A solid-phase chemical cleaner for oil-based drilling fluids, its preparation method and application

Abstract

This invention provides a solid-phase chemical cleaner for oil-based drilling fluids, comprising a long-chain alkyl polyamine compound. The solid-phase chemical cleaner for oil-based drilling fluids provided by this invention exhibits high surface activity; its hydrophilic portion preferentially adsorbs onto the surface of drill cuttings, improving the oil wettability of the drill cuttings surface, thereby improving the drilling fluid flow pattern. This facilitates timely removal using high-mesh vibrating screens, reducing the conversion of coarse particles to fine particles and slowing the generation and accumulation of submicron solid phases. Furthermore, its long molecular chain and charge density provide a strong adsorption and aggregation effect on fine solid particles, causing small particles to agglomerate into larger particles, which is beneficial for removal by solids control equipment and helps improve the separation efficiency of solids control equipment. This invention also provides a method for preparing and applying the solid-phase chemical cleaner for oil-based drilling fluids.

Description

Technical Field

[0001] This invention belongs to the field of oil-based drilling fluid technology, and particularly relates to a solid-phase chemical cleaner for oil-based drilling fluids, its preparation method and application, specifically a long-chain alkyl polyamine compound type solid-phase chemical cleaner. Background Technology

[0002] Oil-based drilling fluids possess strong inhibition properties, good lubrication performance, strong anti-fouling ability, and good thermal stability. They can effectively inhibit the hydration and expansion of shale and reduce the occurrence of complex situations such as wellbore collapse and necking, and are widely used in shale gas horizontal wells. Due to the relatively high preparation and maintenance costs of oil-based drilling fluids, they are typically recycled after well completion. As much as possible, all oil-based drilling fluid is recovered and continuously recycled in subsequent wells. Hydrophilic drill cuttings generated during drilling are adsorbed onto the surface of surfactants, wetted, and agitated, becoming oleophilic and suspended in the oil-based drilling fluid. Their particle size distribution ranges from nanometers to centimeters. Generally, coarser drill cuttings can be promptly removed by solids control equipment. This portion of drill cuttings has a high content but a small specific surface area, resulting in limited surfactant adsorption loss and minimal impact on drilling fluid performance. Small drill cuttings that are not removed in time are continuously refined and dispersed in the slurry due to repeated circulation and mechanical crushing. They cannot be removed by solids control equipment. The initial content of this drill cuttings is low, but as drill cuttings continue to invade, their content will gradually increase. With the increase of drilling fluid reuse, the drill cuttings content in the oil-based drilling fluid system will eventually be too high and difficult to remove. This will not only increase the viscosity and shear stress of the drilling fluid, causing the rheological properties of the drilling fluid to deteriorate or even become unusable, but also slow down the mechanical drilling rate, reduce drilling efficiency and increase drilling costs.

[0003] Drilling fluid solids control technology primarily removes unwanted inert solids from drilling fluids through chemical and mechanical methods, while simultaneously controlling the active solids within a certain range. Unwanted solids mainly originate from drill cuttings. Currently, methods to reduce drill cuttings content in oil-based drilling fluids mainly involve removal using solids control equipment and dilution with emulsions (water-in-oil emulsions). However, while existing solids control equipment is effective at removing larger drill cuttings, it has virtually no effect on nano- or micron-sized cuttings. Furthermore, using water-in-oil emulsions for dilution increases preparation and maintenance costs, raises the total volume of drilling fluid, and significantly increases drilling fluid expenses. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a solid-phase chemical cleaner for oil-based drilling fluids, its preparation method and application. The chemical cleaner provided by this invention has a good cleaning effect on the solid phase of drilling fluids.

[0005] This invention provides a solid-phase chemical cleaner for oil-based drilling fluids, comprising:

[0006] Long-chain alkyl polyamine compounds.

[0007] Preferably, the long-chain alkyl polyamine compound has the structure of Formula I:

[0008]

[0009] In Equation I, n ranges from 1 to 4;

[0010] R is selected from alkyl groups having 10 to 20 carbon atoms.

[0011] Preferably, the R is selected from -CH2(CH2). 10 CH3,-CH2(CH2) 12 CH3 or -CH2(CH2) 14 CH3.

