A method for predicting wax deposition amount in an oil-water mixed pipeline transportation process

Abstract

The present application relates to a kind of wax deposition amount prediction methods of oil-water mixed pipeline conveying process, it includes: measuring the soil temperature near buried oil-water mixed pipeline;In different operating conditions, the temperature of oil-water mixed pipeline oil-water mixture and the speed of oil-water mixed pipeline oil-water mixture in different operating conditions are measured;Oil-water mixture sample is obtained at the sampling point of field wellhead, and the water content of oil-water mixed pipeline conveying process oil-water mixture is calculated;Wax deposit is scraped from oil-water mixed pipeline, and the thickness of wax deposition is calculated;Wax deposition amount of oil-water mixed pipeline is influenced by the water content in oil-water mixed pipeline, inlet velocity, inlet temperature and soil temperature, multiple physical quantity operating parameters are combined, and multiple parameter combination form orthogonal table is formed;Multiple parameter combination mathematical model of oil-water mixed pipeline operation process is established, and wax deposition of oil-water mixed pipeline conveying process is predicted.The present application realizes accurate and convenient prediction of wax deposition amount of oil-water mixed pipeline conveying process.

Description

Technical fields:

[0001] This invention relates to the field of oil and gas storage and transportation technology, specifically a method for predicting wax deposition during oil-water mixed pipeline transportation. Background technology:

[0002] As most oilfields enter the mid-to-late stages of production, water content, input costs, and energy consumption continue to increase, placing higher demands on ambient temperature gathering and transportation. Influenced by factors such as transportation technology, topography, and oil properties, heating or heat tracing methods are often used during gathering and transportation, leading to a continuous increase in electricity and fuel oil consumption from the wellhead to the metering station, generally accounting for 30% to 40% of total energy consumption in crude oil production, resulting in increased carbon dioxide emissions. Simultaneously, wax deposition during transportation reduces the effective flow area of ​​pipelines, significantly increases energy loss, and in severe cases, can even cause pipeline or equipment blockages. Given the continuously rising water content and the increasingly severe challenges of energy conservation and consumption reduction, it is necessary to study the relationship between wax deposition in gathering and transportation pipelines for easily solidifying, high-viscosity crude oil and water content, as well as operating parameters of the oil-water mixture, with the goals of energy conservation, consumption reduction, and safe pipeline operation, to provide technical support for ambient temperature gathering and transportation production operations.

[0003] For oil-water mixed-phase pipeline transportation, loop-type experimental setups are typically used to study the wax deposition patterns in the oil-water two-phase system. However, the wax deposition during transportation is dynamically affected by actual operating conditions. Long-term pipeline operation leads to complex roughness variations due to internal corrosion. Furthermore, loop-type experimental setups are used for indoor pipelines and focus on only a portion of the horizontal pipeline, neglecting the combined effects of local bends, vertical pipes, and long-distance horizontal pipes from the wellhead to the metering station on crude oil flow and wax deposition. Therefore, using loop-type experimental setups to study the wax deposition patterns in the oil-water two-phase system introduces certain errors. Simultaneously, in actual production, water content is closely related to the wax deposition process. The presence of the water phase distorts and reduces the wax diffusion path. Higher water content results in a smaller internal temperature gradient, a lower wax molecule concentration gradient, and a decreased driving force for wax molecule diffusion. Therefore, a new method for predicting wax deposition during oil-water mixed-phase pipeline transportation needs to be established, considering the impact of water content changes on wax deposition thickness, to achieve accurate and convenient prediction of wax deposition during oil-water mixed-phase pipeline transportation.

[0004] In summary, current methods for predicting wax deposition in oil-water mixed pipelines all have certain limitations and cannot continuously, accurately, and conveniently calculate the amount of wax deposition during the transportation of oil and water in mixed pipelines. Summary of the Invention:

[0005] The purpose of this invention is to provide a method for predicting wax deposition during oil-water mixed transport pipelines. This method addresses the problem that current methods using loop experimental devices to study the wax deposition patterns in oil-water mixed transport pipelines cannot accurately reflect the actual fluid flow and heat transfer characteristics within the pipeline, leading to certain errors.

