CN109422887B

CN109422887B - Anionic starch microsphere and preparation method and application thereof

Info

Publication number: CN109422887B
Application number: CN201710720844.7A
Authority: CN
Inventors: 韩洁; 赵林; 杨超; 王晨
Original assignee: China Petroleum and Chemical Corp; Sinopec Dalian Research Institute of Petroleum and Petrochemicals
Current assignee: Sinopec Dalian Petrochemical Research Institute Co ltd; China Petroleum and Chemical Corp
Priority date: 2017-08-22
Filing date: 2017-08-22
Publication date: 2020-11-10
Anticipated expiration: 2037-08-22
Also published as: CN109422887A

Abstract

The invention discloses an anionic starch microsphere and a preparation method and application thereof, wherein the raw materials of the anionic starch microsphere comprise the following components: 100 parts of deionized water, 1-20 parts of starch, 10-50 parts of triethanolamine, 0.105-14.6 parts of epoxy chloropropane, 0.1-20 parts of anionic monomer, 0.001-0.2 part of initiator, 0.05-10 parts of zwitterionic surfactant and 0.5-200 parts of inorganic salt solution. The particle size of the starch microspheres is 0.1-500 mu m, and the starch microspheres have uniformly distributed polydispersity. The prepared anionic starch microspheres are polydisperse starch microspheres with uniformly distributed particle sizes.

Description

Anionic starch microsphere and preparation method and application thereof

Technical Field

The invention belongs to the technical field of microspheres, and particularly relates to an anionic starch microsphere as well as a preparation method and application thereof.

Background

The shielding temporary plugging protection oil-gas layer drilling technology (shielding temporary plugging technology for short) is mainly used for solving the problem that a multi-pressure layer system stratum of an open hole well section protects an oil-gas layer, namely two adverse factors (pressure difference and drilling fluid solid-phase particles) which damage the oil-gas layer in the process of drilling into the oil-gas layer are utilized to convert the adverse factors into the advantageous factors for protecting the oil-gas layer, and the purpose of reducing the damage of the drilling fluid, cement paste, the pressure difference and the bubble invasion time to the oil-gas layer is achieved.

The basic idea of the shielding temporary plugging protection oil-gas reservoir drilling technology is that when an oil-gas reservoir is drilled, the pressure difference formed between the pressure of a drilling fluid liquid column and the pressure of the oil-gas reservoir forces solid particles of types and sizes artificially added in the drilling fluid to enter the pore throat of the oil-gas reservoir in a very short time, a plugging zone is quickly, shallowly and effectively formed near a well wall, the drilling fluid is prevented from continuously invading the oil-gas reservoir, and the damage of the drilling fluid to the oil-gas reservoir is reduced. Its thickness must be much less than the perforation depth in order to unblock through the perforations when the completion is put into production. After drilling is completed, if the open hole is completed, the blocking zone can be eliminated by means of acidification and the like, so that the original permeability of an oil-gas layer is recovered, and the oil-gas well is ensured to have better yield.

The microsphere compound is a more common temporary plugging agent for protecting oil and gas reservoirs at present, wherein the starch microsphere is also widely researched. The prior art has more researches on monodisperse or polydisperse starch microspheres, and patents CN201010546156.1 and CN201410236878.5 describe two preparation methods of monodisperse starch microspheres. CN201510151917.6 describes a preparation method of nano-scale polydisperse starch microspheres. CN201510175382.6 provides a method for preparing polymer microspheres with particle size gradient characteristics. There are few reports on uniformly distributed polydisperse starch microspheres.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides an anionic starch microsphere and a preparation method and application thereof.

The first aspect of the invention provides an anionic starch microsphere, which comprises the following raw materials in parts by weight: 100 parts of deionized water, 1-20 parts of starch, 10-50 parts of triethanolamine, 0.105-14.6 parts of epoxy chloropropane, 0.1-20 parts of anionic monomer, 0.001-0.2 part of initiator, 0.05-10 parts of zwitterionic surfactant and 0.5-200 parts of inorganic salt solution, wherein the inorganic salt solute accounts for 0.025-50 parts.

In the anionic starch microspheres, the raw materials of the anionic starch microspheres comprise the following components in parts by weight: 100 parts of deionized water, 5-15 parts of starch, 20-40 parts of triethanolamine, 1.04-7.8 parts of epoxy chloropropane, 5-15 parts of anionic monomer, 0.02-0.105 part of initiator, 1-6 parts of zwitterionic surfactant and 50-150 parts of inorganic salt solution, wherein the inorganic salt solute accounts for 0.5-30 parts.

In the anionic starch microspheres, the controllable range of the particle size of the starch microspheres is 0.1-500 μm, the particle size of the starch microspheres is in a particle size concentrated distribution interval (wherein the particle size concentrated distribution interval is defined as a continuous interval in which the proportion of particle size distribution is greater than or equal to 90% except particle size boundaries at two ends, and the particle size concentrated distribution interval is the particle size distribution diagramThe distribution is approximately in a straight line distribution, excluding the areas with obvious inflection points at two ends), the particle size distribution in the particle size concentrated distribution interval has the following characteristics: evenly dividing the particle size concentrated distribution interval into n intervals, wherein the ratio of the microspheres in each interval is as follows:

wherein n is an integer greater than 1.

