Hydrate kinetic inhibitor as well as preparation method and application thereof

Abstract

The invention discloses a hydrate kinetic inhibitor as well as a preparation method and application thereof. The structural formula of the hydrate kinetic inhibitor is shown as a formula I. In the formula I, x: y is (1-9): 1. The preparation method of the hydrate kinetic inhibitor as shown in the formula I comprises the following steps: mixing N-vinyl caprolactam and vinyl isobutyl ether with a solvent, adding an initiator, carrying out binary copolymerization reaction, and then adding a terminating agent, so as to obtain the hydrate kinetic inhibitor as shown in the formula I. The hydrate kinetic inhibitor has excellent performance of inhibiting formation of hydrates, and can better solve the problem of pipe blockage caused by formation of hydrates in oil and gas development and transportation. # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas exploitation and transportation, and relates to a hydrate kinetic inhibitor and a preparation method and application thereof. Background Art

[0002] Natural gas hydrates are usually ice-like cage compounds formed by gas molecules and water molecules under high pressure and low temperature conditions. They are found in large quantities in nature, especially in permafrost on land and in the deep sea. They also often appear in oil and gas pipelines and laboratories. Since the discovery of natural gas hydrates in natural gas pipelines, their prevention and control has always been a major challenge for the oil and gas industry. As oil and gas drilling gradually develops into deep ocean waters, the higher hydrostatic pressure and lower ambient temperature in deep waters also provide favorable conditions for the formation of hydrates. Once hydrates are formed in the pipeline, some will flow with the fluid in the pipe, and some will adhere to the pipe wall and deposit, gradually blocking the pipeline, causing the fluid to be unable to be transported normally, and even causing serious safety accidents, leading to significant economic losses.

[0003] Therefore, the research on gas hydrate risk prevention and control technology has always been valued and supported by the oil and gas industry. In response to the risk of hydrate blockage in pipelines, different mitigation measures and remedial strategies have been developed, such as pressure reduction, injection of chemical inhibitors, and heating. Among them, chemical inhibitor injection is the most commonly used method. Traditional thermodynamic inhibitors may bring high costs and environmental risks due to their large dosage. Therefore, low-dose hydrate kinetic inhibitors (LDHIs) are considered to be a potential alternative that can effectively inhibit the nucleation and growth of hydrates without changing the thermodynamic conditions for hydrate formation. At present, some foreign gas fields have commercially applied hydrate kinetic inhibitors, such as PVP and Inhibex 501. It has been proven that these low-dose hydrate kinetic inhibitors can effectively inhibit the formation of hydrates.

[0004] In summary, it is of great commercial significance to develop efficient, environmentally friendly and low-cost hydrate kinetic inhibitors. Summary of the invention

[0005] The purpose of the present invention is to provide a hydrate kinetic inhibitor and a preparation method and application thereof; the hydrate kinetic inhibitor has excellent performance in inhibiting hydrate formation and can better solve the problem of pipe blockage caused by hydrate formation in oil and gas development and transportation.

[0006] The present invention provides a hydrate kinetic inhibitor, the structural formula of which is shown in Formula I.

[0007] In formula I, x:y is 1~9:1.

[0008] In the above-mentioned hydrate kinetic inhibitor, the relative molecular mass of the hydrate kinetic inhibitor may be 1000-50000.

[0009] The present invention also provides a method for preparing the hydrate kinetic inhibitor represented by the above formula I, which comprises the following steps: N-vinyl caprolactam and vinyl isobutyl ether are mixed with a solvent, an initiator is added, a binary copolymerization reaction is carried out, and then a terminator is added to obtain the hydrate kinetic inhibitor shown in formula I.

[0010] In the above preparation method, the temperature of the binary copolymerization reaction can be 323.15~363.15 K, specifically 353.15K, 323.15~353.15 K, 353.15~363.15 K, and the reaction time can be 5~12h, specifically 6h, 7h, 8h, 9h, 10h, 6~12h or 6~10h.

[0011] In the above preparation method, the molar ratio of the N-vinyl caprolactam to the vinyl isobutyl ether may be 1 to 9:1, specifically 1:1, 3:2, 7:3, 4:1 or 9:1.

