CN111718442A - Temperature-sensitive polymer, foam fracturing fluid, and preparation method and application thereof - Google Patents
Temperature-sensitive polymer, foam fracturing fluid, and preparation method and application thereof Download PDFInfo
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- CN111718442A CN111718442A CN201910222325.7A CN201910222325A CN111718442A CN 111718442 A CN111718442 A CN 111718442A CN 201910222325 A CN201910222325 A CN 201910222325A CN 111718442 A CN111718442 A CN 111718442A
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
- C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
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- C08F220/54—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide
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- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/62—Compositions for forming crevices or fractures
- C09K8/66—Compositions based on water or polar solvents
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- C09K8/685—Compositions based on water or polar solvents containing organic compounds containing cross-linking agents
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- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/62—Compositions for forming crevices or fractures
- C09K8/70—Compositions for forming crevices or fractures characterised by their form or by the form of their components, e.g. foams
- C09K8/703—Foams
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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
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/92—Compositions for stimulating production by acting on the underground formation characterised by their form or by the form of their components, e.g. encapsulated material
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Abstract
The invention relates to a temperature-sensitive polymer, a foam fracturing fluid, and a preparation method and application thereof. The temperature-sensitive polymer comprises the following structural unit A, structural unit B, structural unit C and structural unit D derived from a hydrophobic monomer. The temperature sensitivityThe polymer has low viscosity at normal temperature, and the viscosity is not reduced but greatly increased at relatively high temperature of the stratum, and has good foam stability. The foam fracturing fluid has the advantages of good compatibility of all components, good foaming and sand carrying properties, high crack forming efficiency, increased viscosity along with temperature rise, temporary plugging function and wide application prospect in oil field exploitation, particularly in repeated fracturing technology.
Description
Technical Field
The invention belongs to the field of oilfield exploitation, and particularly relates to a temperature-sensitive polymer, a foam fracturing fluid containing the temperature-sensitive polymer, and a preparation method and application of the foam fracturing fluid.
Background
At present, the repeated fracturing technology faces urgent technical requirements no matter in a vertical well or a horizontal well, and no matter in shale or sandstone. Particularly, the repeated fracturing technology is taken as the main technology for cost reduction and efficiency improvement abroad. In other words, by repeating the fracturing to enlarge the first fracture sweep area (achieved by extending the old fracture as it is or creating a new main fracture or new branch fractures), the goal of low drilling while increasing production can be achieved. Further, the repeated fracturing may be not only the second same-well co-layer fracturing but also the third and above repeated fracturing.
The traditional repeated fracturing technology only simply increases the scale of fracturing fluid and proppant, particularly the repeated fracturing of a horizontal well, and if a single-seal double-clamp fracturing pipe column is adopted, the construction displacement is also reduced to a considerable extent compared with the first fracturing. And due to the pressure deficit effect of the stratum caused by long-term production after the first fracturing, the following adverse effects are caused to repeated fracturing: 1) the comprehensive fluid loss coefficient of the stratum is greatly increased, so that the joint forming efficiency of repeated fracturing is low, and even under the condition of reduced discharge capacity, the joint forming is insufficient or an effective crack cannot be formed; 2) the ground stress difference coefficient is further reduced, one or more times of turning can occur in the extension process of the main crack, so that the length of the main crack can not reach the expected target easily, and even the early sand blocking phenomenon is generated due to the multiple times of turning of the main crack. The reason is that the formation pressure decreases much in the direction of the maximum horizontal principal stress and less in the direction of the minimum horizontal principal stress, resulting in a reduced difference between the two horizontal principal stresses. In addition, the presence of the first fracture also generates induced ground stress, increasing more in the direction of minimum horizontal principal stress and less in the direction of maximum horizontal principal stress. Even if the first fractured fracture is partially or completely closed, the induced stress is difficult to completely disappear due to certain plastic characteristics of various reservoirs, namely the so-called residual stress. Although unlike long term production, the first fracture also results in a two-way horizontal principal stress reduction effect. The superposition of the two results in that the ground stress in repeated fracturing tends to be in an isotropic characteristic.
The foam fracturing fluid can greatly reduce the filtration loss, increase the joint forming efficiency, be beneficial to quickly establishing the net pressure in the main crack and be beneficial to quickly extending the main crack so as to avoid one or more steering effects caused by slow extending speed. In addition, the foam liquid has relatively strong sand carrying performance, is convenient for construction with high sand-liquid ratio, and can further reduce the invasion of a water phase during repeated fracturing and the expansion damage caused by the invasion. At present, however, the application of the foam fracturing fluid in the repeated fracturing technology mainly has the following two problems that the conventional foam fracturing fluid has high viscosity at normal temperature, and when the conventional foam fracturing fluid reaches a target layer, the viscosity is reduced due to the rise of the formation temperature, so that the filtration loss is increased; secondly, the foam quality in the conventional foam fracturing fluid is poor, and the foam quality has great influence on the rheological property of the fracturing fluid.
