A salt-responsive high-temperature resistant drilling fluid viscosity enhancer and its preparation method and application

Abstract

The present invention discloses a salt-responsive high-temperature resistant drilling fluid thickener, a preparation method thereof, and an application thereof. The salt-responsive high-temperature resistant drilling fluid thickener comprises a first side chain, a second side chain, a third side chain, and a fourth side chain, the number ratio of the four being (5-9): (3-5): (1-2): (0.2-0.4); the weight average molecular weight of the salt-responsive high-temperature resistant drilling fluid thickener is 1.0×10 7 ~3×10 7 The thickener can resist salt until it is saturated with salt at 180℃, and still has good salt resistance and thickening effect at 200℃.

Description

Technical Field

[0001] The invention relates to a salt-responsive high-temperature resistant drilling fluid viscosity enhancer, a preparation method and application thereof, and belongs to the technical field of drilling fluid treatment agents for petroleum exploration and development. Background Art

[0002] With the gradual advancement of oil and gas exploration and development, deep and ultra-deep well oil and gas field drilling will become the main battlefield for my country's oil and gas resources. The deep and ultra-deep formation environment is extremely complex, often accompanied by extreme conditions such as high temperature and high salinity. The drilling fluid is easily contaminated by salt during the drilling process, resulting in poor system performance and causing underground safety accidents such as well wall instability, leakage, and drill stuck.

[0003] The performance of drilling fluids is closely linked to their core treatment agents. Viscosifiers, as key treatment agents for solid-free and saturated brine drilling fluids, regulate the system's rheological properties. To ensure clean wellbore and safe drilling, drilling fluids must exhibit excellent rheological properties and suspension stability, with viscosity and shear forces maintained within appropriate ranges. Increasing the bentonite content can improve drilling fluid viscosity and shear forces. However, excessive bentonite content increases the low-density solids content of the drilling fluid, hindering the achievement of low solids and improving ROP. To ensure the viscosity, shear force, and shear-thinning properties of low-solids polymer drilling fluids, viscosifiers are the preferred choice. Currently, conventional polymer viscosifiers include 80A51, xanthan gum (XC), carboxyethyl cellulose (HEC), and polyacrylamide. These have limited applicable temperature and salt tolerances, necessitating the development of high-temperature and salt-resistant viscosifiers specifically for deep salt-gypsum formations.

[0004] The Chinese invention patent application with application number 2022105687433 and application date July 29, 2022 discloses an environmentally friendly high-temperature and salt-resistant thickener for water-based drilling fluid, and its preparation method and application. The preparation method includes the steps of: adding olefin monomers, anionic monomers, and cationic monomers to water, stirring evenly to obtain aqueous phase A; adding cross-linking monomers, emulsifiers and ester monomers to white oil, emulsifying to obtain oil phase B; mixing aqueous phase A and oil phase B, emulsifying, and adjusting the pH of the system to 6-9 to obtain an emulsion; adding an initiator aqueous solution under a nitrogen atmosphere to react; after the reaction is completed, using acetone for precipitation, filtering, washing, and drying to obtain an environmentally friendly high-temperature and salt-resistant thickener for water-based drilling fluid. The drilling fluid thickener has the following disadvantages: (1) insufficient high temperature resistance. The thickener polymer molecular chain is easily thermally degraded and ineffective under high temperature conditions, resulting in poor high temperature resistance; (2) the drilling fluid thickener has poor salt resistance. Due to the polyelectrolyte effect, the polymer molecular chain stretches in water, but curls in salt water, and its solubility becomes poor, resulting in the loss of thickening performance. Summary of the Invention

[0005] The present invention provides a salt-responsive high-temperature resistant drilling fluid thickener, a preparation method and an application thereof, aiming to solve the problem that existing drilling fluid thickeners are easily degraded in high-temperature environments and have poor stability in high-salt environments, resulting in decreased viscosity.

[0006] In order to achieve the above objectives, the first aspect of the present invention provides a salt-responsive high-temperature resistant drilling fluid viscosity enhancer, wherein the salt-responsive high-temperature resistant drilling fluid viscosity enhancer is a high molecular polymer, comprising a first side chain, a second side chain, a third side chain, and a fourth side chain, wherein the number ratio of the four side chains is (5-9): (3-5): (1-2): (0.2-0.4);

[0007] The first side chain is -R1, R1 is an amide, carboxylic acid or carboxylate having 1 to 3 carbon atoms;

[0008] The second side chain is -R2, R2 is a sulfonic acid or sulfonate having 5 to 10 carbon atoms;

[0009] The third side chain is -R3, where R3 is an amine salt having 5 to 10 carbon atoms;

[0010] The fourth side chain is -R4, where R4 is at least one of an amide, a carboxylate, and an alcohol ester having 16 to 18 carbon atoms;

[0011] The weight average molecular weight of the salt-responsive high-temperature drilling fluid viscosity enhancer is 1.0×10 7 ~3×10 7 .

[0012] In some embodiments of the present invention, the salt-responsive high-temperature resistant drilling fluid viscosifier has the structural formula:

[0013]

[0014] m:n:x:y:z=(4~5):(4~5):(3-5):(1-2):(0.2-0.4), R=C16~C18 alkyl.

