Determination method for wall-adhering and oil-condensing scouring flow velocity of extra-high-water-content crude oil

Abstract

The invention relates to a method for determining the scouring flow velocity of wall-adhered condensed oil of extra-high-water-content crude oil in the crude oil pipeline transportation technology, which specifically comprises the following steps: preparing wall-adhered condensed oil through a simulated stirring tank, respectively fixing different masses of condensed oil blocks on different test pipe sections, and then sequentially testing the different masses of condensed oil blocks to obtain the scouring flow velocity of the wall-adhered condensed oil of the extra-high-water-content crude oil. The corresponding scouring flow velocity is tested through the loop scouring experiment at different temperatures, a prediction model of the scouring flow velocity of the ultra-high-water-content crude oil adhering to the wall and condensing oil is further established, and on-site gathering and transportation parameters are determined according to the established prediction model. According to the method, the formation of pipeline wall-adhered condensed oil in the cooling and conveying process of the extra-high water content crude oil and the scouring flow velocity at different temperatures are simulated, a reference basis is provided for determining the temperature, the flow velocity and the flow rate of low-temperature conveying of the crude oil, and the method can be used for guiding and determining conveying parameters of the extra-high water content crude oil with different properties.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of crude oil pipeline transportation, in particular to a method for determining the flushing flow rate of wall-sticking and coagulated oil of extra-high water-cut crude oil. BACKGROUND

[0002] Most of the domestic oilfield developments have entered the later stage. The related process technology of non-heating gathering and transportation has been experimented and applied in a large number of oilfield blocks. It has been widely recognized that the wall-sticking temperature is the gathering and transportation temperature limit of low-temperature gathering and transportation of high water-cut crude oil, and it has entered the promotion stage. However, when the non-heating gathering and transportation experiment is carried out on the extra-high water-cut crude oil pipeline with a comprehensive water cut of more than 90%, it is found that the extra-high water-cut pipeline is relatively stable and safe at the wall-sticking temperature, and there is still a certain temperature reduction space to save the energy consumption of crude oil pipeline transportation. Therefore, it is urgent to improve the production efficiency of the extra-high water-cut crude oil pipeline and reduce the gathering energy consumption. Therefore, it is of great significance to carry out the research on the flushing rule of the coagulated oil block of the extra-high water-cut crude oil below the wall-sticking temperature, so as to perfect the related technology of non-heating gathering and transportation of oilfields and expand the application range of non-heating gathering and transportation in actual production. SUMMARY

[0003] The present application provides a method for determining the flushing flow rate of wall-sticking and coagulated oil of extra-high water-cut crude oil, which is easy to form wall-sticking and coagulated oil in the low-temperature transportation of the pipeline. Through the research on the flushing flow rate of wall-sticking and coagulated oil, the minimum flow required for safe transportation of the wall-sticking and coagulated oil in the temperature reduction gathering and transportation of the high water-cut pipeline or the lowest temperature at which the wall-sticking and coagulated oil can be flushed away under the given flow is explored.

