阅读说明：本技术 一种天然气水合物抑制剂的综合评价方法 (Comprehensive evaluation method of natural gas hydrate inhibitor ) 是由 王雷 宋志康 许文俊 叶荣俊 李婷婷 于 2021-07-12 设计创作，主要内容包括：一种天然气水合物抑制剂的综合评价方法,包括以下步骤：S1,准备水合物抑制剂评价装置；S2,将配置好的抑制剂溶液投入反应釜中,打开搅拌器；当反应釜温度稳定至指定的实验温度,将实验气体通入至指定的实验压力；观察实验现象,并用数据采集系统记录实验过程中体系压力、扭矩以及温度数据；S3,通过压力数据计算水合物生成量,判断水合物抑制剂抑制生长性能；将扭矩、温度数据绘制成与时间的关系图,判断水合物抑制剂抑制成核性能。本发明采用水合物生成量和扭矩-温度变化分别评价了含有抑制剂的水合物反应体系的成核和生长阶段,因此能够比较全面的评价水合物抑制成核性能和抑制生长性能,从而能够准确筛选出优良的水合物抑制剂。(A comprehensive evaluation method of a natural gas hydrate inhibitor comprises the following steps: s1, preparing a hydrate inhibitor evaluation device; s2, adding the prepared inhibitor solution into a reaction kettle, and opening a stirrer; when the temperature of the reaction kettle is stabilized to the specified experiment temperature, introducing experiment gas to the specified experiment pressure; observing an experimental phenomenon, and recording system pressure, torque and temperature data in the experimental process by using a data acquisition system; s3, calculating the generation amount of the hydrate through pressure data, and judging the growth inhibition performance of the hydrate inhibitor; and (3) plotting the torque and temperature data into a relation graph with time, and judging the nucleation inhibition performance of the hydrate inhibitor. According to the method, the nucleation and growth stages of the hydrate reaction system containing the inhibitor are respectively evaluated by adopting the generation amount of the hydrate and the torque-temperature change, so that the nucleation inhibition performance and the growth inhibition performance of the hydrate can be comprehensively evaluated, and the excellent hydrate inhibitor can be accurately screened.)

1. The comprehensive evaluation method of the natural gas hydrate inhibitor is characterized by comprising the following steps of:

s1, preparing a hydrate inhibitor evaluation device;

the hydrate inhibitor evaluation device comprises a reaction kettle (7), wherein a methane gas cylinder (1), a pressure regulating valve (2) and a PID valve (3) are sequentially connected and then are connected to an inlet of the reaction kettle (7) through the PID valve (3), a stirrer (6) of the reaction kettle (7) is provided with a torque sensor (5), the torque sensor (5) is used for recording torque data, an outlet of the reaction kettle (7) is provided with a pressure sensor (9) and a temperature sensor (10), and the pressure sensor (9) and the temperature sensor (10) are respectively used for recording pressure and temperature data in the reaction kettle; the torque sensor (5), the pressure sensor (9) and the temperature sensor (10) are connected with a data acquisition system (11);

s2, performing an experiment using the hydrate inhibitor evaluation apparatus by an induction time method:

s201, putting the prepared inhibitor solution into a reaction kettle, vacuumizing air, and adjusting the temperature of a water bath;

s202, when the temperature of the reaction kettle is stabilized to the specified experiment temperature, introducing experiment gas to the specified experiment pressure, and opening the stirrer;

s203, observing an experimental phenomenon, and recording system pressure, torque and temperature data in the experimental process by using a data acquisition system (11);

s3, finishing pressure, temperature and torque data after the experiment:

calculating the generation amount of the hydrate according to the pressure data, and judging the growth inhibition performance of the hydrate inhibitor; and (4) drawing the torque and temperature change data into a relation graph with time, and judging the nucleation inhibition performance of the hydrate inhibitor.

2. The comprehensive evaluation method of a natural gas hydrate inhibitor according to claim 1, wherein in the step S201, the concentration of the hydrate inhibitor solution is not more than 1 wt%.