In the anionic starch microspheres, the anionic monomer can be one or more of AA (acrylic acid), AMPS (2-methyl-2-acrylamidopropanesulfonic acid), FA (fumaric acid), SSS (sodium allylsulfonate) and AOIAS (sodium 2-acryloyloxy isopentene sulfonate).

In the anionic starch microspheres, the starch is one or more of mung bean starch, cassava starch, sweet potato starch, wheat starch, water chestnut starch, lotus root starch and corn starch, and preferably corn starch and/or potato starch.

In the anionic starch microsphere, the initiator is any one of potassium persulfate, sodium persulfate and ammonium persulfate.

In the anionic starch microsphere, the structure of the zwitterionic surfactant is as follows:

wherein: n is an integer between 2 and 6, preferably n is 3 or 4; r is a carbon chain having 1 to 18 carbon atoms, preferably 12 to 18 carbon atoms. The carbon chain is a saturated carbon chain and can be a straight chain or a branched chain. The carbon chain (excluding the terminal carbon) may contain substituted hydroxyl, amino or carboxyl groups, and the same carbon may be monosubstituted. The zwitterionic surfactant can be one or more of dimethyl dodecyl sulfopropyl ammonium salt, dimethyl hexadecyl sulfoethyl ammonium salt, dimethyl octadecyl sulfobutyl ammonium salt, dimethyl (3-hydroxyl dodecyl) sulfopropyl ammonium salt and dimethyl (6-amino tetradecyl) sulfoethyl ammonium salt.

In the anionic starch microspheres, the inorganic salt is a soluble inorganic salt, the inorganic salt is one or more of sodium salt, potassium salt, ammonium salt, calcium salt and magnesium salt, and when the inorganic salt is sodium salt, the inorganic salt is specifically one or more of sodium chloride, sodium bromide, sodium sulfate, sodium sulfite, sodium carbonate, sodium bicarbonate, sodium nitrate, sodium phosphate, sodium hydrogen phosphate and sodium silicate; when the inorganic salt is potassium salt, the inorganic salt is one or more of potassium chloride, potassium bromide, potassium sulfate, potassium sulfite, potassium carbonate, potassium bicarbonate, potassium nitrate, potassium phosphate, potassium hydrogen phosphate and potassium silicate; when the inorganic salt is ammonium salt, the inorganic salt is one or more of ammonium chloride, ammonium bromide and ammonium nitrate; when the inorganic salt is a calcium salt, it is specifically calcium chloride or calcium bromide; when the inorganic salt is a magnesium salt, the inorganic salt is specifically one or more of magnesium chloride, magnesium bromide, magnesium sulfate and magnesium nitrate.

The second aspect of the present invention provides a preparation method of the above anionic starch microspheres, which comprises the following steps:

(1) weighing a certain amount of starch, adding the starch into water, adding a certain amount of triethanolamine, fully and uniformly mixing at 20-80 ℃, and adding epoxy chloropropane for reaction;

(2) adding an anionic monomer into the starch solution obtained in the step (1), fully dissolving and uniformly mixing, adding an initiator, and reacting for 3-6 hours at the temperature of 60-80 ℃;

(3) adding a zwitterionic surfactant into the feed liquid obtained in the step (2), and uniformly mixing;

(4) and (3) slowly adding an inorganic salt solution and epoxy chloropropane into the feed liquid obtained in the step (2) at a constant speed at the temperature of 30-60 ℃, and continuing to react for a period of time after the inorganic salt solution and the epoxy chloropropane are added, so as to obtain the starch microspheres.

In the method, the starch in the step (1) is one or more of mung bean starch, cassava starch, sweet potato starch, wheat starch, water chestnut starch, lotus root starch and corn starch, and preferably corn starch and/or potato starch.

In the method, the temperature in the step (1) is 20-80 ℃, and preferably 30-60 ℃; the reaction time is 0.5-4 h, preferably 1-3 h.

In the method of the present invention, the initiator in the step (2) may be any one of potassium persulfate, sodium persulfate, and ammonium persulfate.

In the method, the anionic monomer in the step (2) is one or more of AA (acrylic acid), AMPS (2-methyl-2-acrylamidopropanesulfonic acid), FA (fumaric acid), SSS (sodium allylsulfonate) and AOIAS (sodium 2-acryloyloxy isopentene sulfonate).

In the method of the present invention, the zwitterionic surfactant described in step (3) has the following structure:

In the method, the inorganic salt in the step (4) is soluble inorganic salt, the inorganic salt is one or more of sodium salt, potassium salt, ammonium salt, calcium salt and magnesium salt, and when the inorganic salt is sodium salt, the inorganic salt is specifically one or more of sodium chloride, sodium bromide, sodium sulfate, sodium sulfite, sodium carbonate, sodium bicarbonate, sodium nitrate, sodium phosphate, sodium hydrogen phosphate and sodium silicate; when the inorganic salt is potassium salt, the inorganic salt is one or more of potassium chloride, potassium bromide, potassium sulfate, potassium sulfite, potassium carbonate, potassium bicarbonate, potassium nitrate, potassium phosphate, potassium hydrogen phosphate and potassium silicate; when the inorganic salt is ammonium salt, the inorganic salt is one or more of ammonium chloride, ammonium bromide and ammonium nitrate; when the inorganic salt is a calcium salt, it is specifically calcium chloride or calcium bromide; when the inorganic salt is a magnesium salt, the inorganic salt is specifically one or more of magnesium chloride, magnesium bromide, magnesium sulfate and magnesium nitrate.

