Dynamic detection method for moisture content of emulsified oil

Abstract

The invention discloses a dynamic detection method for the water content of emulsified oil. Comprising the following steps: (1) field calibration: carrying out oil-water separation on emulsified oil, respectively measuring M (n) oil and M (n) water, and calculating to obtain a hydrogen content index HI oil = M (n) oil / M (n) water of the oil; (2) real-time measurement: dividing the fluid in the emulsified oil pipeline into n layers in the direction vertical to the flowing direction of the fluid, performing layered scanning by using a magnetic resonance probe, acquiring the maximum amplitude M (n) of FID (Flame Ionization Detector) of each layer, and calculating the water content eta (n) of each layer according to the formula M (n) = eta (n) * M (n) water / n + [1-eta (n)] M (n) water * HI oil / n; and (3) the dynamic moisture content is calculated according to eta = eta (1) * S (1) + eta (2) * S (2) +... + eta (n) * S (n), n is an integer selected from 2-15, and rapid, green and non-invasive testing of the moisture content of the emulsified oil is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of on-line water content detection of emulsified oil, and particularly relates to a dynamic detection method for the water content of emulsified oil. Background Technique

[0002] In the petroleum industry, with the increasing depletion of conventional oil and gas resources and the in-depth development of unconventional oil and gas resources, the underground fluids faced in the field of oil drilling and production engineering are mainly oil-water two-phase mixed fluids. Among them, shale oil and heavy oil, as important unconventional oil and gas resources, have very serious emulsification phenomena and are in the state of water-in-oil and oil-in-water in pipelines for a long time, which brings great difficulties to oil and gas metering and laboratory testing. Separation metering technology: Conventional phase separation technologies (such as relying on natural stratification or mechanical device-assisted stratified three-phase separators) cannot achieve perfect separation of the oil phase and the water phase, which brings difficulties to the next step of on-line oil-water metering and laboratory testing using a single-phase flowmeter; Sampling and laboratory testing technology: After sampling and standing for a period of time, wait for the oil and water to stratify and then read the preliminary water content. Then, further use a demulsifier to demulsify the oil-water mixed fluid, and then measure the oil and water content of the treated fluid to correct the preliminary water content data. From the above two types of emulsified oil water content testing methods used on-site, it can be seen that the most reliable method for emulsified oil water content testing is the sampling and laboratory testing technology.

[0003] The existing sampling and laboratory testing technology for the water content of emulsified oil has many deficiencies:

[0004] (1) Low accuracy: ① It often takes a period of time to sample and send it to a professional laboratory for testing. During this process, the physical properties of the fluid are greatly affected by the external environmental temperature, pressure, and vibration, and will change significantly; ② During the testing process, the demulsification process cannot ensure the complete separation of oil and water, and parameter correction itself will introduce errors; ③ The human influence factor is large, the operation process is cumbersome, and human errors will be introduced;

[0005] (2) Low efficiency and long sampling period. Due to the long testing time and high cost, the highest sampling frequency is also more than 2 hours. A large sampling interval cannot fully reflect the real-time dynamic changes of the oil well.

[0006] (3) Additional labor costs. The sampling and testing processes both require professional personnel to operate, resulting in high labor costs.

[0007] (4) Sample pollution. Chemical reagents such as demulsifiers are added during the sample testing process, which will pollute the sample. The tested sample needs to be detoxified, resulting in additional costs. There is an urgent need for an efficient, accurate, green, and safe measurement method.

[0008] The testing of the water content of emulsified oil is a difficult problem that plagues the petroleum industry and the progress is slow.

