Flocculating agent for oil-based drilling fluid as well as preparation method and application of flocculating agent

Abstract

The invention provides a flocculating agent for oil-based drilling fluid as well as a preparation method and application of the flocculating agent. The preparation method of the flocculant for the oil-based drilling fluid comprises the following steps: adding a lipophilic monomer A into a solvent, heating to a reaction temperature, and adding an initiator a and a chain transfer agent to obtain a mixed solution I; uniformly mixing a lipophilic monomer B and a hydrophilic monomer to obtain a mixed solution II; and adding the obtained mixed solution II into the mixed solution I, then adding an initiator b, and carrying out a reaction to obtain the flocculant for the oil-based drilling fluid. According to the flocculant for the oil-based drilling fluid, the oil-soluble flocculant is synthesized on the basis of two lipophilic monomers and one hydrophilic monomer through a reversible addition-fragmentation chain transfer polymerization method, and after the oil-soluble flocculant is added into the oil-based drilling fluid, a nano-micron grade inferior solid phase can be adsorbed; therefore, the purposes of efficiently removing the nano-micron inferior solid phase and improving the repeated utilization rate of the oil-based drilling fluid are achieved.

Description

Technical Field

[0001] The invention relates to a flocculant for oil-based drilling fluid and a preparation method and application thereof, belonging to the field of oilfield chemistry in the petroleum industry. Background Art

[0002] As oil and gas exploration and development progresses toward deeper and more complex formations, drilling depths and complexity continue to increase, leading to more and more problems and demands for higher performance from drilling fluids. Oil-based drilling fluids, due to their superior temperature resistance, ability to inhibit shale hydration, significant lubrication and drag reduction, and minimal reservoir damage, have become widely used in deep, ultra-deep, horizontal, and extended-reach wells, as well as in complex formations.

[0003] Oil-based drilling fluid is a dispersed system composed of oil as the continuous phase, water as the dispersed phase, and an appropriate amount of emulsifiers, wetting agents, and weighting materials. Due to the extreme depths of ultra-deep wells, the large variations in inclination in horizontal and extended-reach wells, and the limited rock-carrying capacity of oil-based drilling, some drill cuttings cannot be promptly carried out of the wellbore during the drilling fluid circulation process. Repeated grinding of the cuttings by the drill tool within the wellbore causes a continuous increase in the amount of low-quality nano- and micron-level solids in the drilling fluid, compromising its usability. Excessive levels of nano-micron-scale inferior solids have a serious impact on the performance of oil-based drilling fluids. Excessive levels of inferior solids will reduce the drilling speed and affect the penetration rate; excessive levels of inferior solids will increase the viscosity of the drilling fluid, reduce its lubrication performance, increase the friction of the drilling fluid, and thus aggravate the wear of the drill tool; excessive levels of inferior solids will lead to poor filtration performance of the drilling fluid, and increased filtration loss under high temperature and high pressure will affect the stability of the wellbore during the drilling process; recycled oil-based drilling fluids are generally recycled by removing the inferior solids through solids control equipment and adding new drilling fluid to dilute the old slurry. However, the solids control equipment has limited ability to remove micro-nano-scale inferior solids. Excessive inferior solids have to be reused by increasing the amount of new drilling fluid added, which greatly increases the cost of use and processing.

[0004] Therefore, to reduce the content of low-quality solids in recycled oil-based drilling fluids, minimize the amount of new drilling fluid added, and lower the cost of drilling fluid use and processing, appropriate flocculants can be added. Research has found that flocculants are highly effective at flocculating solid particles in liquids. Even a small amount can significantly reduce the amount of suspended matter and colloidal contaminants in the liquid, thereby purifying the liquid. Flocculants can be generally divided into two categories based on their chemical composition: inorganic flocculants and organic flocculants. Inorganic flocculants include inorganic coagulants and inorganic polymer flocculants, while organic flocculants include organic polymer flocculants, natural organic polymer flocculants, and microbial flocculants. However, regardless of the type of flocculant, the vast majority are used for the purification and flocculation of aqueous solutions, while reports on flocculants specifically for oil solutions are relatively limited. For example, Chinese patent document CN114605582A discloses an oil-based drilling fluid flocculant formed by compounding an oil-soluble polymer with a fatty acid. The oil-soluble polymer is formed by emulsion polymerization of styrene, p-hydroxystyrene, and acrylate. While the polymer flocculant in this method can bind to solids in the drilling fluid, the resulting flocs are weak. Furthermore, the flocculant prepared by emulsion polymerization contains emulsifiers and water, which may affect the stability of the drilling fluid during subsequent use. Chinese patent document CN117164752A discloses an oil-based drilling fluid flocculant and its preparation method. The flocculant utilizes lauryl methacrylate or styrene as lipophilic monomers, trifluoroethyl methacrylate as fluorinated monomer, and dimethyldiallylammonium chloride as cationic monomer. The presence of the fluorinated monomer results in a relatively high cost for the oil-based drilling fluid flocculant, and its overall flocculation effect is relatively limited.

