Viscosity reducer for oil-based drilling fluid, composition for preparing viscosity reducer and preparation method of viscosity reducer

Abstract

The invention relates to the field of well drilling, and discloses a viscosity reducer for oil-based drilling fluid, a composition for preparing the viscosity reducer and a preparation method of the viscosity reducer. The composition is prepared from the following components in parts by weight: 30 to 40 parts of alkylamine with 10 to 20 carbon atoms, 1 to 2 parts of maleic anhydride, 0.5 to 1 part of acrylic acid and 58 to 69 parts of an oil solvent. The viscosity reducer disclosed by the invention contains excessive alkylamine, and can be adsorbed on the surface of drilling cuttings, so that a solid phase is changed from hydrophilicity to lipophilicity, and the friction resistance of the solid phase in oil-based drilling fluid is weakened; alkylamine has a single molecular structure, so that the rheological property of the drilling fluid cannot become poor due to space crosslinking; alkylamine reacts with maleic anhydride to generate long-chain amide, alkylamine reacts with acrylic acid to generate short-chain amide, and compared with fatty acid amide for conventional oil-based drilling fluid, the long-chain amide and the short-chain amide generated in the viscosity reducer have a synergistic effect to effectively reduce the structural force of the drilling fluid and reduce the viscosity of the drilling fluid.

Description

Technical Field

[0001] This invention relates to the field of drilling technology, and more specifically to a viscosity reducer for oil-based drilling fluids, a composition for preparing the same, and a method for preparing the same. Background Technology

[0002] During drilling, emulsifiers and wetting agents interact with part of the solid phase, causing a polarity reversal on the solid phase surface, resulting in oleophilic colloidal particles that disperse in the oil phase, forming a spatial network structure. This leads to decreased drilling fluid fluidity, increased circulating pressure loss, and a higher risk of lost circulation. Commercially available crude oil viscosity reducers often have poor compatibility with oil-based drilling fluids; some products, when added, actually increase viscosity instead of reducing it. Other viscosity reducers can cause demulsification in oil-based drilling fluids, drastically reducing their electrical stability and increasing the risk of wellbore instability in shale formations. Currently, the primary method used in the field is fresh drilling fluid dilution to reduce drilling fluid viscosity, resulting in an increase in the total volume of oil-based drilling fluid and higher exploration costs. Therefore, developing and improving oil-based drilling fluid viscosity reducers is essential for improving drilling efficiency and ensuring field safety.

[0003] Patent CN113736434A discloses a novel viscosity-reducing agent for oil-based drilling fluids. This agent effectively reduces the plastic viscosity, dynamic shear force, and static shear force of oil-based drilling fluids without requiring fluid replacement, improving the rheological properties of thickened oil-based drilling fluids and preventing problems such as excessively high drilling pump pressure and pump stalling. The viscosity-reducing agent is primarily prepared by reacting hydrophilic fumed silica with unsaturated fatty acids and organic amines, followed by mixing with an oil-soluble solvent. Adding 3% by volume of the nano-viscosity-reducing agent effectively reduces static shear force by 72%, meeting field application requirements. While reducing static shear force, the apparent viscosity is reduced by 25%. The modified nano-viscosity-reducing agent maintains an 81% demulsification voltage retention rate while reducing viscosity and shear force.

[0004] Patent CN115725277A discloses a viscosity reducer for oil-based drilling fluids and its preparation method. This viscosity reducer can effectively reduce the viscosity-shear ratio of oil-based drilling fluid systems, which helps extend the service life of oil-based drilling fluids and reduce overall costs. It also helps reduce the discharge of waste slurry, waste liquid, and waste residue, thus protecting the environment. The viscosity reducer is prepared by reacting 25-40 parts of organic acid, 10-30 parts of aminophenol, 5-10 parts of epoxy monomer, and 40 parts of solvent oil at high temperature. After adding this viscosity reducer, the dynamic shear force and plastic viscosity of the oil-based drilling fluid both decrease by more than 20%, while the demulsification voltage decreases by less than 20%.

