A polyethylene-vinyl acetate and microsphere composite hydrate inhibitor and its application

Abstract

The present invention discloses a polyethylene-vinyl acetate and microsphere composite hydrate inhibitor and its application. A composite hydrate inhibitor is composed of polyethylene-vinyl acetate and polymethylsilsesquioxane microspheres. The composite hydrate inhibitor proposed by the present invention comprises PMSQ microspheres as a component with strong thermal stability, high biosafety, simple synthesis and controllable particle size; the composite formed by mixing EVA and PMSQ microspheres can not only effectively reduce the wax precipitation temperature of wax oil and improve crude oil fluidity, but also inhibit hydrate nucleation and particle aggregation in waxy oil-water systems, and has the dual effects of de-pour point and hydrate inhibition; compared with the single effects of EVA and PMSQ microspheres, the composite of the two has a better de-pour point effect, enhances the nucleation inhibition performance of hydrates, and has a better anti-aggregation effect, making the application occasions more extensive.

Description

Technical field:

[0001] The present invention relates to the technical field of hydrate formation prevention and control, and in particular to a polyethylene-vinyl acetate and microsphere composite hydrate inhibitor and application thereof. Background technology:

[0002] Global energy demand continues to increase, and traditional fossil energy will remain the main source of energy for the next 30 years. With the continuous advancement of oil extraction technology and the near exhaustion of onshore fossil energy consumption, the development of oil and gas resources has gradually shifted from land to the deep sea. However, the low temperature and high pressure environment and the flow shear in multiphase fluids during deep-sea oil and gas pipeline transportation provide sufficient supercooling and mass transfer conditions for hydrates, which easily lead to the formation and aggregation of hydrates. The formation and aggregation of hydrates in pipelines will reduce production efficiency and threaten production safety. In severe cases, it will block the pipeline and cause production to stop, causing serious environmental damage and economic losses. Therefore, preventing and controlling the formation and aggregation of hydrates in pipelines has always been an important issue that has received much attention in the flow assurance of deep-sea oil and gas transportation.

[0003] Conventional methods for preventing hydrate deposition include physical methods such as water removal, heating, and pressure reduction. These methods can curb hydrate formation at the source, but they are difficult to implement and can significantly reduce production efficiency. Adding chemical inhibitors is a method currently receiving extensive research.

[0004] Chemical inhibitors mainly include thermodynamic inhibitors, kinetic inhibitors and polymerization inhibitors. Thermodynamic inhibitors change the equilibrium curve of hydrate formation, making it difficult for hydrates to form. However, the dosage is large, up to 20-60wt% (based on the water phase), and they are highly toxic. Kinetic inhibitors affect the nucleation and formation of hydrates by inhibiting hydrate nucleation or hindering crystal growth. Although the dosage is low, they also have a high supercooling (△T sub The drawback of polymerization inhibitors is that their inhibitory effects fail at temperatures above 10K. Inhibitors prevent the aggregation of hydrate particles within the system, dispersing them in the liquid hydrocarbon phase, thereby enabling continuous delivery of a stable hydrate slurry. These inhibitors require minimal dosage and are suitable for oil-water systems, maintaining excellent performance even at high supercooling temperatures. However, most common AAs are traditional surfactants, which are expensive to synthesize, difficult to recycle, and pose significant environmental risks.

[0005] Furthermore, changes in temperature and pressure can cause some of the wax in waxy crude oil to precipitate from the oil phase due to a decrease in solubility, resulting in poorer flow properties. If wax deposition and hydrate formation occur simultaneously, the risk of pipeline blockage is likely to increase. Therefore, to mitigate the flow safety risks associated with the complex coexistence of solid phases during deepwater oil and gas transportation, research on efficient additives for waxy hydrate systems is urgently needed.

[0006] In recent years, researchers have proposed that adding a combination of polymerization inhibitors and pour point depressants to a waxy oil-water system can simultaneously change the morphology of wax crystal precipitation and inhibit the nucleation of hydrates. Currently, one of the most commonly used methods to improve wax deposition is to add a pour point depressant (PPD). Traditional polymer pour point depressants can be mainly divided into two types: linear polyethylene-vinyl acetate (EVA) and comb-type polymethacrylate (POA). They have good performance in improving crude oil fluidity, but have shortcomings such as poor shear resistance and easy failure. New pour point depressants are mainly composite pour point depressants. By combining traditional pour point depressants with solid particles, the purpose of improving the stability and recyclability of the pour point depressants is achieved. Summary of the invention:

[0007] In order to overcome the above-mentioned problems existing in the prior art, the present invention provides a polyethylene-vinyl acetate and microsphere composite hydrate inhibitor and its application. The solid particulate hydrate inhibitor proposed in the present invention is non-toxic, has high biosafety, is simple to synthesize, has controllable particle size, can inhibit hydrate nucleation and effectively prevent hydrate aggregation.