[0009] Low-field nuclear magnetic resonance technology is currently a mainstream indoor fluid component analysis technology. Its advantages lie in non-invasive, green, environmentally friendly, efficient and accurate measurement methods. Applying it to the industrial site for on-line analysis of emulsified oil has good prospects. However, in the actual application of low-field nuclear magnetic resonance technology for the moisture content test of emulsified oil, it is mainly the traditional static sampling and testing method. The on-line testing measurement process is slow and the accuracy is low, which hinders the production process. Summary of the Invention

[0010] The purpose of the present invention is to overcome the problems existing in the prior art that the dynamic moisture content test process of emulsified oil by low-field nuclear magnetic resonance technology is slow and the accuracy is low, and to provide a dynamic detection method for the moisture content of emulsified oil.

[0011] In order to achieve the above object, the first aspect of the present invention provides a dynamic detection method for the moisture content of emulsified oil, which includes the following steps:

[0012] (1) On-site calibration: Separate the emulsified oil into oil and water, and measure the maximum amplitudes of FID of pure oil and pure water respectively, namely M(n) 油 and M(n) 水 , and calculate the hydrogen index HI of the oil 油 =M(n) 油 / M(n) 水 ;

[0013] (2) Real-time measurement: Divide the fluid in the emulsified oil pipeline into n layers in the direction perpendicular to the fluid flow direction, use a magnetic resonance probe for layered scanning, collect the maximum amplitude M(n) of FID for each layer, and calculate the moisture content η(n) of each layer according to M(n)=η(n)×M(n) 水 / n+[1-η(n)]M(n) 水 ×HI 油 / n;

[0014] (3) Calculate the dynamic moisture content according to η=η(1)×S(1)+η(2)×S(2)+…+η(n)×S(n), where S(n) is the proportion of the volume of the nth layer in the total volume;

[0015] where n is an integer selected from 2 to 15.

[0016] Through the above technical solutions, the present invention provides a dynamic detection method for the moisture content of emulsified oil, which realizes the application of low-field nuclear magnetic resonance fluid detection technology to the industrial measurement site, can perform dynamic measurement of the moisture content test of emulsified oil by using low-field nuclear magnetic resonance technology, only needs to calibrate to obtain the hydrogen index HI of the oil 油 , then collect the maximum amplitude M(n) of FID through layered scanning, and through M(n)=η(n)×M(n) 水 / n+[1-η(n)]M(n)水 ×HI 油 / n Calculate the moisture content η(n) of each layer, and then calculate the dynamic moisture content in combination with η = η(1)×S(1) + η(2)×S(2) + … + η(n)×S(n), realizing the fast, green, non-invasive, and full-range testing of the moisture content of emulsified oil, providing a complete set of testing schemes including sampling methods, measurement methods, calibration methods, and sample post-treatment methods, and facilitating the accurate and fast testing of the moisture content of emulsified oil. Description of the Drawings

[0017] Figure 1 It is a schematic diagram of horizontal pipe stratified scanning. Detailed Embodiments

[0018] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0019] The first aspect of the present invention provides a method for dynamically detecting the moisture content of emulsified oil, which includes the following steps:

[0020] (1) On-site calibration: Separate the oil and water in the emulsified oil, and measure the maximum FID amplitudes of pure oil and pure water, namely M(n) 油 and M(n) 水 , and calculate the hydrogen index HI of the oil 油 = M(n) 油 / M(n) 水 ;

[0021] (2) Real-time measurement: In the direction perpendicular to the fluid flow direction, divide the fluid in the emulsified oil pipeline into n layers, use a magnetic resonance probe for stratified scanning, collect the maximum FID amplitude M(n) for each layer, and calculate the moisture content η(n) of each layer according to M(n) = η(n)×M(n) 水 / n + [1 - η(n)]M(n) 水 ×HI 油 / n;

[0022] (3) Calculate the dynamic moisture content according to η = η(1)×S(1) + η(2)×S(2) + … + η(n)×S(n), where S(n) is the proportion of the volume of the nth layer in the total volume;

[0023] where n is an integer selected from 2 - 15, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15.

