A polymer suitable for high salinity high suspended solids low charge

Abstract

A polymer suitable for high-salinity, high-suspended-matter, and low-charge oilfield fracturing fluids is disclosed, comprising the following components by weight: 20-30 parts N-methoxymethylacrylamide, 15-20 parts polyethylene glycol diacrylate, 15-20 parts acryloylmorpholine, 15-20 parts N-vinylcaprolactam, 10-15 parts polyethylene glycol monoallyl ether, 0.2-0.4 parts glycerol diallyl ether, 0.1-0.3 parts cumene hydroperoxide, 0.1-0.3 parts diethylethanolamine, and 70-90 parts deionized water. The polymer synthesized in this invention has a low charge, effectively reducing adsorption with negatively charged clay minerals in the formation, thus minimizing polymer loss and formation damage. This invention effectively solves the problem of insufficient performance of traditional polymers in fracturing fluids under special reservoir conditions, enabling efficient fracturing stimulation of high-salinity, high-suspended-matter reservoirs.

Description

Technical Field

[0001] This invention belongs to the field of oilfield fracturing fluids, specifically a polymer suitable for high salinity, high suspended matter, and low charge. Background Technology

[0002] In oilfield development, fracturing is one of the key technologies for improving oil and gas recovery. Fracturing fluid, as the core working fluid in the fracturing process, directly affects the fracturing effect and the productivity of oil and gas wells. Traditional polymer thickeners for fracturing fluids, such as partially hydrolyzed polyacrylamide (HPAM), exhibit good thickening performance and proppant carrying capacity in low-salinity, low-suspended-matter clean water or saline water. However, in some special reservoir environments, such as high-salinity formation water and high-suspended-matter conditions, traditional polymers face severe challenges. High-salinity ions severely damage the hydration film of polymer molecular chains, causing the molecular chains to coil and fail to fully extend, resulting in a sharp decrease in the viscosity of the fracturing fluid and a weakened proppant carrying capacity. Simultaneously, the presence of high suspended matter not only causes physical entanglement or chemical adsorption with polymer molecules, consuming the effective polymer concentration, but may also form blockages in fractures, reducing their conductivity. Furthermore, some traditional polymers have high charge density, easily adsorbing with negatively charged clay minerals in the formation, causing significant polymer loss and formation damage. Summary of the Invention

[0003] This invention provides a polymer suitable for high mineralization, high suspended matter, and low charge, in order to overcome the deficiencies in the prior art.

[0004] This invention is achieved through the following technical solution: A polymer suitable for high mineralization, high suspended matter, and low charge comprises the following substances in parts by weight: 20-30 parts N-methoxymethacrylamide, 15-20 parts polyethylene glycol diacrylate, 15-20 parts acryloylmorpholine, 15-20 parts N-vinylcaprolactam, 10-15 parts polyethylene glycol monoallyl ether, 0.2-0.4 parts glycerol diallyl ether, 0.1-0.3 parts cumene hydroperoxide, 0.1-0.3 parts diethylethanolamine, and 70-90 parts deionized water.

[0005] The N-methoxymethylacrylamide, as described above, is suitable for polymers with high mineralization, high suspended matter, and low charge, and has a purity ≥95%.

[0006] As described above, a polymer suitable for high mineralization, high suspended matter, and low charge is wherein the average molecular weight of the polyethylene glycol diacrylate is 2000-3000, and the average molecular weight of the polyethylene glycol monoallyl ether is 2000-2500.

[0007] As described above, a polymer suitable for high mineralization, high suspended matter, and low charge is wherein the purity of the acryloylmorpholine is ≥98% and the purity of the N-vinylcaprolactam is ≥98%.

[0008] As described above, for a polymer suitable for high mineralization, high suspended matter, and low charge, the purity of the diallyl glycerol is ≥99.5%.

[0009] As described above, a polymer suitable for high mineralization, high suspended matter, and low charge is wherein the purity of the cumene hydrogen peroxide is ≥80%, and the purity of the diethylethanolamine is ≥99%.