[0005] Patent CN112358857A discloses an oil-based drilling fluid viscosity reducer, comprising the following components by weight: 50-100 parts solvent oil, 5-50 parts surfactant, 1-20 parts penetrant, and 1-10 parts stabilizer. This viscosity reducer can significantly reduce the viscosity and shear stress of oil-based drilling fluids, improve their fluidity, reduce circulating pump pressure, and enable the recycling of oil-based drilling fluids. It also exhibits excellent high-temperature resistance, low cost, and high economic value. However, this viscosity reducer contains toluene, which is a harmful substance and can pollute the environment. Summary of the Invention

[0006] The main objective of this invention is to provide a viscosity reducer for oil-based drilling fluids, a composition for preparing the same, and a method for preparing the same, in order to solve the problem of how to effectively reduce the viscosity of oil-based drilling fluids.

[0007] According to one aspect of the present invention, a composition for preparing a viscosity reducer for oil-based drilling fluid is provided, comprising, by weight: 30 to 40 parts of an alkylamine having 10 to 20 carbon atoms, 1 to 2 parts of maleic anhydride, 0.5 to 1 part of acrylic acid, and 58 to 69 parts of an oil solvent.

[0008] According to one embodiment of the present invention, the alkylamine is octadecylamine.

[0009] According to one embodiment of the present invention, the oil solvent is industrial white oil.

[0010] According to one embodiment of the present invention, the composition comprises, by weight, 32 to 38 parts of alkylamine, 1.2 to 1.8 parts of maleic anhydride, 0.5 to 0.8 parts of acrylic acid, and 60 to 65 parts of oil solvent.

[0011] According to another aspect of the present invention, a method for preparing a viscosity reducer for oil-based drilling fluids is provided, comprising the following steps performed sequentially: S1, an excess of alkylamine with 10-20 carbon atoms and maleic anhydride are reacted in a reaction vessel; S2, add acrylic acid to the reaction vessel to carry out the reaction; S3, add an oil solvent to the reaction vessel to obtain a viscosity reducer.

[0012] According to one embodiment of the present invention, the amount of alkylamine used is 30-40 parts by weight, the amount of maleic anhydride used is 1-2 parts, the amount of acrylic acid used is 0.5-1 parts, and the amount of oil solvent used is 58-69 parts.

[0013] According to one embodiment of the present invention, in step S1, the reaction temperature is 130-150°C and the reaction time is 2-4 hours.

[0014] According to one embodiment of the present invention, in step S2, the reaction temperature is 70-90°C and the reaction time is 2-4 hours.

[0015] According to one embodiment of the present invention, the alkylamine is octadecylamine and the oil solvent is industrial white oil.

[0016] According to another aspect of the present invention, a viscosity reducer for oil-based drilling fluid is provided, which is prepared by the preparation method according to any of the above embodiments.

[0017] In the technical solution of this invention, the viscosity reducer contains an excess of alkylamine, which can be adsorbed onto the surface of drill cuttings, causing the solid phase to change from hydrophilic to lipophilic, thereby reducing the friction of the solid phase in oil-based drilling fluid. The alkylamine has a simple molecular structure and will not produce spatial cross-linking, thus preventing a deterioration in the rheological properties of the drilling fluid. The alkylamine reacts with maleic anhydride to generate long-chain amides and reacts with acrylic acid to generate short-chain amides. Compared with the fatty acid amides used in conventional oil-based drilling fluids, the long-chain amides and short-chain amides generated in the viscosity reducer of this invention can work synergistically to effectively reduce the structural forces of the drilling fluid and reduce the viscosity of the drilling fluid. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart illustrating a method for preparing a viscosity reducer for oil-based drilling fluids according to an embodiment of the present invention is shown. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0021] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0022] This invention proposes a composition for preparing a viscosity reducer for oil-based drilling fluids, comprising, by weight: 30-40 parts of an alkylamine having 10-20 carbon atoms, 1-2 parts of maleic anhydride, 0.5-1 parts of acrylic acid, and 58-69 parts of an oil solvent.