3. The comprehensive evaluation method of a natural gas hydrate inhibitor according to claim 2, wherein an auxiliary agent such as a cosolvent is added to the hydrate inhibitor solution as required.

4. The method for comprehensively evaluating a natural gas hydrate inhibitor according to claim 1, wherein in the step S202, the test gas is 99.9% methane gas, and may be a mixed gas.

5. The comprehensive evaluation method of a natural gas hydrate inhibitor according to claim 1, wherein in the step S202, the experimental temperature is kept constant within a range of 276.15K-276.45K; the experimental pressure is in the range of 7MPa-7.3 MPa.

6. The comprehensive evaluation method of a natural gas hydrate inhibitor according to claim 1, wherein in step S203, at the later stage of the hydrate reaction, the pressure and the temperature are in a stable state, and at this time, the system pressure is not enough to support the continuous generation of the hydrate, and data needs to be recorded for more than one hour to avoid a large error.

7. The comprehensive evaluation method of a natural gas hydrate inhibitor according to claim 1, wherein the method of calculating the hydrate formation amount from the pressure data in step S3 comprises:

the gas consumption is calculated by calculating the gas consumption after the reaction based on the pressure difference and temperature before and after the reaction, thereby determining the amount of hydrate generated

PV＝nZRT (1)

Gauge pressure, MPa; v is volume, ml; n is the amount of substance, mol; z is gas compression factor, constant; r is constant 8.314J/(mol.k); t is temperature, K;

the amount n of the initial gaseous substance can be obtained from the formula (1)₀The amount of the substance n of the gas remaining after the reaction_tComprises the following steps:

n_t＝n₀-Δn (2)

n_t: the amount of the residual gas substances after the reaction, mol; n is₀: amount of initial gas, mol; Δ n:

amount of reacted gas, mol;

gas is consumed in the reaction process to generate solid hydrate, and the volume of the gas after the reaction is finished is changed;

CH₄+5.75H₂O→CH₄·5.75H₂O (3)

v is volume, ml; m is molecular molar mass, g/mol; n is the amount of substance, mol; ρ: density, g/cm³The density of the hydrate is 0.918g/cm³；

According to the hydrate generation reaction formula (3) and the calculation formula (4), the water volume reduction amount in the hydrate generation process is 103.5 delta n and the hydrate generation amount is 130.17 delta n;

the gas consumption quantity delta n can be obtained according to the volume change equation and the gas state equation (1):

V_{water (W)}+V_{Qi (Qi)}+V_H＝V_{General assembly} (5)

V_{Water (W)}: volume of water after reaction, ml; v_{Qi (Qi)}: volume of remaining gas, ml; v_H: volume of hydrate formed, ml; v_{General assembly}: total volume of the reaction kettle, ml.

8. The method for comprehensively evaluating a natural gas hydrate inhibitor according to claim 1, wherein the torque and temperature data in the step S3 are recorded reaction system torque and temperature data when the stress degree and the heat release effect of the mass nucleation of the hydrate are detected.

Technical Field

The invention belongs to the technical field of hydrates, and particularly relates to a comprehensive evaluation method of a natural gas hydrate inhibitor.

Background

The natural gas hydrate is a non-stoichiometric cage-shaped crystal substance formed by water and small molecular gases such as methane under the conditions of high pressure and low temperature. Gas hydrates are closely related to oil and gas production and transportation, and how to solve the problem that hydrates block oil and gas production mineshafts, ground processing devices and conveying pipelines is always a troublesome problem. Inhibition of the hydrate formation process by the addition of a hydrate inhibitor is an effective means, but currently evaluation of hydrate inhibitor efficacy has not formed a uniform approach.

