A starch-based polymer and a preparation method and application thereof

Abstract

The application discloses a starch-based polymer and a preparation method and application thereof, and the preparation method comprises the following steps: (1) mixing starch and amylase and simultaneously introducing water to perform maintenance treatment; (2) adding a plasticizer into the material obtained in the step (1), uniformly mixing and performing cooling treatment; (3) adding an initiator, acrylamide, a functional monomer, N,N-methylene bisacrylamide and water into the material obtained in the step (2) to perform explosive polymerization reaction, and the material obtained after the reaction is further subjected to optional forming and drying treatment to obtain the starch-based polymer. The application also provides the starch-based polymer and application thereof in water-based mud drilling and mining. The starch-based polymer prepared by the preparation method has good salt resistance, temperature resistance, filtration loss performance, and has the characteristics of environmental protection, lubrication, good water solubility, low cost, easy storage and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oilfield chemicals, and relates to a modified starch compound, in particular to a starch-based polymer and a preparation method and application thereof. BACKGROUND

[0002] In recent years, drilling and mining deep geology has put forward higher requirements for the performance of drilling fluid, and the development of high-temperature and salt reservoirs urgently needs high-performance drilling additives. The anti-sloughing solid wall material mainly based on sulfonated asphalt and the high-temperature resistant fluid loss additive material mainly based on functional synthetic polymers provide strong support for improving drilling efficiency and prolonging the safe construction period. However, with the continuous attention of the upstream site to the environmental performance of drilling and mining additives, the application of asphalt materials is limited, and the development and application of high-efficiency polymer additives have gradually become a research hotspot. The high-performance polymer additives represented by Snow Frac Driscal high-temperature resistant fluid loss additive have a temperature resistance of more than 200℃, and are popularized and applied in the upstream market, but the related products are expensive and are often sold with the system, not sold separately, which also brings difficulties to the site in reducing costs and increasing efficiency. In the face of the application needs of high-temperature and high-salt reservoir development and environmental protection needs, as well as the cost orientation of high-performance drilling and mining additives procurement and application, research related to green natural macromolecules has increased day by day. Among them, research related to widely available, inexpensive, environmentally friendly and degradable starch and lignin has gradually increased. The modification of starch materials is mainly etherification modification and graft modification.

[0003] Patent CN 106634880 A discloses a kind of water-based drilling fluid with amphiphilic starch fluid loss additive and its preparation method, which adopts the means of starch etherification and grafting, obtains modified starch product with good salt resistance and temperature resistance, and still has good fluid loss performance after 150℃, 16h aging under 2.0% addition amount. CN108410435A discloses a kind of nano starch fluid loss additive for drilling fluid and its preparation method, first prepares nano starch particles suitable for etherification modification, then carries out etherification modification and crosslinking modification, and the nano starch fluid loss additive obtained after purification has good fluid loss ability after 160℃ aging for 16h, and the HTHP filter loss of the base slurry with the product is less than 35mL. CN111647109A discloses a kind of modified starch fluid loss additive and its preparation method, which is obtained by grafting copolymerization of N-vinyl-2-caprolactam, hydroxybutyl vinyl ether, acrylic acid and maleic anhydride with starch, and has good viscosity reduction and fluid loss effect, and the fluid loss and viscosity reduction performance remain stable after 140℃ curing for 16h.

[0004] It can be seen from the above analysis that the modified starch product with temperature resistance of 140-160℃ is prepared by etherification or graft modification, and the temperature resistance and filtration loss resistance are excellent, which can meet the application requirements of some deep wells. However, in general, there is still a lack of modified starch products with environmental protection and temperature resistance in the development of reservoirs with bottom hole temperature exceeding 180℃, to meet the green development requirements of deep reservoirs. SUMMARY

[0005] In view of the deficiencies in the prior art, the core purpose of the present application is to provide a starch-based polymer and its preparation method and application. The starch-based polymer prepared by the preparation method has good salt resistance and temperature resistance and filtration loss resistance, and has the characteristics of environmental protection, lubrication, good water solubility, low cost, easy storage and the like.

[0006] The first aspect of the present application provides a starch-based polymer, the raw materials of the starch-based polymer include the following components in parts by weight: 100 parts of starch, 20-60 parts of water, 0.5-1.5 parts of amylase, 0.5-10 parts of plasticizer, 0.6-6 parts of initiator, 40-240 parts of acrylamide, 20-80 parts of functional monomer, and 0.05-0.25 parts of N,N-methylene bisacrylamide; preferably, the raw materials of the starch-based polymer include the following components: 100 parts of starch, 30-50 parts of water, 0.75-1.25 parts of amylase, 2-8 parts of plasticizer, 1-5 parts of initiator, 60-180 parts of acrylamide, 30-70 parts of functional monomer, and 0.1-0.2 parts of N,N-methylene bisacrylamide.