[0024] In the present invention, a method for dynamically detecting the water content of emulsified oil is provided. Different from the existing methods, the water content measurement is completed under the state of continuous and high-speed fluid flow, realizing the application of low-field nuclear magnetic resonance fluid detection technology to the industrial metrology site. It can use low-field nuclear magnetic resonance technology to dynamically determine the water content of emulsified oil, achieving rapid, green, non-invasive, and full-range testing of the water content of emulsified oil, providing a complete set of testing schemes including sampling methods, measurement methods, calibration methods, and sample post-treatment methods, and facilitating the accurate and rapid testing of the water content of emulsified oil.

[0025] In some specific embodiments of the present invention, preferably, n is an integer selected from 10 to 15.

[0026] In some specific embodiments of the present invention, in step (2), the measurement method of S(n) is as follows: For example, when n = 4, that is, scanning is performed in 4 layers, with each layer having a height h, and S(1) to S(4) are calculated.

[0027] S(2) = S(3) = [arcsin(h / r) * πr2 / 360 + (r2 - h2)1 / 2 * h / 2] * v;

[0028] S(1) = S(4) = [πr2 / 2 - arcsin(h / r) * πr2 / 360 + (r2 - h2)1 / 2 * h / 2] * v;

[0029] Wherein, r is the pipe radius and v is the fluid flow rate.

[0030] In some specific embodiments of the present invention, the method further includes: before the measurement, preheating the nuclear magnetic resonance probe to a temperature close to that of the emulsified oil fluid.

[0031] In some specific embodiments of the present invention, in step (1), before separating the oil and water of the emulsified oil, sampling is first performed, and the sample is sampled into a sample tube. The sampling method is selected from atmospheric pressure sampling or pressure-maintaining sampling.

[0032] In some specific embodiments of the present invention, in step (1), the oil-water separation method is static treatment, and the temperature of the static treatment is maintained within the range of ±5°C of the temperature at the wellhead where the emulsified oil is produced. For example, when the temperature at the wellhead where the emulsified oil is produced is 80°C, the temperature of the static treatment is maintained at 80°C ± 5°C; when the temperature at the wellhead where the emulsified oil is produced is 30°C, the temperature of the static treatment is maintained at 30°C ± 5°C. Maintaining the temperature of the static treatment at the temperature at the wellhead where the emulsified oil is produced helps to completely separate the oil and water, obtain pure oil and pure water phases, ensure the accuracy of measurement. At the same time, the magnetic field intensity of the magnetic resonance magnet is different at different temperatures, and the signal intensity obtained is also different. Maintaining the temperature of the static treatment at the temperature at the wellhead where the emulsified oil is produced can thus perform on-site calibration more accurately.

[0033] In some specific embodiments of the present invention, in step (1), the volumes of the pure oil and pure water to be measured are the same.

[0034] In some specific embodiments of the present invention, the method further includes: before performing the layer scanning in step (2), installing the magnetic resonance device to the pipe orifice to be measured, so that the emulsified oil fluid to be measured completes the layer scanning during the continuous flow through the magnetic resonance probe.

[0035] In some specific embodiments of the present invention, in step (2), the layer scanning method is static magnetic field gradient combined with antenna frequency modulation or gradient coil combined with antenna frequency modulation.

[0036] In some specific embodiments of the present invention, the two parameters of M(n) water and HI oil need to be obtained through on-site calibration, and only one calibration is required before the dynamic scanning. In step (1), after the oil-water separation, a CPMG pulse sequence is continuously emitted to the obtained oil phase, and the T2 spectrum is inversely obtained in real time. When the T2 spectrum shows only a single oil peak, it indicates that the oil phase is pure oil, and the maximum amplitude M(n) of its FID is collected 油 for calculating HI 油 。

[0037] In some specific embodiments of the present invention, in step (1), after the oil-water separation, a CPMG pulse sequence is continuously emitted to the obtained water phase, and the T2 spectrum is inversely obtained in real time. When the T2 spectrum shows only a single water peak, it indicates that the water phase is pure water, and the maximum amplitude M(n) of its FID is collected 水 for calculating HI 油 。

[0038] In the present invention, no chemical reagents are added during the whole process of magnetic resonance detection, and the probe does not contact the sample during the measurement process, so the sample will not be contaminated. After the test is completed, the sample can be directly reinjected into the fluid pipe.