[0012] This invention provides a method for preparing a solid-phase chemical cleaner for oil-based drilling fluids, comprising:

[0013] Polyethylene polyamine, ethanol, and potassium carbonate were mixed to obtain a mixture;

[0014] The mixture is reacted with brominated long-chain alkanes to obtain a solid-phase chemical cleaner for oil-based drilling fluids.

[0015] Preferably, the polyethylene polyamine is selected from one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, or pentaethylenehexamine.

[0016] Preferably, the brominated long-chain alkane is selected from one or more of bromododecane, bromotetradecane, or bromohexadecane.

[0017] Preferably, the mass ratio of the polyethylene polyamine, ethanol, and potassium carbonate is (1.04–2.20):(70.93–79.42):(5.11–6.45).

[0018] The mass ratio of the polyethylene polyamine to the brominated long-chain alkane is (1.04–2.20):(15.37–21.96).

[0019] Preferably, the reaction temperature is 75–85°C; and the reaction time is 8–10 h.

[0020] Preferably, after the reaction is completed, the process further includes:

[0021] The obtained reaction product was rotary evaporated to remove ethanol, yielding an oil-based drilling fluid solid-phase chemical cleaner.

[0022] This invention provides a method for cleaning oil-based drilling fluids, comprising:

[0023] Mix oil-based drilling fluid and oil-based drilling fluid with a solid-phase chemical cleaner;

[0024] The mass of the solid-phase chemical cleaner for the oil-based drilling fluid is 0.5 to 1.5% of the mass of the oil-based drilling fluid.

[0025] The oil-based drilling fluid solid phase chemical cleaner provided by this invention has high surface activity. Its hydrophilic portion can preferentially adsorb onto the surface of drill cuttings, improving the oil wettability of the drill cuttings surface, thereby improving the drilling fluid flow pattern. This facilitates timely removal using a high-mesh vibrating screen, reducing the conversion of coarse particles into fine particles and slowing down the generation and accumulation of submicron solid phases. Moreover, it has a long molecular chain and charge density, exhibiting a strong adsorption and aggregation effect on fine solid phase particles, causing small particles to agglomerate into larger particles, which is beneficial for cleaning by solids control equipment and helps improve the separation efficiency of solids control equipment. Attached Figure Description

[0026] Figure 1 The particle size distribution of oil-based old slurry before the addition of solid-phase chemical cleaning agents is shown, with D90 being 11.30 μm;

[0027] Figure 2 The particle size distribution of the solid chemical agent prepared in Example 1 of this invention with 1% added to the oil-based slurry has a D90 of 122.38 μm. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] This invention provides a solid-phase chemical cleaner for oil-based drilling fluids, comprising:

[0030] Long-chain alkyl polyamine compounds.

[0031] In this invention, the long-chain alkyl polyamine compound preferably has the structure of Formula I:

[0032]

[0033] In Equation I, n ranges from 1 to 4;

[0034] R is selected from alkyl groups having 10 to 20 carbon atoms.

[0035] In this invention, n is preferably 1, 2, 3 or 4.

[0036] In this invention, R is preferably selected from alkyl groups having 12 to 18 carbon atoms, more preferably from alkyl groups having 14 to 16 carbon atoms, and most preferably from -CH2(CH2). 10 CH3,-CH2(CH2) 12 CH3 or -CH2(CH2) 14 CH3.

[0037] This invention provides a method for preparing a solid-phase chemical cleaner for oil-based drilling fluids, comprising:

[0038] Polyethylene polyamine, ethanol, and potassium carbonate were mixed to obtain a mixture;

[0039] The mixture is reacted with brominated long-chain alkanes to obtain a solid-phase chemical cleaner for oil-based drilling fluids.

[0040] In this invention, the polyethylene polyamine is preferably selected from one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine or pentaethylenehexamine.

[0041] In this invention, the ethanol is preferably anhydrous ethanol; the potassium carbonate is preferably anhydrous potassium carbonate.

