CN104479660A - Composite hydrate inhibitor - Google Patents

Abstract

The invention discloses a composite hydrate inhibitor. The composite hydrate inhibitor is formed by configuring a kinetic inhibitor and ionic liquid according to the mass ratio of 1:1, wherein the kinetic inhibitor is polyvinylcaprolactam with the weight-average molecular weight of 900-40000. The hydrate inhibitor disclosed by the invention has high inhibition activity, small using amount, low cost and environmental friendliness, is easy to recover and applicable to an oil-gas-water three-phase or oil-water or gas-water two-phase coexistence system, is applied to generation of inhibition hydrates in oil-gas production, processing and conveying processes and has broad prospects.

Description

A compound hydrate inhibitor

Technical field:

The invention relates to the technical field of chemical industry, in particular to a composite hydrate inhibitor.

Background technique:

During oil and gas extraction, processing and transportation, water and some light hydrocarbons in the system are very likely to form hydrates at low temperature and high pressure in the pipeline. If no suppression measures are taken, these hydrates will block pipelines, valves and equipment, affecting normal industrial production operation, causing huge economic losses and threatening the safety of the entire production system. Therefore, how to prevent and control hydrates has become one of the key issues in the oil and gas industry, especially for the exploitation of deep-sea oil and gas fields, the problem of hydrate blockage is more prominent.

At present, the main hydrate control methods include water removal method, heating method, depressurization method and adding hydrate inhibitor method. The water removal method is costly and has great limitations, because the formation of hydrates does not absolutely require the existence of a free water phase. If the hydrate crystal nuclei or free water are adsorbed on the wall, although the water in the liquid hydrocarbon phase At very low concentrations, hydrates can also grow from the liquid hydrocarbon phase. The heating method makes the pipeline temperature higher than the hydrate formation temperature, which may easily cause pipeline rupture or even hydrate eruption, and the water produced by decomposition must be removed, otherwise hydrate will form again. The decompression method is to reduce the system pressure, which requires too high pressure control and is very difficult to apply. Therefore, the method of adding hydrate inhibitor is simple, economical and effective, and it is the most widely used method to prevent hydrate formation and blockage.

Hydrate inhibitors mainly include thermodynamic inhibitors and low-dose inhibitors. Thermodynamic inhibitors, such as methanol, ethylene glycol and other alcohols or inorganic salts, change the phase equilibrium conditions of hydrates and move the hydrate formation curve to lower temperatures or higher pressures, and the inhibitory effect is very effective. However, this method has a large amount of addition, and the general solution concentration is 10 to 60 wt%, and the corresponding storage, transportation, injection and recovery costs are high. At the same time, methanol is toxic, which is not conducive to safety and environmental protection. Low-dose inhibitors include kinetic inhibitors and polymerization inhibitors. Among them, the kinetic inhibitor is to delay the nucleation time of hydrate crystals or prevent the further growth of crystals, thereby inhibiting its formation and preventing hydrate blockage. However, the kinetic inhibitor is not very effective when the pipeline (or oil well) is closed or the subcooling degree is large (>10°C). On the other hand, kinetic inhibitors are generally water-soluble polymers. When the temperature rises, the solubility becomes poor and the inhibitory performance decreases. The polymerization inhibitor is to add some low-concentration surfactants or polymers to change the size of hydrate crystals and the form of aggregation, so that it can be transported as a slurry in the dominant fluid to achieve safe fluid transport. However, the dispersion performance of the polymerization inhibitor is limited, and it can only work when there is an oil phase, so the application occasions are limited.

Invention content:

The purpose of the present invention is to provide a novel high-efficiency composite hydrate inhibitor.

The present invention is achieved through the following technical solutions:

A composite hydrate inhibitor, which is configured by a kinetic inhibitor and an ionic liquid at a mass ratio of 1:1; the kinetic inhibitor is polyvinyl caprolactam (PVCap) with a weight-average molecular weight of 900-40,000 .

The ionic liquid is formed by combining organic cations and organic or inorganic anions in a molar ratio of 1:1 through ionic bonds.

