High-temperature-resistant non-sulfonated composite filtrate reducer for drilling fluid and preparation method of non-sulfonated composite filtrate reducer

Abstract

The invention provides a high-temperature-resistant non-sulfonated composite filtrate reducer for drilling fluid and a preparation method of the non-sulfonated composite filtrate reducer, and particularly relates to the field of C08F. The non-sulfonated composite filtrate reducer comprises a modified natural polymer and a synthetic non-sulfonated polymer, the modified natural polymer is etherified-crosslinked double modified konjac glucomannan; the synthetic non-sulfonated polymer is an acrylic acid-itaconic acid-acrylamide terpolymer. A traditional sulfonation treatment agent is abandoned, a full-non-sulfonation system is constructed by adopting environment-friendly components such as a modified natural polymer, a synthetic non-sulfonation polymer and a bio-based modified material, and the biodegradation rate of the system is larger than or equal to 90%, EC50gt; the drilling fluid has no biotoxicity, and completely meets the drilling environmental protection standard. The drilling fluid waste does not need to be treated complexly and can be discharged after reaching the standard only through simple solid-liquid separation, compared with traditional polysulfonate drilling fluid waste treatment, the cost is reduced by 40% or above, and the method is suitable for construction in severe environment-friendly areas.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field technology, specifically to a high-temperature resistant non-sulfonated composite filtration reducer for drilling fluids and its preparation method. Background Technology

[0002] As oil and gas exploration and development extend to deeper and ultra-deep formations, drilling depths are increasing year by year, and bottom-hole temperatures are generally rising to over 180°C, with some deep wells reaching 200°C. At the same time, the wells face multiple challenges such as the development of formation microfractures, shale hydration and expansion, and increasingly stringent environmental regulations, which place stringent requirements on the comprehensive performance of drilling fluids.

[0003] Currently, polysulfonated drilling fluids are widely used in high-temperature deep well drilling. They achieve high-temperature resistance and stability through sulfonation treatment agents such as sulfonated lignite and sulfonated phenolic resin. However, these sulfonation treatment agents have significant drawbacks: First, they are highly biotoxic, with EC50 generally below 10,000 mg / L and a biodegradation rate of less than 40%, which can easily cause formation pore blockage and water pollution, failing to meet the requirements of SYT7467-2020 "Technical Specification for Environmental Performance Evaluation of Drilling Fluids"; Second, waste disposal is difficult, requiring complex processes such as high-temperature incineration and chemical oxidation, with treatment costs accounting for more than 30% of the total cost of drilling fluids, thus limiting their application scenarios.

[0004] To address the environmental challenges and application limitations of sulfonated fluid loss reducers, non-sulfonated fluid loss reducers have become a research hotspot, driving technological advancements in non-sulfonated water-based drilling fluids. However, existing non-sulfonated fluid loss reducers and related composite systems still face numerous bottlenecks, failing to meet the demands of high-temperature deep well drilling: Firstly, their high-temperature resistance is insufficient. Most single non-sulfonated fluid loss reducers rely on modified natural polymers or synthetic polymers, which are prone to molecular chain breakage and cross-linking structure disintegration at 200℃, leading to a sharp decline in fluid loss reduction performance and an inability to effectively control drilling fluid filtration loss; Secondly... Poor functional synergy: Most existing non-sulfonated filtration reducers are single-function and have poor compatibility when compounded with other treatment agents in drilling fluids. It is difficult to achieve synergistic optimization of high temperature resistance, filtration reduction, plugging, and inhibition of shale hydration at the same time. A single filtration reducer often cannot meet the needs of multiple operating conditions. Third, the preparation process is complicated. The preparation process of some high-performance non-sulfonated filtration reducers is cumbersome and the reaction conditions are harsh, resulting in high production costs. It is difficult to achieve large-scale on-site production and application. Moreover, most existing non-sulfonated systems have not completely solved the core requirements of environmental compliance and low-cost treatment.

[0005] Therefore, there is an urgent need to develop a non-sulfonated composite filtration reducer for drilling fluids that is based on a compound of non-sulfonated components, can withstand high temperatures of over 200°C, has excellent filtration loss reduction performance, meets environmental standards, has synergistic functions, and is easy to prepare. Summary of the Invention

[0006] This invention addresses the problems of insufficient high-temperature resistance, failure to meet environmental standards, poor functional synergy, and complex preparation processes of existing sulfonated filtration loss reducers by providing a high-temperature resistant non-sulfonated composite filtration loss reducer for drilling fluids and its preparation method.

[0007] The technical method of the present invention is as follows: A high-temperature resistant non-sulfonated composite filtration reducer for drilling fluids, comprising a modified natural polymer and a synthetic non-sulfonated polymer; the modified natural polymer is an etherified-crosslinked double-modified konjac glucomannan; and the synthetic non-sulfonated polymer is an acrylic acid-itaconic acid-acrylamide terpolymer.

[0008] Optionally, the mass ratio of the modified natural polymer to the synthetic non-sulfonated polymer is 1:1.5~2.5.

[0009] The present invention also provides a method for preparing a high-temperature resistant non-sulfonated composite filtration reducer for drilling fluid, comprising the following steps: compounding modified natural polymers with synthetic non-sulfonated polymers at a mass ratio of 1:1.5~2.5.

