A polymer viscosifier for oilfield fracturing and a preparation method thereof
By combining quaternary polymer thickeners, the problems of insufficient thickening capacity and poor filtration reduction performance of fracturing fluid in high temperature and high salinity environments are solved, enabling efficient fracturing operations under complex conditions and reducing reservoir damage and sand plugging risks.
Patent Information
- Application Number
- CN202610604300.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-05-06
- Publication Date
- 2026-06-26
AI Technical Summary
Existing fracturing fluid thickeners have insufficient thickening ability in high-temperature and high-salt environments, slow dissolution and dispersion rates, high frictional resistance, and poor filtration loss reduction performance, making it difficult to meet the construction requirements of complex working conditions and leading to increased reservoir damage and sand plugging risks.
A quaternary polymer thickener is used, which is composed of polyether, allyl malonic acid, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt and sodium p-styrene sulfonate. Through hydrogen bonding, steric hindrance effect, cross-linking reaction and dynamic network construction, the viscosity stability and sand carrying capacity of the thickener are improved.
It maintains high viscosity under high temperature and high salinity conditions, exhibits excellent shear resistance, reduces filtration loss and friction, improves the rheological properties of fracturing fluid, and reduces reservoir damage.
Smart Images
Figure CN122277824A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of petroleum extraction technology, specifically relating to a polymer thickener for oilfield fracturing and its preparation method. Background Technology
[0002] Fracturing is a core technology for enhancing the production of low-permeability oil and gas reservoirs. Its principle involves injecting fracturing fluid into the formation using a high-pressure pump system on the surface, creating artificial fractures with high conductivity within the reservoir. This improves the flow channels for oil and gas, thereby increasing production and injection. Thickeners, as the core additives in water-based fracturing fluids, primarily function to increase the viscosity of the fracturing fluid through the thickening effect of their polymer chains, achieving key properties such as proppant carrying, fracture creation, and reduced filtration loss. The performance of the thickener directly determines the success rate of fracturing operations, the conductivity of the fractures, and the final production enhancement effect.
[0003] Currently, commonly used fracturing fluid thickeners mainly fall into two categories: natural plant gums and their derivatives, and synthetic polymers. Natural plant gums, especially hydroxypropyl guar gum, dominate fracturing operations due to their rapid thickening and good sand-carrying capacity. However, these thickeners have significant limitations: firstly, they have a high content of water-insoluble matter, resulting in a large amount of residue after breaking down, which severely damages the conductivity of the reservoir and supported fractures; secondly, they have limited temperature and shear resistance, with viscosity decreasing rapidly under high-temperature deep well conditions, making it difficult to meet the requirements of complex operating conditions. In contrast, synthetic polymer thickeners, such as polyacrylamide and acrylamide copolymers, have advantages such as tunable molecular structure, low residue content, and relatively good temperature resistance, and are gradually becoming a research hotspot. However, existing synthetic polymer thickeners still face challenges in application, such as insufficient thickening capacity under high-temperature and high-salt environments, slow dissolution and dispersion rates, high frictional resistance, and poor filtration loss reduction performance.
[0004] With the large-scale development of unconventional oil and gas resources, reservoir conditions are becoming increasingly complex, placing higher demands on the scale of fracturing operations and the performance of fracturing fluids. Large-scale volumetric fracturing requires fracturing fluids to achieve rapid swelling within a very short time and maintain stable rheological properties during long-distance, high-friction pumping. Simultaneously, in high-temperature, high-salt reservoirs, the molecular chains of thickeners are prone to thermal and chemical degradation, leading to loss of proppant-carrying capacity and increasing the risk of proppant plugging. Therefore, developing a polymer thickener with rapid dissolution, high viscosity-enhancing efficiency, and excellent temperature and salt resistance is of significant practical importance for improving the fracturing effect in complex oil and gas reservoirs and reducing reservoir damage. Summary of the Invention
[0005] This invention addresses the shortcomings of existing technologies by providing a polymer thickener for oilfield fracturing and its preparation method. The polymer thickener of this invention has advantages such as high apparent viscosity, strong shear resistance, and strong salt and hardness resistance.