[0007] In the above-mentioned starch-based polymer, the amylase is isoamylase, and the specific activity of the isoamylase is 2000-6000 U / g substrate.

[0008] In the above-mentioned starch-based polymer, the plasticizer is one or more of polyhydric alcohol, amine, inorganic salt containing IA group metal, polyhydric alcohol, and polyester. The polyhydric alcohol is C2-C6 polyhydric alcohol, which can be one or more of ethylene glycol, glycerol, sorbitol, mannitol, and erythritol; the amine can be one or more of urea, thiourea, and formamide; the inorganic salt containing IA group metal can be one or more of sodium chloride, sodium bromide, sodium sulfate, sodium sulfite, sodium carbonate, sodium bicarbonate, sodium nitrate, sodium phosphate, sodium hydrogen phosphate, sodium silicate, potassium chloride, potassium bromide, potassium sulfate, potassium sulfite, potassium carbonate, potassium bicarbonate, potassium nitrate, potassium phosphate, and potassium hydrogen phosphate; the polyhydric alcohol can be at least one of polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 1000, and polyethylene glycol 2000; and the polyester can be one or more of glycerol mono-fatty acid ester, 1-ethyl-3-methyl imidazole acetate, polylactic acid, polybutylene succinate, polycaprolactone, and polybutylene adipate terephthalate.

[0009] The starch in the starch-based polymer is one or more of mung bean starch, cassava starch, sweet potato starch, potato starch, wheat starch, water caltrop starch, lotus root starch, and corn starch, preferably corn starch and / or potato starch.

[0010] The functional monomer in the starch-based polymer is one or more of sulfonic acid monomer and / or phosphonic acid monomer, and the specific functional monomer can be one or more of methacryloyloxyethyl-N,N-dimethylpropane sulfonate, N,N-dimethylallylamine propane sulfonate, 4-vinylpyridine propane sulfonate, N-methyldiallyl propane sulfonate, N-methyldiallyl butane sulfonate, 2-methyl-2-acrylamidopropane sulfonic acid, 2-acryloyloxyisopentyl sulfonate sodium, allyl sulfonate sodium, styrene sulfonate sodium, allyl phosphonic acid, (2-methylallyl) phosphonic acid diethyl ester, allyl phosphonic acid diethyl ester, allyl phosphonic acid dimethyl ester, vinyl phosphonic acid, 2-methylvinyl phosphonic acid, and 2-methyl-2-acrylamidopropane phosphonic acid.

[0011] The initiator in the starch-based polymer is one or two of potassium persulfate, sodium persulfate, and ammonium persulfate.

[0012] The starch-based polymer has a temperature resistance of ≥180℃, a high-temperature high-pressure filtration loss (HTHP) of ≤25 mL, a NaCl resistance of ≥300000 mg / L, and a divalent salt resistance of ≥50000 mg / L.

[0013] The second aspect of the present application provides a preparation method of a starch-based polymer, which comprises the following steps:

[0014] (1) mixing starch and amylase under contact conditions, while introducing water, mixing, and then curing;

[0015] (2) adding a plasticizer to the material obtained in step (1), mixing, and then cooling;

[0016] (3) adding an initiator, acrylamide, a functional monomer, N,N-methylene bisacrylamide, and water to the material obtained in step (2) to perform explosive polymerization, and then further performing optional molding and drying on the material obtained after the reaction to obtain a starch-based polymer.

[0017] In the preparation method of the starch-based polymer, the reaction in step (1) can be performed in a kneading reactor, and the specific process is to first add starch and amylase to the kneading reactor, spray water during kneading, and then perform curing. The kneading reactor can use existing equipment in the art, and can be made of stainless steel and provided with a vacuum pressure relief device under a sealed state.

[0018] In the preparation method of the starch-based polymer, the temperature of the curing treatment in step (1) is 30-70°C, preferably 40-60°C; and the curing treatment time is 10-50 min, preferably 20-40 min.

[0019] In the preparation method of the starch-based polymer, the starch in step (1) is one or more of mung bean starch, cassava starch, sweet potato starch, potato starch, cereal starch, water chestnut starch, lotus root starch, and corn starch, preferably corn starch and / or potato starch.

[0020] In the preparation method of the starch-based polymer, the amylase in step (1) is isoamylase, and the isoamylase specific activity is 2000-6000 U / g substrate.

[0021] In the preparation method of the starch-based polymer, the plasticizer in step (2) is one or more of a polyhydric alcohol, an amine, an inorganic salt containing a Group IA metal, a polyhydric alcohol, and a polyester. The polyhydric alcohol is a C2-C6 polyhydric alcohol, and can be one or more of ethylene glycol, glycerol, sorbitol, mannitol, and erythritol; the amine can be one or more of urea, thiourea, and formamide; the inorganic salt containing a Group IA metal can be one or more of sodium chloride, sodium bromide, sodium sulfate, sodium sulfite, sodium carbonate, sodium bicarbonate, sodium nitrate, sodium phosphate, sodium hydrogen phosphate, sodium silicate, potassium chloride, potassium bromide, potassium sulfate, potassium sulfite, potassium carbonate, potassium bicarbonate, potassium nitrate, potassium phosphate, and potassium hydrogen phosphate; the polyhydric alcohol can be at least one of polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 1000, and polyethylene glycol 2000; and the polyester can be one or more of glycerol mono-fatty acid ester, 1-ethyl-3-methyl imidazole acetate, polylactic acid, polybutylene succinate, polycaprolactone, and polybutylene adipate terephthalate.

