A method and system for evaluating the viscosity reduction effect of a porous medium on heavy oil

Abstract

The application discloses a method and system for evaluating the viscosity reduction effect of a porous medium on thick oil, comprising the following steps: preparing a binary system of thick oil to be tested and water, and obtaining the nuclear magnetic resonance characteristics of the binary system; preparing a plurality of viscosity reducers to be tested; preparing a porous medium sample for testing, and forming a ternary system of the porous medium sample and the binary system, and obtaining the nuclear magnetic resonance characteristics of the ternary system; injecting the plurality of viscosity reducers to be tested into the ternary system respectively, forming a corresponding quaternary system for each viscosity reducer, and obtaining the nuclear magnetic resonance characteristics of each quaternary system; and analyzing the viscosity reduction effect of the thick oil to be tested injected with different viscosity reducers according to the nuclear magnetic resonance characteristics of each quaternary system, the nuclear magnetic resonance characteristics of the ternary system and the nuclear magnetic resonance characteristics of the binary system.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field exploration and development technology, and in particular to a method and system for evaluating the viscosity-reducing effect of porous media on heavy oil. Background Technology

[0002] With the increasing demand for oil and gas resources, heavy oil resources have become increasingly important. my country possesses abundant heavy oil resources and significant production potential. The high viscosity, poor fluidity, and viscosity reduction characteristics of heavy oil are crucial for its extraction, and adding surfactants is one of the main methods for reducing its viscosity.

[0003] The evaluation method for viscosity reduction of heavy oil involves uniformly mixing heavy oil with a viscosity reducer to prepare a crude oil emulsion. The viscosity of the emulsion is then measured using a rotational viscometer or rheometer and compared to the viscosity of the heavy oil to evaluate the viscosity reduction effect. However, this technique cannot evaluate the viscosity reduction effect of heavy oil in porous media, and therefore cannot reflect the influence of porous media on the viscosity reduction effect. Summary of the Invention

[0004] The purpose of this invention is to provide a scheme for evaluating the viscosity reduction effect of heavy oil in porous media using nuclear magnetic resonance technology.

[0005] To address the aforementioned technical problems, this invention provides a method for evaluating the viscosity-reducing effect of porous media on heavy oil, comprising: preparing a binary system of the heavy oil to be tested and water, and obtaining the nuclear magnetic resonance (NMR) characteristics of the binary system; preparing multiple viscosity-reducing agents to be tested; preparing a porous media sample for testing, and forming a ternary system of the porous media sample and the binary system, and obtaining the NMR characteristics of the ternary system; injecting the multiple viscosity-reducing agents to be tested into the ternary system respectively, forming a corresponding quaternary system for each viscosity-reducing agent, and obtaining the NMR characteristics of each quaternary system; and analyzing the viscosity-reducing effect of injecting different viscosity-reducing agents into the heavy oil to be tested based on the NMR characteristics of each quaternary system, the ternary system, and the binary system.

[0006] Preferably, the nuclear magnetic resonance feature is a nuclear magnetic resonance T2 spectrum.

[0007] Preferably, the step of analyzing the viscosity-reducing effect of injecting different viscosity reducers into the experimental heavy oil based on the NMR characteristics of each quaternary system, ternary system, and binary system includes: for each viscosity reducer, comparing the relaxation time of the NMR characteristics of different component systems to determine the heavy oil whose viscosity is reduced after injecting the corresponding viscosity reducer; and evaluating the viscosity-reducing performance of each viscosity reducer based on the viscosity-reduced heavy oil corresponding to each viscosity reducer and the total oil volume.

[0008] Preferably, based on the NMR characteristics of each quaternary system and the NMR characteristics of the ternary system, a first area is calculated, which is jointly enclosed by the portion of the extended relaxation time in the NMR characteristic curve of each quaternary system and the NMR characteristics of the ternary system and the NMR characteristics of the binary system; based on the first area corresponding to each viscosity reducer, and in combination with the curve area indicated in the NMR characteristics of the ternary system, a corresponding heavy oil viscosity reduction index is obtained for each viscosity reducer.