[0008] The first object of the present invention is to provide a polyethylene-vinyl acetate and microsphere composite hydrate inhibitor, which is composed of polyethylene-vinyl acetate (EVA) and polymethylsilsesquioxane microspheres (PMSQ), and the mass ratio of the polyethylene-vinyl acetate and polymethylsilsesquioxane microspheres is 0.5-2:1.

[0009] Preferably, the mass ratio of the polyethylene vinyl acetate (EVA) to the polymethylsilsesquioxane microspheres (PMSQ) is 1:1.

[0010] In actual use, polyethylene-vinyl acetate and polymethylsilsesquioxane microspheres are mixed evenly.

[0011] Preferably, the polymethylsilsesquioxane microspheres are prepared by the following steps: adding methyltrimethoxysilane (MTMS) dropwise into water and stirring to completely dissolve it to obtain a methyltrimethoxysilane aqueous solution; then adding ammonia water dropwise, allowing the mixture to react for 2-4 hours, and centrifuging the mixture to obtain a sediment, which is then washed and dried to obtain white powdery polymethylsilsesquioxane microspheres.

[0012] PMSQ is produced by hydrolysis and condensation of methyltrimethoxysilane (MTMS), and its particle size distribution is around 1 μm.

[0013] The specific reaction process equation of PMSQ is shown in the following formula 1:

[0014]

[0015] Preferably, the concentration of methyltrimethoxysilane in the methyltrimethoxysilane aqueous solution is 4-6 vol%; the volume ratio of ammonia water to the total reaction solution is 0.001-0.003:1, and the reaction is allowed to stand for 3 hours.

[0016] More preferably, the concentration of methyltrimethoxysilane in the methyltrimethoxysilane aqueous solution is 5 vol%; and the volume ratio of ammonia water to the total reaction solution is 0.002:1.

[0017] The second object of the present invention is to provide the application of the polyethylene-vinyl acetate and microsphere composite hydrate inhibitor.

[0018] Preferably, the composite hydrate inhibitor is used to inhibit the formation and aggregation of hydrates in a waxy oil-water system.

[0019] The waxy oil-water system is prepared by the following steps:

[0020] (1) First, add oil into the container, then add wax and microsphere composite hydrate inhibitor into the container, maintain the container temperature at 50°C-70°C, so that the wax is completely dissolved, and stir the mixture during the reaction to ensure uniform mixing;

[0021] (2) After the mixture is evenly mixed, continue stirring and store for 0.5-1 hour;

[0022] (3) Add deionized water according to the water content requirement and stir evenly to obtain a wax-containing oil-water system.

[0023] More preferably, when the composite hydrate inhibitor is used, the mass ratio of the wax to the oil phase is 1:100 to 5:100, the applicable pressure is 1 to 25 MPa, and the temperature is -25°C to 25°C.

[0024] More preferably, the total volume ratio of water to oil and water in the wax-containing oil-water system is 0.1 to 0.5:1.

[0025] More preferably, the composite hydrate inhibitor in the waxy oil-water system accounts for 0.02 to 0.1 wt% of the oil mass.

[0026] The third object of the present invention is to provide the application of the polyethylene-vinyl acetate and microsphere composite hydrate inhibitor in the prevention and control of hydrate formation in wax-containing oil-water systems.

[0027] Compared with the existing technology, the present invention has the following advantages: compared with the current traditional polymerization inhibitors, the composite hydrate inhibitor proposed by the present invention has a component PMSQ microsphere with strong thermal stability, high biosafety, simple synthesis, and controllable particle size; the composite formed by mixing EVA and PMSQ microspheres can not only effectively reduce the wax precipitation temperature of wax oil and improve crude oil fluidity, but also inhibit hydrate nucleation and particle aggregation in waxy oil-water systems, and has the dual effects of depressing the pour point and inhibiting hydrates; compared with the single effects of EVA and PMSQ microspheres, the composite of the two has a better depressing effect, enhances the hydrate nucleation inhibition performance, and has a better anti-aggregation effect, making it more widely applicable. Description of the drawings:

[0028] Figure 1 This is a TEM image of the PMSQ particles synthesized in Example 1.