[0042] In this invention, the preferred mass ratio of the polyethylene polyamine, ethanol and potassium carbonate is (1.04-2.20):(70.93-79.42):(5.11-6.45), more preferably (1.2-2.0):(72-78):(5.2-6.2), and most preferably (1.4-1.6):(74-76):(5.6-6.0).

[0043] In this invention, the mixing is preferably carried out in a four-necked flask equipped with a stirrer, thermometer, reflux condenser and dropping funnel; the mixing is preferably carried out under stirring conditions; the stirring time is preferably 15 to 30 minutes, more preferably 20 to 25 minutes.

[0044] In this invention, the brominated long-chain alkane is preferably selected from one or more of bromododecane, bromotetradecane, or bromohexadecane.

[0045] In this invention, the mass ratio of the polyethylene polyamine to the brominated long-chain alkane is preferably (1.04-2.20):(15.37-21.96), more preferably (1.2-2.0):(16-20), and most preferably (1.4-1.6):(17-18).

[0046] In this invention, the brominated long-chain alkane is preferably added dropwise to the mixture using a dropping funnel for reaction; the dropping rate is preferably 20-30 drops / min, more preferably 22-28 drops / min, and most preferably 24-26 drops / min.

[0047] In this invention, the reaction temperature is preferably 75-85°C, more preferably 78-82°C, and most preferably 80°C; the reaction time is preferably 8-10 hours, and more preferably 9 hours.

[0048] In this invention, after the reaction is completed, it preferably further includes:

[0049] The obtained reaction product was rotary evaporated to remove ethanol, yielding an oil-based drilling fluid solid-phase chemical cleaner.

[0050] In this invention, the rotary evaporation is preferably carried out in a rotary evaporator, and the rotary evaporation is preferably sealed and depressurized to 400-600 mmHg, more preferably 450-550 mmHg, and most preferably 500 mmHg; the temperature for removing ethanol is preferably 55-65°C, more preferably 60°C.

[0051] In embodiments of the present invention, the method for preparing the solid-phase chemical cleaner for oil-based drilling fluid preferably includes:

[0052] Weigh 1.04–2.20 parts of polyethylene polyamine, 70.93–79.42 parts of anhydrous ethanol, and 5.11–6.45 parts of anhydrous potassium carbonate into a four-necked flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel, and stir for 15–30 minutes.

[0053] Heat the mixture to 75–85°C and, while stirring, add 15.37–21.96 parts of bromo-containing long-chain alkanes dropwise into the flask using a dropping funnel at a rate of 20–30 drops / min. Continue the reaction at a constant temperature for 8–10 hours.

[0054] The above product was placed in a rotary evaporator, sealed and depressurized to 400-600 mmHg, and ethanol was removed at 55-65°C to obtain an oil-based drilling fluid solid-phase chemical cleaner.

[0055] This invention provides a method for cleaning oil-based drilling fluids, comprising:

[0056] Mix oil-based drilling fluid and oil-based drilling fluid with a solid-phase chemical cleaner;

[0057] The mass of the solid-phase chemical cleaner for the oil-based drilling fluid is 0.5 to 1.5% of the mass of the oil-based drilling fluid;

[0058] The solid-phase chemical cleaner for oil-based drilling fluids is the same as the solid-phase chemical cleaner for oil-based drilling fluids described in the above technical solution.

[0059] In this invention, the mass of the solid chemical cleaner for oil-based drilling fluid is preferably 0.8 to 1.2% of the mass of the oil-based drilling fluid, and most preferably 1%.

[0060] In this invention, the mixture preferably further includes:

[0061] The resulting mixture was centrifuged to obtain the supernatant liquid.

[0062] In this invention, the centrifugal separation speed is preferably 2500-3500 rpm, more preferably 2800-3200 rpm, and most preferably 3000 rpm; the centrifugal separation time is preferably 20-40 min, more preferably 25-35 min, and most preferably 30 min.

[0063] In this invention, the density of the oil-based drilling fluid is preferably 1.3–2.4 g / cm³. 3 More preferably, it is 1.5–2.0 g / cm³. 3 Examples include well slurry from the Jiaoye block, well slurry from the Luzhou block, and recycled high-density oil-based old slurry from the Weiyuan block.

