Environment-friendly self-adaptive rheology modifier as well as preparation method and application thereof

Abstract

The invention discloses an environment-friendly self-adaptive rheology modifier and a preparation method and application thereof, and the preparation method comprises the following steps: dissolving a thermal response monomer, an ionic monomer and a crosslinking accelerator in deionized water, and adjusting the pH value to 7.0-8.0; the thermal response monomer is N-vinyl caprolactam; the ionic monomer is one or a mixture of acrylamide and sodium 2-acrylamide-2-methylpropanesulfonate; the ionic monomer is one or a mixture of acrylamide and sodium 2-acrylamide-2-methylpropanesulfonate; raising the temperature to 60-70 DEG C in an inert protection atmosphere, adding an initiator and a molecular weight control agent, and reacting for 4-6 hours at a constant temperature; pouring the reaction liquid into acetone to precipitate, and performing vacuum drying to obtain a white polymer; the lowest critical solution temperature of the obtained environment-friendly self-adaptive rheology modifier is 28-35 DEG C, the low-temperature apparent viscosity increase rate is smaller than or equal to 25% (2-10 DEG C), the high-temperature viscosity increase rate is larger than or equal to 30% (40-160 DEG C), the filter loss is smaller than or equal to 15 mL (API standard), the Zeta potential is smaller than or equal to-39.4 mV, the average particle size is larger than or equal to 3480 nm (containing 2% of bentonite-based slurry), and the environment friendliness is as follows: the biotoxicity is EC50gt; and 9 * 10 < 5 > mg / L.

Description

Technical Field

[0001] The invention belongs to the technical field of drilling, and in particular relates to an environmentally friendly adaptive rheology regulator and a preparation method and application thereof. Background Art

[0002] Against the backdrop of growing global energy demand and dwindling onshore oil and gas resources, offshore oil and gas fields have become crucial to future energy supply, with unlimited development potential. However, offshore oil and gas field development faces numerous challenges. The marine environment is complex and dynamic, and the drilling process faces challenges such as alternating high and low temperatures, high pressure, hydration expansion of shale formations, and the development of nanopores. Drilling fluid systems must be able to effectively cope with these complex environments, improve drilling efficiency, and reduce development costs, while also minimizing impacts on the marine environment and safeguarding marine ecosystems. Therefore, developing an appropriate drilling fluid system is crucial for the safe and efficient development of offshore oil and gas resources.

[0003] Currently, a prominent challenge facing offshore drilling is the impact of extreme temperature fluctuations. Low temperatures in deepwater (2-4°C) cause a sharp increase in drilling fluid viscosity, leading to increased pumping pressure and the risk of stuck drill bits. High-temperature reservoirs (>60°C) cause a decrease in viscosity, impairing rock-carrying capacity. Existing rheology modifiers such as carboxymethyl cellulose and xanthan gum experience viscosity increases exceeding 45% at low temperatures and high-temperature fluid loss exceeding 35 mL. Their effectiveness in alternating high and low-temperature environments is poor, and their biotoxicity makes them difficult to meet marine environmental protection requirements.

[0004] Chinese patent document CN109054782B develops a thermosensitive polymer rheology modifier based on a copolymer of alkenylamide and alkenylsulfonic acid. This modifier exhibits the characteristics of high-temperature viscosity increase and low-temperature viscosity reduction in seawater-based drilling fluids. However, it does not include biotoxicity data for degradation products, making it difficult to meet the environmental protection requirements of deepwater drilling.

[0005] Chinese patent document CN111849435B proposes a smart temperature-responsive polymer for biodiesel-based drilling fluids, which achieves constant rheology through the structural units of dihydroxyethyl dihydroxypropyl stearyl ammonium chloride and dimerized fatty acids. Although this technology shows good temperature adaptability within 120°C, it has a significant low-temperature viscosity-increasing effect. At 5°C, the dynamic shear force (YP) increases by more than 35%, resulting in an increased risk of ECD (equivalent circulating density) loss of control in deepwater drilling. In addition, this material relies on biodiesel as a base oil, and the EC of its degradation products is 50 The value is only about 1.2×10 4 mg / L, potentially toxic to marine plankton.

