A lubricating and fluid loss control agent for drilling fluid

Abstract

This application relates to an in-situ emulsifiable drilling fluid lubricant-filtration reducer, comprising: acrylic acid (AA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylamide (AM), a 10-20% sodium hydroxide aqueous solution, a compound emulsifier, and an initiator. It effectively solves the technical bottlenecks of traditional water-based drilling fluids, such as functional separation of lubricant and filtration reducer, mineral oil contamination, and high-temperature performance degradation. It is particularly suitable for water-based drilling fluid systems operating under high-temperature and complex conditions in deep wells, ultra-deep wells, and extended reach wells.

Description

Technical Field

[0001] This invention relates to the field of drilling fluid treatment agents, specifically to a drilling fluid lubricant-filtration loss reducing agent that can be emulsified in situ. Background Technology

[0002] Drilling fluid, often referred to as the "blood" of drilling engineering, plays a crucial role in wellbore stability, wellbore cleaning, drill bit cooling, and lubrication. As domestic oil and gas exploration and development extends into deeper formations and unconventional reservoirs, the proportion of deep, ultra-deep, and horizontal wells is increasing annually, leading to increasingly severe high-temperature, high-pressure, and complex formation conditions during drilling. Under high-temperature environments, drilling fluid treatment agents are prone to degradation, cross-linking, and desorption, resulting in a sharp deterioration in the rheological properties and filtration efficiency of the drilling fluid, seriously threatening the safety and efficiency of drilling operations. Therefore, developing multifunctional drilling fluid treatment agents with excellent temperature resistance is of great significance for ensuring the safe and efficient development of deep oil and gas resources.

[0003] Currently, drilling fluid systems are mainly divided into two categories: water-based drilling fluids and oil-based drilling fluids. While oil-based drilling fluids possess significant advantages such as good lubricity, high temperature resistance, and strong salt resistance, they also have inherent drawbacks including high environmental pollution risks, high costs, and difficulties in post-drilling cleaning. With increasingly stringent environmental regulations, their application is facing growing restrictions. Water-based drilling fluids, due to their low cost and good environmental compatibility, have become the mainstream research and application direction. However, water-based drilling fluids suffer from significantly insufficient lubrication performance and filtration loss control under high-temperature conditions, making it difficult to meet the operational requirements of deep wells, ultra-deep wells, and extended reach wells.

[0004] Regarding drilling fluid additives, current technologies typically employ a compounding of single-function additives, such as filtration reducers, lubricants, and viscosity modifiers, each performing a single function. This approach not only leads to complex drilling fluid formulations, high solids content, and difficult maintenance and management, but also makes it difficult to guarantee the compatibility and synergistic effects between various additives, often resulting in a contradiction where "adding one affects another," ultimately increasing the overall cost of the drilling fluid. Particularly concerning lubrication performance, traditional water-based drilling fluid lubricants, such as mineral oil and vegetable oil, are prone to oxidation, hydrolysis, or desorption at high temperatures, leading to a significant decrease in lubrication performance. Simultaneously, some lubricants and filtration reducers compete for adsorption on clay surfaces, further degrading filtration performance and limiting the overall effectiveness of water-based drilling fluids.

[0005] To address these issues, researchers have attempted to physically compound or chemically bond lubricants with filtration loss reducers to obtain additives with dual functions. For example, polymer microspheres have been prepared via reverse emulsion polymerization, simultaneously imparting filtration loss reduction and lubrication properties. However, existing reverse emulsion polymerization technologies typically use mineral oils such as white oil as the oil phase. While the polymerization process is stable and the product molecular weight distribution is narrow, mineral oils themselves are difficult to biodegrade. Mineral oil residues in drilling fluids, once discharged with drill cuttings, can cause persistent and irreversible negative impacts on soil, groundwater, and ecosystems. Furthermore, when existing reverse emulsion polymerization products are added to water-based drilling fluids, the oil phase often floats freely on the surface or agglomerates, failing to effectively disperse within the system. This significantly reduces lubrication effectiveness and makes it difficult to form a stable boundary lubrication film.