[0064] The oil-based drilling fluid solid phase chemical cleaner provided by this invention has a simple synthesis process, excellent removal effect on nano- and micron-sized inferior solid phases, and can reduce the plastic viscosity of oil-based drilling fluids without significantly affecting the shear stress of the drilling fluid or its suspension stability. It can be used while drilling or as a pretreatment for high-density oil-based slurries, effectively purifying inferior solid phases. When used while drilling, a 1% addition can reduce the plastic viscosity of the field slurry by 17.24% and remove inferior solid phases by 31.5%, without affecting the suspension stability of the drilling fluid. When used as a pretreatment for high-density oil-based slurries, a 1% addition can reduce the plastic viscosity by 30.6% and remove inferior solid phases by 50%, while also improving the emulsion stability of the drilling fluid and reducing high-temperature, high-pressure filtration loss.

[0065] Example 1

[0066] 2.38 g of pentaethylenehexamine (10 mM), 100 mL of ethanol, and 6.91 g of anhydrous potassium carbonate (50 mM) were placed in a 250 mL four-necked flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel. The mixture was stirred for 15 min and heated to 85 °C. 19.94 g of bromododecane (80 mM) was added dropwise to the flask through the dropping funnel at a rate of 20–30 drops / min. After reacting at a constant temperature for 10 h, the ethanol was removed by rotary evaporation, yielding a yellow viscous liquid, which is a solid-phase chemical cleaner for oil-based drilling fluids.

[0067] Nuclear magnetic resonance (NMR) analysis was performed on the oil-based drilling fluid solid-phase chemical cleaner prepared in Example 1 of this invention: 10 mg of the sample was dissolved in deuterated water and then added to an NMR tube. NMR spectroscopy was performed using a Bruker 400 MHz NMR spectrometer. The results were as follows:

[0068] 1H NMR (400MHz, Deuterium Oxide) δ3.42-3.31 (t, 0.94H), 3.03-2.61 (m, 1H), 1.86-1.82 (t, 1.48H), 1.3-1.18 (s, 15.5H), 1.16-0.89 (s, 2H).

[0069] The structural formula of the oil-based drilling fluid solid-phase chemical cleaner prepared in Example 1 of this invention is as follows:

[0070]

[0071] Example 2

[0072] 1.89 g of tetraethylenepentamine (10 mM), 100 mL of ethanol, and 5.5 g of anhydrous potassium carbonate (40 mM) were placed in a 250 mL four-necked flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel. The mixture was stirred for 30 min and heated to 80 °C. 17.45 g of bromododecane (70 mM) was added dropwise to the flask through the dropping funnel at a rate of 20–30 drops / min. After reacting at a constant temperature for 9 h, the ethanol was removed by rotary evaporation to obtain a yellow viscous liquid, which is a solid-phase chemical cleaner for oil-based drilling fluids.

[0073] Example 3

[0074] 1.46 g of triethylenetetramine (10 mM), 100 mL of ethanol, and 5.5 g of anhydrous potassium carbonate (40 mM) were placed in a 250 mL four-necked flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel. The mixture was stirred for 25 min and heated to 80 °C. 16.64 g of bromotetradecane (60 mM) was added dropwise to the flask through the dropping funnel at a rate of 20–30 drops / min. After reacting at a constant temperature for 8 h, the ethanol was removed by rotary evaporation, yielding a yellow viscous liquid, which is a solid-phase chemical cleaner for oil-based drilling fluids.

[0075] Example 4

[0076] 1.03 g of diethylenetriamine (10 mM), 100 mL of ethanol, and 4.15 g of anhydrous potassium carbonate (30 mM) were placed in a 250 mL four-necked flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel. The mixture was stirred for 20 min and heated to 75 °C. 15.27 g of hexadecane bromide (50 mM) was added dropwise to the flask through the dropping funnel at a rate of 20–30 drops / min. After reacting at a constant temperature for 8 h, the ethanol was removed by rotary evaporation, yielding a yellow viscous liquid, which is a solid-phase chemical cleaner for oil-based drilling fluids.