[0015] A second aspect of the present invention provides a method for preparing a salt-responsive high-temperature resistant drilling fluid viscosifier, comprising a free radical micelle polymerization step, in which the following items are contacted in an aqueous solution: a terminal olefin hydrophilic monomer, a terminal olefin hydrophobic monomer, a terminal olefin ammonium salt, a terminal olefin sulfonic acid or its salt, an initiator, and a surfactant, wherein the molar ratio of the terminal olefin hydrophilic monomer, the terminal olefin hydrophobic monomer, the terminal olefin ammonium salt, and the terminal olefin sulfonic acid or its salt is (5-9): (0.2-0.4): (1-2): (3-5).

[0016] In some embodiments of the present invention, the terminal olefin hydrophilic monomer is one or more of acrylamide, sodium acrylate, methacrylamide, and N,N-dimethylacrylamide;

[0017] The terminal olefin hydrophobic monomer is one or more of N-octadecyl acrylamide, hexadecyl methacrylate, and octadecyl methacrylate;

[0018] The terminal olefin ammonium salt is one or more of diallyldimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride, methacryloylpropyltrimethylammonium chloride, and dodecyl / hexadecyldimethylallylammonium chloride;

[0019] The terminal olefin sulfonic acid is one or more of 2-acrylamido-2-methyl-1-propanesulfonic acid, 2-acrylamidododecanesulfonic acid, sodium vinyl sulfonate, sodium styrene sulfonate, and allyl sulfonic acid.

[0020] In some embodiments of the present invention, the temperature of the free radical micelle polymerization step is 40-65°C.

[0021] In some embodiments of the present invention, the pH of the aqueous solution is 7-9.

[0022] A third aspect of the present invention provides the use of the above-mentioned salt-responsive high-temperature resistant drilling fluid viscosifier in the field of deep and ultra-deep drilling.

[0023] A fourth aspect of the present invention provides a drilling fluid comprising the above-mentioned salt-responsive high-temperature resistant viscosity enhancer.

[0024] In some embodiments of the present invention, the drilling fluid includes bentonite, the above-mentioned salt-responsive high-temperature resistant viscosity enhancer, sodium chloride, a fluid loss control agent, and barite.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] (1) The salt-responsive high-temperature resistant drilling fluid thickener provided by the present invention has a special anti-polyelectrolyte effect and salt-responsive characteristics, realizing the transformation from traditional "salt resistance" to "salt affinity", and providing a new idea for the research and development of salt-resistant drilling fluid treatment agents; the thickener of the present invention has high-temperature resistance and salt resistance properties, and can be applied to deep well high-temperature and salt-gypsum formations; experiments have shown that the salt-responsive high-temperature resistant drilling fluid thickener of the present invention can resist temperatures up to 180°C, can resist salt to salt saturation, and still has good effects at 200°C.

[0027] (2) The viscosity enhancer of the present invention has excellent salt-responsive viscosity enhancement properties. With the addition of electrolyte salts, the molecular chains of the viscosity enhancer solution of the present invention stretch, the fluid dynamics size increases, and a regular and dense spatial network structure is formed, thereby increasing the viscosity of the drilling fluid. The viscosity enhancer of the present invention plays a very important role in solving problems such as dynamic cuttings carryover, static cuttings suspension, and improving the mechanical drilling speed during drilling.

[0028] (3) The viscosity enhancer of the present invention can be used as a saturated brine-based slurry viscosity enhancer. The viscosity retention rate of 1 wt% viscosity enhancer + saturated NaCl solution after aging at 200°C is greater than 61%. When 1 wt% viscosity enhancer is added to the saturated brine drilling fluid, the fluid still maintains a relatively high apparent viscosity after aging at a high temperature of 200°C, and also has a certain filtration loss reduction effect. Under high temperature and high salt conditions, the saturated brine drilling fluid still maintains good rheological properties and can effectively cope with drilling conditions in deep salt-gypsum layers.

[0029] (4) The drilling fluid provided by the present invention has excellent shear thinning properties, viscoelasticity and a stable internal space structure. The saturated brine drilling fluid can maintain good rheological properties under high temperature and high salinity conditions, and has obvious viscosity-enhancing and shear-enhancing effects. It can be used for suspending and carrying cuttings during drilling in high-friction formations and long horizontal sections, cleaning wellbores, preventing sand settling and drill bit jamming, and increasing drilling speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 : Schematic diagram of preparing a tackifier according to an embodiment of the present invention.

[0032] Figure 2 : Viscosity change of thickener after high temperature aging in saturated NaCl aqueous solution for 16 hours. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0034] For simplicity, the present invention only explicitly discloses certain numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range. Similarly, any upper limit can be combined with any other upper limit to form an unspecified range. In addition, although not explicitly stated, each point or individual value between the endpoints of a range is included in the range. Thus, each point or individual value can serve as its own lower limit or upper limit and be combined with any other point or individual value, or with other lower limits or upper limits, to form an unspecified range.

[0035] It should be noted that, in the description of the present invention, unless otherwise specified, "above" and "below" are inclusive, and the meaning of "multiple" in "one or more" is two or more. Relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the presence of other identical elements in the process, method, article or device comprising the elements.

