Cutting agents, their preparation methods and applications, and oil-based drilling fluids

Abstract

This invention relates to the fields of petroleum drilling technology and chemical technology, specifically to a cutting agent, its preparation method and application, and an oil-based drilling fluid. The cutting agent comprises: structural unit A provided by a polyfatty acid as shown in formula (I), structural unit B provided by a polyetheramine, and structural unit C provided by an alkanolamine compound; formula (I), in which R1 and R2 are each independently selected from H or Cl-C. 18 The alkyl group, m is a natural number greater than 1. The cutting agent in this invention has temperature-responsive characteristics, that is, the cutting performance of the cutting agent is different at different temperatures, and it can achieve the effect of cutting at high temperature and not thickening at low temperature; in addition, the cutting agent also has high temperature resistance.

Description

Technical Field

[0001] This invention relates to the fields of petroleum drilling technology and chemical technology, specifically to a cutting agent and its preparation method and application, and oil-based drilling fluid. Background Technology

[0002] Drilling fluid is a working fluid used in drilling. One of its essential functions is to be pumped into the wellbore by a mud pump, carrying the drilled cuttings out of the wellbore using the structural forces of the drilling fluid. Oil-based drilling fluid is a type of drilling fluid. Its material composition causes its viscosity and shear rate to decrease as the temperature rises and increase as the temperature falls. This characteristic means that when there are significant temperature differences at different locations within the wellbore, the viscosity and shear rate of oil-based drilling fluid can vary greatly.

[0003] Shear modifiers are key treatment agents for improving the shear force, regulating rheology, and enhancing the cuttings carrying capacity of oil-based drilling fluids; they are core materials for controlling the rheological properties of oil-based drilling fluids. Classified by chemical composition, flow modifiers for oil-based drilling fluids mainly include four categories: organoclay, rubber-based oil-soluble polymers, oil-soluble amides and their derivatives, and amphiphilic small-molecule or oligomers. Among these, organoclay is primarily bentonite modified with quaternary ammonium salts; rubber-based oil-soluble polymers mainly refer to high-molecular-weight olefin homopolymers or copolymers; oil-soluble amides and their derivatives mainly refer to oil-soluble polymers containing amide groups; and oligomers mainly refer to small-molecule organic compounds.

[0004] When drilling ultra-deep wells (depths greater than 8000m), the temperature at the bottom of the well often exceeds 200℃ due to the heat generated by the Earth's crust. At this temperature, the viscosity and shear of oil-based drilling fluid are very low, making it impossible to carry out the cuttings extracted from the bottom of the well in time. In this case, it is necessary to add a cuttings-lifting agent to the oil-based drilling fluid to enhance its cuttings-carrying capacity. However, in the upper part of the wellbore or at the surface, where there is no crustal influence, the temperature of the oil-based drilling fluid drops to 50-85℃, and the viscosity and shear increase. If traditional cuttings-lifting agents are added to increase the viscosity and shear of the oil-based drilling fluid to meet the cuttings-carrying capacity requirements at the bottom of the well, the viscosity and shear will also increase significantly when the surface temperature drops drastically. This will cause the fluidity of the oil-based drilling fluid to deteriorate, making mud pumping difficult or impossible, thus affecting the pumping capacity and causing a series of subsequent problems.

[0005] Currently available shearing enhancers or popular modifiers can improve the shearing performance of oil-based drilling fluids under high-temperature conditions, but they cannot simultaneously achieve properties such as non-thickening and easy pumping at low temperatures. A few reported rheological modifiers can regulate the rheological properties of drilling fluids, but they cannot improve the shear force or cutter carrying capacity of drilling fluids at high temperatures. Therefore, there is an urgent need to develop a temperature-responsive shearing enhancer that simultaneously achieves shearing performance at high temperatures and non-thickening at low temperatures. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem of excessive viscosity-shear changes in oil-based drilling fluids caused by large temperature differences in existing technologies, and to provide a shearing agent, its preparation method and application, and an oil-based drilling fluid. This shearing agent has temperature-responsive characteristics, that is, the shearing performance of the shearing agent varies with different temperatures, and can achieve the effect of shearing at high temperatures and no thickening at low temperatures; in addition, the shearing agent also has high temperature resistance, reaching up to 220 ℃.

