A detection method for determining the temperature of wall-sticking and condensing oil formation in a high-water-content oil collection pipeline
By prefabricating a solidified oil layer adhering to the test pipe section and constructing a loop test system, the problem of inaccurate detection in the existing technology was solved, and the formation temperature of solidified oil plugs in high water-content oil collection pipelines was accurately determined, ensuring safe transportation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2021-09-27
- Publication Date
- 2026-05-12
AI Technical Summary
Existing methods for detecting the formation temperature of oil sticking to the wall cannot accurately simulate the flow conditions in oil collection pipelines with high water content, resulting in inaccurate detection results and difficulty in determining the formation temperature of oil plugs, which poses a risk of pipe rupture.
By prefabricating a condensed oil layer adhering to the pipe wall in the test pipe section and constructing a loop test system, the actual pipe flow conditions were simulated, the morphology of the condensed oil layer being washed by the liquid flow was observed, and the peeling temperature between the condensed oil layer and the pipe wall was determined.
It enables accurate detection of the temperature at which oil condenses and adheres to the pipe walls in high water-content oil collection pipelines, ensuring that the detection results are consistent with the actual pipe flow, reducing the risk of pipe bursts, and providing a safe transport temperature limit.
Smart Images
Figure CN115876828B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of crude oil gathering and transportation, and relates to a detection method for determining the temperature of oil condensation on the wall in high water-content oil gathering pipelines. Background Technology
[0002] As oilfields enter the late stages of development, the large amount of produced water significantly deteriorates the economic viability of the "hot water mixing and gathering" process developed in the early stages of development. Simultaneously, the overall fluidity of the produced fluid improves, making it possible to lower the water mixing temperature or even eliminate the need for heating during oil gathering. However, the fluid flow pattern in pipelines becomes more complex at low temperatures, leading to the formation of oil clumps suspended in the water, resulting in "oil clump sticking to the pipe wall." This reduces the flow area within the pipe, and oil clumps tend to accumulate at the point of reduced pipe diameter, forming "oil plugs" and causing a sharp increase in pipeline pressure drop. Therefore, understanding the formation temperature of "oil clump sticking to the pipe wall" and controlling the transport temperature above this temperature is one of the key technologies for eliminating the need for heating during oil gathering.
[0003] The key to simulating the formation temperature of "wall-adhering solidified oil" in the laboratory lies in constructing a temperature and flow field that matches the actual pipe flow conditions, simulating the adhesion of solidified oil to the pipe wall and the peeling of the wall-adhering layer from the pipe wall under the scouring force of the liquid flow. Existing research methods for detecting the formation temperature of "wall-adhering solidified oil" mainly include the pour point test tube method, the loop method, and the cold finger method.
[0004] The pour point test tube method, based on the crude oil pour point testing standard, uses a standard pour point test tube to hold the sample. The upper layer of the tube is a gelled water-in-oil emulsion, and the lower layer is free water. By tilting the test tube, the free water shears and breaks down the gelled structure. The temperature at which the liquid surface in the test tube stops flowing as the temperature decreases is called the "stagnation point." The "stagnation point" reflects, to some extent, the competition between the yield stress of the gelled oil and the shearing effect of the free water. This "stagnation point" is used in some literature as the formation temperature of "wall-adhering solidified oil." However, this method simulates the stress on the wall-adhering layer during pipeline transportation using the gravity of the lower free water layer in the test tube, neglecting the impact force of the fluid on the solidified oil layer in actual pipeline flow, resulting in a significant discrepancy with reality.
