A method for continuously monitoring whether the asphaltene precipitated from high-temperature crude oil can redissolve

Abstract

The present invention discloses an experimental method for continuously monitoring whether the precipitated asphaltene in high-temperature crude oil redissolves, which relates to the field of oil and gas resource development. The specific steps are as follows: First, through crude oil purification and asphaltene sample purification, relatively clean crude oil without impurities and relatively pure asphaltene are obtained; then the purified asphaltene is wrapped with a sieve mesh and suspended in a container filled with crude oil. A magnetic rotor is placed in the container, the rotation speed is set to 10 r / s, and the temperature of the constant temperature water bath is set to 60 °C; finally, samples are taken every 2 days in the first 10 days, and then every 5 days thereafter. Each time 5 g of samples are taken for continuous separation experiments to obtain the asphaltene content in the crude oil, and multiple groups are measured to observe the dynamic changes of the asphaltene content to judge whether the asphaltene redissolves.

Description

Technical Field

[0001] The present invention relates to the field of oil and gas resource development, and particularly to a method for continuously monitoring whether precipitated asphaltene in high-temperature crude oil redissolves. Background Art

[0002] Asphaltene is a component with the largest molecular weight and the strongest polarity in crude oil. When factors such as temperature, pressure, or composition in the crude oil change, the dynamic stability system of asphaltene is disturbed or even destroyed, resulting in the precipitation, aggregation, and deposition of asphaltene. This can cause blockages in downhole wellbores, production tubing, and related instruments and equipment. Asphaltene blockages reduce the wellhead pressure, cause accidents such as stuck testing tools, significantly reduce the single-well production capacity, and even lead to well shutdown and major repair operations. Oilfield enterprises often need to spend a large amount of manpower, financial resources, and time to deal with them, increasing the oil and gas development costs and reducing the development efficiency of the oilfield.

[0003] Only in 2018 - 2019, there were 16 well times of asphaltene blockages in the wellbores of the Shunbei Oil and Gas Field in the Tarim Basin, Xinjiang, accounting for one-fourth of the entire oilfield block, seriously affecting the efficient development of the oil and gas field.

[0004] Currently, the influencing factors and precipitation laws of asphaltene are not clearly understood, and the prevention and control technologies in the oilfield field are weak. In the process of studying the precipitation law of crude oil asphaltene, the conclusion of whether the precipitated asphaltene can redissolve into the crude oil at high temperature and high pressure, that is, whether the asphaltene precipitation phenomenon is reversible, directly determines the correctness of the next research method and route. However, for whether asphaltene can redissolve, there are no relevant experiments on actual oil samples in the oilfield field, nor are there experimental methods to verify this conclusion.

[0005] However, there have been studies on the solubility of asphaltene. For example, the asphalt rejuvenator diffusion test device and test method in Chinese Patent Application No. 201510897570.X aim to solve the problem that the existing experimental devices and evaluation methods for asphalt rejuvenator diffusion are not efficient and accurate enough. The test device includes a dissolution barrel, a sample holder, a collection device, a liquid inlet pipe, and a liquid outlet pipe. The test method is to first let the asphalt sample added with the rejuvenator stand, weigh the asphalt sample and measure the height of the sample, add trichloroethylene for asphalt cleaning, and then repeat the cleaning process multiple times, measure the four components of the discharged liquid solid matter, calculate the relative content of the rejuvenator, and then obtain the diffusion rate of the rejuvenator through the diffusion depth. This invention utilizes the large solubility of trichloroethylene in asphalt and adopts a layered dissolution method to gradually dissolve the asphalt sample treated with the rejuvenator, and then analyzes the diffusion characteristics of the rejuvenator based on the analysis results of the components of the dissolved solution.

[0006] For another example, a device for measuring the solubility of asphaltene disclosed in Chinese Patent Application No. 201420561679.7 includes a dissolution system, a stirring system, and a constant temperature system. Among them, the dissolution system includes a container, a scale, and a liquid dispenser. The stirring system is used to stir the solution in the container, and the constant temperature system is used to provide a constant temperature environment for the container. The test device for measuring the solubility of asphaltene in organic solvents provided by this utility model can measure the solubility of asphaltene in heavy oil at different temperatures in organic solvents. The instrument is simple, easy to operate, and has the advantages of small device volume, accurate experiment, and simple evaluation process.

[0007] However, there is no research on whether the precipitated asphaltene from crude oil redissolves. Considering the actual problems encountered in the research process, an experimental method for verifying whether the precipitated asphaltene from crude oil redissolves is designed. Therefore, there is an urgent need for a method to continuously monitor whether the precipitated asphaltene from high-temperature crude oil redissolves, which can test whether the precipitated asphaltene from crude oil redissolves under high-temperature and high-pressure conditions, further study the precipitation law of crude oil asphaltene, and thus provide technical support for guiding the stable production of oil and gas fields on site. Summary of the Invention

[0008] Aiming at the defects existing in the prior art, the present invention aims to provide a method for continuously monitoring whether the precipitated asphaltene from high-temperature crude oil redissolves, providing a basis and support for determining the research method of asphaltene dissolution and redissolution laws.