[0007] To achieve the above objectives, a first aspect of the present invention provides a cutting agent comprising: a structural unit A provided by a polyfatty acid of formula (I), a structural unit B provided by a polyetheramine, and a structural unit C provided by an alcohol amine compound; Formula (I), In equation (I), R1 and R2 are each independently selected from H or C1-C. 18 The alkyl group, where m is a natural number greater than 1.

[0008] A second aspect of the present invention provides a method for preparing a cutting agent, the method comprising: performing a polycondensation reaction of a polyfatty acid, a polyether amine, and an alkanolamine compound under an inert atmosphere, wherein the cutting agent is the cutting agent described in the first aspect of the present invention.

[0009] A third aspect of the present invention provides the application of a cutting agent in drilling fluid, wherein the cutting agent is the cutting agent described in the first aspect of the present invention.

[0010] A fourth aspect of the present invention provides an oil-based drilling fluid, wherein the oil-based drilling fluid includes the cutting agent described in the first aspect of the present invention.

[0011] Through the above technical solution, the present invention has at least the following beneficial effects: The shearing agent in this invention is resistant to high temperatures and has strong shearing ability at high temperatures, which can compensate for the high-temperature thickening characteristics of oil-based drilling fluids; at low temperatures, it has low shearing ability, which can reduce the impact on the pumping and discharging capacity of mud pumps. Attached Figure Description

[0012] Figure 1 This is the infrared spectrum of the cutting agent in Example 1. Detailed Implementation

[0013] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0014] The present invention provides a cutting agent comprising: a structural unit A provided by a polyfatty acid of formula (I), a structural unit B provided by a polyether amine, and a structural unit C provided by an alkanolamine compound; Formula (I), In equation (I), R1 and R2 are each independently selected from H or C1-C. 18 The alkyl group, where m is a natural number greater than 1.

[0015] The shearing agent in this invention can adjust the shear force of drilling fluid in response to temperature. At the bottom-hole high temperature of 160~220℃, the shearing agent can increase the dynamic-plastic ratio of oil-based drilling fluid, which helps to carry the rock. At the wellhead temperature of 80~100℃, the viscosity-shear rise of oil-based drilling fluid is not too high. This achieves the characteristics of drilling fluid that is easy to pump at low temperature and easy to carry the rock at high temperature, thus meeting the requirements of safe and efficient drilling in ultra-deep and complex formations.

[0016] In this invention, C1-C 18 The alkyl group can be either a straight-chain alkyl group or a branched-chain alkyl group, and the present invention does not have any special limitations on this. For example, it can be methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, n-hexyl, n-heptyl, n-dodecyl, n-hexadecyl, etc. According to a preferred embodiment of the present invention, in formula (I): R1 and R2 are each independently selected from C1-C1. 10 Alkyl groups. In formula (I) of the present invention, R1 is tert-butyl and R2 is H, which is used as an example to illustrate the advantages of the present invention, but does not represent a limitation of the present invention.

[0017] The polyfatty acid in this invention can provide nonpolar fatty chains and carboxyl groups. The amide groups formed by the carboxyl groups and amine groups can form intramolecular hydrogen bonds. As the temperature changes, the formation or breaking of intramolecular hydrogen bonds will cause the polymer conformation to fold or stretch, thereby changing the viscosity of the cutting agent and realizing that the cutting agent has temperature-responsive characteristics.

[0018] According to one embodiment of the present invention, in formula (I), m is a natural number from 2 to 8, such as 2, 3, 4, 5, 6, 7, etc. Using the aforementioned method, the cutting agent can achieve temperature-responsive characteristics. In formula (I) of the present invention, m being 5 is used as an example to illustrate the advantages of the present invention, but this does not represent a limitation of the present invention.

[0019] According to one embodiment of the present invention, structural unit A and structural unit B are linked by an amide group obtained by reacting a polyfatty acid with a polyetheramine. The polyfatty acid in the present invention contains a carboxyl group, and the polyetheramine contains an amino group; structural unit A and structural unit B can be linked by an amide group generated by the reaction of the carboxyl group and the amino group.

[0020] According to one embodiment of the present invention, structural unit A and structural unit C are linked by amide groups and / or ester groups obtained by reacting polyfatty acids with alkanolamine compounds. The polyfatty acids in the present invention contain carboxyl groups, and the alkanolamine compounds contain hydroxyl and amino groups. Structural unit A and structural unit C can be linked by amide groups generated from the reaction of carboxyl and amino groups, or by ester groups generated from the reaction of carboxyl and hydroxyl groups.