[0006] On the other hand, drilling practices in the Ordos Basin, exemplified by the Changqing Oilfield, have revealed widespread wellbore instability issues in formations such as the Zhifang, Shiqianfeng, and Shihezi Formations. Traditional asphalt-based anti-collapse agents have been gradually phased out due to environmental concerns. Inorganic salt inhibitors require large quantities, negatively impact drilling fluid resistivity, and generate high-salt wastewater. While potassium polyacrylate polymeric inhibitors offer good surface inhibition, their large molecular weight (millions to tens of millions) prevents them from penetrating the mud cake and the semi-permeable membrane formed by the wellbore to reach the formation interior, resulting in poor filtrate inhibition and significant discrepancies between laboratory evaluations and field application results. These issues indicate that drilling fluid treatment agents urgently need to evolve towards multifunctional integration, environmental friendliness, and controllable molecular structures.

[0007] Therefore, developing a multifunctional integrated additive that can replace traditional mineral oil with green and renewable biomass oil phase, achieve in-situ emulsification transformation in drilling fluid, and possess excellent filtration loss reduction and lubrication properties is of great practical significance and has broad application prospects for simplifying drilling fluid formulation, reducing overall costs, reducing environmental pollution, and improving the performance of high-temperature deep well drilling fluids. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, such as the separation of drilling fluid filtration reducer and lubricant functions, the significant environmental pollution from mineral oil-based additives, and the poor dispersion stability of reverse emulsion products in drilling fluids, this invention provides an in-situ emulsifiable drilling fluid lubricant-filtration reducer (hereinafter referred to as LU-FLR) and its preparation method. This integrated agent uses biodegradable oleic acid as the oil phase. Acrylamide (AM), acrylic acid (AA), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) are copolymerized via reverse emulsion polymerization. The resulting emulsion product, after being added to water-based drilling fluid, spontaneously undergoes an in-situ phase transition from water-in-oil (W / O) to oil-in-water (O / W) under the action of an emulsifier, forming a stable oleic acid microdroplet dispersion system, thereby achieving a synergistic effect of filtration reduction and lubrication.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing an in-situ emulsifiable drilling fluid lubricant-filtration loss reducer includes the following steps:

[0011] The first step involves mixing acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and acrylamide (AM) in a reaction vessel at room temperature. The pH is then adjusted to 6.5-7.5 using a 10-20% sodium hydroxide aqueous solution to obtain an aqueous monomer mixture solution. The molar ratio of AA, AM, and AMPS is (0.4~1.2):(1.5~2.5):(0.3~0.6). The AA, AM, and AMPS are industrial-grade or higher purity products, the water is industrial-grade deionized water, and the sodium hydroxide is an industrial-grade or higher purity product.

[0012] The second step involves mixing oleic acid with a compound emulsifier in another reactor at room temperature and stirring until homogeneous to obtain an oil phase. The compound emulsifier is a mixture of industrial-grade or higher purity nonionic polyether surfactants and polyol ester nonionic surfactants, and the hydrophilic-lipophilic balance (HLB) of the system is adjusted to 3.8-5.6.

[0013] The third step involves adding the oil phase to a reactor equipped with a stirrer, thermometer, and nitrogen inlet pipe. Under nitrogen protection, the mixture is stirred at 400-600 r / min. The aqueous phase obtained in the first step is then slowly added dropwise to the oil phase at a rate of one-tenth to one-twentieth of its weight per hour. After the addition is complete, stirring continues for 20-40 minutes to form a stable water-in-oil (W / O) preemulsion. The volume ratio of the oil phase to the aqueous phase is 1:(1-2).

[0014] The fourth step involves adding an initiator accounting for 0.2% to 0.8% of the total monomer mass to the pre-emulsion and stirring the mixture at 50 to 60°C for 2 to 6 hours. The initiator is an industrial grade or higher purity ammonium persulfate / sodium bisulfite, potassium persulfate / sodium bisulfite, azobisisobutyramidine hydrochloride, or azobisisobutyronitrile.

[0015] The fifth step is to cool the product to room temperature after the reaction is complete, thus obtaining the LU-FLR emulsion product, which is an in-situ emulsifiable drilling fluid lubricant and filtration loss reducer.

[0016] In the integrated agent, acrylamide and acrylic acid provide hydration and adsorption groups, giving the polymer good water solubility and adsorption capacity for clay particles; 2-acrylamido-2-methylpropanesulfonic acid provides strong anionic sulfonic acid groups, giving the polymer excellent temperature resistance, salt resistance and rigid molecular chain structure; oleic acid, as a biodegradable green oil phase, is transformed in situ into oleic acid droplets by the oil-in-water emulsifier in the drilling fluid, and adheres to the filter cake surface during filtration to form a boundary oil film, playing a lubricating function; the emulsifier (surfactant) is the key innovation of this invention. The preferred emulsifier system can be used as an emulsifier for water-in-oil emulsions during the polymer synthesis stage, and can be transformed into an emulsifier for oil-in-water emulsions during the drilling fluid use stage, so that in-situ emulsification can be achieved, and oleic acid can be converted into a lubricant without the need for external reagents.

