Method and device for testing transport and migration capability of cross-linked polymer for profile control of oil field

Abstract

The invention relates to a method and a device for testing the transport and migration capability of a cross-linked polymer for oilfield profile control. The whole experiment is carried out in a temperature-resistant and pressure-resistant reaction kettle; the method comprises the following steps: checking the leakproofness of a reaction kettle, checking the connectivity and leakproofness of a long rock core, vacuumizing the long rock core and saturating water, checking the secondary leakproofness of the reaction kettle and the long rock core, calculating the water permeability of the long rock core by water drive, mixing a polymer and a cross-linking agent on line, pre-shearing the cross-linked polymer and performing a cross-linked polymer injection experiment. The method comprises the following steps: monitoring the pressure of a long-core on-way pressure measuring point during injection of a cross-linked polymer, collecting long-core on-way produced liquid through a sampling point, measuring to obtain viscosity and concentration data of the produced liquid, and realizing on-line mixing of the polymer and a cross-linking agent by adopting a metal mixer, so that the dynamic cross-linking effect of a system in a stratum can be simulated; the pre-shearing operation can effectively avoid abnormal increase of an injection pressure value caused by an end face effect, the accuracy of experimental data is improved, and guidance is provided for evaluation and optimization of the transportation and migration capability of the cross-linked polymer in an oil field.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field technology, and more specifically, to a method and apparatus for testing the transport and migration capabilities of cross-linked polymers used in oilfield profile control. Background Technology

[0002] Cross-linked polymers can effectively improve reservoir water absorption profiles and expand the macroscopic swept volume of injected water. They are one of the most commonly used profile control agents in oilfields, and it is essential to screen cross-linked polymers suitable for target reservoirs.

[0003] The transport and migration capacity of cross-linked polymers reflects their ability to penetrate deep into the reservoir and is an important indicator for selecting the best cross-linked polymers. Long core transport and migration experiments are one of the methods for evaluating the transport capacity of cross-linked polymers.

[0004] In conventional long core transport experiments, the core airtightness checks, vacuuming, and saturation water processes are all conducted outside the temperature- and pressure-resistant reactor. When the core is subsequently placed into the reactor and pressure monitoring points are connected, pipeline loosening may occur, allowing air to enter the core and increasing experimental complexity and uncertainty. Furthermore, the mixture of polymer and crosslinking agent placed in an intermediate container is prone to crosslinking to form a gel. Direct injection into the long core can easily lead to end-face effects, causing blockage at the injection end, abnormal pressure increases, and affecting the accuracy of experimental data. Summary of the Invention

[0005] The purpose of this invention is to provide a method for testing the transport and migration capacity of cross-linked polymers used in oilfield profile control. The method involves conducting a sealing test, vacuuming, and saturation process on long core samples in a high-temperature and high-pressure resistant reactor. This simulates the high-temperature and high-pressure environment of the formation, effectively reducing the probability of air entering the core during the experiment, improving the accuracy of the experimental data, and providing guidance for the evaluation and optimization of the transport and migration capacity of cross-linked polymers in oilfields.

[0006] Another object of the present invention is to provide an apparatus for testing the transport and migration capabilities of cross-linked polymers used in oilfield profile control.

[0007] The technical solution of the present invention:

[0008] This invention provides a method for testing the transport and migration capabilities of cross-linked polymers used in oilfield profile control, comprising the following steps:

[0009] S1. Perform a leak test on the temperature and pressure resistant reactor;

[0010] S2. Place the long core into a temperature- and pressure-resistant reactor and pressurize it to check the continuity and airtightness of the long core;

[0011] S3. Vacuum the long core sample and perform saturated water operation;

[0012] S4. Conduct a second airtightness check on the temperature and pressure resistant reactor and long core samples;

[0013] S5. Simulate formation water from the target reservoir by injecting it into the long core using an injection pump, and calculate the water permeability of the long core.

[0014] S6. The polymer and crosslinking agent are mixed online using a metal mixer to obtain a crosslinked polymer, which is then injected into a high-permeability cylindrical core to achieve pre-shearing.

[0015] S7. The pre-sheared cross-linked polymer is directly injected into the long core. After the injection volume reaches the target PV number, it is switched to subsequent water flooding. The pressure data along the long core and the viscosity and concentration data of the produced fluid are obtained. The transport and migration capacity of the cross-linked polymer is evaluated based on the pressure data along the long core and the viscosity and concentration data of the produced fluid.

[0016] Furthermore, S1 above includes the following steps:

[0017] S1.1. Install plugs inside the pressure measuring point and sampling point of the reactor, and connect them to the external confining pressure pump;

[0018] S1.2. Add water to the temperature and pressure resistant reactor and pressurize it to 1MPa-3MPa, and perform a tightness check at each point.

[0019] Furthermore, S2 above includes the following steps:

[0020] S2.1. Place the long core into the temperature- and pressure-resistant reactor. The injection end and pressure measurement point of the long core are connected to the pressure measurement point of the reactor through a pressure-resistant metal pipeline. The sampling point and extraction end of the long core are connected to the sampling point of the reactor through a pressure-resistant metal pipeline.