[0006] Some patents are dedicated to the development of adaptive modifiers. However, these agents suffer from issues such as a narrow temperature range, uneven viscosity adjustment, highly toxic degradation products, and inadequate fluid loss control. These agents struggle to fully meet the complex demands of offshore drilling, such as deepwater, low-temperature, and high-temperature, high-pressure environments, requiring high efficiency, environmental friendliness, and temperature adaptability. Given the alternating high and low-temperature environments encountered in offshore drilling, there is an urgent need to develop an environmentally friendly, temperature-adaptive rheological modifier suitable for both deepwater, low-temperature, and high-temperature reservoirs, providing technical support for deep ocean drilling and deep-earth oil and gas resource development. Summary of the Invention

[0007] Traditional rheology modifiers cannot maintain good rheological parameters at low temperatures, and the plastic viscosity and dynamic shear force increase significantly beyond the reasonable range. To address the defects of existing rheology modifiers such as narrow temperature adaptability and high environmental toxicity, the present invention proposes a temperature-adaptive rheology modifier based on a composite of thermally responsive monomers and ionic monomers. Through molecular structure design and polymerization process optimization, it achieves the unity of two-way rheological regulation and marine environmental protection.

[0008] In order to achieve the above purpose, the technical solutions adopted are as follows: A method for preparing an environmentally friendly adaptive rheology modifier comprises the following steps: (1) Dissolve the thermoresponsive monomer, ionic monomer, and crosslinking accelerator in deionized water and adjust the pH to 7.0-8.0; (2) Raise the temperature to 60-70°C under an inert protective atmosphere, add initiator and molecular weight control agent, and react at constant temperature for 4-6 hours; (3) The reaction solution was poured into acetone for precipitation and vacuum dried to obtain a white powder.

[0009] According to the above scheme, the thermoresponsive monomer in step (1) is N-vinyl caprolactam (NVCL). The LCST regulates the core, with low-temperature hydrophilicity inhibiting viscosity increase and high-temperature hydrophobicity self-assembly increasing viscosity. According to the above scheme, the ionic monomer in step (1) is one or a mixture of acrylamide (AM) and sodium 2-acrylamido-2-methylpropanesulfonate (AMPS). The sulfonic acid group improves temperature resistance and dispersion stability.

[0010] According to the above scheme, the cross-linking accelerator in step (1) is γ-methacryloxypropyltrimethoxysilane (KH570), which enhances the cross-linking degree of the molecular chain and forms a three-dimensional network structure.

[0011] According to the above scheme, the initiator in step (2) is ammonium persulfate (APS).

[0012] According to the above scheme, the molecular weight control agent in step (2) is dodecyl mercaptan. The molecular weight control agent regulates the molecular weight of the polymer to 50k~200kDa.

[0013] According to the above scheme, in step (3), the vacuum drying temperature is 60°C, and the drying time is more than 24 h.

[0014] According to the above scheme, the raw materials are as follows by weight parts: The thermoresponsive monomer: 30 - 50 parts; the ionic monomer: 20 - 40 parts; the crosslinking promoter: 5 - 15 parts; deionized water 200 - 500 parts; the molecular weight controller: 1 - 5 parts; the initiator: 0.1 - 0.5 parts.

[0015] An environment-friendly self-adaptive rheological regulator is prepared by adopting the above technical scheme.

