A modified bentonite slurry, its preparation method and application

Abstract

This invention discloses a modified bentonite drilling mud, its preparation method, and its application, belonging to the technical field of drilling mud and geotechnical engineering materials. The modified bentonite drilling mud disclosed in this invention, by mass parts, comprises: 100 parts sodium-based bentonite, 0.5 parts anhydrous sodium carbonate, 1-5 parts gum arabic, 0.1-2 parts xanthan gum, and 1000 parts water. The modified bentonite drilling mud disclosed in this invention solves the technical problem that existing drilling muds are unable to simultaneously meet engineering performance requirements, be environmentally friendly, and possess good salt resistance.

Description

Technical Field

[0001] This invention belongs to the technical field of drilling mud and geotechnical engineering materials, specifically relating to a modified bentonite mud, its preparation method, and its application. Background Technology

[0002] Bentonite drilling mud, with its superior colloidal wall-protecting ability, efficient cuttings suspension and carrying characteristics, and excellent lubrication and drag-reduction properties, occupies a core position in various underground engineering fields such as shield tunneling, oil and gas field drilling and development, and pile foundation construction, becoming a key engineering material for ensuring construction safety and improving operational efficiency. In traditional bentonite drilling mud systems, sodium carboxymethyl cellulose (CMC) is the most widely used viscosity-enhancing and filtration-reducing agent. It significantly increases the viscosity of the mud through the adsorption and entanglement of molecular chains, while effectively reducing mud filtration loss through the molecular film formation effect, playing an irreplaceable role in maintaining borehole wall stability and preventing borehole collapse and mud leakage. However, during the industrial production of CMC, incomplete raw material refining and chemical reactions inevitably generate a large amount of industrial salt byproducts. These byproducts not only increase the ionic strength of the mud system and affect colloidal stability, but also increase the difficulty of desalination during waste mud treatment. More importantly, the ether bonds and carbon-carbon skeleton contained in the CMC molecular structure are difficult to be degraded by microorganisms in the natural environment, and long-term accumulation will cause soil compaction and eutrophication of water bodies. In addition, industrial-grade CMC production raw materials often contain C r3+ Pb 2+ Heavy metal impurities, such as ions, gradually seep into the soil and groundwater during the use and disposal of mud, causing persistent pollution, disrupting the ecological balance, threatening the survival of plants and animals and human health, and posing a huge challenge to the harmless treatment of waste mud, increasing the environmental protection cost of engineering projects, which is contrary to the current development concept of green engineering construction.

[0003] To address environmental challenges, researchers have experimented with various natural plant gums, such as guar gum, xanthan gum, and flaxseed gum. However, these single plant gums all have drawbacks: guar gum has good thickening effects but poor filtration loss reduction capabilities; xanthan gum has good filtration loss reduction properties but moderate thickening efficiency; and flaxseed gum has insufficient filtration loss reduction capabilities. Currently, no natural plant gum can simultaneously meet the stringent requirements of engineering for both mud viscosity and API filtration loss, and therefore cannot effectively replace CMC. Although some existing patents, such as Chinese patent application CN111621271A, disclose a salt-responsive smart polymer saturated brine drilling fluid and its preparation method, the technical solutions employed attempt to improve performance through composite components or cross-linking technology, but generally fail to overcome the bottlenecks of poor salt resistance and easily damaged viscosity of natural plant gums in high-salt formations.

[0004] Gum arabic is a natural, biodegradable polysaccharide hydrophilic colloid with abundant sources and low cost. While existing technologies mention its application in drilling fluids, these studies primarily utilize coarsely processed gum blocks and fail to address its weak salt resistance in high-salt formations. Traditional bentonite drilling muds often employ carboxymethyl cellulose (CMC) as an additive to improve performance; however, CMC suffers from poor environmental compatibility and limited biodegradability. Therefore, developing a natural drilling mud additive that simultaneously meets engineering performance requirements, is environmentally friendly, and possesses good salt resistance has become a pressing technical challenge in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a modified bentonite mud, its preparation method and application, in order to solve the technical problem that existing muds are difficult to simultaneously meet engineering performance requirements, be environmentally friendly and have good salt resistance.

