A drilling fluid system based on heat conduction network and its preparation method

Abstract

The present invention provides a drilling fluid system constructed based on a heat-conducting network and a preparation method thereof, belonging to the field of oil and gas drilling engineering. The drilling fluid system constructed based on a heat-conducting network comprises the following raw materials by weight: 100 parts of a water-based drilling fluid base fluid, 1 to 5 parts of a nanomaterial, 0.5 to 3 parts of a dispersant, 1 to 10 parts of a metal fiber, 1 to 3 parts of a viscosity enhancer, and 1 to 4 parts of a fluid loss reducer; the nanomaterial is a mixture of graphene oxide, boron nitride, and carbon nanotubes; the dispersant is sodium lignin sulfonate, cocamidopropyl betaine, or sodium polyacrylate; and the metal fiber is copper fiber, aluminum fiber, or silver-plated copper fiber. The present invention constructs an efficient heat-conducting path by coordinating the nanomaterial with the metal fiber network, while optimizing dispersibility and rheology, significantly improving the thermal conductivity of the drilling fluid and the ground cooling efficiency.

Description

Technical Field

[0001] The present invention relates to a drilling fluid system constructed based on a heat conduction network and a preparation method thereof, and in particular to a high-thermal-conductivity drilling fluid system constructed based on a multi-scale heat conduction network and a preparation method thereof, belonging to the field of oil and gas drilling engineering. Background Art

[0002] During drilling in ultra-deep and ultra-deep formations, drilling fluids must carry cuttings, cool the drill bit, and maintain wellbore stability. However, conventional drilling fluids (such as oil-based or water-based systems) generally have low thermal conductivity (typically less than 0.5 W / (m·K)). This prevents timely transfer of bottomhole heat to the surface, leading to safety hazards such as drill bit overheating, fluid degradation, and even downhole tool failure. Furthermore, the surface cooling system's limited heat transfer efficiency prevents it from rapidly reducing the temperature of the return drilling fluid, further exacerbating the impact of high downhole temperatures on operations.

[0003] Specifically, low thermal conductivity makes it difficult for heat accumulated at the bottom of the well to be transferred to the ground cooling system in a timely manner, leading to the following chain problems: drill tools fail due to overheating, and the drill bit and downhole tools experience material softening and increased wear due to the sudden increase in local temperature (which can reach over 300°C); drilling fluid performance deteriorates, and high temperature accelerates the degradation of polymers in the drilling fluid (for example, the viscosity retention rate of xanthan gum at 180°C is less than 30%), and the increased filtration loss causes the risk of wellbore instability; the ground cooling efficiency reaches a bottleneck, and the temperature of the return drilling fluid is often higher than 80°C. The existing plate heat exchanger has a limited heat exchange area and a cooling rate of less than 5°C / min, which cannot meet the circulating cooling needs, further increasing the downhole heat load.

[0004] While some prior art studies have attempted to improve the thermal conductivity of drilling fluids by adding thermally conductive fillers (such as graphite and metal oxides), these methods suffer from the following issues: uneven dispersion, easy agglomeration of nanomaterials, resulting in a discontinuous thermal network and limited improvement in actual thermal conductivity; poor rheological properties, and a high filler ratio that increases drilling fluid viscosity and impacts pumping efficiency; and poor cost and compatibility with other drilling fluid components (such as viscosifiers and fluid loss additives). For example, Chinese patent document CN107573911A utilizes modified graphene oxide, but its lamellar structure easily breaks under shear and produces charge repulsion with anionic treatment agents, resulting in poor suspension stability. Chinese patent document CN109825263A enhances dispersibility by covalently coating CNTs with sodium polystyrene sulfonate. However, a high aspect ratio of the nanotubes (>1000) increases the plastic viscosity of the drilling fluid, limiting pumping efficiency.

[0005] Therefore, there is an urgent need to develop a drilling fluid system that combines high thermal conductivity, stable dispersibility, and good rheological properties. In addition, existing technologies often focus on optimizing a single thermal conductive material, ignoring the synergistic effect of the "filler-base fluid-additive" multiphase system. For example, the high-temperature shearing agent developed in Chinese patent document CN117903763A improves rheological properties through a hydrophobic association structure, but is not designed for the thermal conductivity path; Chinese patent document CN114736659A uses sulfonated monomers to improve high-temperature stability, but the sulfonic acid group has poor interfacial compatibility with metal fibers, which in turn exacerbates agglomeration.

