Multi-scene self-adaptive gradient composite drilling fluid slurry and preparation method thereof

Abstract

The invention discloses multi-scene self-adaptive gradient composite drilling fluid slurry and a preparation method of the multi-scene self-adaptive gradient composite drilling fluid slurry. The multi-scene self-adaptive gradient composite drilling fluid slurry is prepared from 20%-30% of modified sepiolite, 12%-25% of sodium red clay, 8%-15% of a nanofiller-red clay compound, 4%-8% of a pH response type filtrate reducer, 3%-6% of an environment-friendly lubricant, 0.5%-2% of a bio-based antibacterial agent and the balance of deionized water. The modified sepiolite is modified by grafting acrylic acid with a silane coupling agent; the nano filler-red clay compound is a compound formed by loading nano calcium carbonate on the surface of red clay; the pH response type filtrate reducer is a compound of polyaspartic acid and chitosan quaternary ammonium salt, or a compound of polyepoxysuccinic acid and chitosan quaternary ammonium salt; the environment-friendly lubricant is a modified vegetable oil microemulsion; the density of the multi-scene self-adaptive gradient composite drilling fluid slurry is 1.3-1.7 g / cm < 3 >. The invention solves the problem that the existing drilling fluid is insufficient in salt resistance and environmental protection property.

Description

Technical Field

[0001] This invention relates to the field of drilling fluid technology, specifically to a multi-scenario adaptive gradient composite drilling fluid mud and its preparation method. Background Technology

[0002] Drilling fluid is a general term for various circulating fluids that fulfill the needs of drilling operations through multiple functions. Drilling fluids can be classified according to their composition into water, mud, clay-free flushing fluid, emulsions, foam, and compressed air, among others. Water is the earliest type of drilling fluid used; it requires no treatment, is convenient to use, and is suitable for areas with intact rock formations and abundant water sources. Mud is a widely used drilling fluid, primarily suitable for unstable rock formations with loose, fractured, easily collapsing, or water-swelling and spalling characteristics.

[0003] Existing drilling fluids suffer from problems such as insufficient salt resistance, poor high-temperature stability, limited wall protection options, and environmental deficiencies. Specifically, traditional bentonite is prone to ion exchange failure in high-salt formations, leading to a sharp drop in viscosity and insufficient salt resistance; sepiolite-based drilling fluids are prone to dehydration and hardening above 180°C, losing their rheological properties and exhibiting poor high-temperature stability; reliance on chemical inhibitors (such as KCl) to suppress shale hydration has limited effectiveness in sealing complex fracture formations, resulting in limited wall protection options; and the presence of oil-based or heavy metal additives (such as sulfonated lignite) pollutes the formation, failing to meet the requirements of green exploration. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, a multi-scenario adaptive gradient composite drilling fluid mud and its preparation method are provided to solve the problems of insufficient salt resistance and environmental friendliness of existing drilling fluids.

[0005] To achieve the above objectives, a multi-scenario adaptive gradient composite drilling mud is provided. By weight percentage, the multi-scenario adaptive gradient composite drilling mud includes 20-30% modified sepiolite, 12-25% sodium-modified red clay, 8-15% nanofiller-red clay composite, 4-8% pH-responsive filtration reducer, 3-6% environmentally friendly lubricant, 0.5-2% bio-based antibacterial agent, and the balance being deionized water. The modified sepiolite is modified by grafting acrylic acid onto a silane coupling agent. The nanofiller-red clay composite is a composite of nano-calcium carbonate supported on the surface of red clay. The pH-responsive filtration reducer is a complex of polyaspartic acid and chitosan quaternary ammonium salt, or a complex of polyepoxysuccinic acid and chitosan quaternary ammonium salt. The environmentally friendly lubricant is a modified vegetable oil microemulsion; The density of the multi-scenario adaptive gradient composite drilling fluid mud is 1.3~1.7 g / cm³. 3 .

[0006] Furthermore, the modified vegetable oil microemulsion is a modified rapeseed oil microemulsion, a modified coconut oil microemulsion, or a modified soybean oil microemulsion.

[0007] Furthermore, the bio-based antibacterial agent is tea tree oil extract, rosemary extract, or Bacillus extracellular polysaccharide.