[0005] Therefore, in order to solve the problem that the content of micro-nano-scale inferior solid phase in oil-based drilling fluid is too high during the circulation process and the solid control equipment is difficult to remove, it is urgent to develop a flocculant for oil-based drilling fluid that can efficiently remove nano-micron-scale inferior solid phase. Summary of the Invention

[0006] To address the shortcomings of existing technologies, particularly the high content of nano- and micro-scale inferior solids in existing oil-based drilling fluids during recycling, the difficulty in removing them, the poor reusability of discarded oil-based drilling fluids, and the limited removal capacity of existing flocculants, the present invention provides a flocculant for oil-based drilling fluids, as well as its preparation method and application. The flocculant for oil-based drilling fluids of the present invention is synthesized from two lipophilic monomers and one hydrophilic monomer via a reversible addition-fragmentation chain transfer polymerization process. When added to oil-based drilling fluids, the flocculant is capable of adsorbing nano- and micro-scale inferior solids, thereby achieving the purpose of efficiently removing nano- and micro-scale inferior solids and increasing the reusability of oil-based drilling fluids.

[0007] The technical solutions of the present invention are as follows:

[0008] A method for preparing a flocculant for oil-based drilling fluid comprises the following steps:

[0009] The lipophilic monomer A is added to a solvent, heated to the reaction temperature, and an initiator a and a chain transfer agent are added to obtain a mixed solution I; the lipophilic monomer B and the hydrophilic monomer are evenly mixed to obtain a mixed solution II; the obtained mixed solution II is added to the mixed solution I, and then the initiator b is added to react to obtain a flocculant for oil-based drilling fluid.

[0010] According to the present invention, preferably, the lipophilic monomer A is one or more of lauryl methacrylate, lauryl acrylate, and octadecyl methacrylate.

[0011] According to the present invention, the solvent is preferably one or more of white oil, dimethyl sulfoxide, N,N-dimethylformamide, and toluene, and the white oil is 3# white oil, 5# white oil, 7# white oil, or 10# white oil; and the mass ratio of the solvent to the lipophilic monomer A is 3-6:1.

[0012] According to the present invention, preferably, the reaction temperature is 80-100°C.

[0013] According to the present invention, the initiator a is preferably one or a combination of two or more of ammonium persulfate, potassium persulfate, benzoyl peroxide, and azobisisobutyronitrile; the mass of the initiator a is 0.1-1% of the total mass of the lipophilic monomer A, the lipophilic monomer B, and the hydrophilic monomer.

[0014] According to the present invention, preferably, the chain transfer agent is one or more of 2-cyano-2-propyl dodecyl trithiocarbonate, 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid, and 4-cyano-4-(phenylcarbonylthio)pentanoic acid; the mass of the chain transfer agent is 0.3-0.8% of the total mass of the lipophilic monomer A, the lipophilic monomer B, and the hydrophilic monomer.

[0015] According to the present invention, preferably, the lipophilic monomer B is methyl methacrylate and / or vinyltrimethoxysilane; the molar ratio of the lipophilic monomer B to the lipophilic monomer A is 0.8-1.2:1, more preferably 1:1.

[0016] According to the present invention, preferably, the hydrophilic monomer is one or more of dimethylaminoethyl methacrylate, acrylamide, acrylic acid, and methacrylic acid; the molar ratio of the hydrophilic monomer to the lipophilic monomer A is 0.2-0.4:1, more preferably 1:3.