[0012] In the above preparation method, the total weight of the N-vinyl caprolactam and vinyl isobutyl ether is 100% for calculation: The amount of the initiator can be 0.01% to 0.5%, specifically 0.01%; the amount of the terminator can be 0.01% to 0.1%, specifically 0.05%, 0.01% to 0.05%, 0.05% to 0.1%; The initiator comprises at least one of azobisisobutyronitrile, dimethyl azobisisobutyrate, azobisisoheptanenitrile and tert-butyl hydroperoxide; The terminator includes styrene and / or methacrylic acid.

[0013] In the above preparation method, the weight ratio of the solvent to the sum of the N-vinyl caprolactam and vinyl isobutyl ether may be 2 to 10:1; The solvent includes at least one of ethanol, isopropanol, N,N-dimethylformamide and n-propanol. The hydrate kinetic inhibitor of the present invention is used to inhibit hydrate formation during oil and gas development or transportation. In the above application, the hydrate kinetic inhibitor is used to inhibit hydrate formation in an oil-gas-water three-phase system or a gas-water two-phase system; The pressure of the oil-gas-water three-phase system or the gas-water two-phase system may be 0.2-30 MPa, and the temperature may be -15°C-30°C.

[0014] In the above application, when the hydrate kinetic inhibitor is used alone, the weight percentage of the hydrate kinetic inhibitor used can be 0.5-5.0%, specifically 0.5%, calculated based on the total weight of water in the system as 100%.

[0015] The present invention has the following beneficial effects: (1) The hydrate kinetic inhibitor provided by the present invention is a binary copolymer obtained by binary copolymerization of N-vinyl caprolactam and vinyl isobutyl ether monomers, which has good water solubility and can ensure that it works in the aqueous phase; (2) Compared with traditional thermodynamic inhibitors, the hydrate kinetic inhibitor provided by the present invention has the advantages of small dosage, low cost and significant effect; (3) Compared with existing hydrate kinetic inhibitors, such as PVP and Inhibex 501, the hydrate kinetic inhibitor provided by the present invention has a better inhibitory effect on hydrates and has good commercial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the infrared spectrum of the hydrate kinetics inhibitor of Example 1. DETAILED DESCRIPTION

[0017] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0018] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0019] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0020] Example 1 This embodiment provides a hydrate kinetic inhibitor, and the preparation method thereof comprises the following steps: (1) Selecting N-vinyl caprolactam and vinyl isobutyl ether as synthetic raw materials, using isopropyl alcohol as a solvent for polymerization reaction, and mixing the synthetic raw materials and the solvent to obtain a mixture; wherein the amounts of N-vinyl caprolactam and vinyl isobutyl ether are 5.8155 g and 4.1845 g, respectively (i.e., the molar ratio is 1:1); and the amount of isopropyl alcohol is 30 g; (2) Add the above mixture into a three-necked round-bottom flask. After the temperature of the thermostatic water bath reaches 353.15K, add 0.01% of the total weight of the two monomers as the initiator azobisisobutyronitrile into the three-necked round-bottom flask. Then quickly fix the three-necked round-bottom flask in the thermostatic water bath. Install a condenser on the three-necked round-bottom flask and start stirring after nitrogen is introduced into the three-necked round-bottom flask. Keep the water bath temperature and stirring speed constant during the reaction. Stop heating after 10 hours of reaction. Add 0.05% of the total weight of the two monomers as the terminator styrene into the three-necked round-bottom flask. (3) When the system temperature is cooled to room temperature, the nitrogen gas is stopped and the stirring is turned off, and the product in the three-necked round-bottom flask is transferred to a beaker to obtain a crude product of the hydrate kinetic inhibitor; (4) The liquid in the beaker was transferred to a rotary evaporator, and the crude product of the hydrate kinetic inhibitor was purified by the rotary evaporator. The purified product was taken out and vacuum dried at a temperature of 323.15 K to obtain the hydrate kinetic inhibitor, whose relative molecular mass was 13425. Finally, the product was sealed and stored in a dry and cool place for future use.