[0029] Figure 2 This is the EDS graph of the PMSQ particles synthesized in Example 1.

[0030] Figure 3 This is the IR graph of the PMSQ microparticles synthesized in Example 1.

[0031] Figure 4 This is the curve of temperature, pressure and torque changing with time during the formation of methane hydrate in a waxy oil-water system under the action of single 0.02wt% PMSQ, EVA and EVA / PMSQ (mass ratio 1:1) composite under the conditions of water content 30vol% and wax content 5wt%.

[0032] Figure 5 This is the curve of temperature, pressure and torque changing with time during the formation of methane hydrate in a waxy oil-water system under the action of single 0.05wt% PMSQ, EVA and EVA / PMSQ (mass ratio 1:1) composite under the conditions of water content 30vol% and wax content 5wt%. Specific implementation method:

[0033] The following examples are provided to further illustrate the present invention, but are not intended to limit the present invention.

[0034] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the experimental materials and reagents herein are conventional commercial products in the art.

[0035] The testing equipment is a visual high-pressure stirring experimental device, whose main components include a dual-view mirror high-pressure reactor, a low-temperature thermostat, temperature and pressure sensors, a torque sensor, and a data acquisition device. The high-pressure reactor has a maximum operating pressure of 25 MPa and an operating temperature range of -25°C to 60°C. The pressure inside the high-pressure reactor can be freely adjusted using a manual piston-type booster valve, and the maximum pressure of the pump is 30 MPa. The low-temperature thermostat can provide a refrigerant circulating fluid at a temperature of -25°C to 60°C for the high-pressure reactor jacket. The data acquisition system collects the temperature, pressure, and torque inside the reactor in real time. Hydrate formation and aggregation can be comprehensively judged by the changes in temperature, pressure, and torque during the reaction, as well as by observation through the transparent window.

[0036] Specific testing process:

[0037] Preparation of wax-containing water-oil system:

[0038] (1) First, add 100 mL of mineral oil into a 250 mL beaker, add a certain amount of wax (for example, the mass ratio of wax to oil phase is 5:100, that is, the wax content is 5 wt%) into the mineral oil, and keep it at 60 ° C (higher than the wax precipitation temperature WAT) to completely dissolve the wax.

[0039] (2) Continue stirring at high speed for 1 hour to allow the wax and oil to be completely mixed.

[0040] (3) Add a certain amount of deionized water (according to the water content requirement), stir for 5 minutes, and then transfer 150 mL of wax oil water into the reactor to start the test process.

[0041] The phase equilibrium temperature for methane hydrate formation at 9.0 MPa is approximately 11.9°C. Before the experiment, the reactor was repeatedly rinsed with deionized water, and the pipeline system was purged with nitrogen. Then, at an initial temperature of 35°C, the reactor was evacuated to eliminate the influence of air. High-purity methane gas was slowly injected to 9.0 MPa. Considering that the gas dissolves in the oil phase, repeated gas injection was performed until the oil, water, and gas phases reached equilibrium and stabilized at 35°C and 9 MPa. Stirring was then initiated at 400 rpm, and the temperature was lowered to the target experimental temperature of 3°C to induce hydrate formation. During the cooling process, the pressure decreased linearly with temperature, gradually entering the hydrate phase equilibrium region from the non-hydrate region. Under a certain temperature driving force, initial hydrate nuclei appeared, resulting in a sharp drop in pressure. Due to the exothermic reaction, the temperature in the system rose sharply, and the corresponding torque also increased. As the reaction continued, methane gas was continuously consumed, entering the hydrate solid phase from the gas-liquid phase. The hydrate formation experiment was considered complete when the system temperature stabilized and the pressure dropped by less than 0.01 MPa within 30 minutes. The hydrate induction time was defined as the time from reaching the phase equilibrium temperature and pressure (Te = 11.3°C and Pe = 7.94 MPa) to the appearance of initial hydrate nuclei, resulting in a sudden drop in pressure or a sudden increase in temperature.

[0042] Example 1

[0043] PMSQ microspheres were prepared by the following steps: MTMS with a volume concentration of 5 vol% (based on the obtained MTMS aqueous solution) was added dropwise into deionized water and stirred at a constant speed of 300 rpm for 3 hours to completely hydrolyze it; then the stirring was paused, 200 μL / 100 mL (based on the total reaction liquid volume) of ammonia water was added dropwise, and the reaction was allowed to stand for 3 hours; finally, the sediment in the mixed solution was filtered out using a high-speed centrifuge at a speed of 8000 rpm for 5 minutes, washed with anhydrous ethanol, and vacuum dried at 80°C to obtain white powdery PMSQ microspheres.