[0021] S2.2. Add water to the temperature and pressure resistant reactor, connect the air pump to the long core injection end through the reactor pressure measuring point, connect a PVC pipe to the long core extraction end, and extend the other end of the PVC pipe into the water. Close all other long core pressure measuring points and long core sampling points, pressurize to 1MPa-2MPa, and inject air into the long core to check its connectivity.

[0022] S2.3. Close the extraction end of the long core and perform a sealing test on the long core.

[0023] Furthermore, S3 above includes the following steps:

[0024] S3.1. Vacuum the long core through the pressure measurement point of the reactor until the vacuum pressure is -0.09MPa to -0.1MPa, then stop evacuating.

[0025] S3.2. After the pressure stabilizes, maintain the pressure for 60-120 minutes;

[0026] S3.3. Saturate the long core sample with water through the sampling point of the reactor.

[0027] Furthermore, S4 above includes the following steps:

[0028] S4.1. Connect pressure sensors to the pressure measurement point and sampling point of the reactor connected to the long core pressure measurement point, injection end and sampling point, close the remaining pressure measurement point and sampling point of the reactor, open the vent end of the temperature and pressure resistant reactor, and inject water through the bottom drain to discharge the air in the temperature and pressure resistant reactor.

[0029] S4.2. Close the drain end and the outlet, increase the confining pressure, and observe the pressure stability of the confining pressure, the pressure measuring point of the long core, and the injection end of the long core.

[0030] S4.3. Heat and continue to observe the pressure stability in S4.2 to achieve a secondary airtightness check of the temperature and pressure resistant reactor and long core.

[0031] Furthermore, the confining pressure value for increasing the confining pressure in S4.2 is 3MPa-5MPa, and the heating temperature in S4.3 is 60℃-80℃.

[0032] Furthermore, the above S5 includes the following steps:

[0033] S5.1. Set the injection pump displacement rate to 0.1 mL / min-0.5 mL / min and inject simulated formation water from the target reservoir into the long core.

[0034] S5.2. Record the pressure at the injection end and pressure measurement point of the long core at intervals, as well as the liquid output at the production end of the long core, and calculate the water permeability of the long core based on Darcy's formula.

[0035] Furthermore, the above-mentioned S7 includes the following steps:

[0036] S7.1. Displace the long core by injecting pre-sheared cross-linked polymer at a constant rate of 0.1 mL / min-0.5 mL / min, and record the pressure at the injection end, pressure measurement point and sampling point of the long core at intervals, as well as the liquid output at the extraction end;

[0037] S7.2. Intermittently test the viscosity and concentration of the sampled fluid at the sampling point and the sampled fluid at the sampling end, and continuously inject the pre-sheared cross-linked polymer body until the target PV number is reached, and then switch to subsequent water flooding;

[0038] S7.3. Set the subsequent water drive displacement rate to 0.1 mL / min-0.5 mL / min, and record the pressure at the injection end, pressure measurement point and sampling point of the long core at intervals, as well as the liquid output at the production end;

[0039] S7.4. Intermittently test the viscosity and concentration of the produced fluid at the production end. When the viscosity of the produced fluid at the production end is stable and the viscosity difference with water is 0.1 mP·s-0.5 mP·s, the experiment is terminated, and the pressure data along the long core and the viscosity and concentration data of the produced fluid are obtained.

[0040] S7.5. Evaluate the transport and migration capabilities of crosslinked polymers based on the obtained data.

[0041] On the other hand, the present invention provides an apparatus for testing the transport and migration capacity of cross-linked polymers used in oilfield profile control, comprising a temperature- and pressure-resistant reactor, wherein the temperature- and pressure-resistant reactor is provided with a plurality of reactor pressure measuring points and a plurality of reactor sampling points; the reactor pressure measuring points are connected to core holders via pressure-resistant metal pipelines; a pressure port is provided on the side wall of the temperature- and pressure-resistant reactor, and each pressure port and core holder is connected to a confining pressure pump, and the confining pressure pump is provided with a confining pressure gauge; the end of the core holder away from the temperature- and pressure-resistant reactor is connected to a metal mixer, and the metal mixer is connected to two sets of feeding mechanisms.

[0042] Furthermore, the feeding mechanism includes a first intermediate container, a second intermediate container, and a horizontal pump. The bottoms of both the first and second intermediate containers are connected to the horizontal pump, and the horizontal pump is also connected to a container filled with white oil. The tops of both the first and second intermediate containers are connected to a metal mixer.

[0043] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0044] 1. Conducting airtightness checks, vacuuming, and saturation water processes for long rock cores inside a high-temperature and high-pressure resistant reactor can simulate the high-temperature and high-pressure environment of the formation, effectively reducing the probability of air entering the rock core during the experiment.

[0045] 2. Using a metal mixer to mix polymers and crosslinking agents online avoids gelation of the system before injection into long cores, which is beneficial for better simulating the dynamic gelation of the system in the formation.

[0046] 3. The pre-shearing step allows the cross-linked polymer to be stretched and sheared by the porous medium before injection into long cores, effectively avoiding the abnormal increase in injection pressure caused by end-face effect when it is injected into long cores, improving the accuracy of experimental data, and providing guidance for the evaluation and optimization of the transport and migration capacity of cross-linked polymers in oilfields.