[0008] Furthermore, it includes 240 parts by weight of modified sepiolite, 140 parts by weight of sodium red clay, 90 parts by weight of nanofiller-red clay complex, 70 parts by weight of polyaspartic acid and chitosan quaternary ammonium salt complex, 50 parts by weight of modified rapeseed oil microemulsion, 10 parts by weight of tea tree oil extract and 390 parts by weight of deionized water.

[0009] Furthermore, it includes 260 parts by weight of modified sepiolite, 130 parts by weight of sodium red clay, 110 parts by weight of nanofiller-red clay complex, 50 parts by weight of polyaspartic acid and chitosan quaternary ammonium salt complex, 60 parts by weight of modified rapeseed oil microemulsion, 5 parts by weight of tea tree oil extract and 385 parts by weight of deionized water.

[0010] Furthermore, it includes 280 parts by weight of modified sepiolite, 180 parts by weight of sodium red clay, 150 parts by weight of nanofiller-red clay complex, 80 parts by weight of polyaspartic acid and chitosan quaternary ammonium salt complex, 40 parts by weight of modified rapeseed oil microemulsion, 8 parts by weight of tea tree oil extract and 342 parts by weight of deionized water.

[0011] Furthermore, it includes 220 parts by weight of modified sepiolite, 200 parts by weight of sodium red clay, 130 parts by weight of nanofiller-red clay complex, 30 parts by weight of polyepoxysuccinic acid and chitosan quaternary ammonium salt complex, 50 parts by weight of modified coconut oil microemulsion, 5 parts by weight of rosemary extract and 365 parts by weight of deionized water.

[0012] This invention provides a method for preparing multi-scenario adaptive gradient composite drilling mud, comprising the following steps: The modified sepiolite and sodium-modified red clay were mixed and stirred evenly to obtain the first dry material; The first dry material is mixed with a nanofiller-red clay composite to obtain a second dry material. Add a pH-responsive filtration reducer to the second dry material and stir until homogeneous to obtain the first wet material; An environmentally friendly lubricant was added to the first wet material and stirred evenly to obtain a second wet material; A multi-scenario adaptive gradient composite drilling mud is prepared by adding a bio-based antibacterial agent and deionized water to the second wet material and stirring evenly.

[0013] The beneficial effects of this invention lie in the fact that the multi-scenario adaptive gradient composite drilling mud of this invention constructs a novel composite material system through gradient composite and functionalized modification of sepiolite and red clay. Specifically, silane coupling agent (KH-550) is used to graft acrylic acid to modify sepiolite, improving its hydrophobic properties. Simultaneously, nano-sized calcium carbonate with a particle size of 20-50 nm is loaded onto the surface of red clay to enhance its plugging ability. The modified sepiolite and red clay possess both excellent shear resistance and adsorption properties. The synergistic effect of these modifications effectively achieves a comprehensive improvement in wellbore stability, filtration loss, and lubrication performance.

[0014] The multi-scenario adaptive gradient composite drilling fluid mud of this invention enhances wellbore protection, prevents wellbore collapse, ensures wellbore stability, and reduces the corrosion rate of seawater on the reinforcing cage and drill bit. Its cuttings-carrying capacity efficiently transports drilling cuttings to the surface, ensuring smooth drilling operations. Simultaneously, the multi-scenario adaptive gradient composite drilling fluid mud of this invention effectively seals formation fractures and pores, preventing drilling fluid loss.

[0015] Furthermore, the multi-scenario adaptive gradient composite drilling fluid mud of the present invention has high biodegradability and no heavy metal residues were detected. Detailed Implementation

[0016] The present application will now be described in further detail with reference to the embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit the invention.

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.

[0018] This invention provides a multi-scenario adaptive gradient composite drilling mud, which, by weight percentage, comprises 20-30% modified sepiolite, 12-25% sodium-modified red clay, 8-15% nanofiller-red clay composite, 4-8% pH-responsive filtration reducer, 3-6% environmentally friendly lubricant, 0.5-2% bio-based antibacterial agent, and the balance being deionized water.

[0019] Modified sepiolite was modified by grafting acrylic acid onto silane coupling agent (KH-550), with a grafting rate of ≥70%.

[0020] Sodium-treated red clay is prepared by sodium treatment of red clay with 3-10% Na2CO3, with an interlayer spacing of 0.8-1.5 nm.