In the method, the amounts of the deionized water, the starch, the triethanolamine, the epichlorohydrin, the anionic monomer, the initiator, the zwitterionic surfactant and the inorganic salt solution are respectively as follows in parts by weight: 100 parts of deionized water, 1-20 parts of starch, 10-50 parts of triethanolamine, 0.105-14.6 parts of epoxy chloropropane, 0.1-20 parts of anionic monomer, 0.001-0.2 part of initiator, 0.05-10 parts of zwitterionic surfactant and 0.5-200 parts of inorganic salt solution (wherein inorganic salt solute accounts for 0.025-50 parts); preferably 100 parts of deionized water, 5-15 parts of starch, 20-40 parts of triethanolamine, 1.04-7.8 parts of epoxy chloropropane, 5-15 parts of anionic monomer, 0.02-0.105 part of initiator, 1-6 parts of zwitterionic surfactant and 50-150 parts of inorganic salt solution (wherein inorganic salt solute accounts for 0.5-30 parts).

In the method, the epoxy chloropropane in the step (1) is 0.005-0.6 part, preferably 0.04-3 parts.

In the method, the epoxy chloropropane in the step (4) is 0.1-14 parts, preferably 1-7.5 parts.

In the method of the present invention, the slow and uniform adding in the step (4) may be any method capable of realizing uniform solvent adding in the field, such as a dropwise adding method.

The third aspect of the invention also provides application of the anionic starch microspheres in a temporary plugging agent for protecting an oil-gas layer. The starch microspheres are used as a component in a drilling fluid system to play a role in shielding and temporary plugging. The addition amount of 0.5-5 wt% can achieve good effect. The drilling fluid added with the microspheres has good plugging capability, can effectively plug pores or microcracks to form compact mud cakes, prevents a large amount of filtrate from permeating into a stratum, and reduces the filtration loss.

Compared with the prior art, the anionic starch microsphere and the preparation method thereof have the following advantages:

1. the anionic starch microspheres are polydisperse microspheres with uniformly distributed particle sizes, and are different from monodisperse and polydisperse starch microspheres prepared by the prior art. When the starch microspheres are applied to the field of temporary plugging agents for protecting oil and gas reservoirs, due to the fact that geological structures are different, the porosity span of the reservoirs is large, and if the microspheres with monodisperse particle sizes are used, the requirement on broad spectrum is difficult to meet, and the using effect cannot meet the industrial requirement. In addition, the existing polydisperse microspheres are normally distributed, the effective range of the particle size is narrow, and the effect is obviously limited. The uniformly distributed polydisperse starch microspheres provided by the technology can well solve the problems, namely, in any particle size interval, the microspheres have equivalent proportion, high microsphere content and obvious temporary plugging effect, and can meet the requirement of broad spectrum.

2. In the preparation method of the anionic starch microspheres, the structures of the straight chain part and the branched chain part in the starch are equivalent in size and have similar molecular sizes under the combined action of the triethanolamine and the epichlorohydrin, so that the prepared microspheres are easier to control, and the particle size distribution is uniform. The starch is then modified by copolymerization with anionic monomers to render it anionic. In the process of crosslinking starch into microspheres, by using a zwitterionic surfactant and simultaneously slowly adding inorganic salt and epichlorohydrin at a constant speed, under the combined action of the zwitterionic surfactant and the epichlorohydrin, the particle size of the prepared starch microspheres is linearly changed, and then the polydisperse starch microspheres with uniformly distributed particle sizes are prepared.

3. In the preparation method of the anionic starch microspheres, due to the addition of the anionic monomer, the salt resistance, temperature resistance and other properties of the microspheres are remarkably improved.

Detailed Description

The following examples further illustrate the anionic starch microspheres of the present invention, and methods of making and using the same, but are not intended to limit the invention thereto.

The particle size of the anionic starch microspheres in the embodiment of the invention is measured by a Malvern 3000 particle size analyzer, and the measuring method is wet measurement.

The particle size range (a μm-b μm) in all the examples and comparative examples below means a.ltoreq.D < b.

Example 1

11 parts of corn starch are weighed and added into 100 parts of deionized water, and then 21 parts of triethanolamine are added and fully dissolved at 40 ℃. Then 0.35 part of epoxy chloropropane is added, and the mixture is mixed and reacted for 2 hours. 6 parts of AMPS is weighed and added into the starch solution, and the mixture is fully dissolved and mixed. 0.22 part of ammonium persulfate is added at 80 ℃ and reacted for 6 hours. 6 parts of dimethylaminetetradecylsulfanylammonium salt are added and mixed thoroughly. Weighing 62 parts of KCl to prepare 130 parts of inorganic salt solution, dripping the inorganic salt solution and 2 parts of epichlorohydrin into the starch solution at the same time at 55 ℃, and dripping the solution at a constant speed for 5 hours. And continuously reacting for 2 hours after the dropwise adding is finished to obtain the uniformly distributed polydisperse starch microspheres. The starch microspheres have a particle size concentration distribution interval of 10-170 micrometers (92.9% of particle sizes are in the interval), and the particle size distribution in the particle size concentration distribution interval has the following characteristics: (10 μm-50 μm): 25.4 percent; (50 μm-90 μm): 24.6 percent; (90 μm-130 μm): 25.3 percent; (130 μm-170 μm): 24.7 percent.

