Synergistic inhibition performance evaluation method for natural gas hydrate compound inhibitor with high CO2 content

Abstract

The invention discloses a method for evaluating the synergistic inhibition performance of a natural gas hydrate compound inhibitor with high CO2 content. The method comprises the following steps: S1, dissolving a kinetic inhibitor and a thermodynamic inhibitor in deionized water to form a homogeneous solution as a compound inhibitor; s2, testing inhibition performance; s3, observing the morphology of the hydrate crystal through a microscopic imaging technology, quantifying the growth rate and aggregation degree of the crystal in combination with an image processing algorithm, and verifying the adsorption configuration of the inhibitor and CO2 through molecular dynamics simulation; and S4, an early warning threshold value is set based on the supercooling degree threshold value and the particle size grading, an early warning signal is triggered, and the injection amount of the compound inhibitor is dynamically adjusted. According to the method, hydrate nucleation and growth are inhibited through the synergistic effect of the compound components, and quantitative analysis and early warning of the inhibition effect are achieved by combining microscopic imaging, molecular simulation and dynamic monitoring technologies.

Description

TECHNICAL FIELD

[0001] The application relates to a method for evaluating the synergistic inhibition performance of a high- CO2 natural gas hydrate complex inhibitor, and belongs to the technical field of natural gas hydrate inhibition. BACKGROUND

[0002] The core innovation of the method for optimizing and visually evaluating the synergistic inhibition performance of a high- CO2 natural gas hydrate complex inhibitor lies in solving the limitations of traditional inhibitors through multi-component synergistic mechanism and interdisciplinary evaluation technology. Traditional thermodynamic inhibitors (such as methanol and ethylene glycol) have the problems of large dosage, high toxicity and easy interference by high salinity in high- CO2 gas fields, and a single kinetic inhibitor (such as polyvinyl caprolactam) has a sharp decrease in inhibition efficiency when the supercooling degree exceeds 10 DEG C. CO2 molecules are easy to form more stable sI type crystals due to the high adaptability of the strong polarity of CO2 molecules to the cavity of the hydrate cage, further increasing the risk of pipeline blockage. Therefore, the application proposes a complex inhibitor system, which combines low-molecular-weight alcohol thermodynamic inhibitors with high-molecular-weight kinetic inhibitors, uses the thermodynamic inhibitors to reduce water activity to adjust the phase equilibrium, and at the same time, uses the circular structure of the kinetic inhibitors to embed the crystal lattice to interfere with the orderly arrangement of CO2 molecules, so that the inhibition time is extended to more than 75 hours, the supercooling degree tolerance range is expanded to 15 DEG C, the dosage of the medicament is reduced by 30%-50%, and the environmental toxicity is significantly reduced.

[0003] In the evaluation method, the traditional high-pressure experiment relies on complex equipment and cannot observe the micro mechanism in real time, while the application innovatively integrates spectral dynamic monitoring and kinetic analysis to build a multi-dimensional visual evaluation system. For example, the CO2 molecular vibration peak displacement is tracked through Raman spectroscopy, and the crystal morphology change is directly compared through microscopic imaging to realize rapid and low-cost verification of the inhibition effect. These technologies not only improve the evaluation accuracy (error rate <5%), but also provide micro mechanism support for inhibitor molecular design and theoretical basis for optimizing molecular structure. SUMMARY

[0004] The application aims to provide a method for evaluating the synergistic inhibition performance of a high- CO2 natural gas hydrate complex inhibitor to solve the flow security problem caused by crystal blockage in the transportation pipeline of high- CO2 natural gas hydrate. The method inhibits the nucleation and growth of hydrates through the synergistic effect of complex components, and realizes quantitative analysis and early warning of the inhibition effect by combining microscopic imaging, molecular simulation and dynamic monitoring technology.

