A highly effective treatment agent for hydrate flow obstruction in wellbore

Abstract

The present invention provides a highly efficient treatment agent for hydrate flow obstruction in a wellbore, which is composed of a modified inhibitor, an amino acid, and an alcohol. The three substances in the inhibitor synergistically inhibit the formation of natural gas hydrates, and have a significant inhibitory effect on the formation of natural gas hydrates; at the same time, the dosage of these substances is low, and will not cause damage to the environment, which is green and environmentally friendly, and has a wide range of application prospects in natural gas mining and transportation.

Description

Technical Field

[0001] The invention relates to the technical field of chemical engineering, and in particular to a highly efficient treatment agent for hydrate flow obstruction in a wellbore. Background Art

[0002] Natural gas hydrate inhibitors are chemical substances that inhibit the formation of hydrates during the extraction, transportation and processing of natural gas. Natural gas hydrate inhibitors mainly include thermodynamic inhibitors and kinetic inhibitors.

[0003] Thermodynamic gas hydrate inhibitors can change the thermodynamic equilibrium conditions between water and gas molecules, destroy the structural relationship between water molecules with holes, change the interaction energy between them, thereby reducing the vapor pressure of the interface, greatly reducing the crystallization point of the generated hydrate, and achieving the purpose of inhibiting the formation of gas hydrates. Thermodynamic inhibitors are currently the most commonly used hydrate inhibitors at home and abroad. Widely used thermodynamic inhibitors can be divided into two categories: organic inhibitors and inorganic inhibitors; organic inhibitors include compounds such as methanol; inorganic inhibitors include sodium chloride, calcium chloride and potassium chloride. However, this type of inhibitor is toxic, requires a large amount of reagents, is not easy to degrade, and is easy to cause harm to the environment. In addition, due to its large usage, the cost is too high.

[0004] Kinetic gas hydrate inhibitors do not affect the thermodynamic conditions for hydrate formation, but can reduce the nucleation rate of hydrates and prolong the nucleation time of hydrates, thereby delaying the time for hydrates to enter the rapid growth phase. Currently developed kinetic inhibitors mainly include: (1) amide polymers, (2) ketone polymers, (3) imine polymers, (4) diamine polymers, (5) organic salts, and (6) copolymers. The characteristics of this type of inhibitor are that the amount added is small and will not affect the thermodynamic conditions for hydrate formation; however, its inhibitory effect is limited.

[0005] Compared with traditional thermodynamic inhibitors and kinetic inhibitors, green inhibitors developed in recent years are easy to degrade and less destructive to the environment. Such inhibitors mainly include amino acids, ionic liquids, antifreeze proteins or antifreeze glycoproteins, and some natural polymers, such as hydroxycellulose, starch, chitosan, pectin, etc. This type of new natural inhibitor is still in the early stages of development, and its inhibitory performance on the formation of natural gas hydrates is poor and needs to be further improved.

[0006] Since a single natural gas hydrate inhibitor has limited inhibitory activity and causes environmental damage when used in excessively high concentrations, improving the inhibitory effect of natural gas hydrate inhibitors by compounding different natural gas hydrate inhibitors has become one of the current research hotspots. For example, the prior art "A Natural Gas Hydrate Inhibitor" discloses a combined inhibitor composed of polyvinyl pyrrolidone, polyether amine, and ethylene glycol butyl ether, but the prior art has little research on combined inhibitors.

[0007] Therefore, it is quite necessary to study how to improve the inhibitory effect of natural gas hydrate inhibitors on the formation of natural gas hydrates by compounding different natural gas hydrate inhibitors. Summary of the invention

[0008] In view of the deficiencies in the prior art, the present invention aims to provide an efficient treatment agent for hydrate flow obstruction in a wellbore. As a combined inhibitor, the agent is compounded from three substances to enhance the inhibitory effect on the formation of natural gas hydrates.

[0009] The primary purpose of the present invention is to provide an efficient treatment agent for hydrate flow obstruction in a wellbore.

[0010] Another object of the present invention is to provide a structurally modified polyvinyl caprolactam (modified inhibitor) containing a -CH2-CH(NH2)-COOH group.

[0011] Another object of the present invention is to provide use of the modified inhibitor in the preparation of natural gas hydrate inhibitors.

[0012] Another object of the present invention is to provide the use of the modified inhibitor in combination with amino acids and alcohols in the preparation of an efficient hydrate flow disorder treating agent.