[0021] According to one embodiment of the present invention, the polyetheramine has a structure as shown in formula (II): Equation (II), In formula (II), R3 and R4 are each independently selected from H or C1-C7 alkyl groups, and n is a natural number greater than 2.

[0022] In this invention, the alkyl groups of C1-C7 can be straight-chain alkyl groups or branched-chain alkyl groups. This invention does not have any special limitations on this. For example, they can be methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, n-hexyl, n-heptyl, etc. In formula (II) of this invention, R3 is methyl and R4 is methyl. This is used as an example to illustrate the advantages of this invention, but it does not represent a limitation on this invention.

[0023] The polyetheramine in this invention can provide ether bonds and amino groups. The amide group formed by the carboxyl group and the amino group and the ether bond can form intramolecular hydrogen bonds. By adjusting the number of amide groups and ether bonds, the formation or breaking of intramolecular hydrogen bonds at different temperatures can be controlled, thereby achieving the temperature-responsive properties of the cutting agent.

[0024] According to a preferred embodiment of the present invention, in formula (II): R3 and R4 are each independently selected from C1-C5 alkyl groups. Using the aforementioned method, the cutting agent can be made to have temperature-responsive properties.

[0025] According to a preferred embodiment of the present invention, in formula (II), n is a natural number from 3 to 20, for example, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19. By employing the aforementioned method, the cutting agent can achieve temperature-responsive characteristics. In formula (II) of the present invention, n is 8 as an example to illustrate the advantages of the present invention, but this does not represent a limitation of the present invention.

[0026] According to one embodiment of the present invention, the alkanolamine compound has a structure as shown in formula (III): Formula (III) In formula (III), R5 and R6 are each independently selected from C1-C4 alkylene groups. The alkanolamine compound in this invention can provide a secondary amine, and the amide group formed by the carboxyl group and the secondary amine can form an intramolecular hydrogen bond. The formation or breaking of the intramolecular hydrogen bond at different temperatures can enable the slitting agent to have temperature-responsive properties.

[0027] In this invention, the C1-C4 alkylene groups are divalent groups formed by the loss of one H from a C1-C4 alkyl group. According to a preferred embodiment of this invention, in formula (III): R5 and R6 are each independently selected from C2-C4 alkylene groups. Using the aforementioned method, the temperature-responsive properties of the cutting agent can be achieved.

[0028] According to one embodiment of the present invention, the molar ratio of structural unit A to structural unit B is 1:1-3.

[0029] According to one embodiment of the present invention, the molar ratio of structural unit A to structural unit C is 1:1-2.

[0030] As long as the objective of this invention can be achieved, the average molecular weight of the cutting agent in this invention can be selected within a wide range. According to one embodiment of this invention, the average molecular weight of the cutting agent is 5000-35000. For example, it is 5000, 10000, 15000, 19000, 22000, 26000, 27500, 30000, 32000, or 35000.

[0031] This invention provides a method for preparing a cutting agent, the method comprising: performing a polycondensation reaction of a polyfatty acid, a polyether amine, and an alkanolamine compound under an inert atmosphere, wherein the cutting agent is the cutting agent described in this invention.

[0032] In the preparation method of the present invention, the types and amounts of each component are selected and determined according to the composition of the target cutting agent.

[0033] The shearing agent prepared in this invention can withstand high temperatures and has strong adhesion and shearing ability at high temperatures, which can compensate for the high-temperature thickening characteristics of oil-based drilling fluids; it has weaker adhesion and shearing ability at low temperatures, which can reduce the impact on the pumping and discharging capacity of mud pumps.

[0034] According to the present invention, there are no special restrictions on the inert gas used to achieve the inert atmosphere, as long as the purpose of the present invention can be achieved. The inert gas in the present invention is a gas capable of achieving an inert atmosphere, that is, it does not chemically react with other chemical substances in the reaction system. Nitrogen gas is used as an example to illustrate the advantages of the present invention, but this does not represent a limitation on the present invention.

