A high-temperature and high-salt resistant crosslinked viscosifier and filtrate reducer for soil-free water-based drilling fluid, its preparation method and application

Abstract

The present invention provides a temperature and salt resistant crosslinking thickening and filtrate loss reducing agent for soil-free water-based drilling fluids, its preparation method and application, belonging to the field of drilling technology. The temperature and salt resistant crosslinking thickening and filtrate loss reducing agent for soil-free water-based drilling fluids comprises the following raw materials in parts by weight: 15-25 parts of N,N-dimethylacrylamide, 1-10 parts of 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate, 1-10 parts of long-chain alkyl polyoxyethylene ether methacrylate, 0.005-0.015 parts of macromolecular crosslinking agent, 0.03-0.08 parts of initiator A, and 80-100 parts of deionized water. The thickening and filtrate loss reducing agent of the present invention has a temperature resistance of up to 180 °C and is resistant to saturated NaCl, and has excellent thickening, shear strengthening and filtrate loss reducing effects under high temperature and high salt conditions, improves the rheological and filtrate loss properties of the drilling fluid, and ensures safe and efficient drilling of deep wells.

Description

Technical Field

[0001] The present invention relates to a temperature and salt resistant crosslinking thickening and filtration loss reducing agent for soil-free water-based drilling fluids, its preparation method and application, and belongs to the field of drilling technology. Background Art

[0002] With the increase of drilling depth, the drilling risks and difficulties increase step by step. Especially under the conditions of high temperature (180°C) and high salt (>15% NaCl), the dehydration of bentonite and the thermal degradation and desorption of filtration loss reducing agents will lead to the deterioration of the rheological and filtration properties of water-based drilling fluids, and downhole complex accidents such as wellbore collapse, pipe sticking, and overflow occur frequently. In severe cases, it may even lead to the abandonment of the wellbore. The soil-free water-based drilling fluid is a drilling fluid without clay materials such as bentonite. Compared with the clay-containing water-based drilling fluid, it has the characteristics of high mechanical drilling rate, good lubricity, good cuttings carrying capacity, good reservoir protection performance, and excellent salt resistance, and has broad application prospects. However, the soil-free drilling fluid does not contain bentonite, and it is impossible to rely on the network structure formed by bentonite and polymer to endow the drilling fluid with the rheological properties required for drilling. Especially under the harsh conditions of high temperature, high salt, and high density, the treatment agent needs to have excellent temperature and salt resistance to play a good role in thickening and increasing shear force.

[0003] At present, patent literature has reported more on two types of tackifiers, namely natural modified polymers and synthetic polymers. Chinese patent literature CN109796946A provides a hydroxyethyl psyllium husk-nano silica composite tackifier. When the dosage of the tackifier is 0.5%, the apparent viscosity of the system is 22.0 mPa·s, which is higher than 18.0 mPa·s of the 5% bentonite base slurry. When the dosage of the tackifier is 1%, the viscosity reduction rate of the system after aging at 150°C for 16 h is lower than 30%. Chinese patent literature CN102127401A discloses a high-temperature resistant tackifier composed of starch, guar gum, alkaline hydroxide, epoxide and alcohol solvent. This tackifier can resist temperatures up to 150°C in fresh water, 130°C in seawater and 120°C in brine. Chinese patent literature CN106608945A discloses a copolymer association tackifier mainly composed of N,N-dimethylacrylamide, N-methyldiallylpropylsulfonate and cationic polyamine association body. This tackifier can withstand temperatures up to 180°C, resist saturated NaCl concentration and 20% CaCl2 concentration, and has good tackifying, inhibition and filtration loss reduction properties in 4% calcium bentonite base slurry. Chinese patent literature CN104140790A discloses a polymer tackifier and its preparation method. This polymer tackifier is prepared from polyvinyl alcohol and xanthan gum. After adding 2% of the tackifier to 15% calcium chloride aqueous solution, the apparent viscosity of the drilling fluid after aging at 120°C for 16 h is 22 mPa·s. Chinese patent literature CN101845295A discloses a drilling fluid tackifier composed of a quaternary copolymer and a bisquaternary ammonium salt. This tackifier forms earthworm-like or long rod-like micelles through molecular association in water, thus effectively increasing the viscosity of the drilling fluid. When the dosage of the tackifier is 1.5%, the apparent viscosity of the solids-free drilling fluid after aging at 100°C for 16 h is 36 mPa·s, the plastic viscosity is 17 mPa·s and the shear force is 19 Pa. Chinese patent literature CN100549123C discloses a tackifier composed of a sulfonate-type anionic surfactant, a quaternary ammonium salt-type or pyridinium salt-type cationic surfactant, industrial formaldehyde and industrial alcohol. When 3% of the tackifier is added to 1% hydroxyethyl cellulose saturated salt solution, the viscosity of the solution after aging at 150°C increases from 3 mPa·s to 26 mPa·s. When 3% of the tackifier is added to 0.5% HPAM aqueous solution, the viscosity of the solution after aging at 150°C increases from 3 mPa·s to 20 mPa·s. Chinese patent literature CN104650827A discloses a solids-free drilling fluid tackifier polymerized from N,N-dimethylacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinylcaprolactam and divinylbenzene as monomers, which can resist temperatures up to 165°C. CN107235863A discloses a hydrophobic associating polymer polymerized from a benzene ring-containing hydrophobic monomer and N-vinylpyrrolidone, which can resist temperatures up to 150°C.CN107235862A discloses a polymer viscosifier for solids-free drilling fluid, with a temperature resistance up to 150 °C. Hydrophobic groups of benzene ring and long fluorocarbon chains are introduced into the viscosifier molecules, which can form a three-dimensional network structure through hydrophobic association, thus effectively increasing the solution viscosity.