[0022] In the preparation method of the starch-based polymer, the cooling in step (2) is to 15-35°C, preferably 20-30°C.

[0023] In the preparation method of the starch-based polymer, the initiator in step (3) is any one or more of potassium persulfate, sodium persulfate, and ammonium persulfate.

[0024] In the preparation method of the starch-based polymer, the functional monomer in step (3) is a sulfonic acid-based monomer and / or a phosphonic acid-based monomer, and the specific functional monomer can be one or more of methyl methacryloyloxyethyl-N,N-dimethylpropane sulfonate, N,N-dimethylallylamine propane sulfonate, 4-vinylpyridine propane sulfonate, N-methyldiallyl propane sulfonate, N-methyldiallyl butane sulfonate, 2-methyl-2-acrylamidopropane sulfonic acid, 2-acryloyloxyisopentyl sulfonate sodium, allyl sulfonate sodium, styrene sulfonate sodium, allyl phosphonic acid, (2-methylallyl) phosphonic acid diethyl ester, allyl phosphonic acid diethyl ester, allyl phosphonic acid dimethyl ester, vinyl phosphonic acid, 2-methylvinyl phosphonic acid, and 2-methyl-2-acrylamidopropane phosphonic acid.

[0025] In the preparation method of the starch-based polymer, the reaction temperature in step (3) is 40-50°C, and the reaction time is 20-60 min.

[0026] In the preparation method of the starch-based polymer, the heating can be stopped after the explosive polymerization reaction in step (3) is completed.

[0027] In the preparation method of the starch-based polymer, the molding in step (3) can adopt any one of the existing molding processes in the art, and specifically can be any one of compression molding, extrusion molding, and spray molding, and the extrusion molding process is preferred.

[0028] In the preparation method of the starch-based polymer, the material obtained after the reaction in step (3) is generally controlled at 40-60°C.

[0029] In the preparation method of the starch-based polymer, the drying temperature in step (3) is 80-120°C, and the drying time is 0.5-2 h.

[0030] In the preparation method of the starch-based polymer, the amounts of the starch, water, amylase, plasticizer, initiator, acrylamide, functional monomer, and N,N-methylene bisacrylamide are as follows: 100 parts of starch, 20-60 parts of water, 0.5-1.5 parts of amylase, 0.5-10 parts of plasticizer, 0.6-6 parts of initiator, 40-240 parts of acrylamide, 20-80 parts of functional monomer, and 0.05-0.25 parts of N,N-methylene bisacrylamide; preferably, 100 parts of starch, 30-50 parts of water, 0.75-1.25 parts of amylase, 2-8 parts of plasticizer, 1-5 parts of initiator, 60-180 parts of acrylamide, 30-70 parts of functional monomer, and 0.1-0.2 parts of N,N-methylene bisacrylamide.

[0031] In the preparation method of the starch-based polymer, the amount of water in step (1) is 5-20 parts, and preferably 8-16 parts.

[0032] The third aspect of the present application also provides the use of the above-mentioned starch-based polymer in water-based mud, especially in high-temperature and high-salt water-based mud drilling, the starch-based polymer can play a good salt-resistant and temperature-resistant filtration reduction effect at an addition amount of 0.5-3 wt%, and has the characteristics of environmental protection, lubrication, low cost and easy storage, and is suitable for application in deep well high-salt brine formation and other complex well drilling.

[0033] Compared with the prior art, the starch-based polymer and the preparation method thereof provided by the present application have the following advantages:

[0034] 1. The starch-based polymer has a temperature resistance of ≥180℃, a high-temperature and high-pressure filtration loss (HTHP) of ≤25 mL, a NaCl resistance of ≥300000 mg / L, and a divalent salt resistance of ≥50000 mg / L, and has good salt-resistant and temperature-resistant filtration reduction performance, and has the characteristics of environmental protection, lubrication, good water solubility, low cost and easy storage.