[0006] The first objective of this invention discloses a polymer thickener for oilfield fracturing, obtained by polymerizing the following four monomers:
[0007] (1) Polyether, the structural formula of which is as follows:
[0008]
[0009] Where n is a natural number between 5 and 50;
[0010] (2) Allylmalonic acid, the structural formula of which is as follows:
[0011]
[0012] (3) 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, the structural formula of which is as follows:
[0013]
[0014] (4) Sodium styrene sulfonate, the structural formula is as follows:
[0015] .
[0016] The second objective of this invention is to disclose a method for preparing the above-mentioned thickener, the specific steps of which are as follows:
[0017] S1. Add 2-methylallylamine and catalyst to the high-pressure reactor, purge the pipeline and reactor with nitrogen, evacuate, purge the pipeline and reactor with nitrogen again, and evacuate; raise the temperature to 80-85℃, slowly introduce ethylene oxide, after the introduction is complete, raise the temperature and maintain the reaction, the pressure gradually decreases, when the pressure no longer decreases, the reaction is complete, cool the system to below 40℃ to obtain polyether;
[0018] S2. Add polyether, allyl malonic acid, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, sodium p-styrene sulfonate, buffer salt, and deionized water to the reactor, stir, adjust the pH to 7-8, and purge the reactor with nitrogen.
[0019] S3. Add initiator dropwise, heat and maintain the temperature to react, and obtain a viscous liquid;
[0020] S4. Cool to room temperature, add ethanol to the above viscous liquid to precipitate the product, wash with ethanol 2-3 times, dry, and obtain the solid product polymer thickener.
[0021] Further, the mass ratio of ethylene oxide to 2-methylallylamine in step S1 is 6.2-62:1.
[0022] Further, the catalyst mentioned in step S1 is either solid sodium hydroxide or solid potassium hydroxide, and the weight ratio of it to 2-methylallylamine is 0.005-0.01:1.
[0023] Furthermore, the temperature of the heating and holding reaction described in step S1 is 100-160℃.
[0024] Further, the mass ratio of allyl malonic acid, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, sodium p-styrene sulfonate, and polyether in step S2 is 0.5-1:0.05-0.2:0.1-0.5:1.
[0025] Further, the mass ratio of the buffer salt, deionized water, and polyether in step S2 is 0.1-0.2:12-15:1. The buffer salt is one of potassium dihydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, and disodium hydrogen phosphate.
[0026] Further, the initiator mentioned in step S3 is a mixed solution of persulfate and sodium bisulfite, wherein the concentration of persulfate is 8-10 wt%, the concentration of sodium bisulfite is 3-5 wt%, and the weight ratio of initiator to polyether is 0.2-0.4:1.
[0027] Furthermore, the persulfate is one of potassium persulfate, ammonium persulfate, and sodium persulfate.
[0028] Furthermore, the heating and holding reaction temperature in step S3 is 70-90℃, and the time is 1-4h.
[0029] The polymer thickener of this invention is a quaternary polymer thickener. The polyether can form hydrogen bonds with water molecules through ether oxygen atoms, significantly improving the water solubility and dissolution rate of the thickener. The long polyether chain provides steric hindrance, shielding the negatively charged groups of the thickener molecular chain from the high-valence cations in formation water, inhibiting molecular chain coiling, and thus maintaining the viscosity stability of the thickener under high-salt conditions. The flexible polyether segments impart good toughness to the thickener molecular chain, reducing molecular chain breakage under high-temperature conditions, further enhancing the viscoelasticity and proppant carrying capacity of the fracturing fluid. Simultaneously, its adsorption on the rock surface can form a hydration film, reducing fracturing fluid filtration loss and tubing friction.