[0047] 4. Recording data such as injection end pressure, pressure at long core pressure measurement points, long core extraction end pressure, extraction end fluid volume, extraction fluid viscosity and concentration at intervals during each stage of the experiment allows for detailed monitoring of the cross-linked polymer injection and migration process, which helps to analyze the gel's migration behavior in the core and accurately assess its transport capacity.

[0048] 5. Using a temperature- and pressure-resistant reactor with controllable confining pressure and temperature for experiments helps to make the experimental environment closer to the actual reservoir conditions, enhances the practicality and reference value of the experimental results, and ensures that the test results are effective in real applications.

[0049] 6. After continuously injecting the cross-linked polymer to the target PV number, switch to subsequent water flooding until the viscosity of the produced fluid is close to that of water, and end the experiment. This allows for complete monitoring of the cross-linked polymer migration and displacement effect. By measuring the pressure changes along the long core and the changes in the viscosity and concentration of the produced fluid, the location and migration distance of the cross-linked polymer can be determined, providing clear evaluation indicators for transport capacity. Attached Figure Description

[0050] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0051] Figure 1 This is a schematic flowchart of the method of the present invention;

[0052] Figure 2 This is a schematic diagram of the experimental apparatus of the present invention;

[0053] Figure 3 This is a schematic diagram of the temperature- and pressure-resistant reactor structure of the present invention;

[0054] Figure 4 This is a schematic diagram of the 8m long core structure in this invention.

[0055] Icons: 100-Temperature and pressure resistant reactor; 101-Top cover; 102-Bottle body; 103-Drain end; 104-Drain outlet; 110-Reactor pressure measuring point; 120-Reactor sampling point; 130-Core support; 131-Heating tube; 140-Pressure port; 150-Measuring cylinder; 200-Confining pressure pump; 210-Confining pressure gauge; 300-Core holder; 400-Metal mixer; 510-First intermediate container; 520-Second intermediate container; 530-Horizontal flow pump; 540-Container; 610-Injection end; 620-Output end; 630-Long core pressure measuring point; 640-Long core sampling point; 650-Connection point. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0057] Example

[0058] Please refer to Figure 1 This invention provides a method for testing the transport and migration capabilities of cross-linked polymers used in oilfield profile control, comprising the following steps:

[0059] S1. Perform a leak test on the temperature and pressure resistant reactor;

[0060] S2. Place the long core into a temperature- and pressure-resistant reactor and pressurize it to check the continuity and airtightness of the long core;

[0061] S3. Vacuum the long core sample and perform saturated water operation;

[0062] S4. Conduct a second airtightness check on the temperature and pressure resistant reactor and long core samples;

[0063] S5. Simulate formation water from the target reservoir by injecting it into the long core using an injection pump, and calculate the water permeability of the long core.

[0064] S6. The polymer and crosslinking agent are mixed online using a metal mixer to obtain a crosslinked polymer, which is then injected into a high-permeability cylindrical core to achieve pre-shearing.

[0065] S7. The pre-sheared cross-linked polymer is directly injected into the long core. After the injection volume reaches the target PV number, it is switched to subsequent water flooding. The pressure data along the long core and the viscosity and concentration data of the produced fluid are obtained. The transport and migration capacity of the cross-linked polymer is evaluated based on the pressure data along the long core and the viscosity and concentration data of the produced fluid.

[0066] It should be noted that the high-permeability cylindrical core is a homogeneous artificial core, measuring φ2.5cm × 10cm, with a permeability of 3000-5000 × 10⁻⁶. -3 μm 2 High-permeability cylindrical rock cores need to be replaced every 12-24 hours.

[0067] This invention utilizes a high-temperature and high-pressure resistant reactor to perform core sealing checks, vacuuming, and water saturation processes. This simulates the high-temperature and high-pressure environment of the formation, effectively reducing the probability of air entering the core during the experiment. Furthermore, the use of online mixing of polymers and crosslinking agents prevents the system from gelling before injection into long cores, facilitating a better simulation of dynamic gelation within the formation. The pre-shearing step stretches and shears the crosslinked polymer through the porous medium before injection into long cores, effectively preventing abnormal pressure increases due to end-face effects and improving the accuracy of experimental data.

[0068] Furthermore, conventional cross-linked polymer transport capacity testing experiments are conducted using centimeter-scale cylindrical or square cores. The core scale differs significantly from the reservoir scale, making it difficult to simulate the long-distance transport, dynamic gelation, and retention / plugging processes of cross-linked polymers in real-world reservoir conditions. This invention utilizes meter-scale long cores to conduct cross-linked polymer transport capacity testing experiments, which can better simulate the long-distance transport, dynamic gelation, and retention / plugging processes of cross-linked polymers. By setting pressure measurement and sampling points along the long core, monitoring pressure data, and testing the viscosity and concentration of produced fluid, the dynamic gelation and retention distribution of cross-linked polymers within the core can be determined. Simultaneously, to accurately simulate the high-temperature and high-pressure conditions of real formations, the entire experiment is conducted in a temperature- and pressure-resistant reactor.