[0004] Although there are various existing viscosifiers, their temperature and salt resistance are insufficient and cannot meet the performance requirements of high temperature (180 °C) and high salt (> 15% NaCl). Therefore, it is urgent to develop an efficient viscosifier and filtration reducer to effectively maintain the rheological properties of solids-free drilling fluid under high temperature and high salt conditions. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, especially the poor temperature and salt resistance of the viscosifiers for solids-free water-based drilling fluid, which cannot maintain the rheological properties of solids-free water-based drilling fluid under high temperature and high salt conditions, the present invention provides a temperature and salt resistant crosslinked viscosifier and filtration reducer for solids-free water-based drilling fluid, its preparation method and application. The viscosifier and filtration reducer of the present invention has the effects of viscosity increasing, gel strength increasing and filtration reduction under high temperature and high salt conditions, and can improve the rheological and filtration properties of solids-free water-based drilling fluid under high temperature and high salt conditions.

[0006] The present invention is realized by the following technical solutions:

[0007] A temperature and salt resistant crosslinked viscosifier and filtration reducer for solids-free water-based drilling fluid, comprising the following raw materials in parts by weight: 15-25 parts of N,N-dimethylacrylamide, 1-10 parts of 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate, 1-10 parts of long-chain alkyl polyoxyethylene ether methacrylate, 0.005-0.015 parts of macromolecular crosslinking agent, 0.03-0.08 parts of initiator A, and 80-100 parts of deionized water.

[0008] According to the present invention, the 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate can be commercially available or prepared according to the following method:

[0009] Dissolve N-[3-(dimethylamino)propyl]methacrylamide in acetonitrile to obtain solution 1, dissolve 1,3-propanesultone in acetonitrile to obtain solution 2, dropwise add solution 1 into solution 2, and after the dropping is completed, carry out the reaction; after the reaction is completed, cool, remove the solvent, and dry to obtain 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate;

[0010] Further preferably, in Solution 1, the mass ratio of N-[3-(dimethylamino)propyl]methacrylamide to acetonitrile is 1:3 - 15, and in Solution 2, the mass ratio of 1,3-propane sultone to acetonitrile is 1:2.5 - 12; the molar ratio of N-[3-(dimethylamino)propyl]methacrylamide to 1,3-propane sultone is 1:1.2 - 3; the dropping rate of Solution 1 is 3 - 8 mL / min.

[0011] Further preferably, in the preparation of 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate, the reaction temperature is 70 - 90 °C, and the reaction time is 20 - 30 h; the drying is carried out under vacuum at 80 - 100 °C for 20 - 30 h.

[0012] According to the present invention, the reaction route for synthesizing 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate is as follows:

[0013]

[0014] Preferably according to the present invention, the structural formula of the long-chain alkyl polyoxyethylene ether methacrylate is shown in Formula I below:

[0015] Formula I;

[0016] In Formula I, n is an integer between 20 and 30, and R is a straight-chain hydrocarbon group with 16 - 25 carbon atoms.

[0017] Preferably according to the present invention, the macromolecular crosslinking agent is prepared by the following method:

[0018] (1) Add 2-acrylamido-2-methylpropanesulfonic acid and initiator B to deionized water, stir evenly to obtain an aqueous phase;

[0019] (2) Mix pentaerythritol triallyl ether, triallyl isocyanurate and cyclohexane, and then add an emulsifier, stir evenly to obtain an oil phase;

[0020] (3) Under stirring conditions, add the aqueous phase to the oil phase, and then subject the obtained mixed system to shear emulsification to obtain a water-in-oil emulsion; transfer it to a three-necked flask for reaction; after the reaction is completed, wash and dry to obtain the macromolecular crosslinking agent.

[0021] Preferably according to the present invention, in step (1), the initiator B is 2,2'-azobis(2-methylpropionamidine) dihydrochloride, azobisisobutyronitrile, ammonium persulfate or potassium persulfate, and the mass ratio of the initiator B to 2-acrylamido-2-methylpropanesulfonic acid is 0.01 - 0.1:10.

[0022] Preferably according to the present invention, the mass ratio of 2-acrylamido-2-methylpropanesulfonic acid to deionized water in step (1) is 1:2.5 - 7.

[0023] Preferably according to the present invention, the mass ratio of pentaerythritol triallyl ether, triallyl isocyanurate and 2-acrylamido-2-methylpropanesulfonic acid in step (2) is 0.05 - 0.10:0.05 - 0.10:5 - 10.

[0024] Preferably according to the present invention, the emulsifier in step (2) is a composition of Span 80 and Tween 80, the mass ratio of Tween 80 to Span 80 in the composition is 1 - 3:2 - 6, and the mass ratio of the emulsifier to cyclohexane is 1:7 - 15.

