CN111057159B - Anti-collapse modified starch for drilling fluid and preparation method thereof - Google Patents
Anti-collapse modified starch for drilling fluid and preparation method thereof Download PDFInfo
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- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B31/00—Preparation of derivatives of starch
- C08B31/08—Ethers
- C08B31/12—Ethers having alkyl or cycloalkyl radicals substituted by heteroatoms, e.g. hydroxyalkyl or carboxyalkyl starch
- C08B31/125—Ethers having alkyl or cycloalkyl radicals substituted by heteroatoms, e.g. hydroxyalkyl or carboxyalkyl starch having a substituent containing at least one nitrogen atom, e.g. cationic starch
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- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/02—Well-drilling compositions
- C09K8/03—Specific additives for general use in well-drilling compositions
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- C09K2208/00—Aspects relating to compositions of drilling or well treatment fluids
- C09K2208/12—Swell inhibition, i.e. using additives to drilling or well treatment fluids for inhibiting clay or shale swelling or disintegrating
Abstract
The invention relates to an anti-collapse modified starch for drilling fluid and a preparation method thereof, belonging to the field of additives for drilling fluid in petroleum drilling engineering; the anti-collapse modified starch for the drilling fluid mainly comprises the following raw materials: starch, low-carbon alcohol, a starch acylating agent, a cross-linking agent, a quaternary ammonium salt cationic agent and a catalyst; the anti-collapse modified starch which can resist 150 ℃ and has a remarkable anti-collapse function is prepared by modifying the original starch by using a method of appropriate cross-linking and proportion-controlled anion-cation ionization. The product has rich raw material sources, good water loss reducing and inhibiting effects, and no pollution to the environment, and is the anti-collapse modified starch with stable performance.
Description
Technical Field
The invention relates to the field of additives for drilling fluid in petroleum drilling engineering, and further relates to an anti-collapse modified starch for drilling fluid and a preparation method thereof.
Background
With the progress of the environmental protection concept and the implementation of a new environmental protection method, higher requirements are provided for the drilling fluid, how to reduce the environmental pollution to the maximum extent, meet the requirements of drilling engineering on safety, high quality, rapidness and high efficiency, protect the environment, ensure that the drilling fluid treating agent is nontoxic and harmless to the environment, and benefit offspring and descendants. However, in order to solve the problems of collapse, diameter shrinkage, serious slurry making and the like in drilling of deep and complex strata, asphalt anti-collapse agents, salt inhibitors and the like are often required to be added, wherein some toxic monomers are used as organic treating agents synthesized by raw materials, and finished products are difficult to degrade and may contain completely unreacted toxic monomers, so that the biotoxicity index of the drilling fluid is difficult to meet the requirement of environmental protection. At present, most of developed oil and gas fields are environment-sensitive areas, are seriously lack of water, have rare vegetation, increasingly worsen desertification and have very severe situation of environmental protection problem.
Through a large number of scientific research and customs research at home and abroad, the environmental-friendly drilling fluid treating agent achieves certain performance, mainly focuses on the environmental-friendly filtrate reducer, and has less research on the environmental-friendly anti-sloughing agent. The starch is natural and rich in source and low in price, is a renewable resource, is commonly used as a fluid loss additive in petroleum drilling engineering, mainly has a good fluid loss reducing effect in saline water, and also has the advantages of reservoir protection, biodegradability and no biotoxicity. The modified starch researched by the invention is less researched at home and abroad as an environment-friendly anti-sloughing agent, and the environment-friendly anti-sloughing modified starch can replace a drilling fluid anti-sloughing treating agent with high toxicity and harm to the environment. Chemical modification of starch as an anti-sloughing agent for drilling fluid is rarely reported, most of the starch is used as a fluid loss agent with anti-sloughing performance, and the methods mainly comprise three methods, namely gelatinization, cationization and graft copolymerization. The gelatinization method has the main advantages of simple processing technology and low cost, and has the defect of poor thermal stability, and can only be used at the well temperature of 80-100 ℃; the single agent of the product synthesized by the cationization method can reach 100-120 ℃, and the product is characterized by small molecular weight and a large amount of cations in molecules, the Cationic Starch (CS) product synthesized by the method has a large amount of positive charges, is easy to foam in the dissolving process, has low bond breaking temperature and poor temperature resistance, and if the using temperature exceeds 120 ℃, a large amount of oxygen reducing agent and bactericide are required to be added into the drilling fluid to improve the high temperature resistance and salt resistance of the product; the use temperature of the product synthesized by the graft copolymerization method is 130-180 ℃, the product has the advantages of improving the thermal stability of starch, and the product after graft copolymerization has larger molecular weight, and has the disadvantages of complex production process, possible damage to the main chain of the starch, great degradation difficulty of the synthesized product and higher cost.
Disclosure of Invention
In order to solve the problems that the single modified starch synthesized by the cationization method in the prior art has the use temperature of 100-120 ℃ and the anti-collapse performance is not obvious, the invention provides anti-collapse modified starch for drilling fluid, and particularly relates to the anti-collapse modified starch for the drilling fluid and a preparation method thereof. According to the invention, the anti-collapse modified starch with 150 ℃ resistance and obvious anti-collapse function is prepared by modifying the original starch by using a method of appropriate crosslinking and proportion-controlled anion-cation ionization.
One of the purposes of the invention is to provide an anti-collapse modified Starch for drilling fluid, which has a general structural formula of Starch-O-C2NR or (C)6H10O5)n-O-C2NR, wherein Starch is
n is 300-600, R is a metal element with positive charge; preferably, R is a monovalent metal element; more preferably, R is selected from at least one of K, Na, Ca or Mg;
the molecular weight of the modified starch can be between 5 and 10 ten thousand.
The substitution degrees of the anion and the cation are within a certain range, the substitution degree of the anion is within a period of 0.34-0.38, and the substitution degree of the cation is within a period of 0.39-0.41. The substitution degree of anions adopts a complexometric titration method; the method can be used for testing by a common testing method in the field, and can be tested by a method for testing the substitution degree in national standard GB 1904-2005 food additive sodium carboxymethyl cellulose of the people's republic of China. The cation substitution degree measuring method is calculated according to the measurement of ammonia content, and the measuring method can refer to the national standard GB 608-88 of the general method for measuring nitrogen by chemical reagents, a semimicro method and the method GB 12091-89 for measuring the nitrogen content of starch and derivatives.
The invention also aims to provide a preparation method of the anti-collapse modified starch for the drilling fluid, which is mainly prepared from the following raw materials: starch, low-carbon alcohol, a starch acylating agent, a cross-linking agent, a quaternary ammonium salt cationic agent and a catalyst. The method specifically comprises the following steps:
(1) dissolving starch in low-carbon alcohol to prepare starch suspension, dissolving a quaternary ammonium salt cationic agent and an alkaline catalyst in the starch suspension, and uniformly mixing to obtain starch slurry;
(2) adding a cross-linking agent and a starch acylating agent into the starch slurry, adding an alkaline catalyst for more than two times, heating, and reacting under stirring;
(3) and after the reaction is finished, adjusting the pH, washing with low-carbon alcohol, performing suction filtration, and drying to obtain the catalyst.