[0009] To achieve the above technical solution, the present invention provides a method for continuously monitoring whether the precipitated asphaltene from high-temperature crude oil redissolves, and the method includes two parts: calibration of the asphaltene content in high-temperature crude oil and continuous monitoring method of asphaltene redissolution.

[0010] A method for continuously monitoring whether the precipitated asphaltene from high-temperature crude oil redissolves includes the following steps:

[0011] 1. Calibration of the asphaltene content in high-temperature crude oil

[0012] The calibration of the asphaltene content in high-temperature crude oil is to obtain the initial asphaltene content of high-temperature crude oil without impurity interference, providing a comparison parameter for the subsequent asphaltene dissolution data of continuous monitoring. The specific steps are as follows

[0013] 1-1. Take a certain amount of crude oil in a beaker, stir it evenly and filter it multiple times to remove the solid-phase impurities in the sample, and finally obtain the filtered crude oil;

[0014] 1-2. Heat n-heptane to boiling, and then add the boiling n-heptane to the filtered crude oil obtained in step 1-1 to dissolve the saturates, aromatics, and resins in the crude oil sample. After full dissolution, filter the fully dissolved solution to obtain a filtrate and a small amount of insoluble matter;

[0015] 1-3. Use toluene and a Soxhlet extractor to separate and extract the insoluble matter in Step 1-2 to obtain asphaltene. The mass of the obtained asphaltene is the asphaltene content in the crude oil used in the experiment.

[0016] 2. Continuous monitoring method for asphaltene redissolution

[0017] The following steps are all measured under the high-temperature conditions provided by a DF-101S thermostatic heating magnetic stirrer.

[0018] 2-1. Crude oil purification: Filter the crude oil to remove impurities and place it in a container.

[0019] 2-2. Asphaltene sample purification: Since the asphaltene sample taken on-site contains other impurities, it needs to be purified. In accordance with the four-component separation standard, dissolve the asphaltene sample containing impurities provided on-site with n-heptane according to the operation in Step 1-2, and then extract it with toluene according to the operation in Step 1-3. After drying the solvent, relatively pure asphaltene is obtained.

[0020] 2-3. Wrap the relatively pure asphaltene obtained in Step 2-2 with a sieve mesh and hang it in the container containing the crude oil in Step 2-1.

[0021] 2-4. Place a magnetic rotor in the container, set the rotation speed, and perform a constant-temperature water bath.

[0022] 2-5. Take the crude oil once every 2 days for the first 10 days, and then take the crude oil once every 5 days for subsequent separation experiments to achieve the purpose of continuous monitoring.

[0023] 2-6. Weigh the asphaltene content in the crude oil with an electronic balance, measure multiple groups, and observe the dynamic change of the asphaltene content to determine whether the asphaltene is redissolved.

[0024] The filtration mentioned in Step 1-1 above is through a 600-mesh sieve.

[0025] The mass ratio of the filtered crude oil to n-heptane in Step 1-2 above is 1:50.

[0026] The filtration mentioned in Step 2-1 above is through a 600-mesh sieve.

[0027] The sieve mesh mentioned in Step 2-3 above is a 600-mesh sieve.

[0028] The rotation speed mentioned in Step 2-4 above is 10 r / s, and the water bath temperature is 60 °C.

[0029] Specifically, a method for continuously monitoring whether the asphaltene precipitated from high-temperature crude oil is redissolved includes the following steps:

[0030] 1. Calibration of asphaltene content in high-temperature crude oil

[0031] The calibration of the asphaltene content in high-temperature crude oil is to obtain the initial asphaltene content of high-temperature crude oil under the condition of no impurity interference, and provide a comparison parameter for the asphaltene dissolution data of subsequent continuous monitoring. The specific steps are as follows

[0032] 1-1. Take a certain amount of crude oil in a beaker, stir it evenly, and filter it through a 600-mesh sieve multiple times to remove the solid impurities in the sample, and finally obtain the filtered crude oil;

[0033] 1-2. After heating n-heptane to boiling, then add the boiling n-heptane to the filtered crude oil obtained in step 1-1 according to a mass ratio of 50:1 to dissolve the saturates, aromatics and resins in the crude oil sample. After sufficient dissolution, filter the fully dissolved solution to obtain a filtrate and a small amount of insoluble substances;

[0034] 1-3. Use toluene and a Soxhlet extractor to separate and extract the insoluble substances in step 1-2 to obtain asphaltene, and the mass of the obtained asphaltene is the asphaltene content in the crude oil used in the experiment.