[0035] 2. The starch-based polymer is prepared by explosive polymerization, and in the preparation method, first, isoamylase is used as a debranching agent to hydrolyze the α-1, 6-glycosidic bond of the starch branch to obtain straight-chain starch with a smaller molecular weight, which is easy to graft copolymerization and has a weak polymerization inhibition effect. Then, a plasticizer is added for kneading to further stretch the starch molecular chain, and then acrylamide, a functional monomer, N, N-methylenebisacrylamide, water and an initiator are added to initiate explosive polymerization at a lower initial temperature to form a high-temperature resistant starch-based polymer. The debranching and plasticizing treatment in the early stage of polymerization reduces the molecular weight, steric hindrance and polymerization inhibition effect of the branched starch, improves the polymerization activity of the starch molecular chain, avoids the self-polymerization of monomers due to the high polymerization rate after the initiation of explosive polymerization, and generates a blend of high molecular polymers and branched starch, thereby ensuring the effective copolymerization.

[0036] 3. In the preparation method of the starch-based polymer, the semi-dry explosive polymerization method shortens the reaction time and improves the synthesis efficiency. The heat released in the rapid polymerization process causes the water content in the system to evaporate rapidly, and the starch graft copolymer obtained after polymerization can be extruded and granulated due to the low water content, and can be completely dehydrated and packaged after a short drying, which greatly reduces the large energy consumption in the preparation of starch graft copolymer powder, reduces the overall cost of the process, and is also beneficial to the transportation and storage of the product.

[0037] 4. In the preparation method of the starch-based polymer, the debranching, starch plasticization, blending and explosive polymerization reactions are orderly integrated, the preparation conditions are simple and controllable, the starch raw material is widely available and low in cost, and the method is green and biodegradable, which is beneficial to the production and popularization and application of the technical method. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The infrared spectrum of the starch-based polymer prepared in Example 1 of the present application. Detailed Implementation

[0039] The following specific embodiments further describe the starch-based polymers involved in this invention, their preparation methods, and applications, but do not constitute a limitation on this invention.

[0040] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values ​​stated herein, and such ranges or values ​​should be understood to include values ​​close to such ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0041] All material ratios appearing in the following examples and comparative examples are mass fractions of the materials.

[0042] In this paper, the molecular composition and structure of the samples were qualitatively analyzed using a Bruker FTS-3000 Fourier transform infrared spectrometer, with a selected frequency collection range of 500–4000 cm⁻¹. -1 The scan was repeated 16 times. Based on the intensity, position, and shape of the absorption peaks in the spectrum, the types of functional groups contained in the sample molecule were determined, thereby confirming the structure of the sample.

[0043] Example 1

[0044] At room temperature (25℃, the same below), 100 parts corn starch and 1 part isoamylase (4000U / g) were added to a kneading reactor. During kneading, 12 parts water were sprayed on top. After thorough mixing, the mixture was cured at 50℃ for 35 minutes. At the same temperature, 6 parts polyethylene glycol 400 were added, and after kneading for 2.5 hours, the temperature was lowered to 25℃. 3.5 parts potassium persulfate were added, and after thorough mixing, 150 parts acrylamide, 50 parts N,N-dimethylallylamine propanesulfonate, 0.15 parts N,N-methylenebisacrylamide, and 28 parts water were added. The temperature was raised to 45℃, and heating was stopped after the burst polymerization reaction occurred. The reaction continued for 40 minutes, and the temperature inside the reactor was adjusted to 50℃. The mixture was then extruded and granulated at the same temperature to obtain white starch-based polymer A. This polymer was dried at 115℃ for 1 hour, then packaged and sealed. The infrared spectrum of the sample is shown below. Figure 1 The figure shows 3420cm. -1 The broadened band at 2930 cm⁻¹ represents the stretching vibration peak of the alcohol hydroxyl groups on starch; -1 The characteristic peak at 1080 cm⁻¹ is the antisymmetric stretching vibration peak of the methylene group (-CH₂-). The -CH₂- group on the starch graft polymer molecular chain belongs to the starch molecule structure, or it can be attributed to the -CH₂- group generated by free radical polymerization of vinyl groups; -1 and 1150cm -1The characteristic peaks at 1660 cm -1 The characteristic peaks at 1660 cm -1 The characteristic peaks at 1660 cm

[0045] Example 2

[0046] A kneading reactor was charged with 100 parts of mung bean starch, 1.5 parts of isoamylase (2000 U / g) at room temperature, and 20 parts of water was sprayed during kneading. After being mixed thoroughly, it was cured at 70°C for 10 min. 10 parts of ethylene glycol was added at the same temperature, and kneaded for 0.5 h, then reduced to 35°C. 6 parts of ammonium persulfate was added, mixed thoroughly, and then 240 parts of acrylamide, 20 parts of methacryloyloxyethyl-N,N-dimethylpropanesulfonate, 0.25 parts of N,N-methylene bisacrylamide and 40 parts of water were added. The temperature was raised to 50°C, and after the polymerization reaction occurred, the heating was stopped, and the reaction was continued for 20 min. The temperature in the reactor was adjusted to 60°C, and then extruded and granulated at the same temperature to obtain white starch-based polymer B. After being dried at 120°C for 0.5 h, it was sealed in a bag.