The ratio of the weight of the starch in the step (1) to the total weight of the alkaline catalyst used in the preparation method (the sum of the weight of the alkaline catalyst used in the step (1) and the weight of the alkaline catalyst used in the step (2)) can be (2-4): 1.
The weight ratio of the starch to the quaternary ammonium salt cationic agent can be (1-4): 1, and preferably (2-3): 1.
In the step (1), the weight ratio of starch in the starch slurry to the alkaline catalyst used in the step (1) is (10-16): 1.
in the step (2), the weight ratio of the starch in the starch slurry to the cross-linking agent is (1400-1700): 1.
In the step (2), the weight ratio of starch in the starch slurry to the starch acylating agent is (4-5): 1.
The lower alcohol can be at least one selected from methanol, ethanol and propanol.
The starch may be selected from at least one of corn starch, tapioca starch or potato starch.
In the step (1) and the step (2), the alkaline catalyst can be at least one of sodium hydroxide and potassium hydroxide.
Quaternary ammonium cationic agents are derivatives of organic amines containing primarily nitrogen, in which the nitrogen atom has four alkyl groups attached, i.e. ammonium ions
All four hydrogen atoms of (a) are substituted by alkyl groups. The quaternary ammonium salt cationic agent can be at least one selected from alkyl dimethyl benzyl quaternary ammonium salt, alkyl trimethyl quaternary ammonium salt, dialkyl dimethyl quaternary ammonium salt and the like; specifically, the surfactant can be at least one selected from 2, 3-epoxypropyltrimethylammonium chloride, benzyltriethylammonium chloride and dodecyltrimethylammonium chloride.
The starch acylating agent can be various reagents capable of acylating or etherifying the hydroxyl group of the starch, preferably is halogenated carboxylic acid with 2-4 carbon atoms, and specifically can be one or more selected from chloroacetic acid, bromoacetic acid, dichloroacetic acid, dibromoacetic acid, trichloroacetic acid and tribromoacetic acid; chloroacetic acid is preferred.
The cross-linking agent can be at least one selected from epoxy chloropropane, propylene oxide, methyl epichlorohydrin, epoxy polydimethylsiloxane, phosphorus oxychloride, sodium trimetaphosphate, adipic acid, sodium tripolyphosphate, hexametaphosphate, formaldehyde and divalent or trivalent mixed anhydride; preferably epichlorohydrin, propylene oxide, methyl epichlorohydrin, phosphorus oxychloride, sodium trimetaphosphate, sodium tripolyphosphate, formaldehyde and divalent or trivalent mixed anhydride; more preferably epichlorohydrin.
Wherein the content of the first and second substances,
in the step (1), the starch can be dissolved in low carbon alcohol to prepare starch suspension with the weight concentration of 15-25%. The invention prepares the starch slurry with uniform dispersion and low carbon alcohol, ensures that the water enters as little as possible, and prevents the starch from swelling and hydrating or generating gelatinization reaction at certain temperature.
In the step (1), if the powder or the flake catalyst is directly added, local concentration is easily overhigh and belongs to exothermic reaction, product synthesis is influenced, a small amount of water can be used for dissolving the quaternary ammonium salt cationic agent and the alkaline catalyst, the temperature is kept to be room temperature as far as possible, and then the mixture is added into the starch suspension together, so that uniformity and reaction quality of alkaline addition are guaranteed, the water is used for completely dissolving the quaternary ammonium salt cationic agent and the alkaline catalyst, the water amount required for dissolving is small, and starch slurry is not influenced.
In the step (2), the temperature can be raised to 40-70 ℃.
In the step (2), the starch acylating agent and the alkaline catalyst can be respectively prepared into solutions and then used, specifically, the starch acylating agent can be dissolved in a low-carbon alcohol to prepare a starch acylating agent solution with the weight concentration of 3-10%, and the alkaline catalyst can be dissolved in the low-carbon alcohol to prepare a catalyst solution with the weight concentration of 4-11%;
in the step (2), a cross-linking agent, a starch acylating agent and a part of catalyst are added into the starch slurry, the temperature is raised, the reaction is carried out under stirring, and then the rest of the catalyst is added for reaction (specifically, the reaction is carried out for 3-6 h under the condition that the stirring speed is controlled to be 500-1000 rpm, and then the rest of the catalyst solution is added for reaction for 2-4 h); wherein the weight of the partial catalyst is 1/8-3/8 of the total amount of the catalyst used in the step (2). Wherein the residual catalyst solution is 1/8-3/8 residual; the catalyst is added twice, so that a certain pH value is kept in the whole reaction, the catalyst is added twice, the reaction is more sufficient, and the efficiency is higher.
In the step (3), the pH can be adjusted to 7.5-9 by using sulfuric acid after the reaction is finished. Meanwhile, the sulfuric acid can effectively purify the primary product and remove impurities.
The main function of the anti-collapse starch is to inhibit the hydration expansion and dispersion of the shale. The method can be divided into two main categories according to different action modes: the first category is to prevent or delay the contact of water-sensitive mineral particles with water in the drilling fluid, i.e. how to avoid or slow the migration of water to the formation to the greatest extent, which is mainly realized by plugging the well wall or reducing the filtration loss. Secondly, how to minimize or delay the hydration tendency of the water sensitive mineral particles after the drilling fluid filtrate invades the formation. In contrast, the latter technical measures are more effective for solving the problem of borehole wall collapse. The coating agent is an important inhibition type anti-collapse agent, and mainly stabilizes the shale through adsorption action and hinders the hydration tendency of water-sensitive mineral particles. The stronger the coating effect, the better the ability to inhibit the dispersion of the water-sensitive mineral particles, and the stronger the anti-collapse effect thereof. The strength of the coating effect is mainly reflected in the following two aspects: in one aspect, the type of adsorbed groups on the molecular chain. Hydroxyl, amide, phenolic hydroxyl, carbonyl, imino, ether bond, nitrile group and the like, all belong to nonionic strong adsorption groups, have certain polarity and are easy to adsorb on the surface of the water-sensitive mineral particles; the quaternary ammonium group belongs to an ionic group, and the adsorption capacity is stronger. On the other hand, the number of adsorption groups on the molecular chain. The larger the quantity, the more favorable the occupation of the adsorption sites on the surface of the water-sensitive mineral particles, and the stronger the coating capacity, the more favorable the reduction or delay of the hydration tendency of the water-sensitive mineral particles. According to the collapse-proof modified starch researched and designed, hydroxyl groups are densely distributed on a molecular chain, and special adsorption groups are introduced into the molecular chain through chemical modification, namely the coating effect of a molecular polymer on dispersible water-sensitive mineral particles is further improved through introducing strong adsorption groups, so that the aims of inhibiting hydration of water-sensitive minerals and maintaining stability of a well wall are fulfilled. The specific action mechanism is as follows:
al in water-sensitive mineral (such as montmorillonite, chlorite, etc.) aluminum octahedron under lattice substitution3+Is easy to be coated with Mg2+、Fe2+Or Zn2+Substituted, Si in silicon-oxygen tetrahedron4+Easily coated with Al3+The isoelectric point is maintained at about 5 to 8 by substitution. When the pH value of the system is larger than the isoelectric point, the surfaces and the end faces of the water-sensitive mineral particles are negatively charged. Ammonium positive ions in molecular chains of the anti-collapse modified starch obtained through cationization are adsorbed on the surfaces of the negatively charged water-sensitive mineral particles through electrostatic interaction, and adjacent water-sensitive mineral sheet layers are bound together, so that the Zeta potential of the water-sensitive mineral particles is reduced; meanwhile, ether bonds and hydroxyl groups in the modified starch molecular chain are easy to form hydrogen bonds with oxygen on the surface of the water-sensitive mineral, and the adsorption position of water molecules on the surface of the water-sensitive mineral is occupied, so that the adsorption of the water molecules on the surface of the water-sensitive mineral is prevented, and the effect of inhibiting the hydration of the surface of the water-sensitive mineral is achieved; in addition, the adjacent hydroxyl groups on the ring structure of the modified starch can be connected with Al on the end face of the water-sensitive mineral particles3+Form coordination bond, namely modified starch forms coordination bond adsorption on the end face of the water-sensitive mineral, thereby further strengthening the coating effect of the molecular chain of the modified starch on the water-sensitive mineral particles. The coating film forming effect of the modified starch molecules on the water-sensitive minerals effectively prevents water molecules from entering the water-sensitive mineral layers, inhibits the osmotic hydration of the water-sensitive minerals, prevents the hydration expansion of the water-sensitive minerals, reduces the hydration collapse pressure, and finally achieves the purpose of preventing the formation collapse. The schematic diagram shows the action mechanism diagram of the anti-collapse modified starch shown in figure 7.