[0021] The hydrate kinetic inhibitor obtained in this example was subjected to infrared spectroscopy analysis, and the obtained infrared spectrum is shown in FIG. Figure 1 As shown, from Figure 1 It can be seen that the binary copolymer, i.e., the hydrate kinetic inhibitor, has an infrared absorption spectrum at 912 cm -1 、993 cm -1 、3080 cm -1 、1682 cm -1 There are no C=CH, =CH, C=C absorption peaks on the left and right, which indicates that unsaturated hydrocarbons have disappeared. -1 The strong absorption peaks on the left and right are the C=O absorption peaks on the polymer molecule caprolactam, 1430 cm -1 The absorption peaks on the left and right are strong absorption peaks of CN on the polymer molecule caprolactam. 2876 cm -1 and 2853 cm -1 The two strong absorption peaks on the left and right are the absorption peaks of saturated CH symmetric stretching vibration and antisymmetric stretching vibration. -1 There is no obvious absorption peak around 1150 cm -1 The strong absorption peaks on the left and right are the absorption peaks of the fatty ether COC, which indicates that the vinyl ether has been successfully polymerized with VCap, thereby converting it into fatty ether.

[0022] In summary, Figure 1The solid infrared data results shown indicate that N-vinyl caprolactam has been successfully polymerized with vinyl isobutyl ether monomer and has a high purity, contains no or only a trace amount of unreacted monomers, and the synthesized product is the target product.

[0023] Example 2 This embodiment provides a hydrate kinetic inhibitor, and its preparation method is basically the same as the preparation method of the hydrate kinetic inhibitor provided in Example 1, except that: (1) In this embodiment, the amounts of N-vinyl caprolactam and vinyl isobutyl ether monomers used are 6.7582 g and 3.2418 g respectively (molar ratio is 3:2); (2) The reaction time in this example is 8 h.

[0024] The relative molecular mass of the hydrate kinetic inhibitor obtained in this example is 19536, and the infrared spectrum is as follows: Figure 1 As shown, its infrared spectrum characteristic absorption peak is ~1617 cm -1 、1430 cm -1 、2876 cm -1 、2853 cm -1 , 1150 cm -1 Etc., indicating that the polymer has high purity, the system contains almost no unreacted monomers, and the polymer contains fatty ether, caprolactam and other groups.

[0025] Example 3 This embodiment provides a hydrate kinetic inhibitor, and its preparation method is basically the same as the preparation method of the hydrate kinetic inhibitor provided in Example 1, except that: (1) In this embodiment, the amounts of N-vinyl caprolactam and vinyl isobutyl ether monomers used are 7.6431 g and 2.3569 g respectively (molar ratio is 7:3); (2) The reaction time in this example is 6 h.

[0026] The relative molecular mass of the hydrate kinetic inhibitor obtained in this example is 26785, and the infrared spectrum is as follows: Figure 1 As shown, its infrared spectrum characteristic absorption peak is ~1617 cm -1 、1430 cm -1 、2876 cm -1 、2853 cm -1 , 1150 cm -1 Etc., indicating that the polymer has high purity, the system contains almost no unreacted monomers, and the polymer contains fatty ether, caprolactam and other groups.

[0027] Example 4 This embodiment provides a hydrate kinetic inhibitor, and its preparation method is basically the same as the preparation method of the hydrate kinetic inhibitor provided in Example 1, except that: (1) In this embodiment, the amounts of N-vinyl caprolactam and vinyl isobutyl ether monomers used are 8.4754 g and 1.5246 g respectively (molar ratio is 8:2); (2) The reaction time in this example is 7 h.

[0028] The relative molecular mass of the hydrate kinetic inhibitor obtained in this example is 23897, and the infrared spectrum is as follows: Figure 1 As shown, its infrared spectrum characteristic absorption peak is ~1617 cm -1 、1430 cm -1 、2876 cm -1 、2853 cm -1 , 1150 cm -1 Etc., indicating that the polymer has high purity, the system contains almost no unreacted monomers, and the polymer contains fatty ether, caprolactam and other groups.

[0029] Example 5 This embodiment provides a hydrate kinetic inhibitor, and its preparation method is basically the same as the preparation method of the hydrate kinetic inhibitor provided in Example 1, except that: (1) In this embodiment, the amounts of N-vinyl caprolactam and vinyl isobutyl ether monomers used are 9.2597 g and 0.7403 g respectively (molar ratio is 9:1); (2) The reaction time in this example is 9 h.