Therefore, research is needed to provide a new temperature-sensitive foam fracturing fluid for repeated fracturing technology to solve the above limitations.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a temperature-sensitive polymer and a preparation method thereof in a first aspect. The temperature-sensitive polymer provided by the invention has lower viscosity at normal temperature, the viscosity is not reduced but greatly increased at the relatively increased temperature of the stratum, and the temperature-sensitive polymer has good foam stability.
A second aspect of the invention provides a foamed fracturing fluid. The foam fracturing fluid provided by the invention has the advantages of good compatibility, foaming and sand carrying properties of all components, high crack forming efficiency, increased viscosity along with temperature rise and temporary plugging function.
In a third aspect of the invention, a method of preparing a foamed fracturing fluid is provided.
In a fourth aspect of the invention, there is provided the use of the foamed fracturing fluid.
According to a first aspect, the present invention provides a temperature-sensitive polymer comprising structural units A, B and C and structural units D derived from a hydrophobic monomer,
wherein R is1-R9Are the same or different and are each independently selected from hydrogen and C1-C6Alkyl, preferably selected from hydrogen, methyl, ethyl, n-propyl and isopropyl; m, n, p and q are 0, 1, 2, 3, 4 or 5.
According to some embodiments of the invention, R1、R2And R3Are all hydrogen.
According to some embodiments of the invention, R4、R5And R6Are all hydrogen.
According to some embodiments of the invention, R7Is hydrogen or C1-C6Alkyl radicals, e.g. methyl, R8And R9Are all hydrogen.
According to some embodiments of the present invention, the hydrophobic monomer comprises at least one of the hydrophobic monomers represented by the structure of formula 1, such as at least one of tetradecyldimethylammonium chloride, hexadecyldimethylallylammonium chloride, or octadecyldimethylammonium chloride,
wherein R is10、R11Same or different, selected from C1-C6Alkyl, preferably selected from methyl, ethyl, n-propyl and isopropyl; r12Is selected from C12-C20Alkyl, preferably selected from C14-C18An alkyl group; r13Is selected from C2-C6Alkenyl, preferably selected from ethenyl, propenyl; m-Is a halide ion, preferably chloride or bromide.
According to some embodiments of the present invention, the ratio of the number of structural units A, B, C and D in the temperature-sensitive polymer is (400- & ltSUB & gt 1000- & ltSUB & gt 500- & ltSUB & gt 900) & ltSUB & gt (4-20) & ltSUB & gt (3-15).
According to some embodiments of the present invention, the temperature-sensitive polymer has a molecular weight of 800-1000 ten thousand.
According to some embodiments of the present invention, a method of preparing a temperature-sensitive polymer comprises the steps of:
a) mixing a compound represented by formula 2, formula 3, and formula 4 and a hydrophobic monomer to form a solution;
wherein R is1-R9Are the same or different and are each independently selected from hydrogen and C1-C6Alkyl, preferably selected from hydrogen, methyl, ethyl, n-propyl and isopropyl; m, n, p and q are 0, 1, 2, 3, 4 or 5
b) Mixing the solution obtained in step a) with a base to form a reaction solution, preferably the reaction solution has a pH of 7.0;
c) introducing an initiator into the reaction liquid obtained in the step b) under an inert atmosphere, and reacting to obtain the colloidal temperature-sensitive polymer.
According to some embodiments of the invention, R1、R2And R3Are all hydrogen.
According to some embodiments of the invention, R4、R5And R6Are all hydrogen.
According to some embodiments of the invention, R7Is hydrogen or C1-C6Alkyl radicals, e.g. methyl, R8And R9Are all hydrogen.
According to some embodiments of the invention, the method further comprises a step d) of drying the colloidal temperature-sensitive polymer obtained in step c). After drying, the temperature-sensitive polymer powder can be obtained by crushing.
According to some embodiments of the present invention, the mass ratio of the compound represented by formula 2, formula 3, and formula 4 to the hydrophobic monomer is (30-70): (40-60): (1-5).
According to some embodiments of the invention, the base is at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide.