[0009] Preferably, a certain number of quartz sands are selected as the porous media sample.

[0010] Preferably, the concentration of each viscosity reducer to be tested is the same.

[0011] Preferably, the preparation of the binary system includes: mixing the heavy oil to be tested and heavy water in a preset oil-water ratio in a rotating container and stirring thoroughly to form the binary system.

[0012] Preferably, the heavy oil to be tested has various structures; the porous medium sample used in the experiment has various structures.

[0013] On the other hand, embodiments of the present invention also provide a system for evaluating the viscosity-reducing effect of porous media heavy oil. The system is used to implement the method described above. The system includes: a nuclear magnetic resonance (NMR) device for performing NMR testing on samples of the test system to obtain the NMR characteristics of the corresponding samples; and a feature processing device connected to the NMR device for obtaining the NMR characteristics of a binary system prepared from the experimental heavy oil and water, obtaining the NMR characteristics of a ternary system prepared from the porous media sample and the binary system water, and obtaining the NMR characteristics of a quaternary system formed by injecting each type of viscosity reducer into the ternary system. Based on the NMR characteristics of each quaternary system, the ternary system, and the binary system, the viscosity-reducing effect of injecting different viscosity reducers into the experimental heavy oil is analyzed.

[0014] Preferably, the nuclear magnetic resonance device uses a CPMG pulse sequence for testing, wherein the test parameters include, but are not limited to: a main frequency of 10.11MHz, a 90-degree pulse of 23µs, a sampling interval of 2µs, a number of echoes of 6144, a number of scans of 16, a waiting time of 2s, and an echo time of 120µs.

[0015] Compared with the prior art, one or more embodiments of the above solutions may have the following advantages or beneficial effects: This invention proposes a method and system for evaluating the viscosity-reducing effect of heavy oil in porous media. The method and system utilize an online high-temperature and high-pressure nuclear magnetic resonance (NMR) device to test binary systems containing the tested heavy oil and water, ternary systems containing the tested heavy oil, water, and porous media, and quaternary systems containing the tested heavy oil, water, porous media, and various tested surfactants. The results of the multi-component system tests are combined to analyze and evaluate the viscosity-reducing effect of injecting different viscosity-reducing agents into the porous media. This invention provides a method for evaluating the viscosity-reducing changes of heavy oil in porous media using an online high-temperature and high-pressure nuclear magnetic resonance device, and can test, analyze, and evaluate the viscosity-reducing effect of injecting different viscosity-reducing agents into different heavy oils.

[0016] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a step diagram of a method for evaluating the viscosity-reducing effect of porous media on heavy oil, according to an embodiment of this application.

[0018] Figure 2 This is a schematic diagram of the nuclear magnetic resonance characteristics of different component system samples of a first viscosity reducer for evaluating the viscosity-reducing effect of porous media heavy oil according to an embodiment of this application.

[0019] Figure 3 This is a schematic diagram of the nuclear magnetic resonance characteristics of samples of different component systems of a second viscosity reducer for evaluating the viscosity-reducing effect of porous media heavy oil according to an embodiment of this application.

[0020] Figure 4 This is a schematic diagram of the system for evaluating the viscosity-reducing effect of porous media on heavy oil, according to an embodiment of this application. Detailed Implementation

[0021] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples, so that the process of how the present invention uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that, as long as there is no conflict, the various embodiments and features in the various embodiments of the present invention can be combined with each other, and the resulting technical solutions are all within the protection scope of the present invention.

[0022] Furthermore, the steps illustrated in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Also, although a logical order is shown in the flowcharts, in some cases the steps shown or described may be performed in a different order than that shown here.