[0016] The present invention also provides an application of the environment-friendly self-adaptive rheological regulator in offshore drilling, and the addition amount of the rheological regulator is 0.5 - 1.5 wt%.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: The product obtained by the present invention has undergone molecular structure design and polymerization process optimization. Through the synergistic effect of the ionic shielding effect of the ionic monomer and the temperature-sensitive switching effect of the thermoresponsive monomer, it is realized that the viscosity increase is inhibited at low temperature (<LCST) (dominated by electrostatic repulsion), and hydrophobic association thickening is triggered at high temperature (>LCST) (crosslinking of NVCL hydrophobic microdomains). Strict pH and oxygen control in the polymerization process ensure the regularity of the terpolymer structure, broadening the rheological regulation window. AM provides a rigid main chain backbone and hydrogen bond sites, enhancing the mechanical strength of the polymer and supporting the network structure stability at high temperature; AMPS (sulfonate monomer): provides electrostatic repulsion through strong hydration sulfonic acid groups (-SO3 - ), inhibits the aggregation of molecular chains at low temperature, maintains low viscosity at low temperature, and enhances the salt tolerance at the same time. The pH is adjusted to neutral: to avoid the protonation failure of the sulfonic acid group of AMPS under acidic conditions, ensure the full participation of the ionic monomer in polymerization, and maintain charge stability.

[0018] The product obtained by the present invention has the characteristic of temperature self-adaptation. Core mechanism of N-vinylcaprolactam: LCST-type phase change drives bidirectional rheological regulation. At low temperature, hydrophilicity inhibits viscosity increase (<LCST), and the molecular behavior is that the caprolactam ring of NVCL strongly interacts with water molecules through hydrogen bonds, and the molecular chains are fully extended. The rheological effect is that the sulfonic acid groups of AMPS generate strong electrostatic repulsion, preventing molecular chain entanglement, and significantly reducing the plastic viscosity and dynamic shear force at low temperature. At high temperature, hydrophobic self-assembly thickens (>LCST), and the molecular behavior is that when the temperature exceeds LCST (about 32 - 35°C), the isopropyl side chain of NVCL dehydrates, and the cyclic structure turns hydrophobic, triggering intra / intermolecular hydrophobic association and forming a physical crosslinking network. The rheological effect is that hydrophobic microdomains act as "dynamic crosslinking points" at high temperature, greatly enhancing the shear stability, and the rheological properties do not show a significant decline.

[0019] The product obtained by the present invention has the characteristics of environmental protection. (1) Biodegradability design. The caprolactam structure of NVCL can be hydrolyzed and degraded by microorganisms (compared with persistent pollutants such as polyacrylonitrile); the linear structure of AM / AMPS is more easily enzymatically degraded than branched / aromatic polymers. (2) Low ecotoxicity and no heavy metals. Traditional regulators contain metals such as zinc and copper (such as ZnO flow regulators) and are prone to accumulation in marine sediments. Compared with halogen monomers (such as brominated acrylates), the sulfonic acid group of AMPS has significantly reduced toxicity to aquatic organisms. (3) Green synthesis process. Aqueous polymerization: avoids organic solvent (such as toluene) residues and does not require a halogen-free initiation system. The decomposition product of APS is ammonium sulfate, which can be naturally degraded into nitrogen / sulfur salts.

[0020] The environmentally friendly adaptive rheology modifier obtained by the present invention has a lower critical solution temperature (LCST) of 28-35°C, a low-temperature apparent viscosity increase of ≤25% (2-10°C), a high-temperature viscosity increase rate of ≥30% (40-160°C), a filtration loss of ≤15 mL (API standard), a Zeta potential of ≤-39.4 mV, an average particle size of ≥3480 nm (containing 2% bentonite-based slurry), and environmental protection: biological toxicity EC 50 >9×10 5 mg / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 : The synthetic route of the adaptive rheology modifier of the present invention. DETAILED DESCRIPTION

[0022] The following examples further illustrate the technical solutions of the present invention but are not intended to limit the scope of protection of the present invention.

[0023] Example 1 An environmentally friendly temperature-adaptive rheology modifier suitable for marine drilling is prepared from the following raw materials in parts by weight: an ionic monomer: 15 parts of acrylamide and 15 parts of sodium 2-acrylamido-2-methylpropanesulfonate; a thermally responsive monomer: 40 parts of N-vinylcaprolactam; a cross-linking accelerator: 10 parts of KH570; 400 parts of deionized water; a molecular weight control agent: 3 parts of dodecyl mercaptan; and an initiator: 0.15 parts of ammonium persulfate.