[0035] According to a specific embodiment of the present invention, the preparation method of the cutting agent includes: adding polyfatty acid, polyetheramine and alkanolamine compound to a three-necked flask equipped with a mechanical stirrer, a dehydrator and an inert gas interface; introducing an inert gas to provide an inert atmosphere before the reaction; placing the three-necked flask in an oil bath; stirring and heating to a specified temperature for a period of time; and obtaining a dark brown viscous liquid after the reaction is complete, which is the cutting agent.

[0036] As long as the purpose of this invention can be achieved, there are no special restrictions on the stirring speed. This invention uses a stirring speed of 250 r / min as an example.

[0037] In this invention, the amount of polyfatty acid, polyetheramine and alkanolamine compound added can be selected according to the content of the corresponding monomer in the slitting agent. Preferably, the molar ratio of polyfatty acid to polyetheramine is 1:1-3, and preferably the molar ratio of polyfatty acid to alkanolamine compound is 1:1-2.

[0038] As long as the purpose of this invention can be achieved, there are no special restrictions on the reaction temperature of the polycondensation reaction in this invention. According to a preferred embodiment of this invention, the conditions for the polycondensation reaction include a temperature of 50-120°C.

[0039] As long as the purpose of this invention can be achieved, there is no special limitation on the reaction time of the polycondensation reaction in this invention. It can be selected according to the corresponding reaction temperature. According to a preferred embodiment of this invention, the conditions of the polycondensation reaction include: a time of 2-5 hours.

[0040] This invention provides an application of a cutting agent in drilling fluid, wherein the cutting agent is the cutting agent described in this invention.

[0041] The cutting agent in this invention, when applied to drilling fluid, can increase the viscosity of the drilling fluid under high-temperature conditions, enhance its sand-carrying capacity, and simultaneously reduce its viscosity under low-temperature conditions, thereby achieving easy pumping performance of the drilling fluid.

[0042] According to one embodiment of the present invention, the drilling fluid is an oil-based drilling fluid.

[0043] Oil-based drilling fluids are water-in-oil emulsions, in which the aqueous phase is stably dispersed in the oil phase as small droplets encapsulated by an interfacial film. Interfacial adsorption, regulation of the emulsion droplet interfacial film, and emulsion aggregation state are key to improving the temperature resistance and fluid structure of oil-based drilling fluids. The polyfatty acid and polyetheramine in this invention are amphiphilic small-molecule oligomers characterized by rapid thermal motion, high shear sensitivity, and minimal impact on the plastic viscosity of the drilling fluid. Containing high-temperature shear-lifting agents with corresponding structural units, these agents can adsorb onto the oil-water interfacial film and interact with other emulsifiers in the oil-based drilling fluid, exhibiting the characteristic of regulating the shear stress response of the drilling fluid with temperature.

[0044] This invention provides an oil-based drilling fluid, wherein the oil-based drilling fluid includes the cutting agent described in this invention.

[0045] The oil-based drilling fluid of this invention has the advantages of low viscosity and easy pumping at low temperatures, and high viscosity and strong rock-carrying capacity at high temperatures. It realizes that the oil-based drilling fluid can take into account both high-temperature rock-carrying capacity and low-temperature pumpability, and solves the problem of difficult control of the rheological properties of oil-based drilling fluid under large temperature difference circulation conditions.

[0046] According to one embodiment of the present invention, the content of the cutting agent in the oil-based drilling fluid is 0.5-5 wt%. For example, it is 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%. In this invention, an oil-based drilling fluid with a cutting agent content of 1 wt% is used as an example to illustrate the advantages of the present invention, but this does not represent a limitation of the present invention.

[0047] The present invention will be described in detail below through embodiments. In the following embodiments and comparative examples: The structures of polyfatty acids are shown in Formula (I) and Formula (IV), and they are commercially available products of Shanghai Aladdin Biochemical Technology Co., Ltd. Formula (I); In formula (I), R1 is tert-butyl, R2 is H, and m is 5; Formula (IV); The structure of polyetheramine is shown in formula (II), and it is a commercially available product of Shanghai Aladdin Biochemical Technology Co., Ltd. Formula (II); In formula (II), R3 is methyl, R4 is methyl, and n is 8; In formula (II), R3 is methyl, R4 is methyl, and n is 2; The alcohol amine compounds (diethanolamine, salmamide) are commercially available products of Shanghai Aladdin Biochemical Technology Co., Ltd. Apparent viscosity AV, plastic viscosity PV, and dynamic shear force YP were determined according to the method in standard GB / T16783.2-2012; The dynamic shear force YP is the ratio of dynamic shear force YP to plastic viscosity PV. Φ6 refers to the reading of the fluid rotational viscometer at a shear rate of 6 revolutions / min. The rheology at room temperature and pressure is measured by a six-speed viscometer, and the rheology at high temperature and high pressure is measured by a Fan77 high temperature and high pressure rheometer. Φ3 refers to the reading of the fluid rotational viscometer at a shear rate of 3 revolutions per minute. The rheology at room temperature and pressure is measured by a six-speed viscometer, while the rheology at high temperature and high pressure is measured by a Fan77 high-temperature and high-pressure rheometer.