[0069] Furthermore, S1 includes the following steps:

[0070] S1.1. Install plugs inside the pressure measuring point and sampling point of the reactor, and connect them to the external confining pressure pump;

[0071] S1.2. Add water to the temperature and pressure resistant reactor and pressurize it to 1MPa-3MPa, and perform a tightness check at each point.

[0072] It should be noted that the plug is made of corrosion-resistant metal to ensure a tight fit with the pressure testing point interface. After water injection and pressurization, observe whether there is liquid leakage or pressure decay at the pressure testing point, weld, and interface to determine the airtightness of the reactor. A reactor with good airtightness can effectively maintain a high temperature and high pressure environment, providing a stable foundation for subsequent simulation of formation conditions.

[0073] Furthermore, S2 includes the following steps:

[0074] S2.1. Place the long core into the temperature- and pressure-resistant reactor. The injection end and pressure measurement point of the long core are connected to the pressure measurement point of the reactor through a pressure-resistant metal pipeline. The sampling point and extraction end of the long core are connected to the sampling point of the reactor through a pressure-resistant metal pipeline.

[0075] S2.2. Add water to the temperature and pressure resistant reactor, connect the air pump to the long core injection end through the reactor pressure measuring point, connect a PVC pipe to the long core extraction end, and extend the other end of the PVC pipe into the water. Close all other long core pressure measuring points and long core sampling points, pressurize to 1MPa-2MPa, and inject air into the long core to check its connectivity.

[0076] S2.3. Close the extraction end of the long core and perform a sealing test on the long core.

[0077] It should be noted that the connections between the injection end, pressure measuring point, sampling point, and extraction end of the long core and the reactor are all made of pressure-resistant metal pipelines. Plugs are installed at the remaining pressure measuring and sampling points of the reactor. When checking the connectivity of the long core, observe whether there are continuous bubbles emerging from the PVC pipe. When checking the airtightness, after adding water and pressurizing, observe whether there are bubbles emerging at the connection between the long core and the pressure-resistant metal pipeline, and monitor the pressure stability to ensure the airtightness of the long core installation in the reactor. At the same time, the airtightness check is performed directly inside the reactor, reducing the steps of core transfer and lowering the risk of air ingress.

[0078] Furthermore, S3 includes the following steps:

[0079] S3.1. Vacuum the long core through the pressure measurement point of the reactor until the vacuum pressure is -0.09MPa to -0.1MPa, then stop evacuating.

[0080] S3.2. After the pressure stabilizes, maintain the pressure for 60-120 minutes;

[0081] S3.3. Saturate the long core sample with water through the sampling point of the reactor.

[0082] It should be noted that a vacuum pump is connected to the pressure measuring point of the reactor. After the pump is turned on, the pressure inside the long core gradually decreases. A vacuum pressure gauge is set at the pressure measuring point in the middle of the long core. The reading of the vacuum pressure gauge needs to be continuously monitored during the experiment to avoid pressure fluctuations. High vacuum and sufficient pressure holding time can completely remove air from the core pores, which is conducive to the subsequent full saturation of formation water and avoids abnormal pressure data and permeability calculation deviations caused by residual air in the pores.

[0083] A saturated water device is connected to the sampling point of the reactor to achieve connectivity with the mid-section sampling point of the long core sample. After saturation, the core sample condition more closely approximates the initial water-bearing state of the underground reservoir, providing realistic basic conditions for subsequent transport and migration experiments. The saturated water device is existing technology and will not be further described here.

[0084] Furthermore, S4 includes the following steps:

[0085] S4.1. Connect pressure sensors to the pressure measurement point and sampling point of the reactor connected to the long core pressure measurement point, injection end and sampling point, close the remaining pressure measurement point and sampling point of the reactor, open the vent end of the temperature and pressure resistant reactor, and inject water through the bottom drain to discharge the air in the temperature and pressure resistant reactor.

[0086] S4.2. Close the drain end and the outlet, increase the confining pressure, and observe the pressure stability of the confining pressure, the pressure measuring point of the long core, and the injection end of the long core.

[0087] S4.3. Heat and continue to observe the pressure stability in S4.2 to achieve a secondary airtightness check of the temperature and pressure resistant reactor and long core.

[0088] Furthermore, in S4.2, the confining pressure is increased to 3MPa-5MPa, and in S4.3, the heating temperature is 60℃-80℃.

[0089] It should be noted that water should be injected through the bottom drain until a uniform flow of water exits the empty end, ensuring complete removal of air from the reactor. After increasing the confining pressure, the pressure fluctuation should be ≤0.1MPa, and the pressure at the long core pressure measurement point and the injection end should be stable without attenuation. The temperature should be raised to 60℃-80℃ to simulate formation temperature and held at that temperature for 2-4 hours. If the pressure fluctuation is ≤0.2MPa, the sealing performance is good. The secondary inspection, combined with the increase in temperature and confining pressure, more closely approximates actual reservoir conditions, testing the stability of the experimental setup under high temperature and high pressure environments, eliminating interference from the coupling effect of temperature and pressure, and providing a reliable environmental guarantee for subsequent polymer gel migration testing.

[0090] Furthermore, S5 includes the following steps:

[0091] S5.1. Set the injection pump displacement rate to 0.1 mL / min-0.5 mL / min and inject simulated formation water from the target reservoir into the long core.