The prior art mostly adopts simple anionic etherification modification or simple cationized starch, but the technical scheme of the invention also adds cationic substitution in the process of twice alkali addition etherification modification, controls the cationic substitution, and ensures that the modified starch not only has the characteristics of etherified starch, but also has the function of strong cationic inhibition. Aiming at the defects of the prior art that the using temperature of a modified starch single agent synthesized by a cationization method is 100-120 ℃, the anti-collapse performance is not obvious and the like, the modified starch anti-collapse inhibitor which can resist 150 ℃ and has a remarkable anti-collapse function for drilling fluid is prepared by modifying raw starch by using a method of appropriate crosslinking and proportion-controlled anion-cation ionization. Compared with the prior art, the product produced by the preparation method has high yield, high purity and more stable performance. The modified starch product has rich raw material sources, has good water loss reduction and inhibition effects after the product formed by the reaction of the modified starch product and chloroacetic acid is subjected to sulfuric acid neutralization reaction and low-carbon alcohol washing under the action of twice catalysis of the catalyst, has good temperature resistance, does not pollute the environment, and is anti-collapse modified starch with stable performance.
Effects of the invention
(1) The alkaline catalyst is added in batches in the reaction process, and the dosage is also finely controlled, so that the reaction efficiency and the stability of the synthesized product are improved.
(2) In the reaction process, the quaternary ammonium salt cationic agent is added firstly during the preparation of the emulsion, so that the occupied space of a proper amount of the cationic agent is ensured, the proper cationization in the heating reaction process is ensured, and the etherification substitution degree of anions is controlled.
(3) The product prepared by the method has simple process, reduces the addition of the preservative, and has more environment-friendly production process.
(4) The anti-collapse modified starch has the following adsorption capacity effects: after high-temperature aging (150 ℃) and high-temperature high-pressure (150 ℃) filtration loss, the anti-collapse modified starch molecules can still have adsorption effect with the montmorillonite particles.
(5) According to GB/T16783.1-2014, oil and gas industry drilling fluid field test part 1: the method in the Water-based drilling fluid measures the apparent viscosity, plastic viscosity, dynamic shear force and medium pressure water loss of 4 percent bentonite slurry added with 2 percent anti-collapse modified starch under the condition of room temperature, then seals the slurry in an aging tank, rolls for 16 hours at 150 ℃, and measures the apparent viscosity, plastic viscosity, dynamic shear force and medium pressure water loss of the aged drilling fluid after cooling to the room temperature. The result shows that the environment-friendly anti-collapse modified starch has good rheological property and lower filtration loss in soil slurry, and the product can be used at the high temperature of 150 ℃.
(6) Preparing an environment-friendly anti-collapse modified starch aqueous solution, adding 2% anti-collapse starch into a 3% KCl solution, performing a shale expansion experiment, pressing an artificial core at 6000psi, soaking for 24 hours in the environment-friendly anti-collapse modified starch aqueous solution, and measuring the expansion rate to be 60.11%.
(7) According to the detection of biological toxicity of GB/T18420.2-2009 'method for detecting biological toxicity of pollutants for offshore oil exploration and development', the half-lethal concentration LC50 value of the environment-friendly anti-collapse modified starch reaches 174000mg/L, which is far greater than the allowable value 30000mg/L of biological toxicity of the water-based drilling fluid in the first-class sea area, and meets the requirement of biological toxicity.
(8) The technical scheme of the invention has the advantages of full reaction and stable product quality, and is suitable for large-scale production.
Application prospect of the invention
The single agent product prepared by the invention can be suitable for being used as an environment-friendly anti-collapse framework treating agent for fresh water and salt water type drilling fluid systems in boreholes with the bottom temperature of 100-150 ℃ in petroleum drilling engineering.
The development of the single anti-collapse modified starch agent expands the application of starch in drilling fluid, such as well temperature and anti-collapse effect inhibition, and comprises the following steps: formate drilling fluid, silicate drilling fluid, clay-phase-free calcium chloride drilling fluid, NaCL/PHPA drilling fluid, KCL/polyalcohol drilling fluid and polyamine high-performance drilling fluid, and better meets the market and technical requirements of using environment-friendly drilling fluid in deep wells, offshore wells and complex stratum drilling during petroleum exploration.
The research and the application of the environment-friendly anti-collapse modified starch are carried out, and the theme of picking up from the source and developing the green industry in the field of petroleum drilling engineering at present is met. Firstly, the starch is natural and rich in source and low in price, and is a renewable resource; secondly, the researched environment-friendly anti-sloughing modified starch can replace a drilling fluid anti-sloughing treating agent with high toxicity and harm to the environment; finally, the application of the environment-friendly drilling fluid system formed by the environment-friendly anti-collapse modified starch is environment-friendly, and can be used for drilling of medium petrochemicals in oceans, environment-sensitive areas and deep complex strata.