[0048] Example 1 Place the dry, round-bottomed three-necked flask on an iron stand, and install the mechanical stirrer, dehydrator, and nitrogen inlet. After purging with nitrogen for 10 minutes, add polyfatty acid (in formula (I), R1 is tert-butyl, R2 is H, and m is 5), polyetheramine (in formula (II), R3 is methyl, R4 is methyl, and n is 8), and diethanolamine to the three-necked flask in a molar ratio of 1:2:1. Place the three-necked flask in an oil bath and heat it to 130°C. The reaction time is 4 hours, and the stirring speed is 250 r / min. The resulting dark brown viscous liquid is the cutting agent, and the average molecular weight of the cutting agent is 30,000.

[0049] The infrared spectrum of the cutting agent in Example 1 is as follows: Figure 1 As shown, Figure 1 Middle, 3200-3300 cm -1 A broad intramolecular hydrogen bond peak is present at 1110 cm⁻¹. -1 The peak at 1643 cm⁻¹ originates from the characteristic peak of the -O- group in aliphatic amino polyether compounds. -1 A strong peak exists at 1548.42 cm⁻¹, which is the vibrational peak of the C=O basis. -1 The peak at this location is a characteristic peak of the NH group, indicating that the polyfatty acid, polyether amine, and alkanolamine compounds in the raw materials have undergone a polycondensation reaction. The spectra of the other examples are similar and will not be repeated.

[0050] Example 2 Place the dry, round-bottomed three-necked flask on an iron stand, and install the mechanical stirrer, dehydrator, and nitrogen inlet. After purging with nitrogen for 10 minutes, add polyfatty acid (in formula (I), R1 is tert-butyl, R2 is H, and m is 5), polyetheramine (in formula (II), R3 is methyl, R4 is methyl, and n is 8), and diethanolamine to the three-necked flask in a molar ratio of 1:1:1. Place the three-necked flask in an oil bath and heat it to 130°C. The reaction time is 4 hours, and the stirring speed is 250 r / min. The resulting dark brown viscous liquid is the cutting agent, and the average molecular weight of the cutting agent is 22,000.

[0051] Example 3 Place the dry, round-bottomed three-necked flask on an iron stand, and install the mechanical stirrer, dehydrator, and nitrogen inlet. After purging with nitrogen for 10 minutes, add polyfatty acid (in formula (I), R1 is tert-butyl, R2 is H, and m is 5), polyetheramine (in formula (II), R3 is methyl, R4 is methyl, and n is 8), and diethanolamine to the three-necked flask in a molar ratio of 1:2:1. Place the three-necked flask in an oil bath and heat it to 100°C. The reaction time is 2 hours, and the stirring speed is 250 r / min. The resulting dark brown viscous liquid is the cutting agent, and the average molecular weight of the cutting agent is 19,000.

[0052] Example 4 Place the dry, round-bottomed three-necked flask on an iron stand, and install the mechanical stirrer, dehydrator, and nitrogen inlet. After purging with nitrogen for 10 minutes, add polyfatty acid (in formula (I), R1 is tert-butyl, R2 is H, and m is 5), polyetheramine (in formula (II), R3 is methyl, R4 is methyl, and n is 2), and diethanolamine to the three-necked flask in a molar ratio of 1:2:1. Place the three-necked flask in an oil bath and heat it to 130°C. The reaction time is 4 hours, and the stirring speed is 250 r / min. The resulting dark brown viscous liquid is the cutting agent, and the average molecular weight of the cutting agent is 27,500.