[0025] Preferably according to the present invention, the rotation speed of stirring in step (3) is 500 - 1500 rpm, and the mass ratio of deionized water in the aqueous phase to cyclohexane in the oil phase is 20 - 50:60 - 80.

[0026] Preferably according to the present invention, the rotation speed of shear emulsification in step (3) is 5000 - 10000 rpm, and the time of shear emulsification is 10 - 30 min.

[0027] Preferably according to the present invention, the temperature of the reaction in step (3) is 50 - 70 °C, and the time of the reaction is 3 - 5 h.

[0028] Preferably according to the present invention, the washing in step (3) is soaking and washing 3 - 5 times in ethanol, and the drying is vacuum drying at 80 - 100 °C for 20 - 30 h.

[0029] Preferably according to the present invention, the initiator A is azodiisobutyramidine dihydrochloride, azodiisobutyronitrile, ammonium persulfate or potassium persulfate.

[0030] According to the present invention, the preparation method of the high-temperature and high-salt-resistant crosslinked thickening and filtration loss reducing agent for soil-free water-based drilling fluid includes the following steps:

[0031] Add N,N-dimethylacrylamide, 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate, long-chain alkyl polyoxyethylene ether methacrylate and macromolecular crosslinking agent into deionized water, stir evenly to obtain a mixed solution; heat the mixed solution to the reaction temperature, add initiator A for reaction; after the reaction is completed, through washing, drying and pulverization, obtain the high-temperature and high-salt-resistant crosslinked thickening and filtration loss reducing agent for soil-free water-based drilling fluid.

[0032] Preferably according to the present invention, the reaction temperature is 60 - 80 °C, and the reaction time is 3 - 5 h; the washing is carried out by washing 2 - 3 times with acetone and then 1 - 2 times with absolute ethanol; the drying is carried out by vacuum drying at 80 - 100 °C until constant weight.

[0033] According to the present invention, the application of the high-temperature and high-salt resistant crosslinked thickening and filtration loss reducing agent for soil-free water-based drilling fluid in the soil-free water-based drilling fluid, the concentration of the high-temperature and high-salt resistant crosslinked thickening and filtration loss reducing agent for soil-free water-based drilling fluid in the soil-free water-based drilling fluid is 1 - 2 wt%.

[0034] The technical features and beneficial effects of the present invention are as follows:

[0035] 1. The macromolecular crosslinking agent of the present invention is prepared by free radical polymerization of 2-acrylamido-2-methylpropanesulfonic acid, pentaerythritol triallyl ether, and triallyl isocyanurate. The internal structure of the macromolecular crosslinking agent is a three-dimensional crosslinked network structure, which has stronger temperature resistance compared with conventional vinyl crosslinking agents. The macromolecular crosslinking agent with strong temperature resistance and heat resistance crosslinks linear polymers to form a two-dimensional network structure, enabling the thickening and filtration loss reducing agent to have excellent high-temperature hydrolysis stability, thereby exerting excellent thickening, gel strength increasing, and filtration loss reducing effects under high-temperature and high-salt conditions.

[0036] 2. The copolymer of the thickening and filtration loss reducing agent of the present invention contains zwitterionic side chains, thus having an anti-polyelectrolyte effect. As the salt concentration increases, the copolymer molecular chains gradually stretch, and the hydrodynamic radius increases, enabling the copolymers to form a spatial network structure through intermolecular forces such as hydrogen bonds and electrostatic forces. The long-chain alkyl groups endow the copolymer with hydrophobic association characteristics, and the copolymer can form an associative network through hydrophobic interactions under high-salt conditions, further strengthening the internal spatial network structure of the drilling fluid and enhancing the thickening, gel strength increasing, and filtration loss reducing properties of the copolymer. The synergistic effect of the micro-crosslinked structure, anti-polyelectrolyte, and hydrophobic association enables the thickening and filtration loss reducing agent of the present invention to have excellent high-temperature and high-salt resistance.

[0037] 3. The thickening and filtration loss reducing agent for soil-free water-based drilling fluid of the present invention has a high temperature resistance of up to 180 °C and a high salt resistance to saturation. It can effectively maintain the viscosity and gel strength of the soil-free water-based drilling fluid and reduce the filtration loss under high-temperature and high-salt conditions, playing a role in improving the rheology and filtration properties of the drilling fluid. It is applicable to soil-free drilling fluids of fresh water, sea water, brine, and saturated brine, and the recommended dosage is 1 - 2%. Specific Embodiments

[0038] The present invention will be further described below in conjunction with specific embodiments, so that those skilled in the art can better understand the present invention and implement it, but the examples given are not intended to limit the present invention. The materials used in the examples can be obtained from commercial channels without special instructions.

[0039] In the present invention, the "parts" mentioned are all parts by weight.

[0040] Preparation Example 1

[0041] Preparation of 3-[(3-Methacrylamidopropyl)dimethylammonio]propane-1-sulfonate

[0042] Dissolve 9.38 g of N-[3-(dimethylamino)propyl]methacrylamide in 50 g of acetonitrile to obtain Solution 1; dissolve 10.99 g of 1,3-propane sultone in 50 g of acetonitrile to obtain Solution 2. Slowly add Solution 1 dropwise into Solution 2 at a rate of 5 mL / min using a constant pressure funnel. After the addition is complete, heat the resulting mixture to 80 °C and continue to react for 24 h at a stirring rate of 300 rpm. After the reaction is completed, cool it naturally to room temperature. Rotate evaporate to remove acetonitrile at 90 °C, and finally vacuum dry at 90 °C for 24 h. The obtained white powder is 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate.