The performance evaluation of the current hydrate inhibitor generally needs to evaluate the induction time to screen out the inhibitor with better effect, and then the next experiment and application are carried out. However, the traditional evaluation method has many defects. The performance evaluation of the hydrate inhibitor mainly adopts the processing of hydrate nucleation data and growth data, so that the nucleation and growth stages of the hydrate cannot be accurately distinguished and researched. At the same time, the inhibition performance of a hydrate inhibitor cannot be comprehensively evaluated. In detail, if a constant temperature experiment is used for recording the hydrate induction time and the pressure drop curve, and the hydrate inhibition effect of the inhibitor component is evaluated as a key parameter. Obviously, the change of the gas-liquid system cannot be reflected in detail, and the performance of a certain inhibitor cannot be reflected more comprehensively. Therefore, there is a need to establish a more systematic approach to comprehensively evaluate the performance of a hydrate inhibitor.

Disclosure of Invention

In response to the above-identified deficiencies in the art or needs for improvement, the present invention provides an evaluation method for comprehensively evaluating the performance of a hydrate inhibitor. The performance of the hydrate inhibitor is comprehensively evaluated by adopting a pressure drop curve, a hydrate generation amount, a torque and temperature change curve of a gas-liquid system, and the purpose is to more effectively screen out the inhibitor with excellent performance.

In order to achieve the purpose, the invention adopts the technical scheme that:

the comprehensive evaluation method of the natural gas hydrate inhibitor is characterized by comprising the following steps of:

s1, preparing a hydrate inhibitor evaluation device;

the hydrate inhibitor evaluation device comprises a reaction kettle, wherein a methane gas cylinder, a pressure regulating valve and a PID valve are sequentially connected and then are connected to an inlet of the reaction kettle through the PID valve, a stirrer of the reaction kettle is provided with a torque sensor for recording torque data, an outlet of the reaction kettle is provided with a pressure sensor and a temperature sensor, and the pressure sensor and the temperature sensor are respectively used for recording pressure and temperature data in the reaction kettle; the torque sensor, the pressure sensor and the temperature sensor are connected with a data acquisition system;

s2, performing an experiment using the hydrate inhibitor evaluation apparatus by an induction time method:

s201, putting the prepared inhibitor solution into a reaction kettle, vacuumizing air, and adjusting the temperature of a water bath;

s202, when the temperature of the reaction kettle is stabilized to the specified experiment temperature, introducing experiment gas to the specified experiment pressure, and opening the stirrer;

s203, observing an experimental phenomenon, and recording system pressure, torque and temperature data in the experimental process by using a data acquisition system;

s3, finishing pressure, temperature and torque data after the experiment:

calculating the generation amount of the hydrate according to the pressure data, and judging the growth inhibition performance of the hydrate inhibitor; and (4) drawing the torque and temperature change data into a relation graph with time, and judging the nucleation inhibition performance of the hydrate inhibitor.

Further, in the step S201, the concentration of the hydrate inhibitor solution is not more than 1 wt%.

Further, an auxiliary agent such as a cosolvent may be added to the hydrate inhibitor solution as necessary.

Further, in step S202, the test gas may be 99.9% methane gas, or a mixed gas.

Further, in the step S202, the experimental temperature is kept constant in the interval 276.15K-276.45K; the experimental pressure is in the range of 7MPa-7.3 MPa.

Further, in the step S203, at the later stage of the hydrate reaction, the pressure and the temperature are in a stable state, at this time, the system pressure is not enough to support the hydrate to continue to generate, data needs to be recorded for more than one hour, and a large error is avoided.

Further, in step S3, the method for calculating the hydrate formation amount from the pressure data includes:

the gas consumption is calculated by calculating the gas consumption after the reaction based on the pressure difference and temperature before and after the reaction, thereby determining the amount of hydrate generated

PV＝nZRT (1)

Gauge pressure, MPa; v is volume, ml; n is the amount of substance, mol; z is gas compression factor, constant; r is constant 8.314J/(mol.k); t is temperature, K;

the amount n of the initial gaseous substance can be obtained from the formula (1)₀The amount of the substance n of the gas remaining after the reaction_tComprises the following steps:

n_t＝n₀-Δn (2)

n_t: the amount of the residual gas substances after the reaction, mol; n is₀: amount of initial gas, mol; Δ n:

amount of reacted gas, mol;

gas is consumed in the reaction process to generate solid hydrate, and the volume of the gas after the reaction is finished is changed;

