive spectroscopy (EDS) results, are as follows: Figure 1 As shown on the right, the components are presumed to be fiber, alcohol, or phenolic substances.

[0032] Example 1

[0033] An environmentally friendly drilling fluid filtration reducer based on modified mangosteen shell is prepared as follows:

[0034] 1) Oxidative modification: Accurately weigh 10g of mangosteen shell powder that has passed through a 100-mesh sieve, mix it with 100mL of 1wt% KMnO4 solution, stir magnetically at room temperature for 9 hours, stop stirring and let stand for 12 hours, centrifuge to remove the liquid, and wash the solid repeatedly with deionized water until the washing liquid is colorless and neutral. Place the obtained solid product in a 60℃ oven and dry it to constant weight to obtain oxidized mangosteen shell (KMS). Repeat this step to obtain more than 10g of KMS for later use.

[0035] 2) Carboxymethylation modification: Weigh 10g of the above KMS and disperse it in 80mL of anhydrous ethanol. Stir it evenly in a 40℃ water bath. Then add 10g of NaOH and continue stirring for 30 minutes. Then slowly add chloroacetic acid ethanol solution (obtained by dissolving 10g of chloroacetic acid in 20mL of ethanol). Adjust the pH of the reaction solution to about 7.5 with dilute hydrochloric acid (0.1mol / L). Stir the reaction at 40℃ for 3 hours. After the reaction is completed, centrifuge to remove the liquid. Wash the remaining solid with deionized water until neutral. Dry it thoroughly at 60℃ to obtain activated mangosteen shell (CM-KMS). Repeat this step to obtain more than 10g of CM-KMS for later use.

[0036] 3) Graft copolymerization: In a 500mL beaker, add 100mL of deionized water and 10g of the above CM-KMS, stir to disperse evenly, then add 6g AM, 2g AMPS, and 1g IA in sequence, stir at 60℃ for 2 hours, then raise the system temperature to 75℃, add 1g DMAEMA and 0.3g MBA, stir for 10 minutes, adjust the pH of the system to 8.5 with 10wt% NaOH solution, then dissolve 0.15g APS in 5mL of deionized water and slowly add it dropwise to the reaction system, keep the reaction at 75℃ for 6 hours. After the reaction is complete, filter the reaction solution, soak and wash the obtained filter residue with anhydrous ethanol 3 times, centrifuge to remove the liquid, dry in a 60℃ oven, grind and pass through a 200-mesh sieve to obtain a brown powder product, which is designated as the environmentally friendly drilling fluid filtration reducer (MSIAA) based on mangosteen shell modification.

[0037] The infrared spectra comparison diagrams of the raw material MS used in this embodiment and the KMS, CM-KMS and MSIAA obtained in each step are shown below. Figure 2 As shown, MS mainly displays typical peaks of biomass, confirming the presence of cellulose, hemicellulose, and lignin. The characteristic peaks of KMS obtained after KMnO4 oxidation indicate successful oxidation, introducing oxygen-containing functional groups (such as more C=O / COOH) onto the molecular chain. The characteristic peaks of CM-KMS obtained after carboxymethylation show carboxymethyl characteristic peaks, confirming successful grafting of carboxymethyl groups onto the backbone. The characteristic peaks of the final copolymer MSIAA prove the successful copolymerization of anionic (-COO) groups. - -SO3 - It is an amphoteric polymer of amines and cationic (tertiary amines) and possesses the key functional group structure for use as a highly efficient filtration loss reducer.

[0038] Figure 3 The XPS spectrum of the MSIAA prepared in this embodiment clearly shows that the sample surface is mainly composed of five elements: C, O, N, S, and Na. Their positions correspond to the expected electron binding energies of the functional groups (polymer carbon chains, amide groups, carboxyl / carboxymethyl groups, sulfonic acid groups, and sodium ions possibly existing in salt form). This confirms the successful synthesis of the complex polymer MSIAA containing multiple functional groups (particularly confirming the S-containing sulfonic acid group and the N-containing amide / amine group).