According to some embodiments of the present invention, the initiation system comprises an oxidizing agent and a reducing agent, wherein the mass percentage concentration of the initiation system in the reaction system is 0.01-0.10%, and the initiation system comprises an oxidizing agent and a reducing agent, wherein the oxidizing agent is selected from one or more of sodium persulfate, potassium persulfate, ammonium persulfate and hydrogen peroxide, and the reducing agent is selected from one or more of ferrous sulfate, ferrous chloride, sodium sulfite, sodium bisulfite, potassium sulfite and sodium thiosulfate.
In order to be able to better exploit the synergy between the oxidizing agent and the reducing agent in the redox initiation system, according to some embodiments of the invention, the molar ratio of the oxidizing agent to the reducing agent is 1 (0.5-1.5). The oxidizing agent and the reducing agent may be introduced into the reaction system in the form of a solid or may be introduced in the form of an aqueous solution.
According to some embodiments of the invention, the reaction temperature is 40 ℃ to 90 ℃ and the reaction time is 4h to 10 h.
In the method for preparing the above temperature-sensitive polymer according to the present invention, it is preferable to perform the following steps:
sequentially adding four monomers of a compound (such as acrylamide) shown in formula 2, a compound (such as acrylic acid) shown in formula 3, a compound (such as hexafluorobutyl methacrylate) shown in formula 4 and a hydrophobic monomer into deionized water to be dissolved; adding 30% sodium hydroxide aqueous solution into the solution to adjust the pH value to 7.0 to obtain reaction solution; introducing nitrogen to remove oxygen in the reaction liquid; then adding 0.03-0.05% of an initiation system (ammonium persulfate aqueous solution and sodium bisulfite aqueous solution 1:1), and immediately removing oxygen in the reaction solution; and (2) carrying out closed reaction for 4-6 hours at 40-90 ℃ to obtain a colloidal polymer, cutting the colloidal polymer, drying at 50-80 ℃ to constant weight, crushing, and sieving with a 40-mesh standard sieve to obtain the polymer.
The temperature-sensitive polymer provided by the invention has lower viscosity at normal temperature, the viscosity is not reduced but greatly increased at the relatively increased temperature of the stratum, and the temperature-sensitive polymer has better foam stabilizing performance.
According to a second aspect, the present invention provides a foamed fracturing fluid prepared from raw materials including a temperature-sensitive polymer, a clay stabilizer, a foaming agent and a crosslinking agent, or including a temperature-sensitive polymer, a clay stabilizer, a foaming agent and a crosslinking agent.
According to some embodiments of the present invention, the foamed fracturing fluid is prepared from the temperature-sensitive polymer or the temperature-sensitive polymer prepared by the method, a clay stabilizer, a foaming agent and a cross-linking agent, or the foamed fracturing fluid comprises the temperature-sensitive polymer or the temperature-sensitive polymer prepared by the method, a clay stabilizer, a foaming agent and a cross-linking agent.
According to some embodiments of the present invention, the content of each component is, in mass percent, 0.1 to 1.0%, preferably 0.4 to 0.6%; clay stabilizers from 0.1 to 1.0%, preferably from 0.3 to 0.5%; the foaming agent is 0.1-1.0%, preferably 0.2-0.4%; the crosslinking agent is 0.1-1.0%, preferably 0.4-0.6%.
According to some embodiments of the present invention, the clay stabilizer comprises a chloride salt and/or one of the compounds represented by the structure of formula 5,
in the formula 5, R14Is selected from C1-C20Alkyl or hydroxy substituted C1-C20Alkyl, preferably selected from C12-C18Alkyl or hydroxy substituted C2-C6An alkyl group; r15、R16And R17Same or different, selected from C1-C4Alkyl, preferably selected from methyl, ethyl, n-propyl and isopropyl; q-Is a halide ion, preferably chloride or bromide.
According to some embodiments of the invention, the chloride salt is selected from at least one of potassium chloride, ammonium chloride, calcium chloride, magnesium chloride and sodium chloride.
According to some embodiments of the present invention, the compound represented by the structure of formula 5 is at least one selected from the group consisting of choline chloride, polyisopropoxydimethylammonium chloride, and cetyltrimethylammonium chloride.
According to some embodiments of the present invention, the mass ratio of the chloride salt to the compound represented by the structure of formula 5 is 1 (0.5-2.0).
According to some embodiments of the invention, the blowing agent comprises a compound of formula 6, a compound of formula 7, and C1-C6One or two of alkyl alcohol.