[0036] In the description of the present invention, the description with reference to the terms "any embodiment / method", "one embodiment / method", "some embodiments / methods", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described may be combined in an appropriate manner in any one or more embodiments / methods or examples. In addition, those skilled in the art may combine and combine different embodiments / methods or examples and features of different embodiments / methods or examples described in this specification, unless they are contradictory.

[0037] In the present invention, according to the provisions of GB / T 16783.1-2014 "Field Testing of Drilling Fluids in the Petroleum and Natural Gas Industry Part 1: Water-Based Drilling Fluids", the terms "apparent viscosity", "plastic viscosity" and "dynamic shear force" are defined as follows:

[0038] Apparent viscosity: also known as effective viscosity or apparent viscosity, is the ratio of shear stress to velocity gradient of drilling fluid under a certain velocity gradient, expressed as "AV" and the unit is m Pa·s (milliPascals·second).

[0039] Plastic viscosity: When the drilling fluid is in laminar flow, the sum of various internal frictions between solid particles, between solid particles and liquid molecules, and between liquid molecules in the drilling fluid is called the plastic viscosity of the drilling fluid, expressed as "PV" and the unit is m Pa·s (milliPascal·second) or cP (centipoise), 1m Pa·s = lcP.

[0040] Dynamic shear stress: The dynamic shear stress of drilling fluid reflects the magnitude of the interaction force between clay particles and polymer molecules when the drilling fluid is in laminar flow, that is, the strength of the network structure formed inside the drilling fluid. It is expressed as "YP" or "T" and the unit is Pa (Pascal).

[0041] High-temperature and high-pressure fluid loss: refers to the fluid loss of drilling fluid under specific high temperature and high pressure, tested according to the provisions of GB / T 16783.1-2014, and expressed as "FL HTHP " indicates that the unit is mL.

[0042] in:

[0043] AV=1 / 2×Φ 600

[0044] PV=Φ 600 -Φ 300

[0045] YP=1 / 2×(Φ 300 -PV)

[0046] The above summary of the present invention is not intended to describe each disclosed embodiment of the present invention.

[0047] The following description further illustrates exemplary embodiments. These embodiments can be used in various combinations. In each example, the examples are listed only as representative groups and should not be interpreted as exhaustive.

[0048] Tackifier:

[0049] The salt-responsive high-temperature resistant drilling fluid viscosity enhancer provided by the present invention is a high molecular polymer, comprising a first side chain, a second side chain, a third side chain and a fourth side chain, wherein the number ratio of the four side chains is (5-9): (3-5): (1-2): (0.2-0.4);

[0050] The first side chain is -R1, R1 is an amide, carboxylic acid or carboxylate having 1 to 3 carbon atoms;

[0051] The second side chain is -R2, R2 is a sulfonic acid or sulfonate having 5 to 10 carbon atoms;

[0052] The third side chain is -R3, where R3 is an amine salt having 5 to 10 carbon atoms;

[0053] The fourth side chain is -R4, where R4 is at least one of an amide, a carboxylate, and an alcohol ester having 16 to 18 carbon atoms;

[0054] The weight average molecular weight of the salt-responsive high-temperature drilling fluid viscosity enhancer is 1.0×10 7 ~3×10 7 .

[0055] The salt-responsive high-temperature resistant drilling fluid thickener of the present invention has four side chains at the same time. The first side chain has a hydrophilic group, which can increase the hydrophilicity of the thickener; the strongly adsorbable sulfonic acid group provided by the second side chain can improve the temperature and salt resistance of the thickener, so that the present invention has salt-responsive high-temperature resistant thickening properties; the amine salt group provided by the third side chain can be strongly adsorbed with the clay surface under electrostatic action; the fourth side chain is a hydrophobic chain, which can increase the hydrophobicity of the thickener; the weight average molecular weight of the present invention is 1.0×10 7 ~3×10 7 When the molecular weight is lower than this, the thickening effect of the thickener is not good, and when the molecular weight is higher than this, the dissolution effect of the thickener is not good.

[0056] The thickener of this invention is a polymer with a small number of hydrophobic groups attached to a hydrophilic macromolecular chain. In aqueous solution, when the thickener exceeds a certain concentration, interactions between the molecular chains cause hydrophobic association to form a reversible physical cross-linked network. This imparts unique rheological properties to the solution, including high viscosity enhancement, salt resistance, and shear resistance.

[0057] In some embodiments of the present invention, the amine salt is a quaternary ammonium salt.

[0058] In some embodiments of the present invention, the salt-responsive high-temperature resistant drilling fluid viscosifier has the structural formula:

[0059]

[0060] m:n:x:y:z=(4~5):(4~5):(3-5):(1-2):(0.2-0.4), R=C16~C18 alkyl.

[0061] In some embodiments of the present invention, the salt-responsive high-temperature resistant drilling fluid viscosifier is prepared from a terminal olefin hydrophilic monomer, a terminal olefin hydrophobic monomer, a terminal olefin ammonium salt, a terminal olefin sulfonic acid or a salt thereof by free radical micelle polymerization.

