Preparation method of shear strength improving agent for water-based drilling fluid

Abstract

The invention relates to a preparation method of a shear strength improving agent for water-based drilling fluid, and belongs to the technical field of oilfield chemistry. A nonionic monomer, an anionic monomer, a temperature-sensitive monomer, a dopamine monomer and a cyclodextrin monomer are copolymerized in water to obtain a polymer with multiple functional units. According to the present invention, the dopamine unit, the polymer and the clay particles can form the composite structure, and the host-guest interaction of the temperature-sensitive unit and the cyclodextrin at the high temperature can form the grid structure between the polymer molecules, such that the three-dimensional network structure between the polymer and the clay particles is constructed so as to achieve the high dynamic plastic ratio of the drilling fluid system; a result test shows that the shear strength improving agent prepared by the invention has better temperature resistance, has less influence on the plastic viscosity of a system while obviously improving the dynamic shear force of the drilling fluid system, and is suitable for being used as a flow pattern regulator of a water-based drilling fluid system.

Description

Technical Field

[0001] The present invention relates to a preparation method of a viscosity increasing and gel strength enhancing agent for water-based drilling fluids, belonging to the technical field of oilfield chemistry. Background Art

[0002] In recent years, with the increasing difficulty of drilling operations, higher requirements have been put forward for the rheological properties of drilling fluids on site. Among them, the plastic viscosity and dynamic gel strength of drilling fluids are two important parameters of the rheological properties of drilling fluids. The plastic viscosity reflects the strength of the internal frictional force in the drilling fluid; if the plastic viscosity is too small, it is not conducive to carrying cuttings, and it is easy to cause problems such as wellbore collapse and lost circulation; if the plastic viscosity is too large, it is easy to cause difficulties in injection, large flow resistance, affect the drilling speed, and difficult degassing. The dynamic gel strength reflects the strength of the internal network structure of the drilling fluid under dynamic conditions; the higher the dynamic gel strength, the stronger the cutting-carrying ability of the drilling fluid. During drilling construction, the dynamic gel strength should be increased as much as possible and the plastic viscosity should be controlled. At present, water-based drilling fluids generally have the disadvantages of relatively high plastic viscosity and relatively low dynamic gel strength. Therefore, it is very necessary to develop a viscosity increasing and gel strength enhancing agent for drilling fluids with a significant gel strength enhancing effect and a small impact on plastic viscosity.

[0003] Chinese invention patent CN 116410403A discloses a high-temperature resistant viscosity increasing and gel strength enhancing agent and its preparation method. The high-temperature resistant viscosity increasing and gel strength enhancing agent contains cross-linked monomer structural units, hydrated monomer structural units and high-temperature resistant monomer structural units. By dissolving N,N'-(1,3-phenylene)bisacrylamide, 2-acrylamido-2-methylpropanesulfonic acid and its derivatives and structural units containing vinyl or propenyl in a solvent, stirring evenly to obtain a mixture; adding an initiator to the mixture, stirring, and then standing for reaction and drying to obtain the high-temperature resistant viscosity increasing and gel strength enhancing agent. Since the polymer contains amide groups, it can adsorb on the surface of clay particles, having the functions of increasing viscosity and gel strength, and having high temperature resistance and good rheological properties, and can play a good role in water-based drilling fluids. The interaction between the molecules of this gel strength enhancing agent is mainly intermolecular forces such as van der Waals forces and hydrogen bonds. The strength of these forces is relatively low and sensitive to temperature. Therefore, the gel strength enhancing effect of such gel strength enhancing agent products is generally average, and it is difficult to achieve the effect of "enhancing gel strength without increasing viscosity".