[0013] The present invention achieves the above-mentioned invention object through the following technical solutions:

[0014] The present invention provides a high-efficiency treatment agent for hydrate flow obstruction in a wellbore, which is composed of polyvinyl caprolactam (modified inhibitor) with a modified structure containing a -CH2-CH(NH2)-COOH group, amino acids, and alcohols; the modified inhibitor has a structural formula as shown in formula (a):

[0015]

[0016] The weight average molecular weight of the modified inhibitor is 1,000 to 1,500,000.

[0017] Preferably, the amino acid is an amino acid that does not contain sulfur.

[0018] More preferably, the amino acid includes but is not limited to glycine or histidine.

[0019] Preferably, the alcohol is a monohydric alcohol or a dihydric alcohol having no more than 3 carbon atoms.

[0020] More preferably, the alcohol includes but is not limited to methanol or propylene glycol.

[0021] Preferably, the mass ratio of the modification inhibitor, the amino acid and the alcohol is 1-5:1-6:1-5.

[0022] More preferably, when the gas hydrate inhibitor is used, the gas hydrate inhibitor is first prepared into an aqueous solution, and the total concentration of the modified inhibitor, amino acid, and alcohol in the aqueous solution is 0.5wt% to 11wt%. More preferably, the total concentration of the modified inhibitor, amino acid, and alcohol in the aqueous solution is 4.5wt% to 11wt%.

[0023] The present invention also provides a modified inhibitor having a structural formula as shown in formula (a):

[0024]

[0025] The weight average molecular weight of the modified inhibitor is 1,000 to 1,500,000.

[0026] The present invention has found that the modified inhibitor provided by the present invention can significantly prolong the induction time of natural gas hydrate formation, so the use of the modified inhibitor provided by the present invention in the preparation of natural gas hydrate inhibitors should also be within the protection scope of the present invention.

[0027] At the same time, the high-efficiency hydrate flow barrier treatment agent obtained by combining the modified inhibitor provided by the present invention with amino acids and alcohols significantly enhances the inhibitory effect on the induction time of natural gas hydrate formation. Therefore, the use of the modified inhibitor provided by the present invention in combination with amino acids and alcohols in the preparation of a high-efficiency hydrate flow barrier treatment agent should also be within the scope of protection of the present invention.

[0028] Preferably, the amino acid is an amino acid that does not contain sulfur.

[0029] More preferably, the amino acid comprises glycine or histidine.

[0030] Preferably, the alcohol is a monohydric alcohol or a dihydric alcohol having no more than 3 carbon atoms.

[0031] More preferably, the alcohol includes but is not limited to methanol or propylene glycol.

[0032] The present invention also provides a method for preparing the modified inhibitor, which is obtained by reacting N-vinyl caprolactam with L-2-amino-3-mercaptopropionic acid.

[0033] Preferably, the mass ratio of N-vinyl caprolactam to L-2-amino-3-mercaptopropionic acid is 40-60:1.6-2.4, and most preferably 25:1.

[0034] Preferably, an initiator is also added to the reaction.

[0035] More preferably, the initiator is 2,2'-azobis(2-(2-imidazolin-2-yl)propane) dihydrochloride.

[0036] More preferably, the mass ratio of N-vinyl caprolactam to 2,2'-azobis(2-(2-imidazolin-2-yl)propane) dihydrochloride is 40-60:0.8-1.2, and most preferably 50:1.

[0037] As an optional preferred embodiment, the above preparation method comprises the following steps:

[0038] N-vinyl caprolactam is dissolved in water, and then 2,2'-azobis(2-(2-imidazoline-2-yl)propane) dihydrochloride and L-2-amino-3-mercaptopropionic acid are added and mixed, and heated in an oil bath for reaction to obtain the structurally modified polyethylene caprolactam containing -CH2-CH(NH2)-COOH groups (PVCap-S-CH2-CH(NH2)-COOH).

[0039] Preferably, the ratio of the mass of N-vinyl caprolactam to the volume of water is 4 g to 6 g: 130 mL to 170 mL, and most preferably 5 g to 150 mL.

[0040] Preferably, the temperature of the oil bath is 30-50°C, most preferably 40°C.

[0041] Preferably, the reaction time is 12 to 20 hours, most preferably 16 hours.

[0042] Preferably, the reaction is carried out under a nitrogen environment.

[0043] Preferably, water is removed after the reaction.

[0044] More preferably, the method for removing moisture is: first remove moisture by a rotary evaporator, dry the rotary evaporator and wash with anhydrous ether, then dry at 30°C to 50°C for 20h to 28h under vacuum conditions, and then dry at 100°C to 120°C for 20h to 28h. Most preferably, dry at 40°C in a vacuum drying oven for 24h, and then dry at 110°C for 24h.