[0005] The method for evaluating the synergistic inhibition performance of a high- CO2 natural gas hydrate complex inhibitor provided by the application comprises the following steps: S1, preparing a complex inhibitor The kinetic inhibitor and the thermodynamic inhibitor are dissolved in deionized water to form a homogeneous solution as a compound inhibitor; S2, inhibition performance test In the high-pressure reactor, CO2-containing natural gas is injected, the compound inhibitor is added, and the temperature, pressure, supercooling degree, induction time and hydrate particle size data are collected in real time, and the crystal nucleus formation process is recorded through a visual window; S3, visual evaluation The hydrate crystal morphology is observed by microscopic imaging technology, the crystal growth rate and aggregation degree are quantified by image processing algorithm, and the adsorption configuration of the inhibitor and CO2 is verified by molecular dynamics simulation, so that the micro-mechanism of the kinetic inhibitor and the thermodynamic inhibitor interfering with the lattice order arrangement is revealed; S4, dynamic early warning and regulation Based on the supercooling degree threshold and particle size classification, the warning threshold is set, the warning signal is triggered, and the injection amount of the compound inhibitor is dynamically adjusted; In the method, the kinetic inhibitor is luvicap EG (developed and produced by BASF Company), and the mass fraction is 0.5-2%; the thermodynamic inhibitor is ethylene glycol, and the mass fraction is 5-10%.

[0006] In the method, in step S2, the pressure resistance range of the high-pressure reactor is 0-30MPa, the temperature detection range is-10℃-30℃, the accuracy is ±0.001℃, the pressure detection range is 0-30MPa, and the accuracy is ±0.001MPa; A multi-channel temperature sensor array is used to monitor the temperature difference in the high-pressure reactor to predict the hydrate nucleation hot spot area.

[0007] In the method, in step S3, a confocal laser scanning microscope (CLSM) is used to observe the hydrate crystal morphology, NA≥1.4, the lateral resolution is ≤200 nm, the three-dimensional crystal morphology is reconstructed through Z-axis layer scanning, the dynamic changes of hydrate crystal porosity (20-50 microns) and lattice distortion can be captured, and the details are avoided. Fuzzy caused by the diffraction limit of traditional optical microscopes; The porosity, lattice distortion and particle aggregation rate are used to quantify the crystal growth rate and aggregation degree.

[0008] In the method, in step S4, the supercooling degree threshold is-15℃, and the particle size classification standard is: Safety stage: particle size <50μm; Warning stage: ≤particle size is 50-200μm; Blocking stage: particle size >200μm; The thermodynamic inhibitor is supplemented in the warning stage, and the blocking stage is combined with high-pressure pulse recoil and targeted heating to unblock.

[0009] In the method of this invention, the CO2 content in the CO2-containing natural gas is ≥30 mol.

[0010] This invention achieves a breakthrough improvement in hydrate inhibition performance through a competitive adsorption and phase equilibrium synergistic regulation mechanism of compound inhibitors. Compared with traditional methods, this invention significantly prolongs the hydrate inhibition time and greatly expands the supercooling tolerance range through synergistic effects, effectively overcoming the limitations of conventional technologies.

[0011] This invention integrates high-speed imaging and high-precision pressure sensing technologies to construct a multimodal dynamic monitoring system, significantly improving the accuracy of blockage early warning. Simultaneously, it drastically reduces the dosage of inhibitors through intelligent control strategies. In terms of environmental protection and economy, it uses low-toxicity ethylene glycol to replace the traditional methanol system, forming a green and sustainable prevention and control solution.