[0030] The relative molecular mass of the hydrate kinetic inhibitor obtained in this example is 22652, and the infrared spectrum is as follows: Figure 1 As shown, its infrared spectrum characteristic absorption peak is ~1617 cm -1 、1430 cm -1 、2876 cm -1 、2853 cm -1 , 1150 cm -1 Etc., indicating that the polymer has high purity, the system contains almost no unreacted monomers, and the polymer contains fatty ether, caprolactam and other groups.

[0031] Inhibition performance test: The inhibitory performance of the hydrate kinetic inhibitors prepared in Examples 1-5 and the existing conventional commercial inhibitors PVP (produced by Sigma-Aldrich) and Inhibex 501 (produced by Ashland Group) on the hydrate formation process is evaluated below. The device used in the evaluation experiment mainly consists of six parts: a visible high-pressure sapphire kettle, a temperature sensor, a pressure sensor, a data acquisition system, a constant temperature air bath and a magnetic stirring device; wherein the volume of the visible high-pressure sapphire kettle is 59 cm 3 , with an inner diameter of 2.54cm, and can withstand a maximum pressure of 40MPa to ensure the safety of the evaluation experiment operation; the errors of the pressure sensor and temperature sensor are ±0.01MPa and ±0.1K respectively; the temperature error of the constant temperature air bath is also ±0.1K, and the adjustment of the experimental temperature is mainly controlled by the constant temperature air bath.

[0032] The method for evaluating the inhibitory performance of hydrate kinetic inhibitors on the hydrate formation process is as follows: First, clean the visible high-pressure sapphire kettle by soaking it with petroleum ether and ethanol once, then clean it three times with anhydrous ethanol, then open the inlet and outlet valves of the visible high-pressure sapphire kettle, and purge it with nitrogen to make the inside completely dry; Add the prepared test solution containing the hydrate kinetic inhibitor into the visible high-pressure sapphire kettle, and use a vacuum pump to evacuate the kettle. After the air in the kettle is pumped out, close the valve to prevent the presence of air from interfering with the experimental results; Open the air inlet valve of the balance kettle, add sufficient experimental gas into the balance kettle, and then close the air inlet valve of the balance kettle; Turn on the constant temperature air bath and set the temperature of the constant temperature air bath to the experimental target temperature. When the temperature in the visible high-pressure sapphire kettle is stable at the target temperature, open the air inlet valve of the visible high-pressure sapphire kettle, and pass the experimental gas from the balance kettle into the visible high-pressure sapphire kettle. After reaching the target pressure, close the air inlet valve, turn on the magnetic stirring device, and keep the stirring speed unchanged during the entire experiment; Turn on the cold light source, observe the appearance and morphological changes of hydrates through the visual window of the constant temperature air bath, and record them with a camera. At the same time, the temperature and pressure data in the kettle are saved in real time through the data acquisition system.

[0033] The experimental gas used in the evaluation experiment was methane with a purity of 99.99%.

[0034] The evaluation experiment determines the strength of the hydrate kinetic inhibitor by measuring the nucleation time of hydrates. The nucleation time of hydrates is determined by real-time monitoring of the camera and real-time monitoring of the pressure change of the system by the pressure sensor. When the camera first captures the appearance of hydrate nuclei in the visible high-pressure sapphire reactor and the pressure sensor monitors that the pressure of the system begins to drop, the time at this time is the nucleation time of the hydrate in the system.

[0035] Test Example 1 10 g of an aqueous solution containing the hydrate kinetic inhibitor provided in Example 1 of the present invention (based on the total weight of water, the concentration of the hydrate kinetic inhibitor in the aqueous solution is 0.5 wt%) is added to a visible high-pressure sapphire kettle, and an experimental gas of 6.227 MPa is introduced into the visible high-pressure sapphire kettle at a temperature of 275.63 K to carry out an evaluation experiment. It is found that the nucleation time of hydrates in the system is 345 min, indicating that in the evaluation system, due to the presence of the hydrate kinetic inhibitor, the formation of hydrates is significantly inhibited.