[0017] The method of using the LU-FLR integrated agent prepared by the present invention is as follows: add it directly to the water-based drilling fluid, the amount of which is 1% to 4% of the total mass of the drilling fluid. At the same time, 0.5% to 1.5% of modified starch, CMC, etc. can be compounded to further optimize the filtration loss reduction performance. During the high-temperature aging of drilling fluid or downhole heating, the emulsifier in LU-FLR rearranges at the oil-water interface, driving the in-situ reversal of the water-in-oil emulsion to form an oil-in-water emulsion. The dissolved AA-AM-AMPS terpolymer is adsorbed onto the surface of bentonite particles through hydrogen bonding and electrostatic interactions, increasing the negative charge density and absolute Zeta potential on the particle surface, enhancing the electrostatic repulsion between particles, and inhibiting the agglomeration and flocculation of clay particles at high temperatures. The amide, carboxyl, and sulfonic acid groups on the copolymer molecular chain form a stable organic-inorganic three-dimensional network structure with bentonite, filling the micropores inside the filter cake to form a dense, thin, and low-permeability filter cake, achieving effective filtration loss reduction at high temperatures. At the same time, uniformly dispersed oleic acid droplets are deposited on the surface of the filter cake and the drill string-wellbore contact interface under pressure differential. Through the chemical adsorption of polar carboxyl head groups on the surface of the iron drill string, a boundary lubrication film is formed. Its non-polar long-chain hydrocarbon groups are arranged outward, reducing the shear resistance between friction pairs and significantly reducing the friction coefficient of the drilling fluid.

[0018] The beneficial effects of this invention are as follows:

[0019] (1) Environmental friendliness: Renewable biomass oleic acid is used to replace traditional mineral oil as the oil phase. Oleic acid has excellent biodegradability and low ecotoxicity, avoiding the persistent pollution of soil and groundwater by mineral oil, which is in line with the development direction of green and environmentally friendly drilling fluid.

[0020] (2) In-situ emulsification and stable dispersion: After the LU-FLR emulsion is added to the water-based drilling fluid, the residual nonionic emulsifier spontaneously realizes the in-situ phase transformation from W / O to O / W. The oleic acid microdroplets formed are stably suspended in the system under the synergistic effect of negatively charged bentonite fine particles and dissolved polymers, which overcomes the technical problem of traditional oily lubricants being easy to float and difficult to disperse.

[0021] (3) Dual function of reducing filtration loss and lubrication: AA-AM-AMPS terpolymer forms a three-dimensional network structure between bentonite particles through multi-point adsorption, reducing filter cake permeability and achieving high efficiency in reducing filtration loss at high temperature (120-180℃); dispersed oleic acid microdroplets form a boundary lubrication film on the filter cake and drill tool surface, greatly reducing the friction coefficient. One agent has two effects, simplifying drilling fluid formulation and reducing overall cost.

[0022] (4) Excellent high temperature resistance: The sulfonic acid groups in the AMPS monomer provide strong steric hindrance and negative charge repulsion effect, giving the polymer molecular chain the ability to maintain an extended conformation at high temperature; 2-4% of LU-FLR is added to the water-based drilling fluid base slurry, and after hot rolling aging at 120-180℃, the API filtration loss can be as low as less than 10mL, the HTHP (120-180℃ / 3.5MPa) filtration loss is 20-40mL, and the lubrication coefficient reduction rate is as high as 70% or more;

[0023] (5) Synergistic enhancement effect: The combination of CMC and modified starch and other environmentally friendly drilling fluid treatment agents complements the chemical adsorption of LU-FLR. At the same time, the coating and protection of starch by the polymer can delay the thermal degradation of starch, showing a significant synergistic effect of reducing filtration loss. Therefore, it is suitable for a variety of environmentally friendly drilling fluid systems.