[0035] 2. Continuous monitoring method for asphaltene back-dissolution

[0036] The following steps are all measured under the high-temperature conditions provided by a DF-101S thermostatic heating magnetic stirrer with a heating mantle.

[0037] 2-1. Crude oil purification: Take the crude oil, filter it through a 600-mesh sieve to remove impurities, and then put it in a glass bottle;

[0038] 2-2. Asphaltene sample purification: Since the asphaltene sample taken on site contains other impurities, it needs to be purified. According to the four-component separation standard, use n-heptane to fully dissolve the asphaltene sample containing impurities provided on site according to the operation in step 1-2, and then extract it with toluene according to the operation in step 1-3. After drying the solvent, relatively pure asphaltene is obtained.

[0039] 2-3. Wrap the relatively pure asphaltene obtained in step 2-2 with a 600-mesh sieve and hang it in the glass bottle containing the crude oil in step 2-1;

[0040] 2-4. Put a magnetic rotor in the glass bottle, set the rotation speed to 10 r / s, and carry out a constant-temperature water bath at a temperature of 60 °C;

[0041] 2-5. Take the crude oil once every 2 days in the first 10 days, and then take the crude oil once every 5 days for separation experiments to achieve the purpose of continuous monitoring;

[0042] 2-6. Weigh the asphaltene content in the crude oil with an electronic balance, measure multiple groups, and observe the dynamic change of the asphaltene content to judge whether the asphaltene is back-dissolved.

[0043] The beneficial effects of the present invention are:

[0044] The present invention provides a method for continuously monitoring whether asphaltene precipitated from high-temperature crude oil is re-dissolved, providing a basis and support for determining the research method of asphaltene law. It fills the gap that there is no method for continuously monitoring whether asphaltene precipitated from high-temperature crude oil is re-dissolved, and provides technical support for guiding the stable production of oil and gas fields.

[0045] (1) The present invention designs crude oil purification during the operation process, realizes the purification of the solvent, ensures that the experimental results are not interfered by impurities, and are closer to the actual situation on site;

[0046] (2) The present invention designs asphaltene sample purification during the operation process, ensuring that the experimental results are not affected by paraffin impurities, making the asphalt dissolution results more accurate;

[0047] (3) The present invention uses a magnetic rotor during the dissolution process to ensure the dissolution effect;

[0048] (4) The present invention controls the rotation speed to 10 r / s during the dissolution process, and ensures the stability of the experimental data according to the characteristics of asphalt;

[0049] (5) The present invention controls the temperature of the constant temperature water bath to 60° C. during the dissolution process to ensure the constancy of the dissolution temperature;

[0050] (6) The present invention designs multiple groups of experiments in the process of rubbing the even-even pairs to reduce the uncertainty caused by experimental errors as much as possible, making the experimental data reliable and increasing its comparability. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 Dynamic change of asphaltene content over time in the embodiment of the present invention DETAILED DESCRIPTION

[0052] Experimental instruments and drugs:

[0053] 1) Instruments: DF-101S heat-collecting constant temperature heating magnetic stirrer was purchased from Shanghai Lingke Company; DZTW constant temperature electric heating jacket was purchased from Tianjin Gongxing Company; Soxhlet extractor was purchased from Shuniu Glass Instrument Factory, 150 ml; glass bottle was purchased from Shuniu Glass Instrument Factory, specification is 250 ml; 600 mesh filter was purchased from Tairun Wire Mesh Manufacturing Co., Ltd.; beaker was purchased from Shuniu Glass Instrument Factory, specification is 250 ml;

[0054] 2) Drugs: n-heptane analytical grade AR, toluene analytical grade AR, and crude oil from a well in Shunbei Oil and Gas Field.

[0055] Embodiment A method for continuously monitoring whether asphaltene precipitated from high-temperature crude oil is dissolved again comprises the following steps:

[0056] 1. Calibration of Asphaltene Content in High-Temperature Crude Oil

[0057] 1-1. Take a certain amount of crude oil in a beaker, stir it evenly, and filter it through a 600-mesh sieve multiple times to remove solid impurities in the sample, and finally obtain 100 mL of filtered crude oil;

[0058] 1-2. After heating n-heptane to boiling, then add the boiling n-heptane to the filtered crude oil obtained in step 1-1 at a ratio of 50:1 to dissolve the saturates, aromatics, and resins in the crude oil sample. After sufficient dissolution, filter the fully dissolved solution to obtain a filtrate and a small amount of insoluble matter;

[0059] 1-3. Use toluene and a Soxhlet extractor to separate and extract the insoluble matter in step 1-2 to obtain 1.37 g of asphaltene, that is, the asphaltene content of the crude oil from a certain well in Shunbei used in the experiment is calibrated to be 1.37%;

