An environmentally friendly recyclable drilling mud for municipal directional drilling, its preparation process and application

Abstract

This invention specifically discloses an environmentally friendly recyclable drilling mud for municipal directional drilling, its preparation process, and its application. The mud is composed of water, bio-enzyme-activated modified bentonite, polyaspartic acid derivatives, industrial solid waste fillers, plant extracts, a compound corrosion inhibitor, and functional regulators in specific mass percentages. Its preparation process includes pretreatment, base mud preparation, functional addition, and adjustment optimization steps; the application process covers construction grouting, slag removal, recycling, and final biodegradation treatment. This invention, through the synergistic utilization of environmentally friendly and biodegradable core components and industrial solid waste, endows the mud with excellent biodegradability. Waste mud can be discharged or reused after simple treatment. This mud system has stable performance and can be recycled more than 5 times. It has significant wall protection and anti-collapse effects in complex strata such as silty clay and sand layers, effectively controlling surface subsidence while significantly reducing water consumption, raw material costs, and waste disposal costs, achieving green, low-carbon, economical, safe, and efficient municipal directional drilling.

Description

Technical Field

[0001] This invention relates to the field of municipal engineering technology, specifically to a mud system for trenchless construction in horizontal directional drilling (HDD) in complex urban environments, which is particularly suitable for green construction scenarios involving complex strata such as silty clay, sand, and artificial fill. Background Technology

[0002] In municipal engineering projects such as urban power grid renovation and old pipeline network upgrading, horizontal directional drilling trenchless construction has become the preferred technology due to its minimal impact on ground traffic and residents' lives. However, the drilling mud used in traditional construction has significant drawbacks: First, it has poor environmental performance. The drilling mud often contains chemical treatment agents that are difficult to biodegrade, such as certain polymers and dichromates. If the waste drilling mud generated after construction is not properly disposed of, it can easily cause long-term pollution to the soil and groundwater, and the cost of compliant treatment is high. Second, it has a low recycling rate. The performance of the drilling mud degrades rapidly during the process of carrying drill cuttings and stabilizing the borehole wall, and it is often used as a disposable consumable, resulting in a large waste of water resources and raw materials. Third, it has insufficient adaptability to geological formations. In complex and heterogeneous formations such as silty clay that softens when exposed to water and easily dispersed sand layers commonly found in urban areas, traditional drilling mud cannot provide sufficient wall protection and anti-collapse capacity while meeting environmental protection requirements, which can easily lead to engineering risks such as borehole wall instability and excessive ground settlement.

[0003] With increasingly stringent environmental regulations, the environmental pollution caused by traditional drilling mud has become a key bottleneck restricting the green development of trenchless technology. Therefore, there is an urgent need to develop a new type of drilling mud system that combines excellent environmental performance, high recycling efficiency, and strong adaptability to complex geological formations to achieve green, low-carbon, and sustainable development of municipal directional drilling operations. Summary of the Invention

[0004] This invention aims to overcome the shortcomings of existing technologies and provide an environmentally friendly, recyclable drilling mud for municipal directional drilling, along with its preparation and application process. The core components of this mud system are green and biodegradable, allowing for multiple recycling cycles. It also provides excellent borehole wall stability in complex formations such as silty clay and sand layers, thereby reducing environmental pollution, conserving resources, and controlling construction risks and costs.

[0005] To achieve the above objectives, the present invention provides an environmentally friendly and recyclable drilling mud for municipal directional drilling, which is composed of the following components by mass percentage: Water: 30%-40%; Modified bentonite: 8%-12%; Biodegradable biopolymers: 2%-5%; Industrial solid waste filler: 15%-25%; Environmentally friendly corrosion inhibitor: 0.5%-1%; The remainder is a functional regulator.