[0023] With the increasing demand for oil and gas resources, heavy oil resources have become increasingly important. my country possesses abundant heavy oil resources and significant production potential. The high viscosity, poor fluidity, and viscosity reduction characteristics of heavy oil are crucial for its extraction, and adding surfactants is one of the main methods for reducing its viscosity.

[0024] The evaluation method for viscosity reduction of heavy oil involves uniformly mixing heavy oil with a viscosity reducer to prepare a crude oil emulsion. The viscosity of the emulsion is then measured using a rotational viscometer or rheometer and compared to the viscosity of the heavy oil to evaluate the viscosity reduction effect. However, this technique cannot evaluate the viscosity reduction effect of heavy oil in porous media, and therefore cannot reflect the influence of porous media on the viscosity reduction effect.

[0025] Therefore, to address one or more of the aforementioned technical problems, this application proposes a method and system for evaluating the viscosity-reducing effect of porous media on heavy oil. This method and system utilize a high-temperature, high-pressure online nuclear magnetic resonance (NMR) displacement device to obtain the NMR characteristics of a quaternary system formed by the experimental porous media, the experimental heavy oil, water, and the experimental surfactant. This allows for a comprehensive evaluation of the viscosity-reducing effect of injecting different viscosity-reducing agents into different experimental heavy oils.

[0026] Figure 1 This is a step diagram illustrating a method for evaluating the viscosity-reducing effect of porous media on heavy oil, according to an embodiment of this application. The following is in conjunction with... Figure 1 The method for evaluating the viscosity reduction effect of porous media heavy oil (hereinafter referred to as the "viscosity reduction evaluation method") described in the embodiments of the present invention will be explained.

[0027] like Figure 1 As shown, step S110 prepares the binary system of heavy oil and water to be tested, and obtains the nuclear magnetic resonance characteristics of the current binary system.

[0028] In step S110, during the preparation of the binary system, the experimental heavy oil and heavy water are mixed according to a preset oil-water ratio and placed in a rotating container for thorough stirring to form a binary system. Specifically, experimental heavy oil and heavy water are selected, the oil and water are mixed in a certain ratio, and then placed in a rotating container for thorough stirring to form a stable oil-water mixture solution, i.e., a binary system formed by the experimental heavy oil and water.

[0029] Subsequently, after the binary system is prepared, a nuclear magnetic resonance (NMR) device is used to conduct high-temperature, high-pressure online displacement tests on the binary system to obtain the corresponding NMR characteristics of the binary system. Specifically, the NMR characteristic described in this embodiment is the NMR T2 spectrum. The prepared binary system is then placed in an NMR device for testing to obtain the NMR T2 spectrum curve of the binary system.

[0030] After obtaining the NMR characteristics of the binary system, the process proceeds to step S120 to prepare the surfactant to be tested.

[0031] Step S120 involves preparing various viscosity-reducing agents for experimentation. Each viscosity-reducing agent is prepared at the same concentration. Different types of viscosity-reducing agents have different components and / or parts.

[0032] After the preparation of the viscosity reducer to be tested is completed, proceed to step S130.

[0033] Step S130 prepares a porous medium sample for the experiment and forms a ternary system of the porous medium sample and the binary system, thereby obtaining the nuclear magnetic resonance characteristics of the current ternary system.

[0034] In step S130, the porous media sample required for the current evaluation experiment is first prepared. In this embodiment of the invention, a certain amount of quartz sand can be selected as the porous media sample. Specifically, the oil-water mixture (binary system) formed in step S110 is mixed with the quartz sand as the porous media sample to prepare a ternary system consisting of the heavy oil to be tested, water, and the porous media sample.

[0035] Then, the currently prepared ternary system is divided into multiple samples. Specifically, the currently prepared ternary system is placed into multiple sample tubes, wherein the number of sample tubes corresponds to the number of types of viscosity reducers to be tested in the current evaluation experiment.