[0053] When this cutting agent is added to oil-based drilling fluid, it can improve the viscosity-cutting ability of the oil-based drilling fluid at high temperatures. However, the effect of improving viscosity-cutting is worse than that of Examples 1, 2, and 3. In particular, under the test conditions of 220°C and 100MPa, the dynamic plasticity decreased by 16.67% compared with Example 1, and the high-temperature rock-carrying capacity was reduced.

[0054] Example 5 Place the dry, round-bottomed three-necked flask on an iron stand, and install the mechanical stirrer, dehydrator, and nitrogen inlet. After purging with nitrogen for 10 minutes, add polyfatty acid (in formula (I), R1 is tert-butyl, R2 is H, and m is 5), polyetheramine (in formula (II), R3 is methyl, R4 is methyl, and n is 8), and salmamide in a molar ratio of 1:2:1 to the three-necked flask. Place the three-necked flask in an oil bath and heat it to 130°C. The reaction time is 4 hours, and the stirring speed is 250 r / min. The resulting dark brown viscous liquid is the cutting agent, and the average molecular weight of the cutting agent is 26,000.

[0055] When this cutting agent is added to oil-based drilling fluid, it can improve the viscosity-cutting ability of the oil-based drilling fluid at high temperatures. However, the effect of improving viscosity-cutting is worse than that of Examples 1, 2, and 3. In particular, under the test conditions of 220°C and 100MPa, the dynamic plasticity decreased by 36.11% compared with Example 1, and the high-temperature rock-carrying capacity was reduced.

[0056] Example 6 Place the dry, round-bottomed three-necked flask on an iron stand, and install the mechanical stirrer, dehydrator, and nitrogen inlet. After purging with nitrogen for 10 minutes, add polyfatty acid (in formula (I), R1 is tert-butyl, R2 is H, and m is 5), polyetheramine (in formula (II), R3 is methyl, R4 is methyl, and n is 8), and diethanolamine in a molar ratio of 1:4:4 into the three-necked flask. Place the three-necked flask in an oil bath and heat it to 130°C. The reaction time is 4 hours, and the stirring speed is 250 r / min. The resulting dark brown viscous liquid is the cutting agent, and the average molecular weight of the cutting agent is 50,000.

[0057] When this cutting agent is added to oil-based drilling fluid, it can improve the viscosity-cutting ability of the oil-based drilling fluid at high temperatures. However, the effect of improving viscosity-cutting is worse than that of Examples 1, 2, and 3. In particular, under the test conditions of 220°C and 100MPa, the dynamic plasticity decreased by 16.67% compared with Example 1, and the high-temperature rock-carrying capacity was reduced.

[0058] Comparative Example 1 Place the dry, round-bottomed three-necked flask on an iron stand, and install the mechanical stirrer, dehydrator, and nitrogen inlet. After purging with nitrogen for 10 minutes, add polyfatty acid (in formula (I), R1 is tert-butyl, R2 is H, and m is 5) and diethanolamine in a molar ratio of 1:1 into the three-necked flask. Place the three-necked flask in an oil bath and heat it to 130°C. The reaction time is 4 hours, and the stirring speed is 250 r / min. The resulting dark brown viscous liquid is the cutting agent.

[0059] When this cutting agent is added to oil-based drilling fluid, it significantly increases viscosity at both high and low temperatures, but the temperature response of the viscosity-cutting effect is poor. Furthermore, the addition of this cutting agent results in a large increase in viscosity but a relatively small increase in shear force, with a dynamic-to-plastic ratio of only 0.21, which is also unfavorable for high-temperature rock carrying.

[0060] Comparative Example 2 Place the dry, round-bottomed three-necked flask on an iron stand, and install the mechanical stirrer, dehydrator, and nitrogen inlet. After purging with nitrogen for 10 minutes, add polyfatty acid (as shown in formula (IV)), polyetheramine (in formula (II), R3 is methyl, R4 is methyl, and n is 8), and diethanolamine in a molar ratio of 1:2:1 into the three-necked flask. Place the three-necked flask in an oil bath and heat it to 130°C. The reaction time is 4 hours, and the stirring speed is 250 r / min. The resulting dark brown viscous liquid is the cutting agent.

[0061] After being added and subjected to high-temperature aging at 220°C, the drilling fluid solidified upon opening the can, making further testing impossible.