[0005] Indoor loop experiments simulate the flow characteristics of actual pipes using the principle of similarity. The experimental method is widely applied, and components include a mixing tank, peristaltic pump, flow meter, pressure gauge, and temperature-controlled water bath. The loop simulates wall adhesion at different oil flow temperatures. The temperature at which the pressure drop in the test section significantly increases is typically defined as the wall adhesion temperature, which is also used as the limit for the unheated oil collection temperature. However, in high-water-content oil collection pipelines, "oil plugs" easily form, causing a rise in pressure in the test section. The process of the oil plug being pushed out of the pipeline by the liquid flow is similar to pipeline cleaning; after the pipeline is cleaned, the pressure drop in the test section decreases again. Therefore, using traditional loop experimental methods, the pressure drop data obtained over time often fluctuates dramatically, requiring extensive experimental experience for interpretation to identify the so-called "oil adhesion" initiation temperature.
[0006] The cold finger method is also currently used to study the adhesion behavior of solidified oil to pipe walls. However, traditional cold finger experimental devices often have two drawbacks: (1) they cannot simulate the actual pipe flow shear rate. (2) After the oil-water mixture is added to the cold finger all at once, the crude oil consumed by adhesion to the wall cannot be replenished. The flow field inside the cold finger is different from that in the oil collecting pipeline and is inconsistent with the actual pipe flow pattern. The wall thickness inside the cold finger device is uniform, and it can only reflect the adhesion situation in a local pipeline.
[0007] In summary, the current methods for determining the formation temperature of "wall-adhering solidified oil" are controversial and lack universally applicable rules for oilfield promotion. The testing methods need to be further developed. Summary of the Invention
[0008] To overcome the shortcomings of existing technologies, this invention provides a detection method for determining the formation temperature of "wall-sticking solidified oil" in high-water-content oil gathering pipelines. This method can more accurately test the formation temperature of "wall-sticking solidified oil" in high-water-content oil gathering pipelines, and helps to more accurately study the boundary temperature of unheated oil collection. This invention also provides a detection system for determining the formation temperature of "wall-sticking solidified oil" in high-water-content oil gathering pipelines. This system pre-fabricates "wall-sticking solidified oil" in the test pipe section using a mold, and constructs a loop using a peristaltic pump, flow meter, and connecting pipes to simulate the liquid flow in high-water-content pipelines. This makes the stress condition of the wall-sticking solidified oil layer in the detection system closer to the actual pipeline transportation situation. Furthermore, by observing the morphology of the ejected solidified oil, it is possible to conveniently and accurately determine whether the solidified oil has peeled off from the pipe wall, thereby obtaining the formation temperature of the "wall-sticking solidified oil."
[0009] The above-mentioned objective of this invention is achieved through the following technical solution:
[0010] A detection method for determining the temperature of oil condensation on the wall in a high water-content oil collecting pipeline, the detection method specifically includes two steps: (1) a loop preparation step and (2) a loop experiment step;
[0011] (1) In the annular channel preparation stage, first, a coagulated oil layer needs to be prefabricated on the inner wall of the test pipe section equipped with a temperature-controlled interlayer, and then the test pipe section is connected to the test annular channel. The specific method is to adjust the temperature-controlled water bath connecting the temperature-controlled interlayer of the test pipe section to make the circulating water temperature reach T1 (lower than the pour point of crude oil); then insert the mold (a smooth hard plastic long rod with a sealed rubber plug at the end) into the test pipe section to form an annular gap between the inner wall surface of the test pipe section and the outer wall surface of the mold. Pour crude oil into the annular gap through a funnel. Under the cooling effect of the circulating water, the crude oil gels and adheres to the test pipe section wall to form an adhered coagulated oil layer. After the mold is withdrawn, the test pipe section with the coagulated oil layer adhered to the inner wall is connected to the annular channel system, and the temperature-controlled water tank, peristaltic pump, flowmeter, and test pipe section are connected in sequence to form a closed loop.
