High-temperature-resistant viscosity improving agent for oil-based drilling fluid and preparation method of high-temperature-resistant viscosity improving agent

Abstract

The invention discloses a high-temperature-resistant tackifier for an oil-based drilling fluid and a preparation method of the high-temperature-resistant tackifier, and belongs to the technical field of drilling fluids. The high-temperature-resistant viscosity improving agent for the oil-based drilling fluid is prepared from the following raw materials in parts by weight: 7 to 14 parts of xanthan gum or modified xanthan gum, 0.5 to 2 parts of an emulsifier, 5 to 9 parts of base oil, 4 to 8 parts of 1, 2-propylene glycol and 2 to 5 parts of attapulgite, according to the invention, 2-acrylamide-2-methylpropanesulfonic acid and phenylboronic acid polymers are simultaneously adopted for modification, so that the salt resistance of xanthan gum is enhanced, the consistency of the drilling fluid is increased, the capacity of the xanthan gum for bearing solid particles is improved, the temperature resistance of the xanthan gum is improved, and the service life of the xanthan gum in a well is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of drilling fluids, and in particular to a high temperature resistant viscosity increasing agent for oil-based drilling fluids and a preparation method thereof. Background Art

[0002] In the process of exploiting low-to-medium permeability oil reservoirs, due to the low-permeability pore structure in the reservoir, solid particles are easy to block these pores, resulting in a further decrease in permeability, which increases the difficulty of exploitation and makes it more difficult to mobilize. As most of my country's oil fields have entered the middle and late stages of exploitation, they have encountered a series of technical difficulties. Petroleum workers have gradually carried out research on drilling deep wells and ultra-deep wells. The stability of high-temperature deep well drilling fluid performance is an important indicator in the process of drilling deep wells and ultra-deep wells. The selection of suitable high-temperature resistant treatment agents is the key to the high-temperature deep well drilling fluid system. In the usual drilling fluid system, clay is the basic substance for adjusting the performance of the drilling fluid, but at the same time, clay in the drilling fluid increases the submicron particles in the drilling fluid system, resulting in damage to the oil and gas reservoirs, and the mechanical drilling rate may also become lower.

[0003] Chinese invention patent CN 113372888 B discloses a method for preparing an oil-based drilling fluid and its product. The method for preparing an oil-based drilling fluid is mainly prepared by mixing the following components: a polyamine inhibitor, a cationic polyacrylamide, a low-viscosity polyanionic cellulose, xanthan gum, a lubricant, and an appropriate amount of water, wherein the final concentrations of the components in the oil-based drilling fluid are: the volume fraction of the polyamine inhibitor is 2-4%, the mass concentration of the cationic polyacrylamide is 5-10 kg / m 3 The mass concentration of the low viscosity polyanionic cellulose is 5-15 kg / m 3 The mass concentration of the xanthan gum is 1-5 kg / m 3 , the volume fraction of the lubricant is 1-3%. Although the invention solves the salt resistance and inhibition, the preparation method is simple. Although xanthan gum still has a high viscosity under high temperature and high mineralization conditions, and has a stronger shear resistance, is not easily adsorbed by reservoir rocks, and can successfully adjust the oil wetting properties in the oil layer, thereby improving the recovery rate. However, xanthan gum has a high production cost, a large amount of use, limited temperature resistance, and is prone to thermal degradation in high-temperature oil layers. Therefore, it is expected to improve its temperature resistance, reduce the amount of use, and improve salt resistance and viscosity effects by modifying xanthan gum through hydrophobic modification, branching modification, etc. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a high temperature resistant viscosity increasing agent for oil-based drilling fluid and a preparation method thereof.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A high temperature resistant viscosity enhancer for oil-based drilling fluid, characterized in that it is composed of the following raw materials: xanthan gum or modified xanthan gum, base oil, emulsifier, 1,2-propylene glycol, and attapulgite.

[0007] The high temperature resistant viscosity enhancer for oil-based drilling fluid is composed of the following raw materials in parts by weight: 7-14 parts by weight of xanthan gum or modified xanthan gum, 0.5-2 parts by weight of emulsifier, 5-9 parts by weight of base oil, 4-8 parts by weight of 1,2-propylene glycol, and 2-5 parts by weight of attapulgite.