[0006] The technical solution adopted by this invention to solve its technical problem is as follows: This method for predicting wax deposition during oil-water mixed transportation pipeline processes includes the following steps:

[0007] Step 1: Place thermocouple thermometers in the soil near the burial depth of the oil-water mixed pipeline to measure the soil temperature near the buried pipeline; in the metering room, use thermocouple thermometers at the pipeline temperature measurement interface to measure the temperature of the oil-water mixture under different operating conditions; in the metering room, use a volumetric flow meter on the straight section of the pipeline to measure the velocity of the oil-water mixture under different operating conditions.

[0008] Step 2: Obtain oil-water mixture samples at the wellhead sampling point on site and calculate the water content of the oil-water mixture during the oil-water transport pipeline process;

[0009] Step 3: Scrape off the wax deposits from the pipe wall during the operation of the oil-water mixed transport pipeline, weigh the scraped wax deposits, and calculate the wax deposit thickness based on the size of the wax deposits and the pipe size;

[0010] Step 4: The amount of wax deposition in oil-water mixed transportation pipelines is affected by a combination of multiple physical parameters, including the water content, inlet velocity, inlet temperature, and soil temperature in the oil-water mixed transportation pipeline. These multiple physical parameters are combined to form an orthogonal array of multiple parameter combinations.

[0011] Step 5: Establish a multi-parameter combined mathematical model for the operation of oil-water mixed transport pipelines to predict wax deposition during the pipeline transportation process.

[0012]

[0013] Where: h s The calculated value for the wax deposition thickness is in mm. These represent the regression coefficients of the model; z1, z2, ... z w represents the power coefficients of the parameters in the regression model; d represents the degree of the polynomial.

[0014] Step two in the above scheme is as follows: control the water content of the oil-water mixture in the pipeline by changing the opening and closing size of the water mixing valve in the oil-water mixed transportation pipeline; prepare a clean, dry and well-sealed sampler, take a sample near the wellhead of the oil-water mixed transportation pipeline, slowly open the sampling valve on the pipeline during sampling, let the fluid flush the sampling port for a period of time to remove the impurities remaining at the sampling port, and then align the sampler with the sampling port to allow the oil-water mixture to flow into the container;

[0015] The obtained oil-water mixture was brought back to the laboratory, and the static separation method was used. The oil-water mixture was placed in a transparent graduated cylinder and allowed to stand for a period of time to allow the oil and water to completely separate into layers. The water content was calculated by measuring the volume of the oil layer and the water layer.

[0016] Step three of the above scheme is as follows: During the operation of the oil-water mixed transportation pipeline, the cleaning ball is placed inside the launching bucket at the wellhead. The pressure difference of the oil-water mixture before and after the cleaning ball is used to push the cleaning ball forward in the pipeline, scraping the wax deposit off the pipeline wall. After the cleaning ball enters the receiving bucket, the cleaning operation is completed. The scraped wax deposit is weighed using an electronic balance, and the wax deposit thickness is calculated based on the size of the wax deposit and the pipeline size.

[0017] Step three in the above plan is more specifically as follows:

[0018] Before starting the pigging operation, check the launching and receiving devices to ensure that the launching tank valves operate flexibly and are well sealed. Close the branch valves that are not related to the pigging operation to prevent the pig from accidentally entering the branch. Place the pig into the launching device at the wellhead and use the pressure difference before and after the oil-water mixture to push the pig forward in the oil-water mixed pipeline.

[0019] When the pig reaches the receiving bucket, close the valve connecting the receiving bucket to the oil-water mixed pipeline, and open the drain valve to discharge the wax deposits carried by the pig into the receiving bucket.