[0092] S5.2. Record the pressure at the injection end and pressure measurement point of the long core at intervals, as well as the liquid output at the production end of the long core, and calculate the water permeability of the long core based on Darcy's formula.

[0093] Furthermore, the displacement flow rate in S5.1 is 0.1 mL / min to 0.5 mL / min.

[0094] It should be noted that the recording interval is every 10-30 minutes. Darcy's formula is an existing formula for calculating core permeability, and will not be further explained here.

[0095] Furthermore, S7 includes the following steps:

[0096] S7.1. Displace the long core by injecting pre-sheared cross-linked polymer at a constant rate of 0.1 mL / min-0.5 mL / min, and record the pressure at the injection end, pressure measurement point and sampling point of the long core at intervals, as well as the liquid output at the extraction end;

[0097] S7.2. Intermittently test the viscosity and concentration of the sampled fluid at the sampling point and the sampled fluid at the sampling end, and continuously inject the pre-sheared cross-linked polymer body until the target PV number is reached, and then switch to subsequent water flooding;

[0098] S7.3. Set the subsequent water drive displacement rate to 0.1 mL / min-0.5 mL / min, and record the pressure at the injection end, pressure measurement point and sampling point of the long core at intervals, as well as the liquid output at the production end;

[0099] S7.4. Intermittently test the viscosity and concentration of the produced fluid at the production end. When the viscosity of the produced fluid at the production end is stable and the viscosity difference with water is 0.1 mP·s-0.5 mP·s, the experiment is terminated, and the pressure data along the long core and the viscosity and concentration data of the produced fluid are obtained.

[0100] S7.5. Evaluate the transport and migration capabilities of crosslinked polymers based on the obtained data.

[0101] Furthermore, the constant rate in S7.1 is 0.1 mL / min-0.5 mL / min, and the subsequent water displacement rate in S7.3 is 0.1 mL / min-0.5 mL / min.

[0102] It should be noted that records were taken every 10-30 minutes. Viscosity was measured using a viscometer, and concentration was determined using a UV spectrophotometer.

[0103] By comprehensively comparing the pressure changes at various pressure measurement points during the cross-linked polymer injection stage and the subsequent water drive stage, as well as the viscosity and concentration changes of the cross-linked polymer along the long core, we can understand the approximate distribution and gelation of the system along the long core. Areas with increased pressure indicate that the system undergoes a cross-linking reaction to form a gel in these areas. Areas with concentrated pressure differential changes are the main gel retention areas; the viscosity and concentration of the produced fluid decrease after these areas. If the pressure differential changes are mainly concentrated in the rear of the core, it indicates a strong transport capacity of the system. Under linear flow conditions, the cross-linked polymer can achieve retention and drag enhancement in the deep core, which is beneficial for expanding the swept volume at depth. If the pressure differential changes are mainly concentrated in the front of the core, it indicates a poor transport capacity of the system within the core, making it difficult to expand the swept volume at depth in actual mining applications.

[0104] To better illustrate the present invention, this invention also provides an apparatus for testing the transport and migration capabilities of cross-linked polymers used in oilfield profile control, comprising a temperature- and pressure-resistant reactor 100. The temperature- and pressure-resistant reactor 100 is provided with a plurality of reactor pressure measuring points 110 and a plurality of reactor sampling points 120. Any reactor sampling point 120 can be used as the production end and connected to a measuring cylinder 150 via a pressure-resistant metal pipeline, and any reactor pressure measuring point 110 can be used as the injection end and connected to a core holder 300 via a pressure-resistant metal pipeline. Optional other pressure measuring points and sampling points can be connected separately via pressure-resistant metal pipelines. At the long core pressure measurement point 630 and the long core sampling point 640, the temperature and pressure resistant reactor 100 is equipped with an empty end 103 at the top and a drain outlet 104 at the bottom. The side wall of the reactor body is equipped with a pressure port 140. The pressure port 140 and the core holder 300 are each connected to a confining pressure pump 200, and a confining pressure gauge 210 is installed at each confining pressure pump 200. The end of the core holder 300 away from the temperature and pressure resistant reactor 100 is connected to a metal mixer 400, and the end of the metal mixer 400 away from the core holder 300 is connected to two sets of feeding mechanisms.

[0105] Furthermore, the feeding mechanism includes a first intermediate container 510, a second intermediate container 520, and a horizontal pump 530. The bottoms of the first intermediate container 510 and the second intermediate container 520 are each connected to the horizontal pump 530 via a pressure-resistant metal pipeline. The horizontal pump 530 is connected to a container 540, which is filled with white oil. The tops of the first intermediate container 510 and the second intermediate container 520 are each connected to a metal mixer 400 via a pressure-resistant metal pipeline.

[0106] It should be noted that, in the two sets of feeding mechanisms, the first intermediate container 510 of one set of feeding mechanisms is filled with polymer, the first intermediate container 510 of the other set of feeding mechanisms is filled with crosslinking agent, and the second intermediate container 520 of both sets of feeding mechanisms is filled with simulated formation water of the target reservoir.

