Surfactin sodium hydrate polymerization inhibitor and its use

Abstract

The present application relates to the field of prevention and treatment of gas hydrate in deepwater oil and gas gathering pipeline, and particularly relates to a kind of subtilisin lipopeptide sodium hydrate polymerization inhibitor and its application.The subtilisin lipopeptide sodium has the general formula as formula I, and R1 in the formula I is C12-C15 saturated fatty acid chain.The polymerization inhibitor can make the generated hydrate particles form hydrate slurry and flow in the pipeline with fluid without gathering into large blocks or depositing on the pipe wall.The present application is suitable for gas-water two-phase and oil-gas-water three-phase coexisting system, and the effective concentration is as low as 0.01 wt% (based on the mass of system water), with the characteristics of wide applicability, low cost and environmental friendliness.

Description

Technical Field

[0001] This invention relates to the field of gas hydrate prevention and control technology in deep-water oil and gas gathering and transportation pipelines, specifically to a Bacillus subtilis lipopeptide sodium hydrate inhibitor and its application. Background Technology

[0002] Gas hydrates are ice-like cage-like compounds formed by water and guest molecules (such as CH4, C2H6, C3H8, and CO2) under certain high pressure and low temperature conditions. In multiphase pipelines transporting oil, gas, and water, hydrates easily form under high pressure and low temperature. Severe formation and accumulation of gas hydrates can lead to pipeline blockage, interruption of oil and gas transportation, threat to production safety, and even safety accidents and economic losses.

[0003] To address the risk of pipeline hydrate blockage, measures such as alcohol injection, heating or insulation, pressure reduction, and inhibitor injection are mainly employed, with inhibitor injection being the most widely used. Based on their inhibition mechanisms, hydrate inhibitors can be classified into three categories: thermodynamic inhibitors, kinetic inhibitors, and polymerization inhibitors. Kinetic inhibitors and polymerization inhibitors are collectively referred to as low-dose inhibitors, which can reduce the risk of hydrate blockage at relatively low dosages (≤2wt%). Kinetic inhibitors can inhibit hydrate nucleation or growth, maintaining a low volume fraction of hydrates in the pipeline; however, they are mostly polymers and are prone to failure under deep-water, high-supercooling conditions. In contrast, polymerization inhibitors exhibit good effects even at higher supercooling conditions, dispersing already formed hydrates in the liquid phase as small particles, forming a flowable hydrate slurry, thus preventing pipeline blockage and showing significant application potential. Currently, most hydrate polymerization inhibitors are only suitable for oil-containing systems, and those suitable for both oil-gas-water and gas-water systems are extremely rare.

[0004] Therefore, based on the advantages and disadvantages of existing hydrate polymerization inhibitors, developing hydrate anti-polymerization agents suitable for oil-gas-water systems and gas-water systems to prevent hydrate blockage in deep-water oil and gas pipelines has become an urgent technical problem to be solved, and is also the core objective of this invention. Summary of the Invention

[0005] To address the shortcomings of existing methods, this invention provides a subtilis lipopeptide sodium hydrate polymerization inhibitor and its application. This invention is achieved through the following technical solution:

[0006] A hydrate polymerization inhibitor comprising sodium subtilisin, wherein sodium subtilisin is a naturally extracted anionic surfactant having a molecular structure as shown in Formula I:

[0007] (Formula I)

[0008] As described above, the hydrate polymerization inhibitor, the sodium subtilis lipopeptide, comprises a hydrophilic head group and a hydrophobic tail chain. The hydrophilic head group is a cyclic heptapeptide group with strong structural stability, consisting of 7 amino acids, including 2 D-leucines, 2 L-leucines, 1 L-aspartic acid, 1 L-valine, and 1 glutamic acid, forming a 25-membered ring. The glutamic acid and aspartic acid residues constitute a secondary polar structure, and the valine residue extends downward. The hydrophobic tail chain R1 is a C12-C15 saturated fatty acid chain. The carboxyl terminus of the fatty acid tail chain is linked to the amino group of glutamic acid in the cyclic heptapeptide group to form an amide group. The molecular structure is shown in Formula II.

[0009] (Formula II)

[0010] The hydrate polymerization inhibitor described above is characterized in that the mass fraction of the sodium subtilis lipopeptide is 0.01 wt% to 2 wt% (based on the mass of water in the system).