[0020] After the pipeline cleaning is completed, the wax deposit scraped off the oil-water mixed transport pipeline wall by the pipeline cleaning tool is weighed, and the average thickness of the wax deposit in the oil-water mixed transport pipeline is calculated.

[0021] Step four in the above scheme is specifically as follows:

[0022] First, the multi-physical quantity operating parameters include moisture content k1, inlet velocity k2, inlet temperature k3, and soil temperature k4, and each physical parameter has three possible values, where k1 has the following values: k 11 k 12 k 13 Values ​​of k2: k 21 k 22 k 23 Values ​​of k3: k 31 k 32 k33 k4 values: k 41 k 42 k 43 The water mixing rate is controlled by adjusting the size of the water mixing valve, and the soil temperature in different seasons is selected. At the same time, the inlet temperature and inlet velocity of the oil-water mixture are controlled by adjusting the size of the water mixing valve.

[0023] Secondly, select an appropriate orthogonal array S based on the number of parameters and the number of possible values. i (n t ), where S represents an orthogonal array, the subscript i represents the number of experiments, n represents the number of parameter values, and t represents the number of physical parameters arranged; for four physical quantity parameters, and each parameter has three values, S9(3) is selected. 4 Orthogonal array.

[0024] Beneficial effects:

[0025] This invention overcomes the limitations of traditional methods used in studying the wax deposition patterns in oil-water mixed-transport pipelines. These methods often rely on a loop-type experimental setup that focuses on a portion of the horizontal pipeline, neglecting the combined effects of local bends, vertical pipes, and long-distance horizontal pipes from the wellhead to the metering station on crude oil flow and wax deposition. This approach fails to accurately reflect the fluid flow and heat transfer characteristics within the actual mixed-transport pipeline, leading to errors. This new invention enables accurate and convenient prediction of wax deposition during oil-water mixed-transport pipeline operations, providing technical support for the ambient temperature gathering and transportation production of petroleum enterprises. Attached image description:

[0026] Figure 1 These are the measured and predicted values ​​of wax deposition thickness in oil-water mixed transportation pipelines under various operating conditions. Detailed implementation method:

[0027] This method for predicting wax deposition during oil-water mixed pipeline transportation includes the following:

[0028] Step 1: Taking the oil-water mixed transport pipeline as the research object, the soil temperature near the buried pipeline is measured on site using thermocouple thermometers placed near the pipeline burial depth. In the metering room, the temperature and velocity of the oil-water mixture under different operating conditions are measured using thermocouple thermometers at the pipeline temperature measurement interface and volumetric flow meters on the straight section of the pipeline.

[0029] Place the thermocouple thermometer probe in the soil around the oil-water mixed pipeline. The insertion position should be close to the pipeline but 0.2-0.3m away from it to avoid damaging the probe due to contact with the pipeline. Select thermocouple thermometer wires with certain moisture-proof and damage-proof properties. Read the temperature reading through the instrument connected on site and record it. When analyzing the data, consider the representativeness of the measurement position and take the average value of multiple measurements to reduce errors.

[0030] By observing the flow meters and thermometers in the metering room, the flow rate and temperature data of the oil-water mixture in the oil-water mixing pipeline are read and recorded. When reading the temperature, it should be taken when the thermometer reaches thermal equilibrium. Multiple measurements can be taken over a period of time, and the average value can be obtained. When reading the flow rate, the stability of the oil-water mixture flow rate should be observed. If abnormal fluctuations occur, check whether there is blockage, leakage, or flow meter malfunction in the pipeline.

[0031] Step 2: Obtain an oil-water mixture sample at the wellhead sampling point, separate the oil and water using the static separation method, and calculate the water content of the oil-water mixture inside the pipeline during transportation using a formula.

[0032] The water content of the oil-water mixture in the pipeline is controlled by adjusting the opening and closing of the water-injection valve. A clean, dry, and well-sealed sampler is prepared and sampled near the pipeline wellhead. During sampling, the sampling valve on the pipeline is slowly opened to allow fluid to flush the sampling port for a period of time, removing any impurities that may remain. Then, the sampling container is aligned with the sampling port, allowing the oil-water mixture to flow into the container.