[0012] (2) In the annular channel experiment stage, first, set the circulating water temperature in the temperature-controlled water tank to T1. After the water temperature reaches the predetermined value, start the speed-regulating peristaltic pump, set the flow rate to Q1 (flow velocity to v1), and the circulating water enters the test pipe section to start scouring the adhered coagulated oil layer, while observing the morphology of the coagulated oil layer scoured out by the liquid flow. The coagulated oil scoured out by the circulating water at T1 temperature will be in a "continuous deformation" state and spread flat on the water surface of the temperature-controlled water tank, indicating that under this condition (Q1, v1, T1), the circulating water can cause the coagulated oil layer to peel off from the pipe wall in the form of yield and continuous deformation, that is, "coagulated oil sticking to the wall" will not occur, then a second group of experiments needs to be carried out. Lower the circulating water temperature of the temperature-controlled water bath to T2 (T2 < T1), and repeat the annular channel preparation stage; the circulating water temperature in the temperature-controlled water tank is T2, and carry out the annular channel experiment again. If the coagulated oil scoured out from the test section is still in a "continuous deformation" state, then lower the circulating water temperature in the temperature-controlled water bath and the temperature-controlled water tank to T3 (T3 < T2 < T1) again for the experiment until a "coagulated oil plug" is found at the end of the test pipeline, that is, the coagulated oil layer does not yield, but the liquid flow overcomes the adhesion force between the coagulated oil and the pipe wall to peel off.
[0013] T3 is the formation temperature of "coagulated oil sticking to the wall" in the oil gathering pipeline under the condition of (Q1, v1). Under this condition, the scouring action of the liquid flow can cause the adhered coagulated oil to peel off from the test pipe section wall, and it is easy to form a "coagulated oil plug", which will cause the pressure drop of the conveying pipe section to rise rapidly and there is a risk of "pipe explosion". Therefore, it is recommended that the minimum safe conveying temperature of this oil gathering pipeline is T3.
[0014] The length of the test pipe section is 400 mm, the inner diameter is 19 mm, and the length of the test pipe section covered with the temperature-controlled interlayer is 300 mm; the diameter of the long rod of the "adhered coagulated oil" production mold is 8 mm, and the thickness of the prefabricated "adhered coagulated oil layer" is 5.5 mm.
[0015] The peristaltic pump outputs in a constant flow rate manner, the flow rate is adjustable, and the flow rate range is 10 - 300 L / h.
[0016] The test tube section is installed 20cm above the circulating water surface in the temperature-controlled water tank; the temperature-controlled water tank, peristaltic pump, flow meter, and temperature-controlled water bath are installed on the same platform.
[0017] The test tube section is equipped with a temperature-controlled interlayer, and the temperature-controlled water bath is connected to the temperature-controlled interlayer of the test tube section to form a closed loop.
[0018] Connect the circulating water in the temperature-controlled water tank to the peristaltic pump, flow meter, and test pipe section to form a closed loop two.
[0019] On the other hand, the present invention also provides a system for implementing the above-mentioned detection method. The detection system includes at least: a temperature-controlled water tank, a peristaltic pump, a flow meter, a temperature-controlled water bath, a test pipe section, and a prefabricated mold for the oil layer adhering to the wall.
[0020] The prefabrication mold for the wall-adhering solidified oil layer includes a smooth, hard plastic rod with a sealing rubber plug at one end and a funnel. By inserting the mold into a test pipe section, an annular gap is formed between the inner wall of the test pipe section and the outer wall of the mold. Crude oil is injected into the annular gap through the funnel. Under the cooling effect of circulating water, the crude oil gels and adheres to the pipe wall, forming the wall-adhering solidified oil layer.
[0021] Connect the test pipe section with the condensed oil layer on the inner wall to the loop system. Figure 2 As shown in the diagram, the loop system is specifically designed so that the inlet end of the test pipe section is connected to the outlet of the flow meter via a connecting pipe, and the outlet end of the test pipe section is led out via a connecting pipe and connected to the liquid level of the temperature-controlled water tank; the temperature-controlled water tank, peristaltic pump, flow meter and test pipe section are connected in sequence to form an experimental loop.
[0022] The test tube section is equipped with a temperature-controlled interlayer. The temperature-controlled water bath is connected to the temperature-controlled interlayer of the test tube section to form a closed loop one. The circulating water in the temperature-controlled water tank is connected to the peristaltic pump, flow meter, and test tube section to form a closed loop two.