[0011] Based on the same inventive concept, this invention also provides the application of Bacillus subtilis lipopeptide sodium hydrate inhibitor in the prevention and control of hydrates.

[0012] Preferably, the application of the subtilis lipopeptide sodium hydrate inhibitor as described above in the prevention and control of hydrates is suitable for oil-gas-water three-phase coexistence systems and / or gas-water two-phase coexistence systems.

[0013] Preferably, the applicable moisture content range is 30% to 100%.

[0014] Compared to existing hydrate inhibitors, the advantages of this invention are:

[0015] (1) When the hydrate polymerization inhibitor of the present invention is used, it can completely prevent hydrate blockage at a concentration of 0.01wt%-2wt% (based on the mass of water in the system), and prevent hydrate aggregation and blockage in the range of 30% to 100% water content. Its performance is significantly better than that of naturally extracted hydrate polymerization inhibitors such as lecithin. It is suitable for oil-gas-water coexistence systems and / or gas-water coexistence systems, and can meet the needs of hydrate prevention and control in complex environments of deep-water oil and gas transportation.

[0016] (2) The Bacillus subtilis lipopeptide sodium of the present invention is fermented from a high-yield strain of natural Bacillus subtilis spores. It is an anionic surfactant with good biodegradability, no environmental pollution or biotoxicity, and has been used in the cosmetics industry. Compared with traditional quaternary ammonium salt surfactant hydrate polymerization inhibitors, the hydrate polymerization inhibitor of the present invention has significantly reduced biotoxicity and environmental hazards. Attached Figure Description

[0017] Figure 1This is a standard diagram for classifying the hydrate polymerization inhibition levels in the swaying kettle in this embodiment of the invention;

[0018] Figure 2 This is an image showing the change in hydrate volume fraction and slider position over time in Comparative Example 1 of this invention.

[0019] Figure 3 This is an image showing the change in hydrate volume fraction and slider position over time in Comparative Example 2 of this invention.

[0020] Figure 4 This is an image showing the change in hydrate volume fraction and slider position over time in Example 1 of this invention. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0023] Unless otherwise specified, the experimental methods used in the following comparative examples and embodiments are conventional methods.

[0024] Unless otherwise specified, all materials and reagents used in the comparative examples and embodiments below are commercially available. In the comparative examples, lecithin is a reported nonionic biosurfactant purchased from Shanghai E. En Chemical Technology Co., Ltd.; in the embodiments, sodium subtilis lipopeptide was purchased from Bloomage Biotechnology Co., Ltd., and is an anionic surfactant.

[0025] This invention employs a high-pressure hydrate swing reactor experimental device as the testing equipment for the performance of polymerization inhibitors. The high-pressure hydrate swing reactor experimental device mainly consists of a reactor body, a swing system, a gas injection system, a data acquisition system, and a temperature control system. The swing system comprises a two-phase stepper motor, a driver, a rotating shaft, and a control box. The swing angle of the swing reactor is set to ±90°, and the maximum swing frequency is 1 time / minute. The gas injection system includes a vacuum pump, a high-pressure gas cylinder, a pressure reducing valve, a six-way valve, and gas pipelines. The data acquisition system contains all the hardware and software related to temperature, pressure, and displacement data, including temperature sensors, pressure sensors, displacement sensors, a data acquisition box, and real-time monitoring software. The temperature sensor has a range of -50℃ to 100℃ with a measurement accuracy of ±0.1℃, and the pressure sensor has a range of 0MPa to 40MPa with an accuracy of ±0.01MPa. The displacement sensor operates in a temperature range of -40℃ to 75℃, with a linearity less than ±0.02% of full scale. The monitoring software collects four position data points per second, reflecting the slider's descent process. The temperature control system uses a Ningbo Tianheng THX-2030H water bath, with a temperature range of -20℃ to 100℃ and a cooling rate of 2℃·h. -1 .