[0017] Preferably, according to the present invention, the mixed solution II is added dropwise to the mixed solution I, the adding time is 1-3 hours, and the adding temperature is 80-100°C.

[0018] According to the preferred embodiment of the present invention, the type and addition amount of the initiator b are the same as those of the initiator a.

[0019] According to the preferred embodiment of the present invention, the reaction time is 3-5 hours.

[0020] The present invention also provides a flocculant for oil-based drilling fluid, which is prepared by the above-mentioned preparation method.

[0021] According to the present invention, the application of the above-mentioned flocculant for oil-based drilling fluid in oil-based drilling fluid is used to adsorb nano-micron-sized inferior solid phases.

[0022] The technical features and beneficial effects of the present invention are as follows:

[0023] 1. The flocculant of the present invention utilizes the carbonyl group in its molecular structure to provide an interaction force (hydrogen bonding) with harmful solid phases. At the same time, the long carbon chains can interweave with each other to play the role of adsorption bridging, entrapping and coiling. It can efficiently adsorb nano-micron particles in oil-based drilling fluids and effectively reduce the content of inferior solid phases in drilling fluids when used in conjunction with solid control equipment.

[0024] 2. The presence of long carbon chains and hydrophilic groups in the molecular structure of the flocculant of the present invention can reduce surface tension, have a certain emulsifying effect, improve the emulsion stability of the oil-based drilling fluid, and increase the demulsification voltage.

[0025] 3. The flocculant of the present invention can significantly improve the reuse efficiency of oil-based drilling fluid and reduce the cost of use.

[0026] 4. The flocculant prepared by the RAFT polymerization method of the present invention has controllable molecular weight, narrow molecular weight distribution, and higher effective components; the flocculant prepared by the RAFT polymerization method has stable chemical properties, short reaction cycle, high yield, high flocculation efficiency, and high floc strength after flocculation. DETAILED DESCRIPTION

[0027] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] Methyl methacrylate, liquid, was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0029] Example 1

[0030] A method for preparing a flocculant for oil-based drilling fluid comprises the following steps:

[0031] (1) 8 g of lauryl methacrylate and 37 g of dimethyl sulfoxide were placed in a three-necked flask and then placed in a water bath with stirring and heating; when the temperature reached 90° C., 0.06 g of azobisisobutyronitrile and 0.06 g of 2-cyano-2-propyldodecyl trithiocarbonate were added to obtain a mixed solution I;

[0032] (2) 3 g of methyl methacrylate and 1.5 g of dimethylaminoethyl methacrylate were stirred in a beaker for 5 minutes to obtain a mixed solution II; the mixed solution II was slowly added dropwise to the three-necked flask of step (1) using a constant pressure dropping funnel at 90° C. for 2 hours; after the addition was completed, 0.06 g of azobisisobutyronitrile was added to the three-necked flask again, and the mixture was reacted at 90° C. for 4 hours; after the reaction was completed, the mixture was naturally cooled to room temperature to obtain a flocculant for oil-based drilling fluid.

[0033] Example 2

[0034] A method for preparing a flocculant for oil-based drilling fluid comprises the following steps:

[0035] (1) 10 g of octadecyl methacrylate and 41 g of 3# white oil were placed in a three-necked flask and then placed in a water bath with stirring and heating; when the temperature reached 90°C, 0.07 g of benzoyl peroxide and 0.07 g of 2-cyano-2-propyl dodecyl trithiocarbonate were added to obtain a mixed solution I;

[0036] (2) 3 g of methyl methacrylate and 0.9 g of methacrylic acid were added to a beaker and stirred for 5 minutes to obtain a mixed solution II; the mixed solution II was slowly added dropwise to the three-necked flask in step (1) using a constant pressure dropping funnel at 90° C. for 2 hours; after the addition was completed, 0.07 g of benzoyl peroxide was added to the three-necked flask again, and the mixture was reacted at 90° C. for 4 hours; after the reaction was completed, the mixture was naturally cooled to room temperature to obtain a flocculant for oil-based drilling fluid.