[0047] Example 3

[0048] A kneading reactor was charged with 100 parts of mung bean starch, 1.5 parts of isoamylase (2000 U / g) at room temperature, and 20 parts of water was sprayed during kneading. After being mixed thoroughly, it was cured at 70°C for 10 min. 10 parts of ethylene glycol was added at the same temperature, and kneaded for 0.5 h, then reduced to 35°C. 6 parts of ammonium persulfate was added, mixed thoroughly, and then 240 parts of acrylamide, 20 parts of methacryloyloxyethyl-N,N-dimethylpropanesulfonate, 0.25 parts of N,N-methylene bisacrylamide and 40 parts of water were added. The temperature was raised to 50°C, and after the polymerization reaction occurred, the heating was stopped, and the reaction was continued for 20 min. The temperature in the reactor was adjusted to 60°C, and then extruded and granulated at the same temperature to obtain white starch-based polymer B. After being dried at 120°C for 0.5 h, it was sealed in a bag.

[0049] Example 4

[0050] To a mixing reactor was added 100 parts of cassava starch, 1.25 parts of isoamylase (3000 U / g) at room temperature, 16 parts of water was sprayed during the kneading process, after fully mixed, it was cured at 60°C for 20 min. 8 parts of potassium chloride was added at the same temperature, after kneading for 1 h, it was decreased to 30°C. 5 parts of initiator (sodium persulfate: ammonium persulfate = 1:1) was added after fully mixed, 180 parts of acrylamide, 30 parts of diethyl allyl phosphonate, 0.2 parts of N,N-methylene bisacrylamide and 34 parts of water was added, the temperature was increased to 48°C, after the explosive polymerization reaction occurred, the heating was stopped, the reaction was continued for 30 min, then the temperature in the reactor was adjusted to 57°C, at the same temperature, it was extruded and granulated, a light yellow starch-based polymer D was obtained, which was briefly dried at 116°C for 1 h and then sealed in a bag.

[0051] Example 5

[0052] To a mixing reactor was added 100 parts of potato starch, 0.75 parts of isoamylase (5000 U / g) at room temperature, 8 parts of water was sprayed during the kneading process, after fully mixed, it was cured at 40°C for 40 min. 2 parts of glycerol mono fatty acid ester was added at the same temperature, after kneading for 3 h, it was decreased to 20°C. 1 part of initiator (potassium persulfate: ammonium persulfate = 3:1) was added after fully mixed, 60 parts of acrylamide, 70 parts of 2-methyl-2-acrylamidopropyl phosphonic acid, 0.1 parts of N,N-methylene bisacrylamide and 24 parts of water was added, the temperature was increased to 42°C, after the explosive polymerization reaction occurred, the heating was stopped, the reaction was continued for 50 min, then the temperature in the reactor was adjusted to 44°C, it was briefly dried at 90°C for 1.5 h and then sealed in a bag.

[0053] Comparative Example 1

[0054] To a mixing reactor was added 100 parts of corn starch, 1 part of isoamylase (4000 U / g) at room temperature, 12 parts of water was sprayed during the kneading process, after fully mixed, it was cured at 50°C for 35 min. 6 parts of polyethylene glycol 400 was added at the same temperature, after kneading for 2.5 h, it was decreased to 25°C. 3.5 parts of potassium persulfate was added after fully mixed, 150 parts of acrylamide, 50 parts of N,N-dimethylallylamine propyl sulfonate and 28 parts of water was added, the temperature was increased to 45°C, after the explosive polymerization reaction occurred, the heating was stopped, the reaction was continued for 40 min, then the temperature in the reactor was adjusted to 50°C, at the same temperature, it was extruded and granulated, a white starch-based polymer a was obtained, which was briefly dried at 115°C for 1 h and then sealed in a bag.

[0055] Comparative Example 2

[0056] A mixing reactor was charged with 100 parts of corn starch and 1 part of isoamylase (4000 U / g) at room temperature. 12 parts of water were sprayed during kneading. After thorough mixing, the temperature was maintained at 50°C for 35 min and then lowered to 25°C. 3.5 parts of potassium persulfate were added and mixed thoroughly. Then 150 parts of acrylamide, 50 parts of N,N-dimethylallylamine propyl sulfonate, 0.15 parts of N,N-methylene bisacrylamide and 28 parts of water were added. The temperature was raised to 45°C. After the explosive polymerization reaction occurred, the heating was stopped. The temperature in the reactor was adjusted to 50°C. The extrusion and granulation were carried out at the same temperature. A white starch-based polymer b was obtained. It was dried at 115°C for 1 h and then sealed in a bag.