Example 2

5 parts of potato starch are weighed into 100 parts of deionized water, and 16 parts of triethanolamine are added and fully dissolved at room temperature. Then 0.04 epichlorohydrin is added, and the mixture is mixed and reacted for 2 hours. Weighing 6 parts of AA, adding into the starch solution, and fully dissolving and mixing. 0.12 part of ammonium persulfate was added at 70 ℃ and reacted for 4 hours. 1 part of dimethylhexadecylsulfoethylammonium salt is added and mixed thoroughly. Weighing 0.5 part of CaCl₂Preparing 62 parts of inorganic salt solution, dripping the inorganic salt solution and 7.5 parts of epichlorohydrin into the starch solution at the same time at 60 ℃, and dripping the solution at a constant speed for 8 hours. And continuously reacting for 2 hours after the dropwise adding is finished to obtain the uniformly distributed polydisperse starch microspheres. The starch microspheres have a particle size concentration distribution interval of 120-240 microns (93.5% of particle sizes are in the interval), and the particle size distribution in the particle size concentration distribution interval has the following characteristics: (120 μm-190 μm): 24.1 percent; (190 μm-260 μm): 26 percent; (260 μm-330 μm): 24.8 percent; (330 μm-400 μm): 25.1 percent.

Example 3

Weighing 20 parts of cassava starch, adding100 parts of deionized water, 20 parts of triethanolamine were added and dissolved sufficiently at 40 ℃. Then 0.3 part of epoxy chloropropane is added, and the mixture is mixed and reacted for 1 hour. 5.5 parts of FA is weighed and added into the starch solution, and fully dissolved and mixed. 0.105 part of sodium persulfate was added thereto at 80 ℃ and reacted for 3 hours. 10 parts of dimethyloctadecyl sulfobutylammonium salt are added and mixed well. Weighing 29 parts of MgCl₂150 parts of inorganic salt solution is prepared, and is dripped into the starch solution at 40 ℃ together with 14 parts of epichlorohydrin for 10 hours at uniform speed. And continuously reacting for 2 hours after the dropwise adding is finished to obtain the uniformly distributed polydisperse starch microspheres. The starch microspheres have a particle size concentration distribution interval of 50-300 microns (95.2% of particle sizes are in the interval), and the particle size distribution in the particle size concentration distribution interval has the following characteristics: (50 μm-100 μm): 20.0 percent; (100 μm-150 μm): 18.7 percent; (150 μm-200 μm): 20.5 percent; (200 μm-250 μm): 20.0 percent; (250 μm-300 μm): 20.8 percent.

Example 4

Weighing 15 parts of mung bean starch, adding into 100 parts of deionized water, adding 40 parts of triethanolamine, and fully dissolving at 60 ℃. Then 0.6 part of epoxy chloropropane is added, and the mixture is reacted for 1.5 hours after being mixed. And weighing 20 parts of SSS, adding into the starch solution, and fully dissolving and mixing. 0.2 part of potassium persulfate was added thereto at 75 ℃ and reacted for 5 hours. 3.7 parts of dimethyl (3-hydroxydodecyl) sulfopropyl ammonium salt are added and mixed thoroughly. Weighing 30 parts of K₂SO₄Preparing 95 parts of inorganic salt solution, dripping the inorganic salt solution and 5 parts of epichlorohydrin into the starch solution at the same time at 30 ℃, and dripping the solution at a constant speed for 7 hours. And continuously reacting for 2 hours after the dropwise adding is finished to obtain the uniformly distributed polydisperse starch microspheres. The starch microspheres have a particle size concentration distribution interval of 150-500 microns (96.1% of particle sizes are in the interval), and the particle size distribution in the particle size concentration distribution interval has the following characteristics: (150 μm-200 μm): 14.7 percent; (200 μm-250 μm): 13.6 percent; (250 μm-300 μm): 15.4 percent; (300 μm-350 μm): 13.9 percent; (350 μm-400 μm): 14.7 percent; (400 μm-450 μm): 14.2 percent; (450 μm-500 μm): 13.5 percent.

Example 5

Weighing 1 part of sweet potato starch, adding into 100 parts of deionized water, adding 50 parts of triethanolamine, and fully dissolving at 50 ℃. Then 0.38 part of epoxy chloropropane is added, and the mixture is mixed and reacted for 2.5 hours. 0.1 part of AOIAS is weighed and added into the starch solution, and fully dissolved and mixed. 0.001 part of ammonium persulfate was added at 65 ℃ and reacted for 4 hours. 0.05 part of dimethyl (6-aminotetradecyl) sulfoethylammonium salt is added and mixed well. 0.025 part of NaCl is weighed to prepare 0.5 part of inorganic salt solution, and the inorganic salt solution and 0.1 part of epichlorohydrin are simultaneously dripped into the starch solution at the temperature of 55 ℃, and the dripping time is 9 hours at uniform speed. And continuously reacting for 2 hours after the dropwise adding is finished to obtain the uniformly distributed polydisperse starch microspheres. The concentrated particle size distribution interval of the starch microspheres is 0.1-6.7 microns (92.8% of particle size is in the interval), and the particle size distribution in the concentrated particle size distribution interval has the following characteristics: (0.1 μm-1.2 μm): 17.0 percent; (1.2 μm-2.3 μm): 15.5 percent; (2.3 μm-3.4 μm): 17.2 percent; (3.4 μm-4.5 μm): 17.0 percent; (4.5 μm-5.6 μm): 16.8 percent; (5.6 μm-6.7 μm): 16.5 percent.