Drawings
FIG. 1-1 is an infrared spectrum of the anti-sloughing modified starch for drilling fluid prepared in example 3;
FIGS. 1-2 are thermogravimetric analysis spectra of the anti-sloughing modified starch for drilling fluid prepared in example 3;
FIG. 2-1 is an XPS energy spectrum of a solid phase of a montmorillonite-anti-sloughing modified starch drilling fluid system after high temperature and high pressure filtration (aging for 16h at 120 ℃); the abscissa is the scanning energy and the ordinate is the intensity;
FIG. 2-2 is an XPS energy spectrum of the solid phase of the montmorillonite-anti-sloughing modified starch drilling fluid system after high temperature and high pressure filtration (aging for 16h at 150 ℃);
FIG. 3-1 is a graph showing the dynamic adsorption profile of the anti-sloughing modified starch at 150 ℃;
FIG. 3-2 is a graph (100 ℃) showing the relationship between the high-temperature adsorption capacity and the rolling recovery rate of the anti-collapse modified starch;
FIG. 3-3 is a graph (120 ℃) showing the relationship between the high-temperature adsorption capacity and the rolling recovery rate of the anti-collapse modified starch;
FIG. 3-4 is a graph (150 ℃) showing the relationship between the high-temperature adsorption capacity and the rolling recovery rate of the anti-collapse modified starch; the abscissa represents the different addition amounts of modified starch;
FIG. 4 is a graph (150 ℃) showing the change of the high-temperature adsorption capacity and the rolling recovery rate of the anti-collapse modified starch with the high-temperature action time; the abscissa is time (hours);
FIG. 5-1 is an AFM photograph (normal temperature) of the collapse preventing modified starch;
FIG. 5-2 is an AFM photograph (150 ℃ C.. times.16 h) of an anti-sloughing modified starch;
FIG. 6-1 is a TEM photograph (normal temperature) of the collapse preventing modified starch in water (observation range 0.5 μm);
FIG. 6-2 is a TEM photograph (normal temperature) of the collapse preventing modified starch in water (observation range 200 nm);
FIG. 6-3 is an ESEM photograph (normal temperature) (5000 times magnification) of the anti-collapse modified starch in water;
FIGS. 6-4 are ESEM photographs (normal temperature) of the anti-collapse modified starch in water (magnification: 10000 times);
FIGS. 6-5 are TEM photographs (150 ℃ C.. times.16 h) of the collapse preventing modified starch in water (observation range 0.5 μm);
FIGS. 6-6 are TEM photographs (150 ℃ C.. times.16 h) of the collapse preventing modified starch in water (observation range 200 nm);
FIGS. 6-7 are ESEM photographs (150 ℃ C.. times.16 h) (5000 magnification) of collapse resistant modified starch in water;
FIGS. 6-8 are ESEM photographs (150 ℃ C.. times.16 h) (10000 times magnification) of collapse preventing modified starch in water;
FIG. 7 is a diagram of the mechanism of action of the anti-collapse modified starch.
Detailed Description
The present invention will be further described with reference to the following examples. However, the present invention is not limited to these examples.
Example 1
(1) Dissolving 100g of corn starch in pure ethanol to prepare a corn starch suspension with the weight concentration of 20%, dissolving 45g of quaternary ammonium salt cationic agent 2, 3-epoxypropyltrimethylammonium chloride and 8g of sodium hydroxide in the corn starch suspension, and uniformly mixing to obtain corn starch slurry;
(2) dissolving 25g of chloroacetic acid with the concentration of more than 97% in ethanol to prepare a chloroacetic acid solution with the weight concentration of 6.5%; dissolving 28g of sodium hydroxide in ethanol to prepare a catalyst solution with the weight concentration of 7%; pouring the corn starch slurry prepared in the step (1) into a three-neck flask, firstly dropwise adding 0.05g of epoxy chloropropane, then sequentially adding all chloroacetic acid solution prepared in the step and 1/4 weight of catalyst solution prepared in the step, heating to 65 ℃ in a constant-temperature water bath, reacting for 3h under the condition of controlling the stirring speed to be 800rpm, and then adding the rest of catalyst solution prepared in the step for reacting for 3 h.
(3) And after the reaction is finished, neutralizing the pH value to 7.5-9 with sulfuric acid, washing with low-carbon alcohol, performing suction filtration, and performing forced air drying at the temperature of about 50 ℃ to obtain the product, namely the collapse-preventing modified starch for the drilling fluid. The anionic substitution degree of the collapse-preventing modified starch for the drilling fluid is measured to be 0.38, and the cationic substitution degree is measured to be 0.40.
Example 2
(1) Dissolving 90g of corn starch in pure ethanol to prepare a corn starch suspension with the weight concentration of 18%, dissolving 35g of quaternary ammonium salt cationic agent 2, 3-epoxypropyltrimethylammonium chloride and 6g of alkaline catalyst sodium hydroxide in the corn starch suspension, and uniformly mixing to obtain corn starch slurry;
(2) dissolving 20g of chloroacetic acid with the weight concentration of more than 97% in ethanol to prepare a chloroacetic acid solution with the weight concentration of 5.0%; 36g of basic catalyst sodium hydroxide was dissolved in ethanol to prepare a 9% by weight catalyst solution. Pouring the prepared corn starch slurry in the step (1) into a three-neck flask, sequentially dropwise adding 0.06g of epoxy chloropropane, then adding all the chloroacetic acid solution prepared in the step and 1/8 weight of the catalyst solution prepared in the step, heating to 50 ℃ in a constant-temperature water bath, reacting for 4h under the condition that the stirring speed is controlled to be 700rpm, and then adding the rest catalyst solution for reacting for 4 h.
(3) And after the reaction is finished, neutralizing the pH value to 7.5-9 with sulfuric acid, washing with low-carbon alcohol, performing suction filtration, and performing forced air drying at the temperature of about 50 ℃ to obtain the product, namely the collapse-preventing modified starch for the drilling fluid. The anionic substitution degree of the collapse-preventing modified starch for the drilling fluid is measured to be 0.34, and the cationic substitution degree is measured to be 0.39.
Example 3
(1) Dissolving 110g of corn starch in pure ethanol to prepare a corn starch suspension with the weight concentration of 22%, dissolving 55g of quaternary ammonium salt cationic agent 2, 3-epoxypropyltrimethylammonium chloride and 9g of alkaline catalyst sodium hydroxide in the corn starch suspension, and uniformly mixing to obtain corn starch slurry;
(2) dissolving 26g of chloroacetic acid with the weight concentration of more than 97% in ethanol to prepare a chloroacetic acid solution with the weight concentration of 6%; dissolving 24g of sodium hydroxide in ethanol to prepare a catalyst solution with the weight concentration of 6%; pouring the corn starch slurry prepared in the step (1) into a three-neck bottle, dropwise adding 0.07g of epoxy chloropropane, sequentially adding all chloroacetic acid solution prepared in the step and 3/8 weight of catalyst solution prepared in the step, heating to 50 ℃ in a constant-temperature water bath, reacting for 5 hours at a stirring speed of 500rpm, and then adding the rest of catalyst solution prepared in the step for reacting for 3 hours.
(3) And after the reaction is finished, neutralizing the pH value to 7.5-9 with sulfuric acid, washing with low-carbon alcohol, performing suction filtration, and performing forced air drying at the temperature of about 50 ℃ to obtain the product, namely the collapse-preventing modified starch for the drilling fluid. The anionic substitution degree of the collapse-preventing modified starch for the drilling fluid is 0.37, and the cationic substitution degree is 0.41.
Spectrogram testing is carried out on the anti-collapse modified starch for the drilling fluid prepared in the example 3, and a figure 1-1 and a figure 1-2 are obtained. FIG. 1-1 is an infrared spectrum for verifying the species of molecular functional groups, and FIG. 1-2 is a thermogravimetric analysis spectrum for verifying the highest thermal decomposition temperature of the molecule itself.