[0043] Preparation Example 2

[0044] Preparation of macromolecular crosslinking agent

[0045] Weigh 33 g of deionized water in a beaker, add 10 g of 2-acrylamido-2-methylpropanesulfonic acid and 0.08 g of 2,2'-azobis(2-methylpropionamidine) dihydrochloride (V50) to the deionized water, and stir well for 20 minutes to obtain an aqueous phase; then add 0.05 g of pentaerythritol triallyl ether, 0.05 g of triallyl isocyanurate and 66 g of cyclohexane to the beaker, and then add 3.5 g of Span 80 and 3.5 g of Tween 80, and stir well for 20 minutes to obtain an oil phase; at a stirring rate of 1000 rpm, add the aqueous phase to the oil phase. When the aqueous phase is completely added to the oil phase, shear emulsify the resulting mixed system at a rate of 8000 rpm on an emulsifier for 20 minutes to obtain a water-in-oil emulsion; transfer it to a three-necked flask, heat it to 60 °C, and continue to react for 4 h under a stirring rate of 350 rpm and a nitrogen atmosphere. Wash the reaction product 3 times with absolute ethanol, and vacuum dry the precipitate at 90 °C for 24 h to obtain the macromolecular crosslinking agent.

[0046] The 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate and macromolecular crosslinking agent used in the examples and comparative examples were prepared from Comparative Example 1 and Comparative Example 2 respectively.

[0047] Example 1

[0048] An anti-temperature and anti-salt crosslinking thickening and filtration loss reducing agent for soil-free water-based drilling fluid, comprising the following raw materials in parts by weight: 20 parts of N,N-dimethylacrylamide, 5 parts of 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate, 5 parts of long-chain alkyl polyoxyethylene ether methacrylate, 0.005 part of macromolecular crosslinking agent, 0.03 part of initiator A, and 80 parts of deionized water;

[0049] Among them, the structural formula of the long-chain alkyl polyoxyethylene ether methacrylate is shown in Formula I as follows:

[0050] Formula I;

[0051] In Formula I, n is 20, and R is a straight-chain hydrocarbon group with 22 carbon atoms;

[0052] The initiator A is azodiisobutylamidine dihydrochloride.

[0053] The preparation method of the above-mentioned anti-temperature and anti-salt crosslinking thickening and filtration loss reducing agent for soil-free water-based drilling fluid comprises the following steps:

[0054] Add deionized water into a three-necked flask, add N,N-dimethylacrylamide, 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate, long-chain alkyl polyoxyethylene ether methacrylate and macromolecular crosslinking agent into the deionized water, and stir well for 20 minutes to disperse the monomers evenly to obtain a mixed solution; heat the mixed solution to 70 °C, add initiator A to initiate free radical polymerization, and continuously react for 4 h to obtain a transparent gel; wash the gel twice with acetone, then wash it once with absolute ethanol, and then place the gel in a vacuum dryer at 90 °C until constant weight, and crush it to obtain the anti-temperature and anti-salt crosslinking thickening and filtration loss reducing agent A1 for soil-free water-based drilling fluid.

[0055] Example 2

[0056] An anti-temperature and anti-salt crosslinking thickening and filtration loss reducing agent for soil-free water-based drilling fluid, comprising the following raw materials in parts by weight: 20 parts of N,N-dimethylacrylamide, 5 parts of 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate, 5 parts of long-chain alkyl polyoxyethylene ether methacrylate, 0.01 part of macromolecular crosslinking agent, 0.03 part of initiator A, and 80 parts of deionized water; the selection of other raw materials is as described in Example 1.

[0057] The preparation method of the above-mentioned anti-temperature and anti-salt crosslinking thickening and filtration loss reducing agent for soil-free water-based drilling fluid is as described in Example 1 to obtain the anti-temperature and anti-salt crosslinking thickening and filtration loss reducing agent A2 for soil-free water-based drilling fluid.

[0058] Example 3

[0059] A temperature- and salt-resistant crosslinked thickening and filtration loss reducing agent for soil-free water-based drilling fluids, comprising the following raw materials in parts by weight: 20 parts of N,N-dimethylacrylamide, 5 parts of 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate, 5 parts of long-chain alkyl polyoxyethylene ether methacrylate, 0.015 parts of macromolecular crosslinking agent, 0.03 parts of initiator A, and 80 parts of deionized water; the selection of other raw materials is as described in Example 1.

[0060] The preparation method of the above temperature- and salt-resistant crosslinked thickening and filtration loss reducing agent for soil-free water-based drilling fluids is as described in Example 1, and a temperature- and salt-resistant crosslinked thickening and filtration loss reducing agent A3 for soil-free water-based drilling fluids is obtained.

[0061] Example 4

[0062] A temperature- and salt-resistant crosslinked thickening and filtration loss reducing agent for soil-free water-based drilling fluids, comprising the following raw materials in parts by weight: 25 parts of N,N-dimethylacrylamide, 5 parts of 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate, 5 parts of long-chain alkyl polyoxyethylene ether methacrylate, 0.005 parts of macromolecular crosslinking agent, 0.03 parts of initiator A, and 80 parts of deionized water; the selection of other raw materials is as described in Example 1.