[0004] Chinese Invention Patent CN 107286915A discloses a preparation method of a drilling fluid viscosifier, and the steps are as follows: Methyl methacrylate, ethylene glycol, butyl acrylate and propylene oxide are put into a reactor, the pH is adjusted with sodium hydroxide solution, and then zinc stearate is added. The reaction is carried out under nitrogen protection. Subsequently, chitosan and vinyltrimethoxysilane are added, mixed well and left standing. Then, a catalyst and an initiator are added for modification reaction. After the reaction is completed, a crosslinking agent is added for reaction and discharging. The discharged material is filtered and the filtrate is collected. After distillation, the distillation residue is collected and mixed with sodium oxalate, an emulsifier and an auxiliary agent, and the stirred mixture is collected to obtain the drilling fluid viscosifier. This method has relatively cumbersome steps, high cost, and poor control over the dissolution performance of the product. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a preparation method of a viscosifier for water-based drilling fluid. General Overview of the Invention

[0007] In the present invention, a polymer with multiple functional units is prepared by copolymerizing a non-ionic monomer, an anionic monomer, a temperature-sensitive monomer, a dopamine monomer and a cyclodextrin monomer in water. Through the reaction of the dopamine unit with the surface functional groups of clay particles, a stable polymer / clay composite structure is formed. In addition, by utilizing the hydrophobic transformation of the temperature-sensitive unit at high temperature and through its host-guest interaction with cyclodextrin, a network structure between polymer molecules is formed, thereby constructing a three-dimensional network structure between the polymer and clay particles, realizing that while significantly improving the dynamic shear force of the drilling fluid system, the influence on the plastic viscosity of the system is relatively small. Detailed Description of the Invention

[0009] The technical solution of the present invention is as follows.

[0010] A preparation method of a viscosifier for water-based drilling fluid:

[0011] Add non-ionic monomer, anionic monomer, dopamine monomer, temperature-sensitive monomer, cyclodextrin monomer and deionized water into a three-necked flask equipped with a stirrer, a thermometer and a nitrogen inlet tube in sequence. After stirring until all raw materials are dissolved, introduce nitrogen for 30 min, control the pH at 6-10 and the temperature at 0-10 °C, then add sodium bisulfite, persulfate and azo compound, react for 1-10 h, then raise the temperature to 70 °C and react for 1 h. Dry and crush the product to obtain it. The mass ratio of the non-ionic monomer to the anionic monomer is 1:(0.1-1), the ratio of the total mass of the non-ionic monomer and the anionic monomer, the mass of the dopamine monomer, and the mass of the temperature-sensitive monomer is 1:(0.002-0.06):(0.01-0.1), the mass ratio of the temperature-sensitive monomer to the cyclodextrin monomer is 1:(0.5-10), the ratio of the total mass of the non-ionic monomer, anionic monomer, dopamine monomer, temperature-sensitive monomer and cyclodextrin monomer to the mass of deionized water is 1:(1-6), and the mass ratio of deionized water, sodium bisulfite, persulfate, azo compound is 1:(0.0001-0.002):(0.00005-0.001):(0.0001-0.002);

[0012] According to the present invention, preferably, the non-ionic monomer is one or a mixture of two or more of acrylamide, methacrylamide, N-hydroxymethylacrylamide, N-hydroxyethylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, vinylpyrrolidone, vinylcaprolactam;

[0013] Preferably, the anionic monomer is one or a mixture of two or more of acrylic acid, methacrylic acid, allylsulfonic acid, sodium methallylsulfonate, sodium vinylsulfonate, sodium p-styrenesulfonate, 2-acrylamido-2-methylpropanesulfonic acid;

[0014] Preferably, the dopamine monomer is

[0015]

[0016] where a is 1-4;

[0017] Preferably, the temperature-sensitive monomer is

[0018]

[0019] where b is 1-6, c is 5-50, and R1 is one of H, CH3, CH2CH3, CH2CH2CH3;

[0020] Preferably, the cyclodextrin monomer is

[0021]

[0022] Among them, R2 is one of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin after removing one hydroxyl group, and d is 1-5;

[0023] Preferably, the persulfate is one of potassium persulfate, sodium persulfate, and ammonium persulfate;

[0024] Preferably, the azo compound is one of azobisisobutyronitrile, azobisisoheptonitrile, dimethyl azobisisobutyrate, azobis(isobutyramidine) dihydrochloride, azobis(2-methylpropionamidine) dihydrochloride, and azoisobutyronitrile carboxamide, or a mixture of two or more of them;

[0025] Preferably, the mass ratio of the non-ionic monomer to the anionic monomer is 1:(0.2-0.8);

[0026] Preferably, the ratio of the total mass of the non-ionic monomer and the anionic monomer, the mass of the dopamine monomer, and the mass of the thermosensitive monomer is 1:(0.005-0.05):(0.02-0.08);