[0044] The obtained PMSQ microspheres were tested by TEM electron microscope. Figure 1 As shown by Figure 1 It can be seen that the particle size distribution is relatively uniform, with an average particle size of 1 μm. Figure 2 As can be seen from Table 1, the microparticles contain three elements: Si, O, and C, and the three elements are evenly distributed in the microspheres.

[0045] Table 1

[0046]

[0047] Depend on Figure 3 It can be seen that (1) at a wave number of 3400 cm -1 The broad peaks appearing on the left and right are the stretching vibration peaks of -OH in the hydrogen bond association state, proving that the microspheres are hydrophilic; (2) at the wave number of 3000-2700cm -1 The four small peaks appearing at 1270 cm-1 are the stretching vibration absorption peaks of saturated methyl CH. -1 The medium-intensity peak at 1030 cm is the symmetrical deformation vibration peak of the saturated methyl CH on the Si, which indicates the hydrophobicity of the microspheres; (3) -1 and 1110cm -1 The strong broad peaks appearing near the antisymmetric stretching vibration peak of Si-O-Si are at 797-769 cm -1 The sharp peak at 4° is the Si-C stretching vibration absorption peak, which is consistent with the target product. The FTIR spectrum proves that the PMSQ microspheres were successfully synthesized and have amphiphilic properties.

[0048] Example 2

[0049] The same as Example 1, except that: the concentration of methyltrimethoxysilane in the methyltrimethoxysilane aqueous solution is 4 vol%; the volume ratio of ammonia water to the total reaction solution is 0.001:1, and the reaction is allowed to stand for 2 hours.

[0050] Example 3

[0051] The same as Example 1, except that: the concentration of methyltrimethoxysilane in the methyltrimethoxysilane aqueous solution is 6 vol%; the volume ratio of ammonia water to the total reaction solution is 0.003:1, and the reaction is allowed to stand for 4 hours.

[0052] The following examples and comparative examples were tested using the PMSQ prepared in Example 1:

[0053] Example 4

[0054] EVA / PMSQ composites of varying concentrations (0.1 wt%, 0.05 wt%, and 0.02 wt%) were added during step (1) of the preparation process for the wax-water-oil system. The mass ratio of EVA to PMSQ in the EVA / PMSQ composites was 1:1, resulting in a wax + EVA / PMSQ wax-water-oil system. The system was then added to the autoclave described above, and the induction time for hydrate formation and the maximum torque during hydrate formation were measured under a water content of 30 vol%. The experimental procedures were the same as above, and the experimental results are shown in Table 1.

[0055] The specific steps of adding PMSQ in step (1) during the preparation of the wax-containing water-oil system are as follows: (1) first add 100 mL of mineral oil into a 250 mL beaker, add wax (the mass ratio of wax to oil phase is 5:100, that is, the wax content is 5 wt%) and a certain concentration (0.1 wt%, 0.05 wt%, 0.02 wt%) of EVA / PMSQ into the mineral oil, and heat to 60 ° C to completely dissolve the wax.

[0056] Example 5

[0057] A certain concentration (0.02 wt%) of polyethylene-vinyl acetate (EVA) was added in step (1) (same as the addition step in Example 4), with a mass ratio of EVA to PMSQ of 2:1 in the EVA / PMSQ composite. A 5 wt% wax + EVA / PMSQ wax-water system was prepared. The induction time for hydrate formation and the maximum torque during hydrate formation were measured at a water content of 30 vol%. The experimental procedures were the same as above, and the experimental results are shown in Table 1.

[0058] Example 6

[0059] A certain concentration (0.02 wt%) of polyethylene-vinyl acetate (EVA) was added in step (1) (same as the addition step in Example 4), with a mass ratio of EVA to PMSQ of 1:2 in the EVA / PMSQ composite. A 5 wt% wax + EVA / PMSQ wax-water system was prepared. The induction time for hydrate formation and the maximum torque during hydrate formation were measured at a water content of 30 vol%. The experimental procedures were the same as above, and the experimental results are shown in Table 1.

[0060] Blank example 1

[0061] A 5 wt% wax-containing oil-water system without polymerization inhibitor was added to the autoclave, and the induction time and maximum torque of hydrate formation at a water content of 30 vol% were measured. The experimental procedures were the same as above, and the experimental results are shown in Table 1.