[0010] Optionally, the preparation of the modified natural polymer includes the following steps: adding konjac glucomannan powder to deionized water to prepare a konjac glucomannan solution with a mass concentration of 3% to 8%, heating to 50 to 70°C, adding 6% to 10% of the konjac glucomannan mass of etherifying agent and 2% to 4% of the konjac glucomannan mass of crosslinking agent, reacting at a constant temperature for 2 to 3 hours, cooling to room temperature, filtering, vacuum drying, and pulverizing to obtain the modified natural polymer.

[0011] Optionally, the etherifying agent is propylene oxide, and the crosslinking agent is aluminum trichloride.

[0012] Optionally, the preparation of the synthetic non-sulfonated polymer includes the following steps: using deionized water as a solvent, adding acrylic acid, itaconic acid, and acrylamide, then adding ammonium persulfate accounting for 0.3%~0.7% of the total mass of the monomers, heating to 60~80℃ and reacting for 3~5 hours, cooling, removing water by vacuum distillation, and pulverizing to obtain the synthetic non-sulfonated polymer.

[0013] Optionally, the molar ratio of acrylic acid, itaconic acid, and acrylamide is 1~3:1:2~4.

[0014] This invention also provides a high-temperature resistant, non-sulfonated, environmentally friendly water-based drilling fluid, the drilling fluid comprising: Base liquid: water; The above-mentioned non-sulfonated composite filtration loss reducer is used at a concentration of 2.0% to 4.0%. Nano-organic-inorganic composite plugging agent: 0.5%~1.5%; Environmentally friendly shale inhibitors: 1.0%~3.0%; Non-sulfonated flow pattern modifier: 0.3%~0.8%; Environmentally friendly lubricant: 0.8%~1.5%; Weighting agent: Adjust the drilling fluid density to 1.2~2.0 g / cm³. 3 .

[0015] Optionally, the water is fresh water or clean water with a mineralization degree ≤500mg / L; the nano-organic-inorganic composite plugging agent is composed of nano-silica and modified bio-based resin in a mass ratio of 2:1; the environmentally friendly shale inhibitor is dendritic polyamine; the non-sulfonated flow pattern regulator is hydroxypropyl guar gum with a degree of substitution of 0.4~0.6; the environmentally friendly lubricant is obtained by compounding ricinoleic acid and sucrose ester in a mass ratio of 3:1 with a lubrication coefficient ≤0.12; and the weighting agent is barite and / or micro-manganese mineral powder.

[0016] This invention also provides a method for preparing high-temperature resistant, non-sulfonated, environmentally friendly water-based drilling fluid, comprising the following steps: injecting the prescribed amount of clean water into a mixing tank, turning on the stirring device, adjusting the stirring speed to 600~800 r / min, slowly adding a non-sulfonated flow modifier at room temperature, and continuing to stir for 15~20 min to obtain a uniform base fluid; While maintaining a constant stirring speed, slowly add the non-sulfonated composite filtration loss reducer and the environmentally friendly shale inhibitor to the base solution in sequence. After each component is added, continue stirring for 20 to 30 minutes. Add the nano-organic-inorganic composite sealing agent, increase the stirring speed to 1000~1200r / min, and simultaneously turn on ultrasonic-assisted dispersion, stirring for 30~40min; Reduce the stirring speed to 800-1000 rpm, add environmentally friendly lubricant, and stir for 15-20 minutes. Then, slowly add weighting agent as needed and continue stirring for 25-35 minutes, checking the drilling fluid density every 10 minutes until the density reaches 1.2-2.0 g / cm³. 3 Target value; The prepared drilling fluid is transferred to a high-temperature aging tank, sealed, and aged in a 200℃ constant temperature oven. After being removed and cooled to room temperature, it is stirred at 750~850r / min for 8~12min to obtain a high-temperature resistant, non-sulfonated, environmentally friendly water-based drilling fluid.

[0017] The beneficial effects of this invention are: I. This invention abandons traditional sulfonation treatment agents and uses environmentally friendly components such as modified natural polymers, synthetic non-sulfonated polymers, and bio-based modified materials to construct a fully non-sulfonated system. The system has a biodegradability rate of ≥90%, EC50 >50000mg / L, and no biotoxicity, fully meeting drilling environmental standards. Drilling fluid waste requires no complex treatment; simple solid-liquid separation is sufficient for compliant discharge. Compared to traditional polysulfonated drilling fluid waste treatment, the cost is reduced by more than 40%, making it suitable for construction in areas with stringent environmental regulations.

[0018] II. The core innovation of this invention lies in the synergistic design of a non-sulfonated composite filtration loss reducer and a nano-organic-inorganic composite plugging agent. The dual-modified konjac glucomannan and the terpolymer form a "natural-synthetic" composite structure, significantly improving molecular chain stability at high temperatures. The nano-plugging agent avoids high-temperature agglomeration through organic-inorganic composite processing. The synergistic effect of both ensures that the drilling fluid retains ≥85% viscosity and has a high-temperature, high-pressure filtration loss ≤10mL after aging at 200℃ for 72 hours. This solves the problems of high-temperature degradation and performance control issues in traditional non-sulfonated systems, and increases the upper limit of high-temperature resistance by more than 20℃ compared to existing non-sulfonated systems.