[0010] The preparation method of the polymer described above, which is suitable for high mineralization, high suspended matter, and low charge, includes the following steps: Step 1: Weigh out the following ingredients according to the specified ratio: N-methoxymethacrylamide, polyethylene glycol diacrylate, acrylomorpholine, N-vinylcaprolactam, polyethylene glycol monoallyl ether, glyceryl diallyl ether, cumene hydrogen peroxide, diethylethanolamine, and deionized water. Step 2: Add N-methoxymethacrylamide, polyethylene glycol diacrylate, acrylmorpholine, N-vinylcaprolactam, polyethylene glycol monoallyl ether, and 90% by mass of deionized water to a sealed reactor and mix. Step 3: Dissolve diallyl ether, cumene hydrogen peroxide, and diethylethanolamine in the remaining 10% by mass of deionized water; Step 4: Add the solution obtained in Step 3 dropwise at a uniform rate to the sealed reaction vessel after mixing in Step 2 to carry out the reaction; Step 5: After the reaction is complete, a polymer suitable for high mineralization, high suspended matter, and low charge is obtained.

[0011] As described above, for a polymer suitable for high mineralization, high suspended matter, and low charge, the mixing temperature in step two is 40-50℃, the mixing speed is 100-150 rad / min, and the mixing time is 50-60 min.

[0012] As described above, for a polymer suitable for high mineralization, high suspended matter, and low charge, the dissolution temperature in step three is 30-40℃, the stirring speed is 100-150 rad / min, and the dissolution time is 15-20 min.

[0013] As described above, for a polymer suitable for high mineralization, high suspended matter, and low charge, in step four, the sealed reactor is heated to 60-70°C, the stirring speed is adjusted to 200-250 rad / min, and nitrogen gas is introduced through the air vent to begin dripping the solution obtained in step three. The dripping time is 80-90 min, and after the dripping is completed, the reaction continues for 2-2.5 h. Nitrogen gas is continuously introduced for protection throughout the entire dripping and reaction process.

[0014] The advantages of this invention are: the polymer synthesized in this invention has a low charge, which can effectively reduce adsorption with negatively charged clay minerals in the formation, thereby reducing polymer loss and damage to the formation; simultaneously, this invention introduces polyethylene glycol diacrylate and acryloylmorpholine, which have strong hydration capabilities. Under high salinity conditions, these groups can maintain the good extension state of the molecular chain by forming stable hydrogen bonds with water molecules, thus ensuring that the fracturing fluid has high viscosity and excellent sand-carrying capacity; moreover, the synergistic effect of N-methoxymethylacrylamide and N-vinylcaprolactam units in this invention endows the polymer with good salt-resistant thickening properties and thermal stability, maintaining the stability of the molecular structure even under high temperature and high salt conditions, and is not prone to degradation; in addition, the introduction of polyethylene glycol monoallyl ether in this invention optimizes the water solubility and molecular chain of the polymer. The flexibility of the fracturing fluid reduces non-specific adsorption and entanglement with high-suspended-matter particles, avoiding the reduction of effective polymer concentration and fracture clogging problems. This allows the fracturing fluid to maintain good flow performance and proppant carrying efficiency even in high-suspended-matter environments. In this invention, the synergistic effect of diallyl ether, cumene hydrogen peroxide, and diethylethanolamine constructs an efficient and mild initiation system that can rapidly initiate monomer polymerization at lower temperatures, improving reaction efficiency. At the same time, it can also form a moderate cross-linking network between polymer molecular chains, further enhancing the thickening effect and shear stability of the polymer. This allows the fracturing fluid to withstand high shear forces during operation, maintain stable viscosity, and ensure proppant carrying and fracture creation effects. This invention effectively solves the problem of insufficient performance of traditional polymer fracturing fluids in special reservoir environments, and can efficiently complete the fracturing and stimulation of reservoirs with high salinity and high suspended-matter. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1This is a schematic diagram showing the drag reduction of polymers prepared in Examples 1-3 of the present invention, suitable for high mineralization, high suspended matter, and low charge, in clear water (where the blue line represents Example 1, the green line represents Example 2, and the red line represents Example 3). Figure 2 This is a schematic diagram showing the drag reduction rate of polymers prepared in Examples 1-3 of the present invention, suitable for high mineralization, high suspended matter, and low charge, in a 1% potassium chloride aqueous solution (where the blue line represents Example 1, the green line represents Example 2, and the red line represents Example 3). Figure 3 This is a schematic diagram of the liquid settling method for detecting polymers with high mineralization, high suspended matter, and low charge prepared in Example 3 of the present invention; Figure 4 This is a schematic diagram of the static sand-carrying performance test of the polymer prepared in Example 3 of the present invention, which is suitable for high mineralization, high suspended matter and low charge. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0018] Step 1: Weigh out the following ingredients according to the specified ratio: 20 parts N-methoxymethacrylamide (purity 96.3%), 15 parts polyethylene glycol diacrylate (average molecular weight 2000), 15 parts acryloylmorpholine (purity 98.5%), 15 parts N-vinylcaprolactam (purity 98.2%), 10 parts polyethylene glycol monoallyl ether (average molecular weight 2000), 0.2 parts glyceryl diallyl ether (purity 99.5%), 0.1 parts cumene hydrogen peroxide (purity 81.7%), 0.1 parts diethylethanolamine (purity 99.1%), and 70 parts deionized water. Step 2: Add N-methoxymethacrylamide, polyethylene glycol diacrylate, acrylmorpholine, N-vinylcaprolactam, polyethylene glycol monoallyl ether, and 90% by mass of deionized water to a sealed reactor for mixing. The mixing temperature is 40℃, the mixing speed is 100 rad / min, and the mixing time is 60 min. Step 3: Add diallyl ether, cumene hydrogen peroxide and diethylethanolamine to the remaining 10% of deionized water to dissolve them. The dissolution temperature is 30℃, the stirring speed is 100 rad / min, and the dissolution time is 20 min. Step 4: Heat the sealed reactor to 60°C, adjust the stirring speed to 200 rad / min, and introduce nitrogen gas through the air vent to start adding the solution obtained in Step 3. The adding time is 90 min. After the adding is completed, continue the reaction for 2.5 h. Nitrogen gas is continuously introduced for protection throughout the adding and reaction process. Step 5: After the reaction is complete, a polymer suitable for high mineralization, high suspended matter, and low charge is obtained. Example 2