[0008] The base oil is at least one of diesel and white oil.

[0009] The emulsifier is at least one of tall oil fatty acid, polyglycerol-3 polyricinoleate, Span 80, hexadecyl ricinoleate, and sorbitan monopalmitate.

[0010] Xanthan gum, as a water-soluble high molecular weight polysaccharide, can be used as a non-cross-linked fracturing fluid in the oilfield mining industry. It is a thickener with good thickening effect. There are still some shortcomings in the application of xanthan gum as a thickener, such as large amount required and low high temperature viscosity. Modification of xanthan gum can further improve the basic properties of xanthan gum, which can not only improve the thickening ability, temperature resistance and salt resistance of modified xanthan gum, but also effectively reduce the required amount and cost, effectively broadening the application of xanthan gum in oil-based drilling fluids.

[0011] Specifically, in S1, the xanthan gum is pretreated and treated by electron irradiation, which not only triggers a cross-linking reaction between the xanthan gum molecules to form a more stable network structure, but also enhances the mechanical properties and stability of the xanthan gum; the electron irradiation can stimulate the generation of free radicals in the reactant molecules, thereby promoting the reaction between the xanthan gum and 2-acrylamide-2-methylpropane sulfonic acid, and effectively improving the reaction yield; in S2, the pretreated xanthan gum and 2-acrylamide-2-methylpropane sulfonic acid are grafted with groups from 2-acrylamide-2-methylpropane sulfonic acid through an esterification reaction, which can thicken the double electric layer on the surface of the xanthan gum, enhance the salt resistance of the xanthan gum, increase the viscosity of the drilling fluid, thereby improving its ability to carry solid particles, and reduce the sedimentation rate of the solid particles, thereby achieving effective well wall support and cementing effects.

[0012] The preparation method of the modified xanthan gum comprises the following steps:

[0013] S1. Mix xanthan gum and water at room temperature and stir evenly to obtain pretreated xanthan gum;

[0014] S2: 2-acrylamide-2-methylpropanesulfonic acid, dimethyl sulfoxide and water are mixed and stirred to obtain a mixed solution a; all the above-mentioned pretreated xanthan gum is added to the mixed solution a for reaction to obtain modified xanthan gum.

[0015] Preferably, the preparation method of the modified xanthan gum comprises the following steps:

[0016] S1. At room temperature, 3-8 parts by weight of xanthan gum and 80-150 parts by weight of water are mixed, the pH value is adjusted to 10.5-11.5, the mixture is stirred evenly, vacuum dried, and irradiated with electrons for 10-30 minutes to obtain pretreated xanthan gum; the electron beam energy of the electron irradiation is 3-10 MeV, and the irradiation dose is 50-200 kGy;

[0017] S2: 5-8 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 80-150 parts by weight of dimethyl sulfoxide and 20-50 parts by weight of water are mixed and stirred to obtain a mixed solution a; all of the above-mentioned pretreated xanthan gum is added to the mixed solution a, reacted at 55-70° C. for 4-10 hours, and the solvent is removed by reduced pressure distillation to obtain modified xanthan gum.

[0018] Although the modified xanthan gum obtained above has good viscosity and increased salt resistance, the high temperature resistance of xanthan gum has not been well improved and is still prone to thermal degradation in high temperature oil layers. It is necessary to further modify xanthan gum to improve its temperature resistance and reduce its dosage.

[0019] In S3, acrylic acid, dimethylaminopropyl acrylamide, and 5-acrylamide-2-(aminomethyl)phenylboronic acid are used as raw materials. In the presence of diisopropyl peroxydicarbonate as an initiator and sodium formate aqueous solution as a chain transfer agent, the xanthan gum preliminarily modified in S2 is added. Acrylic acid, dimethylaminopropyl acrylamide, 5-acrylamide-2-(aminomethyl)phenylboronic acid and the double bonds in dimethylaminopropyl acrylamide and 5-acrylamide-2-(aminomethyl)phenylboronic acid modified xanthan gum undergo polymerization to obtain phenylboronic acid polymer modified xanthan gum with very high viscosity and improved heat resistance. The specific mechanism is as follows: (1) The addition of acrylic acid can form a stable complex with calcium ions, thereby effectively Control the formation of sediment in the oil-based drilling fluid to prevent the precipitation of solid particles in the drilling fluid and blockage of the wellbore; (2) The introduction of dimethylaminopropyl acrylamide can improve the temperature resistance of xanthan gum, enhance the stability of oil-based drilling fluid in high temperature environment, and extend its service life underground; (3) 5-acrylamide-2-(aminomethyl)phenylboronic acid has good anti-pollution properties, which can reduce the performance degradation of oil-based drilling fluid after contact with formation water or other pollution sources, and maintain the stability and performance of the drilling fluid; (4) The addition of 2-acrylamide 2-methylpropane sulfonic acid can increase the viscosity and consistency provided by xanthan gum, further improving the bearing capacity and wellbore support effect of oil-based drilling fluid.