[0063] The preparation method of the above temperature- and salt-resistant crosslinked thickening and filtration loss reducing agent for soil-free water-based drilling fluids is as described in Example 1, and a temperature- and salt-resistant crosslinked thickening and filtration loss reducing agent A4 for soil-free water-based drilling fluids is obtained.

[0064] Example 5

[0065] A temperature- and salt-resistant crosslinked thickening and filtration loss reducing agent for soil-free water-based drilling fluids, comprising the following raw materials in parts by weight: 20 parts of N,N-dimethylacrylamide, 10 parts of 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate, 5 parts of long-chain alkyl polyoxyethylene ether methacrylate, 0.005 parts of macromolecular crosslinking agent, 0.03 parts of initiator A, and 80 parts of deionized water; the selection of other raw materials is as described in Example 1.

[0066] The preparation method of the above temperature- and salt-resistant crosslinked thickening and filtration loss reducing agent for soil-free water-based drilling fluids is as described in Example 1, and a temperature- and salt-resistant crosslinked thickening and filtration loss reducing agent A5 for soil-free water-based drilling fluids is obtained.

[0067] Example 6

[0068] A temperature and salt resistant crosslinking thickening and filtration reducing agent for soil-free water-based drilling fluid, comprising the following raw materials in parts by weight: 20 parts of N,N-dimethylacrylamide, 5 parts of 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate, 10 parts of long-chain alkyl polyoxyethylene ether methacrylate, 0.005 part of macromolecular crosslinking agent, 0.03 part of initiator A, and 80 parts of deionized water; the selection of other raw materials is as described in Example 1.

[0069] The preparation method of the above temperature and salt resistant crosslinking thickening and filtration reducing agent for soil-free water-based drilling fluid is as described in Example 1, and a temperature and salt resistant crosslinking thickening and filtration reducing agent A6 for soil-free water-based drilling fluid is obtained.

[0070] Comparative Example 1

[0071] A thickening and filtration reducing agent for soil-free water-based drilling fluid is as described in Example 1, except that: the macromolecular crosslinking agent is 0.02 part.

[0072] The preparation method of the above thickening and filtration reducing agent for soil-free water-based drilling fluid is as described in Example 1, and a thickening and filtration reducing agent D1 for soil-free water-based drilling fluid is obtained.

[0073] Comparative Example 2

[0074] A thickening and filtration reducing agent for soil-free water-based drilling fluid is as described in Example 1, except that: the macromolecular crosslinking agent is not added.

[0075] The preparation method of the above thickening and filtration reducing agent for soil-free water-based drilling fluid is as described in Example 1, except that: the step of adding the macromolecular crosslinking agent is omitted, and a thickening and filtration reducing agent D2 for soil-free water-based drilling fluid is obtained.

[0076] Comparative Example 3

[0077] A thickening and filtration reducing agent for soil-free water-based drilling fluid is as described in Example 1, except that: 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate is not added.

[0078] The preparation method of the above thickening and filtration reducing agent for soil-free water-based drilling fluid is as described in Example 1, except that: the step of adding 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate is omitted, and a thickening and filtration reducing agent D3 for soil-free water-based drilling fluid is obtained.

[0079] Comparative Example 4

[0080] A thickening and filtration reducing agent for soil-free water-based drilling fluid is as described in Example 1, except that: long-chain alkyl polyoxyethylene ether methacrylate is not added.

[0081] The preparation method of the above-mentioned tackifier and filtration reducer for soil-free water-based drilling fluid is as described in Example 1, except that the step of adding long-chain alkyl polyoxyethylene ether methacrylate is omitted, and the tackifier and filtration reducer D4 for soil-free water-based drilling fluid is obtained.

[0082] Comparative Example 5

[0083] A tackifier and filtration reducer for soil-free water-based drilling fluid is as described in Example 1, except that the macromolecular cross-linking agent is replaced with an equal mass of N,N-dimethylenebisacrylamide.

[0084] The preparation method of the above-mentioned tackifier and filtration reducer for soil-free water-based drilling fluid is as described in Example 1, and the tackifier and filtration reducer D5 for soil-free water-based drilling fluid is obtained.

[0085] Comparative Example 6

[0086] A tackifier and filtration reducer for soil-free water-based drilling fluid is as described in Example 1, except that the long-chain alkyl polyoxyethylene ether methacrylate is replaced with an equal mass of methyl methacrylate.

[0087] The preparation method of the above-mentioned tackifier and filtration reducer for soil-free water-based drilling fluid is as described in Example 1, and the tackifier and filtration reducer D6 for soil-free water-based drilling fluid is obtained.