[0057] Comparative Example 3

[0058] A mixing reactor was charged with 100 parts of corn starch at room temperature. 12 parts of water were sprayed during kneading. After thorough mixing, the temperature was maintained at 50°C for 35 min. 6 parts of polyethylene glycol 400 were added at the same temperature. Kneading was carried out for 2.5 h and then the temperature was lowered to 25°C. 3.5 parts of potassium persulfate were added and mixed thoroughly. Then 150 parts of acrylamide, 50 parts of N,N-dimethylallylamine propyl sulfonate, 0.15 parts of N,N-methylene bisacrylamide and 28 parts of water were added. The temperature was raised to 45°C. After the explosive polymerization reaction occurred, the heating was stopped. The temperature in the reactor was adjusted to 50°C. The extrusion and granulation were carried out at the same temperature. A light yellow starch-based polymer c was obtained. It was dried at 115°C for 1 h and then sealed in a bag.

[0059] Performance test

[0060] 1. API filtration loss test

[0061] The performance of the starch-based polymers obtained in Examples 1-5 and Comparative Examples 1-3 was evaluated using a medium temperature and pressure filtration instrument. Experimental instruments: medium temperature and pressure filtration instrument, stirrer, settling kettle, roller-type heating furnace. Experimental materials: prepared drilling fluid, samples obtained in Examples 1-5, samples obtained in Comparative Examples 1-3.

[0062] Experimental steps:

[0063] In a high-speed stirring cup, 400 mL of distilled water was added, 120 g of sodium chloride was added, and after dissolution under stirring, 40 g of bentonite for drilling fluid test slurry and 1.5 g (accurate to 0.01 g) of anhydrous sodium bicarbonate were slowly added under stirring at a speed of (11000±300) r / min. High-speed stirring was carried out for 20 min. The sodium chloride brine-based slurry was obtained after being sealed and maintained at room temperature for 24 h. A total of 2 portions of the base slurry were prepared.

[0064] Take two 400 mL of the above base paste, add 12.0 g of the sample (3 wt%) to one of them, high-speed stir at (11000 ± 300) r / min for 20 min, pour into the aging tank, put it into the high-temperature roller oven at 180°C for 16 h, then take it out, cool to room temperature, high-speed stir for 5 min, and measure the medium-pressure filtration loss according to the provisions in GB / T 16783.1. Calculate the filtration loss reduction rate according to formula (1).

[0065]

[0066] In the formula:

[0067] f - filtration loss reduction rate;

[0068] FL0 - filtration loss of base paste, mL;

[0069] FL - filtration loss of sample-containing paste, mL.

[0070] Use the above steps to test the sample's resistance to divalent salt performance, and adjust "add 120 g of sodium chloride" to "add 10 g of calcium chloride and 10 g of magnesium chloride", and the rest of the steps remain unchanged.

[0071] Experimental results:

[0072] The filtration loss reduction rate of the drilling fluid was evaluated 30 min after the start of the experiment. The results of the sodium salt resistance temperature resistance experiment are shown in Table 1, and the results of the calcium salt resistance temperature resistance experiment are shown in Table 2.

[0073] Table 1 Evaluation of filtration loss resistance to sodium salt

[0074] Item FL0 FL f Example 1 78.2 7.2 90.79％ Example 2 73.5 11.5 84.35％ Example 3 69.6 9.4 86.49％ Example 4 75.4 8.6 88.59％ Example 5 76.2 9.3 87.80％ Comparative Example 1 79.3 40.1 49.43％ Comparative Example 2 71.5 38.2 46.57％ Comparative Example 3 80.2 42.0 47.63％

[0075] Table 2 Evaluation of filtration loss resistance to divalent salt

[0076]

[0077]

[0078] 2. High temperature and high pressure filtration loss test (HTHP)

[0079] Take two high-speed stirring cups, add 400 mL of distilled water and 0.96 g (accurately weighed to 0.01 g) of anhydrous sodium carbonate to each, and after dissolving, slowly add 16.0 g (accurately weighed to 0.01 g) of bentonite for drilling fluid test paste under high-speed stirring, high-speed stir for 20 min, and then seal and maintain at 25°C ± 1°C for 24 h as the base paste. Take one cup of the maintained base paste, high-speed stir for 5 min, and measure the high temperature and high pressure filtration loss of the base paste at 180°C and a pressure difference of 3.45 MPa according to the test procedure specified in GB / T 16783.1.

[0080] Take another cup of base paste, slowly add 12.0 g (3 wt%) of the sample under high-speed stirring, after high-speed stirring for 20 min, seal and maintain at 25℃±1℃ for 24 h, as sample paste. According to the test procedure specified in GB / T 16783.1, the high temperature and high pressure filtration loss of the sample paste is determined at 180℃ and a pressure difference of 3.45 MPa, and the results are shown in Table 3. FL1 and FL2 are the high temperature and high pressure filtration losses of the base paste and the sample paste, respectively.