[0020] The invention adopts 2-acrylamide-2-methylpropanesulfonic acid and phenylboronic acid polymer for simultaneous modification, which not only retains the salt resistance of xanthan gum and increases the viscosity of drilling fluid to improve its ability to carry solid particles, but also improves the temperature resistance of high xanthan gum and prolongs its service life underground.

[0021] Furthermore, the preparation method of the modified xanthan gum comprises the following steps:

[0022] S1. Mix xanthan gum and water at room temperature and stir evenly to obtain pretreated xanthan gum;

[0023] S2: 2-acrylamide-2-methylpropanesulfonic acid, dimethyl sulfoxide and water are mixed and stirred to obtain a mixed solution a; all the pretreated xanthan gum is added to the mixed solution a to react to obtain a preliminary modified xanthan gum;

[0024] S3, under nitrogen protection, acrylic acid, dimethylaminopropyl acrylamide, 5-acrylamide-2-(aminomethyl)phenylboronic acid, water and N-vinyl pyrrolidone are mixed, diisopropyl peroxydicarbonate, sodium formate aqueous solution and the above preliminary modified xanthan gum are added, stirred, and reacted in a water bath to obtain a crude modified xanthan gum product;

[0025] S4: washing, vacuum drying and crushing the crude modified xanthan gum to obtain modified xanthan gum.

[0026] The method for preparing the high temperature resistant viscosity enhancer for oil-based drilling fluid comprises mixing and stirring modified xanthan gum, emulsifier, base oil, 1,2-propylene glycol and attapulgite.

[0027] Furthermore, preferably, the preparation method of the modified xanthan gum comprises the following steps:

[0028] S1. At room temperature, 3-8 parts by weight of xanthan gum and 80-150 parts by weight of water are mixed, the pH value is adjusted to 10.5-11.5, the mixture is stirred evenly, vacuum dried, and irradiated with electrons for 10-30 minutes to obtain pretreated xanthan gum; the electron beam energy of the electron irradiation is 3-10 MeV, and the irradiation dose is 50-200 kGy;

[0029] S2: 5-8 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 80-150 parts by weight of dimethyl sulfoxide and 20-50 parts by weight of water are mixed and stirred to obtain a mixed solution a; all of the above-mentioned pretreated xanthan gum is added to the mixed solution a, reacted at 55-70° C. for 4-10 hours, and the solvent is removed by distillation under reduced pressure to obtain a preliminary modified xanthan gum;

[0030] S3: Under nitrogen protection, 3-8 parts by weight of acrylic acid, 2-5 parts by weight of dimethylaminopropyl acrylamide, 0.1-05 parts by weight of 5-acrylamide-2-(aminomethyl)phenylboric acid, 30-80 parts by weight of water and 40-80 parts by weight of N-vinyl pyrrolidone are mixed, 0.1-0.3 parts by weight of diisopropyl peroxydicarbonate, 0.2-0.5 parts by weight of 0.1 mol / L sodium formate aqueous solution and 3-8 parts by weight of the above-mentioned preliminary modified xanthan gum are added, stirred at 400-800 rpm for 15-30 min, then placed at 60-75° C. for reaction for 6-20 h, and distilled under reduced pressure to obtain a crude modified xanthan gum product;

[0031] S4: washing, vacuum drying, crushing, and passing through a 80-150 mesh sieve to obtain the modified xanthan gum.