[0006] Furthermore, the modified bentonite is bentonite that has undergone bio-enzyme activation treatment. Unlike traditional chemical modification using soda ash (sodium carbonate) or polyacrylamide, bio-enzyme activation is a green and mild biocatalytic process. Enzyme treatment does not introduce inorganic salts or difficult-to-degrade synthetic chemicals, ensuring the biocompatibility and ultimate degradability of the mud system from the source. Bioenzymes, such as specific cellulases or proteases, selectively decompose organic impurities between or on the surface of bentonite mineral particles and gently erode particle edges. This plays two key roles: first, purification, improving the purity of bentonite and making its effective component, montmorillonite, easier to hydrate; second, micropore creation, increasing specific surface area and interlayer active sites. This significantly improves the hydration and swelling efficiency, dispersibility, and final mud yield of bentonite, achieving the required viscosity and filtration loss control with a smaller dosage. Bentonite forms the skeleton of the mud, primarily providing base mud viscosity and forming a low-permeability filter cake to stabilize the pore walls. If the mud content is below 8%, the base mud viscosity is insufficient, failing to effectively suspend drill cuttings and solid particles, resulting in poor filter cake quality. If it is above 12%, the mud viscosity is too high, leading to poor fluidity, a surge in pumping resistance, increased energy consumption, and potentially masking the effects of other functional components, making it uneconomical. The 8%-12% range ensures the formation of a sufficiently high-performance and economical base mud in most complex formations.

[0007] The biodegradable biopolymer is a polyaspartic acid derivative. Polyaspartic acid (PASP) and its derivatives are recognized as environmentally friendly water treatment agents that can be decomposed by microorganisms in the natural environment into water, carbon dioxide, and ammonium salts, without the risk of persistent pollution. This directly solves the fatal problem of traditional slurry commonly using synthetic polymers such as polyacrylamide (PAM) being difficult to degrade and causing environmental accumulation. The PASP derivative molecular chain contains abundant active groups such as carboxyl groups, which not only give it good thickening and water retention capabilities, but also allow it to form a stable composite structure with bentonite particles and industrial solid waste fillers through adsorption-bridging effects, enhancing overall suspension stability. Its molecular structure can be easily modified to adjust its temperature and salt resistance properties to meet the needs of different underground environments. The polymer is the backbone of the slurry, mainly playing a role in thickening, increasing shear strength, and reducing filtration loss. A content below 2% has no significant effect on modifying the slurry system and has limited improvement in sludge carrying capacity; a content above 5% significantly increases costs and may lead to excessively viscous slurry or even the formation of clumps, affecting fluidity and pumping efficiency, and excessive polymer may interfere with the dispersion of bentonite. A range of 2%-5% can significantly improve the performance of slag carrying and wall protection while maintaining good rheological properties and economy of the mud.

[0008] Furthermore, the industrial solid waste filler is fly ash and / or slag powder with a particle size ≤0.075mm; the functional regulator is a pH adjuster and a defoamer. The functional regulator includes a pH adjuster, such as food-grade potassium carbonate and sodium hydroxide, and a defoamer, such as a food-grade silicone defoamer, used to adjust the slurry system to its optimal working state.

[0009] Furthermore, the environmentally friendly corrosion inhibitor is a corrosion inhibitor formulated from plant extracts.

[0010] Furthermore, the environmentally friendly corrosion inhibitor is formulated from the following plant extracts in the indicated weight percentages: 40%–60% tea polyphenol extract, 20%–30% aloe polysaccharide extract, 10%–20% curcumin extract, and 5%–10% rosmarinic acid extract. The main components of the tea polyphenol extract are catechins, which possess excellent antioxidant and metal surface adsorption capabilities, effectively inhibiting electrochemical corrosion. The aloe polysaccharide extract exhibits synergistic film-forming and corrosion-inhibiting effects, enhancing the lubrication and protection of the drilling tools by the drilling mud. The curcumin extract has strong metal chelating ability, forming a protective layer on the metal surface and slowing down the corrosion rate. The rosmarinic acid extract, as a natural preservative, possesses antioxidant and antibacterial properties, preventing corrosion caused by microorganisms in the drilling mud system.