Example 6

11 parts of starch (maize: mung bean =2: 1) are weighed into 100 parts of deionized water, and then 33 parts of triethanolamine are added and sufficiently dissolved at 72 ℃. Then 0.25 part of epoxy chloropropane is added, and the mixture is reacted for 0.5h after being mixed. 6.7 parts of AMPS are weighed out and added into the starch solution, and the mixture is fully dissolved and mixed. 0.014 part of potassium persulfate was added thereto at 68 ℃ and reacted for 5 hours. 6.8 parts of dimethyldodecylsulfobutylammonium salt are added and mixed thoroughly. 34 parts of inorganic salt (NaCl: CaCl) is weighed₂=1: 1) to prepare 70 parts of inorganic salt solution, dripping the inorganic salt solution and 12.5 parts of epichlorohydrin into the starch solution at the same time at 57 ℃, and dripping the solution at constant speed for 4.5 h. And continuously reacting for 2 hours after the dropwise adding is finished to obtain the uniformly distributed polydisperse starch microspheres. The concentrated particle size distribution interval of the starch microspheres is 70-270 mu m (97.8% of particle size is in the interval), and the particle size distribution in the concentrated particle size distribution interval has the following characteristics: (70 μm-110 μm): 19.8 percent; (110 μm-150 μm): 20.6 percent; (150 μm-190 μm): 20.1 percent; (190 μm-230 μm): 20.7 percent; (230 μm-270 μm): 18.8 percent.

Example 7

Weighing 18 parts of starch (cassava: corn =3: 1) and adding to 100 parts of deionized water, and then12 parts of triethanolamine were added and dissolved thoroughly at 65 ℃. Then 0.025 parts of epoxy chloropropane is added, and the mixture is mixed and reacted for 1.6 h. 3.1 parts of AMPS are weighed out and added into the starch solution, and the mixture is fully dissolved and mixed. 0.044 part of ammonium persulfate was added at 72 ℃ and reacted for 4 hours. 1.2 parts of dimethylhydroxyhexadecylsulfopropyl ammonium salt are added and mixed thoroughly. Weighing 12 parts of KNO₃Preparing 81 parts of inorganic salt solution, dripping the inorganic salt solution and 6 parts of epichlorohydrin into the starch solution at the same time at 45 ℃, and dripping the solution at a constant speed for 6 hours. And continuously reacting for 2 hours after the dropwise adding is finished to obtain the uniformly distributed polydisperse starch microspheres. The particle size concentrated distribution interval of the starch microspheres is 20-260 mu m (94.7% of particle size is in the interval), and the particle size distribution in the particle size concentrated distribution interval has the following characteristics: (20 μm-60 μm): 17.3 percent; (60 μm-100 μm): 16.2 percent; (100 μm-140 μm): 16.4 percent; (140 μm-180 μm): 17.4 percent; (180 μm-220 μm): 17.4 percent; (220 μm-260 μm): 15.3 percent.

Example 8

Weighing 2 parts of wheat starch, adding the wheat starch into 100 parts of deionized water, adding 35 parts of triethanolamine, and fully dissolving at 45 ℃. Then, 0.014 part of epichlorohydrin was added thereto, and the mixture was mixed and reacted for 2.75 hours. 4.7 parts of monomer (AMPS: AA =1: 1) were weighed into the starch solution, and thoroughly dissolved and mixed. 0.02 part of an initiator (sodium persulfate: potassium persulfate =1: 1) was added at 67.5 ℃ and reacted for 6 hours. 7.4 parts of dimethyldodecylsulfopropyl ammonium salt are added and mixed thoroughly. Weighing 6.5 parts of Na₂CO₃Preparing 115 parts of inorganic salt solution, dripping the inorganic salt solution and 4 parts of epichlorohydrin into the starch solution at the same time at 42 ℃, and dripping the solution at a constant speed for 6.5 hours. And continuously reacting for 2 hours after the dropwise adding is finished to obtain the uniformly distributed polydisperse starch microspheres. The concentrated particle size distribution range of the starch microspheres is 0.1-8.5 microns (94.3% of particle sizes are in the range), and the particle size distribution in the concentrated particle size distribution range has the following characteristics: (0.1 μm-1.5 μm): 16.4 percent; (1.5 μm-2.9 μm): 17.6 percent; (2.9 μm-4.3 μm): 17.1 percent; (4.3 μm-5.7 μm): 16.2 percent; (5.7 μm-7.1 μm): 17.6 percent; (7.1 μm-8.5 μm): 16.1 percent.

Comparative example 1

Adding 11 parts of corn starch into 100 parts of deionized water, and fully dissolving for 30min at 40 ℃ for later use. 6 parts of AMPS is weighed and added into the starch solution, and the mixture is fully dissolved and mixed. 0.22 part of ammonium persulfate is added at 80 ℃ and reacted for 6 hours. 6 parts of dimethylaminetetradecylsulfanylammonium salt are added and thoroughly dissolved and mixed. 2 parts of epichlorohydrin are weighed and added into the starch solution, and the continuous reaction time is 7 hours at 55 ℃. Obtaining the uniformly distributed polydisperse starch microspheres. The starch microspheres have a particle size concentration distribution interval of 120-400 microns (95.8% of particle sizes are in the interval), and the particle size distribution in the particle size concentration distribution interval has the following characteristics: (120 μm-170 μm): 11.6 percent; (170 μm-350 μm): 78.6 percent; (350 μm-400 μm): 9.8 percent.