[0032] Beneficial effects of the present invention: The present invention provides a high temperature resistant viscosity enhancer for oil-based drilling fluid and a preparation method thereof, with modified xanthan gum, polyglycerol-3 polyricinoleate, diesel, 1,2-propylene glycol, and attapulgite as main raw materials, and through the reasonable proportion of the raw materials, not only solves the problem that the diesel-based drilling fluid cannot be prepared due to the increase in viscosity and deterioration of rheology caused by the thickening of the oil phase in a low temperature environment, but also satisfies the problem of viscosity reduction due to the increase in temperature under high temperature conditions. The present invention simultaneously uses 2-acrylamide-2-methylpropanesulfonic acid and phenylboronic acid polymer for simultaneous modification, which not only retains the salt resistance of xanthan gum, increases the viscosity of the drilling fluid, and improves its ability to carry solid particles, but also improves the temperature resistance of high xanthan gum and extends its service life underground. DETAILED DESCRIPTION

[0033] The above content of the present invention is further described in detail below in conjunction with specific implementation modes, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments.

[0034] Introduction of some raw materials in this application:

[0035] Xanthan gum was purchased from Wuhan Jiyesheng Chemical Co., Ltd., model: JYS154.

[0036] Polyglycerol-3 polyricinoleate was purchased from Jiangsu Jufeng Chemical Technology Co., Ltd., model: Jolee7887.

[0037] Diesel was purchased from Huizhou Shuanghe Trading Co., Ltd., model: DelvacXHPExtra10W-40.

[0038] Example 1

[0039] A high temperature resistant viscosity enhancer for oil-based drilling fluid is composed of the following raw materials in parts by weight: 10 parts by weight of xanthan gum, 1 part by weight of polyglycerol-3 polyricinoleate, 6 parts by weight of diesel, 5 parts by weight of 1,2-propylene glycol, and 4 parts by weight of attapulgite.

[0040] The preparation method of the high temperature resistant viscosity enhancer for oil-based drilling fluid is as follows: 10 parts by weight of xanthan gum, 1 part by weight of polyglycerol-3 polyricinoleate, 6 parts by weight of diesel, 5 parts by weight of 1,2-propylene glycol and 4 parts by weight of attapulgite are mixed and stirred.

[0041] Example 2

[0042] A high temperature resistant viscosity enhancer for oil-based drilling fluid is composed of the following raw materials in parts by weight: 10 parts by weight of modified xanthan gum, 1 part by weight of polyglycerol-3 polyricinoleate, 6 parts by weight of diesel, 5 parts by weight of 1,2-propylene glycol, and 4 parts by weight of attapulgite.

[0043] The preparation method of the modified xanthan gum comprises the following steps:

[0044] S1: at room temperature, 5 parts by weight of xanthan gum and 100 parts by weight of water are mixed, the pH value is adjusted to 11, the mixture is stirred evenly, and vacuum dried to obtain pretreated xanthan gum;

[0045] S2: 5 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 100 parts by weight of dimethyl sulfoxide and 30 parts by weight of water are mixed and stirred to obtain a mixed solution a; all of the above-mentioned pretreated xanthan gum is added to the mixed solution a, and the mixture is reacted at 60° C. for 6 hours, and the solvent is removed by distillation under reduced pressure to obtain modified xanthan gum.

[0046] The preparation method of the high temperature resistant viscosity enhancer for oil-based drilling fluid is as follows: 10 parts by weight of modified xanthan gum, 1 part by weight of polyglycerol-3 polyricinoleate, 6 parts by weight of diesel, 5 parts by weight of 1,2-propylene glycol and 4 parts by weight of attapulgite are mixed and stirred.

[0047] Example 3

[0048] A high temperature resistant viscosity enhancer for oil-based drilling fluid is composed of the following raw materials in parts by weight: 10 parts by weight of modified xanthan gum, 1 part by weight of polyglycerol-3 polyricinoleate, 6 parts by weight of diesel, 5 parts by weight of 1,2-propylene glycol, and 4 parts by weight of attapulgite.