[0036] Next, using a nuclear magnetic resonance (NMR) apparatus, high-temperature, high-pressure online displacement tests were conducted on each ternary system sample to obtain the corresponding (ternary system) NMR characteristics. Sample tubes containing different ternary system samples were individually sealed in non-metallic core holders, which were then placed into the NMR probe of the NMR apparatus for testing. Under the same experimental conditions, the NMR characteristics of the ternary system samples in each sample tube were tested using the NMR apparatus to obtain the corresponding NMR T2 spectra.

[0037] Further, after obtaining the NMR characteristics of the ternary system, the process proceeds to step S140.

[0038] Step S140 involves injecting various viscosity-reducing agents into ternary systems to form corresponding quaternary systems for each agent, thereby obtaining the NMR characteristics of each quaternary system. In step S140, different viscosity-reducing agents are injected into different ternary system samples to form different quaternary systems. Then, using an NMR apparatus, high-temperature, high-pressure online displacement tests are performed on each of the different ternary system samples (different quaternary systems) injected with the viscosity-reducing agents, thereby obtaining the corresponding quaternary system NMR characteristics for each quaternary system sample.

[0039] Figure 2 This is a schematic diagram of the nuclear magnetic resonance characteristics of different component system samples of a first viscosity reducer for evaluating the viscosity-reducing effect of porous media heavy oil according to an embodiment of this application. Figure 3 This is a schematic diagram illustrating the NMR characteristics of different component system samples of a second viscosity reducer for evaluating the viscosity-reducing effect of porous media on heavy oil, as described in an embodiment of this application. Specifically, when two viscosity reducers are prepared for the current evaluation experiment, viscosity reducer No. 1 is injected into the first ternary system sample tube using an injection pump. The NMR T2 spectrum of the quaternary system formed by heavy oil, water, porous media, and viscosity reducer No. 1 is then tested. Figure 2 The NMR characteristics of the multi-component system for viscosity reducer sample 1 were demonstrated. Following the same test parameters, viscosity reducer 2 was added to a second ternary system sample tube, and another quaternary system sample consisting of heavy oil, water, porous media, and viscosity reducer 2 was tested, obtaining the corresponding quaternary system NMR T2 spectra. Figure 3 The nuclear magnetic resonance characteristics of the multi-component system of viscosity reducer sample 2 were shown.

[0040] After obtaining the NMR characteristics of each quaternary system, proceed to step S150.

[0041] Step S150 analyzes the viscosity-reducing effect of injecting different viscosity reducers into the experimental heavy oil based on the NMR characteristics of each quaternary, ternary, and binary system obtained in step S140. Using the obtained binary, ternary, and quaternary NMR T2 spectra for a specific viscosity reducer, the viscosity-reducing effect of the experimental heavy oil in the porous medium is evaluated. Specifically, for each viscosity reducer, the relaxation times of the NMR characteristics of different component systems are compared to determine the heavy oil whose viscosity is reduced after injection of the current viscosity reducer. Then, based on the viscosity-reduced heavy oil corresponding to each viscosity reducer and the total oil volume, the viscosity-reducing performance of each viscosity reducer is evaluated.

[0042] Specifically, firstly, based on the NMR characteristics of each quaternary system and the ternary system, the area of ​​the first curve formed by the extended relaxation time portion of the NMR characteristic curve of each quaternary system and the corresponding ternary and binary NMR characteristics is calculated. Then, based on the area of ​​the first surface corresponding to each viscosity reducer, and combined with the area of ​​the (second) curve formed by the T2 spectrum curve indicated in the ternary system NMR characteristics and the horizontal axis, the corresponding heavy oil viscosity reduction index is obtained for each viscosity reducer.