The ionic liquid is preferably a kind of alkylguanidinium salt ionic liquid shown in formula I:

Wherein, _R1 is selected from n-butyl group, _R2 is selected from methyl group, _R3 is selected from methyl group, anion X is selected from halide ion, tetrafluoroborate, acetate, trifluoroacetate, trifluoromethanesulfonate One of.

The compound inhibitor has a low usage concentration and a small dosage, and the mass concentration relative to water is 0.05% to 0.5% when used.

The main feature of the present invention is that the added ionic liquid has dual thermodynamic and kinetic inhibition effects on hydrates, which can reduce the hydrate formation temperature or increase the hydrate formation pressure, and reduce the negative impact of supercooling on the inhibition performance of high molecular polymers; It can also inhibit the nucleation, growth and agglomeration rate of hydrates, prolong the inhibition time, and is non-toxic, non-corrosive, environmentally friendly, and will not cause corrosion to pipelines; biodegradable, and the subsequent separation and recovery process is simple; It has the characteristics of adjustable anion/cation. By adjusting its polarity and hydrophilicity/lipophilicity, the inhibitor can be applied to oil-gas-water three-phase or oil-water or gas-water two-phase coexistence system.

Compared with traditional hydrate inhibition methods, the combined hydrate inhibitor of the present invention combined with ionic liquid and kinetic inhibitor polyvinylcaprolactam has the following advantages:

(1) Higher inhibitory activity: the inhibitory effect produced by using ionic liquid alone is generally weaker than that of the kinetic inhibitor PVCap, but the single kinetic inhibitor PVCap is greatly affected by the degree of supercooling. When the degree of supercooling exceeds 10°C, the inhibition The effect will become very poor. By combining the two, the charge inhibition effect of the ions in the ionic liquid and the characteristics of the active agent itself can improve the thermodynamic environment to a certain extent and reduce the influence of the composite inhibitor on the degree of supercooling. The synergy between the two can produce a phase Better inhibitory effect than single-component inhibitors, even better than the sum of the effects of single-component inhibitors.

(2) Less dosage and lower cost: the dosage of the compound inhibitor is far less than that of the traditional thermodynamic inhibitor, the general mass concentration is about 0.05-0.5wt%, and the reagent cost is greatly reduced.

(3) Environmentally friendly and easy to recycle. The ionic liquid has good chemical stability and thermal stability, is not easy to burn, and has no corrosion, which overcomes the corrosion caused by traditional thermodynamic inhibitors to pipelines. Moreover, the ionic liquid is not volatile, has a large boiling point difference with the fluid, and is easy to recover later, which can reduce the loss of inhibitors.

In a word, the present invention is applicable to oil-gas-water three-phase or oil-water or gas-water two-phase coexistence system, and is applied to inhibit the formation of hydrate in the process of oil and gas exploitation, processing and transportation, and has broad prospects.

Detailed ways:

The following is a further description of the present invention, rather than a limitation of the present invention.

The hydrate reaction system of this embodiment mainly includes the core equipment high-pressure reactor, low-temperature constant temperature tank, vacuum pump, gas cylinder and data acquisition instrument, etc. The high-pressure reactor includes a reactor body, a magnetic stirrer, an inlet valve, a vacuum valve, a drain valve, a safety valve, and a temperature and pressure sensor. The high-pressure reaction kettle is made of stainless steel 316 material, with windows on the front and back of the kettle body, and the maximum working pressure can reach 10MPa. The low-temperature constant temperature tank provides -20-100°C refrigerant circulating fluid for the jacket of the high-pressure reactor, and the speed adjustment range of the agitator is 0-2200r/min. The temperature in the kettle is measured by a Pt100 platinum resistance temperature sensor with a temperature measurement accuracy of ±0.1°C, and the pressure is measured by a pressure sensor with an accuracy of 0.5%. Parameters such as pressure, temperature and rotational speed in the kettle can be automatically collected and stored by the data acquisition system.

The effect of the compound inhibitor of the present invention can be comprehensively judged according to the induction time of the hydrate, the complete formation time and the pressure drop. The hydrate induction time is the time elapsed from the initial value of the gas pressure to the beginning of the pressure drop. The reaction completion time is the time elapsed from the beginning of hydrate formation to the final stabilization of pressure and temperature.