[0088] Application Experimental Example 1

[0089] Add 8 parts by weight of the tackifier and filtration reducers A1 - A6 in the examples to 400 parts by weight of deionized water, stir at a high speed of 6000 rpm for 20 min, then add 144 parts by weight of NaCl, and continue stirring for 20 min to obtain drilling fluids F1 - F6. According to the same method, configure the tackifier and filtration reducers D1 - D6 in the comparative examples into drilling fluids DF1 - DF6. Load the drilling fluids into a stainless steel aging tank and keep rolling at a constant temperature of 180 °C for 16 hours. After aging, cool to room temperature and take out, and stir at 6000 rpm for 20 min. According to the petroleum and natural gas industry standard GB / T 29170 - 2012 "Petroleum and natural gas industry - Laboratory testing of drilling fluids", measure the apparent viscosity (AV, mPa·s), plastic viscosity (PV, mPa·s), yield point (YP, Pa), and API filtration loss FL of the drilling fluids before and after high-temperature aging. API The results are shown in Table 1.

[0090] Table 1 Drilling fluid performance test

[0091]

[0092] As shown in Table 1 of the experimental results, when the dosage of the viscosifier and filtration reducer in the saturated brine drilling fluid is 2%, the AV of drilling fluids F1 - F6 remains within the range of 46.5 mPa·s to 57.0 mPa·s, and the AV after aging at 180°C remains within the range of 25.0 mPa·s to 38.5 mPa·s. The retention rates of AV before and after aging are 53.76%, 62.37%, 67.54%, 56.25%, 59.18%, and 58.76% respectively. The PV of drilling fluids F1 - F6 before aging remains within the range of 39.5 mPa·s to 45.0 mPa·s, and the PV after aging at 180°C remains within the range of 21.0 mPa·s to 29.0 mPa·s. The retention rates of PV before and after aging are 53.16%, 61.73%, 64.44%, 53.75%, 56.79%, and 55.56% respectively. The YP of drilling fluids F1 - F6 before aging remains within the range of 7.0 mPa·s to 12.0 mPa·s, and the YP after aging at 180°C remains within the range of 4.0 Pa to 9.5 Pa. The retention rates of YP before and after aging are 57.14%, 65%, 79.17%, 68.75%, 70.59%, and 75.0% respectively. The retention rates of AV, PV, and YP of drilling fluids F1 - F6 before and after aging are all greater than 50%, indicating that the viscosifier and filtration reducer of the present invention have good temperature resistance, salt resistance, viscosity increasing, and gel strength enhancing properties. With the increase in the dosage of the crosslinking agent, the AV, PV, and YP of the drilling fluid before and after aging at 180°C show an upward trend, indicating that the macromolecular crosslinking agent effectively enhances the temperature resistance of the viscosifier and filtration reducer. When the dosages of N,N - dimethylacrylamide, 3 - [(3 - methacrylamidopropyl)dimethylammonio]propane - 1 - sulfonate, and long - chain alkyl polyoxyethylene ether methacrylate are increased, the viscosity increasing, gel strength enhancing, and filtration reducing properties of the copolymer are improved. Because the dimethyl, sulfonic acid group, and long alkyl chain have rigidity and high temperature hydrolysis resistance, effectively improving the temperature resistance of the polymer. The FL of drilling fluids F1 - F6 after aging at 180°C API are 16.0, 14.8, 12.6, 15.8, 15.0, and 15.4 mL respectively, indicating that the viscosifier and filtration reducer of the present invention also has good filtration reducing properties.

[0093] As can be seen from Comparative Example 1, when the dosage of the crosslinking agent is further increased, the viscosity increasing and gel strength enhancing effects of the viscosifier and filtration reducer before aging are poor. Because too much crosslinking agent will cause the polymer to form a three-dimensional structure, namely a water-insoluble microgel. The three-dimensional crosslinked structure of the microgel degrades in a high-temperature environment, promoting the dissolution of the polymer. Therefore, the drilling fluid after aging can still maintain a certain viscosity, gel strength and a low filtration loss. As can be seen from Comparative Examples 2 and 5, when the anti-macromolecular crosslinking agent is removed, or the macromolecular crosslinking agent is replaced with a conventional vinyl crosslinking agent N,N-methylenebisacrylamide, the high-temperature resistance of the viscosifier and filtration reducer is greatly reduced. After aging at 180°C, the viscosity and gel strength of the drilling fluid are low, and the filtration loss is large. As can be seen from Comparative Example 3, when 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate is removed, the viscosifier and filtration reducer do not have the effect of anti-polyelectrolyte and have poor salt resistance. After aging at 180°C, the viscosity and gel strength of the drilling fluid are also low, and the filtration loss is large. As can be seen from Comparative Examples 4 and 6, when the hydrophobic monomer long-chain alkyl polyoxyethylene ether methacrylate is removed, or it is replaced with methyl methacrylate without a long-chain alkyl group, the hydrophobic association of the viscosifier and filtration reducer is weak, so the performance of the treatment agent decreases. The synergistic effect of the micro-crosslinked structure, anti-polyelectrolyte effect and hydrophobic association enables the viscosifier and filtration reducer of the present invention to achieve excellent viscosity increasing, gel strength enhancing and filtration loss reducing effects under high-temperature and high-salt conditions.