[0006] In summary, the current drilling fluid system faces three contradictions in improving thermal conductivity: high thermal conductivity and low viscosity cannot achieve a good balance; the high specific surface area of ​​nanomaterials and the geometric characteristics of fibers easily lead to loss of control of rheological parameters; long-term dispersion and dynamic shear compatibility are poor, and downhole high-speed circulation (shear rate> 500s -1 ) requires the filler to have the ability to resist shear redispersion; the coordination between cost control and performance upgrade is poor, and the industrial application of precious metal fibers (such as silver) or functionalized nanomaterials is restricted by the cost of raw materials.

[0007] This technological gap severely restricts the development efficiency of deep oil and gas reservoirs and economical geothermal wells. Therefore, the development of a drilling fluid system with high thermal conductivity, stable rheology, and economic efficiency has become an urgent need in the oil and gas engineering field. Summary of the Invention

[0008] To address the shortcomings of existing drilling fluids, particularly their low thermal conductivity and insufficient cooling capacity under high-temperature conditions, the present invention provides a drilling fluid system based on a thermally conductive network and its preparation method. This system utilizes nanomaterials in conjunction with a metal fiber network to create a highly efficient thermally conductive path, while simultaneously optimizing dispersibility and rheological properties, significantly improving the thermal conductivity of the drilling fluid and its surface cooling efficiency.

[0009] The technical solutions of the present invention are as follows:

[0010] A drilling fluid system constructed based on a heat conduction network includes the following raw materials in parts by mass: 100 parts of water-based drilling fluid base fluid, 1-5 parts of nanomaterials, 0.5-3 parts of dispersants, 1-10 parts of metal fibers, 1-3 parts of tackifiers, and 1-4 parts of fluid loss reducers.

[0011] Preferably, according to the present invention, the water-based drilling fluid base liquid is a base liquid commonly used in the art; preferably, the water-based drilling fluid base liquid includes water, Na2CO3 and bentonite, and based on 1L of water, the added mass of Na2CO3 is 0.4g, and the added mass of bentonite is 35~40g; the water-based drilling fluid base liquid is prepared according to the following method: adding Na2CO3 to water, stirring evenly, adding bentonite under low-speed stirring conditions, and then stirring at high speed to obtain the water-based drilling fluid base liquid; the rotation speed of the low-speed stirring is 1500~2500rpm, the rotation speed of the high-speed stirring is 8000~12000rpm, and the time of high-speed stirring is 20~40min.

[0012] Preferably, according to the present invention, the nanomaterial is a mixture of graphene oxide (GO), boron nitride (BN) and carbon nanotubes (CNTs), and the mass ratio of graphene oxide (GO), boron nitride (BN) and carbon nanotubes (CNTs) in the mixture is 1:1:1; the thickness of the graphene oxide (GO) is 0.5~2nm, and the lateral size is 1~10μm; the thickness of the boron nitride (BN) is 1~3nm, and the lateral size is 0.5~2μm; the carbon nanotubes (CNTs) are multi-walled carbon nanotubes MWCNTs with a diameter of 10~20nm and a length of 10~30μm.

[0013] According to the present invention, the dispersant is preferably sodium lignin sulfonate, cocamidopropyl betaine or sodium polyacrylate, more preferably sodium lignin sulfonate; preferably, the weight average molecular weight of the sodium lignin sulfonate is 2000~12000, preferably 4000~10000; the number average molecular weight of the sodium polyacrylate is 1000~5000.

[0014] According to the present invention, the metal fiber is preferably copper fiber, aluminum fiber or silver-plated copper fiber, further preferably silver-plated copper fiber; the diameter of the metal fiber is 5~15μm, the length is 0.5~2mm, and the aspect ratio is ≥50; the copper base diameter of the silver-plated copper fiber is 4~13μm, and the thickness of the silver plating layer is 0.5~1μm.

[0015] According to the present invention, preferably, the mass ratio of the nanomaterial to the metal fiber is 1:1-2, more preferably 1:1.5.

[0016] According to the present invention, the viscosity enhancer is preferably xanthan gum or sulfonated polyacrylamide, more preferably sulfonated polyacrylamide; the sulfonated polyacrylamide is a copolymer of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and acrylamide (AM), which is prepared according to the following method: 2-acrylamido-2-methylpropanesulfonic acid (AMPS) is added to distilled water, stirred evenly, and then acrylamide (AM) is added to obtain a monomer solution, wherein the molar ratio of acrylamide to 2-acrylamido-2-methylpropanesulfonic acid in the monomer solution is 7:3, and the total mass of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid in the monomer solution is 1:1. The method comprises the following steps: adjusting the pH of the monomer solution to 7 using a 20-30% by mass NaOH solution, deoxygenating the solution with nitrogen for 10-30 minutes, adding a redox initiator, and reacting the solution at a constant temperature of 35-45° C. for 5-7 hours; washing the reaction product with ethanol, drying the product at 80-90° C. to a constant weight, and crushing the product to obtain sulfonated polyacrylamide; the mass of the redox initiator is 0.1-0.5% of the total mass of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid; the oxidant in the redox initiator is ammonium persulfate, the reducing agent is sodium bisulfite, and the mass ratio of the oxidant to the reducing agent is 1:1.