[0004] The purpose of the present application is achieved by a method for determining the flushing flow rate of wall-sticking and coagulated oil of extra-high water-cut crude oil, which comprises the following steps: Step 1: Prepare the crude oil water sample for flushing experiment. Part of the crude oil is cooled to the coagulated oil temperature through simulated stirring tank, and the wall-sticking and coagulated oil block is prepared; Step 2: Prepare coagulated oil blocks with different masses and fix them on different test pipe sections. Different masses of wall-sticking and coagulated oil blocks in step 1 are fixed on the walls of different test pipe sections, the temperature is controlled to the coagulated oil temperature in step 1, and it is static for more than 30 minutes, so that the wall-sticking and coagulated oil block has the same wall-sticking performance as that in step 1; Step 3: Adjust the flushing ring device. The storage tank and the flushing ring of the flushing ring device are filled with the crude oil water sample prepared in step 1. The flushing ring is connected with a circulating pump and a detachable test pipe section. The inner diameters of the flushing ring and the test pipe section are the same. The flushing ring and the storage tank are respectively provided with a temperature control water bath. Step 4, starting from the test pipe section with the smallest oil block, connect the test pipe section with the oil block in step 2 to the scouring loop, start the circulating pump, circulate the crude oil water sample in the scouring loop and the test pipe section, start from the initial flow rate and the initial temperature, scour the test pipe section, after each circulating flow rate scouring for 30 minutes, if the oil block is not scoured, increase the flow rate and continue to scour until the oil block in the test pipe section is scoured, record the corresponding oil block mass, scouring flow rate and scouring temperature; Step 5, replace the test pipe section with the same mass of oil block, reduce the loop temperature, start from the scouring flow rate recorded in the last time, gradually increase the scouring flow rate, continue to scour the oil block, and record the corresponding scouring flow rate; repeat the temperature reduction scouring process of the step, until the circulating pump reaches the maximum flow rate, and the scouring experiment of the wall-adhesion oil block at the corresponding flow rate is completed; Step 6, repeat the scouring test of step 4 and step 5, respectively, to carry out the scouring test at different temperatures for oil blocks of different masses, and record the mass of the oil block, the scouring flow rate and the scouring temperature; Step 7, according to the scouring data of the oil block, input the scouring temperature, the mass of the oil block and the scouring flow rate data of the scoured oil block into the origin software, respectively, compare the scouring flow rate and the applicability of different models under the influence factors, establish a high water cut crude oil wall-adhesion oil block scouring flow rate prediction model to determine the scouring flow rate u of the oil block of different masses at different temperatures; Step 8, according to the monitoring data of the construction site and the scouring flow rate u of the oil block of different masses at different temperatures calculated by the prediction model in step 7, according to the formula u=4Q / πd 2 ; in the formula, Q is the flow rate, d is the pipe diameter, The scouring flow rate is calculated for determining the minimum conveying flow rate and the scouring flow rate of the corresponding oil block mass on the construction site.

[0005] The above method of the application simulates the formation of the pipeline wall-adhesion oil block in the high water cut crude oil temperature reduction conveying process, and obtains the scouring flow rate at different temperatures, which provides a reference basis for determining the temperature, flow rate and flow of the crude oil low temperature conveying, and can be used to guide the determination of the conveying parameters of different crude oils.

[0006] Further, in order to facilitate the preparation of the prepared oil block, in the first step, when preparing the oil water sample for the flushing experiment, the oil sample taken from the oil pipeline on site is used to prepare the oil water sample with a water content similar to that of the produced liquid; when preparing the oil block, the oil water sample is stirred in the simulated stirring tank, the temperature is raised to 50°C while stirring, then the oil water sample in the simulated stirring tank is cooled at a rate of 0.5°C / min while stirring, until it reaches 3-5°C below the oil freezing point, and then it is stirred at a constant temperature for 10-20 min until sufficient oil block is collected at the bottom of the simulated stirring tank, then the drain valve at the bottom of the tank is opened to release the oil water mixture, and the oil block adhering to the inner wall of the tank is sampled for use in the flushing experiment.

[0007] In order to facilitate the fixation of the oil block on the inner wall of the test pipe section for the flushing experiment, in the second step, different masses of oil blocks are taken and placed in different test pipe sections, the test pipe sections are cooled to the oil freezing temperature of the first step, and then left to stand for 30 min to allow the oil block to adhere to the inner wall of the test pipe section, then the adhesion performance of the oil block in the test pipe section is tested by the following pre-flushing experiment: the test pipe section is connected to the flushing loop, and the flushing loop is filled with the same oil water mixture as in the first step with a water content of 50% and a temperature of the oil freezing temperature, and pre-flushing is carried out for 20-30 min, and the oil block still adheres firmly to the wall; otherwise, the same mass of oil block is placed again and left to stand for 30 min, and the pre-flushing experiment is carried out again until the oil block adheres firmly to the wall.

[0008] Further, in order to verify the adhesion performance of the oil block in the test pipe section, in the second step, the pre-flushing flow rate is the same as the shear rate corresponding to the oil stirring in the simulated stirring tank in the first step, which is calculated and determined according to the following formula:

[0009] In the formula: is the average shear rate of the flushing loop, is the average shear rate of the simulated stirring tank, V is the flushing flow rate, D is the inner diameter of the flushing loop, is the viscosity of the oil water emulsion in the simulated stirring tank, is the rotational speed of the simulated stirring tank; after the rotational speed of the simulated stirring tank and the viscosity of the oil water emulsion in the tank are determined, the average shear rate of the simulated tank can be calculated , and then according to , the inner diameter of the pipe D is substituted into the above formula to convert the flushing flow rate of the loop corresponding to the average shear rate in the simulated stirring tank V .