[0077] Example 5

[0078] 2.38 g of pentaethylenehexamine (10 mM), 100 mL of ethanol, and 5.5 g of anhydrous potassium carbonate (40 mM) were placed in a 250 mL four-necked flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel. The mixture was stirred for 30 min and heated to 80 °C. 24.43 g of hexadecane bromide (80 mM) was added dropwise to the flask through the dropping funnel at a rate of 20-30 drops / min. After reacting at a constant temperature for 8 h, the ethanol was removed by rotary evaporation to obtain a yellow viscous liquid, which is a solid-phase chemical cleaner for oil-based drilling fluids.

[0079] The oil-based drilling fluid solid-phase chemical cleaner prepared in Example 5 of this invention was subjected to nuclear magnetic resonance detection according to the method of Example 1. The detection results are as follows:

[0080] 1H NMR (400MHz, Deuterium Oxide) δ3.42-3.31 (t, 1.73H), 3.03-2.61 (m, 1H), 1.86-1.82 (t, 0.66H), 1.3-1.18 (s, 30.7H), 1.16-0.89 (s, 3.41H).

[0081] The structural formula of the oil-based drilling fluid solid-phase chemical cleaner prepared in Example 5 of this invention is as follows:

[0082]

[0083] Example 6

[0084] 1.89 g tetraethylenepentamine (10 mM), 100 mL ethanol, and 6.91 g anhydrous potassium carbonate (50 mM) were placed in a 250 mL four-necked flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel. The mixture was stirred for 30 min and heated to 85 °C. 19.41 g bromotetradecane (70 mM) was added dropwise to the flask through the dropping funnel at a rate of 20-30 drops / min. After reacting at a constant temperature for 9 h, the ethanol was removed by rotary evaporation, yielding a yellow viscous liquid, which is a solid-phase chemical cleaner for oil-based drilling fluids.

[0085] Performance testing

[0086] The solid-phase chemical cleaning agents prepared in Examples 1-6 were respectively added to the well slurry (density 1.32 g / cm³) in the Jiaoye block. 3 ), Luzhou block well mud (density 2.05 g / cm³) 3 The well mud, and the high-density oil-based old mud (density 2.32 g / cm³) recovered from the Weiyuan block. 3In the test, its rheological properties were measured. After the test, the fluid was centrifuged at 3000 rpm for 30 min and the density of the upper liquid and the solid content were measured (the rheological properties and solid content of drilling fluid were measured in accordance with GB / T 16783.2-2012 "Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 2: Oil-based Drilling Fluids"). The results are shown in Table 1. It can be seen that adding solid phase chemical cleaners to the drilling mud preferentially adsorbs onto the solid surface, improving oil wettability and reducing the plastic viscosity of the drilling fluid (plastic viscosity reduction rate between 12.50% and 17.24%). Simultaneously, its molecules possess high charge density and long alkyl chains, which can moderately aggregate nano- and micro-particles, facilitating timely removal using high-mesh vibrating screens, slowing the generation and accumulation of submicron solid phases, and improving the separation efficiency of solids control equipment. The density and solid content of the upper drilling fluid after centrifugation show that the addition of solid phase chemical cleaners can effectively separate inferior solid phases (inferior solid phase reduction rate between 6.67% and 31.5%). This solid phase chemical cleaner has no adverse effect on the emulsion stability of the drilling fluid and can be used during drilling. Furthermore, when used as a pretreatment for high-density oil-based old drilling mud, an addition of 1% can achieve a plastic viscosity reduction rate of 30.6% and an inferior solid phase removal rate of 50%, while also helping to improve the emulsion stability of the drilling fluid and reduce high-temperature, high-pressure filtration loss.

[0087] Figure 1 and Figure 2 This image shows the particle size distribution of high-density recycled slurry before and after adding 1% of the solid-phase chemical cleaner prepared according to this invention. The recycled slurry has been reused multiple times. The inferior solid phase, after repeated cutting with a drill bit, has a smaller particle size (D90) of 11.89 μm. After adding the solid-phase chemical cleaner, the D90 is 122.38 μm, indicating that the addition of the solid-phase chemical cleaner significantly agglomerates the inferior solid phase. The agglomerated inferior solid phase has a larger particle size and can be easily removed by a conventional vibrating screen. Furthermore, the agglomeration and removal of the inferior solid phase can significantly improve the rheological properties of high-density oil-based recycled slurry, thereby increasing its reuse efficiency.