[0017] According to the present invention, preferably, the fluid loss reducer is carboxymethyl cellulose or sulfonated phenolic resin, more preferably sulfonated phenolic resin.

[0018] According to the present invention, the method for preparing the drilling fluid system based on the thermal conductive network comprises the following steps:

[0019] (1) Adding a dispersant to a water-based drilling fluid base fluid and shearing the fluid to obtain a dispersion;

[0020] (2) adding nanomaterials to the dispersion obtained in step (1), and shearing to obtain a suspension;

[0021] (3) Adding metal fiber to the suspension obtained in step (2), stirring evenly, then sequentially adding a viscosity enhancer and a fluid loss reducer, stirring evenly, to obtain a drilling fluid system constructed based on a thermal conductive network.

[0022] Preferably, according to the present invention, the shearing rate in step (1) is 8000-12000 rpm, and the shearing time is 10-30 minutes.

[0023] Preferably, according to the present invention, the nanomaterials in step (2) are equally divided into 2 to 4 batches and added to the dispersion, and each batch of nanomaterials is sheared at a shear rate of 8000 to 12000 rpm for a shear time of 5 to 15 minutes.

[0024] Preferably, according to the present invention, the stirring speed after adding the metal fiber in step (3) is 5000~8000 rpm, and the stirring time is 20~40 minutes; the stirring speed after adding the viscosity enhancer and the filtration loss reducer is 5000~8000 rpm, and the stirring time is 20~40 minutes.

[0025] The technical features and beneficial effects of the present invention are as follows:

[0026] 1. Multi-scale Nanomaterial Enhanced Thermal Conductivity: This invention utilizes multi-dimensional nanomaterials, including graphene oxide (GO), boron nitride (BN), and carbon nanotubes (CNTs), to create a complementary thermal conductivity enhancement mechanism. GO, with its two-dimensional layered structure and oxygen-containing functional groups (-COOH, -OH), tightly bonds to the metal fiber surface through π-π stacking and hydrogen bonding, significantly reducing interfacial thermal resistance. Boron nitride (BN) inhibits polymer degradation at high temperatures (>150°C) through its hydrophobic layered structure. It also optimizes interfacial compatibility through a synergistic hydrophilic-hydrophobic interaction with GO, and achieves fluid loss control through the charge-regulating effect of the dispersant. Carbon nanotubes (CNTs), with their high aspect ratio (>1000) one-dimensional tubular structure, act as a "thermal bridge," connecting the nanosheets and metal fibers in series to form a penetrating thermal path. This synergistic effect of these materials increases the thermal conductivity of the drilling fluid to 1.9-2.6 W / (m·K), significantly exceeding that of conventional systems.

[0027] 2. Construction of a long-range thermal conductivity network using metal fibers and interface strengthening: A continuous "linear" thermal conductivity network is constructed using high aspect ratio (≥50) metal fibers (such as silver-plated copper fibers and aluminum fibers). The metal fiber diameter (5-15μm) precisely matches the size of the nanomaterial, increasing the heat conduction area through "point-line" contact. This design increases the cooling rate to 20.9-26.5°C / min and controls the apparent viscosity to ≤53mPa·s.

[0028] 3. Synergistic optimization of dispersants and stabilization of multiphase systems: Dispersions based on sodium lignin sulfonate, cocamidopropyl betaine or sodium polyacrylate can achieve uniform dispersion of nanomaterials and stable suspension of metal fibers. Sodium lignin sulfonate has a temperature resistance of >200°C and can enhance the dispersibility of nanomaterials through sulfonic acid groups and hydroxyl groups, and form hydrogen bonds with the surface of metal fibers to inhibit sedimentation; cocamidopropyl betaine can adapt to high-salt environments due to its zwitterionic properties and can reduce the repulsive effect between nanomaterials and anionic additives through charge balance; sodium polyacrylate can stabilize nanosuspensions through electrostatic repulsion and steric hindrance, and dynamic shear (>500s -1 ) improves dispersion stability under high temperatures. The synergistic effect of adding specific dispersants reduces the nanomaterial agglomeration rate to less than 3%, the suspension sedimentation rate to less than 3% after 24 hours of standing, the dispersion stability retention rate to more than 90% at high temperatures (150°C), and the filtration loss to 25%.