[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a modified bentonite slurry, which comprises, by mass parts: 100 parts sodium bentonite, 0.5 parts anhydrous sodium carbonate, 1-5 parts gum arabic, 0.1-2 parts xanthan gum, and 1000 parts water.

[0007] Furthermore, the fineness of the sodium-based bentonite is 400-500 mesh.

[0008] Furthermore, the modified bentonite slurry has a viscosity of 40-55 s and an API filtration loss of ≤11 mL.

[0009] Furthermore, the modified bentonite slurry has a viscosity retention rate of ≥85% and an API filtration loss change of ≤2mL.

[0010] This invention also discloses a method for preparing the above-mentioned modified bentonite slurry, comprising the following steps: S1: Add sodium bentonite and anhydrous sodium carbonate to water and stir to obtain the basic slurry; S2: While maintaining stirring, add gum arabic and xanthan gum to the base slurry, continue stirring, and then perform post-treatment to obtain the slurry for modified bentonite.

[0011] Furthermore, in S1, the stirring speed is 1500~1800 rpm, and the time is 30~35 min.

[0012] Furthermore, in S2, the stirring speed is 1500~1800 rpm and the stirring time is 20~30 min.

[0013] Furthermore, in S2, the post-processing involves sequentially performing a settling and stirring process.

[0014] Furthermore, the standing period is 24-30 hours at room temperature.

[0015] The present invention also discloses the application of the above-mentioned modified bentonite mud in drilling engineering or pile foundation engineering.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a modified bentonite mud, comprising sodium-based bentonite, anhydrous sodium carbonate, gum arabic, and xanthan gum. Xanthan gum, in conjunction with the other components, utilizes its abundant carboxylate groups in its side chains to form stable ion bridges with the large number of sodium ions between bentonite particles, effectively blocking water molecule permeation pathways and significantly reducing filtration loss. Furthermore, it exhibits excellent salt resistance due to its strong binding capacity to sodium ions. Gum arabic, in conjunction with the other components, primarily forms a hydrogen bond network with the bentonite particle surface through its main chain hydroxyl groups, significantly increasing mud viscosity. A small amount of carboxylate groups at the ends of its branches can also form ion bridges with sodium ions, assisting in reducing filtration loss; however, the degree of bridging is limited, and some free sodium ions are easily absorbed by calcium ions in the formation. Because of its substitution properties, its salt resistance is relatively weak when used alone. In addition, the hydrophobic peptide chains in the gum arabic molecules can be anchored to the edges of the bentonite interlayers through van der Waals forces, inhibiting excessive hydration and swelling between layers, and further assisting in blocking water permeation channels. Secondly, xanthan gum and gum arabic work synergistically through hydrogen bonds and ion bridging to jointly construct a more dense and stable three-dimensional network structure, which not only achieves a balance between thickening and filtration loss reduction, but also uses the strong ionic binding ability of xanthan gum to compensate for the shortcomings of gum arabic in salt resistance, so that the composite mud can be comparable to or better than traditional CMC mud in key performance. The modified bentonite mud disclosed in this invention solves the technical problem that existing muds cannot simultaneously meet engineering performance requirements, be environmentally friendly, and have good salt resistance.

[0017] Furthermore, analysis based on pore water pressure monitoring and filtration behavior modeling revealed that the bentonite mud of this invention exhibits a gradual increase in pore pressure and a moderate peak pressure during the initial pressurization phase, followed by a rapid decrease and stabilization at a low level, reflecting rapid mud film formation and a dense structure. Simultaneously, the filtration behavior model further demonstrates that its total filtration loss is significantly lower than that of traditional CMC mud. These data collectively validate that the mud of this invention demonstrates comparable or even superior engineering performance to traditional CMC mud in terms of film formation rate, filtration control, and formation stability, showcasing high reliability and environmental friendliness.