[0023] Furthermore, peristaltic pumps with constant flow function can achieve better loop flow control.
[0024] Furthermore, the temperature-controlled water tank has a power greater than 1.5kW and is an open water tank, which facilitates observation of the morphology of the flushed-out solidified oil.
[0025] Furthermore, the power of the temperature-controlled water bath is greater than 2.5kW.
[0026] Furthermore, the connecting pipe is made of PVC, thereby achieving the effect of heat insulation and preventing breakage.
[0027] This invention constructs a fluid flow path to establish a pre-formed solidified oil adhering layer on the wall, observes the scouring state of the pre-formed adhering layer under the continuous scouring action of the fluid flow, and quantitatively simulates the actual pipeline flow with the flow rate, so that the detection process of the "adhering solidified oil" formation temperature is closer to the actual situation of oilfield oil gathering pipeline transportation.
[0028] The advantages of this invention compared to the prior art are:
[0029] (1) The method for detecting the formation temperature of sticky solidified oil in high water-content oil collecting pipelines provided by the present invention, on the one hand, realizes the formation of sticky solidified oil layer at a specific temperature by prefabricating sticky solidified oil layer in the test pipe section; on the other hand, it simulates the liquid flow in the actual oil collecting pipeline by constructing an experimental loop; ensuring that the stress of sticky solidified oil layer during the flushing process is consistent with the actual pipeline flow; and making up for the defects of the pour point test tube method and cold finger device that cannot completely simulate the stress of sticky solidified oil layer in pipeline flow.
[0030] (2) The method for detecting the temperature of oil sticking to the wall in a high water content oil collection pipeline provided by the present invention forms a closed loop two for flushing circulating water and a closed loop one for temperature control of the test pipe section circulating water, thereby establishing a temperature field for "oil sticking to the wall"; by controlling the temperature of the circulating water in the water tank to be consistent with the temperature of the circulating water in the temperature control water bath of the test pipe section, and by ensuring that the temperature is lower than the wax precipitation point of the crude oil sample, the detection of the temperature of "oil sticking to the wall" under specific temperature field conditions is realized.
[0031] (3) The method for detecting the temperature of oil condensation on the wall in a high water content oil collection pipeline provided by the present invention is based on the idea that the flow velocity in the loop is equal to the flow velocity in the actual pipeline. A peristaltic pump is set in the experimental loop. By changing the speed of the peristaltic pump, the flow velocity of the pipeline is adjusted, thereby simulating the actual pipeline flow and making the detection process of the temperature of oil condensation on the wall closer to the actual situation of the high water content oil collection pipeline.
[0032] (4) The method for detecting the formation temperature of condensed oil adhering to the wall in a high water content oil collection pipeline provided by the present invention proposes to use an open temperature-controlled water tank to contain the circulating water of the second closed loop, and at the same time collect the flushed material of the test pipe section to facilitate observation of the morphology of the flushed condensed oil. By determining the transition temperature of the flushed condensed oil morphology from "deformable" to "condensed oil plug", the formation temperature of "condensed oil adhering to the wall" under the flow rate condition is determined. The judgment basis is easy to grasp, which solves the defect of the existing loop test device that relies on pressure difference changes, where the pressure difference data fluctuates greatly and it is not easy to judge the formation temperature of "condensed oil adhering to the wall".
[0033] (5) The simulation system for detecting the formation temperature of condensed oil on the wall in a high water content oil collection pipeline provided by the present invention, on the one hand, ensures that the stress condition of the condensed oil layer on the wall during the flushing process is consistent with the actual pipeline flow by pre-fabricating a condensed oil layer on the wall at a specific temperature in the controlled test section and constructing an experimental loop; it makes up for the defects of the pour point test tube method and cold finger device, which cannot completely simulate the stress condition of the condensed oil layer on the wall in the pipeline flow; on the other hand, it determines the formation temperature of "condensed oil on the wall" under the flow rate condition by determining the transition temperature of the flushed condensed oil morphology from "deformable" to "condensed oil plug". The judgment basis is easy to grasp and solves the defects of large fluctuation of pressure difference data and difficulty in judging the turning point in the current loop test device. Attached Figure Description
[0034] The present invention will now be described in further detail with reference to the accompanying drawings.