[0019] III. This invention constructs an integrated functional system of "filtration loss reduction, plugging, inhibition, and lubrication," with each component working synergistically. The nanocomposite plugging agent achieves a plugging rate of ≥88% in dense sandstone, effectively filling micro-cracks and pores. The dendritic polyamine inhibitor reduces the hydration swelling rate of shale to below 15%, exhibiting superior inhibition compared to traditional polyamine inhibitors. The drilling fluid dynamic-plastic ratio remains stable at 0.5~0.6, demonstrating strong suspension and rock-carrying capacity, effectively preventing wellbore collapse, stuck pipe, and high filtration loss, making it suitable for complex, high-temperature, deep well conditions.

[0020] IV. The preparation process of this invention requires no special equipment. Ultrasonic-assisted dispersion can be easily adapted to simple on-site modifications. All components are readily available and the cost is controllable, reducing costs by more than 60% compared to oil-based drilling fluids. The formulation is highly adjustable, and by adjusting the amount of weighting agent and the ratio of functional components, it can be adapted to formations with different density requirements of 1.2~2.0 g / cm3. It has high flexibility in field application and broad prospects for large-scale promotion. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] In a first aspect, the present invention provides a high-temperature resistant non-sulfonated composite filtration reducer for drilling fluids, wherein the non-sulfonated composite filtration reducer comprises a modified natural polymer and a synthetic non-sulfonated polymer. The modified natural polymer is an etherified-crosslinked double-modified konjac glucomannan; the synthetic non-sulfonated polymer is an acrylic acid-itaconic acid-acrylamide terpolymer. Here, high-temperature resistance specifically refers to 200℃.

[0023] In this embodiment, the mass ratio of the modified natural polymer to the synthetic non-sulfonated polymer is 1:1.5 to 2.5. For example, 1:1.2, 1:2, or 1:2.2.

[0024] The non-sulfonated composite filtration loss reducer of this invention is composed of modified natural polymers and synthetic non-sulfonated polymers in a mass ratio of 1:1.5~2.5. The two work synergistically to form a dense filter cake and resist high-temperature degradation. Secondly, the present invention provides a method for preparing a high-temperature resistant non-sulfonated composite filtration reducer for drilling fluids, comprising the following steps: compounding modified natural polymers and synthetic non-sulfonated polymers at a mass ratio of 1:1.5~2.5.

[0025] In this embodiment, the preparation of the modified natural polymer includes the following steps: Konjac glucomannan powder is added to deionized water to prepare a konjac glucomannan solution with a mass concentration of 3%–8%. The solution is heated to 50–70°C, and etherifying agent (6%–10% by mass of konjac glucomannan) and crosslinking agent (2%–4% by mass of konjac glucomannan) are added. The mixture is reacted at a constant temperature for 2–3 hours. After cooling to room temperature, the mixture is filtered, vacuum dried, and pulverized to obtain the modified natural polymer. For example, konjac glucomannan solutions with mass concentrations of 5%, 6%, and 7% can be prepared. The solution is heated to 55%, 60%, and 65°C. Etherifying agent (7%, 8%, and 9% by mass of konjac glucomannan) and crosslinking agent (2.5%, 3%, and 3.5% by mass of konjac glucomannan) are added. The mixture is reacted at a constant temperature for 2.5 hours.

[0026] In this embodiment, the etherifying agent is propylene oxide and the crosslinking agent is aluminum trichloride.

[0027] In this embodiment, the vacuum drying temperature is 50~70℃, preferably 60℃, and the vacuum drying time is 3~5h, preferably 4h.

[0028] In this embodiment, the material is pulverized to 70-90 mesh, preferably 80 mesh.

[0029] The modified natural polymer of this invention introduces high-temperature resistant ether bonds (-O-CH2-CH(OH)-CH3) through etherification, and forms a three-dimensional network structure through cross-linking. It is not easily degraded at high temperatures, and its natural hydrophilicity allows it to be quickly adsorbed onto the surface of the filter cake, reducing the filter cake permeability.

[0030] In this embodiment, the preparation of the synthetic non-sulfonated polymer includes the following steps: using deionized water as a solvent, acrylic acid, itaconic acid, and acrylamide are added, followed by the addition of ammonium persulfate at a mass of 0.3% to 0.7% of the total monomer mass. The mixture is heated to 60 to 80°C and reacted for 3 to 5 hours. After cooling, the water is removed by vacuum distillation, and the mixture is pulverized to obtain the synthetic non-sulfonated polymer. For example, ammonium persulfate at a mass of 0.4%, 0.5%, and 0.6% of the total monomer mass is added. The temperature is raised to 65°C, 70°C, and 75°C, and the reaction time is 3.5 hours, 4 hours, and 4.5 hours, respectively.

[0031] In this embodiment, the molar ratio of acrylic acid, itaconic acid, and acrylamide is 1~3:1:2~4. For example, the molar ratio of acrylic acid, itaconic acid, and acrylamide is 2:1:3, 2.2:1:3.5, or 2.5:1:3.5.

[0032] In this embodiment, the material is pulverized to 90-110 mesh, preferably 100 mesh.

[0033] The copolymer of this invention introduces pyrrole heterocyclic groups into its molecular structure, without sulfonated groups (-SO3H). The molecular chain entanglement ability is stable at 200°C, and it can synergize with modified konjac glucomannan to further densify the filter cake structure and control the filtration loss.