[0049] The preparation method of the modified xanthan gum comprises the following steps:

[0050] S1: at room temperature, 5 parts by weight of xanthan gum and 100 parts by weight of water are mixed, the pH value is adjusted to 11, the mixture is stirred evenly, vacuum dried, and irradiated with electrons for 15 minutes to obtain pretreated xanthan gum; the electron beam energy of the electron irradiation is 8 MeV, and the irradiation dose is 100 kGy;

[0051] S2: 5 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 100 parts by weight of dimethyl sulfoxide and 30 parts by weight of water are mixed and stirred to obtain a mixed solution a; all of the above-mentioned pretreated xanthan gum is added to the mixed solution a, and the mixture is reacted at 60° C. for 6 hours, and the solvent is removed by distillation under reduced pressure to obtain modified xanthan gum.

[0052] The preparation method of the high temperature resistant viscosity enhancer for oil-based drilling fluid is as follows: 10 parts by weight of modified xanthan gum, 1 part by weight of polyglycerol-3 polyricinoleate, 6 parts by weight of diesel, 5 parts by weight of 1,2-propylene glycol and 4 parts by weight of attapulgite are mixed and stirred.

[0053] Example 4

[0054] A high temperature resistant viscosity enhancer for oil-based drilling fluid is composed of the following raw materials in parts by weight: 10 parts by weight of modified xanthan gum, 1 part by weight of polyglycerol-3 polyricinoleate, 6 parts by weight of diesel, 5 parts by weight of 1,2-propylene glycol, and 4 parts by weight of attapulgite.

[0055] The preparation method of the modified xanthan gum comprises the following steps:

[0056] S1: at room temperature, 5 parts by weight of xanthan gum and 100 parts by weight of water are mixed, the pH value is adjusted to 11, the mixture is stirred evenly, vacuum dried, and irradiated with electrons for 15 minutes to obtain pretreated xanthan gum; the electron beam energy of the electron irradiation is 8 MeV, and the irradiation dose is 100 kGy;

[0057] S2: 5 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 100 parts by weight of dimethyl sulfoxide and 30 parts by weight of water are mixed and stirred to obtain a mixed solution a; all of the above-mentioned pretreated xanthan gum is added to the mixed solution a, reacted at 60° C. for 6 hours, and the solvent is removed by distillation under reduced pressure to obtain a preliminary modified xanthan gum;

[0058] S3, under nitrogen protection, 5 parts by weight of acrylic acid, 4 parts by weight of dimethylaminopropyl acrylamide, 0.3 parts by weight of 5-acrylamide-2-(aminomethyl)phenylboric acid, 50 parts by weight of water and 60 parts by weight of N-vinyl pyrrolidone were mixed, 0.2 parts by weight of diisopropyl peroxydicarbonate, 0.3 parts by weight of 0.1 mol / L sodium formate aqueous solution and 5 parts by weight of the above-mentioned preliminary modified xanthan gum were added, stirred at 600 rpm for 20 min, then placed at 70° C. for reaction for 12 h, and distilled under reduced pressure to obtain a crude modified xanthan gum product;

[0059] S4: washing, vacuum drying, crushing, and passing through a 100-mesh sieve to obtain the modified xanthan gum.

[0060] The preparation method of the high temperature resistant viscosity enhancer for oil-based drilling fluid is as follows: 10 parts by weight of modified xanthan gum, 1 part by weight of polyglycerol-3 polyricinoleate, 6 parts by weight of diesel, 5 parts by weight of 1,2-propylene glycol and 4 parts by weight of attapulgite are mixed and stirred.

[0061] Example 5

[0062] A high temperature resistant viscosity enhancer for oil-based drilling fluid is composed of the following raw materials in parts by weight: 10 parts by weight of modified xanthan gum, 1 part by weight of polyglycerol-3 polyricinoleate, 6 parts by weight of diesel, 5 parts by weight of 1,2-propylene glycol, and 4 parts by weight of attapulgite.

[0063] The preparation method of the modified xanthan gum comprises the following steps:

[0064] S1: at room temperature, 5 parts by weight of xanthan gum and 100 parts by weight of water are mixed, the pH value is adjusted to 11, the mixture is stirred evenly, vacuum dried, and irradiated with electrons for 15 minutes to obtain pretreated xanthan gum; the electron beam energy of the electron irradiation is 8 MeV, and the irradiation dose is 100 kGy;

[0065] S2, under nitrogen protection, 5 parts by weight of acrylic acid, 4 parts by weight of dimethylaminopropyl acrylamide, 0.3 parts by weight of 5-acrylamide-2-(aminomethyl)phenylboric acid, 50 parts by weight of water and 60 parts by weight of N-vinyl pyrrolidone were mixed, 0.2 parts by weight of diisopropyl peroxydicarbonate, 0.3 parts by weight of 0.1 mol / L sodium formate aqueous solution and 5 parts by weight of the above-mentioned preliminary modified xanthan gum were added, stirred at 600 rpm for 20 min, then placed at 70° C. for reaction for 12 h, and distilled under reduced pressure to obtain a crude modified xanthan gum product;

[0066] S3: washing, vacuum drying, crushing and passing the crude modified xanthan gum through a 100-mesh sieve to obtain modified xanthan gum.