[0024] The preparation method of the above-mentioned environmentally friendly temperature adaptive rheology regulator for ocean drilling, the reaction mechanism is shown in the attached Figure 1 As shown, the steps include: (1) Solution preparation: Add the thermoresponsive monomer, ionic monomer, and cross-linking accelerator into deionized water for copolymerization, and adjust the pH to 7.5 with NaOH; (2) Nitrogen protection polymerization: Add initiator and molecular weight control agent at 70°C and react for 6 h; (3) Precipitate with acetone and dry in vacuum at 60°C for 24 h to obtain a white powder.

[0025] In a specific embodiment, the test slurry preparation process is as follows: 2% attapulgite slurry is used as the base slurry, 0.5% carboxymethyl cellulose (CMC), 0.5% xanthan gum (XC), and 1% rheology modifier obtained in the embodiment are added respectively, and a high-speed stirrer is used at a stirring speed of 5000 r / min for a total stirring time of 30 minutes. The slurry viscosity is measured using a six-speed rotary viscometer, the slurry filtration loss is measured using a medium-pressure filter loss meter, the slurry Zeta potential is measured using a zeta potential meter, and the slurry EC is measured using the Petroleum and Natural Gas Industry Standard SY / T 7467-2020 of the People's Republic of China. 50 value.

[0026] The temperature-adaptive rheology modifier prepared in this example was measured to have an LCST of 32°C, a plastic viscosity of 20 mPa·s at 2°C, a plastic viscosity of 25 mPa·s at 160°C, a filtration loss of 15 mL at 160°C, a Zeta potential of -39.4 mV, and an EC 50 =9.2×10 5 mg / L.

[0027] Example 2 An environmentally friendly temperature-adaptive rheology modifier suitable for marine drilling is prepared from the following raw materials in parts by weight: an ionic monomer: 10 parts of acrylamide and 10 parts of sodium 2-acrylamide-2-methylpropanesulfonate; a thermally responsive monomer: 50 parts of N-vinylcaprolactam; a cross-linking accelerator: 15 parts of KH570; 500 parts of deionized water; a molecular weight control agent: 1 part of dodecyl mercaptan; and an initiator: 0.5 parts of ammonium persulfate.

[0028] The preparation method of the environmentally friendly temperature-adaptive rheology regulator for ocean drilling is the same as that in Example 1, except that the reaction is carried out at 70° C. for 5 hours under nitrogen protection polymerization conditions.

[0029] The temperature-adaptive rheology modifier prepared in this example was measured to have an LCST of 28°C, a plastic viscosity of 18 mPa·s at 2°C, a plastic viscosity of 23 mPa·s at 160°C, a filtration loss of 12 mL at 160°C, a Zeta potential of -38.2 mV, and an EC 50 =9×10 5 mg / L.

[0030] Example 3 An environmentally friendly temperature-adaptive rheology modifier suitable for marine drilling is prepared from the following raw materials in parts by weight: an ionic monomer: 15 parts of acrylamide and 20 parts of sodium 2-acrylamido-2-methylpropanesulfonate; a thermally responsive monomer: 35 parts of N-vinylcaprolactam; a cross-linking accelerator: 8 parts of KH570; 300 parts of deionized water; a molecular weight control agent: 4 parts of dodecyl mercaptan; and an initiator: 0.2 parts of ammonium persulfate.

[0031] The preparation method of the environmentally friendly temperature-adaptive rheology regulator for ocean drilling is the same as that in Example 1, except that the polymerization is carried out at 65° C. for 6.5 hours under nitrogen protection.

[0032] The temperature-adaptive rheology modifier prepared in this example was measured to have an LCST of 35°C, a plastic viscosity of 17 mPa·s at 2°C, a plastic viscosity of 22 mPa·s at 160°C, a filtration loss of 14 mL at 160°C, a Zeta potential of -38.6 mV, and an EC 50 =8.8×10 5 mg / L.