[0039] Figure 4The images show the simultaneous thermal analysis (TG-DSC) results of the raw materials MS used in this embodiment and the CM-KMS and MSIAA obtained in each step. MS degradation mainly consists of two stages: the initial stage (~68.87℃) involves the loss of adsorbed water (7.11% weight loss), and the main decomposition stage, which shows a sharp DTG peak at 330.76℃, corresponding to the pyrolysis of components such as cellulose (61.63% weight loss). The final char residue is 38.37%, demonstrating the high thermal stability of biomass itself. The CM-KMS main decomposition temperature is significantly advanced to 267.08℃ (32.78% weight loss), indicating that the introduced carboxymethyl groups have poor thermal stability. The initial water loss is increased (13.97%), and the final char residue decreases to 32.35%, indicating that the modification weakens the high-temperature stability of the material. The dehydration stage of MSIAA was more pronounced (total weight loss ~17.05%), with the main decomposition peak at 304.1℃ (weight loss 39.95%). Its decomposition temperature was higher than CM-KMS but lower than MS, and the char residue further decreased to 21.57%, reflecting the thermal behavior characteristics of the organic polymer network. The comparison shows that the thermal stability of the products at each stage exhibits a regular change with the modification process:

[0040] Main decomposition temperatures: MS (330.76℃) > MSIAA (304.1℃) > CM-KMS (267.08℃). Polymerization and crosslinking improve the thermal stability of MSIAA compared to CM-KMS.

[0041] Residual carbon content: MS (38.37%) > CM-KMS (32.35%) > MSIAA (21.57%), indicating that the conversion from natural biomass to organic polymers reduced the high-temperature carbonization capacity.

[0042] Water loss behavior: Due to its rich content of hydrophilic functional groups, MSIAA has a significantly higher water absorption and loss rate than the former two.

[0043] While chemical modification imparts target functional groups to materials, it reduces their overall thermal stability and char content. However, MSIAA, by constructing a polymer network based on CM-KMS, raised the main decomposition temperature to approximately 300°C, achieving relatively mild thermal decomposition behavior within the critical temperature range of 200-350°C. This provides a thermal performance basis for its application in downhole intermediate-temperature environments.

[0044] Example 2

[0045] An environmentally friendly drilling fluid filtration reducer with high sulfonic acid monomer content is prepared using the same method as in Example 1, except that the monomer feeding ratio is changed to: AM 5.0g, AMPS 3.0g, IA 1.0g, and DMAEMA 1.0g. The resulting product is designated as MSIAA-1.

[0046] Example 3

[0047] An environmentally friendly drilling fluid filtration reducer with high cationic monomer content is prepared using the same method as in Example 1, except that the monomer feeding ratio is changed to: AM 5.0g, AMPS 2.0g, IA 1.0g, and DMAEMA 2.0g. The resulting product is designated as MSIAA-2.

[0048] Example 4

[0049] An environmentally friendly drilling fluid filtration reducer with low crosslinking degree is prepared using the same method as in Example 1, except that the amount of crosslinking agent MBA is adjusted from 0.3g to 0.15g. The resulting product is designated as MSIAA-3.

[0050] Comparative Example 1

[0051] An environmentally friendly drilling fluid filtration reducer is prepared by omitting the carboxymethylation step compared to Example 1, and directly replacing CM-KMS with an equal amount of KMS in copolymerization to obtain control sample C-1.

[0052] Comparative Example 2

[0053] An environmentally friendly drilling fluid filtration reducer was prepared by omitting the sulfonic acid monomer (i.e., not adding AMPS) and adjusting the amount of AM from 6.0g to 8.0g for copolymerization, resulting in control sample C-2.

[0054] Comparative Example 3

[0055] Commercially available starch-based filtration reducer hydroxyethyl starch (purchased from Maclean's) was used as control sample C-3.

[0056] Test case

[0057] According to the standards of the oil and gas industry, take 350 mL of distilled water, add 14.0 g of sodium bentonite and 0.28 g of anhydrous sodium carbonate, stir at high speed for 20 min, and cure in a sealed container at 25±1℃ for 24 h to obtain a fresh water-based slurry.

[0058] Filtration loss reducer performance test at room temperature: 1.0% (w / v, 1g filtration loss reducer per 100ml of freshwater-based slurry) of the filtration loss reducer to be tested was added to the freshwater-based slurry. After stirring at 800rpm for 20min, the slurry to be tested was obtained. The apparent viscosity (AV) and dynamic shear force (YP) were measured using a six-speed rotational viscometer, and the API filtrate loss (FL) was measured using a medium-pressure filtrate loss meter. The test results are shown in Table 1 below.

[0059] Table 1

[0060]

[0061] As shown in Table 1, adding 1.0% MSIAA to the freshwater-based slurry significantly reduced the API filtration loss (FL) from 30 mL to 9.2 mL, achieving a filtration loss reduction rate of 69.3%. This effect is superior to commercially available starch-based product C-3 (FL: 10.4 mL) and comparative examples lacking key steps or monomers (C-1, C-2), indicating that it can rapidly form a dense filter cake at room temperature, effectively controlling water loss. Simultaneously, MSIAA exhibits excellent rheological regulation capabilities, maintaining an apparent viscosity (AV) of 5 mPa·s and increasing the dynamic shear force (YP) to 2 Pa, which is beneficial for drilling fluid to carry cuttings.