[0034] Thirdly, addressing the problems of poor environmental performance of sulfonated drilling fluids, insufficient high-temperature resistance of non-sulfonated drilling fluids, weak functional synergy, and limited adaptability in existing technologies, this invention aims to provide a high-temperature resistant (200℃) non-sulfonated environmentally friendly water-based drilling fluid and its preparation method. Specific objectives are as follows: Develop a fully non-sulfonated composite treatment agent system, completely eliminating sulfonated components, ensuring a biodegradability rate ≥90%, no biotoxicity, meeting stringent environmental standards, and reducing waste disposal costs; through structural innovation and synergistic design of the core treatment agent, achieve stable rheological properties, low filtration loss, and viscosity retention rate ≥85% after aging at 200℃ for 72 hours; construct an integrated functional system of "filtration loss reduction - nano-plugging - shale inhibition - lubrication" to improve the plugging rate of micro-fractured formations and the ability to inhibit shale hydration, reducing the risk of wellbore collapse; simultaneously provide a simple, parameter-controllable preparation method adapted to field equipment, enabling large-scale application while balancing technical performance and economic efficiency.

[0035] This invention provides a high-temperature resistant, non-sulfonated, environmentally friendly water-based drilling fluid, the drilling fluid comprising: Base liquid: water; The above-mentioned non-sulfonated composite filtration loss reducer is used at a concentration of 2.0% to 4.0%. Nano-organic-inorganic composite plugging agent: 0.5%~1.5%; Environmentally friendly shale inhibitors: 1.0%~3.0%; Non-sulfonated flow pattern modifier: 0.3%~0.8%; Environmentally friendly lubricant: 0.8%~1.5%; Weighting agent: Adjust the drilling fluid density to 1.2~2.0 g / cm³. 3 .

[0036] In this embodiment, the water is fresh water or clean water with a mineralization degree ≤500mg / L.

[0037] In this embodiment, the nano-organic-inorganic composite sealing agent is composed of nano-silica and modified bio-based resin in a mass ratio of 2:1, and the organic-inorganic phases are tightly bonded through surface modification.

[0038] Here is the specific preparation process of the nano-organic-inorganic composite sealing agent: Spherical nano-silica particles with a diameter of 50-100 nm are selected and surface-modified with silane coupling agent KH-550. The modification process involves dispersing nano-silica in anhydrous ethanol, adding 5% (by weight) of KH-550, ultrasonically dispersing for 30 min, heating to 50℃, reacting for 2 h, centrifuging, and drying to obtain modified nano-silica. Modified bio-based resin is obtained by using soybean protein resin as raw material, adding 10% (by weight) of epichlorohydrin for cross-linking modification, heating to 80℃, reacting for 1.5 h, cooling, and pulverizing to 200 mesh. The composite process involves mixing modified nano-silica and modified bio-based resin, adding an appropriate amount of anhydrous ethanol, ultrasonically dispersing for 40 min, then vacuum drying at 50℃ for 3 h, and pulverizing to 150 mesh to obtain the composite sealing agent.

[0039] In this embodiment, the environmentally friendly shale inhibitor is a dendritic polyamine (a third-generation dendritic molecule with ethylenediamine as its core), without sulfonation components. The preparation process of the environmentally friendly shale inhibitor is as follows: using ethylenediamine as the initiator, it undergoes a Michael addition reaction with methyl acrylate, followed by an aminolysis reaction to prepare the third-generation dendritic polyamine, with a product purity ≥98%. This inhibitor has a biodegradability rate ≥90% (compliant with OECD 301B standards) and inhibits shale hydration through a triple mechanism: first, it adsorbs onto the shale surface to neutralize negative charges, reducing the repulsive force between shale particles; second, it compresses the electric double layer, reducing the entry of water molecules into the shale interlayer; and third, it works synergistically with nano-blocking agents to form a composite protective film on the shale surface, further preventing hydration expansion.

[0040] In this embodiment, the non-sulfonated flow pattern modifier is hydroxypropyl guar gum with a degree of substitution of 0.4~0.6. It is easily soluble at room temperature, can adjust the dynamic-plastic ratio of drilling fluid to 0.5~0.6, improve the suspension and rock-carrying capacity, has a viscosity retention rate of ≥90% at high temperature, has no sulfonated groups, and does not affect environmental performance.

[0041] In this embodiment, the environmentally friendly lubricant is a plant extract compound system, which is obtained by compounding ricinoleic acid and sucrose ester in a mass ratio of 3:1. It has a lubrication coefficient ≤0.12, is non-toxic and biodegradable, and has a biodegradation rate ≥92%. At the same time, it can improve the lubricity of filter cake and reduce drill wear.

[0042] In this embodiment, the weighting agent is barite and / or micro manganese mineral powder.

[0043] Fourthly, the present invention provides a method for preparing a high-temperature resistant, non-sulfonated, environmentally friendly water-based drilling fluid, comprising the following steps: Preparation of the base solution: Pour the prescribed amount of water into a mixing tank, turn on the stirring device, and adjust the stirring speed to 600~800 r / min. Slowly add the non-sulfonated flow pattern regulator at room temperature, and continue stirring for 15~20 min until completely dissolved and no visible particles are found, thus obtaining a homogeneous base solution. Here, the room temperature is 25±5℃.

[0044] Addition of functional components: While maintaining a constant stirring speed, slowly add the non-sulfonated composite filtration loss reducer and the environmentally friendly shale inhibitor to the base solution in sequence. After each component is added, continue stirring for 20-30 minutes to ensure that the components are fully dispersed and dissolved, and to avoid local agglomeration.