[0045] The technical solution of the present invention has the following beneficial effects:

[0046] The present invention provides a high-efficiency treatment agent for hydrate flow obstruction in a wellbore, which is obtained by combining the modified inhibitor, amino acid and alcohol provided by the present invention. The three substances in the high-efficiency treatment agent for hydrate flow obstruction synergistically play the role of inhibiting the formation of natural gas hydrates, and have a significant inhibitory effect on the formation of natural gas hydrates; at the same time, the dosage of these substances is low, and will not cause damage to the environment, which is green and environmentally friendly, and has a wide range of application prospects in natural gas mining and transportation. DETAILED DESCRIPTION

[0047] The present invention is further described below with reference to specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0048] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0049] Example 1 Synthesis of Polyethylene Caprolactam Containing -CH2-CH(NH2)-COOH Group Modified Structure

[0050] Take 5g of N-vinyl caprolactam monomer and place it in a three-necked flask, add 150mL of sterilized water and a magnet, turn on the magnetic stirring to fully dissolve the monomer. Weigh 0.1g of 2,2'-azobis(2-(2-imidazoline-2-yl)propane) dihydrochloride (AIBI) and 0.2g of L-2-amino-3-mercaptopropionic acid and add them to the three-necked flask, quickly connect the three ports of the three-necked flask with condensers, install a thermometer, and seal with a rubber stopper. After evacuating the entire system, nitrogen is introduced, and this is repeated three times, and then nitrogen is continuously introduced to ensure that there is no air in the system and that the reaction is carried out under the protection of nitrogen throughout the process. Immerse the three-necked flask in an oil bath, set the oil bath temperature to 40°C, and start timing when the thermometer shows that the temperature reaches 40°C. The reaction time is 16h. After the reaction is completed, the solution is transferred to a rotary evaporator, and the rotary evaporator is connected to a vacuum pump for reduced pressure rotary evaporation. After no liquid is evaporated, it is washed with anhydrous ether. After standing in a beaker until no precipitation is precipitated, the upper ether is poured off. The beaker is transferred to a vacuum drying oven, dried at 40°C for 24 hours, and then dehydrated at 110°C for 24 hours to obtain a modified inhibitor PVCap-S-CH2-CH(NH2)-COOH (polyethylene caprolactam with a -CH2-CH(NH2)-COOH group structure modification). The reaction equation is shown in formula (I).

[0051]

[0052] Example 2 Synthesis of Polyethylene Caprolactam Containing -CH2-CH(NH2)-COOH Group Modified Structure

[0053] Take 4g of N-vinyl caprolactam monomer and place it in a three-necked flask, add 130mL of sterilized water and a magnet, turn on the magnetic stirring to fully dissolve the monomer. Weigh 0.08g of 2,2'-azobis(2-(2-imidazoline-2-yl)propane) dihydrochloride (AIBI) and 0.16g of L-2-amino-3-mercaptopropionic acid and add them to the three-necked flask, quickly connect the three ports of the three-necked flask with condensers, install a thermometer, and seal with a rubber stopper. After evacuating the entire system, nitrogen is introduced, and this is repeated three times, and then nitrogen is continuously introduced to ensure that there is no air in the system and that the reaction is carried out under the protection of nitrogen throughout the process. Immerse the three-necked flask in an oil bath, set the oil bath temperature to 30°C, and start timing when the thermometer shows that the temperature reaches 30°C. The reaction time is 20h. After the reaction is completed, the solution is transferred to a rotary evaporator, and the rotary evaporator is connected to a vacuum pump for reduced pressure rotary evaporation. After no liquid is evaporated, it is washed with anhydrous ether. After standing in a beaker until no precipitation is precipitated, the upper ether is poured off. The beaker is transferred to a vacuum drying oven, dried at 40°C for 24 hours, and then dehydrated at 110°C for 24 hours to obtain a modified inhibitor PVCap-S-CH2-CH(NH2)-COOH (polyethylene caprolactam with a -CH2-CH(NH2)-COOH group structure modification). The reaction equation is shown in formula (II).