[0067] The preparation method of the high temperature resistant viscosity enhancer for oil-based drilling fluid is as follows: 10 parts by weight of modified xanthan gum, 1 part by weight of polyglycerol-3 polyricinoleate, 6 parts by weight of diesel, 5 parts by weight of 1,2-propylene glycol and 4 parts by weight of attapulgite are mixed and stirred.

[0068] Test Example 1

[0069] The high temperature resistant viscosity enhancers for oil-based drilling fluid prepared in the above embodiments 1-5 are respectively used to prepare oil-based drilling fluid systems. The basic formula adopted is 100 parts by weight of base oil (diesel in the above embodiments), 15 parts by weight of silicon dioxide, 7 parts by weight of nonadecanoic acid amide + 2 parts by weight of the high temperature resistant viscosity enhancer for oil-based drilling fluid prepared in embodiments 1-5, 2 parts by weight of 25wt% CaCl2 aqueous solution, 3 parts by weight of oleic acid diethanolamide, 3 parts by weight of sodium hydroxide, and 5 parts by weight of sodium carboxymethyl cellulose. The above raw materials are stirred at 8000 rpm for 1 hour to obtain an oil-based drilling fluid.

[0070] With reference to the national standard GB / T16783.2-2012 "Field Test of Drilling Fluids in Petroleum and Natural Gas Industry Part 2: Oil-Based Drilling Fluids", the rheological properties of the oil-based drilling fluids to which the viscosity enhancers of Examples 1-5 were added were tested at -4°C and 180°C. Each group was tested 4 times and the average value was taken. The results are shown in Table 1.

[0071] Table 1 Rheological properties test results of oil-based drilling fluid

[0072]

[0073] Test Example 2

[0074] Salt resistance test: Calcium chloride brine with a concentration of 20wt% was prepared, and the above-prepared oil-based drilling fluid was subjected to 0%, 10%, and 30% brine contamination experiments, respectively. 40mL was added to the aged oil-based drilling fluid of Test Example 1, stirred at high speed for 30min, loaded into an aging tank, aged at 180°C for 16h, and then the rheological properties at 65°C were measured. Each group was tested 4 times, and the average value was taken. The results are shown in Table 2.

[0075] Table 2 Salt resistance test results

[0076]

[0077] From the above results, it can be seen that the oil-based drilling fluid prepared by the high temperature resistant viscosity raising agent for oil-based drilling fluid of the present invention has good viscosity, high temperature resistance and salt resistance. From Examples 1-3, it can be seen that in S1, xanthan gum is pretreated and treated by electron irradiation, which not only triggers the cross-linking reaction between xanthan gum molecules, so that it forms a more stable network structure, but also can enhance the mechanical properties and stability of xanthan gum; electron irradiation can stimulate the generation of free radicals in the reactant molecules, thereby promoting the reaction between xanthan gum and 2-acrylamide-2-methylpropane sulfonic acid, and effectively improving the reaction yield; in S2, the pretreated xanthan gum and 2-acrylamide-2-methylpropane sulfonic acid are grafted with the group from 2-acrylamide-2-methylpropane sulfonic acid through esterification reaction, which can thicken the double electric layer on the surface of xanthan gum, enhance the salt resistance of xanthan gum, increase the viscosity of drilling fluid, improve its ability to carry solid particles, reduce the sedimentation velocity of solid particles, thereby achieving effective well wall support and cementing effect. From Examples 3-5, it can be seen that xanthan gum modified by phenylboronic acid polymer has very high viscosity and improved heat resistance. The specific mechanism is as follows: (1) The addition of acrylic acid can form a stable complex with calcium ions, thereby effectively controlling the formation of precipitates in the oil-based drilling fluid and preventing the precipitation of solid particles in the drilling fluid and clogging the wellbore; (2) The introduction of dimethylaminopropyl acrylamide can improve the heat resistance of xanthan gum, enhance the stability of oil-based drilling fluid in high temperature environment, and extend its service life underground; (3) 5-acrylamide-2-(aminomethyl)phenylboronic acid has good anti-pollution properties, which can reduce the performance degradation of oil-based drilling fluid after contact with formation water or other pollution sources, and maintain the stability and performance of the drilling fluid; (4) The addition of 2-acrylamide 2-methylpropanesulfonic acid can increase the viscosity and consistency provided by xanthan gum, further improving the bearing capacity and wellbore support effect of the oil-based drilling fluid.