[0024] The in-situ emulsifiable lubricant-filtration loss reducer provided by this invention effectively solves the technical bottlenecks of functional separation of lubricant and filtration loss reducer in traditional water-based drilling fluids, mineral oil contamination, and high-temperature performance degradation. It is especially suitable for water-based drilling fluid systems under high-temperature and complex working conditions such as deep wells, ultra-deep wells, and extended reach wells, and has broad market application prospects. Attached Figure Description

[0025] Figure 1 This is a structural diagram of the water-in-oil (oleic acid) emulsion in the water-based drilling fluid of Example 1. Detailed Implementation

[0026] Example 1

[0027] A method for preparing an in-situ emulsifiable drilling fluid lubricant-filtration loss reducer includes the following steps:

[0028] The first step involves mixing acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and acrylamide (AM) in a reaction vessel at room temperature, adjusting the pH to 7 with a 10% sodium hydroxide aqueous solution to obtain an aqueous monomer mixture solution. The molar ratio of AA, AM, and AMPS is 1:2:0.4. AA, AM, and AMPS are industrial-grade pure products, the water is industrial-grade deionized water, and the sodium hydroxide is an analytical-grade product.

[0029] The second step involves mixing oleic acid with a compound emulsifier in another reactor at room temperature and stirring until homogeneous to obtain the oil phase. The compound emulsifier is a mixture of analytical grade Span 80, Tween 60 and OP-10 in a mass ratio of 88:6:6, and the hydrophilic-lipophilic balance (HLB) of the system is adjusted to 5.6.

[0030] The third step involves adding the oil phase to a reactor equipped with a stirrer, thermometer, and nitrogen inlet pipe. Under nitrogen protection, the mixture is stirred at 600 r / min. The aqueous phase obtained in the first step is then slowly added dropwise to the oil phase at a rate of one-tenth of a part by weight per hour. After the addition is complete, stirring continues for 40 minutes to form a stable water-in-oil (W / O) preemulsion. The volume ratio of the oil phase to the aqueous phase is 1:1.5.

[0031] Fourth step: Add an initiator accounting for 0.3% of the total mass of monomers to the pre-emulsion, and stir the reaction at 60°C for 3 hours. The initiator is analytical grade 2,2'-azobis(2-methylpropanediamine) dihydrochloride.

[0032] The fifth step is to cool the product to room temperature after the reaction is complete, thus obtaining the LU-FLR emulsion product, which is an in-situ emulsifiable drilling fluid lubricant and filtration loss reducer.

[0033] The beneficial effects of this invention are as follows: when 3% LU-FLR is added to 4% water-based drilling fluid slurry and after hot rolling aging at 120°C for 16 hours, the API filtration loss can be as low as 8.8 mL, the HTHP (150°C / 3.5MPa) filtration loss is 23 mL, and the lubrication coefficient reduction rate is as high as 87.03%.

[0034] Example 2

[0035] A method for preparing an in-situ emulsifiable drilling fluid lubricant-filtration loss reducer includes the following steps:

[0036] The first step involves mixing acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and acrylamide (AM) in a reaction vessel at room temperature. The pH is then adjusted to 6.5 using a 15% sodium hydroxide aqueous solution to obtain an aqueous monomer mixture solution. The molar ratio of AA, AM, and AMPS is 0.8:1.5:0.3. AA, AM, and AMPS are analytical grade products, the water is industrial-grade deionized water, and the sodium hydroxide is an analytical grade product.

[0037] The second step involves mixing oleic acid with a compound emulsifier in another reactor at room temperature and stirring until homogeneous to obtain an oil phase. The compound emulsifier is a mixture of analytical grade Span 85, Tween 60 and OP-10 in a mass ratio of 71:15:14, and the hydrophilic-lipophilic balance (HLB) of the system is adjusted to 5.6.

[0038] The third step involves adding the oil phase to a reactor equipped with a stirrer, thermometer, and nitrogen inlet pipe. Under nitrogen protection, the mixture is stirred at 500 r / min. The aqueous phase obtained in the first step is then slowly added dropwise to the oil phase at a rate of one-tenth of a part by weight per hour. After the addition is complete, stirring continues for 30 minutes to form a stable water-in-oil (W / O) preemulsion. The volume ratio of the oil phase to the aqueous phase is 1:1.

[0039] Fourth step: Add an initiator accounting for 0.2% of the total mass of monomers to the pre-emulsion, and stir the reaction at 60°C for 2 hours. The initiator is analytical grade 2,2'-azobis(2-methylpropanediamine) dihydrochloride.