[0062] Temperature resistance test of filtration loss reducer: The test slurry with the filtration loss reducer added was put into a high-temperature aging tank and subjected to rolling heat aging in a roller heating furnace at 100℃, 150℃ and 200℃ for 16 hours respectively. After being taken out and cooled to room temperature, it was stirred at 800 rpm for 5 minutes at 25±2℃. The rheological parameters and API filtration loss were measured after heat aging at different temperatures.

[0063] The performance test results of the filtration loss reducer after 100℃ heat aging are shown in Table 2 below.

[0064] Table 2

[0065]

[0066] The performance test results of the filtration loss reducer after heat aging at 150℃ are shown in Table 3 below.

[0067] Table 3

[0068]

[0069] The performance test results of the filtration loss reducer after heat aging at 200℃ are shown in Table 4 below.

[0070] Table 4

[0071]

[0072] As shown in Table 2-4, after 16 hours of rolling heat aging at 100℃, 150℃, and 200℃, MSIAA exhibited excellent high-temperature stability. Regarding filtration loss reduction, after extreme aging at 200℃, the filtration loss of MSIAA was only 18.6 mL, a controllable increase compared to its performance at room temperature (an increase of 11.6 mL), and significantly lower than that of the freshwater-based slurry (86.2 mL) and the commercially available comparative sample C-3 (82 mL). This demonstrates that its three-dimensional network structure can be effectively maintained at high temperatures, exhibiting significant resistance to high-temperature decomposition. In terms of rheological properties, although the AV and YP values ​​of MSIAA increased to some extent after high-temperature aging, they remained within an excellent controllable range (AV: 34 mPa·s, YP: 9.5 Pa at 200℃), without excessive thickening or flocculation, indicating that the product possesses good high-temperature rheological stability.

[0073] like Figure 5 The figure shows a comparison of the filtration loss of freshwater-based slurry, the filtration loss reducers prepared in Examples 1-4, and the filtration loss reducers in Comparative Examples 1-3 at different temperatures. It can be seen that the filtration loss of MSIAA is lower than that of other filtration loss reducer samples at all test temperatures, especially at the extreme high temperature of 200℃, where its filtration loss remains at a low level.

[0074] The control sample C-1, prepared directly from oxidized mangosteen shells using KMS, showed higher filtration loss than MSIAA at all temperature ranges, especially at 200℃. This indicates that carboxymethylation successfully introduced a large number of carboxylic acid groups into the mangosteen skeleton, which not only enhanced the hydrophilicity and reactivity of the raw material but also provided more sites for subsequent graft copolymerization, thus forming the basis for constructing stable and high-performance polymers.

[0075] Compared with sample C-2 (without AMPS), after aging at 150℃ and 200℃, although the filtration loss was acceptable, its high-temperature rheological stability was poor (AV and YP fluctuated more). In contrast, MSIAA with AMPS introduced had lower filtration loss and was more stable at high temperatures, proving that sulfonic acid groups can effectively enhance the rigidity of polymer chains and electrolyte resistance, and are the key components for maintaining high-temperature performance.

[0076] Both MSIAA-1 (high sulfonic acid content) and MSIAA-2 (high cationic content) showed a decrease in filtration performance at high temperatures. In comparison, MSIAA exhibited good overall performance and was the preferred formulation. MSIAA-3 (low crosslinking degree) showed an increase in filtration loss at high temperatures, confirming that an appropriate crosslinking density is indispensable for maintaining the integrity of the three-dimensional network at high temperatures.

[0077] To assess the environmental friendliness of the product, the biotoxicity and biodegradability of the MSIAA prepared in Example 1 were tested.

[0078] Preparation of MSIAA filtration loss reducer dispersion: Weigh 2.00 g (accurate to 0.01 g) of the MSIAA sample prepared in Example 1, add 80-85 mL of deionized water, and stir and disperse at 25±2℃ and 500-800 r / min for 30-40 minutes until a uniform dispersion is obtained. Transfer the entire dispersion to a 100 mL volumetric flask, make up to volume, and shake well to obtain the MSIAA filtration loss reducer dispersion.