[0035] Figure 1 This is a schematic diagram of a prefabricated oil-coated layer in the detection system for determining the formation temperature of oil-coated solidification in a high water-content oil-collecting pipeline in Example 1.
[0036] Figure 2 This is a schematic diagram of the test conducted in the detection system for determining the temperature of oil condensation on the wall of a high water-content oil collecting pipeline in Example 1.
[0037] Figure 3 This is a schematic diagram of the solidified oil that was ejected from the test pipe section in Example 1 and was able to deform and spread on the water surface.
[0038] Figure 4 This is a schematic diagram of the condensed oil that was flushed out of the test pipe section in the form of a "condensed oil plug" in Example 1.
[0039] In the diagram: 1. Long rod, 2. Rubber stopper, 3. Funnel, 4. Test pipe section; 5. Circulating water; 6. Temperature-controlled water tank; 7. Peristaltic pump; 8. Flow meter; 9. Temperature-controlled water bath; 10. Water bath circulation pipeline; 11. Pre-cast wall-adhesive solidified oil layer. Detailed Implementation
[0040] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.
[0041] The method of the present invention used in the embodiments includes two stages: a loop preparation stage and a loop experiment stage.
[0042] In the loop preparation stage, first, a coagulated oil layer needs to be prefabricated on the inner wall of the test pipe section equipped with a temperature-controlled interlayer, and then the test pipe section is connected to the test loop. The method is to adjust the temperature-controlled water bath connecting the temperature-controlled interlayer of the test section to make the circulating water temperature reach T1 (lower than the pour point of the crude oil); then insert the mold (a smooth hard plastic long rod with a sealed rubber plug at the end) into the test pipe section to form an annular gap between the inner wall surface of the test pipe section and the outer wall surface of the mold. Inject crude oil into the annular gap. Under the cooling effect of the circulating water in the temperature-controlled water bath (for a duration not less than 30 minutes), the crude oil gels and adheres to the wall of the test pipe section, forming a sticky wall coagulated oil layer. Carefully extract the mold to obtain the test pipe section with the prefabricated sticky wall coagulated oil layer.
[0043] In the loop experiment stage: Connect the test pipe section with the coagulated oil layer attached to its inner wall to the loop system, and complete the sequential connection of the temperature-controlled water tank, peristaltic pump, flowmeter, and test pipe section to form a closed loop. In the loop experiment stage, first set the circulating water temperature in the temperature-controlled water tank to T1. After the water temperature reaches the predetermined value, start the speed-adjustable peristaltic pump, set the flow rate to Q1 (flow velocity to v1), and the circulating water enters the test pipe section to start scouring the sticky wall coagulated oil layer, while observing the shape of the coagulated oil layer scoured by the liquid flow.
[0044] (1) The coagulated oil scoured by the circulating water at the temperature of T1 will be in a "continuous deformation" state and spread flat on the water surface of the temperature-controlled water tank, indicating that under this condition (Q1, v1, T1), the circulating water can cause the coagulated oil layer to peel off from the pipe wall in the form of yield and continuous deformation, then a second set of experiments needs to be carried out.
[0045] (2) Lower the circulating water temperature of the temperature-controlled water bath to T2 (T2 < T1), and repeat the loop preparation stage; the circulating water temperature in the temperature-controlled water tank is T2, and carry out the loop experiment again. If the coagulated oil scoured from the test section is still in a "continuous deformation" state, then lower the circulating water temperature in the temperature-controlled water bath and the temperature-controlled water tank to T3 (T3 < T2 < T1) again for the experiment until a "columnar coagulated oil slug" is found at the end of the test pipeline, that is, the coagulated oil layer does not yield, but the liquid flow overcomes the adhesion force between the coagulated oil and the pipe wall to peel off.