[0023] In embodiments of the present invention, the viscosity reducer prepared from the composition contains an excess of alkylamine, which can be adsorbed onto the surface of drill cuttings, causing the solid phase to change from hydrophilic to lipophilic, thereby reducing the friction of the solid phase in oil-based drilling fluids. The alkylamine has a simple molecular structure and will not produce spatial cross-linking, thus preventing a deterioration in the rheological properties of the drilling fluid. The alkylamine reacts with maleic anhydride to generate long-chain amides and reacts with acrylic acid to generate short-chain amides. Compared with fatty acid amides used in conventional oil-based drilling fluids, the long-chain amides and short-chain amides generated in the viscosity reducer of the present invention can work synergistically to effectively reduce the structural forces of the drilling fluid, thereby reducing the viscosity of the drilling fluid.

[0024] Alkylamines can be composed of an alkyl moiety (R) and an amino group (NH2), where the alkyl moiety can be a hydrocarbon group with different carbon chain lengths. In embodiments of the present invention, the alkylamine in the composition is selected from one or more alkylamines having 10 to 20 carbon atoms, such as dodecylamine (C42-24 ... 12 H 27 N), hexadecylamine (C) 16 H 35 N), octadecylamine (C) 18 H 39 N), etiamine (C) 20 H 43 One or more of N). In one specific embodiment, the alkylamine in the composition is octadecylamine, and the octadecylamine meets the requirements of Grade I in standard HG / T 3503-1989.

[0025] Maleic anhydride, also known as maleic anhydride or dehydrated malic anhydride, is commonly abbreviated as maleic anhydride and has the chemical formula C4H2O3. The maleic anhydride molecule contains two carbonyl groups and a conjugated system, exhibiting strong reactivity. It can undergo chemical reactions with various compounds, such as addition reactions and condensation reactions. In the embodiments of this invention, the maleic anhydride meets the solid-state type I requirements of standard GB / T 3676-2020.

[0026] In some embodiments of the present invention, the acrylic acid meets the requirements for first-class acrylic type in standard GB / T 17529.1-2008 "Industrial Acrylic Acid".

[0027] The oil solvent can be any suitable hydrophobic solvent. The oil solvent can be mineral oil, a petroleum product refined from crude oil. Mineral oil mainly includes light fuel oil, heavy fuel oil, lubricating oil, cooling oil, and other mineral hydrocarbons. The oil solvent can also be industrial white oil. In a specific embodiment, the industrial white oil is No. 5 white oil, which meets the NB / SH / T 0006-2017 standard.

[0028] The inventors discovered that adding 1-2 parts maleic anhydride to 30-40 parts alkylamine achieves the best viscosity-reducing effect. Excessive maleic anhydride leads to increased cross-linking, which in turn causes an increase in the viscosity of oil-based drilling fluids; conversely, too low a maleic anhydride content results in the viscosity reducer still primarily consisting of alkylamines and oil-based agents, mainly improving drill cuttings wettability with limited improvement on oil-water interfacial friction, thus resulting in insufficient viscosity reduction.

[0029] The inventors discovered that adding 0.5 to 1 part acrylic acid, relative to 30 to 40 parts alkylamine, achieves the best viscosity-reducing effect. In the embodiments of this invention, acrylic acid is mainly used to react with excess alkylamine, preventing excessive alkylamine from causing increased filtration loss in subsequent oil-based drilling fluids. Too low an acrylic acid content leads to excessive alkylamine and a lack of synergistic emulsifying and wetting effects from short-chain amides, resulting in insufficient viscosity-reducing effect. Too high an acrylic acid content causes excessive acrylic acid to react with the alkali in the oil-based drilling fluid, resulting in a decrease in the overall base number.