[0081] Table 3: Evaluation of high temperature and high pressure filtration loss

[0082]

[0083]

[0084] As shown in Tables 1, 2 and 3, the salt and halide resistance of the starch-based polymers prepared in Examples 1-5 is good, and the reduction rates of the medium pressure filtration losses in the presence of sodium salt and divalent salt are both higher than 80%. The salt and temperature resistance of the samples prepared in Comparative Examples 1-3 is weak, and the reduction rates of the medium pressure filtration losses are all lower than 50%. The high temperature and high pressure filtration losses of the starch-based polymers prepared in Examples 1-5 are all less than 20 mL, with the lowest being only 13.2 mL. In comparison, the high temperature and high pressure filtration losses of the samples prepared in Comparative Examples 1-3 are all higher than 35 mL, with the highest being 48.2 mL, and the high temperature and pressure resistance is relatively weak.

Claims

1. A method for preparing a starch-based polymer, the method comprising the following steps: (1) Under contact conditions, starch and amylase are mixed together, water is introduced at the same time, and after mixing, they are cured. (2) Add plasticizer to the material obtained in step (1), mix well and cool; (3) Add an initiator, acrylamide, functional monomer, N,N-methylenebisacrylamide and water to the material obtained in step (2) to carry out a burst polymerization reaction. After the reaction is completed, the material is further subjected to optional molding and drying treatment to obtain a starch-based polymer; the functional monomer is a sulfonic acid monomer and / or a phosphonic acid monomer. The amounts of starch, water, amylase, plasticizer, initiator, acrylamide, functional monomer, and N,N-methylenebisacrylamide, by weight, are as follows: 100 parts starch, 20-60 parts water, 0.5-1.5 parts amylase, 0.5-10 parts plasticizer, 0.6-6 parts initiator, 40-240 parts acrylamide, 20-80 parts functional monomer, and 0.05-0.25 parts N,N-methylenebisacrylamide.

2. The method for preparing the starch-based polymer according to claim 1, wherein, The temperature for curing in step (1) is 30-70℃.

3. The method for preparing the starch-based polymer according to claim 1, wherein, The temperature for curing in step (1) is 40-60℃.

4. The method for preparing the starch-based polymer according to claim 1, wherein, The starch in step (1) is one or more of the following: mung bean starch, tapioca starch, sweet potato starch, potato starch, wheat starch, water chestnut starch, lotus root starch, and corn starch.

5. The method for preparing the starch-based polymer according to claim 1, wherein, The starch in step (1) is corn starch and / or potato starch.

6. The method for preparing the starch-based polymer according to claim 1, wherein, The amylase in step (1) is an isoamylase with a specific activity of 2000-6000 U / g substrate.

7. The method for preparing the starch-based polymer according to claim 1, wherein, The plasticizer in step (2) is one or more of the following: polyol, amine, inorganic salt containing group IA metal, polymeric alcohol, and polyester.

8. The method for preparing the starch-based polymer according to claim 7, wherein, The polyol is a C2-C6 polyol, which is one or more of ethylene glycol, glycerol, sorbitol, mannitol, and erythritol; the amine is one or more of urea, thiourea, and formamide; the inorganic salt containing group IA metals is one or more of sodium chloride, sodium bromide, sodium sulfate, sodium sulfite, sodium carbonate, sodium bicarbonate, sodium nitrate, sodium phosphate, sodium hydrogen phosphate, sodium silicate, potassium chloride, potassium bromide, potassium sulfate, potassium sulfite, potassium carbonate, potassium bicarbonate, potassium nitrate, potassium phosphate, and potassium hydrogen phosphate; the polymeric alcohol is selected from at least one of polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 1000, and polyethylene glycol 2000; the polyester is selected from one or more of glycerol monofatty acid ester, 1-ethyl-3-methylimidazolium acetate, polylactic acid, polybutylene succinate, polycaprolactone, and polybutylene adipate.

9. The method for preparing the starch-based polymer according to claim 1, wherein, In step (2), cool to 15-35°C.

10. The method for preparing the starch-based polymer according to claim 1, wherein, In step (2), cool to 20-30°C.

11. The method for preparing the starch-based polymer according to claim 1, wherein, The initiator in step (3) is any one or more of potassium persulfate, sodium persulfate, and ammonium persulfate.

12. The method for preparing the starch-based polymer according to claim 1, wherein, The functional monomer in step (3) is one or more of the following: methacryloyloxyethyl-N,N-dimethylpropanesulfonate, N,N-dimethylallylaminepropanesulfonate, 4-vinylpyridinepropanesulfonate, N-methyldiallylpropanesulfonate, N-methyldiallylbutanesulfonate, 2-methyl-2-acryloylaminopropanesulfonic acid, sodium 2-acryloyloxyisopentenesulfonate, sodium allylsulfonate, sodium styrenesulfonate, allylphosphonic acid, (2-methylallyl)phosphonic acid diethyl ester, allylphosphonic acid diethyl ester, allylphosphonic acid dimethyl ester, vinylphosphonic acid, 2-methylvinylphosphonic acid, and 2-methyl-2-acryloylaminopropanephosphonic acid.

13. The method for preparing the starch-based polymer according to claim 1, wherein, The reaction temperature in step (3) is 40-50℃ and the reaction time is 20-60 min.