The specific implementation process:

Before the experiment is run, first clean the autoclave with deionized water three to five times, and then purge the autoclave and the experimental piping system with nitrogen to ensure that the system is dry. Vacuum the high-pressure reactor, and inhale the prepared aqueous solutions of compound inhibitors of different concentrations. In order to remove the air in the autoclave, the test gas is introduced first, and then the vacuum is pumped. This is repeated 3 times, and finally the test gas less than 0.5MPa is introduced to ensure the positive pressure in the autoclave and the conditions for hydrate formation are not reached. The experiment starts with a low-temperature thermostat to cool down the high-pressure reactor until the temperature in the reactor reaches the set experimental temperature. When the temperature is stable, open the inlet valve, open the valve of the gas cylinder, and feed the experimental gas to the required pressure for the experiment. Start the magnetic stirrer and keep it at 500rmp. The pressure dropped slightly at the beginning of the experiment due to the dissolution of the gas. Hydrates are formed, and the pressure will gradually drop. At the same time, the window observation method and the temperature and pressure change curve method are used to judge whether the hydrate is formed. When the temperature and pressure remain stable for a long time, it is considered that the reaction has reached equilibrium and the formation of hydrates has completely ended. Turn off the stirrer and stop the experiment.

The reaction experiment temperature was set at 4° C., the experiment pressure was 7.5 MPa, and the experiment gas was a mixed gas (by volume fraction, methane 91.95%, ethane 5.00% and propane 3.05%).

Comparative example 1

Add 200g of pure water into the reactor, follow the above experimental procedures, the results show that under the above conditions, the induction time of hydrate formation is 35min, the reaction completion time is 1500min, and the pressure drop during the reaction is 3.5MPa.

Comparative example 2

Add 200g of PVCap aqueous solution with a mass concentration of 0.25% and a weight average molecular weight of 900 to 40,000 into the reaction kettle. The experimental procedure is the same as above. The results show that the induction time of hydrate formation under this system is 105 minutes, the reaction completion time is 3105 minutes, and the pressure drop during the reaction is 1.68 MPa, which has a good suppression effect.

Comparative example 3

Add 200g of PVCap aqueous solution with a mass concentration of 0.5% and a weight average molecular weight of 900 to 40,000 into the reaction kettle. The experimental procedure is the same as above. The results show that the induction time of hydrate formation under this system is 219 minutes, the reaction completion time is 3915 minutes, and the pressure drop during the reaction is 1.43 MPa, which has a good suppression effect.

Comparative example 4

Add 200g of N,N,N,,N,,-tetramethyl-N"-methyl-N"-butylguanidine chloride ([MBTMG]Cl) aqueous solution with a mass concentration of 0.5% into the reaction kettle. As above, the results show that the induction time of hydrate formation under this system is 155 minutes, the reaction completion time is 2508 minutes, and the pressure drop in the reaction is 1.73 MPa, which has a good inhibitory effect.

Example 1

PVCap with a weight-average molecular weight of 900-40000 and N,N,N,,N,,-tetramethyl-N"-methyl-N"-butylguanidine chloride ([MBTMG]Cl) in a mass ratio of 1 : 1 is configured into 200g of 0.05% mass concentration of the composite aqueous solution into the reactor, the experimental procedure is the same as above, the results show that the hydrate generation induction time under this system is 67min, the reaction completion time is 2219min, and the pressure drop in the reaction is 2.37MPa, which has Better suppression effect.

Example 2

PVCap with a weight-average molecular weight of 900-40000 and N,N,N,,N,,-tetramethyl-N"-methyl-N"-butylguanidine chloride ([MBTMG]Cl) in a mass ratio of 1 : 1 is configured to add 200g of 0.25% composite aqueous solution into the reaction kettle, and the experimental procedure is the same as above. The results show that the hydrate formation induction time under this system is 319min, the reaction completion time is 4327min, and the pressure drop in the reaction is 1.55MPa, which has Better suppression effect.