According to some embodiments of the present invention, the blowing agent comprises a compound represented by formula 6 and a compound represented by formula 7,
in the formula 6, R is selected from C1-C20Alkyl or halogen substituted C1-C20Alkyl, preferably selected from C12-C18Alkyl or halogen substituted C12-C18An alkyl group, a carboxyl group,
in the formula 7, R18-R20Same or different, selected from C1-C20Alkyl, preferably R18Is C1-C20Alkyl radical, R19And R20Identical or different, are methyl, ethyl, n-propyl and isopropyl, more preferably R18-R20Are all methyl.
According to some embodiments of the invention, the foaming agent comprises at least one selected from the group consisting of laureth, perfluorolaureth, tetradeceth, and hexadecyl polyetheth, and at least one selected from the group consisting of dodecyl dimethyl betaine, tetradecyl dimethyl betaine, and betaine.
According to some embodiments of the present invention, the mass ratio of the compound represented by formula 6 to the compound represented by formula 7 is 1 (1-10).
According to some embodiments of the present invention, the mass ratio of the compound represented by formula 6 to the compound represented by formula 7 is 1 (4-6).
According to some embodiments of the invention, the crosslinking agent comprises a titanium-containing compound, C1-C6And C is an organic acid1-C6And one or more of the polyols and derivatives thereof.
According to some embodiments of the invention, the crosslinking agent comprises a titanium-containing compound, C1-C6And C is an organic acid1-C6The polyol of (1) and derivatives thereof.
According to some embodiments of the invention, the crosslinking agent comprises 1) at least one selected from the group consisting of titanium tetrachloride, titanium sulfate, titanium sulfite, and butyl titanate; 2) is selected from C1-C6At least one of organic acids of (a), such as at least one of formic acid, acetic acid and lactic acid; and 3) is selected from C1-C6At least one of the polyhydric alcohols and derivatives thereof of (a), for example at least one of ethylene glycol, glycerol and triethanolamine,
according to some embodiments of the invention, the titanium-containing compound, C1-C6And C is an organic acid1-C6The mass ratio of the polyhydric alcohol and the derivative thereof is 1 (2-10) to 1-5.
According to some embodiments of the invention, the titanium-containing compound, C1-C6And C is an organic acid1-C6The mass ratio of the polyhydric alcohol and the derivative thereof is 1 (4-8) to 2-4.
According to a third aspect, the invention provides a preparation method of the foam fracturing fluid, which comprises the following steps:
s1, adding a temperature-sensitive polymer into water to dissolve to obtain a solution;
s2, adding a clay stabilizer, a foaming agent and a cross-linking agent into the solution obtained in the step S1 to obtain a base solution;
s3, introducing CO into the base liquid obtained in the step S22And (4) gas to obtain the foam fracturing fluid.
Advantageously, in step S2, a clay stabilizer, a foaming agent and a crosslinking agent are sequentially added to the solution obtained in step S1 in this order.
According to a fourth aspect, the present invention provides the use of the foamed fracturing fluid described above or the foamed fracturing fluid prepared by the method described above in oilfield exploitation, in particular in a repeated fracturing technique.
The foam fracturing fluid provided by the invention is suitable for repeated fracturing of shale, sandstone or other reservoirs, and has the advantages of greatly reducing filtration loss, increasing fracture-making efficiency, being beneficial to quickly establishing net pressure in a main fracture, being beneficial to quickly extending the main fracture and avoiding one or more steering effects caused by slow extension speed. In addition, the foam liquid has relatively strong sand carrying performance, is convenient for construction with high sand-liquid ratio, and can further reduce the invasion of a water phase during repeated fracturing and the expansion damage caused by the invasion.
The temperature-sensitive foam fracturing fluid is mainly used, the viscosity of the fracturing fluid is not reduced but greatly increased along with the increase of the temperature, the temperature of the front edge of a crack is relatively highest and is equal to the original static temperature of a reservoir, and the viscosity of the fracturing fluid is greatly increased, so that the complete temporary plugging operation can be performed at the end part of the crack, and the method is equivalent to the conventional end sand-removing fracturing. The foam liquid has relatively high viscosity, the viscosity is further increased under the action of reservoir temperature, complete plugging effect can be realized in the height direction of the seam end due to low density, the net pressure of the main fracture is further and greatly increased, and a large amount of steering branch fractures and even micro fractures can be promoted to be generated in the subsequent low-viscosity conventional fracturing liquid (generally slick water).
By enlarging the first fracture sweep area by repeated fracturing (by extending the old fracture as it is or creating a new main fracture or new branch fractures), the goal of low drilling while increasing production can be achieved. Moreover, the repeated fracturing not only can be the second same-well same-layer fracturing, but also can be the third or more repeated fracturing, and has wide application prospect.