[0018] Furthermore, according to relevant experimental results, the bentonite mud of the present invention has comparable performance to traditional CMC-containing mud in terms of viscosity and API filtration loss, and some formulations perform even better; in particular, the AH5 formulation exhibits superior filtration loss reduction performance and mud film quality. Attached Figure Description

[0019] Figure 1 This is a diagram illustrating the mechanism of action of gum arabic in the components of this invention. Figure 2 This is a diagram of the mud permeation film formation system of the present invention; Figure 3 This is a real-world illustration of the mud film type of the present invention. Detailed Implementation

[0020] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0021] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0022] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0023] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0024] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0025] This invention provides a modified bentonite slurry, the composition of which, by mass parts, comprises: 1000 parts water, 100 parts sodium bentonite, 0.5 parts anhydrous sodium carbonate, 1-5 parts gum arabic, and 0.1-2 parts xanthan gum; wherein the sodium bentonite has a fineness of 400 mesh (Example source: Sichuan Renshou Xingda Industry and Trade Co., Ltd.).

[0026] This invention also discloses a method for preparing the above-mentioned modified bentonite slurry, comprising the following steps: Add 100 parts sodium-based bentonite and 0.5 parts anhydrous sodium carbonate to 1000 parts by weight of clean water. Turn on a high-speed mixer and stir at 1800 rpm for 30 minutes to form a uniform base slurry. While stirring, add 1-5 parts gum arabic and 0.1-2 parts xanthan gum to the base slurry in sequence (the order of addition is not important). Continue stirring at high speed for 20-30 minutes to ensure that the gum arabic and xanthan gum are completely dissolved and evenly dispersed. After the resulting slurry has been allowed to stand at 25°C for 24 hours, stir again at a speed of not less than 1500 rpm for 5 minutes to obtain the bentonite slurry.

[0027] To clarify the performance differences between the gum arabic selected in this invention and the existing CMC technology, a comparative experiment was conducted. The basic mud mixture ratio was: 1000 mL water, 100 g sodium bentonite, and 0.5 g anhydrous sodium carbonate. The property data of the basic mud are shown in Table 1.

[0028] Table 1. Determination of Basic Mud Properties

[0029] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0030] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0031] Example 1 A method for preparing modified bentonite mud includes the following steps: Add 100 parts sodium bentonite and 0.5 parts anhydrous sodium carbonate to 1000 parts by weight of clean water, turn on the high-speed mixer and stir at 1800 rpm for 30 minutes to form a uniform base slurry. While maintaining stirring, add 1.0 part of gum arabic and 0.1 part of xanthan gum to the base slurry, and continue stirring at high speed for 30 minutes to ensure that the gum arabic and xanthan gum are completely dissolved and evenly dispersed. After the resulting slurry is allowed to stand at 25°C for 24 hours, it is stirred again at a speed of not less than 1500 rpm for 5 minutes to obtain the modified bentonite slurry, which is denoted as compound slurry AH1.

[0032] Example 2 A method for preparing modified bentonite mud includes the following steps: Add 100 parts sodium bentonite and 0.5 parts anhydrous sodium carbonate to 1000 parts by weight of clean water, turn on the high-speed mixer and stir at 1800 rpm for 30 minutes to form a uniform base slurry. While maintaining stirring, add 1.2 parts of gum arabic and 0.3 parts of xanthan gum to the base slurry, and continue stirring at high speed for 30 minutes to ensure that the gum arabic and xanthan gum are completely dissolved and evenly dispersed. After the resulting slurry is left to stand at 25°C for 24 hours, stir again at a speed of not less than 1500 rpm for 5 minutes to obtain modified bentonite slurry, which is denoted as compound slurry AH3.

[0033] Example 3 A method for preparing modified bentonite mud includes the following steps: Add 100 parts sodium bentonite and 0.5 parts anhydrous sodium carbonate to 1000 parts by weight of clean water, turn on the high-speed mixer and stir at 1800 rpm for 30 minutes to form a uniform base slurry. While maintaining stirring, add 1.4 parts of gum arabic and 0.1 parts of xanthan gum to the base slurry, and continue stirring at high speed for 30 minutes to ensure that the gum arabic and xanthan gum are completely dissolved and evenly dispersed. After the resulting slurry is allowed to stand at 25°C for 24 hours, it is stirred again at a speed of not less than 1500 rpm for 5 minutes to obtain modified bentonite slurry, which is denoted as compound slurry AH5.