[0010] Further, in the third, fourth, fifth and sixth steps, the oil water sample used in the flushing experiment is the same as the oil water sample used in the first step to prepare the oil block.

[0011] Further, in the fourth step, the initial flow rate of the flushing is the same as the pre-flushing flow rate in the second step, and the initial temperature is the pour point of the crude oil; the value of the flow rate of the flushing is increased by 0.012 m / s each time.

[0012] Further, in the fifth step, the temperature is decreased by 2℃ each time.

[0013] In order to accurately predict the flow rate of the flushing of the wall-adhered and solidified oil, in the seventh step, the model for predicting the flow rate of the flushing of the wall-adhered and solidified oil is u = a * exp(-b) * m -c , wherein a, b and c are constants obtained by software calculation and are different for different oil-water mixtures, u is the flow rate of the flushing, m is the mass of the solidified oil, and T is the temperature of the flushing experiment.

[0014] Further, in the second step, the test pipe section is flushed and wetted by using the oil-water sample for flushing before the wall-adhered and solidified oil block is fixed. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is a schematic diagram of the indoor stirring simulation tank in the first step.

[0016] Figure 2 It is a schematic diagram of the flushing loop device in the third step.

[0017] Figure 3 It is a comparison and selection of the model of the flow rate of the flushing and the mass of the solidified oil.

[0018] Figure 4 It is a comparison and selection of the model of the flow rate of the flushing and the temperature of the experiment.

[0019] In the figure, 1 is a stirring simulation tank; 2 is a water bath pot; 3 is an inlet and outlet valve; 4 is a liquid storage tank; 5 is a temperature control water bath device; 6 is a measurement pipe section; 7 is a flushing loop; 8 is a circulating pump; 9 is a thermometer; 10 is a pressure gauge; and 11 is a flow meter. DETAILED DESCRIPTION

[0020] The implementation process of the method for determining the flow rate of the flushing of the wall-adhered and solidified oil of the extra-high water-cut crude oil will be described in detail below with reference to the accompanying drawings.

[0021] All the implementation tools include Figure 1 the indoor stirring simulation tank shown in the figure and Figure 2 the flushing loop device and the test pipe section shown in the figure need to be cleaned and pretreated before use, and are wetted by using the oil-water sample for flushing. The monitoring instruments need to be calibrated and qualified before use. The indoor simulation stirring tank in the embodiment is as shown in Figure 1As shown, this is mainly used to simulate the low-temperature shearing motion of crude oil flotation oil within a certain shear rate range to prepare solidified oil blocks for simulating scouring experiments. It includes a simulated stirring tank 1, with inlet and outlet valves at the bottom of the tank. The tank body is equipped with electrically driven stirring blades, and the outer wall of the tank body is equipped with a heat exchange jacket that is circulated and connected to a water bath for controlling the temperature inside the tank. To facilitate sample collection, the simulated stirring tank used in the example experiment has an easily accessible sampling port on its side wall for sampling solidified oil blocks.

[0022] like Figure 2 As shown, the flushing ring device of this embodiment includes a liquid storage tank 4, a flushing ring 7 connected to the liquid storage tank 4, a detachable test pipe section 6 of the same diameter connected to the flushing ring 7, and a circulation pump 8 on the flushing ring 7. To facilitate the overall temperature control of the flushing ring 7 and the liquid storage tank 4, heat exchange structures for temperature control are provided on the outer periphery of both the flushing ring 7 and the liquid storage tank 4. Specifically, heat exchange tubes are spirally wound on the outer periphery of the flushing ring 7, and the heat exchange tubes are connected to one of the temperature-controlled water bath devices. The outer wall of the liquid storage tank 4 is also provided with a heat exchange jacket for controlling the temperature of the liquid inside the tank. The heat exchange jacket is connected to another temperature-controlled water bath device 5. To facilitate data monitoring, a thermometer 9, a pressure gauge 10, and a flow meter 11 are provided on the flushing ring. Before each pre-flushing and flushing experiment, the flushing loop 7 was wetted with experimental crude oil water sample for 10 minutes. Before the experiment, the monitoring device also needed to be debugged and calibrated to ensure that the pointer or reading was normal, so as to ensure the accuracy of the monitoring data.