[0045] Dispersion of the sealing agent: Add the nano-organic-inorganic composite sealing agent, increase the stirring speed to 1000~1200r / min, and at the same time turn on the ultrasonic-assisted dispersion (power 200~400W, preferably 300W), stir for 30~40min to make the nanoparticles uniformly dispersed in the system without agglomeration.

[0046] Lubricant and weighting agent addition: Reduce the stirring speed to 800-1000 rpm, add environmentally friendly lubricant, and stir for 15-20 minutes; then slowly add weighting agent as needed, and continue stirring for 25-35 minutes, checking the drilling fluid density every 10 minutes until the density reaches 1.2-2.0 g / cm³. 3 The target value.

[0047] High-temperature aging stabilization: The prepared drilling fluid is transferred to a high-temperature aging tank, sealed, and aged in a 200℃ constant-temperature oven. After removal, it is cooled to room temperature and stirred at 750~850r / min (preferably 800r / min) for 8~12min (preferably 10min) to obtain a high-temperature resistant, non-sulfonated, environmentally friendly water-based drilling fluid. Here, the aging time is 70~74h, preferably 72h.

[0048] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0049] The present invention will be described in detail below through embodiments and experimental examples. However, these are merely examples and do not limit the present invention in any way.

[0050] Example 1 This embodiment provides a high-temperature resistant (200℃) non-sulfonated environmentally friendly water-based drilling fluid with a suitable density of 1.4 g / cm³. 3 The medium-to-low density strata are as follows: Components and proportions (based on 1000kg of clean water, by mass percentage): 2.5% non-sulfonated composite filtration loss reducer (10kg modified konjac glucomannan + 15kg acrylic acid-itaconic acid-acrylamide terpolymer), 0.8% (8kg) nano-organic-inorganic composite plugging agent, 1.5% (15kg) environmentally friendly shale inhibitor, 0.5% (5kg) non-sulfonated flow pattern regulator, 1.0% (10kg) environmentally friendly lubricant, and weighting agent (ultrafine calcium carbonate) added as needed (adjust density to 1.4g / cm³). 3 ).

[0051] Preparation method: The preparation steps of the above technical solution were carried out. The stirring speeds were 700 r / min (addition of base liquid and functional components), 1100 r / min (dispersion of nano-blocking agent, ultrasonic power 300W), and 900 r / min (addition of lubricant and weighting agent). The stirring times for each stage were 18 min, 25 min, 35 min, 18 min, and 30 min, respectively. After aging at 200℃ for 72 h, the mixture was taken out and stirred evenly.

[0052] Performance testing: Apparent viscosity after aging is 32 mPa·s, viscosity retention rate is 86%, high temperature and high pressure filtration loss is 9.5 mL / 30 min, clogging rate is 88.2%, shale expansion rate is 14.8%, lubrication coefficient is 0.12, biodegradation rate is 91%, and EC50 is >50000 mg / L.

[0053] Example 2 This embodiment provides a high-temperature resistant (200℃) non-sulfonated environmentally friendly water-based drilling fluid with a suitable density of 1.6 g / cm³. 3 The medium-to-high density strata are as follows: Components and proportions (based on 1000kg of clean water, by mass percentage): 3.0% non-sulfonated composite filtration loss reducer (12kg modified konjac glucomannan + 18kg acrylic acid-itaconic acid-acrylamide terpolymer), 1.0% (10kg) nano-organic-inorganic composite plugging agent, 2.0% (20kg) environmentally friendly shale inhibitor, 0.6% (6kg) non-sulfonated flow pattern regulator, 1.2% (12kg) environmentally friendly lubricant, and weighting agent (ultrafine calcium carbonate) added as needed (adjusting density to 1.6g / cm³). 3 ).

[0054] Preparation method: The preparation steps of the above technical solution were carried out. The stirring speeds were 750 r / min (addition of base liquid and functional components), 1150 r / min (dispersion of nano-blocking agent, ultrasonic power 300W), and 900 r / min (addition of lubricant and weighting agent). The stirring times for each stage were 18 min, 25 min, 35 min, 20 min, and 30 min, respectively. After aging at 200℃ for 72 h, the mixture was taken out and stirred evenly.

[0055] Performance testing: Apparent viscosity after aging is 38 mPa·s, viscosity retention rate is 88%, high temperature and high pressure filtration loss is 8.2 mL / 30 min, clogging rate is 90.5%, shale expansion rate is 12.5%, lubrication coefficient is 0.11, biodegradation rate is 93%, and EC50 is >50000 mg / L.

[0056] Example 3 This embodiment provides a high-temperature resistant (200℃) non-sulfonated environmentally friendly water-based drilling fluid with a suitable density of 1.8 g / cm³. 3 The high-density strata are as follows: Components and proportions (based on 1000kg of clean water, by mass percentage): 3.5% non-sulfonated composite filtration loss reducer (14kg modified konjac glucomannan + 21kg acrylic acid-itaconic acid-acrylamide terpolymer), 1.2% (12kg) nano-organic-inorganic composite plugging agent, 2.5% (25kg) environmentally friendly shale inhibitor, 0.7% (7kg) non-sulfonated flow pattern regulator, 1.4% (14kg) environmentally friendly lubricant, and weighting agent (ultrafine calcium carbonate) added as needed (to adjust density to 1.8g / cm³). 3 ).