[0029] 4. Multiphase synergy achieves comprehensive performance optimization: A multiphase synergistic design combining nanomaterials, metal fibers, and dispersants achieves a balance between high thermal conductivity, low viscosity, and dynamic shear adaptability. The nanomaterial / fiber mass ratio optimizes the balance between thermal path density and rheological properties, avoiding viscosity surges. A phased gradient shear process (8,000-12,000 rpm) ensures uniform dispersion of the nanomaterial while largely preserving the structural integrity of the metal fibers. This system exhibits stable performance at temperatures of 150°C and pressures of 50 MPa, reducing industrial costs by approximately 25%. It can be applied on a large scale to water-based, oil-based, and hybrid systems.

[0030] 5. Comprehensively Improve the Safety and Efficiency of Deep-Well Operations: This invention significantly reduces downhole risks and improves operational efficiency through the synergy of efficient thermal conductivity and stable rheological properties. The multi-scale thermal network significantly increases the heat transfer rate from the bottom of the well to the surface; the surface cooling system's heat exchange efficiency is greatly improved, significantly shortening the cycle cooling time; and the system is suitable for ultra-deep wells exceeding 4,500 meters, geothermal wells, and high-salinity oil and gas reservoirs. Furthermore, the environmentally friendly and economical dispersant (for example, the cost of sodium lignin sulfonate is 30% lower than that of SDBS) further reduces the difficulty of drilling fluid waste disposal, meeting green drilling requirements and providing an efficient, economical, and environmentally friendly solution for deep oil and gas resource development.

[0031] 6. The present invention solves the core problems of low thermal conductivity and poor high-temperature dispersion stability of traditional drilling fluids through the three-in-one design of "multi-scale nanomaterial synergistic thermal conductivity - metal fiber network penetration - dispersant interface stability", providing an efficient, economical and industrializable thermal management solution for deep oil and gas resource development. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a physical photo of the drilling fluid system constructed based on the heat conductive network obtained in Example 1. DETAILED DESCRIPTION

[0033] The technical solutions of the present invention are described clearly and completely below with reference to specific embodiments. Obviously, the embodiments described are only a portion of the embodiments of the present invention, and not all of them. The raw materials used in the examples are conventional and commercially available; the methods described are based on prior art unless otherwise specified. All other examples improved or modified by persons of ordinary skill in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0034] The graphene oxide (GO) sheets used in the examples have a thickness of 0.8-1.2 nm and a lateral size of 1-5 μm;

[0035] The boron nitride (BN) used is hexagonal h-BN with a thickness of 1~3nm, a lateral size of 0.5~2μm, and a specific surface area of ​​18~25m 2 / g;

[0036] The carbon nanotubes used are multi-walled carbon nanotubes (MWCNTs) with a diameter of 10-20 nm and a length of 10-30 μm.

[0037] The weight average molecular weight of the sodium lignin sulfonate used is 5000~10000;

[0038] The number average molecular weight of the sodium polyacrylate used is 2000~5000;

[0039] The aluminum fibers used have a diameter of 8-12 μm, a length of 1-1.5 mm, and an aspect ratio of 50-100;

[0040] The copper base of the silver-plated copper fiber used is 10 μm in diameter, the silver coating thickness is 0.5-1 μm, and the length is 0.8-1.2 mm.

[0041] The sulfonated polyacrylamide used was prepared according to the following method:

[0042] 2-Acrylamido-2-methylpropanesulfonic acid (AMPS) was added to distilled water and stirred uniformly, followed by the addition of acrylamide (AM) and stirring uniformly to obtain a monomer solution. The molar ratio of AM to AMPS in the monomer solution was 7:3, and the total mass fraction of AM and AMPS in the monomer solution was 10%. The pH of the monomer solution was adjusted to 7 using a 30% mass fraction NaOH solution. After deoxygenation by nitrogen bubbling for 20 minutes, a redox initiator (ammonium persulfate to sodium bisulfite in a mass ratio of 1:1, with the mass of the redox initiator being 0.3% of the total mass of AM and AMPS) was added. The mixture was reacted at 40°C for 6 hours until the viscosity of the solution increased significantly to form a gel-like product. The obtained gel-like product was washed with anhydrous ethanol, dried at 85°C to constant weight, and pulverized into a powdery product to obtain sulfonated polyacrylamide.

[0043] The sulfonated phenolic resin used is sulfonated phenolic resin SMP-II, a common commercial product.