As shown in the infrared spectrum of figure 1-1, the anti-collapse modified starch after chemical modification has many characteristic absorption peaks increased compared with the original starch, especially at 1650cm-1An amino characteristic absorption peak appears at the position, and-COO appears at the wave number of 1610cm-Characteristic absorption peak of ion, 1450cm-1、1420cm-1Characteristic absorption peaks of methyl and methylene after the hydroxyl is substituted; the environment-friendly anti-collapse modified starch developed by the project accords with the molecular structure design in the aspect of chemical molecular structure.
As can be seen from the thermogravimetric analysis chart of fig. 1-2, the prepared anti-collapse natural polymer modified starch has two degradation processes of thermal reduction in nitrogen, the first slight weight loss process occurs between 80 ℃ and 100 ℃, which is caused by the diffusion of free water in the modified starch; the second time of large weight loss occurs at 150-250 deg.c, because the modified starch itself is decomposed thermally in short time and the structure is destroyed.
Example 4 Effect of adsorption Capacity of collapse-preventing modified starch
In the experiment, an SAM800/series800SIMS XPS spectrometer of KRATOS company in UK is adopted to study the adsorption of the anti-collapse modified starch prepared in example 3 on the water-sensitive mineral particles, and the adsorption capacity of the anti-collapse modified starch is deeply analyzed.
The anti-collapse modified starch prepared in example 3 was added to a 4.0 wt% fresh water base slurry containing montmorillonite, aged in a hot roller oven at 120 ℃ and 150 ℃ for 16 hours, and then subjected to an experiment using a high temperature and high pressure filtration apparatus (model: 387, manufactured by fann corporation) to filter out all the liquid phase and retain all the solid phase, and finally subjected to energy spectrum analysis using SAM800/series800SIMS type X-ray photoelectron spectroscopy of KRATOS corporation, uk. As shown in fig. 2-1 and 2-2.
And (3) testing conditions are as follows: the radiation source is Mg-K α (h ν 1253.6eV), and the charge effect correction of the sample surface is calibrated with C1s (284.60eV) at an angle of incidence of 90 °. The energy range of full-spectrum scanning is 0-1100 eV, the scanning step length is 1.0eV, the pass energy is 8.0eV, and the scanning times are 2 times; the step length of narrow spectrum scanning is 50.0meV, the energy is 6.0eV, the scanning times are 3 times, the working voltage is 15kV, the power is 150W, and the analysis area is 0.3 multiplied by 0.3mm2(ii) a The vacuum degree of the vacuum chamber is 1X 10-9Torr, resolution was 1.2 eV.
As can be seen from FIGS. 2-1 and 2-2, the montmorillonite surface contains not only three elements of Si, O and Al, but also absorption peaks of N1s and C1s appear in the vicinity of 400.0eV, 285.0eV and 169.0eV, respectively, indicating that N and C appearing on the montmorillonite surface are derived from the anti-collapse modified starch molecule. Therefore, the anti-collapse modified starch molecules can still be adsorbed with the montmorillonite particles after high-temperature aging (150 ℃) and high-temperature high-pressure (150 ℃ and 3.5MPa) filtration.
Example 5 Effect of concentration of anti-collapse modified starch on adsorption and anti-collapse Properties
The adsorption capacity of the anti-collapse modified starch on the montmorillonite under the high-temperature action is researched, firstly, the adsorption equilibrium time is accurately grasped through a dynamic adsorption curve, and then, the adsorption capacity of the anti-collapse modified starch on the montmorillonite under the equilibrium adsorption condition is measured on the basis. The adsorption amount of the anti-collapse modified starch prepared in example 3 on montmorillonite under equilibrium adsorption conditions was measured at 150 ℃. The measurement results are shown in FIG. 3-1.
FIG. 3-1 is a dynamic adsorption curve of the collapse preventing modified starch at 150 ℃. As can be seen from the figure, the adsorption capacity of the anti-collapse modified starch on the montmorillonite is gradually increased along with the prolonging of the time, and finally, the adsorption balance can be achieved within the range of 60-80 min. In general, due to the characteristics of the adsorption groups of the anti-collapse modified starch, the anti-collapse starch has good adsorption performance at 150 ℃, high temperature and violent molecular motion, the adsorption balance can move towards the desorption direction, and the time required for reaching the adsorption balance is short.
Preparing 4.0 wt% of fresh water-based slurry, and adding 0.2 wt% of Na2CO3After the mixture is divided into a plurality of parts, the anti-collapse modified starch prepared in the example 3 with different masses is added respectively, and the mixture is maintained in a sealed container for 24 hours to obtain the montmorillonite-anti-collapse modified starch drilling fluid system. Aging the drilling fluid system at 100 ℃, 120 ℃ and 150 ℃ for 16h, and measuring the high-temperature adsorption capacity under the corresponding temperature condition. In addition, the rolling recovery rate of the rock debris after aging for 16h at 100 ℃, 120 ℃ and 150 ℃ under different concentration conditions is measured, and the measurement results are shown in figure 3-2, figure 3-3 and figure 3-4.
FIGS. 3-2, 3-3 and 3-4 show the high temperature adsorption capacity and corresponding rolling recovery rate of the collapse preventing modified starch at 100 deg.C, 120 deg.C and 150 deg.C, respectively, for drilling fluid systems to which different concentrations of the collapse preventing modified starch are added. 3-2, 3-3 and 3-4, the corresponding rolling recovery rate of the high temperature adsorption capacity of the anti-collapse modified starch is gradually increased along with the increase of the concentration of the anti-collapse modified starch under the 3 aging temperature conditions. The experimental result shows that when 1.0 wt% of the anti-collapse modified starch is added into the soil slurry containing 4.0 wt%, the rolling recovery rate of the shale can be respectively improved from 19.98% (100 ℃), 16.77% (120 ℃) and 14.32% (150 ℃) to 78.71% (100 ℃), 83.04% (120 ℃) and 78.83% (150 ℃), and the hydration of the shale is remarkably inhibited.
Example 6 Effect of temperature of anti-sloughing starch on adsorption and anti-sloughing Properties
Preparing 4.0 wt% of fresh water-based slurry, and adding 0.2 wt% of Na2CO3And adding 1.0 wt% of the anti-collapse modified starch prepared in the example 3, and maintaining the mixture in a sealed container for 24 hours to obtain a montmorillonite-anti-collapse modified starch drilling fluid system. Aging the drilling fluid system at 150 deg.CAfter 16h, measuring the high-temperature adsorption capacity to obtain the anti-collapse modified starch with the high-temperature adsorption capacity of 9.86mg g at the aging temperature of 150 DEG C-1。
In addition, 4.0 wt% of fresh water-based slurry was prepared, and 0.2 wt% of Na was added2CO3After the drilling fluid system is divided into two parts, 1.0 wt% of the anti-collapse modified starch prepared in the example 3 is added into one part, the other part is not added and is a blank sample, the two parts are maintained in a sealed container for 24 hours, the drilling fluid system is aged for 16 hours at the temperature of 150 ℃, the rolling recovery rate of rock debris aged for 16 hours at the temperature of 150 ℃ is measured, the rolling recovery rate of the drilling fluid system without the starch product is 38.20%, and the rolling recovery rate of the drilling fluid system added with the anti-collapse modified starch is 74.35%, which shows that the anti-collapse effect of the anti-collapse modified starch drilling fluid system is good.