Comparative example 2

Adding 11 parts of corn starch into 100 parts of deionized water, adding 21 parts of triethanolamine, and fully dissolving at 40 ℃.6 parts of AMPS is weighed and added into the starch solution, and the mixture is fully dissolved and mixed. 0.22 part of potassium persulfate was added thereto at 80 ℃ and reacted for 6 hours. Then, 6 parts of dimethylaminetetradecylsulfanylammonium salt are added and mixed thoroughly. Weighing 62 parts of KCl to prepare 130 parts of inorganic salt solution, dripping the inorganic salt solution and 2 parts of epichlorohydrin into the starch solution at the same time at 55 ℃, and dripping the solution at a constant speed for 5 hours. And continuously reacting for 2 hours after the dropwise adding is finished to obtain the uniformly distributed polydisperse starch microspheres. The particle size concentrated distribution interval of the starch microspheres is 20-180 mu m (94.4% of particle size is in the interval), and the particle size distribution in the particle size concentrated distribution interval has the following characteristics: (20 μm-60 μm): 31.7 percent; (60 μm-100 μm): 18.1 percent; (100 μm-140 μm): 19.2 percent; (140 μm-180 μm): 31.0 percent.

Comparative example 3

11 parts of corn starch are weighed and added into 100 parts of deionized water, and then 21 parts of triethanolamine are added and fully dissolved at 40 ℃. Then 0.35 part of epoxy chloropropane is added, and the mixture is mixed and reacted for 2 hours. 6 parts of AMPS is weighed and added into the starch solution, and the mixture is fully dissolved and mixed. 0.22 part of ammonium persulfate is added at 80 ℃ and reacted for 6 hours. 6 parts of dimethylaminetetradecylsulfanylammonium salt are added and mixed thoroughly. Weighing 62 parts of KCl to prepare 130 parts of inorganic salt solution, simultaneously adding the inorganic salt solution and 2 parts of epichlorohydrin into the starch solution at one time at 55 ℃, and continuously reacting for 7 hours to obtain the uniformly distributed polydisperse starch microspheres. The starch microspheres have a particle size concentration distribution interval of 10-210 micrometers (93.9% of particle sizes are in the interval), and the particle size distribution in the particle size concentration distribution interval has the following characteristics: (10 μm-60 μm): 9.9 percent; (60 μm-110 μm): 38.1 percent; (110 μm-160 μm): 41.2 percent; (160 μm-210 μm): 10.8 percent.

Comparative example 4

11 parts of corn starch are weighed into 100 parts of deionized water and dissolved thoroughly at 40 ℃. Then 0.35 part of epoxy chloropropane is added, and the mixture is mixed and reacted for 2 hours. 6 parts of AMPS is weighed and added into the starch solution, and the mixture is fully dissolved and mixed. 0.22 part of ammonium persulfate is added at 80 ℃ and reacted for 6 hours. 6 parts of dimethylaminetetradecylsulfanylammonium salt are added and mixed thoroughly. Weighing 62 parts of KCl to prepare 130 parts of inorganic salt solution, dripping the inorganic salt solution and 2 parts of epichlorohydrin into the starch solution at the same time at 55 ℃, and dripping the solution at a constant speed for 5 hours. And continuously reacting for 2 hours after the dropwise adding is finished to obtain the uniformly distributed polydisperse starch microspheres. The particle size concentration distribution interval of the starch microspheres is 5-205 mu m (92.5% of particle size is in the interval), and the particle size distribution in the particle size concentration distribution interval has the following characteristics: (5 μm-55 μm): 35.2 percent; (55 μm-105 μm): 21.6 percent; (105 μm-155 μm): 20.0 percent; (155 μm-205 μm): 23.2 percent.

Evaluation of application of the anionic starch microspheres as temporary plugging agents, namely sand bed plugging experiments, and evaluation is carried out by selecting samples in examples and comparative examples. An experimental instrument: a drilling fluid sand bed filtration loss instrument, a stirrer and an oven. Experimental materials: log 860 well slurry (density 1.19 g/cm)³) Examples, comparative examples and 20-40 mesh sand samples.

The experimental steps are as follows:

1. slurry preparation: formulated slurry +3% of the example sample or the comparative example sample.

2. Manufacturing a sand bed: adding 20-40 mesh sand into the cylinder by 350cm³Shaking up;

3. adding prepared experimental slurry (400-500 mL), fixing on an instrument frame and sealing an upper channel and a lower channel;

4. and opening an air source, adjusting the pressure to 0.69mPa, simultaneously opening an upper switch and a lower switch, and measuring the condition that the drilling fluid invades the sand bed in the half-hour process.

The experimental results are as follows:

the filtrate loss FL is 30min after the formula is added₁And the drilling fluid is basically stable after invading the sand bed to the depth D. After a stable mud cake is formed, the pressure is released, the drilling fluid is poured out, clear water is added to the position of 400mL, and the filtration loss FL after 30min of pressurization (0.69 mPa) measurement is carried out₂The results are shown in Table 1.