[0021] The nanofiller-red clay composite is a composite of nano-calcium carbonate supported on the surface of red clay. Specifically, nano-calcium carbonate / silica is supported on red clay with a loading rate of 20-60% and a particle size of 5-50 nm.

[0022] pH-responsive filtration reducers are complexes of polyaspartic acid (PASP) and chitosan quaternary ammonium salt (CS-Q) (i.e., PASP-CS-Q complex) or complexes of polyepoxysuccinic acid and chitosan quaternary ammonium salt (i.e., PESA-Q). Specifically, when used in conventional formations (including clay or test layers) or loose sand / collapse-prone formations, the pH-responsive filtration reducer uses a complex of polyaspartic acid and chitosan quaternary ammonium salt.

[0023] When used in conventional formations, pH-responsive filtration reducers employ a complex of polyaspartic acid and chitosan quaternary ammonium salt. In clay formations, a pH 7-9 responsive type is used, primarily for reducing filtration loss, with a PASP:CS-Q ratio of 2.5:1 (mass ratio, the same below). In hard rock formations, a pH 8-10 responsive type is used, with a PASP:CS-Q ratio of 3:1, to reduce the erosion of the rock by the filtrate.

[0024] When used in loose sandy / collapsed formations, increasing the polyaspartic acid ratio in the polyaspartic acid-chitosan quaternary ammonium salt complex (PASP:CS-Q=5:1) enhances pH response sensitivity (rapidly reduces filtration loss at pH 8-10).

[0025] When used in environments with high temperature, high salt or environmental requirements, the pH-responsive filtration loss reducer uses a complex of polyepoxysuccinic acid and chitosan quaternary ammonium salt, and the PESA-chitosan quaternary ammonium salt complex (PESA-Q) has a salt filtration loss of ≤8mL (25% NaCl).

[0026] The environmentally friendly lubricant is a modified vegetable oil microemulsion. The modified vegetable oil microemulsion has a particle size of <100 nm and a biodegradability of >85%. The modified vegetable oil microemulsion is a modified rapeseed oil microemulsion, a modified coconut oil microemulsion, or a modified soybean oil microemulsion.

[0027] Bio-based antibacterial agents are tea tree oil extract, rosemary extract, or Bacillus extracellular polysaccharide.

[0028] The density of the multi-scenario adaptive gradient composite drilling fluid mud of this invention is 1.3~1.7 g / cm³. 3 .

[0029] As a preferred embodiment, when used in conventional formations such as clay layers, the present invention provides a multi-scenario adaptive gradient composite drilling mud, comprising 240 parts by weight of modified sepiolite, 140 parts by weight of sodium-modified red clay, 90 parts by weight of nanofiller-red clay composite, 70 parts by weight of a composite of polyaspartic acid and chitosan quaternary ammonium salt, 50 parts by weight of modified rapeseed oil microemulsion, 10 parts by weight of tea tree oil extract, and 390 parts by weight of deionized water.

[0030] As a preferred embodiment, when used in conventional formations such as hard rock, the present invention provides a multi-scenario adaptive gradient composite drilling mud, comprising 260 parts by weight of modified sepiolite, 130 parts by weight of sodium-modified red clay, 110 parts by weight of nanofiller-red clay composite, 50 parts by weight of a composite of polyaspartic acid and chitosan quaternary ammonium salt, 60 parts by weight of modified rapeseed oil microemulsion, 5 parts by weight of tea tree oil extract, and 385 parts by weight of deionized water.

[0031] As a preferred embodiment, when used in loose sand layers / burrow-prone formations, the present invention provides a multi-scenario adaptive gradient composite drilling mud, comprising 280 parts by weight of modified sepiolite, 180 parts by weight of sodium-modified red clay, 150 parts by weight of nanofiller-red clay composite, 80 parts by weight of a composite of polyaspartic acid and chitosan quaternary ammonium salt, 40 parts by weight of modified rapeseed oil microemulsion, 8 parts by weight of tea tree oil extract, and 342 parts by weight of deionized water.

[0032] As a preferred embodiment, when used in environments with high temperature / high salinity / environmental requirements, this invention provides a multi-scenario adaptive gradient composite drilling mud, comprising 220 parts by weight of modified sepiolite, 200 parts by weight of sodium-modified red clay, 130 parts by weight of nanofiller-red clay composite, 30 parts by weight of a composite of polyepoxysuccinic acid and chitosan quaternary ammonium salt, 50 parts by weight of modified coconut oil microemulsion, 5 parts by weight of rosemary extract, and 365 parts by weight of deionized water.