[0062]

[0063] Formula (IV) Comparative Example 3 Place the dry, round-bottomed three-necked flask on an iron stand, and install the mechanical stirrer, dehydrator, and nitrogen inlet. After purging with nitrogen for 10 minutes, add polyfatty acid (in formula (I), R1 is tert-butyl, R2 is H, and m is 5) and polyetheramine (in formula (II), R3 is methyl, R4 is methyl, and n is 8) to the three-necked flask at a molar ratio of 1:2. Place the three-necked flask in an oil bath and heat it to 130°C. The reaction time is 4 hours, and the stirring speed is 250 r / min. The resulting dark brown viscous liquid is the cutting agent.

[0064] When this cutting agent is added to oil-based drilling fluid, compared with a blank sample of oil-based drilling fluid, the improvement in adhesion and cutting is not significant, and the cutting effect is poor.

[0065] Test case Prepare ten sets of 1.40g / cm 3 One group of oil-based drilling fluids served as a blank sample, while the other nine groups of oil-based drilling fluids were treated with 1 wt% of the cutting agent from Examples 1-6 and Comparative Examples 1-3, respectively. After aging at 220°C for 16 hours, the downhole environment was simulated using a Fan77 high-temperature and high-pressure rheometer. The rheological parameters of the oil-based drilling fluids were tested under the following conditions: before aging at 65°C and atmospheric pressure, after aging at 65°C and atmospheric pressure, and after aging at 220°C and 100MPa.

[0066] In all examples and comparative examples, the cutting agent was 1.40 g / cm³. 3 The performance evaluation of oil-based drilling fluids is shown in Table 1: Table 1

[0067] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A cutting agent, characterized in that, The cutting agent comprises: structural unit A provided by the polyfatty acid shown in formula (I), structural unit B provided by the polyether amine, and structural unit C provided by the alkanolamine compound; Equation (I), In equation (I), R1 and R2 are each independently selected from H or C1-C. 18 The alkyl group, where m is a natural number greater than 1.

2. The cutting agent according to claim 1, characterized in that, In formula (I): R1 and R2 are each independently selected from C1-C 10 Alkyl groups; and / or m is a natural number between 2 and 8.

3. The cutting agent according to claim 1, characterized in that, Structural unit A and structural unit B are linked by an amide group obtained by reacting polyfatty acid with polyetheramine; and / or The structural unit A and structural unit C are connected by amide and / or ester groups obtained by reacting polyfatty acids with alcohol amine compounds.

4. The cutting agent according to any one of claims 1-3, characterized in that, The polyetheramine has a structure as shown in formula (II): Equation (II), In formula (II), R3 and R4 are each independently selected from H or C1-C7 alkyl groups, and n is a natural number greater than 2.

5. The cutting agent according to claim 4, characterized in that, In formula (II): R3 and R4 are each independently selected from C1-C5 alkyl groups; and / or n is a natural number between 3 and 20.

6. The cutting agent according to any one of claims 1-3, characterized in that, The alkanolamine compound has the structure shown in formula (III): Formula (III) In formula (III), R5 and R6 are each independently selected from C1-C4 alkylene groups.

7. The cutting agent according to claim 6, characterized in that, In formula (III): R5 and R6 are each independently selected from C2-C4 alkylene groups.

8. The cutting agent according to claim 1, characterized in that, The molar ratio of structural unit A to structural unit B is 1:1-3; and / or The molar ratio of structural unit A to structural unit C is 1:1-2; and / or The average molecular weight of the cutting agent is 5000-35000.

9. A method for preparing a cutting agent, characterized in that, The method includes: Under an inert atmosphere, polyfatty acids, polyether amines, and alcohol amine compounds undergo a polycondensation reaction. Wherein, the cutting agent is the cutting agent according to any one of claims 1-8.

10. The method according to claim 9, characterized in that, The conditions for the polycondensation reaction include: a temperature of 50-120°C; and / or a time of 2-5 hours.

11. The application of a cutting agent in drilling fluid, characterized in that, The cutting agent is the cutting agent described in any one of claims 1-8.

12. The application according to claim 11, characterized in that, The drilling fluid is an oil-based drilling fluid.

13. An oil-based drilling fluid, characterized in that, The oil-based drilling fluid includes the cutting agent as described in any one of claims 1-8.

14. The oil-based drilling fluid according to claim 13, characterized in that, The oil-based drilling fluid contains 0.5-5 wt% cutting agent.

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