[0023] The method for determining the scouring velocity of ultra-high water-cut crude oil adhering to the wall in this embodiment includes the following steps: Step 1: First, prepare the crude oil water sample for the flushing experiment. Oil samples taken from the field pipeline of the studied crude oil block are used to prepare a crude oil emulsion with a water content similar to the produced fluid. This emulsion is used for the subsequent preparation of solidified oil blocks and flushing experiments. The following method is employed... Figure 1 The simulated stirred tank shown is used to prepare oil clumps adhering to the walls. A crude oil-water sample is placed in simulated stirred tank 1 and mixed. While stirring, the temperature is raised to 50°C. Then, while stirring, the oil-water mixture in simulated stirred tank 1 is cooled at a rate of 0.5°C / min until it reaches 3-5°C below the crude oil's pour point. In this embodiment, the crude oil's pour point is 29°C, and the final cooling temperature is 25°C. The mixture is then stirred at 25°C for 20 minutes until sufficient oil clumps are produced. The inlet / outlet valve 3 at the bottom of the simulated stirred tank is then opened to release the oil-water mixture. The oil clumps adhering to the walls are removed from the sampling port for use in preparation for the flushing experiment. The stirring speed of the simulated stirred tank in this step is set according to the shear rate of the fluid inside the pipeline during crude oil transportation. Set, according to formula The simulated stirring tank rotation speed N is calculated, wherein μ is the viscosity of the crude oil water sample, the shear rate is taken in the range of the shear rate in the oil pipeline, and the simulated stirring tank rotation speed N is obtained after conversion. In this embodiment, the lower stirring paddle rotation speed 200 r / min is taken in the range of the shear rate in the oil pipeline to facilitate the rapid coagulation of oil.

[0024] In step 2, different masses of coagulated oil blocks are prepared and fixed on different test pipe sections 6. Before use, the test pipe sections 6 are pretreated. The wall-adhesive coagulated oil blocks of different masses in step 1 are taken and fixed on the walls of different test pipe sections 6, respectively. The temperature is controlled to the coagulated oil temperature 25℃ in step 1, and is static for more than 30 minutes, so that the wall-adhesive performance of the coagulated oil blocks is the same as that in step 1. In this step, coagulated oil blocks with masses of 1.0 g, 1.5 g and 2.0 g are taken, respectively. Several coagulated oil blocks with each mass are taken, and the coagulated oil blocks with different masses are placed in different test pipe sections 6 and are labeled with the masses on the walls. After the two ends of each test pipe section are closed with rubber plugs, the test pipe sections are placed in a temperature control box, the temperature is lowered to the coagulated oil temperature 25℃ in step 1, and is static for 30 minutes, so that the coagulated oil blocks are wall-adhesive in the inner walls of the test pipe sections 6. Then, the fastness of the wall-adhesive coagulated oil blocks in the test pipe sections 6 is detected through the following pre-flushing experiment. After the flushing loop is wetted by the crude oil water sample, the test pipe sections of each mass are connected to the flushing loop as shown in the figure, and the flushing loop is filled with the same crude oil water sample as in the simulated stirring tank in step 1. After pre-flushing for 30 minutes, if the coagulated oil blocks are still wall-adhesive, otherwise, the coagulated oil blocks with the same mass are placed again, the static time at the coagulation point is extended to 30 minutes, and the pre-flushing experiment is performed again until the coagulated oil blocks are wall-adhesive. Figure 2

[0025] In the above pre-flushing experiment, the pre-flushing flow rate is the same as the shear rate corresponding to the flow rate in the simulated stirring tank in step 1. The pre-flushing flow rate is calculated and determined according to the following formula:

[0026] In the formula, γ is the average shear rate of the flushing loop, γ is the average shear rate of the simulated stirring tank, V is the flushing flow rate, V D is the inner diameter of the flushing loop, D μ is the viscosity of the oil-water emulsion in the simulated stirring tank, N is the rotation speed of the simulated stirring tank. After the rotation speed N of the simulated stirring tank, the viscosity μ of the oil-water emulsion in the simulated stirring tank and the average shear rate γ of the simulated stirring tank are determined according to the above two formulas, the average shear rate γ of the simulated stirring tank can be calculated. According to the formula, , the inner diameter D of the pipeline is substituted into the above formula, and the flushing flow rate V corresponding to the average shear rate of the simulated stirring tank is converted. V