[0107] Please refer to Figure 3 The temperature and pressure resistant reactor 100 includes a reactor body 102 and a top cover 101. The top cover 101 has a vent end 103. The bottom of the reactor body 102 has a drain outlet 104. The reactor body 102 is equipped with a core support 130 for placing long cores. The core support 130 is circumferentially equipped with heating tubes 131. The side wall of the reactor body 102 has a pressure port 140. The top side wall of the reactor body 102 is also circumferentially equipped with several pressure measuring points and several sampling points.

[0108] Please refer to Figure 4The long core is 8m long and is formed by combining two 4m homogeneous long cores. The two 4m homogeneous long cores are connected by a connection point 650. One homogeneous long core has an injection end 610 and the other homogeneous long core has a extraction end 620. There are also 6 long core sampling points 640 and 6 long core pressure measuring points 630 set at intervals between the injection end 610 and the extraction end 620.

[0109] To verify the technical effect of the present invention, specific experiments are described below in conjunction with the above-described method and apparatus, including the following steps:

[0110] S1. Install plugs at pressure measuring point 110 and sampling point 120 of the reactor, connect an external confining pressure pump 200, pressurize to 1MPa, observe that there is no water leakage at the welded joints of pressure measuring point 110 and sampling point 120 of the reactor, and the sealing is good. Perform a sealing check on all pressure measuring points one by one, mark the leak points, and select the points with good sealing as the pressure measuring point 110 and sampling point 120 of the reactor for the experiment.

[0111] S2. Six long core pressure measurement points 630 and six long core sampling points 640 are set at intervals along the 8m long core. Pressure-resistant metal pipelines are installed on the long core pressure measurement points 630 and the six long core sampling points 640. The long core is placed in a temperature- and pressure-resistant reactor 100. The other end of the pressure-resistant metal pipeline is connected to the pressure measurement point 110 and the sampling point 120 of the reactor. The temperature- and pressure-resistant reactor 100 is kept open and filled with water. The long core injection end 610 is connected to an air pump, and the extraction end 620 is connected to one end of a PVC pipe. The other end of the hose is inserted into the water in the temperature- and pressure-resistant reactor 100. Plugs are installed at the six pressure measurement points and the six sampling points. The long core is pressurized to 2MPa to check the connectivity and airtightness. Continuous bubbles emerge from the PVC pipe, indicating that the internal connectivity of the core is good. The valve at the extraction end 620 is closed. No bubbles emerge at the connection between the long core and the pressure-resistant metal pipeline, indicating that the connection is airtight.

[0112] S3. Connect the vacuum pump in series to the long core injection end 610 through the pressure measuring point 110 of the reactor, and connect the vacuum pressure gauge in series to the long core pressure measuring point 630 in the middle of the long core through the pressure measuring point 110 of the reactor to test the vacuum degree inside the long core. Turn on the vacuum pump, and when the vacuum gauge reading stabilizes at -0.092MPa, turn off the vacuum pump and maintain the pressure for 60 minutes. Connect the long core sampling point 640 to the saturated water device to saturate the long core with water. The water saturated in the long core is the target reservoir simulated formation water.

[0113] S4. Connect pressure sensors to the pressure measuring point and sampling point of the reactor connected to the injection end, sampling point and pressure measuring point of the long core. Close the temperature and pressure resistant reactor 100, open the top vent 103, and inject water through the bottom drain 104 to discharge the air inside the temperature and pressure resistant reactor 100. After the vent 103 discharges water evenly, close the vent 103 and drain 104, and raise the confining pressure to 3MPa. The confining pressure, the pressure at the injection end 610 and the pressure at the long core measuring point 630 remain stable, indicating that the temperature and pressure resistant reactor 100 has good sealing performance at all points under normal temperature conditions. When heated to 75℃, the confining pressure, the pressure at the injection end 610 and the pressure at the long core measuring point 630 still remain stable, and water permeability can be measured.

[0114] S5. Connect the injection end 610 to the horizontal flow pump, turn on the horizontal flow pump and set the displacement flow rate to 0.3 mL / min, inject the target reservoir simulated formation water into the long core, and record the pressure at the injection end 610, the pressure at the long core pressure measuring point 630 and the output volume at the production end 620 as 9 mL every 30 min. After the water drive pressure stabilizes, calculate the permeability of the long core as 3000 mD.

[0115] S6. Set the displacement flow rate of the horizontal flow pump to 0.3 mL / min, and inject the polymer and crosslinking agent into a metal mixer 400 with dimensions of 175×70×30 mm to mix and obtain a crosslinked polymer. The metal mixer 400 is connected to the injection end 610 through a core holder 300. The core holder 300 is equipped with a core with dimensions of φ2.5×10 cm and a permeability of 3000×10⁻⁶. -3 μm 2 A high-permeability homogeneous artificial cylindrical core is used to achieve pre-shearing of the cross-linked polymer. The core holder 300 is externally covered with an electric heating element, and the heating temperature is set to 75℃.