[0033] The obtained samples were brought back to the laboratory, and the static separation method was used. The samples were placed in a transparent graduated cylinder and allowed to stand for a period of time to allow the oil and water to completely separate. The water content was calculated by measuring the volume of the oil layer and the water layer. The calculation formula is: water content = (water layer volume / (oil layer volume + water layer volume)) × 100%.

[0034] Step 3: During the operation of the oil-water mixed pipeline, the pigging ball is placed inside the launching bucket at the wellhead. The pressure difference of the oil-water mixture before and after the pigging ball propels the pigging ball forward in the pipeline, scraping the wax deposit off the pipe wall. After the pigging ball enters the receiving bucket, the pigging operation is completed. The scraped wax deposit is weighed using an electronic balance, and the wax deposit thickness is calculated based on the size of the wax deposit and the pipe size.

[0035] Before starting the pigging operation, inspect the launching and retrieving devices to ensure that the launching tank valves operate smoothly and are properly sealed. Close any branch valves unrelated to the pigging operation to prevent the pig from accidentally entering a branch. Place the pig into the launching device at the wellhead, and use the pressure difference between the oil and water mixture to propel the pig forward in the pipeline.

[0036] When the pig reaches the collection bucket, close the valve connecting the collection bucket to the pipeline and open the drain valve to discharge the wax deposits and other contaminants carried by the pig into the collection bucket.

[0037] After the pipeline cleaning is completed, the wax deposit scraped off the pipe wall by the pig is weighed. The formula for calculating the average thickness of the wax deposit in the oil-water mixed transport pipeline is as follows:

[0038]

[0039] Where h is the measured calculated value of the wax deposition thickness in the oil-water mixed transport pipeline, in mm; m is the mass of the wax deposition, in kg; r is the radius of the pipeline, in m; L is the length of the pipeline, in m; and ρ is the density of the wax deposition, in kg / m³. 3 .

[0040] Step 4: Since the amount of wax deposited in oil-water mixed transportation pipelines is mainly affected by the combined influence of water content, inlet velocity, inlet temperature and soil temperature, and considering the influence of the interaction between multiple physical parameters such as water content, inlet velocity, inlet temperature and soil temperature in oil-water mixed transportation pipelines, an orthogonal table is formed by scientifically and reasonably combining multiple physical parameters through orthogonal experiments.

[0041] Orthogonal experimental design combines physical parameters within different value ranges to evaluate the impact of each parameter on wax deposition under different value ranges, making the parameter combinations more scientific and reasonable. The specific steps are as follows:

[0042] First, based on the accumulated data from actual field operations, the physical parameters to be studied and the value range of each physical parameter are identified. In studying wax deposition during the transportation of oil-water mixtures in pipelines, the physical parameters include water content k1, inlet velocity k2, inlet temperature k3, and soil temperature k4, with each parameter having three possible values. Specifically, k1 has the following values: 11 k 12 k 13 Values ​​of k2: k 21 k 22 k 23 Values ​​of k3: k 31 k 32 k 33 k4 values: k 41 k 42 k 43 The water mixing rate was controlled by adjusting the size of the water mixing valve. Studies were conducted in different seasons to select different soil temperatures. At the same time, the inlet temperature and flow rate of the oil-water mixture were controlled by adjusting the size of the valve.

[0043] Secondly, select an appropriate orthogonal array S based on the number of parameters and the number of possible values. i (n t ), where S represents an orthogonal array, the subscript i represents the number of experiments, n represents the number of parameter values, and t represents the number of physical parameters arranged. For four physical parameters, each with three values, S9(3) can be selected. 4 An orthogonal array is shown below:

[0044]

[0045]

[0046] Step 5: Using a multivariate nonlinear regression mathematical method, a multi-parameter combined mathematical model of the oil-water mixed transport pipeline operation process is established to derive the functional relationships between water content, inlet velocity, inlet temperature, soil temperature, and wax deposition in the oil-water mixed transport pipeline. This is combined with the mean squared error (MSE) and goodness-of-fit (Mn) parameters. 2 Two metrics are used to comprehensively evaluate the model's performance.