[0034] Comparative Example 1 A method for preparing modified bentonite mud includes the following steps: Add 100 parts sodium bentonite and 0.5 parts anhydrous sodium carbonate to 1000 parts by weight of clean water, turn on the high-speed mixer and stir at 1800 rpm for 30 minutes to form a uniform base slurry. While maintaining stirring, add 1.5 parts of gum arabic and 0 parts of xanthan gum to the base slurry, and continue stirring at high speed for 30 minutes to ensure that the gum arabic and xanthan gum are completely dissolved and evenly dispersed. After the resulting slurry has been allowed to stand at 25°C for 24 hours, it is stirred again at a speed of not less than 1500 rpm for 5 minutes to obtain modified bentonite slurry, which is denoted as compound slurry AH6.

[0035] Comparative Example 2 The mud formulation for this comparative example is: 1.5g of CMC (carboxymethyl cellulose) added. This mud, prepared according to the aforementioned method, is used for performance comparison with the various embodiments of the present invention.

[0036] Table 2 Viscosity and Loss Rate of Examples and Comparative Examples

[0037] To verify the actual engineering performance of the environmentally friendly mud of this invention, a standard mud penetration film-forming test was conducted. For example... Figure 2 The experimental system shown consists of four main parts: a mud permeation column, a pressurization device, a pressure regulating device, and a data acquisition device. The mud permeation column is a custom-made acrylic tube with an inner diameter of 300 mm, allowing for clear observation of the process. Data acquisition uses an electronic scale to record the amount of water lost in real time, and four pore water pressure sensors placed at different heights on the column to monitor pressure changes within the formation.

[0038] Comparative Example 3: Compound Mud PENG The mud formula for this comparative example is: mud prepared according to the aforementioned method, without any additives.

[0039] Comparative Example 4: Compound Drilling GUA The mud formulation for this comparative example is: adding a suitable amount of guar gum. This mud, prepared according to the aforementioned method, is used to compare its performance with that of the embodiments of the present invention.

[0040] Comparative Example 5: YAMA Compound Mud The mud formulation for this comparative example is: adding a suitable amount of flaxseed gum. This mud, prepared according to the aforementioned method, is used to compare its performance with that of the embodiments of the present invention.

[0041] The experiment used several optimized compound muds (AH1, AH3, AH5, AH6) from this invention for comparison with traditional CMC muds, other plant-based gum muds (guar gum muds, flaxseed gum muds), and additive-free base muds. The formation material consisted of uniformly graded standard sand, which was filled and saturated to form a 300 mm thick test formation.

[0042] During the experiment, 150 mm high mud was injected into the prepared formation, and then a constant pressure of 200 kPa was applied and maintained to simulate the working conditions on the engineering site. At the same time, data on filtration loss and pore water pressure were collected.

[0043] Analysis of filtration loss showed that different additives significantly affected the film-forming properties of the mud. Table 3 shows that the base mud without additives formed the worst quality mud film, which ruptured rapidly under pressure. While guar gum and linseed gum muds could eventually form a film, the process was slow and resulted in high filtration loss. In contrast, CMC mud and the compound mud of this invention performed excellently, rapidly forming a dense, cake-like mud film. Figure 3 As shown. Effectively prevents further slurry loss. Of particular note is that the total filtration loss of the preferred formulation AH5 (1.4 parts gum arabic + 0.1 parts xanthan gum) of this invention is significantly lower than that of conventional CMC slurry, demonstrating its superior filtration loss reduction performance.

[0044] Table 3 Actual Filtration Loss

[0045] The changes in pore water pressure further revealed the formation quality and stability of the mud film. Table 4 shows that all muds experienced a rapid increase in pore water pressure to a peak value during the initial pressurization phase. Muds with poor performance (such as base mud and guar gum mud) exhibited extremely high peak pressures, large curve fluctuations, and even mud film rupture. In contrast, the peak pore pressures of CMC mud and the compound mud of this invention were moderate and rapidly decreased, stabilizing at extremely low levels. Notably, the peak pressure and stability values ​​of AH5 mud were very close to those of CMC mud, indicating that both were essentially equivalent in maintaining the stability of the excavation face.