[0054]

[0055] Example 3 Synthesis of Polyvinyl Caprolactam Containing -CH2-CH(NH2)-COOH Group Modified Structure

[0056] Take 6g of N-vinyl caprolactam monomer and place it in a three-necked flask, add 170mL of sterilized water and a magnet, turn on the magnetic stirring to fully dissolve the monomer. Weigh 0.12g of 2,2'-azobis(2-(2-imidazoline-2-yl)propane) dihydrochloride (AIBI) and 0.24g of L-2-amino-3-mercaptopropionic acid and add them to the three-necked flask, quickly connect the three ports of the three-necked flask with condensers, install a thermometer, and seal with a rubber stopper. After evacuating the entire system, nitrogen is introduced, and this is repeated three times, and then nitrogen is continuously introduced to ensure that there is no air in the system and that the reaction is carried out under the protection of nitrogen throughout the process. Immerse the three-necked flask in an oil bath, set the oil bath temperature to 50°C, and start timing when the thermometer shows that the temperature reaches 50°C. The reaction time is 12h. After the reaction is completed, the solution is transferred to a rotary evaporator, and the rotary evaporator is connected to a vacuum pump for reduced pressure rotary evaporation. After no liquid is evaporated, it is washed with anhydrous ether. After standing in a beaker until no precipitation is precipitated, the upper ether is poured off. The beaker is transferred to a vacuum drying oven, dried at 40°C for 24 hours, and then dehydrated at 110°C for 24 hours to obtain a modified inhibitor PVCap-S-CH2-CH(NH2)-COOH (polyethylene caprolactam with a -CH2-CH(NH2)-COOH group structure modification). The reaction equation is shown in formula (III).

[0057]

[0058] Experimental Example 1: Test of the inhibitory effect of modified inhibitor and hydrate flow barrier high-efficiency treatment agent on natural gas hydrate formation

[0059] This example tests the inhibitory effect of modified inhibitor (PVCap-S-CH2-CH(NH2)-COOH) and hydrate flow barrier high-efficiency treatment agent a composed of modified inhibitor + glycine + propylene glycol on natural gas hydrates, and pure water, modified inhibitor with the same concentration, glycine with the same concentration or propylene glycol with the same concentration are used as control groups. The inhibitory effect of the above inhibitors on the formation of natural gas hydrates of the following three gases is tested respectively, gas 1 is pure methane; gas 2 is a multi-component mixed gas, composed of methane 92vol%, ethane 5vol% and propane 3vol%; gas 3 is a multi-component mixed gas, composed of n-pentane 0.208vol%, isopentane 0.201vol%, isobutane 0.493vol%, n-butane 0.789vol%, propane 3.13vol%, ethane 7.51vol%, nitrogen 0.398vol%, and the rest is methane.

[0060] The modified inhibitor and hydrate flow barrier high-efficiency treatment agent a test adopts a high-pressure stirring test reaction device, which mainly includes: constant temperature water bath, reactor, buffer tank, magnetic stirrer, data acquisition module, temperature sensor, pressure sensor, etc. The volume of the reactor is 600mL, and the maximum pressure it can withstand is 25MPa; the model of the pressure sensor is CYB-20S, with an accuracy of ±0.025MPa; the model of the temperature sensor is PT100, with an accuracy of ±0.1℃.

[0061] Experimental method: According to the mass percentage of modified inhibitor, glycine and propylene glycol shown in Table 1, the raw materials are mixed to prepare the hydrate flow barrier high-efficiency treatment agent a, and pure water, modified inhibitor of the same concentration, glycine of the same concentration and propylene glycol of the same concentration are prepared separately, and added into different reactors according to the mass of 110.0±0.5g. When the temperature is reduced to the preset temperature, the reactor is evacuated and the above-mentioned gas 1 or gas 2 or gas 3 is introduced into the reactor to the target pressure according to the experimental combination shown in Table 1. The air inlet valve on the reactor is closed, and then the gas source is closed, and the magnetic stirring is started, and the experiment begins. The temperature, pressure and time after the start of the experiment are recorded, and the reaction process is observed. When the temperature rises and then decreases to a certain temperature and is stable for a long time (more than 3 hours), the pressure decreases in a single trend within 30 minutes, and the experiment and related data recording are stopped. The induction time of natural gas hydrate formation after adding different inhibitors is investigated, so as to determine the inhibition performance of different inhibitors. The experimental results are shown in Table 1.

[0062] Table 1 Test results of inhibition performance of modified inhibitor and hydrate flow barrier high-efficiency treatment agent a

[0063]

[0064]

[0065] It can be seen that the modified inhibitor provided by the present invention can inhibit the formation of natural gas hydrates when used alone at a low concentration, pure water has basically no inhibitory effect on the formation of natural gas hydrates, and low amounts of propylene glycol and low amounts of glycine have limited inhibitory effects on the formation of natural gas hydrates; in addition, after the modified inhibitor, glycine and propylene glycol are used in combination, the inhibitory effect of the hydrate flow obstacle high-efficiency treatment agent a on natural gas hydrates is significantly improved, and the effect is even better than the sum of the effects of the modified inhibitor, glycine and propylene glycol alone. The experimental results show that the combined use of the modified inhibitor, glycine and propylene glycol has a synergistic effect in improving the inhibitory ability to natural gas hydrates.