[0043] Figure 2 The NMR T2 spectrum of a multi-component system sample injected with viscosity reducer No. 1 is shown. The horizontal axis of the T2 spectrum, indicating the relaxation time, reflects the viscosity of the heavy oil being tested. Higher viscosity corresponds to shorter relaxation time. The vertical axis of the T2 spectrum reflects the content of heavy oils with different viscosities. Therefore, the viscosity of heavy oil can be determined by comparing the relaxation times of the T2 spectra of the multi-component system. Furthermore, the viscosity-reducing effect of different injected viscosity reducers can be assessed. Figure 2 The T2 spectra of the binary, ternary, and quaternary systems show that the relaxation time of crude oil T2 spectrum remains almost unchanged, indicating that viscosity reducer No. 1 has a poor viscosity-reducing effect on the crude oil to be tested.

[0044] Figure 3 The nuclear magnetic resonance T2 spectrum of the multi-component system sample containing the injected viscosity reducer No. 2 was displayed. Figure 3 The T2 spectra of the binary, ternary, and quaternary systems show that in the quaternary system sample, due to the injection of viscosity reducer No. 2, the relaxation time on the horizontal axis of the T2 spectrum exhibits a long relaxation time spectrum (i.e., an extended relaxation time spectrum). This indicates that viscosity reducer No. 2 has a viscosity-reducing effect on the heavy oil being tested, and the oil components with lower viscosity exhibit long relaxation times in the T2 spectrum. Figure 3 The shaded area represents the portion of heavy oil that has been viscous by the injection of viscosity reducer No. 2. The percentage of the viscous oil that has been viscous by the injection is calculated using the following formula for the viscosity reduction index of heavy oil, which is 5.8% of the total oil volume.

[0045] Furthermore, the formula for calculating the viscosity reduction index of heavy oil is expressed using the following expression: Percentage of viscosity-reducing oil (%) = Area of ​​viscosity-reducing oil / Area of ​​T2 spectrum of quaternary system The viscosity-reducing index of heavy oil is characterized by the percentage of viscosity-reducing oil. The area of ​​the viscosity-reducing oil is obtained by calculating the area of ​​the first curve formed by the extended relaxation time curve in the current quaternary system NMR characteristic curve, the corresponding ternary system NMR characteristic curve, and the binary system NMR characteristic curve. The area of ​​the quaternary system T2 spectrum is obtained by calculating the area of ​​the second curve formed by the current quaternary system NMR characteristic curve and the horizontal axis.

[0046] Therefore, the viscosity reduction evaluation method described in steps S110 to S150 of this invention can test the viscosity reduction effect of different types of viscosity reducers on the current experimental heavy oil (in the porous medium used in the current experiment).

[0047] Furthermore, in this embodiment of the invention, the experimental heavy oil can be constructed in multiple forms, thereby continuously repeating the above steps S110 to S150, which allows for the analysis and evaluation of the viscosity-reducing effect of different heavy oils under the injection of different viscosity-reducing agents. Different heavy oils used in the experiment refer to oils of different viscosities. Generally, the viscosity of heavy oil varies from oilfield to oilfield. When constructing multiple heavy oils, light oil can be used to dilute the heavy oil to obtain oils of different viscosities.

[0048] Furthermore, embodiments of the present invention can also construct various types of porous media samples for experiments, thereby continuously repeating the above steps S110 to S150, which enables the analysis and evaluation of the viscosity-reducing effect of heavy oil in different porous media environments when injected with different viscosity reducers. The different types of porous media samples can be constructed according to different media types and / or numbers, etc.

[0049] Example: The viscosity reduction evaluation method described in this embodiment of the invention was applied to a heavy oil working area in an oilfield in Henan Province. The process involved is as follows: Step 1: Select heavy oil from Henan Oilfield and prepare a 1:1 oil-water mixture with a total volume of 40 ml. Place the mixture in a rotating container and stir at 5000 rpm to form a stable oil-water mixture, i.e., a binary system of heavy oil and water. Inject 10 ml of the heavy oil / water mixture into two sample tubes, and then place both sample tubes into the probe of an NMR (Nuclear Magnetic Resonance) device to obtain the NMR T2 spectrum. The nuclear magnetic resonance equipment test uses the CPMG pulse sequence, with the following parameters: main frequency 10.11MHz, 90-degree pulse 23us, sampling interval 2us, number of echoes 6144, number of scans 16, waiting time 2s, and echo time 120us.