[0094] Application Experimental Example 2

[0095] At a stirring rate of 6000 rpm, 400 parts by weight of deionized water was taken, and 4 parts by weight of the viscosifier and filtration reducer A3 in Example 3, 20 parts by weight of ultra-fine calcium carbonate (200 μm), and 144 parts by weight of sodium chloride were successively added to the deionized water. Then barite was added respectively to prepare non-soil-based water-based drilling fluids with densities of 1.2, 1.4, 1.6, 1.8, and 2.0 g / cm 3 , denoted as F7, F8, F9, F10, and F11. The drilling fluid without the viscosifier and filtration reducer A3 was denoted as DF7, DF8, DF9, DF10, and DF11. The above drilling fluids were filled into a stainless steel aging tank and kept rolling at a constant temperature of 180°C for 16 hours. The apparent viscosity (AV, mPa·s), plastic viscosity (PV, mPa·s), yield point (YP, Pa), API filtration loss FL API and high-temperature and high-pressure filtration loss FL HTHP (180°C, 3.5 MPa) of the drilling fluid before and after aging were measured. The results are shown in Tables 2 and 3.

[0096] Table 2 Performance Test of Drilling Fluid Containing the Viscosifier and Filtration Reducer of the Present Invention

[0097]

[0098] Table 3 Performance Test of Drilling Fluid without the Viscosifier and Filtration Reducer of the Present Invention

[0099]

[0100] As can be seen from Table 2 and Table 3, when the density of the drilling fluid is in the range of 1.2 - 2.0 g / cm 3 the rheological parameters are within a reasonable range before and after aging at 180°C. The drilling fluid can maintain a certain viscosity and shear force at low density, and its viscosity and shear force will not be too high at high density. From the filtration performance of the drilling fluid, when the viscosity increasing and filtration loss reducing agent is not added, the FL API of the drilling fluid is complete filtration loss. After adding 1% of the viscosity increasing and filtration loss reducing agent, the FL API of the drilling fluid before and after aging at 180°C is less than 10 mL, and the FL HTHP also decreases to a certain extent. The viscosity increasing and filtration loss reducing agent has soft polymer long chains and a cross-linked network structure, which can block the water loss pores and cracks inside the mud cake and effectively reduce the filtration loss. The experimental results show that the viscosity increasing and filtration loss reducing agent of the present invention has good viscosity increasing, shear force increasing and filtration loss reducing effects in the soil-free saturated salt drilling fluid. During the drilling process, the viscosity increasing and filtration loss reducing agent can effectively improve and maintain the rheological and filtration performance of the soil-free drilling fluid and improve the safety of drilling.

[0101] Application Experimental Example 3

[0102] 8 parts by weight of the viscosity increasing and filtration loss reducing agents A3, HE300, 80A51, Driscal D and Dristemp in Example 3 were respectively added to 400 parts by weight of deionized water. After high-speed stirring at 6000 rpm for 20 min, 144 parts by weight of NaCl was added, and stirring was continued for 20 min to obtain drilling fluids F3, DF12 - DF15. The above drilling fluids were filled into a stainless steel aging tank and kept rolling at a constant temperature of 180°C for 16 hours. The apparent viscosity (AV, mPa·s), plastic viscosity (PV, mPa·s), yield point (YP, Pa), and API filtration loss FL API of the drilling fluid before and after aging were tested, and the results are shown in Table 4.

[0103] Table 4 Performance comparison of different types of viscosity increasing agents

[0104]

[0105] As can be seen from Table 4, under the conditions of 180°C and saturated NaCl, after adding 2% of the viscosity increasing and filtration loss reducing agent A3 in Example 3, the AV of the drilling fluid is 38.5 mPa·s, the PV is 29.0 mPa·s, the YP is 9.5 Pa, and the FL APIIt is 12.6 mL, higher than the AV, PV and YP of the drilling fluids added with HE300, 80A51, Driscal D and Dristemp, and the filtration loss is lower. This shows that the viscosity increasing and filtration loss reducing agent of the present invention has better temperature and salt resistance performance than domestic and foreign viscosity increasing agent products such as HE300, 80A51, Driscal D and Dristemp, and has better viscosity increasing, shear strengthening and filtration loss reducing effects under high temperature and high salt conditions.

[0106] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept scope of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0107] In addition, it should be noted that, among the various specific technical features described in the above specific embodiments, they can be combined in any appropriate way without conflict. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0108] In addition, any combination can be made between various different embodiments of the present invention, as long as it does not violate the idea of the present invention, it should also be regarded as the content disclosed by the present invention.