[0046] T3 is the critical formation temperature of "sticky wall coagulated oil" in the gathering pipeline. Under this condition, the liquid flow scouring can achieve the peeling of the coagulated oil layer from the pipe wall, and the coagulated oil blocks are easy to form "columnar coagulated oil slugs", which will cause the pressure drop of the conveying pipe section to rise rapidly and there is a risk of "pipe explosion". Therefore, it is recommended that the minimum safe transportation temperature of this gathering pipeline is T3.
[0047] (3) Change the speed of the peristaltic pump (change the flow rate Q and the liquid flow velocity v), and repeat the above experimental steps to obtain the formation temperature of "sticky wall coagulated oil" of the crude oil under different liquid flow conditions.
[0048] Example 1
[0049] For Xinmin crude oil (pour point 36℃), the test temperatures were selected as 30℃, 32℃, and 34℃; the test loop flow rates were selected as 50, 100, 150, and 200 L / h.
[0050] Taking a test temperature of 34℃ and a loop flow rate of 50L / h as an example:
[0051] (1) In the preparation stage of the loop, the first step is to pre-fabricate the oil layer on the inner wall of the test pipe section equipped with the temperature control jacket. Figure 1 ).
[0052] The method involves adjusting the temperature-controlled water bath in the temperature-controlled jacket of the test section to achieve a circulating water temperature of 34℃ (below the pour point of crude oil). Then, a mold (a smooth, hard plastic rod with a sealing rubber plug at one end) is inserted into the test pipe section, creating an annular gap between the inner wall of the test pipe section and the outer wall of the mold. Crude oil is injected into this annular gap, and under the cooling effect of the circulating water, the crude oil gels and adheres to the pipe wall, forming a wall-adhering solidified oil layer.
[0053] (2) After the mold is removed, the test tube section with the oil layer attached to the inner wall is connected to the loop system to complete the sequential connection of the temperature control water tank, peristaltic pump, flow meter and test tube section to form a closed loop.
[0054] In the loop test, the temperature of the circulating water in the temperature-controlled water tank was first set to 34℃. After the water temperature reached the predetermined value, the variable speed peristaltic pump was started and the flow rate was set to 50L / h. The circulating water entered the test pipe section and began to flush the oil layer adhering to the wall. At the same time, the morphology of the oil layer flushed out by the liquid flow was observed.
[0055] It was found that the condensed oil flushed out by the circulating water at 34℃ would be in a state of "continuous deformation," spreading evenly on the surface of the temperature-controlled water tank, as shown in the attached image. Figure 3 As shown, this indicates that under these conditions (50L / h, 0.27m / s, 34℃), the circulating water can cause the condensed oil layer to peel off from the pipe wall in the form of yielding and continuous deformation, that is, "condensed oil sticking to the wall" will not occur.
[0056] Stop the pump in the loop and allow the remaining circulating water in the test pipeline to flow back to the temperature-controlled water tank by gravity. Then, remove the test pipe section from the loop, clean and dry the inner wall, and prepare for the next experiment.
[0057] Then, an experiment was conducted at a test temperature of 32℃ and a loop flow rate of 50L / h:
[0058] (1) Reduce the temperature of the circulating water in the temperature-controlled water bath to 32°C and repeat the loop preparation process; to obtain the test pipe section with the prefabricated wall-adhering solidified oil layer.
[0059] (2) The test pipe section is connected to the loop system to form a closed loop. The circulating water temperature in the temperature-controlled water tank is 32℃, and the loop experiment is carried out again.