Detailed Description
The invention will now be further illustrated by means of specific examples, but it will be understood that the scope of the invention is not limited thereto.
The reagent materials adopted in the specific embodiment of the invention are all commercially available raw materials except that the temperature-sensitive polymer is self-made.
Example 1
This example is a preparation of a foamed fracturing fluid system consisting of: temperature sensitive polymer 0.4%, clay stabilizer 0.3%, foaming agent 0.2%, cross-linking agent 0.4%, water 98.7%, CO2A gas.
The clay stabilizer is KCl and choline chloride, and the mass ratio of the KCl to the choline chloride is 1: 1; the foaming agent is perfluoro lauryl polyoxyethylene ether and betaine, and the mass ratio of the perfluoro lauryl polyoxyethylene ether to the betaine is 1: 5; the cross-linking agent is tetrabutyl titanate, lactic acid and ethylene glycol, and the mass ratio of the tetrabutyl titanate, the lactic acid and the ethylene glycol is 1:6: 3.
Preparation of temperature-sensitive polymer:
sequentially adding four monomers of acrylamide, acrylic acid, hexafluorobutyl methacrylate and hexadecyl dimethyl allyl ammonium chloride into deionized water to be used as a total monomer until the monomers are dissolved; the reaction solution comprises, by mass, 30% of total monomers, 50 parts of acrylamide, 45 parts of acrylic acid, 3 parts of hexafluorobutyl methacrylate and 2 parts of hexadecyl dimethyl allyl ammonium chloride; adding 30% sodium hydroxide aqueous solution into the solution to adjust the pH value to 7.0 to obtain reaction solution; introducing nitrogen to remove oxygen in the reaction liquid; then adding 0.03% of an initiation system (ammonium persulfate aqueous solution and sodium bisulfite aqueous solution 1:1), and immediately removing oxygen in the reaction solution; the gel polymer is obtained after the closed reaction for 5 hours at the temperature of 60 ℃, the gel polymer is cut up, then the gel polymer is dried to constant weight at the temperature of 70 ℃, and then the gel polymer is crushed and passes through a standard sieve of 40 meshes to obtain the temperature-sensitive polymer with the molecular weight of 1000 ten thousand (wherein the measuring method of the molecular weight adopts a GBT12005.10-92 polyacrylamide molecular weight viscosity measuring method).
Taking preparation of 1L of foam fracturing fluid as an example, the preparation method comprises the following steps:
1) 4g of temperature-sensitive polymer is slowly added into the aqueous solution under the stirring condition of 1000rpm, and the stirring is continuously carried out for 10min at 800rpm, so that the temperature-sensitive polymer is completely dissolved.
2) Under the condition of continuous stirring at 800rpm, 3g of clay stabilizer is sequentially added until the mixture is completely and uniformly mixed, and 2g of foaming agent is added and uniformly mixed.
3) Pouring the solution prepared in the step 2) into a Wuyi mixing and blending device, adding 4g of cross-linking agent, covering and sealing, and using CO2And (3) slowly introducing air into the solution by an air source, adjusting the rotating speed of the mixer to 1000rpm, and stopping stirring for 5min to obtain the foam fracturing fluid.
The foam fracturing fluid obtained above was immediately poured into a 5000mL graduated cylinder, and the volume of the foam was read as 70% with a foam half-life of 90 min.
Preparing 1L of foam fracturing fluid by the same method, testing the initial viscosity of the prepared foam fracturing fluid to 803mPa.s by using a BROOKFIELDHEOMETER (DV3T) rheometer, and heating to 100 ℃ to obtain the foam fracturing fluid with the viscosity of 1027mPa.s (wherein the specific test method of the viscosity refers to the instrument operation specification).
Example 2
This example is a preparation of a foamed fracturing fluid system consisting of: temperature sensitive polymer 0.5%, clay stabilizer 0.3%, foaming agent 0.2%, cross-linking agent 0.5%, water 98.5%, CO2A gas.
The clay stabilizer is KCl and choline chloride, and the mass ratio of the KCl to the choline chloride is 1: 1; the foaming agent is perfluoro lauryl polyoxyethylene ether and betaine, and the mass ratio of the perfluoro lauryl polyoxyethylene ether to the betaine is 1: 5; the cross-linking agent is tetrabutyl titanate, lactic acid and ethylene glycol, and the mass ratio of the tetrabutyl titanate, the lactic acid and the ethylene glycol is 1:6: 3.