[0050] Step 2: Select two types of surfactants, namely viscosity reducer No. 1 and viscosity reducer No. 2, and prepare them at a concentration of 0.5%.

[0051] Step 3: Select 70-mesh quartz sand as the porous medium. Put the quartz sand into two 10ml sample tubes and mix it with the heavy oil-water mixture to prepare a ternary system of heavy oil, water, and porous medium.

[0052] Step 4: The ternary system of heavy oil, water, and porous media from one sample tube is placed into a non-metallic core holder and sealed. The non-metallic core holder is then inserted into the NMR probe and connected to the tubing. The NMR T2 spectrum is measured under the same NMR measurement parameters. Viscosity reducer #1 is injected into the sample tube via an injection pump to test the T2 spectrum of the quaternary system of heavy oil, water, porous media, and viscosity reducer #1. The same steps are repeated to test the NMR T2 spectrum of another sample containing the quaternary system of heavy oil, water, porous media, and viscosity reducer #2.

[0053] Step 5: Analyze the T2 NMR spectra of the two obtained binary, ternary, and quaternary systems to evaluate the different effects of injecting different viscosity-reducing agents into porous media. (Refer to...) Figure 2 and Figure 3 .

[0054] By repeating the above steps, the viscosity-reducing effect of injecting different viscosity reducers into different heavy oils can be tested, analyzed, and evaluated.

[0055] On the other hand, based on the above-described viscosity reduction evaluation method, this embodiment of the invention also provides a system for evaluating the viscosity reduction effect of porous media heavy oil (hereinafter referred to as the "viscosity reduction evaluation system"). The viscosity reduction evaluation system is used to implement the viscosity reduction evaluation method as described above.

[0056] Figure 4 This is a schematic diagram of a system for evaluating the viscosity-reducing effect of porous media on heavy oil, according to an embodiment of this application. Figure 4 As shown, the viscosity reduction evaluation system of this embodiment includes: nuclear magnetic resonance device 401 and feature processing device 402.

[0057] Furthermore, the nuclear magnetic resonance (NMR) device 401 is used to perform NMR testing on the sample of the test system to obtain the NMR characteristics of the corresponding sample. The feature processing device 402 is connected to the NMR device. The feature processing device 402 is used to obtain the NMR characteristics of a binary system prepared from the experimental heavy oil and water, the NMR characteristics of a ternary system prepared from a porous medium sample and the binary system water, and the NMR characteristics of a quaternary system formed by injecting each type of viscosity reducer into the ternary system. Then, based on the NMR characteristics of each quaternary system, the ternary system, and the binary system, the viscosity-reducing effect of the current experimental heavy oil after injecting different viscosity reducers is analyzed.

[0058] Furthermore, the nuclear magnetic resonance device 401 uses a CPMG pulse sequence for testing. The test parameters include, but are not limited to: a main frequency of 10.11 MHz, a 90-degree pulse of 23 μs, a sampling interval of 2 μs, a number of echoes of 6144, a number of scans of 16, a waiting time of 2 s, and an echo time of 120 μs.

[0059] This invention discloses a method and system for evaluating the viscosity-reducing effect of heavy oil in porous media. The method and system utilize an online high-temperature and high-pressure nuclear magnetic resonance (NMR) device to test a binary system containing the tested heavy oil and water, a ternary system containing the tested heavy oil, water, and a porous medium, and a quaternary system containing the tested heavy oil, water, a porous medium, and various tested surfactants. The results of the multi-component system tests are combined to analyze and evaluate the viscosity-reducing effect of injecting different viscosity-reducing agents into the porous medium. Therefore, this invention provides a method for evaluating the viscosity-reducing changes of heavy oil in porous media using an online high-temperature and high-pressure nuclear magnetic resonance device, and can test, analyze, and evaluate the viscosity-reducing effect of injecting different viscosity-reducing agents into different heavy oils.