CH₄+5.75H₂O→CH₄·5.75H₂O (3)

v is volume, ml; m is molecular molar mass, g/mol; n is the amount of substance, mol; ρ: density, g/cm³The density of the hydrate is 0.918g/cm³；

According to the hydrate generation reaction formula (3) and the calculation formula (4), the water volume reduction amount in the hydrate generation process is 103.5 delta n and the hydrate generation amount is 130.17 delta n;

the gas consumption quantity delta n can be obtained according to the volume change equation and the gas state equation (1):

V_{water (W)}+V_{Qi (Qi)}+V_H＝V_{General assembly} (5)

V_{Water (W)}: volume of water after reaction, ml; v_{Qi (Qi)}: volume of remaining gas, ml; v_H: volume of hydrate formed, ml; v_{General assembly}: total volume of the reaction kettle, ml.

Further, the torque and temperature data in step S3 are the torque and temperature data of the reaction system recorded when the stress degree and the exothermic effect are detected when the hydrate is nucleated in a large amount.

Multiple experiments show that the pressure drop-generation amount and the torque-temperature change of the hydrate can be well matched with the inhibition performance, namely, the more gentle the pressure drop curve is, the lower the generation amount of the hydrate is, and the better the inhibition performance of the inhibitor is; the longer the torque-temperature change occurs corresponds to better performance of the hydrate inhibitor.

Compared with the prior art, the method provided by the invention adopts two evaluation indexes of pressure drop curve-hydrate generation amount and torque-temperature change to respectively evaluate the key indexes of the nucleation and growth stages of the hydrate reaction system containing the inhibitor, so that the nucleation inhibition performance, the growth inhibition performance and the like of the hydrate can be comprehensively evaluated, and the excellent hydrate inhibitor can be accurately screened.

Drawings

FIG. 1 is a schematic view of a hydrate inhibitor evaluation apparatus used in the present invention.

FIG. 2 is a graph of pressure drop for aqueous solutions containing different hydrate inhibitors in accordance with an example of the present invention.

FIG. 3 is a torque-temperature curve of a pure water blank sample in an example of the present invention.

FIG. 4 is a torque-temperature curve of an aqueous solution containing inhibitor A in an example of the present invention.

FIG. 5 is a torque-temperature curve for an aqueous solution containing inhibitor B in an example of the present invention.

FIG. 6 is a torque-temperature curve for an aqueous solution containing inhibitor C in an example of the present invention.

FIG. 7 is a torque-temperature curve for an aqueous solution containing inhibitor D in an example of the present invention.

Wherein: the device comprises a methane gas bottle 1, a pressure regulating valve 2, a PID valve 3, a motor 4, a torque sensor 5, a stirrer 6, a reaction kettle 7, a pressure sensor 9, a temperature sensor 10 and a data acquisition system 11.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

A comprehensive evaluation method of a natural gas hydrate inhibitor comprises the following steps:

s1, preparing a hydrate inhibitor evaluation device;

as shown in fig. 1, the hydrate inhibitor evaluation device comprises a reaction kettle 7, wherein a methane gas cylinder 1, a pressure regulating valve 2 and a PID valve 3 are sequentially connected and then connected to an inlet of the reaction kettle 7 through the PID valve 3, a stirrer 6 of the reaction kettle 7 is provided with a torque sensor 5, the torque sensor 5 is used for recording torque data, an outlet of the reaction kettle 7 is provided with a pressure sensor 9 and a temperature sensor 10, and the pressure sensor 9 and the temperature sensor 10 are respectively used for recording pressure and temperature data in the reaction kettle; the torque sensor 5, the pressure sensor 9 and the temperature sensor 10 are connected with a data acquisition system 11;

s2, performing an experiment using the hydrate inhibitor evaluation apparatus by an induction time method:

s201, putting the prepared inhibitor solution into a reaction kettle, vacuumizing air, and adjusting the temperature of a water bath;

s202, when the temperature of the reaction kettle is stabilized to the specified experiment temperature, introducing experiment gas to the specified experiment pressure, and opening the stirrer;

s203, observing an experimental phenomenon, and recording system pressure, torque and temperature data in the experimental process by using the data acquisition system 11;

s3, finishing pressure, temperature and torque data after the experiment:

calculating the generation amount of the hydrate according to the pressure data, and judging the growth inhibition performance of the hydrate inhibitor; and (4) drawing the torque and temperature change data into a relation graph with time, and judging the nucleation inhibition performance of the hydrate inhibitor. The two are combined to comprehensively evaluate the performance of the hydrate inhibitor.