[0046] Table 4 Peak Pore Water Pressure

[0047] In summary, the permeation film formation test demonstrates from two key dimensions—filtration loss control capability and pore water pressure stability—that the environmentally friendly compound mud provided by this invention, especially the AH5 formulation, can not only completely replace traditional CMC mud but also surpass it in core performance. At the same time, it is environmentally friendly and has extremely high engineering application value.

[0048] Figure 1 To illustrate the mechanism of action of gum arabic, the figure shows that after adding gum arabic to sodium-based bentonite slurry, its hydroxyl groups form hydrogen bonds with the negatively charged siloxane surface of the bentonite particles, causing the solution to gel and increase viscosity. After the branched carboxylic acid groups dissociate, they bond with the Na+ in the bentonite layers. + Ion pairs are formed, and hydrophobic peptide chains are embedded between the particle layers through van der Waals forces. Together, they block water molecule permeation to reduce filtration loss.

[0049] This invention uses sodium-based bentonite as the core, combined with anhydrous sodium carbonate, gum arabic, and xanthan gum to construct a composite system. Through the synergistic effect of each component, it ensures that the mud viscosity (40~55s) and API filtration loss (≤11mL) meet engineering requirements. Furthermore, by leveraging the environmentally friendly properties of the natural polymers gum arabic and xanthan gum, it avoids the problems of industrial salt byproduct accumulation, poor biodegradability, and heavy metal pollution associated with traditional CMC additives, aligning with the concept of green engineering. The selection of 400~500 mesh sodium-based bentonite and precise composition... The formulation ensures excellent stability of the drilling mud, with a viscosity retention rate of ≥85% and an API filtration loss change of ≤2mL, maintaining long-term borehole wall stability and lubrication performance. The preparation method clearly defines the stirring speed (1500~1800 rpm), time parameters, and the settling-stirring post-treatment process, making it simple, controllable, and easy for industrial production. It is suitable for drilling and pile foundation engineering projects, ensuring both construction efficiency and safety while reducing the environmentally friendly treatment cost of waste drilling mud, combining technical practicality and environmental friendliness. This invention discloses a modified bentonite drilling mud that solves the technical problem of existing drilling muds failing to simultaneously meet engineering performance requirements, be environmentally friendly, and possess good salt resistance.

[0050] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A modified bentonite mud, characterized in that, The components of the modified bentonite mud slurry in mass parts include: sodium-based bentonite 100 parts, anhydrous sodium carbonate 0.5 parts, gum arabic 1-5 parts, xanthan gum 0.1-2 parts, and water 1000 parts.

2. A modified bentonite mud according to claim 1, characterized in that, The fineness of the sodium-based bentonite is 400-500 mesh.

3. A modified bentonite mud according to claim 1, wherein The viscosity of the modified bentonite mud slurry is 40-55 s, and the API fluid loss is ≤11 mL.

4. A modified bentonite mud according to claim 1, wherein The viscosity retention rate of the modified bentonite mud slurry is ≥85%, and the API fluid loss change amount is ≤2 mL.

5. A method of preparing a modified bentonite clay slurry according to any one of claims 1 to 4, characterised in that, The method comprises the following steps: S1: stirring sodium-based bentonite and anhydrous sodium carbonate in water to obtain a base slurry; S2: while keeping stirring, adding gum arabic and xanthan gum to the base slurry, continuing to stir, and then performing post-processing to obtain the modified bentonite mud slurry.

6. The method of preparing a modified bentonite clay slurry of claim 5, wherein, In S1, the stirring speed is 1500-1800 rpm, and the time is 30-35 min.

7. The method for preparing modified bentonite slurry according to claim 5, characterized in that, In S2, the speed for continuing to stir is 1500-1800 rpm, and the time is 20-30 min.

8. The method for preparing modified bentonite slurry according to claim 5, characterized in that, In S2, the post-processing is sequentially standing and stirring.

9. The method of preparing a modified bentonite clay slurry of claim 5, wherein, The standing is at room temperature for 24-30 h.

10. Application of the modified bentonite mud slurry in any one of claims 1-4 in drilling engineering or pile foundation engineering.

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