[0047] Based on the orthogonal array of various physical quantity parameters, the wax deposition thickness was used as a predictive index for the wax deposition amount in oil-water mixed transportation pipelines. The field measurement data are shown below:

[0048]

[0049] Using the mathematical method of multiple linear regression, a multi-parameter combined model of the oil-water mixture transportation pipeline process was further established to obtain the functional relationship between parameters such as water content, inlet velocity, inlet temperature, soil temperature and wax deposition thickness.

[0050]

[0051] Where h is the measured value of the wax deposition thickness in the oil-water mixed transportation pipeline, in mm; These represent the regression coefficients of the model; z1, z2, ... z w represents the power coefficients of the parameters in the regression model; d represents the degree of the polynomial.

[0052] Given initial values ​​for the regression model, the corresponding regression coefficients are obtained through iterative solving. And the power coefficients of the parameters z1, z2, ... z w Based on this, the parameter values ​​are substituted into the multi-parameter combined model of the oil-water mixture transportation pipeline process to obtain the calculated value of wax deposition thickness, h. s .

[0053] Mean squared error (MSE) was used as the loss function to evaluate the difference between the calculated and experimental values ​​of wax deposition thickness. A mean squared error close to 0 indicates that the smaller the difference between the model's calculations and experimental values, the more accurate the model is. The mean squared error is defined as:

[0054]

[0055] Among them, h s The measured wax deposition thickness in the oil-water mixed transport pipeline of group s is in mm; h s It is the calculated value of the wax deposition thickness in the oil-water mixed transport pipeline of group s, in mm.

[0056] Meanwhile, by using the goodness-of-fit M 2 As a regression model's ability to explain the overall fluctuations in the data, M2 The closer the value is to 1, the better the model fits the data, meaning the higher the proportion of data fluctuations the model can explain. It can be used to represent the functional relationship between parameters such as water content, inlet velocity, inlet temperature, and soil temperature and the amount of wax deposition in oil-water mixed transport pipelines. M 2 The calculation is shown in the following formula:

[0057]

[0058] Among them, SS t Total error; SS r This is random error; The experimental average value of wax deposition thickness in oil-water mixed transport pipelines.

[0059]

[0060] Combining mean squared error (MSE) and goodness of fit (M) 2 The multi-parameter combined model of the oil-water mixed transport pipeline process, which has a small mean square error and a high goodness of fit obtained from the two indicators, is shown in the following equation:

[0061]

[0062] To make the above content of this invention more concise and understandable, the following section of an oil-water mixed transport pipeline in an oilfield is used as the research object to predict the wax deposition situation on the fifteenth day of its operation, and is described in detail below:

[0063] A section of an oil-water mixed-transport pipeline in an oilfield has a length of 500m and a diameter of φ89×5. The insulation layer is made of rigid polyurethane foam with a thickness of 30mm. This invention, based on orthogonal experiments and multivariate nonlinear regression, establishes a mathematical model for wax deposition changes during the oil-water mixed-transport pipeline process. It determines the functional relationship between wax deposition in the pipeline and the inlet velocity, inlet temperature, water content, and soil temperature of the oil-water two-phase mixture. Therefore, it enables the prediction of wax deposition during the oil-water mixed-transport pipeline process. The specific steps are as follows:

[0064] Step 1: Taking an oil-water mixed transport pipeline as the research object, the soil temperature near the buried pipeline was measured on-site using thermocouple thermometers placed near the pipeline's burial depth. In the metering room, the temperature and velocity of the oil-water mixture were measured under different operating conditions using thermocouple thermometers at the pipeline temperature measurement interface and volumetric flow meters on the straight section of the pipeline. The specific values ​​of the oil-water mixture temperature, flow rate, and surrounding soil temperature for each operating condition are shown in the table below:

[0065]

[0066] Step 2: Obtain an oil-water mixture sample at the wellhead sampling point, separate the oil and water using a static separation method, and calculate the water content of the oil-water mixture inside the pipeline during transportation using a formula. Specific values ​​are shown in the table below.