[0019] Step 1: Weigh out the following ingredients according to the specified ratio: 30 parts N-methoxymethacrylamide (purity 96.3%), 20 parts polyethylene glycol diacrylate (average molecular weight 3000), 20 parts acryloylmorpholine (purity 98.5%), 20 parts N-vinylcaprolactam (purity 98.2%), 15 parts polyethylene glycol monoallyl ether (average molecular weight 2500), 0.4 parts glyceryl diallyl ether (purity 99.5%), 0.3 parts cumene hydrogen peroxide (purity 81.7%), 0.3 parts diethylethanolamine (purity 99.1%), and 90 parts deionized water. Step 2: Add N-methoxymethacrylamide, polyethylene glycol diacrylate, acrylmorpholine, N-vinylcaprolactam, polyethylene glycol monoallyl ether, and 90% by mass of deionized water to a sealed reactor for mixing. The mixing temperature is 50℃, the mixing speed is 150 rad / min, and the mixing time is 50 min. Step 3: Dissolve diallyl ether, cumene hydrogen peroxide and diethylethanolamine in the remaining 10% of deionized water at a temperature of 40°C, a stirring speed of 150 rad / min and a dissolution time of 15 min. Step 4: Heat the sealed reactor to 70°C, adjust the stirring speed to 250 rad / min, and introduce nitrogen gas through the air vent to begin adding the solution obtained in Step 3. The adding time is 80 min. After the adding is completed, continue the reaction for 2 h. Nitrogen gas is continuously introduced for protection throughout the adding and reaction process. Step 5: After the reaction is complete, a polymer suitable for high mineralization, high suspended matter, and low charge is obtained. Example 3

[0020] Step 1: Weigh out the following components according to the specified ratio: 25 parts N-methoxymethacrylamide (purity 96.3%), 18 parts polyethylene glycol diacrylate (average molecular weight 2000-3000), 18 parts acryloylmorpholine (purity 98.5%), 17 parts N-vinylcaprolactam (purity 98.2%), 13 parts polyethylene glycol monoallyl ether (average molecular weight 2000-2500), 0.3 parts glyceryl diallyl ether (purity 99.5%), 0.2 parts cumene hydrogen peroxide (purity 81.7%), 0.2 parts diethylethanolamine (purity 99.1%), and 80 parts deionized water. Step 2: Add N-methoxymethacrylamide, polyethylene glycol diacrylate, acrylmorpholine, N-vinylcaprolactam, polyethylene glycol monoallyl ether, and 90% by mass of deionized water to a sealed reactor for mixing. The mixing temperature is 45℃, the mixing speed is 130 rad / min, and the mixing time is 55 min. Step 3: Add diallyl ether, cumene hydrogen peroxide and diethylethanolamine to the remaining 10% of deionized water to dissolve them. The dissolution temperature is 35℃, the stirring speed is 130 rad / min, and the dissolution time is 180 min. Step 4: Heat the sealed reactor to 65°C, adjust the stirring speed to 230 rad / min, and introduce nitrogen gas through the air vent to begin adding the solution obtained in Step 3. The adding time is 85 min. After the adding is completed, continue the reaction for 2.3 h. Nitrogen gas is continuously introduced for protection throughout the adding and reaction process. Step 5: After the reaction is complete, a polymer suitable for high mineralization, high suspended matter, and low charge is obtained.