[0062] Preferably, the terminal olefinic hydrophilic monomer is R 1 is an amide group, a carboxylic acid or a carboxylate;

[0063] The terminal olefin sulfonic acid or its salt is b=5~10,R 2 , M is hydrogen or metal ion;

[0064] Terminal olefin ammonium salt is c = 5 to 10;

[0065] Terminal olefin hydrophobic monomers: R3 It is at least one of an amide group, an ester group, and an alcohol ester group.

[0066] In some embodiments of the present invention, the terminal olefin hydrophilic monomer is one or more of acrylamide, sodium acrylate, methacrylamide, and N,N-dimethylacrylamide; acrylamide contains an amide group, which easily forms hydrogen bonds with bentonite, thereby preventing the bentonite from settling.

[0067] The terminal olefin hydrophobic monomer is one or more of N-octadecyl acrylamide, hexadecyl methacrylate, and octadecyl methacrylate.

[0068] The terminal olefin ammonium salt is one or more of diallyldimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride, methacryloylpropyltrimethylammonium chloride, and dodecyldimethylallylammonium chloride. The terminal olefin sulfonic acid is one or more of 2-acrylamido-2-methyl-1-propanesulfonic acid, 2-acrylamidododecanesulfonic acid, sodium vinylsulfonate, sodium styrenesulfonate, and allylsulfonic acid. The sulfonic acid group has good temperature and salt resistance, improving the high temperature and salt resistance of the tackifier.

[0069] In some embodiments of the present invention, the molar ratio of the terminal alkenyl hydrophilic monomer, the terminal alkenyl hydrophobic monomer, the terminal alkenyl ammonium salt, and the terminal alkenyl sulfonic acid or its salt is (5-9):(0.2-0.4):(1-2):(3-5). When the molar ratio of the above monomers is within the above range, the salt-responsive high-temperature resistant drilling fluid viscosifier of the present invention can have good high-temperature stability and salt stability.

[0070] Preparation method:

[0071] The preparation method of the salt-responsive high-temperature resistant drilling fluid viscosifier provided by the present invention comprises a free radical micelle polymerization step, in which the following items are contacted in an aqueous solution: a terminal alkenyl hydrophilic monomer, a terminal alkenyl hydrophobic monomer, a terminal alkenyl ammonium salt, a terminal alkenyl sulfonic acid or its salt, an initiator, and a surfactant, wherein the molar ratio of the terminal alkenyl hydrophilic monomer, the terminal alkenyl hydrophobic monomer, the terminal alkenyl ammonium salt, and the terminal alkenyl sulfonic acid or its salt is (5-9): (0.2-0.4): (1-2): (3-5).

[0072] In some embodiments of the present invention, the free radical micelle polymerization step includes: preparing an aqueous solution of a terminal olefin sulfonic acid or a salt thereof and adjusting the pH to neutral; adding a terminal olefin hydrophilic monomer, a terminal olefin ammonium salt, a terminal olefin hydrophobic monomer and an anionic surfactant, mixing them evenly, adding an initiator, reacting under anaerobic conditions, and purifying to obtain a salt-responsive high-temperature resistant drilling fluid viscosifier.

[0073] Preferably, the terminal olefinic hydrophilic monomer is R1 is an amide group, a carboxylic acid or a carboxylate;

[0074] The terminal olefin sulfonic acid or its salt is b=5~10,R 2 , M is hydrogen or metal ion;

[0075] Terminal olefin ammonium salt is c = 5 to 10;

[0076] Terminal olefin hydrophobic monomers: R 3 It is at least one of an amide group, an ester group, and an alcohol ester group.

[0077] In some embodiments of the present invention, the terminal alkenyl hydrophilic monomer is one or more of acrylamide, sodium acrylate, methacrylamide, and N,N-dimethylacrylamide; the terminal alkenyl hydrophobic monomer is one or more of N-octadecyl acrylamide, hexadecyl methacrylate, and octadecyl methacrylate; the terminal alkenyl ammonium salt is one or more of diallyldimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride, methacryloylpropyltrimethylammonium chloride, and dodecyl / hexadecyldimethylallyl ammonium chloride; the terminal alkenyl sulfonic acid is one or more of 2-acrylamido-2-methyl-1-propanesulfonic acid, 2-acrylamidododecanesulfonic acid, sodium vinyl sulfonate, sodium styrenesulfonate, and allyl sulfonic acid.

[0078] In some embodiments of the present invention, the hydrophilic monomer consists of acrylamide and sodium acrylate. Preferably, the mass ratio of acrylamide to sodium acrylate is 1:1.

[0079] In some embodiments of the present invention, the hydrophobic monomer is N-octadecyl acrylamide or octadecyl methacrylate, preferably octadecyl methacrylate.

[0080] In some embodiments of the present invention, the temperature of the free radical micelle polymerization step is 40-65° C.; and the pH of the aqueous solution is 7-9.

[0081] In some embodiments of the present invention, the initiator is one or two of potassium persulfate / sodium bisulfite, azobisisobutyronitrile, ammonium persulfate / sodium bisulfite, and hydrogen peroxide / ferrous sulfate. Preferably, the initiator of the present invention is ammonium persulfate / sodium bisulfite.