Preparation of temperature-sensitive polymer:
sequentially adding four monomers of acrylamide, acrylic acid, hexafluorobutyl methacrylate and hexadecyl dimethyl allyl ammonium chloride into deionized water to be used as a total monomer until the monomers are dissolved; the reaction solution comprises, by mass, 30% of total monomers, 50 parts of acrylamide, 45 parts of acrylic acid, 3 parts of hexafluorobutyl methacrylate and 2 parts of hexadecyl dimethyl allyl ammonium chloride; adding 30% sodium hydroxide aqueous solution into the solution to adjust the pH value to 7.0 to obtain reaction solution; introducing nitrogen to remove oxygen in the reaction liquid; then adding 0.04% of an initiating system (ammonium persulfate aqueous solution and sodium bisulfite aqueous solution 1:1), and immediately removing oxygen in the reaction solution; the gel polymer is obtained after the closed reaction for 5 hours at the temperature of 60 ℃, the gel polymer is cut up, then the gel polymer is dried to constant weight at the temperature of 70 ℃, then the gel polymer is crushed, and the temperature-sensitive polymer is obtained by passing through a standard sieve of 40 meshes, wherein the molecular weight of the temperature-sensitive polymer is 900 ten thousand (the method for measuring the molecular weight adopts a GBT12005.10-92 polyacrylamide molecular weight viscosity measurement method).
Taking preparation of 1L of foam fracturing fluid as an example, the preparation method comprises the following steps:
1) 5g of temperature-sensitive polymer is slowly added into the aqueous solution under the stirring condition of 1000rpm, and the stirring is continuously carried out for 10min at 800rpm, so that the temperature-sensitive polymer is completely dissolved.
2) Under the condition of continuous stirring at 800rpm, 3g of clay stabilizer is sequentially added until the mixture is completely and uniformly mixed, and 2g of foaming agent is added and uniformly mixed.
3) Pouring the solution prepared in the step 2) into a Wuyi mixing device, adding 5g of cross-linking agent, covering and sealing, and using CO2And (3) slowly introducing air into the solution by an air source, adjusting the rotating speed of the mixer to 1000rpm, and stopping stirring for 5min to obtain the foam fracturing fluid.
The foamed fracturing fluid obtained above was immediately poured into a 5000mL graduated cylinder, and the volume of the foam read was 76% and the foam half-life was 96min 8'.
Preparing 1L of foam fracturing fluid by the same method, testing the initial viscosity of the prepared foam fracturing fluid to be 853mPa.s by using a BROOKFIELDHEOMETER DV3T rheometer, and heating to 100 ℃ to obtain the foam fracturing fluid with the viscosity of 1112mPa.s (wherein the specific test method of the viscosity refers to the operation specification of the instrument).
Example 3
This example is a preparation of a foamed fracturing fluid system consisting of: 0.6% of temperature-sensitive polymer, 0.3% of clay stabilizer, 0.2% of foaming agent, 0.6% of cross-linking agent, 98.3% of water, CO2A gas.
The clay stabilizer is KCl and choline chloride, and the mass ratio of the KCl to the choline chloride is 1: 1; the foaming agent is perfluoro lauryl polyoxyethylene ether and betaine, and the mass ratio of the perfluoro lauryl polyoxyethylene ether to the betaine is 1: 5; the cross-linking agent is tetrabutyl titanate, lactic acid and ethylene glycol, and the mass ratio of the tetrabutyl titanate, the lactic acid and the ethylene glycol is 1:6: 3.
Preparation of temperature-sensitive polymer:
sequentially adding four monomers of acrylamide, acrylic acid, hexafluorobutyl methacrylate and hexadecyl dimethyl allyl ammonium chloride into deionized water to be used as a total monomer until the monomers are dissolved; the reaction solution comprises, by mass, 30% of total monomers, 50 parts of acrylamide, 45 parts of acrylic acid, 3 parts of hexafluorobutyl methacrylate and 2 parts of hexadecyl dimethyl allyl ammonium chloride; adding 30% sodium hydroxide aqueous solution into the solution to adjust the pH value to 7.0 to obtain reaction solution; introducing nitrogen to remove oxygen in the reaction liquid; then adding 0.05% of an initiation system (ammonium persulfate aqueous solution and sodium bisulfite aqueous solution 1:1), and immediately removing oxygen in the reaction solution; the gel polymer is obtained after the reaction is closed for 5 hours at the temperature of 60 ℃, the gel polymer is cut up, then the gel polymer is dried to constant weight at the temperature of 70 ℃, then the gel polymer is crushed, and the temperature-sensitive polymer is obtained by passing through a standard sieve of 40 meshes, wherein the molecular weight of the temperature-sensitive polymer is 800 ten thousand (the method for measuring the molecular weight adopts a GBT12005.10-92 polyacrylamide molecular weight viscosity measurement method).