[0026] Based on the characteristics of the swing reactor equipment, a classification standard for polymerization inhibition performance is proposed. For example... Figure 1 The formation and aggregation of hydrates directly affect the movement of the slider. Hydrate particles dispersed in the liquid phase increase fluid viscosity, slowing the slider's displacement rate. Large hydrate aggregates deposit on both sides of the reactor as the slider moves, reducing its range of motion. Aged hydrate deposits can directly clog the slider. Considering the reactor's total length is 200mm and the slider's range of motion is 10mm-200mm, a range of motion of 190mm is considered normal movement, and 0mm is considered blockage. Based on this, the polymerization inhibition performance is classified into three levels: A, B, and C, from best to worst. If the slider moves normally throughout the experiment under the action of the polymerization inhibitor, the performance of this type of inhibitor is recorded as level A. Figure 1 In the middle (a); during the entire experiment, hydrate aggregates precipitated, causing a reduction in the slider's range of motion, but without any blockage. The performance of this type of polymerization inhibitor is classified as Grade B. Figure 1 (b) If blockage of the slider occurs during the entire experiment, the performance of the polymerization inhibitor is grade C. Figure 1 (c)

[0027] Using monitored temperature and pressure data, the volume fraction of hydrates in the reactor can be calculated. The method for calculating the volume fraction of hydrates is as follows:

[0028]

[0029] In the formula, V hydV represents the volume of the hydrate formed, in mL; oil V represents the volume of white oil, in mL; water V represents the initial volume of water, in mL; water,conv The volume of water converted into hydrates, in mL.

[0030] The polymerization inhibition effect of the hydrate polymerization inhibitor designed in this invention can be judged based on the volume fraction of hydrate, the final slider movement range, and the polymerization inhibition performance level. The higher the volume fraction of hydrate, the larger the final slider movement range, and the higher the polymerization inhibition performance level, the better the performance of the polymerization inhibitor.

[0031] Before the experiment, open the reactor end cap, add petroleum ether to repeatedly clean the inner wall of the reactor, and then dry it. Prepare an oil-water mixture by mixing No. 5 white oil, deionized water, and polymerization inhibitor in a certain proportion and add it to the reactor. Tighten the reactor end cap, and evacuate the reactor sequentially until the gauge pressure stabilizes. Set the water bath to 18℃. After the temperature inside the reactor stabilizes, open the gas cylinder switch, six-way valve, and reactor inlet valve to introduce high-purity methane into the reactor. Once the experimental pressure is reached, close the switches and valves. Turn on the control box and motor power, and set the swing angle and frequency of the oscillating reactor on the control box. The reactor begins to swing under the drive of the motor and rotating shaft, and the methane quickly dissolves in the white oil and water. Once the pressure inside the reactor stabilizes at 7MPa, set the water bath temperature to 0℃ and cool it at a constant rate of 2℃ / h. Simultaneously, activate the data acquisition function to record the temperature, pressure, and position data during the hydrate formation process. Once the temperature and pressure stabilized again, indicating that hydrate formation was complete, the water bath and data acquisition were shut off. The control box and motor power were also turned off. The gas inside the reactor was slowly released through the vent to prevent liquid from entering the high-pressure hose due to a sudden pressure drop. After all the gas was released, the waste liquid in the reactor was poured out, and the test was completed.

[0032] Comparative Examples 1 and 2 represent a system without a polymerization inhibitor and a system with the addition of lecithin, a previously reported nonionic biosurfactant. Examples 1 to 10 represent the subtilis lipopeptide sodium system of the present invention.

[0033] Comparative Example 1

[0034] 70 mL of No. 5 white oil was mixed with 30 mL of deionized water to prepare an oil-water mixture (water content 30%), which was then added to a shaking reactor. High-purity methane was selected as the experimental gas and injected into the reactor until the initial pressure reached 7 MPa. The experimental temperature was set at 2.5℃ as a blank group to test the aggregation and blockage of hydrates without the addition of polymerization inhibitor. After 12 hours of experiment, the temperature and pressure were basically stable, and hydrates were completely formed. The final hydrate volume fraction was 7.83%, the final slider displacement was 0 mm, and the polymerization inhibition level was C.

[0035] Comparative Example 2

[0036] 70 mL of No. 5 white oil was mixed with 30 mL of deionized water to prepare an oil-water mixture (water content 30%), and then 1.0 wt% lecithin was added as a polymerization inhibitor. This mixture was then added to a shaking reactor. High-purity methane was selected as the experimental gas and injected into the reactor until the initial pressure reached 7 MPa. The experimental temperature was set at 2.5℃. The performance of the polymerization inhibitor was tested. After 12 hours of experimentation, the temperature and pressure stabilized, hydrates were completely formed, the final hydrate volume fraction was 10.01%, the final slider displacement was 114.8 mm, and the polymerization inhibition level was B.