[0044] Example 1

[0045] A drilling fluid system based on a heat conduction network comprises the following raw materials in parts by weight: 100 parts of a water-based drilling fluid base fluid, 3 parts of a nanomaterial, 1.2 parts of a dispersant, 4.5 parts of metal fibers, 1 part of a tackifier, and 1 part of a fluid loss reducer;

[0046] The water-based drilling fluid base liquid was prepared according to the following method: first, distilled water was measured and poured into a high-speed stirring container, and then sodium carbonate was added and stirred evenly; under low-speed stirring (2000 rpm), bentonite was slowly added to avoid agglomeration; after the addition, the speed was increased to 10000 rpm and high-speed stirring was carried out for 30 minutes to fully hydrate the bentonite to form a colloid, thereby obtaining the water-based drilling fluid base liquid; based on 1L of water, the mass of the added Na2CO3 was 0.4g and the mass of the bentonite was 40g;

[0047] The nanomaterial is obtained by mixing graphene oxide (GO), boron nitride (BN), and carbon nanotubes (CNTs) in a mass ratio of 1:1:1; the dispersant is sodium lignin sulfonate; the metal fiber is silver-plated copper fiber; the viscosity enhancer is sulfonated polyacrylamide; and the fluid loss reducer is sulfonated phenolic resin.

[0048] The method for preparing the drilling fluid system based on the thermal conductive network comprises the following steps:

[0049] (1) Adding a dispersant to the water-based drilling fluid base fluid, shearing at a speed of 10,000 rpm for 20 minutes to obtain a dispersion;

[0050] (2) adding the nanomaterials into the dispersion obtained in step (1) in three equal batches, and shearing at 10,000 rpm for 10 minutes after each batch is added to obtain a suspension;

[0051] (3) Add metal fiber to the suspension obtained in step (2) and stir at 8000 rpm for 30 minutes; then add viscosity enhancer and filtration reducer in sequence and stir at 8000 rpm for 30 minutes until the viscosity stabilizes, thereby obtaining a drilling fluid system constructed based on a thermal conductive network.

[0052] The actual photo of the drilling fluid system constructed based on the heat conduction network obtained in this embodiment is as follows Figure 1 shown.

[0053] Example 2

[0054] A drilling fluid system based on a heat-conducting network is as described in Example 1, except that the metal fiber is 3 parts, and the other conditions are the same as in Example 1.

[0055] The preparation method of the above-mentioned drilling fluid system constructed based on the thermal conductive network is as described in Example 1.

[0056] Example 3

[0057] A drilling fluid system based on a heat-conducting network is as described in Example 1, except that the metal fiber is 6 parts, and the other conditions are the same as in Example 1.

[0058] The preparation method of the above-mentioned drilling fluid system constructed based on the thermal conductive network is as described in Example 1.

[0059] Example 4

[0060] A drilling fluid system constructed based on a heat conductive network is as described in Example 1, except that the metal fiber is aluminum fiber, and the other conditions are the same as in Example 1.

[0061] The preparation method of the above-mentioned drilling fluid system constructed based on the thermal conductive network is as described in Example 1.

[0062] Example 5

[0063] A drilling fluid system constructed based on a heat conductive network is as described in Example 1, except that the dispersant is 2 parts, and the other conditions are the same as in Example 1.

[0064] The preparation method of the above-mentioned drilling fluid system constructed based on the thermal conductive network is as described in Example 1.

[0065] Example 6

[0066] A drilling fluid system constructed based on a heat conductive network is as described in Example 1, except that the viscosity enhancer is 2 parts, the fluid loss reducer is 2 parts, and the other conditions are the same as in Example 1.

[0067] The preparation method of the above-mentioned drilling fluid system constructed based on the thermal conductive network is as described in Example 1.

[0068] Example 7

[0069] A drilling fluid system constructed based on a heat conductive network is as described in Example 1, except that 3 parts of a dispersant are added, and the other conditions are the same as in Example 1.

[0070] The preparation method of the above-mentioned drilling fluid system constructed based on the thermal conductive network is as described in Example 1.

[0071] Example 8

[0072] A drilling fluid system constructed based on a heat conductive network includes the following raw materials in parts by mass: 100 parts of a water-based drilling fluid base fluid, 1 part of a nanomaterial, 0.5 parts of a dispersant, 1 part of a metal fiber, 1 part of a tackifier, and 1 part of a fluid loss reducer; other conditions are the same as those in Example 1.

[0073] The preparation method of the above-mentioned drilling fluid system constructed based on the thermal conductive network is as described in Example 1.