[0030] The inventors discovered that controlling the weight percentage of oil-based solvents to 58-69 parts yields the best results. Excessive oil-based solvent content leads to too low an effective concentration, failing to achieve the desired viscosity-reducing effect; conversely, insufficient oil-based solvent content results in excessively high overall viscosity of the viscosity reducer, poor dispersibility and flowability, and compromised efficacy.

[0031] In embodiments of the present invention, the weight parts of the alkylamine can be 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, or 40 parts, or any other value between any two adjacent values. The weight parts of maleic anhydride can be 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, or 2 parts, or any other value between any two adjacent values. The weight parts of acrylic acid can be 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, or 1 part, or any other value between any two adjacent values. The weight parts of the oil solvent can be 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, or 69 parts, or any other value between any two adjacent values.

[0032] In some embodiments, the composition comprises, by weight, 32 to 38 parts of alkylamine, 1.2 to 1.8 parts of maleic anhydride, 0.5 to 0.8 parts of acrylic acid, and 60 to 65 parts of oil solvent.

[0033] refer to Figure 1 The present invention also proposes a method for preparing a viscosity reducer for oil-based drilling fluids, comprising the following steps performed sequentially: S1, an excess of alkylamine with 10 to 20 carbon atoms and maleic anhydride are reacted in a reaction vessel (e.g., a four-necked flask) under stirring conditions, so that the alkylamine and maleic anhydride react to form a long-chain amide. S2, add acrylic acid to the reaction vessel and react under stirring conditions, so that the acrylic acid reacts with the unreacted alkylamine in step S1 to generate short-chain amide; S3, add an oil solvent to the reaction vessel for dilution to obtain a viscosity reducer.

[0034] In some embodiments, the amount of alkylamine used is 30-40 parts by weight, the amount of maleic anhydride used is 1-2 parts, the amount of acrylic acid used is 0.5-1 part, and the amount of oil solvent used is 58-69 parts.

[0035] In some embodiments, the alkylamine is octadecylamine, and the oil solvent is industrial white oil.

[0036] In some embodiments, in step S1, the reaction temperature is 130–150°C (e.g., 140°C), and the reaction time is 2–4 h (e.g., 3 h) to ensure that the reaction proceeds fully. Step S1 may include: first adding an alkylamine to a reaction vessel and heating it to 130–150°C, then slowly adding maleic anhydride to the reaction vessel and reacting it at 130–150°C for 2–4 h under stirring.

[0037] In some embodiments, in step S2, the reaction temperature is 70–90°C (e.g., 80°C), and the reaction time is 2–4 hours (e.g., 3 hours) to ensure the reaction proceeds fully. In step S2, the temperature can be lowered to room temperature first, and then acrylic acid can be added slowly to prevent material splashing and ensure operational safety.

[0038] In step S3, the temperature can be lowered to 30-50°C (e.g., 40°C) first, and then an oil solvent can be added under stirring conditions, followed by cooling to room temperature.

[0039] The present invention also proposes a viscosity reducer for oil-based drilling fluids, which is prepared by the preparation method according to any of the above embodiments.

[0040] The following description is based on specific embodiments and comparative examples.

[0041] Example 1 A method for preparing a viscosity reducer for oil-based drilling fluids, comprising the following steps: S1. Add 30 parts by weight of octadecylamine to a four-necked flask and heat to 140°C; S2. Slowly add 1 part by weight of maleic anhydride and react at 140°C for 3 hours with stirring; S3. Cool to room temperature, slowly add 0.5 parts by weight of acrylic acid, and react at 80°C for 3 hours with stirring; S4. Cool to 40°C, add 69 parts by weight of industrial No. 5 white oil while stirring, and cool to room temperature to obtain a viscosity reducer for oil-based drilling fluid.

[0042] Example 2 A method for preparing a viscosity reducer for oil-based drilling fluids, comprising the following steps: S1. Add 40 parts by weight of octadecylamine to a four-necked flask and heat to 140°C; S2. Slowly add 2 parts by weight of maleic anhydride and react at 140°C for 3 hours with stirring; S3. Cool to room temperature, slowly add 1 part by weight of acrylic acid, and react at 80°C for 3 hours with stirring. S4. Cool to 40°C, add 58 parts by weight of industrial No. 5 white oil while stirring, and cool to room temperature to obtain a viscosity reducer for oil-based drilling fluid.