[0033] Example 4 An environmentally friendly temperature-adaptive rheology modifier suitable for marine drilling is prepared from the following raw materials in parts by weight: an ionic monomer (5 parts acrylamide) and 10 parts sodium 2-acrylamido-2-methylpropanesulfonate), a thermally responsive monomer (45 parts N-vinylcaprolactam), a cross-linking accelerator (12 parts KH570), 450 parts deionized water, a molecular weight controller (2 parts dodecyl mercaptan), and an initiator (0.3 parts ammonium persulfate).

[0034] The preparation method of the environmentally friendly temperature-adaptive rheology modifier for ocean drilling is the same as that in Example 1, except that the pH is adjusted to 8 with NaOH, and the reaction is carried out at 68° C. for 5.5 hours under nitrogen protection polymerization conditions.

[0035] The temperature-adaptive rheology modifier prepared in this example was measured to have a LCST of 30°C, a plastic viscosity of 16 mPa·s at 2°C, a plastic viscosity of 28 mPa·s at 160°C, a filtration loss of 16 mL at 160°C, a Zeta potential of -39.1 mV, and an EC 50 =8.6×10 5 mg / L.

[0036] Comparative Example 1 An environmentally friendly temperature-adaptive rheology modifier suitable for marine drilling is prepared from the following raw materials in parts by weight: ionic monomers: 15 parts of partially hydrolyzed polyacrylamide (HPAM) and 15 parts of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS); a thermally responsive monomer: 40 parts of N-vinylcaprolactam (NVCL); a cross-linking accelerator: 10 parts of KH570; 400 parts of deionized water; a molecular weight controller: 3 parts of dodecyl mercaptan; and an initiator: 0.15 parts of ammonium persulfate (APS).

[0037] The preparation method of the above-mentioned environmentally friendly temperature-adaptive rheology modifier for ocean drilling comprises the following steps: (1) Solution preparation: Add the thermoresponsive monomer, ionic monomer, and cross-linking accelerator into deionized water for copolymerization, and adjust the pH to 7.5 with NaOH; (2) Nitrogen protection polymerization: Add initiator and molecular weight control agent at 70°C and react for 6 h; (3) Precipitate with acetone and dry in vacuum at 60°C for 24 h to obtain a white powder.

[0038] The temperature-adaptive rheology modifier prepared in this example was measured to have an LCST of 32°C, a plastic viscosity of 16 mPa·s at 2°C, a plastic viscosity of 9 mPa·s at 160°C (the plastic viscosity decreases significantly at high temperatures), a filtration loss of 20 mL at 160°C, a Zeta potential of -36.2 mV, and an EC 50 =6.3×10 5 mg / L.

[0039] Comparative Example 2 An environmentally friendly temperature-adaptive rheology modifier suitable for marine drilling is prepared from the following raw materials in parts by weight: ionic monomers: 15 parts of acrylamide (AM) and 15 parts of highly hydrolyzed polyacrylic acid (PAA); a thermally responsive monomer: 40 parts of N-vinyl caprolactam (NVCL); a cross-linking accelerator: 10 parts of KH570; 400 parts of deionized water; a molecular weight controller: 3 parts of dodecyl mercaptan; and an initiator: 0.15 parts of ammonium persulfate (APS).

[0040] The preparation method of the above-mentioned environmentally friendly temperature-adaptive rheology modifier for ocean drilling comprises the following steps: (1) Solution preparation: Add the thermoresponsive monomer, ionic monomer, and cross-linking accelerator into deionized water for copolymerization, and adjust the pH to 7.5 with NaOH; (2) Nitrogen protection polymerization: Add initiator and molecular weight control agent at 70°C and react for 6 h; (3) Precipitate with acetone and dry in vacuum at 60°C for 24 h to obtain a white powder.

[0041] The temperature-adaptive rheology modifier prepared in this example was measured to have an LCST of 35°C, a plastic viscosity of 55 mPa·s at 2°C (the plastic viscosity increases significantly at low temperatures), a plastic viscosity of 25 mPa·s at 160°C, a filtration loss of 33 mL at 160°C (the filtration loss increases significantly at high temperatures), a zeta potential of -35.6 mV, and an EC 50 =7.6×10 5 mg / L.