[0116] S7. Crosslinking polymer was injected into the long core at a constant rate of 0.3 mL / min. Pressure values ​​at the injection end (610), core pressure measurement point (630), and core sampling point (640) were recorded every 30 min. When the injected crosslinking polymer volume reached 2 PV, samples were sequentially taken at core sampling point 640 and extraction end (620). The viscosity and concentration of the extracted fluid were then tested. When the injected crosslinking polymer volume reached 2 PV, the pressure at injection end (610) was 5.727 MPa, and the pressure values ​​at core pressure measurement point (630) were 2.867 MPa, 1.495 MPa, 1.005 MPa, and 0.78 MPa, respectively. The pressures at sampling points 640, 6 MPa, 0.470 MPa, and 0.068 MPa, were 4.385 MPa, 1.706 MPa, 1.34 MPa, 0.957 MPa, 0.649 MPa, and 0.322 MPa, respectively. The fluid output at sampling point 620 was 8.7 mL. The viscosities of the extracted fluid at sampling point 640 were 62.8 mPa·s, 32.5 mPa·s, 32 mPa·s, 26 mPa·s, 6.6 mPa·s, and 2.5 mPa·s, respectively. The viscosity of the extracted fluid at sampling point 620 was 1.8 mPa·s. The concentrations were 5064.62 mg / L, 4678.21 mg / L, 4280.88 mg / L, 4278.46 mg / L, 4274.22 mg / L, and 4189.68 mg / L, respectively. The concentration of the produced fluid at the 620-cell inlet was 4175.35 mg / L. Crosslinked polymer was continuously injected until the injection volume reached 2 PV, after which water flooding was switched to a waterflooding system. The displacement rate was set at 0.3 mL / min. The injection pressure, pressure at the long core pressure measurement point, and the produced fluid volume at the production end were recorded every 30 minutes. The viscosity of the produced fluid at the production end was also measured. The concentration at the injection end of the long core at 610-cell inlet was measured when the water flooding reached 4.3 PV. The pressure was 2.093 MPa. The pressures at long core sampling point 630 were 1.475 MPa, 0.758 MPa, 0.527 MPa, 0.337 MPa, 0.230 MPa, and 0.102 MPa, respectively. The pressures at long core sampling point 640 were 1.913 MPa, 0.947 MPa, 0.62 MPa, 0.398 MPa, 0.275 MPa, and 0.158 MPa, respectively. The fluid output at sampling point 620 was 9 mL. The viscosity of the extracted fluid at sampling point 620 was basically stable at around 0.72 mP·s, which is similar to that of water. The experiment was then terminated.

[0117] The calculated pressure differences between sampling and pressure measurement points along the long core when the cross-linked polymer injection volume reached 2 PV were 1.518 MPa, 1.161 MPa, 0.211 MPa, 0.155 MPa, 0.335 MPa, 0.208 MPa, 0.171 MPa, 0.137 MPa, 0.179 MPa, 0.148 MPa, and 0.254 MPa, respectively. The pressure difference was mainly concentrated in the first half of the long core, where the viscosity and concentration of the sample decreased rapidly. This indicates that the system was mainly adsorbed and retained in the first half of the long core, and a cross-linking reaction occurred to form a gel, thereby increasing the seepage resistance. The pressure difference between some points in the second half increased, indicating that some of the cross-linked polymer could migrate to the second half of the long core and achieve retention and increased resistance. Therefore, the system has a certain deep profile control capability.

[0118] By comprehensively comparing the pressure differences at various pressure measurement points during the cross-linked polymer injection stage and the subsequent water drive stage, as well as the changes in viscosity and concentration of the cross-linked polymer along the long core, we can understand the approximate distribution of the gel along the long core. The areas where the pressure difference changes are concentrated are the main gel retention areas. After these areas, the viscosity and concentration of the produced fluid decrease accordingly. If the pressure difference changes are mainly concentrated in the rear of the core, it indicates that the system has a strong transport capacity. Under linear flow conditions, the cross-linked polymer system can achieve retention and resistance enhancement in the deep core, and its strong transport capacity is conducive to expanding the swept volume in the deep core. If the pressure difference changes are mainly concentrated in the first half of the core, and there is no significant pressure increase in the second half, the cross-linked polymer system has a poor transport capacity inside the core and is difficult to play a role in expanding the swept volume in the deep core in actual mining applications.

[0119] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for testing the transport and migration capabilities of cross-linked polymers used in oilfield profile control, wherein the entire experiment is conducted in a temperature- and pressure-resistant reactor, characterized in that... Includes the following steps: S1. Perform a leak test on the temperature and pressure resistant reactor; S2. Place the long core into the temperature- and pressure-resistant reactor and pressurize it to check the continuity and airtightness of the long core; S3. Vacuum the long core sample and perform a saturated water operation; S4. Perform a second airtightness check on the temperature- and pressure-resistant reactor and the long core sample; S5. Inject simulated formation water from the target reservoir into the long core using an injection pump, and calculate the water permeability of the long core. S6. The polymer and crosslinking agent are mixed online using a metal mixer to obtain a crosslinked polymer, which is then injected into a high-permeability cylindrical core to achieve pre-shearing; S7. The pre-sheared cross-linked polymer is directly injected into the long core. After the injection volume reaches the target PV number, it is switched to subsequent water flooding to obtain the pressure data along the long core and the viscosity and concentration data of the produced fluid. The transport and migration capacity of the cross-linked polymer is evaluated based on the pressure data along the long core and the viscosity and concentration data of the produced fluid.