[0039] In the present invention, the composition of the emulsified oil: The emulsified oil contains crude oil and water, and the water content is 0.5 - 100%, and any content from 0.5% to 100% of the water content can be measured.

[0040] The present invention will be described in detail below through examples.

[0041] In the following examples and comparative examples, those without specific conditions noted are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments without the manufacturer noted, they are all conventional products that can be obtained through commercial channels. The magnetic resonance equipment has the ability to measure the CPMG pulse sequence and FID (free induction decay signal), has the ability to automatically invert the T2 spectrum, and has the ability of layered scanning. Among them, the minimum echo interval ≤ 200 us, and the magnetic field inhomogeneity ≤ 100 ppm.

[0042] Example 1

[0043] Composition of emulsified oil: The emulsified oil contains crude oil and water.

[0044] (1) On-site calibration: The emulsified oil is allowed to stand to separate the oil and water. The CPMG pulse sequence is continuously emitted to the obtained oil phase, and the T2 spectrum is inversely obtained in real time. When the T2 spectrum shows only a single oil peak, it indicates that the oil phase is pure oil, and the maximum amplitude M(n) of its FID is collected 油 for calculating HI 油 , and at the same time, the CPMG pulse sequence is continuously emitted to the obtained water phase, and the T2 spectrum is inversely obtained in real time. When the T2 spectrum shows only a single water peak, it indicates that the water phase is pure water, and the maximum amplitude M(n) of its FID is collected 水 for calculating HI 油 , and the hydrogen index HI of the oil is calculated 油 = M(n) 油 / M(n) 水 ;

[0045] (2) Real-time measurement: The magnetic resonance equipment is installed at the wellhead to be measured, so that the emulsified oil fluid to be measured is scanned during the continuous flow through the magnetic resonance probe. In the direction perpendicular to the fluid flow direction, the fluid in the emulsified oil pipeline is spatially divided into 15 layers (as Figure 1 shown), and layered scanning is carried out using the magnetic resonance probe. The maximum amplitude M(n) of the FID is collected for each layer, and the water content η(n) of each layer is calculated according to M(n) = η(n) × M(n) 水 / n + [1 - η(n)] M(n) 水 × HI 油 / n;

[0046] (3) Calculate the dynamic water content according to η = η(1) × S(1) + η(2) × S(2) + … + η(15) × S(15).

[0047] Example 2

[0048] Measure the water content rate of the emulsified oil in Example 1:

[0049] (1) On-site calibration: Let the emulsified oil stand for treatment to separate the oil and water. Continuously emit a CPMG pulse sequence to the obtained oil phase, and inversely transform it in real time to obtain the T2 spectrum. When the T2 spectrum shows only a single oil peak, it indicates that the oil phase is pure oil, and collect the maximum amplitude M(n) of its FID 油 For calculating HI 油 , and at the same time, continuously emit a CPMG pulse sequence to the obtained water phase, and inversely transform it in real time to obtain the T2 spectrum. When the T2 spectrum shows only a single water peak, it indicates that the water phase is pure water, and collect the maximum amplitude M(n) of its FID 水 For calculating HI 油 , and calculate the hydrogen index HI of the oil 油 = M(n) 油 / M(n) 水 ;

[0050] (2) Real-time measurement: Install the magnetic resonance device at the wellhead to be measured, and let the emulsified oil fluid to be measured complete the scan during the process of continuously flowing through the magnetic resonance probe. In the direction perpendicular to the fluid flow direction, spatially divide the fluid in the emulsified oil pipeline into 13 layers (as Figure 1 shown), use the magnetic resonance probe to perform layer-by-layer scanning, collect the maximum amplitude M(n) of FID for each layer, and calculate the water content rate η(n) of each layer according to M(n)=η(n)×M(n) 水 / n + [1 - η(n)]M(n) 水 ×HI 油 / n;

[0051] (3) Calculate the dynamic water content rate according to η = η(1)×S(1)+η(2)×S(2)+…+η(13)×S(13).