[0042] Comparative Example 3 An environmentally friendly temperature-adaptive rheology modifier suitable for marine drilling is prepared from the following raw materials in parts by weight: an ionic monomer: 15 parts of acrylamide (AM) and 15 parts of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS); a thermally responsive monomer: 40 parts of N-isopropylacrylamide (NIPAM); a cross-linking accelerator: 10 parts of KH570; 400 parts of deionized water; a molecular weight controller: 3 parts of dodecyl mercaptan; and an initiator: 0.15 parts of ammonium persulfate (APS).

[0043] The preparation method of the above-mentioned environmentally friendly temperature-adaptive rheology modifier for ocean drilling comprises the following steps: (1) Solution preparation: Add the thermoresponsive monomer, ionic monomer, and cross-linking accelerator into deionized water for copolymerization, and adjust the pH to 7.5 with NaOH; (2) Nitrogen protection polymerization: Add initiator and molecular weight control agent at 70°C and react for 6 h; (3) Precipitate with acetone and dry in vacuum at 60°C for 24 h to obtain a white powder.

[0044] The temperature-adaptive rheology modifier prepared in this example was measured to have an LCST of 10°C (a significant decrease in the lowest critical solution temperature), a plastic viscosity of 40 mPa·s at 2°C (a significant increase in the plastic viscosity at low temperatures), a plastic viscosity of 12 mPa·s at 160°C (a significant decrease in the plastic viscosity at high temperatures), a filtration loss of 20 mL at 160°C, a zeta potential of -37.1 mV, and an EC 50 =6.8×10 5 mg / L.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an environmentally friendly adaptive rheology regulator, characterized in that The following steps are involved: (1) Dissolve the thermoresponsive monomer, ionic monomer, and crosslinking accelerator in deionized water and adjust the pH to 7.0-8.0; (2) Raise the temperature to 60-70°C under an inert protective atmosphere, add initiator and molecular weight control agent, and react at constant temperature for 4-6 hours; (3) The reaction solution was poured into acetone for precipitation and vacuum dried to obtain a white powder.

2. The method for preparing the environmentally friendly adaptive rheology modifier according to claim 1, characterized in that The thermally responsive monomer in step (1) is N-vinyl caprolactam.

3. The method for preparing the environmentally friendly adaptive rheology modifier according to claim 1, characterized in that The ionic monomer in step (1) is one of acrylamide and sodium 2-acrylamide-2-methylpropanesulfonate or a mixture thereof.

4. The method for preparing the environmentally friendly adaptive rheology modifier according to claim 1, characterized in that The cross-linking accelerator in step (1) is γ-methacryloxypropyltrimethoxysilane.

5. The method for preparing the environmentally friendly adaptive rheology modifier according to claim 1, characterized in that The initiator in step (2) is ammonium persulfate.

6. The method for preparing the environmentally friendly adaptive rheology modifier according to claim 1, characterized in that The molecular weight control agent in step (2) is dodecyl mercaptan.

7. The method for preparing the environmentally friendly adaptive rheology modifier according to claim 1, characterized in that In step (3), the vacuum drying temperature is 60°C and the drying time is more than 24 h.

8. The method for preparing the environmentally friendly adaptive rheology modifier according to claim 1, characterized in that The raw materials are calculated by weight as follows: The thermal response monomer: 30-50 parts; the ionic monomer: 20-40 parts; the cross-linking accelerator: 5-15 parts; deionized water: 200-500 parts; molecular weight control agent: 1-5 parts; Initiator: 0.1-0.5 parts.

9. An environmentally friendly adaptive rheology regulator, characterized in that The environmentally friendly adaptive rheology regulator is prepared by the preparation method of any one of claims 1 to 8.

10. Use of the environmentally friendly adaptive rheology modifier according to claim 9 in ocean drilling, wherein the addition amount of the rheology modifier is 0.5-1.5 wt%.

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