[0011] On the other hand, the present invention also provides a process for preparing the above-mentioned environmentally friendly and recyclable mud, characterized by comprising the following steps: S1. Pretreatment: Dry the industrial solid waste filler to a moisture content of ≤5% and pass it through a 100-300 mesh sieve; activate the modified bentonite by soaking it in a biological enzyme solution for 4-6 hours; S2. Preparation of base slurry: Add water to the mixing tank, slowly add modified bentonite at a speed of 800-1000 r / min, and stir for 10-30 minutes until completely dissolved; S3. Function addition: Add biodegradable biopolymer, industrial solid waste filler and environmentally friendly corrosion inhibitor in sequence, increase the speed to 1200-1500r / min and stir for 30-60 minutes; S4. Adjustment and optimization: Add functional regulators to adjust the pH of the mud to 8-10, defoam and let it stand for 10-30 minutes to obtain the finished mud.

[0012] This invention also provides an application process for directional drilling using the above-mentioned environmentally friendly recyclable mud, comprising the following steps: P1. Construction grouting: The finished mud is injected into the directional drilling hole through a high-pressure pump, and the grouting pressure is dynamically adjusted according to the stratum type. P2. Mud recovery: The slag-containing mud discharged from the borehole is sequentially treated by a vibrating screen and a centrifugal separator to remove slag and obtain recovered mud. P3. Regeneration treatment: Detect the viscosity and dynamic shear force of the recycled mud, add the corresponding components to the standard range, stir evenly, and reuse. P4. Waste disposal: After the mud has been recycled a set number of times, a biodegradation promoter is added, and after it has been allowed to stand and degrade, it is either discharged in an environmentally friendly manner or reused.

[0013] Furthermore, in step P1, the grouting pressure is adjusted according to the formation type: 0.8-1.2 MPa for silty clay formations and 1.2-1.8 MPa for sand formations.

[0014] Furthermore, in step P2, the vibrating screen is a 100-500 mesh screen, and the centrifugal separator rotates at a speed of 1000-3000 r / min.

[0015] Furthermore, in step P3, the viscosity standard is 18-25s, and the dynamic shear force standard is 15-25Pa; in step P4, the set number of cycles is more than 5 times.

[0016] The beneficial effects of this invention are: The core treatment agents—bio-enzyme-modified bentonite, polyaspartic acid derivatives, and plant-extract corrosion inhibitors—are all biodegradable or environmentally friendly materials, preventing persistent pollution from recalcitrant polymers and harmful additives found in traditional chemical sludge. Utilizing industrial solid waste such as fly ash and slag powder as key fillers achieves waste-to-waste treatment. After simple biodegradation and accelerated treatment, the waste sludge's key indicators, such as chemical oxygen demand and suspended solids, meet environmental emission or agricultural reuse standards, completely solving the problems of difficult, costly, and high-risk disposal of traditional waste sludge.

[0017] Through optimized formulation and regeneration process, the slurry's slag-carrying capacity and wall-protecting performance can be controlled to decay, enabling it to be recycled at least 5 times, which is significantly better than traditional slurry. Recycling reduces fresh water consumption by more than 60%, while also reducing the continuous input of raw materials such as bentonite and polymers.

[0018] The synergistic effect of modified bentonite, biopolymers, and industrial solid waste fillers forms a dense, tough, low-permeability filter cake on the borehole wall. Engineering simulations and applications show that 100% borehole wall stability can be achieved in easily collapsing sand layers and easily narrowed silty clay layers. The excellent wall protection and lubrication properties of the mud system can stably control the surface settlement caused by construction within 15 mm, meeting the stringent requirements for construction deformation in sensitive urban areas. The formula is environmentally friendly and mild, with a moderate pH value, and combined with plant-based corrosion inhibitors, it can effectively reduce corrosion of drilling tools and extend equipment life. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention. The following embodiments are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention.