[0060] It was found that the condensed oil flushed out by the circulating water at 32℃ would be in a "condensed oil plug" state, and would not spread out or deform when it fell onto the surface of the temperature-controlled water tank, as shown in the attached image. Figure 4 As shown, under these conditions (50 L / h, 0.27 m / s, 32℃), the circulating water cannot cause the condensate layer to yield and deform, but it is sufficient to cause the condensate layer to peel off from the pipe wall. That is, 32℃ is the critical temperature for crude oil to "stick to the wall and solidify" under these conditions.
[0061] Then, an experiment was conducted at a test temperature of 30℃ and a loop flow rate of 50L / h:
[0062] (1) Reduce the temperature of the circulating water in the temperature-controlled water bath to 30°C and repeat the loop preparation process; to obtain the test pipe section with the prefabricated wall-adhering solidified oil layer.
[0063] (2) The test pipe section is connected to the loop system to form a closed loop. The circulating water temperature in the temperature-controlled water tank is 30℃, and the loop experiment is carried out again.
[0064] It was found that no condensed oil was flushed out after 1 hour of circulating water flushing at 30℃. This indicates that under these conditions (50L / h, 0.27m / s, 30℃), the circulating water cannot cause the condensed oil layer to detach from the pipe wall. In other words, the adhesion force between the condensed oil layer and the pipe wall is greater than the flushing force of the liquid flow.
[0065] The experimental results of the condensed oil adhering to the wall layer under other circulating water flow conditions are shown in Table 1. As can be seen from the data in the table, under the four conditions of (50L / h, 0.27m / s), (100L / h, 0.55m / s), (150L / h, 0.83m / s), and (200L / h, 1.11m / s), the formation temperatures of "adhered oil adhering to the wall" in Xinmin crude oil are 32℃, 30℃, 30℃, and 30℃, respectively.
[0066] Table 1. Results of scouring experiments on Xinmin crude oil under different test flow rates and temperatures.
[0067]
[0068]
[0069] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.
Claims
1. A method for determining the formation temperature of oil sticking to the wall in a high water-content oil gathering pipeline, characterized in that, The detection method specifically includes two steps: (1) the preparation of the ring track and (2) the test of the ring track; (1) In the preparation of the loop, firstly, a layer of solidified oil needs to be pre-made on the inner wall of the test tube section equipped with a temperature control jacket, and then the test tube section is connected to the test loop. The specific method is to adjust the temperature control water bath connected to the temperature control jacket of the test tube section so that the circulating water temperature reaches T1, which is lower than the pour point of crude oil. Then, insert the mold, with a smooth hard plastic long rod with a sealing rubber plug at the end, into the test tube section to form an annular gap between the inner wall of the test tube section and the outer wall of the mold. Crude oil is injected into the annular gap through a funnel. Under the cooling effect of circulating water, the crude oil gels and adheres to the test pipe section on the pipe wall, forming a solidified oil layer. After the mold is removed, the test pipe section with the solidified oil layer on the inner wall is connected to the loop system, completing the sequential connection of the temperature control water tank, peristaltic pump, flow meter and test pipe section to form a closed loop. (2) In the annular channel experiment, first set the temperature of the circulating water in the temperature-controlled water bath to T1. After the water temperature reaches the predetermined value, start the peristaltic pump, set the flow rate to Q1, and the flow velocity to v 1. The circulating water enters the test pipe section and begins to scour the sticky wall condensate layer. At the same time, observe the shape of the condensate layer scoured by the liquid flow; the condensate flushed out by the circulating water at the temperature of T1 will be in a "continuous deformation" state and spread out on the water surface of the temperature-controlled water bath, indicating that under this condition: Q1, v 1, T1. The circulating water can cause the condensate layer to peel off from the pipe wall in the form of yielding and continuous deformation, that is, "condensate sticking to the wall" does not occur. Then, the second group of experiments needs to be carried out; reduce the temperature of the circulating water in the temperature-controlled water bath to T2, where T2 < T1, and repeat the annular channel preparation process; when the temperature of the circulating water in the temperature-controlled water bath is T2, conduct the annular channel experiment again; if the condensate flushed out from the test section is still in a "continuous deformation" state, then reduce the temperature of the circulating water in the temperature-controlled water bath and the temperature-controlled water bath to T 3， T3 < T2 < T1, and conduct the experiment again until a "condensate plug" is found at the end of the test pipe, that is, the condensate layer does not yield, but the liquid flow overcomes the adhesion between the condensate and the pipe wall to cause peeling; T3 is Q1. v The formation temperature of "wall-adhering solidified oil" in the oil collection pipeline under condition 1; Under this condition, the liquid flow scouring action can cause the wall-adhering solidified oil to peel off from the test pipe section wall, which easily forms a "solidified oil plug", which will cause the pressure drop of the delivery pipe section to rise rapidly, and there is a risk of "pipe bursting". Therefore, the minimum safe delivery temperature of the oil collection pipeline is T3.