[0012] At the microscopic level, molecular dynamics simulations revealed the interaction patterns between inhibitor molecules and CO2, clarifying the strong adsorption configuration between key functional groups and gas molecules, thus providing theoretical support for the molecular design of high-performance inhibitors. The entire scheme, through multi-parameter synergistic optimization and intelligent response mechanisms, achieves comprehensive improvements in inhibition efficacy, monitoring and early warning, and environmental performance, combining technological advancement with engineering practicality. Attached Figure Description

[0013] Figure 1 This is a flowchart of the visual evaluation method for compound inhibitors of the present invention. Detailed Implementation

[0014] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0015] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0016] Figure 1 The flowchart of the method for visual evaluation of compound inhibitors of the present invention includes the following steps: Step S1: In the preparation of the compound inhibitor, the mass ratio of kinetic inhibitor (such as luvicap EG) to thermodynamic inhibitor (such as ethylene glycol) is optimized (typically 0.1%-2% kinetic inhibitor to ≤10% thermodynamic inhibitor), and a homogeneous solution is formed by stirring in deionized water. In the preferred embodiment, luvicap EG is used, whose seven-membered ring structure has a high degree of matching with the cage-like cavity of Si-type hydrates, significantly improving the inhibition efficiency.

[0017] In step S2, natural gas containing 30% CO2 was injected into a high-pressure reactor with a pressure resistance of 20 MPa. After adding a compound inhibitor, parameters such as temperature (-5-15℃), pressure (5-15 MPa), supercooling (ΔT), induction time, and hydrate particle size were collected in real time through a sapphire window. Simultaneously, a high-speed camera recorded the crystal nucleation process. Combined with dynamic data from pressure and temperature sensors, a correlation model was constructed between the hydrate formation rate and the inhibitor concentration and temperature gradient. A multi-channel temperature sensor array was installed in the experimental setup to accurately monitor temperature differences in different sections of the pipeline (accuracy ±0.001℃), providing basic data for subsequent early warning models.

[0018] Step S3 involves real-time observation of the morphological characteristics of hydrate crystals in a high-CO2-content natural gas system, including porosity and lattice distortion, using an optical microscope. Image processing algorithms are then used to quantify the crystal growth rate and aggregation degree (e.g., particle aggregation rate). Molecular dynamics simulations reveal that kinetic inhibitors suppress nucleus growth through competitive adsorption, while thermodynamic inhibitors disrupt the synergistic mechanism of ordered lattice arrangement by disrupting the hydrogen bond network of water molecules.

[0019] Step S4: Based on the supercooling tolerance threshold (ΔT≥15℃) and particle size classification (safe stage <50 μm, warning stage 50-200 μm, blockage stage >200 μm), a real-time warning threshold is set. When the monitoring data approaches the critical value, the system automatically triggers a warning signal and dynamically adjusts the inhibitor injection amount (error rate <5%). In the warning stage, a thermodynamic inhibitor (such as ethylene glycol) replenishment program is initiated to inhibit hydrate formation; if the blockage stage is entered, high-pressure pulse backflushing (ΔP=2-5MPa) and targeted heating (local temperature rise of 2-3℃) are combined to achieve unblocking.

[0020] Example 1 By weight, 1000 parts of deionized water were placed in a high-pressure reactor. The water bath was set to 8°C. Once the temperature inside the reactor reached 8°C, natural gas was injected into the high-pressure reactor. After the pressure inside the reactor reached 8 MPa and stabilized, the gas injection was stopped, and the stirring speed of the stirrer was adjusted to 250 rpm. The reaction was considered complete when the pressure reading from the pressure sensor decreased and then stabilized again.

[0021] Example 2 By weight, 899 parts deionized water, 100 parts ethylene glycol, and 1 part Luvicap EG were placed in a high-pressure reactor. The water bath was set to 8°C. Once the temperature inside the reactor reached 8°C, natural gas was injected into the high-pressure reactor. After the pressure inside the reactor reached 8 MPa and stabilized, the gas injection was stopped, and the stirring speed of the stirrer was adjusted to 250 rpm. The reaction was considered complete when the pressure reading on the pressure sensor decreased and then stabilized again.