[0062] Comparative Example 1

[0063] Polyethylene vinyl acetate (EVA) at various concentrations (0.1 wt%, 0.05 wt%, and 0.02 wt%) was added during step (1) (same as the addition step in Example 4) to prepare a 5 wt% wax + EVA wax-water system. The induction time for hydrate formation and the maximum torque during hydrate formation were measured at a water content of 30 vol%. The experimental procedures were the same as above, and the experimental results are shown in Table 1.

[0064] Comparative Example 2

[0065] PMSQ at various concentrations (0.1 wt%, 0.05 wt%, and 0.02 wt%) was added during step (1) (same as the addition procedure in Example 4) to prepare a 5 wt% wax + PMSQ waxy oil-water system. The induction time for hydrate formation and the maximum torque during hydrate formation were measured at a water content of 30 vol%. The experimental procedures were the same as above, and the experimental results are shown in Table 2.

[0066] Table 2

[0067]

[0068] Depend on Figure 4 and Figure 5 It can be seen that the addition of a composite hydrate inhibitor can not only prolong the hydrate induction time but also prevent hydrate aggregation, but has no significant effect on the amount of hydrate formed. When a 0.02wt% concentration of EVA / PMSQ (mass ratio 1:1) composite hydrate inhibitor is added, the inhibition effect is the best, with the maximum torque decreasing from 6.18N·cm to 3.46N·cm. At a concentration of 0.05wt%, the inhibitory effect on hydrate nucleation is most pronounced, with the composite additive's induction time reaching 611 minutes. However, at a concentration of 0.1wt%, the effects of both hydrate nucleation inhibition and particle inhibition are weakened. This indicates that the applicable range of this composite hydrate inhibitor is 0.02-0.1wt%, and there is an optimal concentration, allowing the addition amount to be selected according to needs.

[0069] As shown in Table 2, by comparing Examples 4, 5, and 6 with Comparative Examples 1-2, it can be seen that under the same moisture and wax content conditions, the addition of the traditional pour point depressant EVA alone can effectively inhibit polymerization, significantly reducing the maximum torque during hydrate formation. However, the addition of microspheres PMSQ can effectively inhibit hydrate nucleation and prevent hydrate crystal aggregation to a certain extent. Furthermore, the combination of EVA and microspheres PMSQ, especially at the same dosage, can achieve even better results in inhibiting hydrate nucleation and preventing hydrate aggregation than the addition of EVA or PMSQ alone.

[0070] The description of the above embodiments is only used to help understand the technical solution and core ideas of the present invention. It should be pointed out that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention. These improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. Application of polyethylene-vinyl acetate and microsphere composite hydrate inhibitor, characterized in that: The composite hydrate inhibitor is used to inhibit the formation and aggregation of hydrates in a wax-containing oil-water system; the composite hydrate inhibitor is composed of polyethylene-vinyl acetate and polymethylsilsesquioxane microspheres, and the mass ratio of the polyethylene-vinyl acetate to the polymethylsilsesquioxane microspheres is 0.5-2:

1.

2. The use according to claim 1, characterized in that The mass ratio of the polyethylene-vinyl acetate and polymethylsilsesquioxane microspheres is 1:

1.

3. The use according to claim 1 or 2, characterized in that The polymethylsilsesquioxane microspheres are prepared by the following steps: adding methyltrimethoxysilane dropwise to water and stirring to completely dissolve it to obtain a methyltrimethoxysilane aqueous solution; then adding ammonia water dropwise, allowing the mixture to react for 2-4 hours, and centrifuging the mixture to obtain a sediment. After washing and drying, white powdery polymethylsilsesquioxane microspheres are obtained.

4. The use according to claim 3, characterized in that The concentration of methyltrimethoxysilane in the methyltrimethoxysilane aqueous solution is 4-6 vol%; and the volume ratio of ammonia water to the total reaction solution is 0.001-0.003:

1.

5. The use according to claim 1, characterized in that When the composite hydrate inhibitor is used, the mass ratio of the wax to the oil phase is 1:100-5:100, the applicable pressure is 1-25 MPa, and the temperature is -25°C-25°C.

6. The use according to claim 1, characterized in that The total volume ratio of water to oil and water in the wax-containing oil-water system is 0.1-0.5:

1.

7. The use according to claim 1, characterized in that The composite hydrate inhibitor in the waxy oil-water system accounts for 0.02-0.1 wt% of the oil mass.

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