[0060] 2. Continuous Monitoring Method for Asphaltene Redissolution

[0061] 2-1. Purification of crude oil: Take 400 mL of crude oil, filter it through a 600-mesh sieve to remove impurities, and then put it in a glass bottle;

[0062] 2-2. Purification of asphaltene sample: Since the asphaltene sample taken on-site contains other impurities, it needs to be purified. According to the four-component separation standard, use n-heptane to fully dissolve the asphaltene sample containing impurities provided on-site according to the operation in step 1-2, and then extract it with toluene according to the operation in step 1-3. After drying the solvent, obtain relatively pure asphaltene;

[0063] 2-3. Wrap the relatively pure asphaltene obtained in step 2-2 with a 600-mesh sieve and hang it in the glass bottle containing crude oil in step 2-1;

[0064] 2-4. Place a magnetic rotor in the glass bottle, set the rotation speed to 10 r / s, and perform a constant-temperature water bath at a temperature of 60 °C;

[0065] 2-5. Take the crude oil every 2 days in the first 10 days, and then take the crude oil every 5 days, 5 g each time, for separation experiments to achieve the purpose of continuous monitoring;

[0066] 2-6. Weigh the asphaltene content in the crude oil with an electronic balance, measure multiple groups, and observe the dynamic change of the asphaltene content to judge whether the asphaltene can redissolve.

[0067] The specific test results are shown in the appendix Figure 1 , from Figure 1 It can be seen that there are weak dynamic fluctuations in the asphaltene content measured in the experiment for more than 70 days, but the overall is close to the initial asphaltene content, and there is no obvious evidence to prove that the asphaltene can redissolve.

[0068] Therefore, it can be concluded from this experiment that it is difficult for the asphaltene in Shunbei crude oil to redissolve or there is a very small part of redissolution. Using this method, it is found that the asphaltene precipitated from the crude oil in the Shunbei oil and gas field at 60 °C can hardly redissolve in the crude oil again.

Claims

1. A method for continuously monitoring whether the precipitated asphaltene in high-temperature crude oil redissolves, characterized in that: The method includes two parts: the calibration of the asphaltene content in high-temperature crude oil and the continuous monitoring method of asphaltene redissolution; The calibration of the asphaltene content in high-temperature crude oil specifically includes the following steps: 1-1. Filter the crude oil to remove solid impurities to obtain the filtered crude oil; 1-2. Heat n-heptane to boiling, add the boiling n-heptane to the filtered crude oil obtained in step 1-1, dissolve the saturates, aromatics and resins in the crude oil sample. After sufficient dissolution, filter the fully dissolved solution to obtain a filtrate and a small amount of insoluble matter; 1-3. Use toluene and a Soxhlet extractor to separate and extract the insoluble matter in step 1-2 to obtain asphaltene. The mass of the obtained asphaltene is the asphaltene content in the crude oil used in the experiment.

2. The method according to claim 1, wherein: The continuous monitoring method of asphaltene redissolution specifically includes the following steps: 2-1. Crude oil purification: Take the crude oil after filtering out impurities and place it in a container; 2-2. Asphaltene sample purification: Since the asphaltene sample taken on-site contains other impurities, it needs to be purified; According to the four-component separation standard, use n-heptane to fully dissolve the asphaltene sample containing impurities provided on-site according to the operation in step 1-2, and then extract it with toluene according to the operation in step 1-3. After drying the solvent, relatively pure asphaltene is obtained; 2-3. Wrap the relatively pure asphaltene obtained in step 2-2 with a sieve mesh and hang it in the container containing the crude oil in step 2-1; 2-4. Place a magnetic rotor in the container, set the rotation speed, and perform a constant temperature water bath; 2-5. Take the crude oil every 2 days in the first 10 days and then every 5 days for separation experiments to achieve the purpose of continuous monitoring; 2-6. Weigh the asphaltene content in the crude oil with an electronic balance, measure multiple groups, and observe the dynamic change of the asphaltene content to judge whether the asphaltene redissolves.

3. The method according to claim 1, wherein: The filtration described in step 1-1 is through a 600-mesh sieve; 4. The method according to claim 1, characterized in that: The mass ratio of the filtered crude oil to n-heptane described in step 1-2 is 1:50; 5. The method according to claim 2, characterized in that: The filtration described in step 2-1 is through a 600-mesh sieve; 6. The method according to claim 2, wherein: The sieve mesh described in step 2-3 is a 600-mesh sieve; 7. The method according to claim 2, characterized in that: The rotation speed described in step 2-4 is 10 r / s; 8. The method according to claim 2, wherein: The water bath temperature described in step 2-4 is 60 °C.

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