[0020] Example 1: Preparation of Environmentally Friendly Recyclable Sludge Weigh the following raw materials, with the following mass percentages for each component: water 34%, modified sodium bentonite activated by cellulase 10%, polyaspartic acid (molecular weight 5000) 3%, dried and sieved Grade I fly ash 20%, compound corrosion inhibitor of plant extracts (tea polyphenols 50%, aloe polysaccharides 25%, curcumin 15%, rosmarinic acid 10%) 0.8%, and functional regulators (including food-grade pH adjuster potassium carbonate and food-grade organosilicon defoamer) totaling 32.2%.

[0021] Preparation process: (1) Dry the fly ash to a moisture content of 3% and pass it through a 200-mesh sieve; soak the bentonite in a 0.5% cellulase solution for 5 hours.

[0022] (2) Add water to the mixing vessel and stir at 900 r / min. Slowly add the activated bentonite and stir for 30 minutes.

[0023] (3) Add polyaspartic acid, fly ash and plant corrosion inhibitor in sequence, increase the speed to 1300 r / min and stir for 60 minutes.

[0024] (4) Add potassium carbonate solution to adjust the pH of the mud to 9.0, add defoamer, continue stirring for 5 minutes, and let stand for 20 minutes to obtain finished mud A. Its properties were tested: density 1.25 g / cm³. 3 Marshall funnel viscosity 22s, API filtration loss 12mL, dynamic shear force 18Pa.

[0025] Recycling and Regeneration of Mud The mud A prepared in Example 1 was applied in a directional drilling crossing project of a municipal power pipeline (the strata were mainly interbedded silty clay and fine sand).

[0026] (1) Construction: Use a mud pump to pump mud A into the hole at a pressure of 1.0-1.5MPa.

[0027] (2) Recovery: The returned mud is processed by a 100-mesh vibrating screen and a centrifuge (3000r / min) to obtain recovered mud.

[0028] (3) Regeneration: The viscosity of the recycled mud was 16s and the dynamic shear force was 12Pa. Polyaspartic acid and water were added, and after high-speed stirring, the performance was restored to a viscosity of 20s and a dynamic shear force of 17Pa, and it was put back into use.

[0029] Comparative Example 1 Compared with Example 1, the only difference is that the bentonite is not modified with bio-enzymes, while the other processes are the same as in Example 1.

[0030] Comparative Example 2 Compared with Example 1, the only difference is that there is no industrial solid waste filler; the other processes are the same as in Example 1.

[0031] Comparative Example 3 Compared with Example 1, the only difference is that the polymer is the non-degradable polymer PAM, while the other processes are the same as in Example 1.

[0032] Comparative Example 4 Compared with Example 1, the only difference is that the corrosion inhibitor is a traditional chemical corrosion inhibitor, while the other processes are the same as in Example 1.

[0033] Comparative Example 5 Compared with Example 1, the only difference is that it is not cyclical and is used only once; the other processes are the same as in Example 1.

[0034] Comparative Example 6 Compared with Example 1, the only difference is that the mass fraction of the bio-enzyme modified bentonite is 3%, while the other processes are the same as in Example 1.

[0035] Comparative Example 7 Compared with Example 1, the only difference is that the mass fraction of the bio-enzyme modified bentonite is 15%, while the other processes are the same as in Example 1.

[0036] Comparative Example 8 Compared with Example 1, the only difference is that the mass fraction of the biodegradable biopolymer is 0.5%, while the other processes are the same as in Example 1.

[0037] Comparative Example 9 Compared with Example 1, the only difference is that the mass fraction of the biodegradable biopolymer is 10%, while the other processes are the same as in Example 1.

[0038] The testing focused on the four core objectives of this invention: environmental friendliness, recyclability, geological adaptability, and economic efficiency. The main test items included: Initial properties: density, Marsh funnel viscosity, API filtration loss, dynamic shear force.

[0039] Cyclic stability: Simulate construction-recycling-regeneration cycle and record the degradation of key performance characteristics up to the point of failure (defined as viscosity <18s or >28s, or dynamic shear force <10Pa).