[0033] This invention provides a method for preparing multi-scenario adaptive gradient composite drilling mud, which includes the following steps: S1. Mix the modified sepiolite and sodium-modified red clay evenly to obtain the first dry material.

[0034] S2. Add nanofiller-red clay composite to the first dry material and mix and stir evenly to obtain the second dry material.

[0035] S3. Add a pH-responsive filtration reducer to the second dry material and stir until homogeneous to obtain the first wet material.

[0036] S4. Add environmentally friendly lubricant to the first wet material and stir evenly to obtain the second wet material.

[0037] S5. Add bio-based antibacterial agent and deionized water to the second wet material and stir evenly to prepare multi-scenario adaptive gradient composite drilling mud.

[0038] This invention relates to a multi-scenario adaptive gradient composite drilling mud system that constructs a novel composite material system through gradient composite and functionalized modification of sepiolite and red clay. Specifically, acrylic acid is grafted onto sepiolite using a silane coupling agent to improve its hydrophobic properties. Simultaneously, nano-sized calcium carbonate with a particle size of 20-50 nm is loaded onto the surface of red clay to enhance its plugging ability. The modified sepiolite and red clay exhibit both excellent shear resistance and adsorption properties. This synergistic effect of modification effectively achieves a comprehensive improvement in wellbore stability, filtration loss, and lubrication performance.

[0039] The multi-scenario adaptive gradient composite drilling fluid mud of this invention enhances wellbore protection, prevents wellbore collapse, ensures wellbore stability, and reduces the corrosion rate of seawater on the reinforcing cage and drill bit. Its cuttings-carrying capacity efficiently transports drilling cuttings to the surface, ensuring smooth drilling operations.

[0040] Meanwhile, the multi-scenario adaptive gradient composite drilling fluid mud plugging performance of the present invention can effectively seal formation fractures and pores, and prevent drilling fluid loss.

[0041] Furthermore, the multi-scenario adaptive gradient composite drilling fluid mud of the present invention has high biodegradability (degradation rate of over 90% within 28 days) and no heavy metal residues were detected.

[0042] The multi-scenario adaptive gradient composite drilling mud of this invention has a variety of typical applications in engineering practice. For example, in drilling engineering, it can effectively cool the drill string, slow down acid and alkali corrosion, extend the service life of the drill string, and at the same time provide lubrication and transport rock cuttings. In shield tunneling construction, it can effectively balance the formation pressure and maintain the stability of the surrounding rock of the tunnel.

[0043] The multi-scenario adaptive gradient composite drilling mud of this invention maintains an apparent viscosity (AV) ≥25 mPa·s at 200℃, and a high-temperature high-pressure filtration loss (HPHT-FL) ≤6 mL. The viscosity decay rate of the multi-scenario adaptive gradient composite drilling mud in 25% NaCl solution is <15%, which is superior to traditional bentonite (>40%). The multi-scenario adaptive gradient composite drilling mud of this invention achieves a ≥95% sealing rate for 0.3~0.8 mm fracture formations, extending the wellbore collapse cycle to 96 hours. The biodegradability rate (28 days) of the multi-scenario adaptive gradient composite drilling mud of this invention is >90%, with no heavy metal residue.

[0044] To further illustrate the application of the multi-scenario adaptive gradient composite drilling fluid mud of the present invention in multiple scenarios, the following embodiments are provided for detailed explanation. Example 1

[0045] Application of the multi-scenario adaptive gradient composite drilling fluid mud of the present invention in the construction of a shale gas well in a conventional formation (clay layer + hard rock layer). Stratigraphic characteristics: Clay layer: mainly kaolinite, with a water swelling rate >15%, which can easily lead to well wall collapse; Hard rock layer: mainly limestone, rock hardness >7 (Mohs), drill bit wear is severe.

[0046] Technical challenges: The clay layer has insufficient inhibitory properties, and the well diameter enlargement rate is >10%. The hard rock formation has poor lubricity, and the friction of the drill bit is >50 kN.