[0043] Example 3 A method for preparing a viscosity reducer for oil-based drilling fluids, comprising the following steps: S1. Add 35 parts by weight of octadecylamine to a four-necked flask and heat to 140°C; S2. Slowly add 1.5 parts by weight of maleic anhydride and react at 140°C for 3 hours with stirring; S3. Cool to room temperature, slowly add 0.7 parts by weight of acrylic acid, and react at 80°C for 3 hours with stirring; S4. Cool to 40°C, add 63.5 parts by weight of industrial No. 5 white oil while stirring, and cool to room temperature to obtain a viscosity reducer for oil-based drilling fluid.

[0044] Comparative Example 1 A method for preparing a viscosity reducer for oil-based drilling fluids, comprising the following steps: S1. Add 30 parts by weight of octadecylamine to a four-necked flask and heat to 140°C; S2. Slowly add 5 parts by weight of maleic anhydride and react at 140°C for 3 hours with stirring; S3. Cool to room temperature, slowly add 0.5 parts by weight of acrylic acid, and react at 80°C for 3 hours with stirring; S4. Cool to 40°C, add 65 parts by weight of industrial No. 5 white oil while stirring, and cool to room temperature to obtain a viscosity reducer for oil-based drilling fluid.

[0045] Comparative Example 2 A method for preparing a viscosity reducer for oil-based drilling fluids, comprising the following steps: S1. Add 30 parts by weight of octadecylamine to a four-necked flask and heat to 140°C; S2. Slowly add 0.5 parts by weight of maleic anhydride and react at 140°C for 3 hours with stirring; S3. Cool to room temperature, slowly add 0.5 parts by weight of acrylic acid, and react at 80°C for 3 hours with stirring; S4. Cool to 40°C, add 69 parts by weight of industrial No. 5 white oil while stirring, and cool to room temperature to obtain a viscosity reducer for oil-based drilling fluid.

[0046] Comparative Example 3 A method for preparing a viscosity reducer for oil-based drilling fluids, comprising the following steps: S1. Add 30 parts by weight of octadecylamine to a four-necked flask and heat to 140°C; S2. Slowly add 1.5 parts by weight of maleic anhydride and react at 140°C for 3 hours with stirring; S3. Cool to 40°C, add 69 parts by weight of industrial No. 5 white oil while stirring, and cool to room temperature to obtain a viscosity reducer for oil-based drilling fluid.

[0047] Performance testing: The performance of the viscosity reducers for oil-based drilling fluids prepared in Examples 1-3 and Comparative Examples 1-3 was tested according to GB16783.2-2012 "Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 2: Oil-based Drilling Fluids". The evaluation method was as follows: S1. Add 210mL of No. 5 white oil, 15.0g of primary emulsifier BZ-OPE, and 12.5g of secondary emulsifier BZ-OSE to high-speed stirring, and stir at high speed for 5 minutes. S2. Add 90 mL of CaCl2 (25% concentration) aqueous solution and stir at high speed for 10 min; S3. Add 12.5g of calcium hydroxide and stir at high speed for 10 minutes. Add 6.5g of thickening agent BZ-OC and stir at high speed for 30 minutes. S4. Add 10.0g of oil-based drilling fluid filtration reducer BZ-OFL and 5g of drill cuttings from the Longmaxi Formation of Sichuan shale gas, and stir at high speed for 20 minutes. S5. Add 600g of barite and stir at high speed for 40 minutes to obtain oil-based drilling fluid; S6. Pour this oil-based drilling fluid into an aging tank and keep it at a constant temperature of 150℃ for 16 hours. S7. Remove the sample and let it reach room temperature. Add 6g of viscosity reducer and stir at high speed for 20 minutes. S8. Determine the rheological properties of the oil-based drilling fluid at 65°C after adding viscosity reducer according to the standard GB / T16783.2.