[0037] Example 1

[0038] 70 mL of No. 5 white oil was mixed with 30 mL of deionized water to prepare an oil-water mixture (water content 30%), and then 2.0 wt% of sodium subtilis lipopeptide was added as a polymerization inhibitor. This mixture was then added to a shaking reactor. High-purity methane was selected as the experimental gas and injected into the reactor until the initial pressure reached 7 MPa. The experimental temperature was set at 2.5℃. The performance of the polymerization inhibitor was tested. After 12 hours of experimentation, the temperature and pressure stabilized, hydrates were completely formed, the final hydrate volume fraction was 19.01%, the final slider displacement was 190.2 mm, and the polymerization inhibition level was Grade A.

[0039] Example 2

[0040] 70 mL of No. 5 white oil was mixed with 30 mL of deionized water to prepare an oil-water mixture (water content 30%), and then 1.5 wt% of sodium subtilis lipopeptide was added as a polymerization inhibitor. This mixture was then added to a shaking reactor. High-purity methane was selected as the experimental gas and injected into the reactor until the initial pressure reached 7 MPa. The experimental temperature was set at 2.5℃. The performance of the polymerization inhibitor was tested. After 12 hours of experimentation, the temperature and pressure stabilized, hydrates were completely formed, the final hydrate volume fraction was 19.26%, the final slider displacement was 191.3 mm, and the polymerization inhibition level was Grade A.

[0041] Example 3

[0042] 70 mL of No. 5 white oil was mixed with 30 mL of deionized water to prepare an oil-water mixture (water content 30%), and then 1.0 wt% of sodium subtilis lipopeptide was added as a polymerization inhibitor. This mixture was then added to a shaking reactor. High-purity methane was selected as the experimental gas and injected into the reactor until the initial pressure reached 7 MPa. The experimental temperature was set at 2.5℃. The performance of the polymerization inhibitor was tested. After 12 hours of experimentation, the temperature and pressure stabilized, hydrates were completely formed, the final hydrate volume fraction was 19.58%, the final slider displacement was 191.3 mm, and the polymerization inhibition level was Grade A.

[0043] Example 4

[0044] 70 mL of No. 5 white oil was mixed with 30 mL of deionized water to prepare an oil-water mixture (water content 30%), and then 0.5 wt% of sodium subtilis lipopeptide was added as a polymerization inhibitor. This mixture was then added to a shaking reactor. High-purity methane was selected as the experimental gas and injected into the reactor until the initial pressure reached 7 MPa. The experimental temperature was set at 2.5℃. The performance of the polymerization inhibitor was tested. After 12 hours of experimentation, the temperature and pressure stabilized, hydrates were completely formed, the final hydrate volume fraction was 18.15%, the final slider displacement was 190.5 mm, and the polymerization inhibition level was Grade A.

[0045] Example 5

[0046] 30 mL of No. 5 white oil was mixed with 70 mL of deionized water to prepare an oil-water mixture (70% water content), and then 1.0 wt% of sodium subtilis lipopeptide was added as a polymerization inhibitor. This mixture was then added to a shaking reactor. High-purity methane was selected as the experimental gas and injected into the reactor until the initial pressure reached 7 MPa. The experimental temperature was set at 2.5℃. The performance of the polymerization inhibitor was tested. After 12 hours of experimentation, the temperature and pressure stabilized, hydrates were completely formed, the final hydrate volume fraction was 15.52%, the final slider displacement was 190.4 mm, and the polymerization inhibition level was Grade A.

[0047] Example 6

[0048] 30 mL of No. 5 white oil was mixed with 70 mL of deionized water to prepare an oil-water mixture (70% water content), and then 0.5 wt% of sodium subtilis lipopeptide was added as a polymerization inhibitor. This mixture was then added to a shaking reactor. High-purity methane was selected as the experimental gas and injected into the reactor until the initial pressure reached 7 MPa. The experimental temperature was set at 2.5℃. The performance of the polymerization inhibitor was tested. After 12 hours of experimentation, the temperature and pressure stabilized, hydrates were completely formed, the final hydrate volume fraction was 14.44%, the final slider displacement was 191.7 mm, and the polymerization inhibition level was Grade A.