[0027] Preferably, the mass ratio of the thermosensitive monomer to the cyclodextrin monomer is 1:(1-6);

[0028] Preferably, the ratio of the total mass of the non-ionic monomer, the anionic monomer, the dopamine monomer, the thermosensitive monomer, and the cyclodextrin monomer to the mass of deionized water is 1:(1.5-4);

[0029] Preferably, the mass ratio of deionized water, sodium bisulfite, persulfate, and azo compound is 1:(0.0001-0.001):(0.00005-0.0005):(0.0001-0.001);

[0030] Preferably, the reaction pH is 7-9, the reaction temperature is 0-6°C, and the reaction time is 2-9 h.

[0031] The excellent effects of the present invention are as follows:

[0032] 1. The reaction conditions are mild, the process is simple and safe, and large-scale industrial production can be achieved.

[0033] 2. The phenolic hydroxyl groups in the polymer dopamine unit can strongly adsorb on the surface of clay particles, forming a bridge between the polymer molecules and the clay particles, thereby constructing an organic-inorganic composite structure.

[0034] 3. At lower temperatures, the thermosensitive units in the polymer are hydrophilic structures and cannot form hydrophobic, host-guest and other interactions, having little effect on the rheology of the drilling fluid system; at higher temperatures, the thermosensitive units in the polymer transform into hydrophobic structures, and through the host-guest interaction with cyclodextrin, a three-dimensional network structure between molecules is formed, thereby significantly improving the dynamic shear force of the drilling fluid system.

[0035] 4. The product of the present invention has good temperature and salt resistance, excellent compatibility with conventional drilling fluid treatment agents, and can meet the requirements of drilling fluid systems under different working conditions.

[0036] 5. The product of the present invention can be applied to low-bentonite or non-bentonite water-based drilling fluid systems, effectively reducing the risk of formation contamination by solid phase invasion of the drilling fluid and achieving the effect of reservoir protection.

[0037] 6. The product prepared by the present invention is convenient for storage, transportation and use, meeting the requirements of environmental protection. Specific Embodiments

[0038] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods.

[0039] Unless otherwise specified, the reagents and materials can be obtained from commercial sources.

[0040] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0041] Example 1:

[0042] A viscosifier for water-based drilling fluid with a dopamine structure is prepared as follows:

[0043] 100 g of acrylamide, 50 g of 2-acrylamido-2-methylpropanesulfonic acid, 3 g of dopamine monomer (a is 2), 6 g of thermosensitive monomer (b is 3, c is 30, R1 is CH2CH3), 18 g of cyclodextrin monomer (R2 is β-cyclodextrin after removing one hydroxyl group, d is 2) and 400 g of deionized water are successively added to a three-necked flask equipped with a stirrer, a thermometer and a nitrogen inlet tube. After stirring until all raw materials are dissolved, 9.7 g of sodium hydroxide is added to adjust the pH to 7. Nitrogen is introduced for 30 min, and the temperature of the system is controlled at 3 °C using an ice bath. Then, 0.2 g of sodium bisulfite, 0.1 g of potassium persulfate and 0.2 g of 2,2'-azobis(2-methylpropionamidine) dihydrochloride are added, and the reaction is carried out for 6 h. Then the temperature is raised to 70 °C and the reaction is carried out for 1 h. The product is dried and pulverized to obtain the product.

[0044] Example 2:

[0045] As described in Example 1, the difference is that the non-ionic water-soluble monomer is 70 g of N,N-dimethylacrylamide.

[0046] Example 3:

[0047] As described in Example 1, the difference is that the non-ionic water-soluble monomer is 50 g of N-hydroxymethylacrylamide and 60 g of vinylpyrrolidone.

[0048] Example 4:

[0049] As described in Example 1, the difference is that the anionic water-soluble monomer is 30 g of methacrylic acid and 40 g of sodium p-styrenesulfonate, and the addition amount of sodium hydroxide becomes 13.9 g.

[0050] Example 5:

[0051] As described in Example 1, the difference is that the anionic water-soluble monomer is 20 g of acrylic acid and 20 g of sodium methallylsulfonate, and the addition amount of sodium hydroxide becomes 11.1 g.