[0082] In some embodiments of the present invention, the surfactant is one or both of a nonionic surfactant and an anionic surfactant. Preferably, the anionic surfactant is sodium lauryl sulfate.

[0083] application:

[0084] The application of the above-mentioned salt-responsive high-temperature resistant drilling fluid viscosity enhancer in the field of deep and ultra-deep drilling.

[0085] The application comprises preparing the salt-responsive high-temperature resistant tackifier into drilling fluid, wherein the drilling fluid comprises bentonite, the salt-responsive high-temperature resistant tackifier, sodium chloride, a fluid loss reducer and barite.

[0086] Example

[0087] The technical solution of the present invention is described in detail below by way of examples. If the manufacturer's brand or preparation method is not specified, the raw materials, equipment or solvents used are all common raw materials, equipment or solvents on the market. Unless otherwise specified, the raw materials of the same name used in the following examples and comparative examples are all the same raw materials. The synthetic polymer tackifier HE300 involved in the following examples was purchased from Chevron Phillips Chemical Co., Ltd. in the United States, the fluid loss agent F39, the fluid loss agent F40, the fluid loss agent F41, and the barite were purchased from the China Petroleum Engineering Technology Research Institute, the Huaian soil was purchased from Xinyuan Chemical (Bentonite) Co., Ltd. in Huaian County, Hebei Province, and the sodium chloride was purchased from Sinopharm Group.

[0088] Example 1

[0089] In this example, a salt-responsive high-temperature resistant zwitterionic polymer thickener A1 was prepared. The mass fractions of the raw materials used in the preparation were as follows:

[0090] Acrylamide / sodium acrylate (the mass ratio of acrylamide and sodium acrylate is 1:1) 6.06g, octadecyl methacrylate 1.2g, methacryloylpropyltrimethylammonium chloride 4.03g, 2-acrylamido-2-methyl-1-propanesulfonic acid sodium 8.99g, initiator ammonium persulfate / sodium bisulfite (the mass ratio of ammonium persulfate and sodium bisulfite is 1:1) 0.1g, anionic surfactant sodium lauryl sulfate 0.5g.

[0091] The specific preparation method is as follows:

[0092] 8.99 g of sodium 2-acrylamido-2-methyl-1-propanesulfonate was weighed and dissolved in 100 mL of pure water and completely dissolved using magnetic stirring to obtain a first solution. The first solution was then titrated with a 20% sodium hydroxide solution to a pH of 7 to obtain a second solution. 6.06 g of acrylamide / sodium acrylate, 4.03 g of methacryloylpropyltrimethylammonium chloride, 1.2 g of octadecyl methacrylate, and 0.5 g of anionic surfactant sodium lauryl sulfate were sequentially added to the second solution at 2-min intervals, and the mixture was thoroughly mixed by stirring to obtain a third solution.

[0093] The third solution was poured into a flask and purged with nitrogen for 30 minutes while stirring. 0.1 g of ammonium persulfate / sodium bisulfite was added to the solution. Under nitrogen, the water bath was heated to 50°C and stirred for 5 hours. After the reaction, the crude product was washed with acetone, filtered, purified three times, and dried under vacuum at 60°C for 24 hours to obtain viscosity enhancer A1.

[0094] Example 2

[0095] In this example, a salt-responsive high-temperature resistant zwitterionic polymer thickener A2 was prepared. The mass fractions of the raw materials used in the preparation were as follows:

[0096] Acrylamide / sodium acrylate (the mass ratio of acrylamide and sodium acrylate is 1:1) 7.07g, octadecyl methacrylate 1.2g, methacryloylpropyltrimethylammonium chloride 4.03g, 2-acrylamido-2-methyl-1-propanesulfonic acid sodium 8.99g, initiator ammonium persulfate / sodium bisulfite (the mass ratio of ammonium persulfate and sodium bisulfite is 1:1) 0.1g, anionic surfactant sodium lauryl sulfate 0.5g.

[0097] The specific preparation method is as follows:

[0098] 8.99 g of sodium 2-acrylamido-2-methyl-1-propanesulfonate was weighed and dissolved in 100 mL of pure water and completely dissolved using magnetic stirring to obtain a first solution. The first solution was then titrated with a 20% sodium hydroxide solution to a pH of 7 to obtain a second solution. 7.07 g of acrylamide / sodium acrylate, 4.03 g of methacryloylpropyltrimethylammonium chloride, 1.2 g of octadecyl methacrylate, and 0.5 g of anionic surfactant sodium lauryl sulfate were sequentially added to the second solution at 2-min intervals, and the mixture was thoroughly mixed by stirring to obtain a third solution.

[0099] The third solution was poured into a flask and purged with nitrogen for 30 minutes while stirring. 0.1 g of ammonium persulfate / sodium bisulfite was added to the solution. Under nitrogen, the water bath was heated to 50°C and stirred for 5 hours. After the reaction, the crude product was washed with acetone, filtered, purified three times, and dried under vacuum at 60°C for 24 hours to obtain viscosity enhancer A2.