[0074] Example 9

[0075] A drilling fluid system constructed based on a heat conductive network includes the following raw materials in parts by mass: 100 parts of a water-based drilling fluid base fluid, 5 parts of a nanomaterial, 3 parts of a dispersant, 10 parts of metal fibers, 3 parts of a tackifier, and 4 parts of a fluid loss reducer; other conditions are the same as in Example 1.

[0076] The preparation method of the above-mentioned drilling fluid system constructed based on the thermal conductive network is as described in Example 1.

[0077] Comparative Example 1

[0078] A drilling fluid system is as described in Example 1, except that no metal fiber is added. Other conditions are the same as in Example 1.

[0079] The preparation method of the drilling fluid system is the same as that of Example 1, except that the step of adding metal fibers is omitted.

[0080] Comparative Example 2

[0081] A drilling fluid system is as described in Example 1, except that no dispersant is added, and other conditions are the same as in Example 1.

[0082] The preparation method of the drilling fluid system is the same as that of Example 1, except that the step of adding the dispersant is omitted.

[0083] Comparative Example 3

[0084] A drilling fluid system is as described in Example 1, except that no nanomaterial is added, and other conditions are the same as in Example 1.

[0085] The preparation method of the drilling fluid system is the same as that of Example 1, except that the step of adding nanomaterials is omitted.

[0086] Comparative Example 4

[0087] A drilling fluid system is as described in Example 1, except that the nanomaterial is only graphene oxide (GO), and the other conditions are the same as in Example 1.

[0088] The preparation method of the above drilling fluid system is as described in Example 1.

[0089] Comparative Example 5

[0090] A drilling fluid system is as described in Example 1, except that the nanomaterial is only boron nitride (BN), and the other conditions are the same as in Example 1.

[0091] The preparation method of the above drilling fluid system is as described in Example 1.

[0092] Comparative Example 6

[0093] A drilling fluid system is as described in Example 1, except that the nanomaterial is only carbon nanotubes (CNTs), and the other conditions are the same as in Example 1.

[0094] The preparation method of the above drilling fluid system is as described in Example 1.

[0095] Comparative Example 7

[0096] A drilling fluid system is as described in Example 1, except that the nanomaterial is a mixture of boron nitride (BN) and carbon nanotubes (CNTs) mixed in a mass ratio of 1:1, and other conditions are the same as in Example 1.

[0097] The preparation method of the above drilling fluid system is as described in Example 1.

[0098] Comparative Example 8

[0099] A drilling fluid system is as described in Example 1, except that the nanomaterial is a mixture of graphene oxide (GO) and boron nitride (BN) mixed in a mass ratio of 1:1, and the other conditions are the same as in Example 1.

[0100] The preparation method of the above drilling fluid system is as described in Example 1.

[0101] Comparative Example 9

[0102] A drilling fluid system is as described in Example 1, except that 6 parts of nanomaterials are added, and the other conditions are the same as in Example 1.

[0103] The preparation method of the above drilling fluid system is as described in Example 1.

[0104] Test Example 1

[0105] The performance of the drilling fluid system obtained in the embodiment and the comparative example was evaluated. The thermal conductivity of the drilling fluid system was measured at room temperature (25°C) using a thermal conductivity meter; the reading of the drilling fluid system at 600 rpm was measured using a six-speed rotary viscometer at room temperature (25°C). According to the formula AV=θ 600 / 2, the apparent viscosity of the drilling fluid system was calculated; 10 mL of the drilling fluid system sample was taken and centrifuged at 4000 rpm for 15 minutes, and the supernatant was collected. The agglomeration rate was calculated according to the formula: agglomeration rate = (initial sample mass - supernatant mass) / initial sample mass × 100%; the sample was heated to 80°C, a thermocouple (K type) was inserted into the center of the sample, cooling was started, and temperature data was collected in real time. The slope of the temperature drop from 80°C to 25°C was used to obtain the cooling rate of the drilling fluid system. The test results are shown in Table 1.

[0106] Table 1 Thermal conductivity, apparent viscosity, agglomeration rate and cooling rate of drilling fluid

[0107]

[0108] The experimental data in Table 1 show that under high-temperature conditions, Example 1 exhibits excellent thermal conductivity (2.6 W / (m·K)) and cooling efficiency (26.5°C / min), over six times higher than that of Comparative Example 3. This performance is attributed to the construction of a multi-scale thermal conductivity network and synergistic interface optimization. First, the nanomaterial dispersion process was optimized. A staged shearing technique (8000-12000 rpm gradient shearing) was employed to control the graphene oxide (GO) aggregation rate to 2.3%. The GO lamellar structure physically anchored the metal fiber surface through π-π interactions, creating a "point-line" thermal conductivity path and significantly improving thermal conductivity. Second, the metal fiber surface was modified to enhance interfacial bonding. Pre-treating the silver-coated copper fibers through physical polishing strengthened the bonding between the fibers and the nanomaterial. The introduction of boron nitride (BN) inhibited polymer degradation at high temperatures through its layered structure. Furthermore, the hydrophobicity of BN complemented the hydrophilicity of GO, suppressing fluid loss in saltwater through a charge-shielding effect.