Taking preparation of 1L of foam fracturing fluid as an example, the preparation method comprises the following steps:
1) 6g of temperature-sensitive polymer is slowly added into the aqueous solution under the stirring condition of 1000rpm, and the stirring is continuously carried out for 10min at 800rpm, so that the temperature-sensitive polymer is completely dissolved.
2) Under the condition of continuous stirring at 800rpm, 3g of clay stabilizer is sequentially added until the mixture is completely and uniformly mixed, and 2g of foaming agent is added and uniformly mixed.
3) Pouring the solution prepared in the step 2) into a Wuyi mixing and blending device, adding 6g of cross-linking agent, covering and sealing, and using CO2And (3) slowly introducing air into the solution by an air source, adjusting the rotating speed of the mixer to 1000rpm, and stopping stirring for 5min to obtain the foam fracturing fluid.
The foamed fracturing fluid obtained above was immediately poured into a 5000mL graduated cylinder, and the volume of the foam read was 73% and the foam half-life was 93min 30'.
Preparing 1L of foam fracturing fluid by the same method, testing the initial viscosity of the prepared foam fracturing fluid to 911mPa.s by using a BROOKFIELDHEOMETER DV3T rheometer, and heating to 100 ℃ to 1186mPa.s (wherein the specific test method of the viscosity refers to the instrument operation specification).
It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not set any limit to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.
Claims (10)
1. A temperature-sensitive polymer comprising the following structural unit A, structural unit B and structural unit C and structural unit D derived from a hydrophobic monomer,
wherein R is1-R9Are the same or different and are each independently selected from hydrogen and C1-C6Alkyl, preferably selected from hydrogen, methyl, ethyl, n-propyl and isopropyl; m, n, p and q are each 0, 1, 2, 3, 4 or 5.
2. The temperature-sensitive polymer according to claim 1, wherein the hydrophobic monomer comprises at least one of the hydrophobic monomers represented by the structure of formula 1, such as at least one of tetradecyldimethylammonium chloride, hexadecyldimethylallylammonium chloride, or octadecyldimethylammonium chloride,
wherein R is10、R11Are the same or different and are each independently selected from C1-C6Alkyl, preferably selected from methyl, ethyl, n-propyl and isopropyl; r12Is selected from C12-C20Alkyl, preferably selected from C14-C18An alkyl group; r13Is selected from C2-C6Alkenyl, preferably selected from ethenyl, propenyl; m-Is a halide ion, preferably chloride or bromide.
3. The temperature-sensitive polymer according to claim 1 or 2, wherein the ratio of the number of structural units A, B, C and D is (400- > 1000): (500- > 900): (4-20): (3-15); and/or, the polymer has a molecular weight of 800-.
4. The method for producing a temperature-sensitive polymer according to any one of claims 1 to 3, comprising the steps of:
a) mixing the compounds represented by formula 2, formula 3 and formula 4 and a hydrophobic monomer to form a solution,
wherein, to R1-R9M, n, p and q are as defined in claim 1;
b) mixing the solution obtained in step a) with a base to form a reaction solution, preferably the reaction solution has a pH of 7.0;
c) introducing an initiating system into the reaction liquid obtained in the step b) under an inert atmosphere, and reacting to obtain the colloidal temperature-sensitive polymer;
optionally, d) drying and pulverizing the gel-like temperature-sensitive polymer obtained in step c).
5. The method of claim 4, wherein the mass ratio of the compound represented by formula 2, formula 3 and formula 4 to the hydrophobic monomer is (30-70): (40-60): (1-5);
and/or the alkali is at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide;
and/or the mass percentage concentration of the initiation system in the reaction system is 0.01-0.10%, the initiation system comprises an oxidizing agent and a reducing agent, wherein the oxidizing agent is selected from one or more of sodium persulfate, potassium persulfate, ammonium persulfate and hydrogen peroxide, the reducing agent is selected from one or more of ferrous sulfate, ferrous chloride, sodium sulfite, sodium bisulfite, potassium sulfite and sodium thiosulfate, and preferably, the molar ratio of the oxidizing agent to the reducing agent is 1 (0.5-1.5);
and/or the reaction temperature is 40-90 ℃, and the reaction time is 4-10 h.
6. The foam fracturing fluid is prepared from raw materials including a temperature-sensitive polymer, a clay stabilizer, a foaming agent and a cross-linking agent, or comprises the temperature-sensitive polymer, the clay stabilizer, the foaming agent and the cross-linking agent.