[0057] Preparation method: The preparation steps of the above technical solution were followed. The stirring speeds were 800 r / min (addition of base liquid and functional components), 1200 r / min (dispersion of nano-blocking agent, ultrasonic power 300W), and 1000 r / min (addition of lubricant and weighting agent). The stirring times for each stage were 20 min, 30 min, 40 min, 20 min, and 35 min, respectively. After aging at 200℃ for 72 h, the mixture was taken out and stirred evenly.

[0058] Performance testing: Apparent viscosity after aging is 45 mPa·s, viscosity retention rate is 90%, high temperature and high pressure filtration loss is 7.8 mL / 30 min, clogging rate is 92.1%, shale expansion rate is 10.2%, lubrication coefficient is 0.10, biodegradation rate is 95%, and EC50 is >50000 mg / L.

[0059] Comparative Example 1 (Traditional Polysulfonate Drilling Fluid) Comparative Example 1 uses existing conventional polysulfonate drilling fluid with a suitable density of 1.6 g / cm³. 3The geological formation is compared with that of Example 2, as follows: Components and proportions (based on 1000kg of clean water, by weight percentage): Water balance, sulfonated lignite 3.0% (30kg), sulfonated phenolic resin 2.0% (20kg), potassium polyacrylamide 0.5% (5kg), asphalt-based sealant 1.0% (10kg), crude oil lubricant 1.5% (15kg), weighting agent (barite) added as needed (adjust density to 1.6g / cm³). 3 ).

[0060] Preparation method: Following the conventional polysulfonated drilling fluid preparation process, sulfonated lignite, sulfonated phenolic resin, and potassium polyacrylamide are added sequentially under stirring with clean water, stirring for 20 minutes at each step. Then, asphalt-based plugging agent and crude oil lubricant are added and stirred for 15 minutes. Finally, barite is added to adjust the density and stirred for 30 minutes. After aging at 200℃ for 72 hours, the mixture is taken out and stirred evenly.

[0061] Performance testing: Apparent viscosity after aging is 35 mPa·s, viscosity retention rate is 75%, high temperature and high pressure filtration loss is 12.3 mL / 30 min, clogging rate is 80.3%, shale expansion rate is 18.6%, lubrication coefficient is 0.10, biodegradation rate is 35%, and EC50 is 8000 mg / L.

[0062] Performance Comparison and Analysis The drilling fluids from Examples 1-3 and Comparative Example 1 underwent uniform performance testing according to the following standards: apparent viscosity was tested according to industry standards; viscosity retention rate = (apparent viscosity after aging / apparent viscosity before aging) × 100%; high-temperature and high-pressure filtration loss was tested according to API standards (3.5 MPa pressure, 200℃ temperature); plugging rate was tested using the core permeability method; shale swelling rate was tested according to SY / T 5613-2016; biodegradation rate was tested according to GB / T 21803-2008 standards; and biotoxicity (EC50) was tested according to GB / T21805-2008. The test results are summarized in the table below: Based on the test results and the formulation design of each system, the following in-depth analysis is conducted: High-temperature stability analysis: The viscosity retention rates of Examples 1-3 were all ≥86%, significantly higher than the 75% of Comparative Example 1, and the high-temperature and high-pressure filtration loss was reduced by 23.6%~36.6% compared to Comparative Example 1. The core reason is that the non-sulfonated composite filtration loss reducer of this invention, through the synergistic effect of "double-modified natural polymer + synthetic non-sulfonated polymer", significantly improves the high-temperature resistance of the molecular chain. In contrast, the sulfonated lignite and sulfonated phenolic resin of Comparative Example 1 are prone to sulfonation group shedding at 200℃, leading to molecular chain degradation and decreased system stability. Meanwhile, Example 3 had the highest dosage of filtration loss reducer and sealing agent, with a viscosity retention rate of 90% and the lowest filtration loss, indicating that increasing the dosage of core functional components can further improve high-temperature stability and adapt to more demanding working conditions.

[0063] Comprehensive drilling performance analysis: The plugging rates of Examples 1-3 were all ≥88.2%, and the shale expansion rate was ≤14.8%, significantly improving wellbore stability compared to Comparative Example 1 (plugging rate 80.3%, shale expansion rate 18.6%). This is because the nano-organic-inorganic composite plugging agent can fill micro-cracks and pores, forming a synergistic protection with the dendritic polyamine inhibitor. In contrast, the asphalt-based plugging agent in Comparative Example 1 can only plug micron-level pores, failing to cover nano-level micro-cracks, and lacks components that effectively inhibit shale hydration, resulting in insufficient wellbore stability. Furthermore, the lubrication coefficient of Example 3 was comparable to that of Comparative Example 1, indicating that the present invention improves environmental friendliness and stability without sacrificing lubrication performance, achieving a more balanced overall function.

[0064] Environmental performance analysis: Examples 1-3 exhibit a biodegradability rate ≥91% and EC50 >50000mg / L, classifying them as non-toxic and environmentally friendly systems. In contrast, Comparative Example 1 shows a biodegradability rate of only 35% and EC50 = 9000mg / L, indicating moderate toxicity and a significant difference in environmental performance. The core difference lies in the fact that this invention uses entirely non-sulfonated environmentally friendly components, eliminating toxic and recalcitrant sulfonating agents and crude oil lubricants. Comparative Example 1, with its sulfonated components and crude oil lubricants, is difficult to biodegrade and easily causes environmental pollution, further demonstrating the environmental innovation of this invention.