[0109] In Comparative Example 1, no metal fibers were added. The system only contained nanomaterials. Due to the lack of a continuous heat conduction path, the thermal conductivity was only 1.2 W / (m·K) and the cooling rate was less than 5.2°C / min. In addition, the lack of metal fibers exacerbated the high-temperature agglomeration of GO, and the thermal conductivity performance declined sharply. In Comparative Example 2, no dispersant was added, resulting in spontaneous agglomeration of GO nanosheets due to surface energy, insufficient interface bonding with the metal fibers, separation of the agglomerates from the fibers under dynamic shear, and poor stability of the thermal conduction network. In Comparative Example 3, no nanomaterials were introduced, and only the linear path of the metal fibers was relied upon. The thermal conduction network density was insufficient, the thermal conductivity of the water-based drilling fluid itself was low, and the metal fibers alone could not significantly improve the performance.

[0110] Test Example 2

[0111] The sedimentation rate, dispersion stability retention rate, rheological properties and filtration loss of the drilling fluid system of Example 1 were measured.

[0112] (1) Sedimentation rate

[0113] The drilling fluid system was poured into a graduated cylinder. After standing for 24 hours, the supernatant was poured out. After drying, the mass of the remaining sediment was weighed using an electronic balance. Sedimentation rate (%) = (mass of sediment / total mass of suspension) × 100%. The sedimentation rate of the suspension after standing for 24 hours was calculated to be 2.26%.

[0114] (2) Dispersion stability retention rate

[0115] Two identical samples were taken, one as the initial sample T0, and the other aged at 150°C for 16 hours as sample T1. The nanoagglomeration rates of T0 and T1 were measured respectively. The dispersion stability retention rate = (T1 agglomeration rate / T0 agglomeration rate) × 100%. The calculation shows that the dispersion stability retention rate at high temperature (150°C) is 91.3%.

[0116] (3) Rheological properties and filtration loss

[0117] At room temperature (25°C), a six-speed rotary viscometer was used to measure the drilling fluid system at 300 rpm and 600 rpm. According to the formula AV=θ 600 / 2, PV=θ 600 -θ 300 and YP=θ 300 The apparent viscosity, plastic viscosity, and dynamic shear force of the drilling fluid system were calculated using the PV-PV method. The drilling fluid system was placed in a high-temperature, high-pressure fluid loss tester and pressurized at 150°C for 30 minutes. The filtrate volume was 13.2 mL. The fluid loss reduction rate was calculated as [(fluid loss of the drilling fluid system in Comparative Example 3 - fluid loss of the present invention) / fluid loss of the drilling fluid system in Comparative Example 3] × 100%. This calculated fluid loss reduction was 25% compared to the 17.6 mL in Comparative Example 3. This fluid loss control capability, verified in accordance with the API 13B-1 standard, can be directly applied in field operations, meeting wellbore stability requirements and reducing the risk of leakage. The test results are shown in Table 2.

[0118] Table 2 Apparent viscosity, plastic viscosity, dynamic shear force and filtration loss of drilling fluid

[0119]

[0120] In summary, the present invention provides a solution to the problem of high-temperature thermal management of drilling fluids through the design of a nano-metal collaborative thermal conductive network and an interface chemical modification process. The drilling fluid involved in the present invention can be used in high-temperature, high-pressure, and ultra-deep well drilling processes, providing a solution that combines thermal conductivity, stability, and environmental protection for the efficient development of deep oil and gas resources.