[0049] Example 7

[0050] Take 100 mL of deionized water (100% water content) and add 0.5 wt% of sodium subtilis lipopeptide as a polymerization inhibitor. Add it to a shaking reactor. High-purity methane is selected as the experimental gas and injected into the reactor to an initial pressure of 7 MPa. The experimental temperature is set at 2.5℃. The performance of the polymerization inhibitor is tested. After 12 hours of experiment, the temperature and pressure are basically stable, hydrate is completely formed, the final hydrate volume fraction is 15.07%, the final slider displacement is 190.7 mm, and the polymerization inhibition level is Grade A.

[0051] Example 8

[0052] Take 100 mL of deionized water (100% water content) and add 0.1 wt% of sodium subtilis lipopeptide as a polymerization inhibitor. Add it to a shaking reactor. High-purity methane is selected as the experimental gas and injected into the reactor to an initial pressure of 7 MPa. The experimental temperature is set at 2.5℃. The performance of the polymerization inhibitor is tested. After 12 hours of experiment, the temperature and pressure are basically stable, hydrate is completely formed, the final hydrate volume fraction is 13.57%, the final slider displacement is 190.7 mm, and the polymerization inhibition level is Grade A.

[0053] Example 9

[0054] Take 100 mL of deionized water (100% water content) and add 0.05 wt% of sodium subtilis lipopeptide as a polymerization inhibitor. Add it to a shaking reactor. High-purity methane is selected as the experimental gas and injected into the reactor to an initial pressure of 7 MPa. The experimental temperature is set at 2.5℃. The performance of the polymerization inhibitor is tested. After 12 hours of experiment, the temperature and pressure are basically stable, hydrate is completely formed, the final hydrate volume fraction is 13.65%, the final slider displacement is 191.5 mm, and the polymerization inhibition level is Grade A.

[0055] Example 10

[0056] Take 100 mL of deionized water (100% water content) and add 0.01 wt% of sodium subtilis lipopeptide as a polymerization inhibitor. Add it to a shaking reactor. High-purity methane is selected as the experimental gas and injected into the reactor to an initial pressure of 7 MPa. The experimental temperature is set at 2.5℃. The performance of the polymerization inhibitor is tested. After 12 hours of experiment, the temperature and pressure are basically stable, hydrate is completely formed, the final hydrate volume fraction is 13.67%, the final slider displacement is 190.9 mm, and the polymerization inhibition level is Grade A.

[0057] Experimental results show that the hydrate polymerization inhibitor of the present invention can completely prevent hydrate blockage at a concentration of 0.01wt%-2wt% (based on the mass of water in the system), and prevent hydrate aggregation and blockage within a water content range of 30% to 100%. It is also suitable for oil-gas-water coexistence systems and gas-water coexistence systems. Its performance is significantly better than that of naturally extracted hydrate polymerization inhibitors such as lecithin, which have been reported, and can meet the needs of hydrate control in complex environments of deep-water oil and gas transportation.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. The application of a hydrate polymerization inhibitor in the prevention and control of hydrates, characterized in that, The hydrate polymerization inhibitor includes sodium subtilis lipopeptide, the molecular structure of which includes a hydrophilic head group and a hydrophobic tail chain. The hydrophilic head group is a cyclic heptapeptide group, and the hydrophobic tail chain R1 is a C12-C15 saturated fatty acid chain. The mass fraction of sodium subtilis lipopeptide is 0.01wt% to 2wt%. The sodium subtilis lipopeptide has the molecular structure of Formula I: (Equation I).

2. The application of the hydrate polymerization inhibitor according to claim 1 in the prevention and control of hydrates, characterized in that, Used for the prevention and control of gas hydrates in deep-water oil and gas gathering and transportation pipelines.

3. The application of the hydrate polymerization inhibitor according to claim 1 in the prevention and control of hydrates, characterized in that, It is used in three-phase systems of oil-gas-water coexistence and / or two-phase systems of gas-water coexistence.

4. The application of the hydrate polymerization inhibitor according to claim 1 in the prevention and control of hydrates, characterized in that, The applicable moisture content range is 30% to 100%.

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