2. The detection method for determining the formation temperature of oil sticking to the wall in a high water-content oil gathering pipeline as described in claim 1, characterized in that, The test tube section is 400 mm long and 19 mm in inner diameter, and the test tube section covered with the temperature control jacket is 300 mm long; the long rod of the mold for making the "wall-adhering solidified oil" has a diameter of 8 mm, and the thickness of the prefabricated "wall-adhering solidified oil layer" is 5.5 mm.
3. The detection method for determining the formation temperature of oil sticking to the wall in a high water-content oil gathering pipeline as described in claim 2, characterized in that, The peristaltic pump outputs a constant flow rate, which is adjustable and ranges from 10 to 300 L / h.
4. The detection method for determining the formation temperature of oil sticking to the wall in a high water-content oil gathering pipeline as described in claim 3, characterized in that, The test tube section is installed 20cm above the circulating water surface in the temperature-controlled water tank; the temperature-controlled water tank, peristaltic pump, flow meter, and temperature-controlled water bath are installed on the same platform.
5. The detection method for determining the formation temperature of oil sticking to the wall in a high water-content oil gathering pipeline as described in claim 4, characterized in that, The test tube section is equipped with a temperature control jacket, and the temperature control water bath is connected to the temperature control jacket of the test tube section to form a closed loop. Connect the circulating water in the temperature-controlled water tank to the peristaltic pump, flow meter, and test pipe section to form a closed loop two.
6. A detection system for implementing the detection method of claim 1, characterized in that, The testing system includes at least: a temperature-controlled water tank, a peristaltic pump, a flow meter, a temperature-controlled water bath, a test tube section, and a mold for the oil layer adhering to the wall.
7. The detection system as described in claim 6, characterized in that, The mold for the sticky oil layer includes a smooth, hard plastic rod with a sealing rubber plug at the end and a funnel; by inserting the mold into the test tube section, an annular gap is formed between the inner wall of the test tube section and the outer wall of the mold; Crude oil is injected into the annular gap through a funnel. Under the cooling effect of circulating water, the crude oil gels and adheres to the pipe wall, forming a wall-adhering solidified oil layer.
8. The detection system as described in claim 7, characterized in that, The test tube section with the condensed oil layer on the inner wall is connected to the loop system. Specifically, the inlet end of the test tube section is connected to the outlet of the flow meter through a connecting pipe, and the outlet end of the test tube section is led out through a connecting pipe and connected to the liquid level of the temperature-controlled water tank. The temperature-controlled water tank, peristaltic pump, flow meter and test tube section are connected in sequence to form an experimental loop.
9. The detection system as described in claim 8, characterized in that, The test tube section is equipped with a temperature-controlled interlayer. The temperature-controlled water bath is connected to the temperature-controlled interlayer of the test tube section to form a closed loop one. The circulating water in the temperature-controlled water tank is connected to the peristaltic pump, flow meter, and test tube section to form a closed loop two.
10. The detection system as described in claim 9, characterized in that, The temperature-controlled water tank has a power greater than 1.5kW and is an open water tank. The connecting pipe is made of PVC.