[0037] Example 3

[0038] A method for preparing a flocculant for oil-based drilling fluid comprises the following steps:

[0039] (1) 8 g of lauryl methacrylate and 39 g of N,N-dimethylformamide were placed in a three-necked flask and then placed in a water bath with stirring and heating; when the temperature reached 90° C., 0.07 g of ammonium persulfate and 0.07 g of 2-cyano-2-propyl dodecyl trithiocarbonate were added to obtain a mixed solution I;

[0040] (2) 4.5 g of vinyltrimethoxysilane and 0.7 g of acrylamide were added to a beaker and stirred for 5 minutes to obtain a mixed solution II; the mixed solution II was slowly added dropwise to the three-necked flask of step (1) using a constant pressure dropping funnel at 90° C. for 2 hours; after the addition was completed, 0.07 g of ammonium persulfate was added to the three-necked flask again, and the mixture was reacted at 90° C. for 4 hours; after the reaction was completed, the mixture was naturally cooled to room temperature to obtain a flocculant for oil-based drilling fluid.

[0041] Example 4

[0042] A method for preparing a flocculant for oil-based drilling fluid comprises the following steps:

[0043] (1) 7 g of lauryl acrylate and 32 g of toluene were placed in a three-necked flask and then placed in a water bath with stirring and heating; when the temperature reached 90° C., 0.05 g of potassium persulfate and 0.05 g of 2-cyano-2-propyl dodecyl trithiocarbonate were added to obtain a mixed solution I;

[0044] (2) 3 g of methyl methacrylate and 0.7 g of acrylic acid were added to a beaker and stirred for 5 minutes to obtain a mixed solution II; the mixed solution II was slowly added dropwise to the three-necked flask in step (1) at 90° C. using a constant pressure dropping funnel for 2 hours; after the addition was completed, 0.05 g of potassium persulfate was added to the three-necked flask again, and the mixture was reacted at 90° C. for 4 hours; after the reaction was completed, the mixture was naturally cooled to room temperature to obtain a flocculant for oil-based drilling fluid.

[0045] Comparative Example 1

[0046] A method for preparing a flocculant for oil-based drilling fluid is as described in Example 1, except that an equal molar amount of lauryl methacrylate is used instead of methyl methacrylate in step (2). Other conditions are the same as those in Example 1.

[0047] Comparative Example 2

[0048] A method for preparing a flocculant for oil-based drilling fluid is as described in Example 2, except that an equal molar amount of octadecyl methacrylate is used instead of methyl methacrylate in step (2). Other conditions are the same as those in Example 2.

[0049] Comparative Example 3

[0050] A method for preparing a flocculant for oil-based drilling fluid is as described in Example 1, except that an equal molar amount of methyl methacrylate is used instead of lauryl methacrylate in step (1). Other conditions are the same as those in Example 1.

[0051] Comparative Example 4

[0052] A method for preparing a flocculant for oil-based drilling fluid is as described in Example 2, except that an equal molar amount of methyl methacrylate is used instead of octadecyl methacrylate in step (1). Other conditions are the same as those in Example 2.

[0053] Comparative Example 5

[0054] A method for preparing a flocculant for oil-based drilling fluid is as described in Example 1, except that 0.02 g of 2-cyano-2-propyl dodecyl trithiocarbonate is added in step (1), and other conditions are the same as in Example 1.

[0055] Comparative Example 6

[0056] A method for preparing a flocculant for oil-based drilling fluid is as described in Example 1, except that 0.2 g of 2-cyano-2-propyl dodecyl trithiocarbonate is added in step (1), and other conditions are the same as in Example 1.

[0057] Comparative Example 7

[0058] A method for preparing a flocculant for oil-based drilling fluid is as described in Example 1, except that in step (1), an equal mass of benzyl dithiobenzoate is used instead of 2-cyano-2-propyldodecyl trithiocarbonate, and other conditions are the same as in Example 1.

[0059] Comparative Example 8

[0060] A method for preparing a flocculant for oil-based drilling fluid is as described in Example 1, except that in step (1), an equal amount of tetraethylthiuram disulfide is used instead of 2-cyano-2-propyldodecyl trithiocarbonate, and other conditions are the same as in Example 1.