The main influencing factors for evaluating the effect of the hydrate inhibitor are pressure, temperature and stirring speed, so that the stirring speed is adjusted to the same speed in each experiment.

In the above method for evaluating a hydrate inhibitor, preferably, the torque and temperature data are obtained by: the data were obtained by measuring the friction between the solution containing the hydrate inhibitor and the stirrer and the temperature on the kettle under the conditions of gas hydrate formation. The method of the invention is to measure under the conditions of temperature of 276.15K to 276.45K and pressure of 7.0MPa to 7.3 MPa. In actual practice, the respective conditions may vary depending on the actual conditions and the gas composition.

In the method for evaluating a hydrate inhibitor, an induction time method is preferably used.

In the method for evaluating a hydrate inhibitor, the gas used is preferably 99.9% methane gas, and may be a mixed gas.

In the above evaluation method of a hydrate inhibitor, it is preferable that the concentration of the hydrate inhibitor in the solution containing the hydrate inhibitor is generally not more than 1% by weight.

In the above-described method for evaluating a hydrate inhibitor, an auxiliary agent such as a cosolvent may be added to the solution containing the hydrate inhibitor as necessary, but the consistency of the comparison conditions needs to be taken into consideration.

In a preferred embodiment of the method for evaluating a hydrate inhibitor according to the present invention, the step of measuring the hydrate formation amount by an induction time method comprises:

the method comprises the following steps: and quickly cooling the hydrate reaction system to a specified experimental temperature, keeping the temperature unchanged in an interval of 276.15K-276.45K, opening a PID valve, starting a stirrer, and introducing methane gas to a specified experimental pressure interval of 7MPa-7.3 MPa.

Step two: and in the later stage of the hydrate reaction, the pressure and the temperature are in a stable state, the system pressure is not enough to support the continuous generation of the hydrate, the record is carried out for more than 1 hour, and a large error is avoided.

Step three: in order to reduce experimental error, the experiment is preferably repeated for 3 times;

step four: and processing the acquired pressure data to obtain hydrate formation data.

In a preferred embodiment provided by the present invention, when the pressure drop data is processed, the calculation method of the hydrate formation amount is:

the gas consumption is calculated by calculating the gas consumption after the reaction based on the pressure difference and temperature before and after the reaction, thereby determining the amount of hydrate generated

PV＝nZRT (1)

Gauge pressure, MPa; v is volume, ml; n is the amount of substance, mol; z is gas compression factor, constant; r is constant 8.314J/(mol.k); t is temperature, K;

the amount n of the initial gaseous substance can be obtained from the formula (1)₀The amount of the substance n of the gas remaining after the reaction_tComprises the following steps:

n_t＝n₀-Δn (2)

n_t: the amount of the residual gas substances after the reaction, mol; n is₀: amount of initial gas, mol; Δ n: amount of reacted gas, mol;

gas is consumed in the reaction process to generate solid hydrate, and the volume of the gas after the reaction is finished is changed;

CH₄+5.75H₂O→CH₄·5.75H₂O (3)

v is volume, ml; m is molecular molar mass, g/mol; n is the amount of substance, mol; ρ: density, g/cm³The density of the hydrate is 0.918g/cm³；

According to the hydrate generation reaction formula (3) and the calculation formula (4), the water volume reduction amount in the hydrate generation process is 103.5 delta n and the hydrate generation amount is 130.17 delta n;

the gas consumption quantity delta n can be obtained according to the volume change equation and the gas state equation (1):

V_{water (W)}+V_{Qi (Qi)}+V_H＝V_{General assembly} (5)

V_{Water (W)}: volume of water after reaction, ml; v_{Qi (Qi)}: volume of remaining gas, ml; v_H: volume of hydrate formed, ml; v_{General assembly}: total volume of the reaction kettle, ml.