[0100] Example 3

[0101] In this example, a salt-responsive high-temperature resistant zwitterionic polymer thickener A3 was prepared. The mass fractions of the raw materials used in the preparation were as follows:

[0102] Acrylamide / sodium acrylate (the mass ratio of acrylamide and sodium acrylate is 1:1) 8.08g, octadecyl methacrylate 1.2g, methacryloylpropyltrimethylammonium chloride 4.03g, 2-acrylamido-2-methyl-1-propanesulfonic acid sodium 10.01g, initiator ammonium persulfate / sodium bisulfite (the mass ratio of ammonium persulfate and sodium bisulfite is 1:1) 0.1g, anionic surfactant sodium lauryl sulfate 0.5g.

[0103] The specific preparation method is as follows:

[0104] 10.01 g of sodium 2-acrylamido-2-methyl-1-propanesulfonate was weighed and dissolved in 100 mL of pure water and completely dissolved using magnetic stirring to obtain a first solution. The first solution was then titrated with a 20% sodium hydroxide solution to a pH of 7 to obtain a second solution. 8.08 g of acrylamide / sodium acrylate, 4.03 g of methacryloylpropyltrimethylammonium chloride, 1.2 g of octadecyl methacrylate, and 0.5 g of anionic surfactant sodium lauryl sulfate were sequentially added to the second solution at 2-min intervals, and the mixture was thoroughly mixed by stirring to obtain a third solution.

[0105] The third solution was poured into a flask and purged with nitrogen for 30 minutes while stirring. 0.1 g of ammonium persulfate / sodium bisulfite was added to the solution. Under nitrogen, the water bath was heated to 50°C and stirred for 5 hours. After the reaction, the crude product was washed with acetone, filtered, purified three times, and dried under vacuum at 60°C for 24 hours to obtain viscosity enhancer A3.

[0106] Example 4

[0107] In this example, a salt-responsive high-temperature resistant zwitterionic polymer thickener A4 was prepared. The mass fractions of the raw materials used in the preparation were as follows:

[0108] Acrylamide / sodium acrylate (the mass ratio of acrylamide and sodium acrylate is 1:1) 7.08g, octadecyl methacrylate 1.2g, methacryloylpropyltrimethylammonium chloride 4.03g, 2-acrylamido-2-methyl-1-propanesulfonic acid sodium 7.08g, initiator ammonium persulfate / sodium bisulfite (the mass ratio of ammonium persulfate and sodium bisulfite is 1:1) 0.1g, anionic surfactant sodium lauryl sulfate 0.5g.

[0109] The specific preparation method is as follows:

[0110] 7.08 g of sodium 2-acrylamido-2-methyl-1-propanesulfonate was weighed and dissolved in 100 mL of pure water and completely dissolved by magnetic stirring to obtain a first solution. The first solution was then titrated with a 20% sodium hydroxide solution to a pH of 7 to obtain a second solution. 7.08 g of acrylamide / sodium acrylate, 4.03 g of methacryloylpropyltrimethylammonium chloride, 1.2 g of octadecyl methacrylate, and 0.5 g of anionic surfactant sodium lauryl sulfate were sequentially added to the second solution at 2-min intervals, and the mixture was thoroughly mixed by stirring to obtain a third solution.

[0111] The third solution was poured into a flask and purged with nitrogen for 30 minutes while stirring. 0.1 g of ammonium persulfate / sodium bisulfite was added to the solution. Under nitrogen, the water bath was heated to 50°C and stirred for 5 hours. After the reaction, the crude product was washed with acetone, filtered, purified three times, and dried under vacuum at 60°C for 24 hours to obtain viscosity enhancer A4.

[0112] Example 5

[0113] The only difference between this embodiment and embodiment 1 is that the amount of acrylamide / sodium acrylate (the mass ratio of acrylamide to sodium acrylate is 1:1) used in this embodiment is 9.09 g.

[0114] Example 6

[0115] The only difference between this example and Example 1 is that the amount of sodium 2-acrylamido-2-methyl-1-propanesulfonate used in this example is 10.02 g.

[0116] Example 7

[0117] The only difference between this embodiment and embodiment 1 is that the amount of methacryloylpropyltrimethylammonium chloride used in this embodiment is 5.05 g.

[0118] Example 8

[0119] The only difference between this embodiment and embodiment 1 is that in this embodiment, the first solution is titrated with a NaOH solution having a mass concentration of 20% to a pH of 8 to obtain a second solution.

[0120] Comparative Example 1

[0121] The only difference between this comparative example and Example 1 is that the amount of acrylamide / sodium acrylate (the mass ratio of acrylamide to sodium acrylate is 1:1) used in this comparative example is 3 g.

[0122] Comparative Example 2

[0123] The only difference between this comparative example and Example 1 is that the amount of sodium 2-acrylamido-2-methyl-1-propanesulfonate used in this comparative example is 5 g.

[0124] Comparative Example 3

[0125] The only difference between this comparative example and Example 1 is that the amount of methacryloylpropyltrimethylammonium chloride used in this comparative example is 2 g.

[0126] Comparative Example 4

[0127] The only difference between this comparative example and Example 1 is that the amount of octadecyl methacrylate used in this comparative example is 5 g.