Example 7 Effect of high temperature action time on adsorption and collapse prevention Properties
Preparing 4.0 wt% of fresh water-based slurry, and adding 0.2 wt% of Na2CO3And adding 1.0 wt% of the anti-collapse modified starch prepared in the example 3, and maintaining the mixture in a sealed container for 24 hours to obtain a montmorillonite-anti-collapse modified starch drilling fluid system. The drilling fluid system is placed in a hot roller furnace at 150 ℃, aged for 8 hours, 16 hours, 24 hours, 32 hours, 40 hours and 48 hours respectively, and then the high-temperature adsorption capacity under different high-temperature action time conditions is measured. In addition, the rolling recovery of the rock debris after aging for 8h, 16h, 24h, 32h, 40h and 48h at an aging temperature of 150 ℃ was measured, and the measurement results are shown in FIG. 4.
FIG. 4 shows the measured high-temperature adsorption capacity and corresponding rolling recovery rate of the anti-collapse modified starch after the montmorillonite-anti-collapse modified starch drilling fluid system is aged for 8 hours, 16 hours, 24 hours, 32 hours, 40 hours and 48 hours at the temperature of 150 ℃. As can be seen from FIG. 4, under the condition of the aging temperature of 150 ℃, the high-temperature adsorption capacity and the corresponding rolling recovery rate of the anti-collapse modified starch are slightly reduced along with the prolonging of the aging time, but the reduction trend is slow, so that the anti-collapse modified starch can play a role for a long time under the high-temperature condition, inhibit the hydration dispersion of the water-sensitive shale, and embody the long-acting property of the anti-collapse effect.
Example 8 Effect of collapse resistant modified starch in the microscopic State
An Atomic Force Microscope (AFM) photograph of the collapse preventing modified starch prepared in example 3 on a mica substrate was taken under normal temperature conditions using an Atomic Force Microscope (AFM) of type NanocopeIIa of Digital Instrument company, USA. Specifically, the research uses a nanoscope eiiia type AFM of the Digital Instrument company in the united states as a research tool, and utilizes the characteristic that the crystal structure of the surface of a mica substrate is similar to that of the surface of montmorillonite to approximately describe the adsorption morphology of the anti-collapse modified starch on the montmorillonite. The AFM working mode is tapping mode, the probe type is RTESP, the working frequency is 86kHz, and the force constant is 1.0-5.0 N.m-1. Adding collapse-preventing modified starch (1250 mg. L)-1) Dripping on newly dissociated mica substrate to spread uniformly as much as possible, naturally drying to form film, and observing microscopic adsorption morphology with AFM, wherein the experimental result is shown in figure 5-1.
Adding collapse-preventing modified starch (1250 mg. L)-1) After aging for 16h at 150 ℃, dripping on a newly dissociated mica substrate to uniformly spread the mica substrate as much as possible, observing the microscopic adsorption morphology by AFM after natural drying and film forming, wherein the experimental result is shown in figure 5-2.
FIG. 5-1 is an AFM photograph of an atomic force microscope on a mica substrate of the collapse resistant modified starch under normal temperature conditions. As can be seen in fig. 5-1, the mica surface is covered by a dense network structure. Apparently, this is due to the cross-linking of the polymers to form a continuous network structure. In the figure, the nodes forming the structure can be clearly seen, and the network structure is irregular and mainly takes a circle and an ellipse as main parts. The bright parts in the figure correspond to areas with higher surface height, and the bright areas do not appear as large-area gathered images, but are distributed on the mica substrate more uniformly, so that the weak interaction between molecular chains of the collapse-preventing modified starch can be shown, and the distribution in the solution is more uniform.
Most of the water-sensitive minerals are similar to mica in crystal structure and have the same surface crystal structure, so that a plurality of adsorption groups are distributed on the molecular chain of the anti-collapse modified starch, so that the water-sensitive minerals can be simultaneously adsorbed and coated by a plurality of anti-collapse modified starches to form a mixed network structure which is full of the whole system, and the anti-collapse modified starch is very favorable for inhibiting the hydration of the water-sensitive minerals and is beneficial to improving the anti-collapse performance of the drilling fluid.
The microscopic morphology of the anti-collapse modified starch after high temperature action: the high temperature will necessarily promote the thermal decomposition of the polymer molecules and their desorption at the surface of the water sensitive mineral particles. If the anti-collapse modified starch molecules have poor thermal stability or are excessively desorbed on the surfaces of the water-sensitive mineral particles, the hydration film on the surfaces of the water-sensitive mineral particles is inevitably thinned, the capability of blocking the hydration dispersion effect of the water-sensitive minerals is reduced, and thus the anti-collapse performance of the drilling fluid is negatively affected. Therefore, it is necessary to study the microscopic adsorption morphology of the anti-collapse modified starch on the surface of the water-sensitive mineral after high temperature, and provide more direct evidence for the thermal stability and strong adsorbability of the anti-collapse modified starch.
FIG. 5-2 is an AFM photograph of the collapse resistant modified starch on a mica substrate after aging at 150 ℃ for 16 h. As can be seen in fig. 5-2, the mica surface is covered by a dense network structure. However, compared with the anti-collapse modified starch on the mica substrate under the normal temperature condition, the nodes forming the structure are fuzzy, which is probably caused by the molecular chain shrinkage of the anti-collapse modified starch under the high temperature action. In general, the anti-collapse modified starch molecules after high-temperature aging form clear veins on the mica substrate, and the phenomena of agglomeration and chain scission do not occur, so that the anti-collapse modified starch can be judged to have better temperature resistance.
Example 9 microscopic Effect of collapse resistant modified starch in Water
The microscopic morphology of the anti-collapse modified starch in water under the normal temperature condition is as follows: preparation of collapse-preventing modified starch (800 mg. L) prepared in example 3-1) The aqueous solution of (2) was dropped on the copper mesh pure carbon film to spread it uniformly as much as possible, and after the film was naturally dried and formed, microscopic adsorption morphology was observed by TEM, and the experimental results are shown in FIG. 6-1 (observation range 0.5 μm) and FIG. 6-2 (observation range 200 nm).
Preparing collapse-proof modified starch (800 mg. L)-1) The aqueous solution is frozen by liquid nitrogen to prepare a sample, ESEM is directly utilized to observe the microscopic morphology of the anti-collapse modified starch in water under the normal temperature condition, and the experimental results are shown in figures 6-3(5000 times) and 6-4(10000 times)。
And 6-1, 6-2, 6-3 and 6-4 are TEM and ESEM photographs of the anti-collapse modified starch in water under the normal temperature condition. As can be seen from FIGS. 6-1 and 6-2, the anti-collapse modified starch molecules are cross-linked in the solution, and the molecular chains are communicated by molecular beams, forming a complete and extended molecular network structure in the three-dimensional space. In addition, as can be seen from fig. 6-3 and fig. 6-4, the molecular chains of the anti-collapse modified starch are in a filament shape in the aqueous solution, are cross-linked with each other, and have obvious interpenetrating networks in a three-dimensional space.