[0036] Test Example 2 10 g of an aqueous solution containing the hydrate kinetic inhibitor provided in Example 2 of the present invention (the concentration of the hydrate kinetic inhibitor in the aqueous solution is 0.5 wt % based on the total weight of water) was added to a visible high-pressure sapphire kettle, and an experimental gas of 6.185 MPa was introduced into the visible high-pressure sapphire kettle at a temperature of 275.74 K to carry out an evaluation experiment. It was found that the nucleation time of hydrates in the system was 727 min, indicating that in the evaluation system, due to the presence of the hydrate kinetic inhibitor, the formation of hydrates was significantly inhibited.

[0037] Test Example 3 10 g of an aqueous solution containing the hydrate kinetic inhibitor provided in Example 3 of the present invention (based on the total weight of water, the concentration of the hydrate kinetic inhibitor in the aqueous solution is 0.5 wt%) is added to a visible high-pressure sapphire kettle, and an experimental gas of 6.192 MPa is introduced into the visible high-pressure sapphire kettle at a temperature of 275.77 K to carry out an evaluation experiment. It is found that the nucleation time of hydrates in the system is 389 min, indicating that in the evaluation system, due to the presence of the hydrate kinetic inhibitor, the formation of hydrates is significantly inhibited.

[0038] Test Example 4 10 g of an aqueous solution containing the hydrate kinetic inhibitor provided in Example 4 of the present invention (the concentration of the hydrate kinetic inhibitor in the aqueous solution is 0.5 wt % based on the total weight of water) was added to a visible high-pressure sapphire kettle, and an evaluation experiment was carried out by introducing 6.17 MPa of experimental gas into the visible high-pressure sapphire kettle at a temperature of 275.65 K. It was found that the nucleation time of hydrates in the system was 22 min, indicating that in the evaluation system, the formation of hydrates was inhibited due to the presence of the hydrate kinetic inhibitor.

[0039] Test Example 5 10 g of an aqueous solution containing the hydrate kinetic inhibitor provided in Example 5 of the present invention (based on the total weight of water, the concentration of the hydrate kinetic inhibitor in the aqueous solution is 0.5 wt%) is added to a visible high-pressure sapphire kettle, and an experimental gas of 6.185 MPa is introduced into the visible high-pressure sapphire kettle at a temperature of 275.75 K to carry out an evaluation experiment. It is found that the nucleation time of hydrates in the system is 78 min, indicating that in the evaluation system, due to the presence of the hydrate kinetic inhibitor, the formation of hydrates is significantly inhibited.

[0040] Comparative test example 1 10g of deionized water was added into a visible high-pressure sapphire kettle, and 6.17MPa of experimental gas was introduced into the visible high-pressure sapphire kettle at a temperature of 275.65K to carry out an evaluation experiment. It was found that the nucleation time of hydrates in the system was less than 1min, indicating that in this evaluation system, since no hydrate kinetic inhibitors were added, the formation of hydrates was very rapid.

[0041] Comparative test example 2 10 g of an aqueous solution containing the commercial inhibitor Inhibex 501 (based on the total weight of water, the concentration of the commercial inhibitor Inhibex 501 in the aqueous solution is 0.5 wt %) was added to a visible high-pressure sapphire kettle, and an experimental gas of 6.17 MPa was introduced into the visible high-pressure sapphire kettle at a temperature of 275.65 K for an evaluation experiment. It was found that the nucleation time of hydrates in the system was 21 min, indicating that in this evaluation system, due to the addition of the commercial inhibitor Inhibex501, the formation of hydrates was also inhibited. However, compared with the evaluation system containing the hydrate kinetic inhibitor provided in Example 2 of the present invention in Test Example 1, the nucleation time of hydrates in Test Example 2 was still shorter, which indicates that compared with the existing hydrate kinetic inhibitor Inhibex 501, the hydrate kinetic inhibitor provided in the embodiment of the present invention has a better inhibitory effect on hydrates.