[0022] Example 3 By weight, 849 parts deionized water, 100 parts ethylene glycol, and 2 parts Luvicap EG were placed in a high-pressure reactor. The water bath was set to 8°C. Once the temperature inside the reactor reached 8°C, natural gas was injected into the high-pressure reactor. After the pressure inside the reactor reached 8 MPa and stabilized, the gas injection was stopped, and the stirring speed of the stirrer was adjusted to 250 rpm. The reaction was considered complete when the pressure reading on the pressure sensor decreased and then stabilized again.

[0023] Example 4 By weight, 849 parts deionized water, 150 parts ethylene glycol, and 1 part Luvicap EG were placed in a high-pressure reactor. The water bath was set to 8°C. Once the temperature inside the reactor reached 8°C, natural gas was injected into the high-pressure reactor. After the pressure inside the reactor reached 8 MPa and stabilized, the gas injection was stopped, and the stirring speed of the stirrer was adjusted to 250 rpm. The reaction was considered complete when the pressure reading on the pressure sensor decreased and then stabilized again.

[0024] Example 5 By weight, 848 parts deionized water, 150 parts ethylene glycol, and 2 parts Luvicap EG were placed in a high-pressure reactor. The water bath was set to 8°C. Once the temperature inside the reactor reached 8°C, natural gas was injected into the high-pressure reactor. After the pressure inside the reactor reached 8 MPa and stabilized, the gas injection was stopped, and the stirring speed of the stirrer was adjusted to 250 rpm. The reaction was considered complete when the pressure reading on the pressure sensor decreased and then stabilized again.

[0025] The composition of the natural gas used is shown in Table 1.

[0026] Table 1 Natural gas composition used in the examples

[0027] The gas consumption can be calculated using the following general formula.

[0028] In the formula: P0 and T0 are the pressure and temperature inside the high-pressure reactor when the gas injection is completed; P1 and T1 are the pressure and temperature inside the high-pressure reactor during the reaction, with units of MPa and K, respectively; V is the effective gas volume inside the high-pressure reactor (ignoring the volume change during the reaction process), with units of ml; R is the universal gas constant, taken as R = 8.314 J / (mol·K); the compressibility coefficient Z is calculated by the PR equation of state; Z1 and Z2 represent the compressibility coefficients of the gas inside the reactor at the beginning and end of the reaction, respectively.

[0029] Table 2 Comparison of induction time and gas consumption of compound inhibitors

[0030] In Example 1, particle size detection and observation were carried out simultaneously to track the crystal growth process in real time. The particle size classification experiment results showed a clear correlation between hydrate crystal size and blockage risk. In the experiment, the crystal growth process was tracked in real time using an online particle monitoring system (using the principle of laser diffraction). It was found that: crystals smaller than 50 μm flowed with the liquid flow and produced almost no deposition effect; crystals between 50 and 200 μm began to show slight deposition, but had not yet formed stable blockage; crystals larger than 200 μm deposited rapidly, leading to a sharp increase in flow resistance.

[0031] Table 3. Blockage risk assessment for different particle size ranges

[0032] Example 6 By weight, 1000 parts of deionized water were placed in a high-pressure reactor. The water bath was adjusted to 8°C. Once the temperature inside the reactor reached 8°C, natural gas was injected into the high-pressure reactor. After the pressure inside the reactor reached 8 MPa and stabilized, the gas injection was stopped, and the stirring speed of the stirrer was adjusted to 250 rpm. The process continued until the pressure reading from the pressure sensor decreased and then stabilized again. A certain amount of gas was then released from the high-pressure reactor to reduce the pressure inside to 1 MPa, until the hydrates inside the reactor were completely decomposed.

[0033] Example 7 By weight, 1000 parts of deionized water were placed in a high-pressure reactor. The water bath was set to 8°C. Once the reactor temperature reached 8°C, natural gas was injected into the reactor. After the pressure inside the reactor reached 8 MPa and stabilized, the gas injection was stopped, and the stirring speed of the agitator was adjusted to 250 rpm. The process continued until the pressure reading from the pressure sensor decreased and then stabilized again. The water bath temperature was then adjusted to 20°C until the hydrates inside the high-pressure reactor were completely decomposed.