[0040] The fifth step is to cool the product to room temperature after the reaction is complete, thus obtaining the LU-FLR emulsion product, which is an in-situ emulsifiable drilling fluid lubricant and filtration loss reducer.

[0041] The beneficial effects of this invention are as follows: when 3% LU-FLR is added to 4% water-based drilling fluid slurry and after hot rolling aging at 140°C for 16 hours, the API filtration loss can be as low as 9.8 mL, the HTHP (150°C / 3.5MPa) filtration loss is 28.8 mL, and the lubrication coefficient reduction rate is as high as 88.03%.

[0042] Example 3

[0043] A method for preparing an in-situ emulsifiable drilling fluid lubricant-filtration loss reducer includes the following steps:

[0044] The first step involves mixing acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and acrylamide (AM) in a reaction vessel at room temperature, adjusting the pH to 7.5 with a 20% sodium hydroxide aqueous solution to obtain an aqueous monomer mixture solution. The molar ratio of AA, AM, and AMPS is 0.4:2:0.5. AA, AM, and AMPS are chemically pure products, the water is industrial-grade deionized water, and the sodium hydroxide is an analytical grade product.

[0045] The second step involves mixing oleic acid with a compound emulsifier in another reactor at room temperature and stirring until homogeneous to obtain an oil phase. The compound emulsifier is a mixture of analytical grade Span 85, Tween 60, and OP-10 in a mass ratio of 80:10:10, and the hydrophilic-lipophilic balance (HLB) of the system is adjusted to 4.5.

[0046] The third step involves adding the oil phase to a reactor equipped with a stirrer, thermometer, and nitrogen inlet pipe. Under nitrogen protection, the mixture is stirred at 400 r / min. The aqueous phase obtained in the first step is then slowly added dropwise to the oil phase at a rate of one-fifteenth of a part by weight per hour. After the addition is complete, stirring continues for 20 minutes to form a stable water-in-oil (W / O) preemulsion. The volume ratio of the oil phase to the aqueous phase is 1:2.

[0047] Fourth step: Add an initiator accounting for 0.5% of the total mass of monomers to the pre-emulsion, and stir the reaction at 50°C for 5 hours. The initiator is chemically pure 2,2'-azobis(2-methylpropanediamine) dihydrochloride.

[0048] The fifth step is to cool the product to room temperature after the reaction is complete, thus obtaining the LU-FLR emulsion product, which is an in-situ emulsifiable drilling fluid lubricant and filtration loss reducer.

[0049] The beneficial effects of this invention are as follows: when 3% LU-FLR is added to 4% water-based drilling fluid slurry and after hot rolling aging at 140℃ for 16 hours, the API filtration loss can be as low as 10.6 mL, the HTHP (160℃ / 3.5MPa) filtration loss is 32.6 mL, and the lubrication coefficient reduction rate is as high as 83.66%.

[0050] Example 4

[0051] A method for preparing an in-situ emulsifiable drilling fluid lubricant-filtration loss reducer includes the following steps:

[0052] The first step involves mixing acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and acrylamide (AM) in a reaction vessel at room temperature. The pH is then adjusted to 6.8 using a 10-20% sodium hydroxide aqueous solution to obtain an aqueous monomer mixture solution. The molar ratio of AA, AM, and AMPS is 1.2:2.5:0.6. AA, AM, and AMPS are chemically pure products, the water is industrial-grade deionized water, and the sodium hydroxide is an industrial-purity product.

[0053] The second step involves mixing oleic acid with a compound emulsifier in another reactor at room temperature and stirring until homogeneous to obtain an oil phase. The compound emulsifier is a mixture of analytical grade Span 85, Tween 80, and OP-10 in a mass ratio of 79:10.5:10.5, and the hydrophilic-lipophilic balance (HLB) of the system is adjusted to 4.5.

[0054] The third step involves adding the oil phase to a reactor equipped with a stirrer, thermometer, and nitrogen inlet pipe. Under nitrogen protection, the mixture is stirred at 550 r / min. The aqueous phase obtained in the first step is then slowly added dropwise to the oil phase at a rate of one-eighteenth of a part by weight per hour. After the addition is complete, stirring continues for 35 minutes to form a stable water-in-oil (W / O) preemulsion. The volume ratio of the oil phase to the aqueous phase is 1:1.

[0055] Fourth step: Add an initiator accounting for 0.8% of the total mass of monomers to the pre-emulsion, and stir the reaction at 60°C for 6 hours. The initiator is analytical grade 2,2'-azobis(2-methylpropanediamine) dihydrochloride.