[0047] The formulation of multi-scenario adaptive gradient composite drilling fluid mud of the present invention (1m 3 The mud is shown in Tables 1 and 2 below: Table 1. Multi-scenario adaptive gradient composite drilling fluid mud formulation in clay layers

[0048] Table 2. Adaptive Gradient Composite Drilling Fluid Formulations for Multiple Scenarios in Hard Rock Formations

[0049] In clay layers, methods for modifying sepiolite include: Sepiol pickling (5% HCl, 2 hours) → KH-550 grafting (60℃, 4 hours) → Acrylic coating (molar ratio 1:2) → Spray drying (inlet air 180℃).

[0050] In hard rock formations, the sepiolite method includes: Sepiol pickling → KH-550 grafting → PEG-6000 coating (molar ratio 1:1) → spray drying (air inlet 190℃).

[0051] The method for sodiumizing red clay includes: crushing red clay (200 mesh) → soaking in 3% to 5% Na2CO3 solution (60℃, 2 hours) → calcining (100℃, 1 hour) → grinding to a particle size <75μm.

[0052] Gradient composition: In the clay layer, modified sepiolite + sodium red clay (24:14) → added nano calcium carbonate-red clay complex (ultrasonic dispersion 40 kHz, 20 min) → added PASP-CS-Q complex (800 rpm, 15 min) → added modified rapeseed oil microemulsion (ultrasonic emulsification) → finally added tea tree oil extract and deionized water (300 rpm, 10 min) → allowed to stand for aging (24 hours, 50℃).

[0053] In hard rock strata, modified sepiolite + sodium-modified red clay (26:13) → nano-calcium carbonate-red clay complex (ultrasonic dispersion 40kHz, 30 minutes) → PASP-CS-Q complex (1000rpm, 20 minutes) → modified rapeseed oil microemulsion (high-speed shearing 25 minutes) → tea tree oil extract and deionized water (400rpm, 15 minutes) → static aging (24 hours, 60℃). Process optimization: Add PASP-CS-Q complex (pH 8~10 responsive) to dynamically adjust filtration loss.

[0054] Application results (see Table 3 below): Wellbore stability: Wellbore enlargement rate in clay layers ≤ 4.5% (conventional mud > 10%); Lubrication performance: friction coefficient of hard rock formation ≤0.07 (0.12 for traditional oil-based mud); Drilling rate improvement: Mechanical drilling rate increased by 30% in hard rock sections (compared to adjacent wells).

[0055] Table 3. Comparison of Application Effects in Example 1 Example 2

[0056] Application of the multi-scenario adaptive gradient composite drilling fluid mud of the present invention in a sandstone oil well in the Tarim Basin—a loose sand / pothole-prone formation. Stratigraphic characteristics: Sand layer: mainly fine sandstone, poorly cemented (cementation index <30%), permeability >50 mD; Easily collapsed boreholes: 3000~3500 m deep, collapse cycle <24 hours.

[0057] Technical challenges: Sand migration caused wellbore instability; High-permeability formations pose a significant risk of leakage.

[0058] The formulation of multi-scenario adaptive gradient composite drilling fluid mud of the present invention (1m 3 (Mud) is shown in Table 4 below: Table 4. Mud Formation Formulas for Loose Sand Layers / Easily Collapsible Formations

[0059] In loose sandy / collapsed pore formations, the modification method of sepiolite includes: sepiolite acid washing (5% HCl, 2 hours) → screening fiber length ≥80μm → KH-550 grafting (60℃, 3 hours) → spray drying (air intake 200℃).

[0060] The sodiumization method of red clay includes: crushing red clay (200 mesh) → soaking in 8% Na2CO3 solution (100℃, 4 hours) → calcining (120℃, 3 hours) → grinding to a particle size <50μm.

[0061] Gradient composition: Modified sepiolite + sodium red clay (28:18) → Add nano calcium carbonate-red clay complex (ultrasonic dispersion 40kHz, 45 minutes) → Add PASP-CS-Q complex (1200rpm, 25 minutes) → Add modified rapeseed oil microemulsion (ultrasonic emulsification 30 minutes) → Finally add tea tree oil extract and deionized water (500rpm, 20 minutes) → Static aging (24 hours, 70℃).

[0062] Application results (see Table 5 below): Process enhancement: Add 0.5% nanocellulose (CNF) to improve the surface lubricity of sand particles.