[0121] The above is only a specific embodiment of the present invention, but the design concept of the present invention is not limited to this. Any non-substantial modification of the present invention using this concept shall be deemed an infringement of the scope of protection of the present invention. However, any simple modification, equivalent change, and modification of the above embodiment made in accordance with the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A drilling fluid system based on a heat conduction network, characterized in that: The invention comprises the following raw materials by weight: 100 parts of water-based drilling fluid base fluid, 1-5 parts of nanomaterials, 0.5-3 parts of dispersant, 1-10 parts of metal fiber, 1-3 parts of viscosity enhancer, and 1-4 parts of fluid loss reducer; The water-based drilling fluid base fluid includes water, Na2CO3 and bentonite. Based on 1L of water, the added mass of Na2CO3 is 0.4g, and the added mass of bentonite is 35-40g; The nanomaterial is a mixture of graphene oxide, boron nitride and carbon nanotubes, and the mass ratio of graphene oxide, boron nitride and carbon nanotubes in the mixture is 1:1:1; the dispersant is sodium lignin sulfonate, cocamidopropyl betaine or sodium polyacrylate; the metal fiber is copper fiber, aluminum fiber or silver-plated copper fiber; the mass ratio of the nanomaterial to the metal fiber is 1:1-2; the viscosity enhancer is xanthan gum or sulfonated polyacrylamide; and the fluid loss reducer is carboxymethyl cellulose or sulfonated phenolic resin; The method for preparing the drilling fluid system based on the heat conduction network comprises the following steps: (1) Add the dispersant to the water-based drilling fluid base fluid and obtain a uniform dispersion by shearing; (2) adding nanomaterials to the dispersion obtained in step (1) and shearing to obtain a suspension; the nanomaterials are divided into 2 to 4 batches and added to the dispersion, and each batch of nanomaterials is sheared at a shear rate of 8000 to 12000 rpm for 5 to 15 minutes; (3) Adding metal fiber to the suspension obtained in step (2), stirring evenly, and then sequentially adding a thickener and a fluid loss reducer, stirring evenly, to obtain a drilling fluid system constructed based on a thermal conductive network; after adding the metal fiber, the stirring speed is 5000-8000 rpm, and the stirring time is 20-40 minutes; after adding the thickener and the fluid loss reducer, the stirring speed is 5000-8000 rpm, and the stirring time is 20-40 minutes.

2. The drilling fluid system based on the heat conduction network according to claim 1, characterized in that: The water-based drilling fluid base liquid is prepared according to the following method: Na2CO3 is added to water, stirred evenly, bentonite is added under low-speed stirring conditions, and then high-speed stirring is performed to obtain the water-based drilling fluid base liquid; the low-speed stirring speed is 1500~2500rpm, the high-speed stirring speed is 8000~12000rpm, and the high-speed stirring time is 20~40min.

3. The drilling fluid system based on the heat conduction network according to claim 1, characterized in that: The graphene oxide has a sheet thickness of 0.5-2 nm and a lateral size of 1-10 μm; the boron nitride has a thickness of 1-3 nm and a lateral size of 0.5-2 μm; and the carbon nanotubes are multi-walled carbon nanotubes (MWCNTs) with a diameter of 10-20 nm and a length of 10-30 μm.

4. The drilling fluid system based on the heat conduction network according to claim 1, characterized in that: The weight average molecular weight of the sodium lignin sulfonate is 2000-12000; the number average molecular weight of the sodium polyacrylate is 1000-5000; the diameter of the metal fiber is 5-15 μm, the length is 0.5-2 mm, and the aspect ratio is ≥50; the copper base diameter of the silver-plated copper fiber is 4-13 μm, and the thickness of the silver plating layer is 0.5-1 μm.

5. The drilling fluid system based on the heat conduction network according to claim 1, characterized in that: The mass ratio of the nano material to the metal fiber is 1:1.

5.

6. The drilling fluid system based on the heat conduction network according to claim 1, characterized in that: The sulfonated polyacrylamide is a copolymer of 2-acrylamido-2-methylpropanesulfonic acid and acrylamide, and is prepared according to the following method: 2-acrylamido-2-methylpropanesulfonic acid is added to distilled water, stirred evenly, and then acrylamide is added to obtain a monomer solution, wherein the molar ratio of acrylamide to 2-acrylamido-2-methylpropanesulfonic acid in the monomer solution is 7:3, and the total mass fraction of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid in the monomer solution is 5-15%; a NaOH solution with a mass fraction of 20-30% is used to adjust the The pH value of the monomer solution is 7. After nitrogen is passed through the solution for deoxygenation for 10 to 30 minutes, a redox initiator is added, and the reaction is carried out at a constant temperature of 35 to 45° C. for 5 to 7 hours. The reaction product is washed with ethanol, dried to a constant weight at 80 to 90° C., and crushed to obtain sulfonated polyacrylamide. The mass of the redox initiator is 0.1 to 0.5% of the total mass of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid. The oxidant in the redox initiator is ammonium persulfate, the reducing agent is sodium bisulfite, and the mass ratio of the oxidant to the reducing agent is 1:

1.

7. The drilling fluid system based on the heat conduction network according to claim 1, characterized in that: The shearing rate in step (1) is 8000-12000 rpm, and the shearing time is 10-30 minutes.

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