Preferably, the torque-temperature of the hydrate inhibitor screening method is obtained according to the following method. The specific operation is as follows:

(1) and quickly cooling the hydrate reaction system to a specified temperature and keeping the temperature unchanged, opening the PID valve, starting the stirrer, and introducing methane gas to a specified pressure.

(2) And (2) detecting the friction effect and the heat release effect of the hydrate reaction system obtained in the step (1) when a large amount of hydrates nucleate, and recording the torque and temperature data of the reaction system.

Experiments prove that the hydrate inhibitor evaluation method provided by the invention is effective not only on a single hydrate inhibitor, but also on a compound hydrate inhibitor.

The following are examples:

a hydrate inhibitor evaluation method comprising the steps of:

(1) the four hydrate inhibitors A, B, C, D to be evaluated are respectively prepared into 1 wt% inhibitor solution with the same concentration, and a pure water system of the methane natural gas hydrate to be inhibited is added to prepare an inhibitor-methane natural gas reaction system, wherein the inhibitor A, C is a single inhibitor, and the inhibitor B, D is a compound inhibitor.

(2) And (2) obtaining a pressure drop curve of the inhibitor-methane natural gas hydrate for the hydrate reaction system prepared in the step (1), and calculating the generation amount of the hydrate, wherein the specific process is as follows:

the hydrate formation amount is obtained according to the following method: and (3) collecting pressure drop data by adopting a constant temperature method, and calculating according to formulas (1), (2), (3), (4) and (5) to obtain the generation amount.

(3) Acquiring torque data and temperature data of the inhibitor-methane natural gas hydrate for the hydrate reaction system prepared in the step (1), wherein the specific process is as follows:

and processing the torque and temperature change curves of the hydrate inhibitor solution, and combining comparison to obtain a torque-temperature comprehensive curve.

Wherein, each group of hydrate inhibitor evaluation experiment needs a plurality of experiments, and experimental accidental errors are avoided.

The pressure drop curve of the hydrate inhibitor is shown in fig. 2, the four inhibitors are all tested under the conditions that the test temperature is 3-3.3 ℃ and the initial pressure is 7-7.3 MPa, and the results are shown in table 1:

TABLE 1 growth inhibitory Effect of four hydrate inhibitors

The growth inhibition performance requirements are as follows: under the given temperature and pressure conditions, except for the pressure drop caused by the dissolution of methane gas in the inhibitor solution in a short time, the inhibitor has obvious no pressure drop stage, and 1 wt% B and 1 wt% D meet the growth inhibition performance requirement.

Solution temperature and torque data are sequentially collected for four inhibitor-methane natural gas hydrate reaction systems, and are collated and compared, as shown in fig. 4-7, and the results of multiple groups of repeated experiments are shown in table 2:

TABLE 2 nucleation inhibition Effect of four hydrate inhibitor solutions

The nucleation inhibition performance requirements are as follows: the longer the torque and temperature ramp time under given temperature and pressure conditions, the better the nucleation inhibition, and the result shows that inhibitor B, D at a concentration of 1 wt% has good nucleation inhibition.

Combining the data of table 1 and fig. 3, it can be found that: the torque-temperature change and pressure drop-hydrate formation can be mutually adjuvanted. The longer the torque-temperature mutation occurs, the longer the time to inhibit hydrate growth; likewise, the lower the pressure drop-hydrate formation value, the longer the nucleation inhibition time of the hydrate inhibitor.

The embodiment comprises a single-type inhibitor A, C and a compound-type inhibitor B, D, and the reliability of the performance evaluation method of the hydrate inhibitor can be verified through the data analysis.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiment according to the technical spirit of the present invention are within the scope of the technical solution of the present invention without departing from the technical solution of the present invention.

Details not described in this specification are within the skill of the art that are well known to those skilled in the art.