[0027] ​​​In this step, to ensure the consistency of the performance of the wall-adhering solidified oil in test section 6 with that in the simulated mixing tank in step 1, the yield stress evaluation verification of the solidified oil was carried out as follows. The yield stress of the wall-adhering solidified oil can reflect the strength of the adhered oil layer, and can also be regarded as a quantitative indicator of the "cohesive strength" or "structural integrity" of the oil layer before shear peeling. It is the main influencing factor that hinders its scouring and peeling in the pipeline. During the yield stress evaluation verification experiment, the yield stress of the solidified oil block prepared in simulated mixing tank 1 and the solidified oil block in test section 6 after cooling were tested with a rheometer. According to the data in Table 1, the yield stress of the two is almost the same, so the degree of adhesion of the solidified oil block is consistent.

[0028] The test results of the yield stress of the solidified oil adhering to the wall in the simulated mixing tank and test pipe section under different test temperatures are shown in Table 1 below. The yield stress of the two solidified oil blocks is basically the same at the same temperature.

[0029] Table 1. Yield stress of oil adhering to the wall at different test temperatures

[0030] Step 3, Debugging Figure 2 After the flushing ring device and monitoring device are installed, the storage tank 4 and flushing ring 7 of the ring device are filled with crude oil water sample of the same composition as in step 1, and then the circulation pump 8 is started to wet the flushing ring.

[0031] Step 4: Starting with the test section containing the smallest solidified oil block, connect the test section with the solidified oil block from Step 2 to the flushing loop 7. Start the circulation pump 8, and circulate the crude oil water sample in the flushing loop and test section from an initial flow rate of 0.2 m / s and an initial temperature of 29°C (the pour point of crude oil). Flushing the test section with the crude oil water sample at each flow rate for 30 minutes, if the solidified oil block is not flushed away after each flow rate, increase the flow rate by 0.012 m and continue flushing until the solidified oil block in the test section is flushed away. Record the corresponding solidified oil block mass, flushing flow rate, and flushing temperature. The recorded data are shown in columns 1-3 of the table.

[0032] Step 5: Replace the fixed test pipe section with the same mass of solidified oil block from Step 2. Reduce the ring temperature in increments of 2°C each time. Gradually increase the flushing flow rate starting from the previously recorded flushing flow rate. Continue to flush the solidified oil block and record the corresponding flushing flow rate. Repeat the cooling and flushing process in this step until the circulating pump reaches its maximum flow rate. The recorded data is shown in columns 1-3 of Table 2.

[0033] Step 6: Repeat steps 4 and 5 for the scouring test. Perform scouring tests at different temperatures on other solidified oil blocks of different qualities prepared in step 2 and record the solidified oil block quality, scouring flow rate and scouring temperature. The recorded data are shown in columns 1-3 of Table 2.

[0034] Step 7, according to the scouring data of the oil block, by origin software, input the scouring temperature, the mass of the oil block and the scouring flow rate data of the oil block, respectively compare and select the scouring flow rate and the different model applicability of each influencing factor, establish the wall sticking oil scouring flow rate prediction model of the extra high water cut crude oil, to determine the scouring flow rate u of the oil block of different mass at different temperature. For example Figure 3 The left and right two graphs are the model comparison curves of the scouring flow rate and the oil mass at different temperatures, Figure 4 The left and right two graphs are the model comparison curves of the scouring flow rate and the experimental temperature of different oil block mass. After comparison, when the oil block mass adopts the power law model and the experimental temperature adopts the exponential model, the accuracy is higher, the origin software establishes the model according to the temperature, the mass of the oil block and the corresponding scouring flow rate data recorded in the experiment, the model is as follows:

[0035] Step 8, according to the monitoring data of the construction site and the scouring flow rate u of the oil block of different mass at different temperature calculated by the prediction model in step 7, according to the formula u = 4Q / πd 2 ; In the formula, Q is the flow rate, and d is the pipe diameter; The scouring flow rate is calculated for the construction site to determine the minimum conveying flow rate and the scouring flow rate of the corresponding oil block mass, and the calculation results are shown in the fourth column data of table 2. Table 2 comparison data of the measured value and the predicted value of the scouring flow rate of the oil block of different mass

[0036] The above implementation process of the embodiment simulates the formation of the wall sticking oil of the pipeline in the cooling and conveying process of the extra high water cut crude oil and the scouring flow rate at different temperatures, provides a reference basis for determining the temperature, flow rate and flow rate of the crude oil in the low temperature conveying, and can be used to guide the determination of the conveying parameters of different crude oils.