TABLE 1 results of the experiment

Sample (I)	Practice of Example 1	Practice of Example 2	Practice of Example 3	Practice of Example 4	Practice of Example 5	Practice of Example 6	Practice of Example 7	Practice of Example 8	Comparative example 1	Comparison of Example 2	Comparative example 3	Comparison of Example 4
													Fluid loss FL₁/ml	0	0	0	0	0	0	0	0	2	0	3	0
Depth D- cm³	130	175	170	210	200	165	210	200	350 (all) Immersion part)	340	350 (all) Immersion part)	300
													Fluid loss FL₂/ml	0	0	0	0	0	0	0	0	80	24	55	20

From the above results, it can be seen that the clear water shows good plugging effect without filtration loss at 0.69mPa pressure for 30min when the samples of examples 1-8 are used, while the clear water shows poor plugging effect with filtration loss of 80ml at 0.69mPa pressure for 30min when the samples of comparative examples 1-4 are used.

Claims

1. The anionic starch microspheres comprise the following raw materials in parts by weight: 100 parts of deionized water, 1-20 parts of starch, 10-50 parts of triethanolamine, 0.105-14.6 parts of epoxy chloropropane, 0.1-20 parts of anionic monomer, 0.001-0.2 part of initiator, 0.05-10 parts of zwitterionic surfactant and 0.5-200 parts of inorganic salt solution, wherein the inorganic salt solute accounts for 0.025-50 parts; the preparation method of the anionic starch microspheres comprises the following steps:

(1) weighing starch, adding the starch into water, adding triethanolamine, fully and uniformly mixing at 20-80 ℃, and adding epoxy chloropropane for reaction;

(2) adding an anionic monomer into the solution obtained in the step (1), fully dissolving and uniformly mixing, adding an initiator, and reacting for 3-6 hours at the temperature of 60-80 ℃;

(4) and (3) slowly adding an inorganic salt solution and epoxy chloropropane into the feed liquid obtained in the step (3) at a constant speed at the temperature of 30-60 ℃, and continuing to react after the inorganic salt solution and the epoxy chloropropane are added to obtain the starch microspheres.

2. The anionic starch microspheres according to claim 1, wherein the raw materials of the anionic starch microspheres comprise the following components in parts by weight: 100 parts of deionized water, 5-15 parts of starch, 20-40 parts of triethanolamine, 1.04-7.8 parts of epoxy chloropropane, 5-15 parts of anionic monomer, 0.02-0.105 part of initiator, 1-6 parts of zwitterionic surfactant and 50-150 parts of inorganic salt solution, wherein the inorganic salt solute accounts for 0.5-30 parts.

3. The anionic starch microspheres according to claim 1, wherein the controllable particle size of the starch microspheres is in the range of 0.1-500 μm.

4. The anionic starch microspheres of claim 1, wherein the starch microspheres have a uniform polydispersity of particle size distribution within a concentrated distribution interval, said concentrated distribution interval characterized by a particle size distribution of: evenly dividing the particle size concentrated distribution interval into n intervals, wherein the ratio of the microspheres in each interval is as follows:

wherein n is an integer greater than 1.

5. The anionic starch microspheres according to claim 1, wherein the starch is one or more of mung bean starch, tapioca starch, sweet potato starch, wheat starch, water chestnut starch, lotus root starch and corn starch.

6. The anionic starch microspheres of claim 1, wherein the starch is corn starch and/or potato starch.

7. The anionic starch microsphere of claim 1, wherein the anionic monomer is one or more of acrylic acid, 2-methyl-2-acrylamidopropanesulfonic acid, fumaric acid, sodium allylsulfonate and sodium 2-acryloyloxy isopentene sulfonate.

8. The anionic starch microsphere of claim 1, wherein the initiator is any one of potassium persulfate, sodium persulfate and ammonium persulfate.

9. The anionic starch microspheres of claim 1, wherein said zwitterionic surfactant has the following structure:

wherein: n is an integer between 2 and 6, R is a carbon chain with the carbon number of 1 to 18, and the carbon chain is a saturated carbon chain and is a straight chain or a branched chain.

10. The anionic starch microspheres of claim 1, wherein said zwitterionic surfactant has the following structure:

wherein: n is 3 or 4; r is a carbon chain with 12-18 carbon atoms, and the carbon chain is a saturated carbon chain and is a straight chain or a branched chain.

11. The anionic starch microspheres of claim 9, wherein the zwitterionic surfactant comprises a substituted hydroxyl, amino or carboxyl group on the carbon chain except for the terminal carbon, and the same carbon is monosubstituted.

12. The anionic starch microspheres according to claim 1, wherein the zwitterionic surfactant is one or more of dimethyldodecylsulfopropyl ammonium salt, dimethylhexadecylsulfoethyl ammonium salt, dimethyloctadecylsulfonylammonium salt, dimethyl (3-hydroxydodecyl) sulfopropyl ammonium salt and dimethyl (6-aminotetradecyl) sulfoethyl ammonium salt.

13. The anionic starch microspheres of claim 1, wherein the inorganic salt is a soluble inorganic salt.

14. The anionic starch microspheres of claim 1, wherein the inorganic salt is one or more of sodium salt, potassium salt, ammonium salt, calcium salt, magnesium salt, and when the inorganic salt is sodium salt, 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; when the inorganic salt is potassium salt, the inorganic salt is one or more of potassium chloride, potassium bromide, potassium sulfate, potassium sulfite, potassium carbonate, potassium bicarbonate, potassium nitrate, potassium phosphate, potassium hydrogen phosphate and potassium silicate; when the inorganic salt is ammonium salt, the inorganic salt is one or more of ammonium chloride, ammonium bromide and ammonium nitrate; when the inorganic salt is a calcium salt, calcium chloride or calcium bromide; when the inorganic salt is a magnesium salt, the inorganic salt is one or more of magnesium chloride, magnesium bromide, magnesium sulfate and magnesium nitrate.