[0067]

[0068] Step 3: During the operation of the oil-water mixed-transport pipeline, a pigging ball is placed inside the launching bucket at the wellhead. The pressure difference between the oil and water mixture before and after the pigging ball propels it forward in the pipeline, scraping wax deposits off the pipe wall. After the pigging ball enters the receiving bucket, the pigging operation is complete. The scraped wax deposits are weighed using an electronic balance, and the wax deposition thickness is calculated based on the wax deposit size and pipeline dimensions. The wax deposition thickness after the fifteenth day of operation of the oil-water mixed-transport pipeline under different parameter combinations is shown in the table below.

[0069]

[0070] Step 4: Since the amount of wax deposited in oil-water mixed transportation pipelines is mainly affected by the combined influence of water content, inlet velocity, inlet temperature and soil temperature, and considering the influence of the interaction between multiple physical parameters such as water content, inlet velocity, inlet temperature and soil temperature in oil-water mixed transportation pipelines, an orthogonal table is formed by scientifically and reasonably combining multiple physical parameters through orthogonal experiments.

[0071] In the study of wax deposition prediction in oil-water mixed transport pipelines, physical parameters included water content k1, inlet velocity k2, inlet temperature k3, and soil temperature k4. Specifically, k1 values ​​were 70%, 40%, and 10%; k2 values ​​were 1.5, 1.2, and 1.0; k3 values ​​were 317K, 316K, and 315K; and k4 values ​​were 293K, 283K, and 273K. The resulting S9(3)... 4 An orthogonal array is shown below:

[0072]

[0073] Step 5: Using a multivariate nonlinear regression mathematical method, a multi-parameter combined mathematical model of the oil-water mixed transport pipeline operation process is established to derive the functional relationships between water content, inlet velocity, inlet temperature, soil temperature, and wax deposition in the oil-water mixed transport pipeline. This is combined with the mean squared error (MSE) and goodness-of-fit (Mn) parameters. 2 Two metrics are used to comprehensively evaluate the model's performance.

[0074] Based on the orthogonal array of various physical parameter combinations, the wax deposition thickness is used as a predictive index for the wax deposition amount in oil-water mixed transportation pipelines. The actual measured wax deposition thickness of oil-water mixed transportation pipelines under various parameter combinations is shown in the table below:

[0075]

[0076] Mathematical model of multiple physical quantities in oil-water mixed pipeline transportation process:

[0077]

[0078] After multivariate nonlinear regression, the polynomial form is obtained as follows:

[0079] y = a 0000 +a 1100 y1y2+a 1010 y1y3+a 1001 y1y4+a 0110 y2y3+a 0101 y2y4+a 0011 y3y4+a 1000 y1+a 0100 y2+a 0010 y3

[0080] Among them, the coefficients and power coefficients are as follows:

[0081] a 0000 =-0.30787, a 1100 =0.08916, a 1010 =-0.03466, a 1001 =-0.00567, a 0110 =1.80757, a 0101 =-0.07747, a 0011 =0.00096, a 1000 =12.46239, a 0100 =-549.64428、a 0010 = -0.26836

[0082] By reverting the multi-parameter numerical values ​​back to the established mathematical regression model combining multiple physical quantities of the oil-water mixed transport pipeline process, the calculated value h of the wax deposition thickness was obtained. The result is shown in the table below:

[0083]

[0084] Mean squared error (MSE) is used as the loss function to evaluate the difference between the calculated and measured values ​​of wax deposition thickness. A mean squared error close to 0 indicates that the smaller the difference between the model's calculations and the measured values, the more accurate the model is. The mean squared error is defined as:

[0085]

[0086] The mean square error (MSE) value is close to 0, indicating that the difference between the predicted value of wax deposition in the oil-water mixed transportation pipeline and the field measured data is small.