[0128] Comparative Example 5

[0129] The only difference between this comparative example and Example 1 is that the pH value of the second solution in this comparative example is 5.

[0130] Table 1 Raw materials in various examples and comparative examples

[0131]

[0132]

[0133] The performance test of the above-synthesized tackifier was carried out:

[0134] (1) Comprehensive performance test of temperature and salt resistance

[0135] The thickeners prepared in Example 1 and Comparative Examples 1-5 were added to deionized water at a mass fraction of 1 wt.%, and the thickening effects were compared with the commonly used synthetic polymer thickener HE300. The specific data are shown in Table 2.

[0136] Table 2 Viscosity values ​​of aqueous solutions

[0137] sample <![CDATA[A1]]> HE300 <![CDATA[B1]]> <![CDATA[B2]]> <![CDATA[B3]]> <![CDATA[B4]]> <![CDATA[B5]]> Viscosity / mPa·s 900 480 7 8 6 5 4

[0138] As shown in Table 2 above, the thickener provided in Example 1 has good thickening performance in aqueous solution. This is because the thickener of the present invention forms a spatial network structure in the aqueous solution, which improves the thickening performance; on the contrary, Comparative Examples 1-3 failed to synthesize due to the reduction of the mass of the terminal alkenyl hydrophilic monomer, the terminal alkenyl sulfonic acid, and the terminal alkenyl ammonium salt. Comparative Example 4 increased the terminal alkenyl hydrophobic monomer, which caused the viscosity of the emulsion to increase during the reaction, resulting in a climbing phenomenon and the synthesis failed. Comparative Example 5 did not exhibit thickening performance due to the acidic reaction environment and the reverse reaction.

[0139] The viscosity enhancers prepared in Examples 1-8 were added to a saturated NaCl deionized water solution at a mass fraction of 1 wt.%, and aged at 120°C, 150°C, 180°C, and 200°C for 16 hours. The viscosity change was measured using a Brookfield DV-III ULTRA viscometer. The specific results are shown in Figure 2 .

[0140] Depend on Figure 2 It can be seen that the viscosity of the thickeners provided in Examples 1-8 remains at approximately 80% after high-temperature aging at 180°C, and remains above 60% after high-temperature aging at 200°C, demonstrating excellent temperature and salt resistance. This is because the second side chain can increase the hydrophobicity of the polymer, the quaternary ammonium salt group provided by the fourth side chain can strongly adsorb to the clay surface under electrostatic action, and the strongly adsorbable sulfonic acid group provided by the third side chain can improve the temperature and salt resistance of the polymer, thus enabling the present invention to possess salt-responsive high-temperature resistance and thickening properties.

[0141] (2) Tackifier performance test

[0142] (2.1) Effect of viscosifier on drilling fluid rheological parameters and filtration loss at room temperature and pressure

[0143] Preparation of base slurry: 16 g of bentonite was slowly added to 400 mL of distilled water while stirring, and then aged at room temperature for 24 h to prepare bentonite base slurry.

[0144] Drilling fluid sample preparation: 2 g of A1 was added to 400 mL of bentonite-based slurry and stirred at 5000 r / min for 20 min to obtain drilling fluid.

[0145] Performance test: The rheological parameters (apparent viscosity AV, plastic viscosity PV and dynamic shear force YP) and filtration loss at normal temperature and pressure of the prepared drilling fluid are tested according to the American Petroleum Institute (API) standard (API RP13B-1, 2009).

[0146] Drilling fluid aging treatment: The drilling fluid samples were subjected to aging treatment at a temperature of 180°C for 16 hours.

[0147] Performance test after aging: After cooling to room temperature after aging, the prepared drilling fluid was stirred at 5000 rpm for 30 minutes. The rheological parameters (apparent viscosity AV, plastic viscosity PV, and dynamic shear force YP) and normal temperature and pressure filtration of the prepared drilling fluid were tested according to the American Petroleum Institute (API) standard (API RP13B-1, 2009). The rheological and filtration loss test results before and after aging are shown in Table 3.

[0148] Table 3

[0149]

[0150] (2.2) Basic drilling fluid formula 1: 400 mL deionized water + 2% Huaian soil + 3% fluid loss reducer F39 + 2% fluid loss reducer F40 + 3% fluid loss reducer F41 + barite (density: 1.2 g / cm 3 ), the specific performance is shown in Table 4.

[0151] Table 4

[0152]

[0153] (2.3) Drilling fluid basic formula 2: 400 mL deionized water + 2% Huaian soil + 36% sodium chloride + 3% fluid loss reducer F39 + 2% fluid loss reducer F40 + 3% fluid loss reducer F41 + barite (density: 1.2 g / cm 3 ), the specific performance is shown in Table 5.

[0154] Table 5

[0155]

[0156] (2.4) Drilling fluid basic formula 3: 400 mL deionized water + 2% Huaian soil + 36% sodium chloride + 0.5% Al + 3% fluid loss reducer F39 + 2% fluid loss reducer F40 + 3% fluid loss reducer F41 + barite (density: 1.2 g / cm 3 ), the specific performance is shown in Table 6.