The microscopic morphology of the anti-collapse modified starch in water after high temperature action: preparing collapse-proof modified starch (800 mg. L)-1) After the aqueous solution is aged for 16h at 150 ℃, the aqueous solution is dripped to a copper net pure carbon film to be spread uniformly as much as possible, the microscopic adsorption morphology is observed by a TEM after the aqueous solution is naturally dried to form a film, and the experimental results are shown in a figure 6-5 (the observation range is 0.5 mu m) and a figure 6-6 (the observation range is 200 nm).
Preparing collapse-proof modified starch (800 mg. L)-1) After the aqueous solution is aged for 16h at 150 ℃, the sample is frozen by liquid nitrogen, the microscopic morphology of the anti-collapse modified starch in water under the normal temperature condition is directly observed by using ESEM, and the experimental results are shown in figures 6-7 (magnified 5000 times) and figures 6-8 (magnified 10000 times).
As can be seen from FIGS. 6-5, 6-6, 6-7 and 6-8, under the aging condition of 150 ℃, the molecules of the collapse-proof modified starch can still be cross-linked with each other in the solution, and the molecular beams are communicated with the space network state, which shows that the molecular chains of the collapse-proof modified starch still remain intact after the high temperature action of 150 ℃.
Example 10 Overall Performance Effect of collapse resistant modified starch
(1) Rolling recovery evaluation
The test method refers to a test method for testing the physical and chemical properties of the shale by using SYT 5613-2016 drilling fluid. The method comprises the following specific steps: comparative evaluation experiments were carried out indoors on the rolling recovery rates of 4% of the Chardonnay soil slurry (Chardonnay soil slurry reference standard SY/T5490 + 1993 sodium bentonite for drilling fluid tests) and the anti-collapse starch prepared in example 3. The rock debris is selected from sampling rock debris provided by Anhui drilling company in Anhui region with well depth of about 2100 m. Screening by 6-10 meshes, reserving the processed rock debris for later use, and screening the recovered rock debris subjected to hot rolling by a 40-mesh screen. The results of the experiments are shown in tables 1 and 2 below. In addition, the concentration of a chemical substance refers to its mass concentration unless otherwise specified herein.
TABLE 1 comparative evaluation of Rolling recovery-I
TABLE 2 comparative evaluation of Rolling recovery-2
The table shows that the rolling recovery rate after the anti-collapse starch is added reaches 92.5 percent, is improved by 38 percent compared with the rolling recovery rate of the base slurry, and has obvious water loss reducing effect after the anti-collapse starch sample is added. After rolling, the shape of the base pulp rock debris is obviously reduced, and the edges and corners become smooth; but the shape of the rock debris added with the anti-collapse starch is not obviously different from the shape before, and the shape and the size are kept intact.
(2) Comparison of the Properties with different products
The anti-collapse modified starch prepared in example 3 was subjected to performance test experiments with different products at 150 ℃. The products are dissolved in clean water, and after being heated and rolled at 150 ℃, the products are placed at room temperature, and relevant performances are measured, the method of the test experiment refers to standard numbers GB/T16783.1-2014 and SY/T5613-2016, and the test results are shown in Table 3.
TABLE 3 comparison of the Properties of the collapse resistant modified starch with the different products (150 ℃ C.)
Wherein the content of the first and second substances,
SMART is published under CN103665174A (application number 201310432320.X)Modified starch prepared by the method of example 1 in the national patent. The preparation method comprises mixing 100g of corn native starch (density of 1.52 g/cm)3Weight average molecular weight of 5-10 ten thousand) is dissolved in methanol to prepare corn starch suspension with the concentration of 20 wt%; preparing chloroacetic acid into a 5.5 wt% chloroacetic acid methanol solution; the catalyst potassium hydroxide was formulated as a 7 wt% aqueous solution. And pouring 175g of the corn starch suspension into a three-neck flask, sequentially adding 70g of the chloroacetic acid solution and 130g of the catalyst potassium hydroxide solution with the mass of 1/4, controlling the temperature to 65 ℃ in a constant-temperature water bath, reacting for 3 hours at the stirring speed of 750rpm, and then adding the rest 3/4 potassium hydroxide solution at the same temperature and the same stirring speed for reacting for 3 hours. And after the reaction is finished, neutralizing the pH value of the solution to 7.5-9 by using hydrochloric acid, washing by using methanol, performing suction filtration, and performing forced air drying at 50 ℃ to obtain a product SMART.
XC is xanthan gum, which is Shanghai Changli and is of type EVER BRIGHT.
The polyamine is a dendritic polyamine-based polymer provided in specifications [0015] to [0016] in Chinese patent publication No. CN104130758A (application No. 201310159974. X).
Flu-tro is a foreign modified starch product manufactured by Saudi America under the model Flu-tro.
As shown in Table 3 above, the anti-collapse starch has good performance and higher rolling recovery rate than other products, which indicates that the anti-collapse starch can still have good performance at a high temperature of 150 ℃ and has good anti-collapse performance.
(3) Environmental protection property of anti-collapse modified starch
The anti-collapse modified starch prepared in the example 3 is sent to a national oceanic administration Tianjin ocean environment monitoring central station for biotoxicity detection, and is numbered as JCU2016110914 according to the standards of 'method for detecting biotoxicity of pollutants for offshore oil exploration and development' (GB/T18420.2-2009) and 'biotoxicity classification of pollutants for offshore oil exploration and development' (GB18420.1-2009), and the test result is qualified, wherein the LC of the anti-collapse modified starch is50＝22.9×104mg/L (96h) which is larger than ocean first-level emission standard 30000mg/L and belongs to nontoxicAnd (3) a treating agent.
(4) Anti-collapse property of anti-collapse modified starch
And (3) performing a performance evaluation experiment on the anti-collapse starch prepared in the example 3 and different products, wherein the performance test method refers to the methods of standard numbers GB/T16783.1-2014 and SY/T5613-2016. Wherein the rock debris comes from a Tianx 100 well provided by Anhui drilling company, the well depth is about 2100 meters, the layer is positioned at four sections of Funing group Fumon, and the lithology is gray black, dark gray mudstone and soft mudstone with white mud crystal and argillaceous dolomite. The results are shown in Table 4 below.
TABLE 4 evaluation of the Properties of the collapse resistant modified starch with different products (150 ℃ C.)
Wherein the soil slurry is Xiazi street soil slurry.
As can be seen from Table 4, the rolling recovery rate after adding the anti-collapse starch of the present invention at 150 ℃ is obviously higher than that of the two basic slurry of clean water and soil slurry, and is also better than that of the inorganic inhibitor KCl and organic inhibitor polyamine which are commonly used in the current system.
Example 11
The performance of the anti-collapse modified starch for the drilling fluid prepared in the embodiments 1 to 3 is evaluated, the test method refers to the specifications of the drilling fluid materials in the standards GB/T16783.1-2014 and GBT5005-2001, and the test results are shown in the following table 5.