[0060] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0061] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should be extended to equivalent substitutions of these features as understood by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0062] The phrase "an embodiment" or "an embodiment" used in this specification means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Therefore, the phrase "an embodiment" or "an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0063] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and changes in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection of this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A method for evaluating the viscosity-reducing effect of porous media on heavy oil, comprising: A binary system of heavy oil and water was prepared, and the nuclear magnetic resonance T2 spectrum of the binary system was obtained. Prepare various viscosity reducers for experimental use; Prepare a porous medium sample for experimentation, and form a ternary system of the porous medium sample and the binary system, and obtain the nuclear magnetic resonance T2 spectrum of the ternary system; The various viscosity-reducing agents to be tested were injected into the ternary system respectively, forming a corresponding quaternary system for each viscosity-reducing agent, and the nuclear magnetic resonance T2 spectrum of each quaternary system was obtained; Based on the NMR T2 spectra of each quaternary system, ternary system, and binary system, the viscosity-reducing effect of injecting different viscosity-reducing agents into the experimental heavy oil was analyzed, including: For each viscosity reducer, the relaxation time of the nuclear magnetic resonance T2 spectra of different component systems was compared to determine the heavy oil that was viscosity-reduced after the injection of the corresponding viscosity reducer. Based on the viscosity-reduced heavy oil corresponding to each viscosity reducer and the total oil volume, the viscosity-reducing performance of each viscosity reducer was evaluated, including: Based on the nuclear magnetic resonance T2 spectrum of each quaternary system and the nuclear magnetic resonance T2 spectrum of the ternary system, calculate the first area enclosed by the portion of the extended relaxation time curve that appears in the nuclear magnetic resonance T2 spectrum curve of each quaternary system, the nuclear magnetic resonance T2 spectrum of the ternary system, and the nuclear magnetic resonance T2 spectrum of the binary system. Based on the first area corresponding to each viscosity reducer, and combined with the curve area indicated in the T2 NMR spectrum of the ternary system, the corresponding heavy oil viscosity reduction index is obtained for each viscosity reducer.

2. The method according to claim 1, characterized in that, A certain number of quartz sands were selected as the porous media samples.

3. The method according to claim 1, characterized in that, Each viscosity reducer tested was prepared at the same concentration.

4. The method according to claim 1, characterized in that, The preparation of the binary system includes: The heavy oil and heavy water to be tested are mixed in a preset oil-water ratio in a rotating container and stirred thoroughly to form the binary system.

5. The method according to claim 1, characterized in that, The structure of the heavy oil to be tested is varied; The porous media samples used in the experiment have various structures.

6. A system for evaluating the viscosity-reducing effect of porous media on heavy oil, characterized in that, The system is used to implement the method as described in any one of claims 1 to 5, and the system comprises: Nuclear magnetic resonance (NMR) devices are used to perform NMR tests on samples of the test system to obtain the corresponding NMR characteristics of the samples. A feature processing device, connected to the nuclear magnetic resonance (NMR) device, is used to obtain the NMR characteristics of a binary system prepared from the experimental heavy oil and water, the NMR characteristics of a ternary system prepared from a porous medium sample and the binary system water, and the NMR characteristics of a quaternary system formed by injecting each of the experimental viscosity reducers into the ternary system. Based on the NMR characteristics of each quaternary system, the ternary system, and the binary system, the viscosity-reducing effect of injecting different viscosity reducers into the experimental heavy oil is analyzed.

7. The system according to claim 6, characterized in that, The nuclear magnetic resonance device is tested using a CPMG pulse sequence, and the test parameters include: a main frequency of 10.11MHz, a 90-degree pulse of 23µs, a sampling interval of 2µs, a number of echoes of 6144, a number of scans of 16, a waiting time of 2s, and an echo time of 120µs.

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