[0061] Comparative Example 9

[0062] A method for preparing a flocculant for oil-based drilling fluid is as described in Example 1, except that in step (1), an equal amount of 2-(thiobenzoylthio) propionic acid is used instead of 2-cyano-2-propyl dodecyl trithiocarbonate, and other conditions are the same as in Example 1.

[0063] Comparative Example 10

[0064] A method for preparing a flocculant for oil-based drilling fluid is as described in Example 1, except that an equimolar amount of N-[2-(dimethylamino)ethyl]acrylamide is used instead of dimethylaminoethyl methacrylate in step (2). Other conditions are the same as those in Example 1.

[0065] Comparative Example 11

[0066] A method for preparing a flocculant for oil-based drilling fluid is as described in Example 1, except that 2.5 g of lauryl methacrylate is added in step (1), and other conditions are the same as in Example 1.

[0067] Comparative Example 12

[0068] A method for preparing a flocculant for oil-based drilling fluid is as described in Example 1, except that 15 g of lauryl methacrylate is added in step (1). Other conditions are the same as those in Example 1.

[0069] Comparative Example 13

[0070] A method for preparing a flocculant for oil-based drilling fluid is as described in Example 2, except that 3.4 g of octadecyl methacrylate is added in step (1), and other conditions are the same as in Example 2.

[0071] Comparative Example 14

[0072] A method for preparing a flocculant for oil-based drilling fluid is as described in Example 2, except that 20 g of octadecyl methacrylate is added in step (1), and other conditions are the same as those in Example 2.

[0073] Test Example 1

[0074] The flocculants for oil-based drilling fluids prepared in the examples and comparative examples were subjected to the following performance evaluations: flocculation and sedimentation evaluation, turbidity evaluation, and impact on drilling fluid performance.

[0075] 1. Flocculation and sedimentation evaluation

[0076] Flocculation sedimentation is one of the most intuitive and important ways to evaluate the flocculation effect. In order to intuitively evaluate the flocculation effect of flocculants, a flocculation sedimentation experiment was used to study the time it takes for the flocculant to settle to a height of 80 mm at different addition amounts.

[0077] 520 mL of white oil, 2.6 g of primary emulsifier, 2.6 g of secondary emulsifier, and 78 g of organic soil were added to the slurry cup. The mixture was stirred at 11,000 rpm for 20 minutes to ensure thorough mixing. This slurry was used as the base slurry for flocculation and sedimentation evaluation. 250 mL of base slurry and 2.5 g of flocculant were added to a stoppered measuring cylinder. The slurry was slowly poured 30 times at a rate of 2 seconds (one forward and one backward movement). The slurry was then allowed to stand while a stopwatch was started. The time it took for the sedimentation height to reach 80 mm was recorded. The results are shown in Table 1.

[0078] The white oil is No. 5 white oil from Changde Hengtong Petrochemical Additives Co., Ltd.;

[0079] The main emulsifier is MO-12, a high-temperature resistant emulsifier for drilling fluid produced by Quanzhou Lanhai Boda Technology Development Co., Ltd. in Fujian Province.

[0080] The auxiliary emulsifier is CO-12, a high-temperature resistant emulsifier for drilling fluid produced by Tianjin Xiongguan Technology Development Co., Ltd.

[0081] The organic clay is the organic bentonite thickening rheological agent BP-182 produced by Zhejiang Huamao New Materials Co., Ltd.

[0082] Table 1 Time taken for the settlement height to reach 80 mm

[0083] sample Time / s none 969 Example 1 49 Example 2 55 Example 3 62 Example 4 52 Comparative Example 1 95 Comparative Example 2 94 Comparative Example 3 103 Comparative Example 4 102 Comparative Example 5 156 Comparative Example 6 226 Comparative Example 7 323 Comparative Example 8 217 Comparative Example 9 221 Comparative Example 10 163 Comparative Example 11 103 Comparative Example 12 97 Comparative Example 13 102 Comparative Example 14 96

[0084] Table 1 shows that flocculants have a positive effect on flocculation and settling properties. For the base slurry without flocculant, the settling height did not reach 80 mm until 969 seconds. Adding the flocculant significantly improved the flocculation and settling process, reaching 80 mm within 70 seconds. In particular, the addition of the flocculant obtained in Example 1 significantly reduced the time required to reach 80 mm, demonstrating that the flocculant of the present invention can reduce flocculation time.