[0034] Example 8 By weight, 1000 parts of deionized water were placed in a high-pressure reactor. The water bath was adjusted to 8°C. Once the reactor temperature reached 8°C, natural gas was injected into the reactor. After the pressure inside the reactor reached 8 MPa and stabilized, the gas injection was stopped, and the stirring speed of the stirrer was adjusted to 250 rpm. The process continued until the pressure reading from the pressure sensor decreased and then stabilized again. A certain amount of gas was then released from the reactor to reduce the pressure to 4 MPa. The water bath was then adjusted to 15°C until the hydrates inside the reactor were completely decomposed.

[0035] Table 4. Congestion Relief Time for Different Relief Strategies

[0036] Time to clear congestion T 解堵 The time elapsed from the completion of the depressurization or heating operation to the complete decomposition of hydrates in the reactor.

Claims

1. A method for evaluating the synergistic inhibitory performance of a compound inhibitor of high CO2-content natural gas hydrate, comprising the following steps: S1. Preparation of compound inhibitors A homogeneous solution of kinetic and thermodynamic inhibitors was formed by dissolving them in deionized water, which was then used as a compound inhibitor. S2, Suppression Performance Test CO2-containing natural gas was injected into a high-pressure reactor, and a compound inhibitor was added. Data on temperature, pressure, supercooling, induction time, and hydrate particle size were collected in real time, and the crystal nucleation process was recorded through a viewing window. S3, Visual Evaluation The morphology of hydrate crystals was observed using microscopic imaging techniques, and the crystal growth rate and aggregation degree were quantified by combining image processing algorithms. The adsorption configuration of inhibitors and CO2 was verified by molecular dynamics simulation. S4. Dynamic Early Warning and Control The warning threshold is set based on the supercooling threshold and particle size classification, triggering the warning signal and dynamically adjusting the injection amount of the compound inhibitor.

2. The method according to claim 1, characterized in that: The kinetic inhibitor is polyvinylcaprolactam with a mass fraction of 0.5-2%; the thermodynamic inhibitor is ethylene glycol with a mass fraction of 5-10%.

3. The method according to claim 1 or 2, characterized in that: In step S2, the pressure resistance range of the high-pressure reactor is 0-30MPa, the temperature detection range is -10℃-30℃, and the pressure detection range is 0-30MPa. A multi-channel temperature sensor array is used to monitor the temperature difference inside the high-pressure reactor to predict the hot spots for hydrate nucleation.

4. The method according to claim 1 or 2, characterized in that: In step S3, the morphology of the hydrate crystals is observed using a confocal laser scanning microscope with a lateral resolution of ≤200 nm, and the three-dimensional crystal morphology is reconstructed by Z-axis tomography. The crystal growth rate and aggregation degree are quantified by porosity, lattice distortion and particle aggregation rate.

5. The method according to claim 1 or 2, characterized in that: In step S4, the supercooling threshold is -15℃, and the particle size grading standard is: Safety stage: Particle size <50μm; Early warning stage: Particle size ≤ 50-200μm; Blockage stage: Particle size > 200 μm; The warning phase triggers the injection of the thermodynamic inhibitor, and the blockage phase combines high-pressure pulse backflush with targeted heating to unblock the blockage.

6. The method according to claim 1 or 2, characterized in that: The CO2 content in the CO2-containing natural gas is ≥30 mol.

7. A visual evaluation system for implementing the method of any one of claims 1-6, comprising: The high-pressure reactor integrates a sapphire viewing window and a high-speed camera module. Multispectral dynamic monitoring module; The intelligent early warning module dynamically adjusts the amount of inhibitor injected based on real-time data.

8. A computer-readable storage medium storing program instructions, characterized in that: When the program instructions are executed by the processor, they implement the steps of the method according to any one of claims 1-6.

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