[0063] Wellbore stability: Collapse cycle extended to 72 hours (compared to 24 hours for traditional mud). Permeability control: Sand layer permeability reduced by ≥95% (permeability <2.5 mD); Environmental friendliness: Biodegradability > 95% (compliant with SY / T 7351-2016).

[0064] Table 5. Comparison of Application Effects in Example 2 Example 3

[0065] Application of the multi-scenario adaptive gradient composite drilling fluid mud of this invention in high temperature / high salinity / environmentally demanding environments—specifically, a marine airport in a land reclamation project. Stratigraphic characteristics: Backfill layer: The backfill material is mainly blocks and crushed stone with sharp edges and corners, and a particle size of 20mm to 400mm. A small portion of the particle size is larger than 400mm. The structure is loose to slightly dense, and the backfill depth is more than 35 meters.

[0066] Environmental challenges: Seabed silt is highly mobile.

[0067] Technical challenges: Anti-settlement: Artificial islands need to resist long-term loads and tidal effects, with a settlement control standard of ≤30 mm (the international standard for similar airports is ≤50 mm).

[0068] Impact of moisture: Seawater is visible 2 meters below the site. Ordinary mud slurry is difficult to use for wall protection due to the influence of tides. Seawater also corrodes machinery and steel cages during construction.

[0069] Ecological protection: The construction area is a national-level marine ranch, and it is necessary to avoid damage to coral reefs and the habitat of Indo-Pacific humpback dolphins.

[0070] The formulation of multi-scenario adaptive gradient composite drilling fluid mud of the present invention (1m 3 (Mud) is shown in Table 6 below: Table 6. Formation Mud Formulas for High Temperature / High Salinity / Environmental Protection Requirements

[0071] In formations with high temperature / high salinity / environmental protection requirements, the sepiolite modification method includes: sepiolite acid washing (5% HCl, 2 hours) → KH-550 grafting (60℃, 3 hours) → PASP coating (molar ratio 1:2) → spray drying (air intake 170℃).

[0072] The method for sodiumizing red clay includes: crushing red clay (200 mesh) → soaking in 10% Na2CO3 solution (120℃, 5 hours) → calcining (150℃, 4 hours) → grinding to a particle size <40μm.

[0073] Gradient composition: Modified sepiolite + sodium red clay (22:20) → Add nano calcium carbonate-red clay complex (ultrasonic dispersion 40kHz, 50 minutes) → Add PESA-Q complex (1500rpm, 30 minutes) → Add modified coconut oil microemulsion (high-speed shearing 30 minutes) → Finally add rosemary extract and deionized water (600rpm, 25 minutes) → Static aging (24 hours, 80℃).

[0074] Application results (see Table 7 below): Salt resistance: Filtration loss ≤8 mL in 25% NaCl environment (conventional mud >20 mL); Wellbore stability: Wellbore enlargement rate of salt-gypsum layer ≤3% (conventional mud >15%); Equipment protection: Mud pump wear rate reduced by 60% (salt corrosion reduced).

[0075] Apparent viscosity in solution: 28 mPa·s (traditional bentonite is only 12 mPa·s).

[0076] Dynamic plugging rate (5 mm crack): 96% (permeability recovery value <3%).

[0077] Construction efficiency: 1,177 piles in the core area were completed 42 days ahead of schedule, improving efficiency by 30%.

[0078] Quality indicators: 100% of the 1550 engineering piles meet the Class I standard (bearing capacity ≥ 120% of design value), and the settlement is ≤ 15mm.

[0079] Environmental compliance: The water quality in the construction area meets Class II standards, and the coral reef survival rate is ≥95%.

[0080] Table 7. Comparison of Application Effects in Example 3

[0081] The multi-scenario adaptive gradient composite drilling mud of this invention undergoes bifunctional modification, including sepiolite grafted with acrylic acid via a silane coupling agent to enhance hydrophobicity, and red clay loaded with nano-calcium carbonate to enhance plugging performance. This multi-scenario adaptive gradient composite drilling mud also incorporates a polyaspartic acid-chitosan quaternary ammonium salt complex for pH-responsive adjustment of filtration loss.

[0082] The present invention utilizes a multi-scenario adaptive gradient composite drilling fluid mud additive modified vegetable oil microemulsion to form a biomimetic lubrication design, which, in conjunction with red clay, forms a lotus leaf-like hydrophobic film.