[0085] 2. Turbidity evaluation

[0086] A No. 5 white oil solution containing 0.2 wt% soy lecithin was prepared, and 10 wt% standard soil was added. After uniform dispersion, flocculants were added in concentrations of 0.1 wt%, 0.5 wt%, 1.0 wt%, and 1.5 wt%. The mixture was shaken evenly and allowed to settle for 15 minutes. The top 10 mL of each mixture was collected and shaken well. The supernatant was then tested for transmittance using a turbidimeter. The results are shown in Table 2.

[0087] Table 2 Transmittance of supernatant at different concentrations of flocculants

[0088]

[0089] The greater the transmittance of the supernatant, the better the flocculation effect. As can be seen from Tables 2, 3, 4, and 5, the transmittance of the supernatant of the organic soil without the addition of flocculant is 11%. When the flocculant dosage is 0.1%, 0.5%, and 1.0%, the transmittance increases, and the flocculation effect is obvious. However, as the flocculant dosage increases, the flocculation effect decreases, and the turbidity test transmittance decreases. This shows that the flocculant has a significant flocculation effect on the organic soil, and the optimal addition dosage for the prepared organic soil test solution is 1%.

[0090] 3. Evaluation in drilling fluid system

[0091] The performance of oil-based drilling fluid is measured according to the latest national standard "GB / T 16783.2-2012 Field testing of drilling fluids in the petroleum and natural gas industry Part 2: Oil-based drilling fluids".

[0092] The oil-based drilling fluid formula is: 300mL No. 5 white oil + 3g flocculant + 3g auxiliary emulsifier + 3g organic soil + 6g filtration reducer + 60g water + 15g calcium chloride + 14g calcium oxide, and then add barite to adjust the drilling fluid density to 1.5g / cm 3 .

[0093] The white oil is No. 5 white oil from Changde Hengtong Petrochemical Additives Co., Ltd.;

[0094] The auxiliary emulsifier is CO-12, a high-temperature resistant emulsifier for drilling fluid produced by Tianjin Xiongguan Technology Development Co., Ltd.

[0095] The organic clay is the organic bentonite thickening rheological agent BP-182 produced by Zhejiang Huamao New Materials Co., Ltd.

[0096] The fluid loss reducer is the oil-based drilling fluid fluid loss reducer D2532 produced by Jiujiang Lanzhuo New Materials Technology Co., Ltd.

[0097] Calcium chloride was chemically pure from Beijing Chemical Reagent Company;

[0098] The barite is barite powder produced by Dongxiang Mining Company in Hanbin District, Ankang City.

[0099] Table 3 Effect of flocculants on the properties of oil-based drilling fluids

[0100]

[0101] As shown in Table 3, compared with the oil-based drilling fluid without flocculant, the oil-based drilling fluid with 1% flocculant added has a higher demulsification voltage, indicating that its emulsion stability is better than that of the oil-based drilling fluid without flocculant. The oil-based drilling fluid with 1% flocculant added has a higher dynamic shear force and dynamic plastic ratio, indicating that its rock carrying capacity is better than that of the oil-based drilling fluid without flocculant.

[0102] 4. Evaluation after centrifugation

[0103] First, the centrifugal speed was set to 2000 rpm and the centrifugal time was set to 5 min. The density of the old pulp after centrifugation with 1% flocculant and without flocculant was compared under the same centrifugal speed and time conditions. The initial density of the old pulp was 1.41 g / cm 3 The results are shown in Table 4. Old slurry: oil-based drilling fluid that has been circulated for a period of time on an offshore drilling platform in Shenzhen waters.

[0104] Table 4 Density after centrifugation

[0105] sample <![CDATA[Density / g·cm -3 > none 1.21 Example 1 1.08 Example 2 1.09 Example 3 1.08 Example 4 1.10 Comparative Example 1 1.12 Comparative Example 2 1.11 Comparative Example 3 1.12 Comparative Example 4 1.12 Comparative Example 5 1.19 Comparative Example 6 1.20 Comparative Example 7 1.20 Comparative Example 8 1.20 Comparative Example 9 1.20 Comparative Example 10 1.19 Comparative Example 11 1.14 Comparative Example 12 1.15 Comparative Example 13 1.16 Comparative Example 14 1.17

[0106] From Table 4, we can see that the density of the old pulp reaches 1.21 g / cm after centrifugation. 3After adding 1% flocculant and treating with the same centrifugal speed and time, the lowest density of drilling fluid reached 1.08g / cm 3 The results show that the addition of flocculants has a flocculation and sedimentation effect on the inferior solid phase in the old slurry of oil-based drilling fluid, and can be separated from the old slurry by centrifugal treatment.