[0065] Formulation compatibility analysis: Example 1 (density 1.4 g / cm³) 3 Example 2 (density 1.6 g / cm³) 3 Example 3 (density 1.8 g / cm³) 3 All properties of the product meet the requirements of the corresponding formation. Furthermore, as density increases, the dosage of the core functional components increases synchronously, and performance is gradually optimized. This demonstrates that the formulation of this invention is highly adjustable and can be flexibly adjusted according to different well depths and formation density requirements, with a wide range of applicability. Example 2, as the preferred solution, balances performance, cost, and ease of construction, achieving a concentration of 1.6 g / cm³. 3 It exhibits optimal overall performance under high-density operating conditions, making it suitable for large-scale field applications.

[0066] Example 4 This embodiment provides a high-temperature resistant (200℃) non-sulfonated environmentally friendly water-based drilling fluid, including the following steps: (1) Raw material preparation Based on 1000 kg of clean water, prepare the following raw materials: 1000 kg of clean water (mineralization 320 mg / L), 30 kg of non-sulfonated composite filtration loss reducer (12 kg of modified konjac glucomannan + 18 kg of acrylic acid-itaconic acid-acrylamide terpolymer, prepared according to the above process), 10 kg of nano-organic-inorganic composite sealing agent (prepared in-house, 6.7 kg of nano-silica + 3.3 kg of modified bio-based resin), 20 kg of environmentally friendly shale inhibitor (dendritic polyamine, purity 98%), 6 kg of non-sulfonated flow modifier (hydroxypropyl guar gum, degree of substitution 0.5), 12 kg of environmentally friendly lubricant (a compound system of ricinoleic acid and sucrose ester), and 420 kg of weighting agent (ultrafine calcium carbonate, particle size 1~5 μm) (adjusting density to 1.6 g / cm³). 3 ).

[0067] (2) Preparation process 1) Pour 1000 kg of clean water into the on-site mixing tank (volume 2 m³, speed adjustable range 0~1500 r / min), turn on the stirring device, adjust the speed to 750 r / min, slowly add 6 kg of non-sulfonated flow conditioner at room temperature (28℃), and continue stirring for 18 min until completely dissolved to obtain a uniform base liquid. 2) Maintain a stirring speed of 750 r / min, first add 30 kg of non-sulfonated composite filtration loss reducer, stir for 25 min, then add 20 kg of environmentally friendly shale inhibitor, continue stirring for 25 min, ensure that the two components are fully dispersed and dissolved, and take samples to observe that there are no obvious particles; 3) Add 10kg of nano-organic-inorganic composite sealing agent, increase the stirring speed to 1150r / min, and at the same time turn on the ultrasonic device on the tank wall (power 300W) for ultrasonic-assisted dispersion for 35min. During this period, take samples every 10min to ensure that the nanoparticles do not agglomerate and the system is uniform. 4) Reduce the stirring speed to 900 rpm, add 12 kg of environmentally friendly lubricant, and stir for 20 minutes. Then, slowly add 420 kg of weighting agent in batches (100 kg each time, with a 5-minute interval), and continue stirring for 30 minutes. Use a drilling fluid density meter to check the density and ensure that the density is stable at 1.6 g / cm³. 3 ; 5) Transfer the prepared drilling fluid to a high-temperature aging tank, seal it, and place it in a 200℃ constant temperature oven for aging for 72 hours. After taking it out, cool it to room temperature (25℃), stir it at 800r / min for 10 minutes to obtain the finished drilling fluid, and take a sample for later use.

[0068] (3) On-site application effect The finished drilling fluid was applied in a high-temperature deep well (5200m deep, bottom hole temperature 200℃, formation containing microfractures and easily hydrated shale). Its main performance characteristics during application are as follows: Wellbore stability: The open-hole diameter enlargement rate was only 4.5%, which is 45.1% lower than the diameter enlargement rate (8.2%) of the adjacent well using traditional polysulfonate drilling fluid. There was no wellbore collapse or block falling. Electrical logging and casing installation were successful on the first attempt, and there were no stuck pipe incidents. Performance stability: During continuous monitoring for 72 hours during drilling, the apparent viscosity remained stable at 37~39 mPa·s, the dynamic-plastic ratio remained at 0.55, and the high-temperature and high-pressure filtration loss remained stable at 8.0~8.4 mL / 30 min, with no significant fluctuations in performance; Environmental benefits: After simple solid-liquid separation, the filtrate from drilling waste has a biodegradation rate of 92%, meeting the standards for farmland irrigation water quality. No additional chemical treatment is required, saving 38% in environmental treatment costs compared to traditional polysulfonated drilling fluid. Construction efficiency: The drilling speed is increased by 12.3% compared to adjacent wells, the wear of drill bits is reduced by 15%, and the overall construction cost is reduced by more than 20%, demonstrating significant application effects.

[0069] In summary, the high-temperature resistant, non-sulfonated, environmentally friendly water-based drilling fluid of the present invention exhibits excellent performance in terms of high-temperature stability, overall drilling performance, and environmental friendliness, and can effectively meet the drilling needs of deep, high-temperature wells and areas with stringent environmental requirements.