[0088] Table 1. Rheological properties and changes in solid content before and after the addition of solid cleaning agent.

[0089]

[0090]

[0091]

[0092] The oil-based drilling fluid solid phase chemical cleaner provided by this invention has a simple synthesis process, excellent removal effect on nano- and micron-sized inferior solid phases, and can reduce the plastic viscosity of oil-based drilling fluids without significantly affecting the shear stress of the drilling fluid or its suspension stability. It can be used while drilling or as a pretreatment for high-density oil-based slurries, effectively purifying inferior solid phases. When used while drilling, a 1% addition can reduce the plastic viscosity of the field slurry by 17.24% and remove inferior solid phases by 31.5%, without affecting the suspension stability of the drilling fluid. When used as a pretreatment for high-density oil-based slurries, a 1% addition can reduce the plastic viscosity by 30.6% and remove inferior solid phases by 50%, while also improving the emulsion stability of the drilling fluid and reducing high-temperature, high-pressure filtration loss.

[0093] While the invention has been described and illustrated with reference to specific embodiments thereof, such description and illustration are not intended to limit the invention. It will be readily understood by those skilled in the art that various changes may be made to suit particular circumstances, materials, compositions, substances, methods, or processes to the objectives, spirit, and scope of this application without departing from the true spirit and scope of the invention as defined by the appended claims. All such modifications are intended to be within the scope of the appended claims. Although the methods disclosed herein have been described with reference to specific operations performed in a particular order, it should be understood that these operations may be combined, subdivided, or reordered to form equivalent methods without departing from the teachings of the invention. Therefore, unless specifically indicated herein, the order and grouping of operations are not a limitation of this application.

Claims

1. A solid-phase chemical cleaner for oil-based drilling fluids, comprising: Long-chain alkyl polyamine compounds; The long-chain alkyl polyamine compound has the structure of Formula I: Equation I; In Equation I, n is 1 to 4; R is selected from alkyl groups having 10 to 20 carbon atoms.

2. The solid-phase chemical cleaner for oil-based drilling fluids according to claim 1, characterized in that, The R is selected from -CH2(CH2). 10 CH3, -CH2 (CH2) 12 CH3 or -CH2 (CH2) 14 CH3.

3. A method for preparing a solid-phase chemical cleaner for oil-based drilling fluid as described in claim 1 or 2, comprising: Polyethylene polyamine, ethanol, and potassium carbonate were mixed to obtain a mixture; The mixture is reacted with brominated long-chain alkanes to obtain a solid-phase chemical cleaner for oil-based drilling fluids.

4. The method according to claim 3, characterized in that, The polyethylene polyamine is selected from one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, or pentaethylenehexamine.

5. The method according to claim 3, characterized in that, The brominated long-chain alkanes are selected from one or more of bromododecane, bromotetradecane, or bromohexadecane.

6. The method according to claim 3, characterized in that, The mass ratio of the polyethylene polyamine, ethanol, and potassium carbonate is (1.04~2.20):(70.93~79.42):(5.11~6.45). The mass ratio of the polyethylene polyamine to the brominated long-chain alkane is (1.04~2.20):(15.37~21.96).

7. The method according to claim 3, characterized in that, The reaction temperature is 75~85℃; the reaction time is 8~10h.

8. The method according to claim 3, characterized in that, After the reaction is completed, the following also includes: The obtained reaction product was rotary evaporated to remove ethanol, yielding an oil-based drilling fluid solid-phase chemical cleaner.

9. A method for cleaning oil-based drilling fluid, comprising: Mix oil-based drilling fluid and oil-based drilling fluid with a solid-phase chemical cleaner; The solid-phase chemical cleaner for oil-based drilling fluid is the solid-phase chemical cleaner for oil-based drilling fluid as described in claim 1 or 2, or the solid-phase chemical cleaner for oil-based drilling fluid prepared by any one of claims 3 to 8. The mass of the solid chemical cleaner for the oil-based drilling fluid is 0.5 to 1.5% of the mass of the oil-based drilling fluid.

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