[0056] The fifth step is to cool the product to room temperature after the reaction is complete, thus obtaining the LU-FLR emulsion product, which is an in-situ emulsifiable drilling fluid lubricant and filtration loss reducer.

[0057] The beneficial effects of this invention are as follows: when 3% LU-FLR is added to 4% water-based drilling fluid slurry and after hot rolling aging at 160°C for 16 hours, the API filtration loss can be as low as 11.2 mL, the HTHP (160°C / 3.5MPa) filtration loss is 36.4 mL, and the lubrication coefficient reduction rate is as high as 83.97%.

[0058] Example 5

[0059] A method for preparing an in-situ emulsifiable drilling fluid lubricant-filtration loss reducer includes the following steps:

[0060] The first step involves mixing acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and acrylamide (AM) in a reaction vessel at room temperature, adjusting the pH to 7 with a 10-20% sodium hydroxide aqueous solution to obtain an aqueous monomer mixture solution. The molar ratio of AA, AM, and AMPS is 1:1.8:0.6. AA, AM, and AMPS are industrial-grade pure products, the water is industrial-grade deionized water, and the sodium hydroxide is an analytical-grade product.

[0061] The second step involves mixing oleic acid with a compound emulsifier in another reactor at room temperature and stirring until homogeneous to obtain an oil phase. The compound emulsifier is a mixture of analytical grade Span 85, Tween 20, and OP-10 in a mass ratio of 85:7.5:7.5, and the hydrophilic-lipophilic balance (HLB) of the system is adjusted to 3.8.

[0062] The third step involves adding the oil phase to a reactor equipped with a stirrer, thermometer, and nitrogen inlet pipe. Under nitrogen protection, the mixture is stirred at 480 r / min. The aqueous phase obtained in the first step is then slowly added dropwise to the oil phase at a rate of one-twentieth by weight per hour. After the addition is complete, stirring continues for 25 minutes to form a stable water-in-oil (W / O) preemulsion. The volume ratio of the oil phase to the aqueous phase is 1:1.

[0063] Fourth step: Add an initiator accounting for 0.4% of the total mass of monomers to the pre-emulsion, and stir the reaction at 55°C for 5 hours. The initiator is analytical grade 2,2'-azobis(2-methylpropanediamine) dihydrochloride.

[0064] The fifth step is to cool the product to room temperature after the reaction is complete, thus obtaining the LU-FLR emulsion product, which is an in-situ emulsifiable drilling fluid lubricant and filtration loss reducer.

[0065] The beneficial effects of this invention are as follows: when 3% LU-FLR is added to 4% water-based drilling fluid slurry and after hot rolling aging at 180°C for 16 hours, the API filtration loss can be as low as 12.2 mL, the HTHP (170°C / 3.5MPa) filtration loss is 43.5 mL, and the lubrication coefficient reduction rate is as high as 82.98%.

[0066] Example 6

[0067] A method for preparing an in-situ emulsifiable drilling fluid lubricant-filtration loss reducer includes the following steps:

[0068] The first step involves mixing acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and acrylamide (AM) in a reaction vessel at room temperature, adjusting the pH to 7.2 with a 14% sodium hydroxide aqueous solution to obtain an aqueous monomer mixture solution. The molar ratio of AA, AM, and AMPS is 0.6:1:0.5. AA, AM, and AMPS are chemically pure products, the water is industrial-grade deionized water, and the sodium hydroxide is a chemically pure product.

[0069] The second step involves mixing oleic acid with a compound emulsifier in another reactor at room temperature and stirring until homogeneous to obtain an oil phase. The compound emulsifier is a mixture of analytical grade Span 85, Tween 20 and OP-10 in a mass ratio of 72:14:14, and the hydrophilic-lipophilic balance (HLB) of the system is adjusted to 5.6.

[0070] The third step involves adding the oil phase to a reactor equipped with a stirrer, thermometer, and nitrogen inlet pipe. Under nitrogen protection, the mixture is stirred at 600 r / min. The aqueous phase obtained in the first step is then slowly added dropwise to the oil phase at a rate of 1 / 13 by weight per hour. After the addition is complete, stirring continues for 30 minutes to form a stable water-in-oil (W / O) preemulsion. The volume ratio of the oil phase to the aqueous phase is 1:1.7.