[0030] Allylmalonic acid provides a large number of carboxyl groups, which can greatly expand the polymer molecular chain after ionization in water, thereby significantly increasing the hydrodynamic volume and enabling the fracturing fluid to achieve high viscosity. The carboxylic acid group is the key site for the cross-linking reaction. The carboxylic acid group can undergo a complexation reaction with the metal cross-linking agent to form a three-dimensional network structure, resulting in an order-of-magnesium increase in viscosity. 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt is an amphoteric surfactant that is not sensitive to the external pH. At the same time, it can form weak associations intramolecularly and intermolecularly to construct a dynamic three-dimensional network, further improving the viscoelasticity and sand-carrying capacity of the fracturing fluid. The cationic quaternary ammonium salt can also inhibit clay swelling. Sodium styrene sulfonate is resistant to salt, high temperature, and calcium and magnesium precipitation. It can maintain the extension of the molecular chain under high salinity or hard water, ensuring the viscosity of the thickener is stable under harsh conditions. At the same time, the benzene ring has a strong anti-shear effect.
[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:
[0032] (1) The polymer thickener of the present invention has a high apparent viscosity. At 60°C, the viscosity of a 1500 mg / L concentration can reach up to 78 mPa•s.
[0033] (2) The polymer thickener of the present invention has good shear resistance, 170 s -1 After shearing at a certain rate for 2 hours, the viscosity retention rate can reach up to 93.6%;
[0034] (3) The polymer thickener of the present invention has good salt and hardness resistance. In a solution with a mineralization of 35000 mg / L and a hardness of 9600 mg / L, the viscosity retention rate can reach up to 89%. Detailed Implementation
[0035] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0036] Example 1 Preparation of polyether M1
[0037] (1) Add 6g of 2-methylallylamine and 0.03g of potassium hydroxide to the high-pressure reactor, purge the pipeline and reactor with nitrogen, evacuate, purge the pipeline and reactor with nitrogen again, and evacuate.
[0038] (2) Heat to 80°C and slowly introduce 37.2g of ethylene oxide. After the introduction is complete, heat to 100°C and keep the temperature for reaction. The pressure gradually decreases. When the pressure no longer decreases, the reaction is complete. Cool the system to below 40°C to obtain polyether M1.
[0039] Example 2 Preparation of polyether M2
[0040] (1) Add 6g of 2-methylallylamine and 0.042g of potassium hydroxide to the high-pressure reactor, purge the pipeline and reactor with nitrogen, evacuate, purge the pipeline and reactor with nitrogen again, and evacuate.
[0041] (2) Heat to 82°C and slowly introduce 98.8g of ethylene oxide. After the introduction is complete, heat to 118°C and keep the temperature for reaction. The pressure gradually decreases. When the pressure stops decreasing, the reaction is complete. Cool the system to below 40°C to obtain polyether M2.
[0042] Example 3 Preparation of polyether M3
[0043] (1) Add 6g of 2-methylallylamine and 0.044g of sodium hydroxide to the high-pressure reactor, purge the pipeline and reactor with nitrogen, evacuate, purge the pipeline and reactor with nitrogen again, and evacuate.
[0044] (2) Heat to 85°C and slowly introduce 204.3g of ethylene oxide. After the introduction is complete, heat to 145°C and keep the temperature for reaction. The pressure gradually decreases. When the pressure stops decreasing, the reaction is complete. Cool the system to below 40°C to obtain polyether M3.
[0045] Example 4 Preparation of polyether M4
[0046] (1) Add 6g of 2-methylallylamine and 0.06g of sodium hydroxide to the high-pressure reactor, purge the pipeline and reactor with nitrogen, evacuate, purge the pipeline and reactor with nitrogen again, and evacuate.
[0047] (2) Heat to 84°C and slowly introduce 372g of ethylene oxide. After the introduction is complete, heat to 160°C and keep the temperature for reaction. The pressure gradually decreases. When the pressure no longer decreases, the reaction is complete. Cool the system to below 40°C to obtain polyether M4.