[0157] Table 6

[0158]

[0159] (2.5) The tackifiers prepared in Examples 1-8 and Comparative Examples 1-5 were added to the drilling fluid basic formula 2 at a mass fraction of 1 wt.%, respectively. High-temperature aging was performed at 120° C., 150° C., 180° C., and 200° C. for 16 hours. The test was performed in accordance with Part 1 of GB / T 16783.1-2014 "Field Testing of Drilling Fluids in the Petroleum and Natural Gas Industry." Specific performance is shown in Tables 7 to 10.

[0160] Table 7 Properties of saturated brine-based drilling fluids prepared with viscosifiers prepared in Examples 1-8 and Comparative Examples 1-5

[0161]

[0162] Table 8 Properties of saturated brine-based drilling fluids prepared with viscosifiers prepared in Examples 1-8 and Comparative Examples 1-5

[0163]

[0164] Table 9 Properties of saturated brine-based drilling fluids prepared with viscosifiers prepared in Examples 1-8 and Comparative Examples 1-5

[0165]

[0166]

[0167] Table 10 Properties of saturated brine-based drilling fluids prepared with viscosifiers prepared in Examples 1-8 and Comparative Examples 1-5

[0168]

[0169] Note: AV stands for apparent viscosity, PV stands for plastic viscosity, YP stands for dynamic shear force; FL HTHP Stands for high temperature and high pressure filtration loss.

[0170] It can be seen from Tables 7 to 10 that the thickeners provided in Examples 1 to 8 have a good thickening effect on saturated saltwater-based drilling fluids, and can also improve the filtration loss reduction effect to a certain extent, and have a system performance adjustment effect. On the contrary, the thickeners provided in Comparative Examples 1 to 5 have a poor thickening effect on saturated saltwater-based drilling fluids. This is because the long chains of the thickeners provided in Examples 1 to 8 are in saturated saltwater-based drilling fluids. Due to the addition of the electrolyte NaCl, the electrostatic adsorption effect between the positive and negative ion groups in the polymer molecules is shielded, and the thickener molecules establish an associative structure through the hydrophobic groups, the molecular chains gradually stretch, the fluid mechanics size increases, the solubility is enhanced, and the viscosity is large. At the same time, the amide group and the sulfonic acid group improve the temperature and salt resistance of the thickener of the present invention.

[0171] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments shown herein, but is intended to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A salt-responsive high-temperature resistant drilling fluid viscosifier, characterized by: The salt-responsive high-temperature resistant drilling fluid viscosity enhancer is a high molecular weight polymer with a weight-average molecular weight of 10,000,000 to 30,000,000, and a structural formula of: m:n:x:y:z=(4~5):(4~5):(3~5):(1~2):(0.2~0.4), R=C16~C18 alkyl.

2. A method for preparing a salt-responsive high-temperature resistant drilling fluid viscosifier, characterized in that: The invention comprises a free radical micelle polymerization step, in which the following items are contacted in an aqueous solution: a terminal alkenyl hydrophilic monomer, a terminal alkenyl hydrophobic monomer, a terminal alkenyl ammonium salt, a terminal alkenyl sulfonate, an initiator, and a surfactant, wherein the molar ratio of the terminal alkenyl hydrophilic monomer, the terminal alkenyl hydrophobic monomer, the terminal alkenyl ammonium salt, and the terminal alkenyl sulfonate is (5-9): (0.2-0.4): (1-2): (3-5); the terminal alkenyl hydrophilic monomer is acrylamide and sodium acrylate in a mass ratio of 1:1, the terminal alkenyl hydrophobic monomer is octadecyl methacrylate, the terminal alkenyl ammonium salt is methacryloylpropyltrimethylammonium chloride, and the terminal alkenyl sulfonate is sodium 2-acrylamido-2-methyl-1-propanesulfonate.

3. The method for preparing the salt-responsive high-temperature resistant drilling fluid viscosity enhancer according to claim 2, wherein: The free radical micelle polymerization steps include: preparing an aqueous solution of terminal olefin sulfonate and adjusting the pH to neutral; adding a terminal olefin hydrophilic monomer, a terminal olefin ammonium salt, a terminal olefin hydrophobic monomer and an anionic surfactant, mixing them evenly, adding an initiator, reacting under anaerobic conditions, and purifying to obtain a salt-responsive high-temperature resistant drilling fluid viscosifier.

4. The method for preparing the salt-responsive high-temperature resistant drilling fluid viscosity enhancer according to claim 2, wherein: The temperature of the free radical micelle polymerization step is 40~65℃.

5. The method for preparing the salt-responsive high-temperature resistant drilling fluid viscosity enhancer according to claim 2, wherein: The pH of the aqueous solution is 7~9.

6. Use of the salt-responsive high-temperature resistant drilling fluid viscosity enhancer according to claim 1 in the field of deep and ultra-deep drilling.

7. A drilling fluid, characterized in that: The invention comprises the salt-responsive high-temperature resistant viscosity increasing agent according to claim 1.

8. The drilling fluid according to claim 7, characterized in that: The drilling fluid comprises bentonite, the salt-responsive high-temperature resistant viscosity enhancer according to claim 1, sodium chloride, a fluid loss reducer and barite.

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