14. The method for preparing the starch-based polymer according to claim 1, wherein, In step (3), heating is stopped after the explosive polymerization reaction occurs.

15. The method for preparing the starch-based polymer according to claim 1, wherein, The drying temperature in step (3) is 80-120℃ and the drying time is 0.5-2h.

16. The method for preparing the starch-based polymer according to claim 1, wherein, The amounts of starch, water, amylase, plasticizer, initiator, acrylamide, functional monomer, and N,N-methylenebisacrylamide, by weight, are as follows: 100 parts starch, 30-50 parts water, 0.75-1.25 parts amylase, 2-8 parts plasticizer, 1-5 parts initiator, 60-180 parts acrylamide, 30-70 parts functional monomer, and 0.1-0.2 parts N,N-methylenebisacrylamide.

17. The method for preparing the starch-based polymer according to claim 1, wherein, The amount of water used in step (1) is 5 to 20 parts.

18. The method for preparing the starch-based polymer according to claim 1, wherein, The amount of water used in step (1) is 8 to 16 parts.

19. The starch-based polymer obtained by the preparation method according to any one of claims 1-18, wherein, by weight, the starch-based polymer raw material comprises the following components: 100 parts starch, 20-60 parts water, 0.5-1.5 parts amylase, 0.5-10 parts plasticizer, 0.6-6 parts initiator, 40-240 parts acrylamide, 20-80 parts functional monomer, and 0.05-0.25 parts N,N-methylenebisacrylamide; the functional monomer is a sulfonic acid monomer and / or a phosphonic acid monomer.

20. The starch-based polymer according to claim 19, wherein, The starch-based polymer raw material includes the following components: 100 parts starch, 30-50 parts water, 0.75-1.25 parts amylase, 2-8 parts plasticizer, 1-5 parts initiator, 60-180 parts acrylamide, 30-70 parts functional monomer, and 0.1-0.2 parts N,N-methylenebisacrylamide.

21. The starch-based polymer according to claim 19, wherein, The amylase mentioned is an isoamylase, with a specific activity of 2000–6000 U / g substrate.

22. The starch-based polymer according to claim 19, wherein, The plasticizer is one or more of polyols, amines, inorganic salts containing Group IA metals, polymeric alcohols, and polyesters; wherein the polyol is a C2-C6 polyol, and is one or more of ethylene glycol, glycerol, sorbitol, mannitol, and erythritol; the amine is one or more of urea, thiourea, and formamide; the inorganic salt containing Group IA metals is one or more of sodium chloride, sodium bromide, sodium sulfate, sodium sulfite, sodium carbonate, sodium bicarbonate, sodium nitrate, sodium phosphate, sodium hydrogen phosphate, sodium silicate, potassium chloride, potassium bromide, potassium sulfate, potassium sulfite, potassium carbonate, potassium bicarbonate, potassium nitrate, potassium phosphate, and potassium hydrogen phosphate; the polymeric alcohol is selected from at least one of polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 1000, and polyethylene glycol 2000; and the polyester is selected from glycerol monofatty acid esters and 1-ethyl-3-ethylhexylene glycol. One or more of the following: methyl imidazole acetate, polylactic acid, polybutylene succinate, polycaprolactone, and polybutylene terephthalate.

23. The starch-based polymer according to claim 19, wherein, Starch is one or more of the following: mung bean starch, tapioca starch, sweet potato starch, potato starch, wheat starch, water chestnut starch, lotus root starch, and corn starch.

24. The starch-based polymer according to claim 19, wherein, The starch is corn starch and / or potato starch.

25. The starch-based polymer according to claim 19, wherein, The functional monomer is one or more of the following: methacryloyloxyethyl-N,N-dimethylpropanesulfonate, N,N-dimethylallylaminepropanesulfonate, 4-vinylpyridinepropanesulfonate, N-methyldiallylpropanesulfonate, N-methyldiallylbutanesulfonate, 2-methyl-2-acryloylaminopropanesulfonic acid, sodium 2-acryloyloxyisopentenesulfonate, sodium allylsulfonate, sodium styrenesulfonate, allylphosphonic acid, diethyl (2-methylallyl)phosphonate, diethyl allylphosphonate, dimethyl allylphosphonate, vinylphosphonic acid, 2-methylvinylphosphonic acid, and 2-methyl-2-acryloylaminopropionylphosphonic acid.

26. The starch-based polymer according to claim 19, wherein, The initiator is any one or two of potassium persulfate, sodium persulfate, and ammonium persulfate.

27. The starch-based polymer according to claim 19, wherein, The starch-based polymer has a temperature resistance of ≥180℃, a high-temperature and high-pressure filtration loss (HTHP) of ≤25mL, a NaCl resistance of ≥300000mg / L, and a divalent salt resistance of ≥50000mg / L.

28. The use of the starch-based polymer according to any one of claims 19-27 in water-based mud drilling and production.

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