15. A method of preparing anionic starch microspheres as claimed in any one of claims 1 to 14, said method comprising the steps of:

16. The preparation method according to claim 15, wherein the starch in the step (1) is one or more of mung bean starch, tapioca starch, sweet potato starch, wheat starch, water chestnut starch, lotus root starch and corn starch.

17. The method according to claim 15 or 16, wherein the starch in the step (1) is corn starch and/or potato starch.

18. The method according to claim 15, wherein the temperature in the step (1) is 30 to 60 ℃; the reaction time is 0.5-4 h.

19. The method according to claim 15 or 18, wherein the temperature in the step (1) is 30 to 60 ℃; the reaction time is 1-3 h.

20. The method according to claim 15, wherein the anionic monomer in step (2) is one or more selected from acrylic acid, 2-methyl-2-acrylamidopropanesulfonic acid, fumaric acid, sodium allylsulfonate and sodium 2-acryloyloxy isopentenylsulfonate.

21. The production method according to claim 15, wherein the initiator in the step (2) is any one of potassium persulfate, sodium persulfate and ammonium persulfate.

22. The method according to claim 15, wherein the zwitterionic surfactant in step (3) has the following structure:

23. The method according to claim 15, wherein the step (a), (b), (c), (d), (e) and (d)3) The zwitterionic surfactant described in (1) has the following structure:

24. The method according to claim 22 or 23, wherein the zwitterionic surfactant has a hydroxyl, amino or carboxyl group substituted on the carbon chain except for the terminal group, and the same carbon is monosubstituted.

25. The method according to any one of claims 15, 22 and 23, wherein the zwitterionic surfactant is one or more of dimethyldodecylsulfopropyl ammonium salt, dimethylhexadecylsulfoethyl ammonium salt, dimethyloctadecylsulfonylammonium salt, dimethyl (3-hydroxydodecyl) sulfopropyl ammonium salt and dimethyl (6-aminotetradecyl) sulfoethyl ammonium salt.

26. The method according to claim 15, wherein the inorganic salt in the step (4) is a soluble inorganic salt.

27. The method according to claim 15 or 26, wherein the inorganic salt in step (4) is one or more of sodium salt, potassium salt, ammonium salt, calcium salt and magnesium salt, and when the inorganic salt is sodium salt, one or more of sodium chloride, sodium bromide, sodium sulfate, sodium sulfite, sodium carbonate, sodium bicarbonate, sodium nitrate, sodium phosphate, sodium hydrogen phosphate and sodium silicate; when the inorganic salt is potassium salt, the inorganic salt is one or more of potassium chloride, potassium bromide, potassium sulfate, potassium sulfite, potassium carbonate, potassium bicarbonate, potassium nitrate, potassium phosphate, potassium hydrogen phosphate and potassium silicate; when the inorganic salt is ammonium salt, the inorganic salt is one or more of ammonium chloride, ammonium bromide and ammonium nitrate; when the inorganic salt is a calcium salt, calcium chloride or calcium bromide; when the inorganic salt is a magnesium salt, the inorganic salt is one or more of magnesium chloride, magnesium bromide, magnesium sulfate and magnesium nitrate.

28. The preparation method of claim 15, wherein the deionized water, the starch, the triethanolamine, the epichlorohydrin, the anionic monomer, the initiator, the zwitterionic surfactant and the inorganic salt solution are respectively used in the following amounts by weight: 100 parts of deionized water, 1-20 parts of starch, 10-50 parts of triethanolamine, 0.105-14.6 parts of epoxy chloropropane, 0.1-20 parts of anionic monomer, 0.001-0.2 part of initiator, 0.05-10 parts of zwitterionic surfactant and 0.5-200 parts of inorganic salt solution, wherein the inorganic salt solute accounts for 0.025-50 parts.

29. The preparation method according to claim 15 or 28, wherein the deionized water, the starch, the triethanolamine, the epichlorohydrin, the anionic monomer, the initiator, the zwitterionic surfactant and the inorganic salt solution are respectively used in the following amounts by weight: 100 parts of deionized water, 5-15 parts of starch, 20-40 parts of triethanolamine, 1.04-7.8 parts of epoxy chloropropane, 5-15 parts of anionic monomer, 0.02-0.105 part of initiator, 1-6 parts of zwitterionic surfactant and 50-150 parts of inorganic salt solution, wherein the inorganic salt solute accounts for 0.5-30 parts.

30. The process according to claim 15, wherein the amount of epichlorohydrin in the step (1) is 0.005 to 0.6 parts.

31. The production process according to claim 15 or 30, wherein the amount of the epichlorohydrin in the step (1) is 0.04 to 3 parts.

32. The process according to claim 15, wherein the amount of epichlorohydrin in the step (4) is 0.1 to 14 parts.

33. The production method according to claim 15 or 32, wherein the amount of the epichlorohydrin in the step (4) is 1 to 7.5 parts.

34. Use of anionic starch microspheres according to any one of claims 1 to 14 in a reservoir protection temporary blocking agent.