[0048] Example 5 Preparation of Polymer Thickener
[0049] (1) Add 20g polyether M1, 10g allyl malonic acid, 4g 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, 2g sodium p-styrene sulfonate, 2g potassium dihydrogen phosphate, and 240g deionized water to the reactor, stir, adjust the pH to 7-8, and purge the reactor with nitrogen.
[0050] (2) Add 4g of initiator containing 8wt% sodium persulfate and 3wt% sodium bisulfite, heat to 90℃, keep the temperature for 1h, and obtain a viscous liquid.
[0051] (3) Cool down to room temperature, add ethanol to the above viscous liquid to precipitate the product, wash with ethanol twice, dry, and obtain the solid product polymer thickener.
[0052] Example 6 Preparation of Polymer Thickener
[0053] (1) Add 20g polyether M2, 12g allyl malonic acid, 3g 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, 5.5g sodium p-styrene sulfonate, 2.5g sodium dihydrogen phosphate, and 266g deionized water to the reactor, stir, adjust the pH to 7-8, and purge the reactor with nitrogen.
[0054] (2) Add 5.4g of initiator containing 10wt% potassium persulfate and 4wt% sodium bisulfite, heat to 85℃, keep the temperature for 2h, and obtain a viscous liquid.
[0055] (3) Cool down to room temperature, add ethanol to the above viscous liquid to precipitate the product, wash with ethanol 3 times, dry, and obtain solid product polymer thickener.
[0056] Example 7 Preparation of Polymer Thickener
[0057] (1) Add 20g polyether M3, 16g allyl malonic acid, 2g 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, 8g sodium p-styrene sulfonate, 3.4g dipotassium hydrogen phosphate, and 283g deionized water to the reactor, stir, adjust the pH to 7-8, and purge the reactor with nitrogen.
[0058] (2) Add 7g of initiator containing 9wt% sodium persulfate and 3.8wt% sodium bisulfite, heat to 70℃, keep the temperature for 4h, and obtain a viscous liquid.
[0059] (3) Cool down to room temperature, add ethanol to the above viscous liquid to precipitate the product, wash with ethanol 3 times, dry, and obtain solid product polymer thickener.
[0060] Example 8 Preparation of Polymer Thickener
[0061] (1) Add 20g polyether M4, 20g allyl malonic acid, 1g 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, 10g sodium p-styrene sulfonate, 4g disodium hydrogen phosphate, and 300g deionized water to the reactor, stir, adjust the pH to 7-8, and purge the reactor with nitrogen.
[0062] (2) Add 8g of initiator containing 10wt% ammonium persulfate and 5wt% sodium bisulfite, heat to 80℃, keep the temperature for 3h, and obtain a viscous liquid.
[0063] (3) Cool down to room temperature, add ethanol to the above viscous liquid to precipitate the product, wash with ethanol twice, dry, and obtain the solid product polymer thickener.
[0064] Example 9: Test of apparent viscosity
[0065] The polymer thickener of the present invention was prepared into a solution with a concentration of 1500 mg / L using tap water. The apparent viscosity μ0 was tested at 60°C in accordance with SY / T 6376-2008 "General Technical Conditions for Fracturing Fluids". Commercially available PAM was used as a comparative sample. The test results are shown in Table 1.
[0066] Example 10 Shear resistance test
[0067] The solution from Example 9 was subjected to 60°C for 170 seconds. - Under the conditions of continuous shearing for 2 hours, the apparent viscosity μ1 was tested. Commercially available PAM was used as a control sample. The test results are shown in Table 1.
[0068] Shear resistance is denoted as η1.
[0069] η1 = μ1 / μ0 × 100%
[0070] Example 11 Salt and Hardness Resistance Test
[0071] Prepare simulated water: Add sodium chloride and calcium chloride to the water to prepare simulated formation water with a salt content of 50,000 mg / L and a hardness of 12,000 mg / L.