[0037] When the actual field pipeline is applied, first select the pipe section where the oil block is accumulated more seriously through pressure drop monitoring, rely on the online analysis equipment of the pipeline oil sample water cut to monitor the real-time water cut of the pipeline, then determine the mass of the oil block in the selected pipe section according to the field parameters such as the length and diameter of the pipe and the physical parameters such as the water cut and oil density, substitute the prediction model in step 7 to predict the flow rate required for the oil scouring under the condition, and then calculate the flow rate required for the oil scouring under the corresponding pipe diameter through the formula. It should be pointed out that different water cut and oil sample composition need to obtain the prediction model again according to the method of the embodiment, and then determine the conveying parameters of the pipeline under different low temperature conveying conditions.

Claims

1. A method for determining the wall sticking oil flushing flow rate of extra-high water cut crude oil, characterized in that, The method comprises the following steps: Step 1, preparing crude oil water sample for flushing experiment, taking part of crude oil to prepare wall-sticking and oil-coagulation block by stirring and cooling to oil-coagulation temperature in a simulated stirring tank; Step 2, preparing wall-sticking and oil-coagulation blocks with different masses and fixing them on different test pipe sections, respectively, taking wall-sticking and oil-coagulation blocks with different masses in step 1 and fixing them on the walls of different test pipe sections, controlling temperature drop to the oil-coagulation temperature in step 1, and keeping still for more than 30 minutes to make the wall-sticking and oil-coagulation blocks have the same wall-sticking performance as in step 1; Step 3, debugging the flushing loop device, filling the liquid storage tank and the flushing loop of the flushing loop device with the crude oil water sample prepared in step 1, connecting a circulating pump and a detachable test pipe section to the flushing loop, making the inner diameters of the flushing loop and the test pipe section the same, and respectively arranging temperature control water baths for the flushing loop and the liquid storage tank; Step 4, starting from the test pipe section with the smallest oil-coagulation block, connecting the test pipe sections with the wall-sticking and oil-coagulation blocks in step 2 to the flushing loop, starting the circulating pump, and starting to circulate and flush the crude oil water sample in the flushing loop and the test pipe section from the initial flow rate and the initial temperature, flushing the test pipe section, increasing the flow rate if some oil-coagulation blocks are not flushed away after the test pipe section is flushed at each circulation flow rate for 30 minutes, and continuing to flush until the oil-coagulation blocks in the test pipe section are flushed away, and recording the corresponding oil-coagulation block mass, the flushing flow rate and the flushing temperature; Step 5, replacing the test pipe section with the same mass of oil-coagulation block, reducing the temperature of the loop, starting from the flushing flow rate recorded in the last time, gradually increasing the flushing flow rate, continuing to flush the oil-coagulation block, and recording the corresponding flushing flow rate; repeating the temperature reduction and flushing process in this step until the circulating pump reaches the maximum flow rate and the flushing experiment of the wall-sticking and oil-coagulation block at the corresponding flow rate is completed; Step 6, repeating steps 4 and 5 to flush the oil-coagulation blocks with different masses at different temperatures and recording the oil-coagulation block mass, the flushing flow rate and the flushing temperature; Step 7, according to the oil-coagulation block flushing data, inputting the flushing temperature, the oil-coagulation block mass and the oil-coagulation block flushing flow rate data into the origin software, respectively comparing and selecting the flushing flow rate and the applicability of different models under the influence of factors, establishing a wall-sticking and oil-coagulation block flushing flow rate prediction model for extra-high water-cut crude oil, and determining the flushing flow rate u of the oil-coagulation block with different masses at different temperatures; Step 8, according to the monitoring data of the construction site and the different quality of the calculated oil block in different temperature scouring flow rate u, according to the formula u = 4Q / πd 2 ; In the formula, Q is the flow, d is the pipe diameter, The flushing flow rate is calculated to determine the minimum conveying flow rate and the corresponding oil-coagulation block mass in the construction site.