7. A foamed fracturing fluid, which is prepared from raw materials including the temperature-sensitive polymer according to any one of claims 1 to 3 or the temperature-sensitive polymer prepared by the method according to any one of claims 4 to 5, a clay stabilizer, a foaming agent and a crosslinking agent,
or the foamed fracturing fluid comprises the temperature-sensitive polymer according to any one of claims 1 to 3 or the temperature-sensitive polymer prepared according to the method of any one of claims 4 to 5, a clay stabilizer, a foaming agent and a crosslinking agent.
8. The foam fracturing fluid according to claim 6 or 7, wherein the content of the temperature-sensitive polymer is 0.1-1.0% by mass, preferably 0.4-0.6% by mass; clay stabilizers from 0.1 to 1.0%, preferably from 0.3 to 0.5%; the foaming agent is 0.1-1.0%, preferably 0.2-0.4%; 0.1 to 1.0 percent of cross-linking agent, preferably 0.4 to 0.6 percent;
and/or the clay stabilizer comprises a chloride salt and/or a compound shown in a structure of a formula 5, preferably at least one selected from potassium chloride, ammonium chloride, calcium chloride, magnesium chloride and sodium chloride and at least one compound shown in a structure of a formula 5, wherein the compound shown in a structure of a formula 5 is at least one selected from choline chloride, poly (isopropanoldimethyl ammonium chloride) and hexadecyltrimethyl ammonium chloride, preferably the mass ratio of the chloride salt to the compound shown in a structure of a formula 5 is 1 (0.5-2.0),
in the formula 5, R14Is selected from C1-C20Alkyl or hydroxy substituted C1-C20Alkyl, preferably selected from C12-C18Alkyl or hydroxy substituted C2-C6An alkyl group; r15、R16And R17Are the same or different and are each independently selected from C1-C4Alkyl, preferably selected from methyl, ethyl, n-propyl and isopropyl; q-Is a halide ion, preferably chloride or bromide;
and/or the foaming agent comprises a compound shown as a formula 6, a compound shown as a formula 7 and C1-C6One or two of the alkyl alcohols preferably include a compound represented by formula 6 and a compound represented by formula 7, more preferably include at least one selected from the group consisting of laureth, perfluorolaureth, tetradeceth and hexadecyl polyoxyethylene, and dodecyl dimethylAt least one of betaine, tetradecyldimethyl betaine and betaine, preferably the mass ratio of the compound shown in the formula 6 to the compound shown in the formula 7 is 1 (1-10), preferably 1 (4-6),
in the formula 6, R is selected from C1-C20Alkyl or halogen substituted C1-C20Alkyl, preferably selected from C12-C18Alkyl or halogen substituted C12-C18An alkyl group, a carboxyl group,
in the formula 7, R18-R20Are the same or different and are each independently selected from C1-C20Alkyl, preferably R18Is C1-C20Alkyl radical, R19And R20Identical or different, each independently of the others, methyl, ethyl, n-propyl and isopropyl, more preferably R18-R20Are both methyl;
and/or the cross-linking agent comprises a titanium-containing compound, C1-C6And C is an organic acid1-C6At least one or more, preferably three,
preferably, the crosslinking agent includes 1) at least one selected from titanium tetrachloride, titanium sulfate, titanium sulfite, and butyl titanate; 2) is selected from C1-C6At least one of organic acids of (a), such as at least one of formic acid, acetic acid and lactic acid; and 3) is selected from C1-C6At least one of the polyhydric alcohols and derivatives thereof of (a), for example at least one of ethylene glycol, glycerol and triethanolamine,
preferably, the titanium-containing compound, C1-C6And C is an organic acid1-C6The mass ratio of the polyhydric alcohol and the derivative thereof is 1 (2-10) to (1-5), preferably 1 (4-8) to (2-4).
9. A method of preparing a foamed fracturing fluid according to any of claims 6 to 8, comprising the steps of:
s1, adding a temperature-sensitive polymer into water to dissolve to obtain a solution;
s2, adding a clay stabilizer, a foaming agent and a cross-linking agent into the solution obtained in the step S1 to obtain a base solution;
s3, introducing CO into the base liquid obtained in the step S22Gas to obtain the foam fracturing fluid,
preferably, in step S2, a clay stabilizer, a foaming agent, and a crosslinking agent are sequentially added to the solution obtained in step S1 in this order.
10. Use of a foamed fracturing fluid according to any of claims 6 to 8 or prepared according to the method of claim 9 in oilfield exploitation, in particular in repeated fracturing techniques.
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