[0048] The main emulsifier, BZ-OPE, is from Bohai Drilling Engineering Co., Ltd.

[0049] The auxiliary emulsifier BZ-OSE is from Bohai Drilling Engineering Co., Ltd.

[0050] The viscosity improver BZ-OC is from Bohai Drilling Engineering Co., Ltd.

[0051] BZ-OFL, a filtration loss reducer for oil-based drilling fluids, is sourced from Bohai Drilling Engineering Co., Ltd.

[0052] The testing instruments used included a precision electronic balance (accuracy 0.01g), a ZNN-D6 six-speed rotational viscometer, a variable frequency high-speed mixer, a digital display roller furnace, and a demulsification voltage tester.

[0053] The rheological properties of the oil-based drilling fluids after adding the viscosity reducers prepared in Examples 1-3 and Comparative Examples 1-3 are shown in Table 1 below. Wherein, Φ600 represents the viscometer reading at a rotation speed of 600 r / min, and Φ3 represents the viscometer reading at a rotation speed of 3 r / min.

[0054] Table 1: Rheological property test results of Examples 1-3 and Comparative Examples 1-3

[0055] As shown in Table 1, the viscosity reducers for oil-based drilling fluids prepared in Examples 1-3 can effectively reduce the Φ600 and Φ3 values ​​of the oil-based drilling fluid, with a maximum reduction of 21.9% in Φ600 and 45.5% in Φ3. In Comparative Example 1, the excessive addition of maleic anhydride led to increased crosslinking, resulting in a slight increase in the viscosity of the oil-based drilling fluid. In Comparative Example 2, the amount of maleic anhydride added was too low; the main components were still white oil and octadecylamine, and its main effect was improving the wettability of drill cuttings, with limited improvement on the frictional force at the oil-water interface, thus resulting in a smaller viscosity reduction. Comparative Example 3 did not introduce acrylic acid, lacking the synergistic emulsifying and wetting effect of short-chain amides, thus resulting in a smaller viscosity reduction.

[0056] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A composition for preparing a viscosity reducer for oil-based drilling fluids, characterized in that, By weight, it contains: 30 to 40 parts of alkylamine with 10 to 20 carbon atoms, 1 to 2 parts of maleic anhydride, 0.5 to 1 part of acrylic acid, and 58 to 69 parts of oil solvent.

2. The composition according to claim 1, characterized in that, The alkylamine is octadecylamine.

3. The composition according to claim 1, characterized in that, The oil solvent is industrial white oil.

4. The composition according to claim 1, characterized in that, The composition comprises, by weight, 32 to 38 parts of alkylamine, 1.2 to 1.8 parts of maleic anhydride, 0.5 to 0.8 parts of acrylic acid, and 60 to 65 parts of oil solvent.

5. A method for preparing a viscosity reducer for oil-based drilling fluids, characterized in that, This includes the following steps performed sequentially: S1, an excess of alkylamine with 10-20 carbon atoms and maleic anhydride are reacted in a reaction vessel; S2, add acrylic acid to the reaction vessel to carry out the reaction; S3, add an oil solvent to the reaction vessel to obtain the viscosity reducer.

6. The method according to claim 5, characterized in that, By weight, the amount of alkylamine is 30-40 parts, the amount of maleic anhydride is 1-2 parts, the amount of acrylic acid is 0.5-1 parts, and the amount of oil solvent is 58-69 parts.

7. The method according to claim 5, characterized in that, In step S1, the reaction temperature is 130–150°C and the reaction time is 2–4 hours.

8. The method according to claim 5, characterized in that, In step S2, the reaction temperature is 70–90°C and the reaction time is 2–4 hours.

9. The method according to claim 5, characterized in that, The alkylamine is octadecylamine, and the oil solvent is industrial white oil.

10. A viscosity reducer for oil-based drilling fluids, characterized in that, It is prepared by the method according to any one of claims 5-9.

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