[0072] The polymer thickener of the present invention was prepared into a solution with a concentration of 5000 mg / L using tap water, and diluted with simulated water at a ratio of 3:7 (V:V). The mineralization of the diluted solution was 35000 mg / L and the hardness was 9600 mg / L. The apparent viscosity μ2 was tested, and commercially available PAM was used as a comparison sample. The test results are shown in Table 1.
[0073] Shear resistance is denoted as η2.
[0074] η2 = μ2 / μ0 × 100%
[0075] Table 1. Test results of apparent viscosity, shear resistance, salt resistance, and hardness resistance.
[0076]
[0077] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A polymer thickener for oilfield fracturing, characterized in that, The polymer thickener is obtained by polymerization of the following four monomers: (1) Polyether, the structural formula of which is as follows: ， Where n is a natural number between 5 and 50; (2) Allylmalonic acid, the structural formula of which is as follows: ， (3) 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, the structural formula of which is as follows: ， (4) Sodium styrene sulfonate, the structural formula is as follows: 。 2. The method for preparing the polymer thickener according to claim 1, characterized in that, The specific steps of the preparation method are as follows: S1. Add 2-methylallylamine and catalyst to the high-pressure reactor, purge the pipeline and reactor with nitrogen, evacuate, purge the pipeline and reactor with nitrogen again, and evacuate; raise the temperature to 80-85℃, slowly introduce ethylene oxide, after the introduction is complete, raise the temperature and maintain the reaction, the pressure gradually decreases, when the pressure no longer decreases, the reaction is complete, cool the system to below 40℃ to obtain polyether; S2. Add polyether, allyl malonic acid, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, sodium p-styrene sulfonate, buffer salt, and deionized water to the reactor, stir, adjust the pH to 7-8, and purge the reactor with nitrogen. S3. Add initiator dropwise, heat and maintain the temperature to react, and obtain a viscous liquid; S4. Cool to room temperature, add ethanol to the above viscous liquid to precipitate the product, wash with ethanol 2-3 times, dry, and obtain the solid product polymer thickener.
3. The method for preparing the polymer thickener according to claim 2, characterized in that, The mass ratio of ethylene oxide to 2-methylallylamine in step S1 is 6.2-62:
1.
4. The method for preparing the polymer thickener according to claim 2, characterized in that, The catalyst mentioned in step S1 is either solid sodium hydroxide or solid potassium hydroxide, and the weight ratio of it to 2-methylallylamine is 0.005-0.01:
1.
5. The method for preparing the polymer thickener according to claim 2, characterized in that, The temperature of the heating and holding reaction in step S1 is 100-160℃.
6. The method for preparing the polymer thickener according to claim 2, characterized in that, The mass ratio of allyl malonic acid, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, sodium p-styrene sulfonate, and polyether in step S2 is 0.5-1:0.05-0.2:0.1-0.5:
1.
7. The method for preparing the polymer thickener according to claim 2, characterized in that, The mass ratio of buffer salt, deionized water and polyether in step S2 is 0.1-0.2:12-15:1; wherein the buffer salt is one of potassium dihydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, and disodium hydrogen phosphate.
8. The method for preparing the polymer thickener according to claim 2, characterized in that, The initiator mentioned in step S3 is a mixed solution of persulfate and sodium bisulfite, wherein the concentration of persulfate is 8-10 wt%, the concentration of sodium bisulfite is 3-5 wt%, and the weight ratio of initiator to polyether is 0.2-0.4:
1.
9. The method for preparing the polymer thickener according to claim 8, characterized in that, The persulfate mentioned is one of potassium persulfate, ammonium persulfate, and sodium persulfate.
10. The method for preparing the polymer thickener according to claim 2, characterized in that, The heating and holding reaction temperature in step S3 is 70-90℃, and the time is 1-4h.