[0052] Example 3

[0053] Measure the water content rate of the emulsified oil in Example 1:

[0054] (1) On-site calibration: Let the emulsified oil stand for treatment to separate the oil and water. Continuously emit a CPMG pulse sequence to the obtained oil phase, and inversely transform it in real time to obtain the T2 spectrum. When the T2 spectrum shows only a single oil peak, it indicates that the oil phase is pure oil, and collect the maximum amplitude M(n) of its FID 油 For calculating HI 油, while continuously emitting a CPMG pulse sequence to the obtained aqueous phase and inversely calculating the T2 spectrum in real time. When the T2 spectrum shows only a single water peak, it indicates that the aqueous phase is pure water, and the maximum amplitude M(n) of its FID is collected. 水 For calculating HI 油 , and calculating the hydrogen index HI of the oil. 油 = M(n) 油 / M(n) 水 ;

[0055] (2) Real-time measurement: Install the magnetic resonance device at the wellhead to be measured, and complete the scanning while the emulsified oil fluid to be measured continuously flows through the magnetic resonance probe. In the direction perpendicular to the fluid flow direction, the fluid in the emulsified oil pipeline is spatially divided into 10 layers (as Figure 1 shown), and use the magnetic resonance probe to perform layer-by-layer scanning. The maximum amplitude M(n) of the FID is collected for each layer, and according to M(n) = η(n) × M(n) 水 / n + [1 - η(n)]M(n) 水 ×HI 油 / n to calculate the water content η(n) of each layer;

[0056] (3) Calculate the dynamic water content according to η = η(1) × S(1) + η(2) × S(2) + … + η(10) × S(10).

[0057] Example 4

[0058] Measure the water content of the emulsified oil in Example 1:

[0059] (1) On-site calibration: Let the emulsified oil stand to separate the oil and water. Continuously emit a CPMG pulse sequence to the obtained oil phase and inversely calculate the T2 spectrum in real time. When the T2 spectrum shows only a single oil peak, it indicates that the oil phase is pure oil, and the maximum amplitude M(n) of its FID is collected. 油 For calculating HI 油 , while continuously emitting a CPMG pulse sequence to the obtained aqueous phase and inversely calculating the T2 spectrum in real time. When the T2 spectrum shows only a single water peak, it indicates that the aqueous phase is pure water, and the maximum amplitude M(n) of its FID is collected. 水 For calculating HI 油 , and calculating the hydrogen index HI of the oil. 油 = M(n) 油 / M(n) 水 ;

[0060] (2) Real-time measurement: Install the magnetic resonance device at the wellhead to be measured, and complete the scanning while the emulsified oil fluid to be measured continuously flows through the magnetic resonance probe. In the direction perpendicular to the fluid flow direction, the fluid in the emulsified oil pipeline is spatially divided into 5 layers (as Figure 1As shown in the figure, magnetic resonance probes are used for layer-by-layer scanning. For each layer, the maximum amplitude M(n) of the FID is collected, and the water content η(n) of each layer is calculated according to M(n) = η(n) × M(n) 水 / n + [1 - η(n)]M(n) 水 ×HI 油 / n;

[0061] (3) The dynamic water content is calculated according to η = η(1) × S(1) + η(2) × S(2) + … + η(5) × S(5).

[0062] Comparative Example 1

[0063] The water content of the emulsified oil in Example 1 was measured: An emulsified oil sample was collected at the wellhead using a sampling bucket and taken to the laboratory, and the water content of the fluid was obtained by means of electro-dehydration testing.