[0079] Using BOD5 / COD Cr The ratio method was used to test the biodegradability of the MSIAA filtration loss reducing agent dispersion; the luminescent bacteria method was used to test the biotoxicity (EC50) of the MSIAA filtration loss reducing agent dispersion. 50 ), to assess its environmental performance. The EC of MSIAA was measured. 50 The value is 3.86 × 10 4 mg / L, BOD5 is 7.87×10 3 COD Cr 1.51×10 4 BOD5 / COD Cr It is 52.2%. According to the People's Republic of China Petroleum and Natural Gas Industry Standard "SY / T 6787-2010 Technical Requirements for Environmental Protection of Water-Soluble Oilfield Chemicals", EC 50 Greater than 2×10 4 mg / L is non-toxic, BOD5 / COD Cr A ratio greater than 5% indicates easy degradation. Therefore, the MSIAA filtration loss reducer prepared in this invention has significant environmental advantages of low toxicity and easy biodegradability, fully meeting the stringent requirements of green drilling technology for the environmental compatibility of treatment agents.

[0080] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. An environmentally friendly drilling fluid filtration reducer based on modified mangosteen shell, characterized in that, It is obtained by graft copolymerization of activated mangosteen shells (obtained by oxidation and carboxymethylation modification of mangosteen shell powder) with functional monomers and crosslinking agents. The functional monomers are acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, itaconic acid, and dimethylaminoethyl methacrylate. The mass ratio of the activated mangosteen shell to acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, itaconic acid, and dimethylaminoethyl methacrylate is 10-12:5-8:2-3:1:1-2. The crosslinking agent is N,N-methylenebisacrylamide, and the amount of N,N-methylenebisacrylamide used is 1.5-3% of the total mass of the functional monomers.

2. A method for preparing an environmentally friendly drilling fluid filtration reducer based on mangosteen shell modification as described in claim 1, characterized in that, The specific steps are as follows: 1) Preparation of activated mangosteen shell: Mangosteen shell powder was mixed with KMnO4 solution for oxidation reaction, followed by solid-liquid separation. The obtained solid was washed and dried to obtain oxidized mangosteen shell. The obtained oxidized mangosteen shell was then modified by carboxymethylation to obtain activated mangosteen shell. 2) Preparation of environmentally friendly drilling fluid filtration reducer: The activated mangosteen shell obtained in step 1) is subjected to graft copolymerization reaction with functional monomers and crosslinking agents, and then post-processed to obtain an environmentally friendly drilling fluid filtration reducer based on mangosteen shell modification.

3. The preparation method of the environmentally friendly drilling fluid filtration reducer based on mangosteen shell modification according to claim 2, characterized in that, Step 1) The mangosteen shell powder has a mesh size of 100-300 mesh; Step 1) The KMnO4 solution has a concentration of 1-2wt%, and the mass-to-volume ratio of the mangosteen shell powder to the KMnO4 solution is 0.1-0.2g / mL; Step 1) The oxidation reaction conditions are: stirring at room temperature for 8-10 hours, and then standing for 10-12 hours.

4. The preparation method of the environmentally friendly drilling fluid filtration reducer based on mangosteen shell modification according to claim 2, characterized in that, Step 1) The method for carboxymethylation modification of oxidized mangosteen shell is as follows: Disperse oxidized mangosteen shell in ethanol at 40-45℃, add NaOH, react for 30-40 minutes, then add ethanol solution of chloroacetic acid, adjust the pH of the system to 7-8, react at 40-45℃ for 3-4 hours, separate the solid and liquid of the reaction solution, and finally wash and dry the obtained solid product.

5. The preparation method of the environmentally friendly drilling fluid filtration reducer based on mangosteen shell modification according to claim 4, characterized in that, The mass-to-volume ratio of oxidized mangosteen shell to ethanol is 0.1-0.25 g / mL, the mass ratio of NaOH to oxidized mangosteen shell is 0.6-1.5:1, and the concentration of the chloroacetic acid ethanol solution is 0.4-0.6 g / mL, wherein the mass ratio of chloroacetic acid to oxidized mangosteen shell is 0.6-1.5:

1.

6. The preparation method of the environmentally friendly drilling fluid filtration reducer based on mangosteen shell modification according to claim 2, characterized in that, Step 2) The activated mangosteen shell is grafted copolymerized with functional monomers and crosslinking agents. The specific method is as follows: the activated mangosteen shell is uniformly dispersed in deionized water, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and itaconic acid are added, and the mixture is stirred evenly at 55-65℃. Then the temperature is raised to 70-80℃, and dimethylaminoethyl methacrylate and N,N-methylenebisacrylamide are added. The mixture is stirred evenly, the pH value of the system is adjusted to 8-9, the initiator is added, and the reaction is carried out at 70-80℃ for 5-7 hours.

7. The preparation method of the environmentally friendly drilling fluid filtration reducer based on mangosteen shell modification according to claim 6, characterized in that, The initiator is ammonium persulfate, and the amount of initiator used is 0.5-1.5% of the total mass of the functional monomers.

8. The application of the environmentally friendly drilling fluid filtration reducer based on mangosteen shell modification as a drilling additive according to claim 1.

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