[0040] Environmental performance: After the waste mud is treated with a biodegradation accelerator for 48 hours, the chemical oxygen demand (COD) and suspended solids (SS) are tested.

[0041] Engineering simulation performance: The stability of the borehole wall and the surface settlement were tested in a simulated trench with interlayered silty clay and fine sand.

[0042] Corrosion inhibition rate: The corrosion inhibition rate of N80 steel sheets was tested using the static hanging plate method (refer to standard SY / T 5273).

[0043] Example and Comparative Experimental Data Table 1: Comparison of Initial Performance and Environmental Performance

[0044] Table 2: Engineering Simulation Test Results

[0045] Experimental data analysis The experimental data above show that the initial viscosity (18s) and dynamic shear stress (12Pa) of the bentonite in Comparative Example 1 without bio-enzyme modification are significantly lower than those in Example 1 (22s, 18Pa), with higher API filtration loss and only 3 cycles. This demonstrates that bio-enzyme activation treatment can effectively improve the hydration efficiency and dispersibility of bentonite, and is a key technology for obtaining excellent initial rheological properties, low filtration loss, and high cycle durability. In Comparative Example 2, the suspended solids (SS) of the waste mud without solid waste filler reached as high as 110 mg / L, far exceeding Example 1 and the emission standards, and its pore wall stability and sedimentation control were weaker than those in Example 1. This indicates that fly ash / slag powder not only acts as a filler, but its microparticle effect plays an irreplaceable role in enhancing the suspension stability of mud, forming a dense filter cake to control solid-phase separation, and stabilizing the pore wall. Comparative Example 3, while exhibiting good engineering performance with a pore wall stability rate of 95%, a settling rate of 15 mm, and a certain degree of recyclability (4 times), showed severely excessive COD (520 mg / L) and SS (380 mg / L) in its waste mud, revealing the fatal flaw of traditional synthetic polymers being difficult to biodegrade and causing serious secondary pollution. In contrast, Example 1, with comparable or even superior performance, achieved complete environmental degradability. Comparative Example 4, using a traditional chemical corrosion inhibitor, had a corrosion inhibition rate of 68%, far lower than the 85% in Example 1, and its waste mud had a higher pollution load. This indicates that the plant extract compound corrosion inhibitor achieves efficient equipment protection while also possessing excellent environmental compatibility. The single-use performance data of Comparative Example 5 was almost identical to that of Example 1 during its first use. This highlights that one of the core advantages of this invention is not simply improving single-use performance, but rather achieving multiple recovery and utilization of performance through a regeneration process. Example 1, with ≥5 cycles, is equivalent to saving 4 batches of new mud material and processing costs, resulting in significant economic benefits.

[0046] Comparative Example 6, with 3% bio-enzyme-modified bentonite, showed a comprehensive deterioration in all properties, including a viscosity of 14s, excessively low dynamic shear force, and an extremely high filtration loss of 30mL. This resulted in highly unstable pore walls, a stability rate of only 70%, severe settling, and near-complete inability to circulate. This demonstrates that insufficient dosage cannot form an effective structure. Comparative Example 7, with 15% dosage, resulted in excessively viscous mud. While it provided good wall protection, its poor fluidity could affect pumping efficiency, and the marginal benefits of performance improvement were no longer economical.

[0047] Comparative Example 8, with a biodegradable biopolymer dosage of 0.5%, had insufficient slag-carrying capacity and poor filtration control, leading to uncontrolled settling and weak wall protection during the project. Comparative Example 9, with a dosage of 10%, resulted in excessively viscous mud. Although it provided good wall protection, its poor fluidity led to weaker settling control than Example 1, and a reduction in the number of cycles.