[0078] The invention adopts 2-acrylamide-2-methylpropanesulfonic acid and phenylboronic acid polymer for simultaneous modification, which not only retains the salt resistance of xanthan gum and increases the viscosity of drilling fluid to improve its ability to carry solid particles, but also improves the temperature resistance of high xanthan gum and prolongs its service life underground.

Claims

1. A high temperature resistant viscosity enhancer for oil-based drilling fluid, characterized in that: It is composed of the following raw materials: xanthan gum, base oil, emulsifier, 1,2-propylene glycol and attapulgite.

2. The high temperature resistant viscosity increasing agent for oil-based drilling fluid according to claim 1, characterized in that: It is composed of the following raw materials: modified xanthan gum, base oil, emulsifier, 1,2-propylene glycol and attapulgite.

3. The high temperature resistant viscosity increasing agent for oil-based drilling fluid according to claim 2, characterized in that: The invention is composed of the following raw materials in parts by weight: 7-14 parts by weight of modified xanthan gum, 0.5-2 parts by weight of emulsifier, 5-9 parts by weight of base oil, 4-8 parts by weight of 1,2-propylene glycol and 2-5 parts by weight of attapulgite.

4. The high temperature resistant viscosity increasing agent for oil-based drilling fluid according to claim 2 or 3, characterized in that: The base oil is at least one of diesel and white oil.

5. The high temperature resistant viscosity increasing agent for oil-based drilling fluid according to claim 2 or 3, characterized in that: The emulsifier is at least one of tall oil fatty acid, polyglycerol-3 polyricinoleate, Span 80, hexadecyl ricinoleate, and sorbitan monopalmitate.

6. The high temperature resistant viscosity increasing agent for oil-based drilling fluid according to claim 2 or 3, characterized in that: The preparation method of the modified xanthan gum comprises the following steps: S1. Mix xanthan gum and water at room temperature and stir evenly to obtain pretreated xanthan gum; S2: 2-acrylamide-2-methylpropanesulfonic acid, dimethyl sulfoxide and water are mixed and stirred to obtain a mixed solution a; all the above-mentioned pretreated xanthan gum is added to the mixed solution a for reaction to obtain modified xanthan gum.

7. The high temperature resistant viscosity increasing agent for oil-based drilling fluid according to claim 6, characterized in that: The preparation method of the modified xanthan gum comprises the following steps: S1. Mix xanthan gum and water at room temperature and stir evenly to obtain pretreated xanthan gum; S2: 2-acrylamide-2-methylpropanesulfonic acid, dimethyl sulfoxide and water are mixed and stirred to obtain a mixed solution a; all the pretreated xanthan gum is added to the mixed solution a to react to obtain a preliminary modified xanthan gum; S3, under nitrogen protection, acrylic acid, dimethylaminopropyl acrylamide, 5-acrylamide-2-(aminomethyl)phenylboronic acid, water and N-vinyl pyrrolidone are mixed, diisopropyl peroxydicarbonate, sodium formate aqueous solution and the above preliminary modified xanthan gum are added, stirred, and reacted in a water bath to obtain a crude modified xanthan gum product; S4: washing, vacuum drying and crushing the crude modified xanthan gum to obtain modified xanthan gum.

8. The method for preparing the high temperature resistant viscosity increasing agent for oil-based drilling fluid according to any one of claims 1 to 7, characterized in that: The modified xanthan gum, emulsifier, base oil, 1,2-propylene glycol and attapulgite are mixed and stirred.

Images