[0064] Evaluation method: Measure the comprehensive water content of the fluid flowing through the pipeline for 1 h: The flowmeter and the three-phase separator are connected in series. After the multiphase flow of the emulsified oil fluid is separated into single phases by the three-phase separator, a water flowmeter, an oil flowmeter, and a gas flowmeter are used to measure the comprehensive water content of the fluid (i.e., the actual water content); and it is compared with the average dynamic water content obtained in this Example 1 within 1 h (measured every 30 min). The average dynamic water content is the average value of the dynamic water content obtained within 1 h in this Example. The measurement result of Comparative Example 1 needs to be obtained after 24 h of sampling. The results are shown in Table 1. The closer the value of the average dynamic water content is to the comprehensive water content, the more accurate the measurement result is.

[0065] Table 1

[0066]

[0067] It can be seen from the results in Table 1 that the Examples of the present invention have higher detection accuracy, can perform dynamic measurement of the water content of emulsified oil by using low-field nuclear magnetic resonance technology, and realize rapid, green, non-invasive, and full-range testing of the water content of emulsified oil.

[0068] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for dynamically detecting the water content of emulsified oil, characterized in that, The steps include: (1) On-site calibration: Separate the emulsion oil into oil and water, and measure the maximum FID amplitudes of pure oil and pure water, namely M(n) 油 and M(n) 水 , and calculate the hydrogen index HI of the oil 油 = M(n) 油 / M(n) 水 ; (2) Real-time measurement: In the direction perpendicular to the fluid flow direction, the fluid in the emulsified oil pipeline is divided into n layers, and a magnetic resonance probe is used for layered scanning. The maximum amplitude M(n) of FID is collected for each layer, and the water content η(n) of each layer is calculated according to M(n) = η(n) × M(n) 水 / n + [1 - η(n)]M(n) 水 × HI 油 / n; (3) Calculate the dynamic moisture content according to η = η(1) × S(1) + η(2) × S(2) + ... + η(n) × S(n), where S(n) is the ratio of the volume of the nth layer to the total volume; Wherein, n is selected from an integer of 2-15.

2. The method according to claim 1, wherein, n is selected from an integer of 10-15.

3. The method according to claim 1 or 2, wherein, The method further comprises: before measuring, preheating the magnetic resonance probe to a temperature close to that of the emulsified oil fluid.

4. The method according to any one of claims 1 - 3, wherein, In step (1), before the emulsified oil is separated into oil and water, sampling is first performed and the sample is sampled into a sample tube. The sampling method is selected from normal pressure sampling or pressure-maintaining sampling.

5. The method according to any one of claims 1 - 4, wherein, In step (1), the oil-water separation method is static treatment, and the temperature of the static treatment is maintained within the range of ±5°C of the temperature when the emulsified oil is produced from the wellhead.

6. The method according to any one of claims 1 - 5, wherein, In step (1), the volumes of pure oil and pure water to be measured are the same.

7. The method according to any one of claims 1 - 6, wherein, The method further comprises: before performing the layered scanning in step (2), installing a magnetic resonance device to the pipe opening to be tested, so that the emulsified oil fluid to be tested completes the layered scanning in the process of continuously flowing through the magnetic resonance probe.

8. The method according to any one of claims 1 - 7, wherein, In step (2), the layered scanning method is static magnetic field gradient combined with antenna frequency modulation or gradient coil combined with antenna frequency modulation.

9. The method according to any one of claims 1 - 8, wherein, In step (1), after the oil-water separation, a CPMG pulse sequence is continuously emitted to the obtained oil phase, and the T2 spectrum is inversely calculated in real time. When the T2 spectrum shows only a single oil peak, it indicates that the oil phase is pure oil, and the maximum amplitude M(n) of its FID is collected. 油 For calculating HI 油 .

10. The method according to any one of claims 1 - 9, wherein, In step (1), after the oil-water separation, a CPMG pulse sequence is continuously emitted to the obtained aqueous phase, and the T2 spectrum is inversely obtained in real time. When the T2 spectrum shows only a single water peak, it indicates that the aqueous phase is pure water, and the maximum amplitude M(n) of its FID is collected. 水 For calculating HI 油 .

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