[0048] Experimental data fully demonstrate that this invention, through its unique component system and optimized ratio of bio-enzyme-modified bentonite, polyaspartic acid derivatives, industrial solid waste fillers, and plant corrosion inhibitors, successfully achieves positive synergy among the components, forming an excellent balance in terms of environmental friendliness, recyclability, engineering adaptability, and economy. All comparative examples, by changing a single variable, exhibited performance shortcomings in different dimensions, conversely confirming the non-obviousness and overall inventiveness of this invention's technical solution. This mud system effectively solves the core pain points of traditional mud systems—heavy pollution, high consumption, and poor adaptability—and possesses significant value for widespread application.

[0049] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An environmentally friendly recyclable slurry for municipal directional drilling construction, characterized by, Composed of the following components by mass percentage composition: Water: 30%-40%; Modified bentonite: 8%-12%; Biodegradable biopolymers: 2%-5%; Industrial solid waste filler: 15%-25%; Environmentally friendly corrosion inhibitor: 0.5%-1%; The remainder is a functional regulator.

2. The environmentally friendly recyclable slurry according to claim 1, wherein, The modified bentonite is bentonite that has been activated by bio-enzymes; the biodegradable biopolymer is a polyaspartic acid derivative.

3. The environmentally friendly recyclable slurry according to claim 1, wherein, The industrial solid waste filler is fly ash and / or slag powder with a particle size ≤0.075mm; the functional regulator is a pH regulator and a defoamer.

4. The environmentally friendly recyclable slurry according to claim 1, characterized in that, The environmentally friendly corrosion inhibitor is a compound of plant extracts.

5. The environmentally friendly recyclable slurry according to claim 4, characterized in that, The environmentally friendly corrosion inhibitor is a compound of plant extracts in the following weight percentages: 40%–60% tea polyphenol extract, 20%–30% aloe polysaccharide extract, 10%–20% curcumin extract, and 5%–10% rosmarinic acid extract.

6. A process for preparing environmentally friendly recyclable sludge according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Pretreatment: Dry the industrial solid waste filler to a moisture content of ≤5% and pass it through a 100-300 mesh sieve; activate the modified bentonite by soaking it in a biological enzyme solution for 4-6 hours; S2. Preparation of base slurry: Add water to the mixing tank, slowly add modified bentonite at a speed of 800-1000 r / min, and stir for 10-30 minutes until completely dissolved; S3. Function addition: Add biodegradable biopolymer, industrial solid waste filler and environmentally friendly corrosion inhibitor in sequence, increase the speed to 1200-1500r / min and stir for 30-60 minutes; S4. Adjustment and optimization: Add functional regulators to adjust the pH of the mud to 8-10, defoam and let it stand for 10-30 minutes to obtain the finished mud.

7. An application process for directional drilling using the environmentally friendly recyclable mud as described in any one of claims 1-5, characterized in that, Includes the following steps: P1. Construction grouting: The finished mud is injected into the directional drilling hole through a high-pressure pump, and the grouting pressure is dynamically adjusted according to the stratum type. P2. Mud recovery: The slag-containing mud discharged from the borehole is sequentially treated by a vibrating screen and a centrifugal separator to remove slag and obtain recovered mud. P3. Regeneration treatment: Detect the viscosity and dynamic shear force of the recycled mud, add the corresponding components to the standard range, stir evenly, and reuse. P4. Waste disposal: After the mud has been recycled a set number of times, a biodegradation promoter is added, and after it has been allowed to stand and degrade, it is either discharged in an environmentally friendly manner or reused.

8. The application process according to claim 7, characterized in that, In step P1, the grouting pressure is adjusted according to the formation type: 0.8-1.2 MPa for silty clay formations and 1.2-1.8 MPa for sand formations.

9. The application process according to claim 7, characterized in that, In step P2, the vibrating screen is a 100-500 mesh screen, and the centrifuge speed is 1000-3000 r / min.

10. The application process according to claim 7, characterized in that, In step P3, the viscosity standard is 18-25s, and the dynamic shear force standard is 15-25Pa; in step P4, the set number of cycles is more than 5 times.

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