2. The method for determining the wall sticking oil flushing flow rate of extra-high water cut crude oil according to claim 1, characterized in that, In step 1, the crude oil water sample for the flushing experiment is prepared by using the oil sample taken from the oil pipeline in the field to prepare the crude oil emulsion with a water content similar to that of the produced liquid; the oil-coagulation block is prepared by stirring and mixing the crude oil water sample in the simulated stirring tank, heating to 50℃, then starting to cool the crude oil water sample in the simulated stirring tank at a cooling rate of 0.5℃ / min while stirring, until the temperature is 3-5℃ lower than the oil freezing point, then stirring for 10-20 minutes to make enough oil-coagulation block gather at the bottom of the simulated stirring tank, then opening the bottom discharge valve of the simulated stirring tank to discharge the oil-water mixture, and taking the wall-sticking and oil-coagulation block on the inner wall of the tank for the flushing experiment.

3. The method for determining the wall sticking oil flushing flow rate of extra-high water cut crude oil according to claim 1, characterized in that, In the second step, take different mass of the coagulated oil block, and place the different mass of the coagulated oil block in different test pipe sections respectively, and lower the temperature of the test pipe sections to the coagulated oil temperature in the first step, and keep the temperature constant for 30 min, so that the coagulated oil block is adhered to the wall of the test pipe section, and then the adhesion performance of the coagulated oil block to the wall of the test pipe section is detected through the following pre-flushing experiment: connect the test pipe section to the flushing loop, and fill the flushing loop with the oil-water mixture having the same water content as that in the simulated stirring tank in the first step and having a temperature of the coagulated oil temperature, pre-flush for 20-30 min, and the coagulated oil block is still firmly adhered to the wall; otherwise, place the same mass of the coagulated oil block again, prolong the constant temperature standing time by 30 min, and perform the pre-flushing experiment again until the coagulated oil block is firmly adhered to the wall.

4. The method for determining the wall sticking oil flushing flow rate of extra-high water cut crude oil according to claim 3, characterized in that, In the second step, the pre-flushing flow rate is the same shear rate as the corresponding flow rate in the first step of simulating the stirring tank condensate stirring, which is calculated and determined as follows: In the formula: is the average shear rate of the flushing ring, is the average shear rate of the simulated stirring tank, V is the flushing flow rate, D is the inner diameter of the flushing ring, is the viscosity of the oil-water emulsion in the simulated stirring tank, is the simulated stirring tank speed; The average shear rate of the simulated tank can be calculated after the stirring tank speed and the viscosity of the oil-water emulsion in the tank are determined , and Substitute the pipe inner diameter D into the above formula to convert the scouring flow rate V of the corresponding annular channel of the average shear rate in the simulated stirring tank.

5. The method of claim 1, wherein the method is characterized by: In the third, fourth, fifth and sixth steps, the flushing experiment uses the crude oil water sample having the same composition as the crude oil water sample used for preparing the coagulated oil block in the first step.

6. The method for determining the wall sticking oil flushing flow rate of extra-high water cut crude oil according to claim 4, characterized in that, In the fourth step, the initial flow rate of the flushing is the same as the pre-flushing flow rate in the second step, and the initial temperature is the freezing point of the crude oil; the value of the flow rate of the flushing is increased by 0.012 m / s each time.

7. The method of claim 4, wherein the method is characterized by, In the fifth step, the temperature is lowered by 2℃ each time.

8. The method of claim 1, wherein the method is characterized by, In the seventh step, the flushing flow rate prediction model of the adhered coagulated oil is: u = a * exp(-b) * m -c where a, b, c are constants calculated from software and vary with the oil-water mixture, u is the scouring flow rate, m is the mass of the oil agglomerates, and T is the temperature of the scouring experiment.

9. The method for determining the wall sticking oil flushing flow rate of extra-high water cut crude oil according to claim 3, characterized in that, In the second step, the test pipe section is flushed and wetted with the flushing crude oil water sample before the coagulated oil block is fixedly adhered to the wall.

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