[0021] Verification test The polymers prepared in Examples 1-3 of this invention, suitable for high mineralization, high suspended matter, and low charge, were added to water and a 1% potassium chloride aqueous solution (the amount added was 1% of the mass of either water or the 1% potassium chloride aqueous solution) for drag reduction testing. Three sets of tests were performed, and the average value was calculated. (If the error rate between any two sets of data from the same example exceeded 5%, the test was repeated until the maximum error was less than 5%). The results are as follows: Figure 1 and Figure 2 As shown, through Figure 1 and Figure 2 The data shows that the drag reduction rate of the polymers prepared in Examples 1-3 of this invention, which are suitable for high mineralization, high suspended matter and low charge, is higher than 80% in clean water and significantly higher than 70% even in a 1% potassium chloride aqueous solution, indicating that they can maintain good drag reduction performance in a high mineralization environment. The polymers prepared in Examples 1-3 of this invention, suitable for high mineralization, high suspended matter, and low charge, were added to clean water (0.5% by mass of water) and subjected to a temperature of 25°C and a shear rate of 170 s⁻¹. -1 The apparent viscosity was tested under the following conditions. Three sets of tests were conducted and the average value was calculated (if the error rate of any two sets of data in the same embodiment exceeds 5%, the test was repeated until the maximum error is less than 5%). The average apparent viscosity of Example 1 was 54.2 mPa·s and the average tack time was 54.7 s; the average apparent viscosity of Example 2 was 55.4 mPa·s and the average tack time was 57.4 s; and the average apparent viscosity of Example 3 was 58.5 mPa·s and the average tack time was 56.3 s. This proves that the polymer prepared in Examples 1-3 of this invention, which is suitable for high mineralization, high suspended matter and low charge, still has an apparent viscosity of more than 50 mPa·s when only 0.5% dosage is added, and can complete tack within 60 s. The tack is rapid, which meets the needs of rapid preparation and immediate use of fracturing fluid in field construction. The stability of the polymers prepared in Examples 1-3 of this invention, suitable for high mineralization, high suspended matter, and low charge, was tested using the liquid standing method. The testing procedure involved adding the polymers prepared in Examples 1-3 to 10 times their mass of water, mixing thoroughly, filling the container into a bottle, sealing it, and allowing it to stand for 30 days. The changes were then observed (the change graph for Example 3 is shown in Figure 1). Figure 3 As shown in the figure, the aqueous solutions of the polymers prepared in Examples 1-3 of this invention, which are suitable for high mineralization, high suspended matter and low charge, did not undergo significant changes after standing for 30 days. This proves that the polymers prepared in Examples 1-3 of this invention, which are suitable for high mineralization, high suspended matter and low charge, have high stability in water and are not prone to stratification, precipitation and other phenomena. They are easy to store and transport and can also improve fracturing efficiency. The sand-carrying performance of the polymers prepared in Examples 1-3 of this invention, suitable for high mineralization, high suspended matter, and low charge, was tested. For static sand-carrying performance testing, 20-40 mesh ceramsite was used as the sand, with a sand ratio of 20% and a polymer solution concentration of 0.5%. The mixture was allowed to stand for 1 hour. (The testing process for Example 3 is as follows...) Figure 4As shown), three sets of tests were performed respectively, and the average value was calculated (if the error rate of any two sets of data in the same embodiment exceeds 5%, the test is repeated until the maximum error is less than 5%). The average settling velocity at room temperature in Example 1 was 0.17 mm / min, the average settling velocity at room temperature in Example 2 was 0.18 mm / min, and the average settling velocity at room temperature in Example 3 was 0.14 mm / min. From the above data, it can be seen that the polymers prepared in Examples 1-3 of the present invention, which are suitable for high mineralization, high suspended matter, and low charge, have good static sand-carrying performance. At the same time, the static sand-carrying performance was tested at a mineralization of 20000 mg / L (operation as above). The average settling velocity at room temperature in Example 1 was 0.28 mm / min, the average settling velocity at room temperature in Example 2 was 0.26 mm / min, and the average settling velocity at room temperature in Example 3 was 0.23 mm / min. From the above data, it can be seen that the polymers prepared in Examples 1-3 of the present invention, which are suitable for high mineralization, high suspended matter, and low charge, can meet the requirements for sand carrying in the re-preparation of the backflow solution. The above tests show that the polymer prepared by this invention, suitable for complex oil reservoirs with high salinity, high suspended matter, and low charge, can comprehensively exhibit excellent drag reduction performance, rapid viscosity-initiating characteristics, good apparent viscosity, high stability, and excellent sand-carrying capacity. Moreover, its low charge characteristic effectively reduces adsorption loss with formation clay minerals, effectively solving the problem of insufficient fracturing efficiency of traditional fracturing fluids under special reservoir conditions. It provides reliable technical support for fracturing stimulation of oil reservoirs with high salinity and high suspended matter, and has broad application prospects.