[0052] Example 6:

[0053] As described in Example 1, the difference is that in the dopamine monomer, a is 4 and the addition amount is 2 g.

[0054] Example 7:

[0055] As described in Example 1, the difference is that in the dopamine monomer, a is 1 and the addition amount is 4 g.

[0056] Example 8:

[0057] As described in Example 1, the difference is that in the thermosensitive monomer, b is 6, c is 40, R1 is CH2CH2CH3, and the addition amount is 8 g.

[0058] Example 9:

[0059] As described in Example 1, the difference is that in the thermosensitive monomer, b is 1, c is 20, R1 is H), and the addition amount is 4 g.

[0060] Example 10:

[0061] As described in Example 1, the difference is that in the cyclodextrin monomer, R2 is α-cyclodextrin after removing one hydroxyl group, d is 1), and the addition amount is 22 g.

[0062] Example 11:

[0063] As described in Example 1, the difference is that in the cyclodextrin monomer, R2 is γ-cyclodextrin after removing one hydroxyl group, d is 4), and the addition amount is 15 g.

[0064] Example 12:

[0065] As described in Example 1, the difference is that the addition amount of deionized water is 560 g.

[0066] Example 13:

[0067] As described in Example 1, the difference is that the addition amount of sodium bisulfite is 0.3 g and the addition amount of potassium persulfate is 0.15 g.

[0068] Example 14:

[0069] As described in Example 1, the difference is that the initiator is azobisisobutyronitrile and the addition amount is 0.3 g.

[0070] Example 15:

[0071] As described in Example 1, the difference is that the system temperature is controlled at 1 °C and the reaction time is 8 h.

[0072] Comparative Example 1:

[0073] As described in Example 1, the difference is that the addition amount of the temperature-sensitive monomer is 0 g.

[0074] Comparative Example 2:

[0075] As described in Example 1, the difference is that the addition amounts of the dopamine monomer, the temperature-sensitive monomer, and the cyclodextrin monomer are all 0 g.

[0076] Performance evaluation

[0077] The thixotropy performance of the products of Comparative Examples 1-2 and Examples 1-15 in the water-based drilling fluid was evaluated. The evaluation of each sample was carried out in the brine-based slurry. Before and after aging at 160 °C for 16 h, the rheological properties were measured with a ZNN-D6 six-speed rotational viscometer. When comparing the temperature-sensitive effects of the samples, the test temperatures were 20 °C, 40 °C, 60 °C, and 80 °C respectively; when comparing the viscosity-increasing and thixotropy-increasing abilities of the samples, the test temperature was 80 °C. The system rheological parameters were calculated according to the following formulas. The test results are shown in Tables 1 and 2.

[0078] PV = Φ600 - Φ300

[0079] YP = 0.511×(Φ300 - PV)

[0080] R dp = YP / PV

[0081] In the formula:

[0082] Φ600—the reading of the six-speed rotational viscometer at 600 r / min, dimensionless;

[0083] Φ300—the reading of the six-speed rotational viscometer at 300 r / min, dimensionless;

[0084] PV—plastic viscosity, mPa·s;

[0085] YP—yield point, Pa;

[0086] R dp —yield-plastic ratio, Pa / mPa·s.

[0087] Brine-based slurry: 400 mL of water + 4% bentonite + 20% sodium chloride + 0.2% sodium carbonate.

[0088] Evaluation system: 400 mL of water + 4% bentonite + 20% sodium chloride + 0.2% sodium carbonate + 1.5% thixotropic agent.

[0089] Table 1 Yield point of the test samples at different temperatures

[0090]

[0091] Table 2 Rheological properties of the test samples before and after aging

[0092]

[0093] As can be seen from Table 1, when the temperature rises to 80 °C, the yield points of Examples 1 to 15 increase significantly, showing good temperature-sensitive characteristics. As can be seen from Table 2, the plastic viscosities of Examples 1 to 15 are small before and after aging, the yield points are large, and the yield-plastic ratios are high; in Comparative Example 1, only the composite structure formed by dopamine units and clay particles is relied on to increase the yield point, lacking the host-guest interaction between the temperature-sensitive monomer and cyclodextrin, so the yield point is small and the yield-plastic ratio is low; Comparative Example 2 is a copolymerization product of a non-ionic monomer and an anionic monomer, and its performance is similar to that of a conventional linear polymer. While increasing the yield point of the drilling fluid, the plastic viscosity is increased significantly, and the yield-plastic ratio is the lowest.