[0071] Fourth step: Add an initiator accounting for 0.6% of the total mass of monomers to the pre-emulsion, and stir the reaction at 60°C for 3 hours. The initiator is industrially pure 2,2'-azobis(2-methylpropanediamine) dihydrochloride.

[0072] The fifth step is to cool the product to room temperature after the reaction is complete, thus obtaining the LU-FLR emulsion product, which is an in-situ emulsifiable drilling fluid lubricant and filtration loss reducer.

[0073] The beneficial effects of this invention are as follows: when 3% LU-FLR is added to 4% water-based drilling fluid slurry and after hot rolling aging at 180°C for 16 hours, the API filtration loss can be as low as 13mL, the HTHP (180°C / 3.5MPa) filtration loss is 58.3mL, and the lubrication coefficient reduction rate is as high as 81.29%.

[0074] Table 1 shows the performance evaluation results of the product from Example 1 when used as a drilling fluid. The evaluation method followed GB / T 16783.1-2014. (Evaluation results of the performance of LU-FLR in water-based drilling fluid in Example 1)

[0075] Table 2 compares the effects of the emulsifiers in all embodiments, showing the formation of water-in-oil and oil-in-water emulsions under different conditions.

[0076]

[0077]

Claims

1. A lubricant-filtration loss reducer for drilling fluids that can be emulsified in situ, characterized in that... include: Acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, 10-20% sodium hydroxide aqueous solution, compound emulsifier, initiator.

2. The in-situ emulsifiable drilling fluid lubricant-filtration loss reducer according to claim 1, characterized in that: The acrylic acid, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid are industrial grade or higher purity products, the water is industrial grade deionized water, and the sodium hydroxide is an industrial grade or higher purity product.

3. The in-situ emulsifiable drilling fluid lubricant-filtration loss reducer according to claim 1, characterized in that: The compound emulsifier is a mixture of industrial-grade or higher purity nonionic polyether surfactants and polyol ester nonionic surfactants.

4. The in-situ emulsifiable drilling fluid lubricant-filtration loss reducer according to claim 1, characterized in that: The initiator is an industrial grade or higher purity ammonium persulfate / sodium bisulfite, potassium persulfate / sodium bisulfite, azobisisobutyramidine hydrochloride, or azobisisobutyronitrile.

5. The in-situ emulsifiable drilling fluid lubricant-filtration loss reducer according to any one of claims 1-4, characterized in that... It is prepared by the following method: The first step involves mixing acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and acrylamide (AM) in a reaction vessel at room temperature. The pH is then adjusted to 6.5-7.5 using a 10-20% sodium hydroxide aqueous solution to obtain an aqueous monomer mixture solution. The molar ratio of AA, AM, and AMPS is (0.4~1.2):(1.5~2.5):(0.3~0.6). The AA, AM, and AMPS are industrial-grade or higher purity products, the water is industrial-grade deionized water, and the sodium hydroxide is an industrial-grade or higher purity product. The second step involves mixing oleic acid with a compound emulsifier in another reactor at room temperature and stirring until homogeneous to obtain an oil phase. The compound emulsifier is a mixture of industrial-grade or higher purity nonionic polyether surfactants and polyol ester nonionic surfactants, and the hydrophilic-lipophilic balance (HLB) of the system is adjusted to 3.8-5.

6. The third step involves adding the oil phase to a reactor equipped with a stirrer, thermometer, and nitrogen inlet pipe. Under nitrogen protection, the mixture is stirred at 400-600 r / min. The aqueous phase obtained in the first step is then slowly added dropwise to the oil phase at a rate of one-tenth to one-twentieth of its weight per hour. After the addition is complete, stirring continues for 20-40 minutes to form a stable water-in-oil (W / O) preemulsion. The volume ratio of the oil phase to the aqueous phase is 1:(1-2). The fourth step involves adding an initiator accounting for 0.2% to 0.8% of the total monomer mass to the pre-emulsion and stirring the mixture at 50 to 60°C for 2 to 6 hours. The initiator is an industrial grade or higher purity ammonium persulfate / sodium bisulfite, potassium persulfate / sodium bisulfite, azobisisobutyramidine hydrochloride, or azobisisobutyronitrile. The fifth step is to cool the product to room temperature after the reaction is complete, thus obtaining the LU-FLR emulsion product, which is an in-situ emulsifiable drilling fluid lubricant and filtration loss reducer.