[0107] Flocculants can improve the performance of oil-based drilling fluids by absorbing micro- and nano-scale low-quality solids. This is because after dissolving in the drilling fluid, flocculant molecules adhere to the particle surfaces and, through constant collision, entangle with each other to form larger flocs. Once the flocs reach a certain size, they settle, allowing the drilling fluid to be separated using solids control equipment. The flocculation mechanisms of flocculants primarily encompass electrostatic neutralization, adsorption bridging, and net capture and sweeping. In actual flocculant flocculation, these mechanisms typically work synergistically to achieve flocculation.

[0108] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing a flocculant for oil-based drilling fluid, characterized in that: The steps are as follows: The lipophilic monomer A is added to a solvent, heated to the reaction temperature, and an initiator a and a chain transfer agent are added to obtain a mixed solution I; the lipophilic monomer B and the hydrophilic monomer are evenly mixed to obtain a mixed solution II; the obtained mixed solution II is added to the mixed solution I, and then the initiator b is added to react to obtain a flocculant for oil-based drilling fluid.

2. The method for preparing the flocculant for oil-based drilling fluid according to claim 1, wherein: The lipophilic monomer A is one or more of lauryl methacrylate, lauryl acrylate, and octadecyl methacrylate; the solvent is one or more of white oil, dimethyl sulfoxide, N,N-dimethylformamide, and toluene, and the white oil is 3# white oil, 5# white oil, 7# white oil, or 10# white oil; and the mass ratio of the solvent to the lipophilic monomer A is 3-6:

1.

3. The method for preparing the flocculant for oil-based drilling fluid according to claim 1, wherein: The initiator a is one or a combination of two or more of ammonium persulfate, potassium persulfate, benzoyl peroxide, and azobisisobutyronitrile; the mass of the initiator a is 0.1-1% of the total mass of the lipophilic monomer A, the lipophilic monomer B, and the hydrophilic monomer.

4. The method for preparing the flocculant for oil-based drilling fluid according to claim 1, wherein: The chain transfer agent is one or more of 2-cyano-2-propyl dodecyl trithiocarbonate, 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid, and 4-cyano-4-(phenylcarbonylthio)pentanoic acid; the mass of the chain transfer agent is 0.3-8% of the total mass of the lipophilic monomer A, the lipophilic monomer B, and the hydrophilic monomer.

5. The method for preparing the flocculant for oil-based drilling fluid according to claim 1, wherein: The lipophilic monomer B is methyl methacrylate and / or vinyltrimethoxysilane; the molar ratio of the lipophilic monomer B to the lipophilic monomer A is 0.8-1.2:1, preferably 1:

1.

6. The method for preparing the flocculant for oil-based drilling fluid according to claim 1, characterized in that: The hydrophilic monomer is one or more of dimethylaminoethyl methacrylate, acrylamide, acrylic acid, and methacrylic acid; the molar ratio of the hydrophilic monomer to the lipophilic monomer A is 0.2-0.4:1, preferably 1:

3.

7. The method for preparing the flocculant for oil-based drilling fluid according to claim 1, characterized in that: The mixed solution II is added dropwise to the mixed solution I, the addition time is 1-3 hours, and the addition temperature is 80-100° C.; the type and addition amount of the initiator b are the same as those of the initiator a.

8. The method for preparing the flocculant for oil-based drilling fluid according to claim 1, characterized in that: The reaction temperature is 80-100° C.; the reaction time is 3-5 h.

9. A flocculant for oil-based drilling fluid, characterized in that: The preparation method is described in any one of claims 1 to 8.

10. Use of the flocculant for oil-based drilling fluid according to claim 9 in oil-based drilling fluid, characterized in that: Used to adsorb nano-micron-sized inferior solid phases.

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