Claims

1. A temperature-resistant and salt-resistant cross-linked viscosity-increasing fluid loss reducer for soil-free water-based drilling fluid, characterized in that: The invention comprises the following raw materials in parts by weight: 15-25 parts of N,N-dimethylacrylamide, 1-10 parts of 3-[(3-methacrylamidopropyl)dimethylammonium]propane-1-sulfonate, 1-10 parts of long-chain alkyl polyoxyethylene ether methacrylate, 0.005-0.015 parts of macromolecular crosslinking agent, 0.03-0.08 parts of initiator A, and 80-100 parts of deionized water; The 3-[(3-methacrylamidopropyl)dimethylammonium]propane-1-sulfonate was prepared according to the following method: N-[3-(dimethylamino)propyl]methacrylamide is dissolved in acetonitrile to obtain solution 1, 1,3-propane sultone is dissolved in acetonitrile to obtain solution 2, solution 1 is added dropwise to solution 2, and after the addition is completed, a reaction is carried out; after the reaction is completed, the reaction is cooled, the solvent is removed, and the reaction is dried to obtain 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate; the molar ratio of N-[3-(dimethylamino)propyl]methacrylamide to 1,3-propane sultone is 1:1.2-3; The structural formula of the long-chain alkyl polyoxyethylene ether methacrylate is shown in Formula I below: Formula I; In Formula I, n is an integer between 20 and 30, and R is a straight chain hydrocarbon group having 16 to 25 carbon atoms; The macromolecular cross-linking agent is prepared according to the following method: (1) adding 2-acrylamide-2-methylpropanesulfonic acid and initiator B into deionized water, stirring evenly, to obtain an aqueous phase; the initiator B is azobisisobutylamidine dihydrochloride, azobisisobutyronitrile, ammonium persulfate or potassium persulfate, and the mass ratio of the initiator B to 2-acrylamide-2-methylpropanesulfonic acid is 0.01-0.1:10; (2) pentaerythritol triallyl ether, triallyl isocyanurate and cyclohexane are mixed, and then an emulsifier is added and stirred to obtain an oil phase; the mass ratio of pentaerythritol triallyl ether, triallyl isocyanurate and 2-acrylamido-2-methylpropane sulfonic acid is 0.05-0.10:0.05-0.10:5-10; and the emulsifier is a combination of Span 80 and Tween 80; (3) adding the water phase to the oil phase under stirring conditions, and then subjecting the resulting mixed system to shear emulsification to obtain a water-in-oil emulsion; Transfer it to a three-necked flask and react; after the reaction is completed, wash and dry to obtain a macromolecular crosslinking agent; the mass ratio of deionized water in the water phase to cyclohexane in the oil phase is 20-50:60-80; the reaction temperature is 50-70°C, and the reaction time is 3-5h; The initiator A is azobisisobutylamidine dihydrochloride, azobisisobutyronitrile, ammonium persulfate or potassium persulfate.

2. The temperature-resistant and salt-resistant cross-linked viscosity-increasing fluid loss reducer for soil-free water-based drilling fluid according to claim 1, characterized in that: The mass ratio of N-[3-(dimethylamino)propyl]methacrylamide to acetonitrile in the solution 1 is 1:3-15, and the mass ratio of 1,3-propane sultone to acetonitrile in the solution 2 is 1:2.5-12; the dripping rate of the solution 1 is 3-8 mL / min.

3. The temperature-resistant and salt-resistant cross-linked viscosity-increasing fluid loss reducer for soil-free water-based drilling fluid according to claim 1, characterized in that: In the preparation of 3-[(3-methacrylamidopropyl)dimethylammonio]propane-1-sulfonate, the reaction temperature is 70-90° C., the reaction time is 20-30 h; and the drying is vacuum drying at 80-100° C. for 20-30 h.

4. The temperature-resistant and salt-resistant cross-linked viscosity-increasing fluid loss reducer for soil-free water-based drilling fluid according to claim 1, characterized in that: The mass ratio of 2-acrylamido-2-methylpropanesulfonic acid to deionized water in step (1) is 1:2.5-7.

5. The temperature-resistant and salt-resistant cross-linked viscosity-increasing fluid loss reducer for soil-free water-based drilling fluid according to claim 1, characterized in that: In the composition of step (2), the mass ratio of Tween 80 to Span 80 is 1-3:2-6, and the mass ratio of the emulsifier to cyclohexane is 1:7-15.

6. The temperature-resistant and salt-resistant cross-linked viscosity-increasing fluid loss reducer for soil-free water-based drilling fluid according to claim 1, characterized in that: The stirring speed in step (3) is 500-1500 rpm; the shear emulsification speed is 5000-10000 rpm, and the shear emulsification time is 10-30 min; the washing is performed by immersion in ethanol for 3-5 times, and the drying is performed by vacuum drying at 80-100° C. for 20-30 h.

7. The method for preparing the temperature-resistant and salt-resistant cross-linked viscosity-increasing fluid loss reducer for soil-free water-based drilling fluid according to any one of claims 1 to 6, characterized in that: The steps include: N,N-dimethylacrylamide, 3-[(3-methacrylamidopropyl)dimethylammonium]propane-1-sulfonate, long-chain alkyl polyoxyethylene ether methacrylate and macromolecular crosslinking agent are added into deionized water and stirred evenly to obtain a mixed solution; the mixed solution is heated to a reaction temperature, and an initiator A is added to react; after the reaction is completed, the mixture is washed, dried and crushed to obtain a temperature-resistant and salt-resistant crosslinked viscosity-enhancing fluid loss reducer for a soil-free water-based drilling fluid.

8. The method for preparing the temperature-resistant and salt-resistant cross-linked viscosity-increasing fluid loss reducer for soil-free water-based drilling fluid according to claim 7, characterized in that: The reaction temperature is 60-80° C., and the reaction time is 3-5 hours. The washing is performed by washing with acetone for 2-3 times and then washing with anhydrous ethanol for 1-2 times. The drying is performed by vacuum drying at 80-100° C. to constant weight.

9. Use of the temperature-resistant and salt-resistant cross-linked viscosity-increasing fluid loss reducer for soil-free water-based drilling fluid according to any one of claims 1 to 6 in soil-free water-based drilling fluid, characterized in that: The concentration of the temperature-resistant and salt-resistant cross-linked viscosity-increasing fluid loss reducer for the soil-free water-based drilling fluid in the soil-free water-based drilling fluid is 1-2wt%.

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