Example 3

PVCap with a weight average molecular weight of 900-40000 and N,N,N,,N,,-tetramethyl-N”-methyl-N”-butylguanidine chloride ([MBTMG]Cl) in a mass ratio of 1:1 Configure 200g of 0.5% composite aqueous solution into the reaction kettle, and the experimental procedure is the same as above. The results show that the induction time of hydrate formation in this system is 522min, the reaction completion time is 6950min, and the pressure drop in the reaction is 0.85MPa, which has a good performance. Inhibitory effect.

Comparing Example 3 with Comparative Examples 3 and 4, it can be seen that the combined use of kinetic inhibitor PVCap and ionic liquid can produce a better inhibitory effect than single-component inhibitors: the induction time of hydrate is prolonged, and the reaction The completion time is longer, and the pressure drop in the reaction is reduced; even, it is better than the sum of the effects of the single component inhibitors, which is due to the charge inhibition of the ions in the ionic liquid and the characteristics of the active agent itself, to a certain extent Improve the thermodynamic environment and reduce the effect of supercooling on compound inhibitors.

Example 4

PVCap with a weight average molecular weight of 900-40000 and N,N,N,,N,,-tetramethyl-N”-methyl-N”-butylguanidine tetrafluoroborate ([MBTMG]BF ₄ ) According to the mass ratio of 1:1, 200g of a composite aqueous solution with a mass concentration of 0.25% was added to the reactor. The experimental procedure was the same as above. The results showed that the induction time of hydrate formation under this system was 387 minutes, the reaction completion time was 4579 minutes, and the pressure drop during the reaction It is 1.1MPa, which has a good suppression effect.

Example 5

PVCap with a weight average molecular weight of 900-40000 and N,N,N,,N,,-tetramethyl-N"-methyl-N"-butylguanidine acetate ([MBTMG]CH ₃ COO) according to The mass ratio is 1:1, and 200g of the composite aqueous solution with a mass concentration of 0.25% is added to the reactor. The experimental procedure is the same as above. The results show that the induction time of hydrate formation under this system is 217min, the reaction completion time is 3778min, and the pressure drop during the reaction is 1.38 MPa, which has a good suppression effect.

Example 6

PVCap with a weight average molecular weight of 900-40000 and N,N,N,,N,,-tetramethyl-N”-methyl-N”-butylguanidine trifluoroacetate ([MBTMG]CF ₃ COO ) according to the mass ratio of 1:1, 200g of a composite aqueous solution with a mass concentration of 0.25% was added to the reactor, and the experimental procedures were the same as above. It is 1.32MPa, which has a good suppression effect.

Example 7

PVCap with a weight average molecular weight of 900-40000 and N,N,N,,N,,-tetramethyl-N”-methyl-N”-butylguanidine trifluoromethanesulfonate ([MBTMG]CF ₃ SO ₃ ) was configured according to the mass ratio of 1:1 to form 200g of a 0.25% composite aqueous solution and put it into the reactor. The experimental procedure was the same as above. The pressure drop is 1.25MPa, which has a good suppression effect.

Claims (4)

1. A composite hydrate inhibitor, characterized in that, it is configured by a kinetic inhibitor and an ionic liquid according to a mass ratio of 1:1; the kinetic inhibitor is a polyethylene base with a weight-average molecular weight of 900～40000 Caprolactam. 2. The composite hydrate inhibitor according to claim 1, wherein the ionic liquid is formed by combining organic cations and organic or inorganic anions with ionic bonds in a molar ratio of 1:1. 3. The complex hydrate inhibitor according to claim 1 or 2, wherein the ionic liquid is selected from one of the alkylguanidinium salt ionic liquids shown in formula I: Wherein, _R1 is selected from n-butyl group, _R2 is selected from methyl group, _R3 is selected from methyl group, anion X is selected from halide ion, tetrafluoroborate, acetate, trifluoroacetate, trifluoromethanesulfonate One of. 4. The composite hydrate inhibitor according to claim 3, characterized in that the mass concentration of the composite inhibitor relative to water is 0.05-0.5% when used.