Claims

1. A preparation method of a viscosifier for water-based drilling fluid, comprising the following steps: Add non-ionic monomer, anionic monomer, dopamine monomer, temperature-sensitive monomer, cyclodextrin monomer and deionized water into a three-necked flask equipped with a stirrer, a thermometer and a nitrogen inlet tube in sequence. After stirring until all raw materials are dissolved, introduce nitrogen for 30 min, control the pH at 6 - 10 and the temperature at 0 - 10 °C, then add sodium bisulfite, persulfate and azo compound, react for 1 - 10 h, then raise the temperature to 70 °C and react for 1 h. Dry and crush the product to obtain it; the mass ratio of non-ionic monomer to anionic monomer is 1:(0.1 - 1), the ratio of the total mass of non-ionic monomer and anionic monomer, dopamine monomer mass, temperature-sensitive monomer mass is 1:(0.002 - 0.06):(0.01 - 0.1), the mass ratio of temperature-sensitive monomer to cyclodextrin monomer is 1:(0.5 - 10), the ratio of the total mass of non-ionic monomer, anionic monomer, dopamine monomer, temperature-sensitive monomer and cyclodextrin monomer to deionized water mass is 1:(1 - 6), and the mass ratio of deionized water, sodium bisulfite, persulfate, azo compound is 1:(0.0001 - 0.002):(0.00005 - 0.001):(0.0001 - 0.002); The non-ionic monomer is one or a mixture of two or more of acrylamide, methacrylamide, N-methylolacrylamide, N-hydroxyethylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, vinylpyrrolidone, vinylcaprolactam; The anionic monomer is one or a mixture of two or more of acrylic acid, methacrylic acid, allylsulfonic acid, sodium methallylsulfonate, sodium vinylsulfonate, sodium p-styrenesulfonate, 2-acrylamido-2-methylpropanesulfonic acid; The dopamine monomer is where a is 1 - 4; The temperature-sensitive monomer is where b is 1 - 6, c is 5 - 50, and R1 is one of H, CH3, CH2CH3, CH2CH2CH3; The cyclodextrin monomer is where R2 is one of α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin after removing one hydroxyl group, and d is 1 - 5; The persulfate is one of potassium persulfate, sodium persulfate, ammonium persulfate; The azo compound is one or a mixture of two or more of azobisisobutyronitrile, azobisisoheptonitrile, dimethyl azodicarboxylate, azodiisobutyramidine hydrochloride, azobis(2-methylpropionamidine) dihydrochloride, azoisobutyronitrile carboxamide; 2. The preparation method of a viscosity increasing agent for water-based drilling fluid according to claim 1, characterized in that, The mass ratio of non-ionic monomer to anionic monomer is 1:(0.2 - 0.8).

3. The preparation method of a viscosity increasing agent for water-based drilling fluid according to claim 1, characterized in that, The ratio of the total mass of non-ionic monomer and anionic monomer, dopamine monomer mass, temperature-sensitive monomer mass is 1:(0.005 - 0.05):(0.02 - 0.08).

4. The preparation method of a rheology increasing agent for water-based drilling fluid according to claim 1, characterized in that, The mass ratio of temperature-sensitive monomer to cyclodextrin monomer is 1:(1 - 6).

5. The preparation method of a viscosifier for water-based drilling fluid according to claim 1, characterized in that, The ratio of the total mass of non-ionic monomer, anionic monomer, dopamine monomer, temperature-sensitive monomer and cyclodextrin monomer to deionized water mass is 1:(1.5 - 4).

6. The preparation method of a viscosity increasing agent for water-based drilling fluid according to claim 1, characterized in that, The mass ratio of deionized water, sodium bisulfite, persulfate, and azo compound is 1:(0.0001 - 0.001):(0.00005 - 0.0005):(0.0001 - 0.001).

7. The preparation method of a viscosity increasing agent for water-based drilling fluid according to claim 1, characterized in that, The reaction pH is 7 - 9, the reaction temperature is 0 - 6 °C, and the reaction time is 2 - 9 h.

Images