2. The method according to claim 1, characterized in that, S1 includes the following steps: S1.

1. Install plugs inside the pressure measuring point and sampling point of the reactor, and connect them to the external confining pressure pump; S1.

2. Add water to the temperature and pressure resistant reactor and pressurize it to 1MPa-3MPa, and perform a tightness check at each point.

3. The method according to claim 2, characterized in that, S2 includes the following steps: S2.

1. The long core is placed into the temperature- and pressure-resistant reactor. The injection end and pressure measuring point of the long core are connected to the pressure measuring point of the reactor through a pressure-resistant metal pipeline. The sampling point and extraction end of the long core are connected to the sampling point of the reactor through a pressure-resistant metal pipeline. S2.

2. Add water to the temperature and pressure resistant reactor, connect the air pump to the injection end of the long core through the pressure measuring point of the reactor, connect a PVC pipe to the extraction end of the long core, and extend the other end of the PVC pipe into the water. Close all other pressure measuring points and sampling points of the long core, pressurize to 1MPa-2MPa, and inject air into the long core to check its connectivity. S2.

3. Close the extraction end of the long core and perform a sealing check on the long core.

4. The method according to claim 3, characterized in that, S3 includes the following steps: S3.

1. Vacuum the long core through the pressure measuring point of the reactor until the vacuum pressure is -0.09MPa to -0.1MPa and then stop evacuating; S3.

2. After the pressure stabilizes, maintain the pressure for 60-120 minutes; S3.

3. The long core sample is subjected to saturated water operation through the sampling point of the reactor.

5. The method according to claim 2, characterized in that, S4 includes the following steps: S4.

1. Connect pressure sensors to the pressure measuring point and the sampling point of the reactor connected to the long core pressure measuring point, the injection end and the sampling point, close the remaining pressure measuring points and the sampling points of the reactor, open the venting end of the temperature and pressure resistant reactor, and inject water through the bottom drain to discharge the air inside the temperature and pressure resistant reactor; S4.

2. Close the drain end and the outlet, increase the confining pressure, and observe the pressure stability of the confining pressure, the pressure measuring point of the long core, and the injection end of the long core. S4.

3. Heat and continue to observe the pressure stability in S4.2 to achieve a secondary airtightness check of the temperature and pressure resistant reactor and the long core.

6. The method according to claim 5, characterized in that, In step S4.2, the confining pressure is increased to 3MPa-5MPa, and in step S4.3, the heating temperature is 60℃-80℃.

7. The method according to claim 2, characterized in that, S5 includes the following steps: S5.

1. Set the displacement flow rate of the injection pump to 0.1 mL / min-0.5 mL / min, and inject simulated formation water from the target reservoir into the long core. S5.

2. Record the pressure at the injection end and pressure measurement point of the long core at intervals, as well as the liquid output at the production end of the long core, and calculate the water permeability of the long core based on Darcy's formula.

8. The method according to claim 2, characterized in that, S7 includes the following steps: S7.

1. The pre-sheared cross-linked polymer is injected into the long core at a constant rate of 0.1 mL / min-0.5 mL / min for displacement. The pressure at the injection end, pressure measurement point and sampling point of the long core, as well as the liquid output at the extraction end, are recorded at intervals. S7.

2. Intermittently test the viscosity and concentration of the sampled fluid at the sampling point and the sampled fluid at the sampling end, and continuously inject the pre-sheared cross-linked polymer body until the target PV number is reached, then switch to subsequent water flooding; S7.

3. Set the subsequent water drive displacement rate to 0.1 mL / min-0.5 mL / min, and record the pressure at the injection end, pressure measurement point and sampling point of the long core at intervals, as well as the liquid output at the production end; S7.

4. Intermittently test the viscosity and concentration of the produced fluid at the production end. When the viscosity of the produced fluid at the production end is stable and the viscosity difference with water is 0.1 mP·s-0.5 mP·s, the experiment is terminated, and the pressure data along the long core and the viscosity and concentration data of the produced fluid are obtained. S7.

5. Evaluate the transport and migration capabilities of crosslinked polymers based on the obtained data.

9. An apparatus for testing the transport and migration capabilities of cross-linked polymers used in oilfield profile control, characterized in that, The reactor includes a temperature- and pressure-resistant reactor, which is equipped with several pressure measuring points and several sampling points. The pressure measuring points are connected to core holders via pressure-resistant metal pipelines. A pressure port is provided on the side wall of the reactor. Each pressure port and the core holder is connected to a confining pressure pump, and the confining pressure pump is equipped with a confining pressure gauge. The end of the core holder away from the temperature- and pressure-resistant reactor is connected to a metal mixer, and the metal mixer is connected to two sets of feeding mechanisms.

10. The apparatus according to claim 9, characterized in that, The feeding mechanism includes a first intermediate container, a second intermediate container, and a horizontal flow pump. The bottoms of the first intermediate container and the second intermediate container are connected to the horizontal flow pump. The horizontal flow pump is also connected to a container filled with white oil. The tops of the first intermediate container and the second intermediate container are connected to the metal mixer.

Images