[0022] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A polymer suitable for high mineralization, high suspended matter, and low charge, characterized in that: The substance comprises the following components in parts by weight: 20-30 parts N-methoxymethacrylamide, 15-20 parts polyethylene glycol diacrylate, 15-20 parts acryloylmorpholine, 15-20 parts N-vinylcaprolactam, 10-15 parts polyethylene glycol monoallyl ether, 0.2-0.4 parts glycerol diallyl ether, 0.1-0.3 parts cumene hydroperoxide, 0.1-0.3 parts diethylethanolamine, and 70-90 parts deionized water.

2. The polymer suitable for high mineralization, high suspended matter, and low charge according to claim 1, characterized in that: The purity of the N-methoxymethylacrylamide is ≥95%.

3. The polymer suitable for high mineralization, high suspended matter, and low charge according to claim 1, characterized in that: The average molecular weight of the polyethylene glycol diacrylate is 2000-3000, and the average molecular weight of the polyethylene glycol monoallyl ether is 2000-2500.

4. A polymer suitable for high mineralization, high suspended matter, and low charge according to claim 1, characterized in that: The purity of the acrylomorpholine is ≥98%, and the purity of the N-vinylcaprolactam is ≥98%.

5. A polymer suitable for high mineralization, high suspended matter, and low charge according to claim 1, characterized in that: The purity of the diallyl ether is ≥99.5%.

6. A polymer suitable for high mineralization, high suspended matter, and low charge according to claim 1, characterized in that: The purity of the cumene hydrogen peroxide is ≥80%, and the purity of the diethylethanolamine is ≥99%.

7. A polymer suitable for high mineralization, high suspended matter, and low charge according to claim 1, characterized in that: Its preparation method includes the following steps: Step 1: Weigh out the following ingredients according to the specified ratio: N-methoxymethacrylamide, polyethylene glycol diacrylate, acrylomorpholine, N-vinylcaprolactam, polyethylene glycol monoallyl ether, glyceryl diallyl ether, cumene hydrogen peroxide, diethylethanolamine, and deionized water. Step 2: Add N-methoxymethacrylamide, polyethylene glycol diacrylate, acrylmorpholine, N-vinylcaprolactam, polyethylene glycol monoallyl ether, and 90% by mass of deionized water to a sealed reactor and mix. Step 3: Dissolve diallyl ether, cumene hydrogen peroxide, and diethylethanolamine in the remaining 10% by mass of deionized water; Step 4: Add the solution obtained in Step 3 dropwise at a uniform rate to the sealed reaction vessel after mixing in Step 2 to carry out the reaction; Step 5: After the reaction is complete, a polymer suitable for high mineralization, high suspended matter, and low charge is obtained.

8. A polymer suitable for high mineralization, high suspended matter, and low charge according to claim 7, characterized in that: The mixing temperature in step two is 40-50℃, the mixing speed is 100-150 rad / min, and the mixing time is 50-60 min.

9. A polymer suitable for high mineralization, high suspended matter, and low charge according to claim 7, characterized in that: The dissolution temperature in step three is 30-40℃, the stirring speed is 100-150 rad / min, and the dissolution time is 15-20 min.

10. A polymer suitable for high mineralization, high suspended matter, and low charge according to claim 7, characterized in that: In step four, the sealed reactor is heated to 60-70°C, the stirring speed is adjusted to 200-250 rad / min, and nitrogen gas is introduced through the air vent to begin adding the solution obtained in step three. The adding time is 80-90 min, and after the adding is completed, the reaction continues for 2-2.5 h. Nitrogen gas is continuously introduced for protection throughout the entire adding and reaction process.

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