[0087] By goodness of fit M 2 As a regression model's ability to explain the overall fluctuations in the data, M 2 The closer a value is to 1, the better the model fits the data; that is, the higher the proportion of data fluctuations that the model can explain relative to the total fluctuations.

[0088] Random Error SS r calculate:

[0089]

[0090] SS r =(0.83-0.82) 2 +(1.17-1.13) 2 +(1.39-1.42) 2 +(0.50-0.52) 2 +(0.21-0.29) 2 +(0.30-0.25) 2 +(0.25-0.22) 2 +(0.34-0.36) 2 +(0.18-0.17) 2 =0.0133

[0091] Calculation of average wax deposition thickness in oil-water mixed transport pipelines:

[0092]

[0093] Total error calculation:

[0094]

[0095] SS t =(0.83-0.574444) 2 +(1.17-0.574444) 2 +(1.397-0.574444) 2 +(0.50-0.574444) 2 +(0.21-0.574444) 2 +(0.30-0.574444) 2 +(0.25-0.574444) 2 +(0.34-0.574444) 2 +(0.18-0.574444) 2 =3.960909

[0096] Therefore, the goodness of fit M 2 for:

[0097]

[0098] The goodness of fit M was calculated. 2 A value close to 1 indicates that the model fits the data well, meaning that the model can explain a high proportion of the total data fluctuations.

[0099] By combining mean squared error (MSE) and goodness of fit (M) 2 Two indicators were used to comprehensively evaluate the performance of the established model, and a multi-parameter combined regression mathematical model of the oil-water mixed transportation pipeline process with a mean square error of 0.001478 and a goodness of fit of 0.99 was obtained, which showed good fitting performance.

[0100] The multi-physical quantity combined regression mathematical model for the oil-water mixed transportation pipeline process is as follows:

[0101] h=-0.30787+0.08916y1y2-0.03466y1y3-0.00567y1y4+1.80757y2y3-0.07747y2y4+0.00096y3y4+12.46239y1-549.64428y2-0.26836y3

[0102] Based on the multi-physical quantity combination regression mathematical model of the oil-water mixed transportation pipeline process, the water content of the oil-water mixture on site was controlled to 60% by changing the size of the water mixing valve. The temperature and velocity of the oil-water mixture were adjusted to 316K and 1.2m / s, respectively. During spring operation, the soil temperature near the oil-water mixed transportation pipeline was 283K. The wax content was measured after running under this combination for fifteen days.

[0103] The actual measured thickness of the wax deposition was h = 1.03 mm.

[0104] Calculations show that when the combined physical parameters of the oil-water mixed transport pipeline are k1 = 60, k2 = 1.2, k3 = 316, and k4 = 283, the wax deposition thickness is:

[0105] h=-0.30787+0.08916×60×1.2-0.03466×60×316-0.00567×60×283+1.80757×1.2×316-0 .07747×1.2×283+0.00096×316×283+12.46239×60-549.64428×1.2-0.26836×316=1.02

[0106] The relative error ε between the measured data h and the calculated data h is:

[0107]

[0108] The reliability of the model was verified.

[0109] In summary, this method for predicting wax deposition during the operation of oil-water mixed-transport pipelines breaks through the limitations of conventional methods that use loop-type experimental devices to study the wax deposition patterns in oil-water two-phase systems. These methods neglect the influence of local bends, vertical pipes, and long-distance horizontal pipes from the wellhead to the metering station on crude oil flow and wax deposition, failing to accurately reflect the fluid flow and heat transfer characteristics within the actual mixed-transport pipeline and causing certain errors. This method fully considers the influence of multiple physical parameters such as water content, inlet temperature, inlet velocity, and soil temperature on wax deposition, achieving accurate and convenient prediction and calculation of wax deposition during the transportation of oil-water mixed-transport pipelines.