[0070] Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0071] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-temperature resistant, non-sulfonated composite filtration reducer for drilling fluids, characterized in that, The non-sulfonated composite filtration loss reducer comprises modified natural polymers and synthetic non-sulfonated polymers; The modified natural polymer is etherified-crosslinked double-modified konjac glucomannan; the synthesized non-sulfonated polymer is an acrylic acid-itaconic acid-acrylamide terpolymer.

2. The high-temperature resistant non-sulfonated composite filtration reducer for drilling fluids according to claim 1, characterized in that, The mass ratio of the modified natural polymer to the synthetic non-sulfonated polymer is 1:1.5~2.

5.

3. The method for preparing the high-temperature resistant non-sulfonated composite filtration reducer for drilling fluid according to claim 1 or 2, characterized in that, Includes the following steps: It is made by compounding modified natural polymers with synthetic non-sulfonated polymers at a mass ratio of 1:1.5~2.

5.

4. The preparation method of the high-temperature resistant non-sulfonated composite filtration reducer for drilling fluid according to claim 3, characterized in that, The preparation of the modified natural polymer includes the following steps: Konjac glucomannan powder was added to deionized water to prepare a konjac glucomannan solution with a mass concentration of 3% to 8%. The solution was heated to 50 to 70°C, and etherifying agent of 6% to 10% by mass of konjac glucomannan and crosslinking agent of 2% to 4% by mass were added. The solution was reacted at a constant temperature for 2 to 3 hours. After cooling to room temperature, the solution was filtered, vacuum dried, and pulverized to obtain the modified natural polymer.

5. The preparation method of the high-temperature resistant non-sulfonated composite filtration reducer for drilling fluid according to claim 4, characterized in that, The etherifying agent is propylene oxide. The crosslinking agent is aluminum trichloride.

6. The method for preparing the high-temperature resistant non-sulfonated composite filtration reducer for drilling fluid according to claim 3, characterized in that, The preparation of synthetic non-sulfonated polymers includes the following steps: Using deionized water as a solvent, acrylic acid, itaconic acid, and acrylamide were added, followed by ammonium persulfate at a mass of 0.3% to 0.7% of the total monomer mass. The mixture was heated to 60 to 80°C and reacted for 3 to 5 hours. After cooling, the water was removed by vacuum distillation and the mixture was pulverized to obtain the synthesized non-sulfonated polymer.

7. The preparation method of the high-temperature resistant non-sulfonated composite filtration reducer for drilling fluid according to claim 6, characterized in that, The molar ratio of acrylic acid, itaconic acid, and acrylamide is 1~3:1:2~4.

8. A high-temperature resistant, non-sulfonated, environmentally friendly water-based drilling fluid, characterized in that, The drilling fluid includes: Base liquid: water; The non-sulfonated composite filtration loss reducer as described in claim 1 or 2 is used at a concentration of 2.0% to 4.0%. Nano-organic-inorganic composite plugging agent: 0.5%~1.5%; Environmentally friendly shale inhibitors: 1.0%~3.0%; Non-sulfonated flow pattern modifier: 0.3%~0.8%; Environmentally friendly lubricant: 0.8%~1.5%; Weighting agent: Adjust the drilling fluid density to 1.2~2.0 g / cm³. 3 .

9. The drilling fluid according to claim 8, characterized in that, The water is fresh water or clean water with a mineralization degree ≤500mg / L; The nano-organic-inorganic composite sealing agent is composed of nano-silica and modified bio-based resin in a mass ratio of 2:

1. The environmentally friendly shale inhibitor is dendritic polyamine; The non-sulfonated flow pattern modifier is hydroxypropyl guanidine gum with a degree of substitution of 0.4 to 0.

6. The environmentally friendly lubricant is obtained by compounding ricinoleic acid and sucrose ester in a mass ratio of 3:1, and has a lubrication coefficient ≤0.12; The weighting agent is barite and / or micro manganese mineral powder.

10. The method for preparing high-temperature resistant, non-sulfonated, environmentally friendly water-based drilling fluid according to claim 8 or 9, characterized in that, Includes the following steps: Pour the prescribed amount of water into the mixing tank, turn on the stirring device, adjust the stirring speed to 600~800r / min, slowly add the non-sulfonated flow pattern regulator at room temperature, and continue stirring for 15~20min to obtain a uniform base liquid. While maintaining a constant stirring speed, slowly add the non-sulfonated composite filtration loss reducer and the environmentally friendly shale inhibitor to the base solution in sequence. After each component is added, continue stirring for 20 to 30 minutes. Add the nano-organic-inorganic composite sealing agent, increase the stirring speed to 1000~1200r / min, and simultaneously turn on ultrasonic-assisted dispersion, stirring for 30~40min; Reduce the stirring speed to 800-1000 rpm, add environmentally friendly lubricant, and stir for 15-20 minutes. Then, slowly add weighting agent as needed and continue stirring for 25-35 minutes, checking the drilling fluid density every 10 minutes until the density reaches 1.2-2.0 g / cm³. 3 Target value; The prepared drilling fluid is transferred to a high-temperature aging tank, sealed, and aged in a 200℃ constant temperature oven. After being removed and cooled to room temperature, it is stirred at 750~850r / min for 8~12min to obtain a high-temperature resistant, non-sulfonated, environmentally friendly water-based drilling fluid.

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