6. The method for preparing the in-situ emulsifiable drilling fluid lubricant-filtration loss reducing agent according to any one of claims 1-4, characterized in that... Includes the following steps: The first step involves mixing acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and acrylamide (AM) in a reaction vessel at room temperature, and then adjusting the pH to 6.5-7.5 with a 10-20% sodium hydroxide aqueous solution to obtain an aqueous monomer mixture solution; the molar ratio of AA, AM, and AMPS is (0.4~1.2):(1.5~2.5):(0.3~0.6). In the second step, oleic acid and compound emulsifier are mixed in another reactor at room temperature and stirred until homogeneous to obtain the oil phase; the hydrophilic-lipophilic balance (HLB) of the system is adjusted to 3.8~5.

6.

7. The preparation method according to claim 6, characterized in that... Further steps include the following: The third step involves adding the oil phase to a reactor equipped with a stirrer, thermometer, and nitrogen inlet pipe. Under nitrogen protection, the mixture is stirred at 400-600 r / min. The aqueous phase obtained in the first step is then slowly added dropwise to the oil phase at a rate of one-tenth to one-twentieth of its weight per hour. After the addition is complete, stirring continues for 20-40 minutes to form a stable water-in-oil (W / O) preemulsion. The volume ratio of the oil phase to the aqueous phase is 1:(1-2). Fourth step: Add an initiator of 0.2% to 0.8% of the total mass of monomers to the pre-emulsion, and stir the mixture at 50 to 60°C for 2 to 6 hours. The fifth step is to cool the product to room temperature after the reaction is complete, thus obtaining the LU-FLR emulsion product, which is an in-situ emulsifiable drilling fluid lubricant and filtration loss reducer.

8. The preparation method according to claim 6 or 7, characterized in that: The acrylic acid, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid are industrial grade or higher purity products; the water is industrial grade deionized water; and the sodium hydroxide is an industrial grade or higher purity product. The compound emulsifier is a mixture of industrial grade or higher purity nonionic polyether surfactants and polyol ester nonionic surfactants. The initiator is an industrial grade or higher purity ammonium persulfate / sodium bisulfite, potassium persulfate / sodium bisulfite, azobisisobutyramidine hydrochloride, or azobisisobutyronitrile.

9. The preparation method according to claim 6, characterized in that... Includes the following steps: The first step involves mixing acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and acrylamide (AM) in a reaction vessel at room temperature. The pH is then adjusted to 6.5-7.5 using a 10-20% sodium hydroxide aqueous solution to obtain an aqueous monomer mixture solution. The molar ratio of AA, AM, and AMPS is (0.4~1.2):(1.5~2.5):(0.3~0.6). The AA, AM, and AMPS are industrial-grade or higher purity products, the water is industrial-grade deionized water, and the sodium hydroxide is an industrial-grade or higher purity product. The second step involves mixing oleic acid with a compound emulsifier in another reactor at room temperature and stirring until homogeneous to obtain an oil phase. The compound emulsifier is a mixture of industrial-grade or higher purity nonionic polyether surfactants and polyol ester nonionic surfactants, and the hydrophilic-lipophilic balance (HLB) of the system is adjusted to 3.8-5.

6. The third step involves adding the oil phase to a reactor equipped with a stirrer, thermometer, and nitrogen inlet pipe. Under nitrogen protection, the mixture is stirred at 400-600 r / min. The aqueous phase obtained in the first step is then slowly added dropwise to the oil phase at a rate of one-tenth to one-twentieth of its weight per hour. After the addition is complete, stirring continues for 20-40 minutes to form a stable water-in-oil (W / O) preemulsion. The volume ratio of the oil phase to the aqueous phase is 1:(1-2). The fourth step involves adding an initiator accounting for 0.2% to 0.8% of the total monomer mass to the pre-emulsion and stirring the mixture at 50 to 60°C for 2 to 6 hours. The initiator is an industrial grade or higher purity ammonium persulfate / sodium bisulfite, potassium persulfate / sodium bisulfite, azobisisobutyramidine hydrochloride, or azobisisobutyronitrile. The fifth step is to cool the product to room temperature after the reaction is complete, thus obtaining the LU-FLR emulsion product, which is an in-situ emulsifiable drilling fluid lubricant and filtration loss reducer.

10. Use of the in-situ emulsifiable drilling fluid lubricant-filtration loss reducer according to any one of claims 1-4 in the petrochemical field.

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