Claims

1. A method for predicting wax deposition during oil-water mixed transport pipeline processes, characterized in that... Includes the following steps: Step 1: Place thermocouple thermometers in the soil near the burial depth of the oil-water mixed pipeline to measure the soil temperature near the buried pipeline; in the metering room, use thermocouple thermometers at the pipeline temperature measurement interface to measure the temperature of the oil-water mixture under different operating conditions; in the metering room, use a volumetric flow meter on the straight section of the pipeline to measure the velocity of the oil-water mixture under different operating conditions. Step 2: Obtain oil-water mixture samples at the wellhead sampling point on site and calculate the water content of the oil-water mixture during the oil-water transport pipeline process; Step 3: Scrape off the wax deposits from the pipe wall during the operation of the oil-water mixed transport pipeline, weigh the scraped wax deposits, and calculate the wax deposit thickness based on the size of the wax deposits and the pipe size; Step 4: The amount of wax deposition in oil-water mixed transportation pipelines is affected by a combination of multiple physical parameters, including the water content, inlet velocity, inlet temperature, and soil temperature in the oil-water mixed transportation pipeline. These multiple physical parameters are combined to form an orthogonal array of multiple parameter combinations. Step 5: Establish a multi-parameter combined mathematical model for the operation of oil-water mixed transport pipelines to predict wax deposition during the pipeline transportation process. In the formula: h is the calculated value of the wax deposition thickness; These represent the regression coefficients of the model; z1, z2, ... z w represents the power coefficients of the parameters in the regression model; d represents the degree of the polynomial.

2. The method for predicting wax deposition during oil-water mixed-transport pipeline transportation according to claim 1, characterized in that: Step two specifically involves: controlling the water content of the oil-water mixture in the pipeline by changing the opening and closing size of the water mixing valve in the oil-water mixed pipeline; preparing a clean, dry, and well-sealed sampler; taking a sample near the wellhead of the oil-water mixed pipeline; slowly opening the sampling valve on the pipeline during sampling to allow the fluid to flush the sampling port for a period of time to remove any remaining impurities; and then aligning the sampler with the sampling port to allow the oil-water mixture to flow into the container. The obtained oil-water mixture was brought back to the laboratory, and the static separation method was used. The oil-water mixture was placed in a transparent graduated cylinder and allowed to stand for a period of time to allow the oil and water to completely separate into layers. The water content was calculated by measuring the volume of the oil layer and the water layer.

3. The method for predicting wax deposition during oil-water mixed transport pipeline transportation according to claim 2, characterized in that: Step three specifically involves: during the operation of the oil-water mixed transport pipeline, placing the pigging ball inside the launching bucket at the wellhead position, using the pressure difference of the oil-water mixture before and after the pigging ball to propel the pigging ball forward in the pipeline, scraping the wax deposits off the pipeline wall, and completing the pigging operation after the pigging ball enters the receiving bucket. The scraped wax deposits are weighed using an electronic balance, and the wax deposit thickness is calculated based on the size of the wax deposits and the pipeline size.

4. The method for predicting wax deposition during oil-water mixed transport pipeline transportation according to claim 3, characterized in that: Step three is more specifically as follows: Before starting the pigging operation, check the launching and receiving devices to ensure that the launching tank valves operate flexibly and are well sealed. Close the branch valves that are not related to the pigging operation to prevent the pig from accidentally entering the branch. Place the pig into the launching device at the wellhead and use the pressure difference before and after the oil-water mixture to push the pig forward in the oil-water mixed pipeline. When the pig reaches the receiving bucket, close the valve connecting the receiving bucket to the oil-water mixed pipeline, and open the drain valve to discharge the wax deposits carried by the pig into the receiving bucket. After the pipeline cleaning is completed, the wax deposit scraped off the oil-water mixed transport pipeline wall by the pipeline cleaning tool is weighed, and the average thickness of the wax deposit in the oil-water mixed transport pipeline is calculated.

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