[0083] The present invention provides a multi-scenario adaptive gradient composite drilling fluid mud containing a bio-based filtration reducer and a vegetable oil microemulsion, which meets GB / T 16783-2020 and international environmental protection standards.

[0084] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A multi-scenario adaptive gradient composite drilling mud, characterized in that, By weight percentage, the multi-scenario adaptive gradient composite drilling mud includes 20-30% modified sepiolite, 12-25% sodium-modified red clay, 8-15% nanofiller-red clay composite, 4-8% pH-responsive filtration reducer, 3-6% environmentally friendly lubricant, 0.5-2% bio-based antibacterial agent, and the balance deionized water; The modified sepiolite is modified by grafting acrylic acid onto a silane coupling agent. The nanofiller-red clay composite is a composite of nano-calcium carbonate supported on the surface of red clay. The pH-responsive filtration reducer is a complex of polyaspartic acid and chitosan quaternary ammonium salt, or a complex of polyepoxysuccinic acid and chitosan quaternary ammonium salt. The environmentally friendly lubricant is a modified vegetable oil microemulsion; The density of the multi-scenario adaptive gradient composite drilling fluid mud is 1.3~1.7 g / cm³. 3 .

2. The multi-scenario adaptive gradient composite drilling fluid mud according to claim 1, characterized in that, The modified vegetable oil microemulsion is a modified rapeseed oil microemulsion, a modified coconut oil microemulsion, or a modified soybean oil microemulsion.

3. The multi-scenario adaptive gradient composite drilling fluid mud according to claim 2, characterized in that, The bio-based antibacterial agent is tea tree oil extract, rosemary extract, or Bacillus extracellular polysaccharide.

4. The multi-scenario adaptive gradient composite drilling fluid mud according to claim 3, characterized in that, It includes 240 parts by weight of modified sepiolite, 140 parts by weight of sodium red clay, 90 parts by weight of nanofiller-red clay complex, 70 parts by weight of polyaspartic acid and chitosan quaternary ammonium salt complex, 50 parts by weight of modified rapeseed oil microemulsion, 10 parts by weight of tea tree oil extract and 390 parts by weight of deionized water.

5. The multi-scenario adaptive gradient composite drilling fluid mud according to claim 3, characterized in that, It includes 260 parts by weight of modified sepiolite, 130 parts by weight of sodium red clay, 110 parts by weight of nanofiller-red clay complex, 50 parts by weight of polyaspartic acid and chitosan quaternary ammonium salt complex, 60 parts by weight of modified rapeseed oil microemulsion, 5 parts by weight of tea tree oil extract and 385 parts by weight of deionized water.

6. The multi-scenario adaptive gradient composite drilling fluid mud according to claim 3, characterized in that, It includes 280 parts by weight of modified sepiolite, 180 parts by weight of sodium red clay, 150 parts by weight of nanofiller-red clay composite, 80 parts by weight of polyaspartic acid and chitosan quaternary ammonium salt composite, 40 parts by weight of modified rapeseed oil microemulsion, 8 parts by weight of tea tree oil extract and 342 parts by weight of deionized water.

7. The multi-scenario adaptive gradient composite drilling fluid mud according to claim 3, characterized in that, It includes 220 parts by weight of modified sepiolite, 200 parts by weight of sodium red clay, 130 parts by weight of nanofiller-red clay complex, 30 parts by weight of polyepoxysuccinic acid and chitosan quaternary ammonium salt complex, 50 parts by weight of modified coconut oil microemulsion, 5 parts by weight of rosemary extract and 365 parts by weight of deionized water.

8. A method for preparing multi-scenario adaptive gradient composite drilling mud as described in any one of claims 1 to 7, characterized in that, Includes the following steps: The modified sepiolite and sodium-modified red clay were mixed and stirred evenly to obtain the first dry material; The first dry material is mixed with a nanofiller-red clay composite to obtain a second dry material. Add a pH-responsive filtration reducer to the second dry material and stir until homogeneous to obtain the first wet material; An environmentally friendly lubricant was added to the first wet material and stirred evenly to obtain a second wet material; A multi-scenario adaptive gradient composite drilling mud is prepared by adding a bio-based antibacterial agent and deionized water to the second wet material and stirring evenly.

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