[0066] Experimental Example 2: Test of the inhibitory effect of modified inhibitor and hydrate flow barrier high-efficiency treatment agent on natural gas hydrate formation

[0067] This example tests the inhibitory effect of modified inhibitor (PVCap-S-CH2-CH(NH2)-COOH) and hydrate flow barrier high-efficiency treatment agent b composed of modified inhibitor + histidine + methanol on natural gas hydrates, with pure water, modified inhibitor with the same concentration, histidine with the same concentration or methanol with the same concentration as the control group. The inhibitors were tested for their inhibitory effect on the formation of natural gas hydrates of the following three gases, respectively: gas 1 was pure methane; gas 2 was a multi-component mixed gas, consisting of 92 vol% methane, 5 vol% ethane and 3 vol% propane; gas 3 was a multi-component mixed gas, consisting of 0.208 vol% n-pentane, 0.201 vol% isopentane, 0.493 vol% isobutane, 0.789 vol% n-butane, 3.13 vol% propane, 7.51 vol% ethane, 0.398 vol% nitrogen, and the rest methane.

[0068] The modified inhibitor and hydrate flow barrier high-efficiency treatment agent b are tested using a high-pressure stirring test reaction device, which mainly includes: a constant temperature water bath, a reactor, a buffer tank, a magnetic stirrer, a data acquisition module, a temperature sensor, a pressure sensor, etc. The volume of the reactor is 600mL, and the maximum pressure it can withstand is 25MPa; the model of the pressure sensor is CYB-20S, with an accuracy of ±0.025MPa; the model of the temperature sensor is PT100, with an accuracy of ±0.1℃.

[0069] Experimental method: According to the mass percentage of modified inhibitor, histidine and methanol shown in Table 2, high-efficiency treatment agent b for hydrate flow obstruction was prepared, and pure water, modified inhibitor of the same concentration, glycine of the same concentration and propylene glycol of the same concentration were prepared separately, and added to different reactors according to the mass of 110.0±0.5g. After the temperature dropped to the preset temperature, the reactor was evacuated and the above gas 1, gas 2 or gas 3 was introduced to the reactor to the target pressure according to the experimental combination shown in Table 2. The air inlet valve on the reactor was closed, and then the gas source was closed, and the magnetic stirring was started, and the experiment began. The temperature, pressure and time after the start of the experiment were recorded, and the reaction process was observed. When the temperature rose and then dropped to a certain temperature and stabilized for a long time (more than 3 hours), the pressure decreased in a single trend within 30 minutes, and the experiment and related data recording were stopped. The hydrate formation induction time after adding different inhibitors was investigated, so as to determine the inhibition performance of different inhibitors. The experimental results are shown in Table 2.

[0070] Table 2 Test results of inhibition performance of modified inhibitor and hydrate flow barrier high-efficiency treatment agent b

[0071]

[0072] It can be seen that pure water has basically no inhibitory effect on the formation of natural gas hydrates, low dosages of methanol and low dosages of histidine have limited inhibitory effects on the formation of natural gas hydrates, and the high-efficiency hydrate flow obstacle treatment agent obtained by combining the modified inhibitor, histidine and methanol has a significant inhibitory effect on the formation of natural gas hydrates at a low concentration, indicating that the combined use of the three natural gas hydrate inhibitors can significantly enhance the inhibitory ability of a single natural gas hydrate inhibitor on natural gas hydrates.

[0073] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A highly efficient treatment agent for hydrate flow obstruction in a wellbore, characterized in that: It is composed of a modified inhibitor, an amino acid, and an alcohol; the modified inhibitor has a structural formula as shown in formula (a): The weight average molecular weight of the modified inhibitor is 1000 to 1500000; The amino acid is glycine or histidine; The alcohol is methanol or propylene glycol; The mass ratio of the modified inhibitor, amino acid and alcohol is 1-5:1-6:1-5.

2. The high-efficiency treating agent for hydrate flow obstruction according to claim 1, characterized in that: When the hydrate flow barrier high-efficiency treatment agent is used, it is first prepared into an aqueous solution, in which the total concentration of the modification inhibitor, amino acid and alcohol is 0.5wt% to 11wt%.

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