[0042] Comparative test example 3 10g of an aqueous solution containing the commercial inhibitor PVP (based on the total weight of water, the concentration of the commercial inhibitor PVP in the aqueous solution is 0.5wt%) was added to a visible high-pressure sapphire kettle, and an experimental gas of 6.17MPa was introduced into the visible high-pressure sapphire kettle at a temperature of 275.65K for an evaluation experiment. It was found that the nucleation time of hydrates in the system was 6min, indicating that in this evaluation system, the formation of hydrates was also inhibited due to the addition of the commercial inhibitor PVP. However, compared with the evaluation system containing the hydrate kinetic inhibitor provided in Example 2 of the present invention in Test Example 1, the nucleation time of hydrates in Test Example 3 was still shorter, which indicates that compared with the existing hydrate kinetic inhibitor PVP, the hydrate kinetic inhibitor provided in the embodiment of the present invention has a better inhibitory effect on hydrates.

[0043] Comparative test example 4 10 g of an aqueous solution containing the commercial inhibitor Inhibex 501 (based on the total weight of water, the concentration of the commercial inhibitor Inhibex 501 in the aqueous solution is 1.0 wt%) was added to a visible high-pressure sapphire autoclave, and an experimental gas of 6.17 MPa was introduced into the visible high-pressure sapphire autoclave for an evaluation experiment at a temperature of 275.65 K. It was found that the nucleation time of hydrates in the system was 120 min, indicating that in this evaluation system, due to the addition of the commercial inhibitor Inhibex501, the formation of hydrates was also inhibited. However, compared with the evaluation system containing the hydrate kinetic inhibitor provided in Example 2 of the present invention in Test Example 6, the nucleation time of hydrates in Test Example 4 was still shorter, indicating that compared with the existing hydrate kinetic inhibitor Inhibex 501, the hydrate kinetic inhibitor provided in the embodiment of the present invention has a better inhibitory effect on hydrates.

[0044] In summary, compared with existing hydrate kinetic inhibitors, such as PVP, Inhibex 501, etc., the hydrate kinetic inhibitor provided by the present invention has a better inhibitory effect on hydrates, indicating that it has good commercial application prospects.

Claims

1. A hydrate kinetic inhibitor, the structural formula of which is shown in Formula I, In formula I, x:y is 1~9:

1.

2. The hydrate kinetic inhibitor according to claim 1, characterized in that: The relative molecular mass of the hydrate kinetic inhibitor is 1000-50000.

3. A method for preparing the hydrate kinetic inhibitor of formula I according to claim 1 or 2, comprising the following steps: N-vinyl caprolactam and vinyl isobutyl ether are mixed with a solvent, an initiator is added, a binary copolymerization reaction is carried out, and then a terminator is added to obtain the hydrate kinetic inhibitor shown in formula I.

4. The preparation method according to claim 3, characterized in that: The temperature of the binary copolymerization reaction is 323.15~363.15 K, and the reaction time is 5~12h.

5. The preparation method according to claim 3 or 4, characterized in that: The molar ratio of the N-vinyl caprolactam to the vinyl isobutyl ether is 1 to 9:

1.

6. The preparation method according to any one of claims 3 to 5, characterized in that: Taking the total weight of the N-vinyl caprolactam and vinyl isobutyl ether as 100% as the calculation: The dosage of the initiator is 0.01% to 0.5%; the dosage of the terminator is 0.01% to 0.1%; The initiator comprises at least one of azobisisobutyronitrile, dimethyl azobisisobutyrate, azobisisoheptanenitrile and tert-butyl hydroperoxide; The terminator includes styrene and / or methacrylic acid.

7. The preparation method according to any one of claims 3 to 6, characterized in that: The weight ratio of the solvent to the sum of the N-vinyl caprolactam and the vinyl isobutyl ether is 2 to 10:1; The solvent includes at least one of ethanol, isopropanol, N,N-dimethylformamide and n-propanol.

8. Use of the hydrate kinetic inhibitor according to claim 1 or 2 in inhibiting hydrate formation during oil and gas development or transportation.

9. The use according to claim 8, characterized in that: The hydrate kinetic inhibitor is used to inhibit hydrate formation in an oil-gas-water three-phase system or a gas-water two-phase system; The oil-gas-water three-phase system or the gas-water two-phase system has a pressure of 0.2-30 MPa and a temperature of -15°C-30°C.

10. The use according to claim 8 or 9, characterized in that: When the hydrate kinetic inhibitor is used alone, the weight percentage of the hydrate kinetic inhibitor used is 0.5-5.0% based on the total weight of water in the system as 100%.

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