Table 5 evaluation results of performances of anti-collapse modified starch for drilling fluid prepared in examples 1 to 3
Remarking: the bentonite meets the requirements of SY/T5490-2016 soil for drilling fluid tests.
From the above, it can be seen that the samples synthesized in example 1, example 2 and example 3 have particularly good rheological properties and fluid loss reduction effect after 16h in 4% bentonite slurry at 150 ℃, wherein the fluid loss reduction effect is the best in example 1 after 16h in 4% bentonite slurry at 150 ℃, and the apparent viscosity is the lowest in example 2 in 4% bentonite slurry. The result shows that the environment-friendly anti-collapse modified starch has good rheological property and lower filtration loss in soil slurry and can be used under the high-temperature condition of 150 ℃.
Example 12
And taking 10g of dried bentonite, and pressurizing for 30min under 6000psi pressure to prepare the artificial rock core. The artificial core was immersed in distilled water, a 3% potassium chloride solution and a 3% potassium chloride + 2% solution of the collapse preventing modified starch prepared in example 1, respectively, and the swelling rate of the artificial core was measured for 24 hours using a shale swelling instrument (manufactured by OFITE corporation), and the results are shown in Table 6.
TABLE 6 shale expansion ratio test results (Room temperature)
As can be seen from Table 6, the shale expansion rate of the anti-collapse modified starch prepared in example 1 is reduced by about 25% in a potassium chloride solution for 24 hours, which shows that the anti-collapse modified starch prepared in example 1 has stronger shale expansion inhibition.
Example 13
Using the anti-sloughing modified starch of example 3, the test method was referenced to the standard GB/T16783.1-2014, GBT5005-2001 drilling fluid material specifications, and the experimental results are shown in Table 7 below. (in Table 7, the slurry was evaluation soil).
TABLE 7 evaluation results of anti-sloughing starch products at different temperatures
As can be seen from Table 7, after high temperature treatment, the collapse-preventing starch still has good temperature resistance, the filtration loss and the viscosity performance are basically kept unchanged, and particularly, no obvious viscosity reduction and filtration loss reduction trend exists at 150 ℃, which indicates that the collapse-preventing starch has good performance at 150 ℃ and can be used.
Example 14
2% of the collapse resistant modified starch prepared in example 1 was added to 4% of the puffAnd (5) moistening the soil slurry, and uniformly stirring. Detecting biotoxicity according to GB/T18420.2-2009' method for testing biotoxicity of pollutants for offshore oil exploration and development50The value reaches 174000mg/L, which is far more than the allowable value 30000mg/L of the biological toxicity of the water-based drilling fluid in the first-class sea area required by the standard, and meets the requirement of biological toxicity.
Claims (10)
1. An anti-collapse modified starch for drilling fluid is prepared from starch with the following structural general formula:
the method specifically comprises the following steps:
(1) dissolving starch in low-carbon alcohol to prepare starch suspension, dissolving a quaternary ammonium salt cationic agent and an alkaline catalyst in the starch suspension, and uniformly mixing to obtain starch slurry;
(2) adding a cross-linking agent and a starch acylating agent into the starch slurry, adding an alkaline catalyst for more than two times, heating, and reacting under stirring;
(3) after the reaction is finished, adjusting the pH, washing with low-carbon alcohol, performing suction filtration, and drying to obtain the product;
the starch acylating agent is selected from halogenated carboxylic acid with 2-4 carbon atoms;
the quaternary ammonium salt cationic agent is selected from at least one of alkyl dimethyl benzyl quaternary ammonium salt, alkyl trimethyl quaternary ammonium salt and dialkyl dimethyl quaternary ammonium salt;
wherein the anionic substitution degree of the anti-collapse modified starch for the drilling fluid is within 0.34-0.38 period, and the cationic substitution degree is within 0.39-0.41 period.
2. The preparation method of the anti-collapse modified starch for the drilling fluid, which is characterized by comprising the following steps of:
(1) dissolving starch in low-carbon alcohol to prepare starch suspension, dissolving a quaternary ammonium salt cationic agent and an alkaline catalyst in the starch suspension, and uniformly mixing to obtain starch slurry;
(2) adding a cross-linking agent and a starch acylating agent into the starch slurry, adding an alkaline catalyst for more than two times, heating, and reacting under stirring;
(3) and after the reaction is finished, adjusting the pH, washing with low-carbon alcohol, performing suction filtration, and drying to obtain the catalyst.
3. The preparation method of the anti-collapse modified starch for the drilling fluid, which is characterized by comprising the following steps of:
the ratio of the weight of the starch to the total weight of the alkaline catalyst in the step (1) and the step (2) is (2-4): 1;
in the step (1), the weight ratio of starch in the starch slurry to the alkaline catalyst used in the step (1) is (10-16): 1.
4. the preparation method of the anti-collapse modified starch for the drilling fluid, which is characterized by comprising the following steps of:
the weight ratio of the starch to the quaternary ammonium salt cationic agent is (1-4) to 1.
5. The preparation method of the anti-collapse modified starch for the drilling fluid, which is characterized by comprising the following steps of:
in the step (2), the weight ratio of starch in the starch slurry to the starch acylating agent is (4-5): 1;
in the step (2), the weight ratio of the starch in the starch slurry to the cross-linking agent is (1400-1700): 1.
6. The preparation method of the anti-collapse modified starch for the drilling fluid, which is characterized by comprising the following steps of:
the cross-linking agent is at least one selected from epoxy chloropropane, epoxy propane, methyl epoxy chloropropane, epoxy polydimethylsiloxane, phosphorus oxychloride, sodium trimetaphosphate, adipic acid, sodium tripolyphosphate, hexametaphosphate, formaldehyde and divalent or trivalent mixed anhydride.
7. The preparation method of the anti-collapse modified starch for the drilling fluid, which is characterized by comprising the following steps of:
the starch acylating agent is selected from at least one of chloroacetic acid, bromoacetic acid, dichloroacetic acid, dibromoacetic acid, trichloroacetic acid and tribromoacetic acid.
8. The preparation method of the anti-collapse modified starch for the drilling fluid, which is characterized by comprising the following steps of:
the cross-linking agent is at least one selected from epichlorohydrin, propylene oxide, methyl epichlorohydrin, phosphorus oxychloride, sodium trimetaphosphate, sodium tripolyphosphate, formaldehyde and divalent or trivalent mixed anhydride.
9. The preparation method of the anti-collapse modified starch for the drilling fluid, which is characterized by comprising the following steps of:
the lower alcohol is selected from at least one of methanol, ethanol and propanol;
the starch is selected from at least one of corn starch, cassava starch or potato starch;
in the step (1) and the step (2), the alkaline catalyst is at least one selected from sodium hydroxide and potassium hydroxide.
10. The preparation method of the anti-collapse modified starch for the drilling fluid, which is characterized by comprising the following steps of:
in the step (2), the temperature is raised to 40-70 ℃;
in the step (3), after the reaction is finished, the pH is adjusted to 7.5-9 by using sulfuric acid.
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