Method for calculating recovery ratio of different fluid components based on CO2 huff and puff and 2D nuclear magnetic combined measurement

Abstract

The invention discloses a method for calculating the recovery ratio of different fluid components based on CO2 huff and puff and 2D nuclear magnetic combined measurement, and relates to the technical field of unconventional oil and gas development, and the method comprises the following steps: measuring a one-dimensional nuclear magnetic T2 spectrum and a 2D nuclear magnetic T1-T2 spectrum of an oil-saturated rock core to obtain nuclear magnetic porosity; carrying out a supercritical CO2 huff-puff 2D nuclear magnetic combined measurement experiment on the oil-saturated rock core to obtain a 2D nuclear magnetic T1-T2 spectrum; the change rate is calculated through the 2D nuclear magnetism T1-T2 spectrum; the recovery ratio is calculated by using the 2D nuclear magnetism T1-T2 spectrum semaphores of oil saturation and different throughput rounds; on the basis of the multi-temperature-order pyrolysis fluid component division plate, the oil-saturated 2D nuclear magnetic T1-T2 spectrum and the 2D nuclear magnetic T1-T2 spectrum semaphore after multiple rounds of huff and puff, the rock core volume and the nuclear magnetic porosity are combined, and the recovery rates of different fluid components are calculated respectively. According to the method, the pore utilization efficiency of different injection stages is quantified, and the fluid types are distinguished by utilizing 2D nuclear magnetism, so that the spatial distribution of different fluid components is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of unconventional oil and gas development, and particularly to a calculation method for recovery ratios of different fluid components based on CO2 huff and puff and 2D nuclear magnetic resonance joint measurement. Background Art

[0002] As an important replacement resource for China's energy structure transformation, the recovery ratio of shale oil and gas directly determines the economy and sustainability of resource development. Improving the recovery ratio is not only the key to ensuring energy security but also an important path to achieving the "dual carbon" goal.

[0003] Methods for studying the recovery ratio in the laboratory include core flooding experiments, one-dimensional nuclear magnetic resonance methods, etc. Among them, in the current stage of core flooding experiments, gas flooding is usually used. By injecting adsorbable gases such as CO2, competitive adsorption is used to displace the adsorbed gas in the shale, enhance the fluidity of crude oil, and induce microfractures to improve permeability. The recovery ratio is calculated by measuring the mass of the core before and after flooding. However, such methods only macroscopically evaluate the recovery ratio, cannot analyze the difference in crude oil production in different pore sizes, parameter optimization relies on empirical models, and is affected by the oil film on the core surface, resulting in a smaller calculated value of the recovery ratio. The one-dimensional nuclear magnetic resonance method measures the one-dimensional nuclear magnetic resonance of the core in the flooding experiment. By calculating the nuclear magnetic resonance T2 spectrum signal amount under different flooding experiment conditions, the recovery ratio in different pore size ranges can be obtained, which can provide certain microscopic information. However, in the shale formation with complex microscopic pore spaces, this method cannot identify the occurrence states of different fluids such as oil and water in the core, such as adsorbed and free oil in the core.

[0004] Therefore, there is an urgent need to study a calculation method for the recovery ratio of different fluid components. Summary of the Invention

[0005] To solve the above technical problems, the present invention discloses a calculation method for recovery ratios of different fluid components based on CO2 huff and puff and 2D nuclear magnetic resonance joint measurement. This method combines dynamic monitoring through multiple rounds of CO2 huff and puff - 2D nuclear magnetic resonance joint measurement experiments to quantify the pore utilization efficiency at different injection stages and reveal the microscopic displacement mechanism; combined with the fluid division chart, the utilization efficiency of different types of fluids in the pores is analyzed through 2D difference spectroscopy to obtain the spatial distribution of different fluid components (such as free oil, adsorbed oil), and quantitative and qualitative evaluation of the recovery ratio is realized.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A calculation method for recovery ratios of different fluid components based on CO2 huff and puff and 2D nuclear magnetic resonance joint measurement includes the following steps:

[0008] S1. Measure the one-dimensional nuclear magnetic resonance T2 spectrum and 2D nuclear magnetic resonance T1 - T2 spectrum of the oil-saturated core to obtain the nuclear magnetic resonance porosity;

[0009] S2. Conduct supercritical CO2 huff and puff - 2D NMR joint measurement experiments on the oil - saturated core to obtain the 2D NMR T1 - T2 spectrum.

[0010] S3. Calculate the change rate from the 2D NMR T1 - T2 spectrum and conduct dynamic NMR response monitoring. When the relative error of the change rate is less than 0.2%, stop the joint measurement experiment; otherwise, repeat steps S2 and S3 and recalculate the change rate until the relative error is less than 0.2%.

[0011] S4. Calculate the recovery factor using the signal amounts of the 2D NMR T1 - T2 spectra of the oil - saturated and different huff and puff cycles.

[0012] S5. Based on the pyrolysis fluid component division chart at multiple temperature levels, combined with the signal amounts of the 2D NMR T1 - T2 spectra of the oil - saturated and after multiple huff and puff cycles, the core volume, and the porosity, calculate the recovery factors of different fluid components respectively.

[0013] Optionally, in step S1, place the dried shale core in a vacuum pressurized saturation device, evacuate the core holder for 24 h, inject aviation kerosene to saturate it for 72 h under a pressure of 30 MPa, and then measure the one - dimensional NMR T2 spectrum and the 2D NMR T1 - T2 spectrum; among them, the NMR measurement parameters are: echo spacing is 0.06 ms, waiting time is 5000 ms, the number of echoes is 32. Combine the NMR porosity standard sample and calculate the NMR porosity using the one - dimensional NMR T2 spectrum of the oil - saturated core. Aviation kerosene has a high purity and weak corrosiveness to the instrument, and it is usually used in the core oil - saturation experiment.

[0014] Optionally, in step S2, use the CO2 huff and puff experimental instrument, set the injection pressure of 20 MPa and the system temperature of 70 °C, and conduct periodic huff and puff on the core. The single - experiment process includes: fluctuating pressure from 20 to 25 MPa and high - pressure pulse injection at 0.1 Hz, soaking the well for 4 h, step - down pressure reduction to atmospheric pressure with a 5 - MPa pressure reduction per stage and a 10 - min pressure stabilization until the core stops producing oil, and then standing for 2 h, which is regarded as the completion of one huff and puff experiment.

[0015] Optionally, in step S2, measure the one - dimensional NMR T2 spectrum and the 2D NMR T1 - T2 spectrum of the core after huff and puff. The NMR measurement parameters are: echo spacing is 0.06 ms, waiting time is 5000 ms, and the number of echoes is 32.

[0016] Optionally, in step S3, with the help of the 2D NMR T1 - T2 spectra of the core after oil - saturation and after each huff and puff cycle, subtract the corresponding signal change regions to obtain the 2D NMR difference spectrum between adjacent huff and puff cycles, stack the NMR signal amounts of the 2D NMR difference spectrum, and calculate the change rate. ;

[0017] ;

[0018] Wherein, is the change rate after the I-th round of huff and puff, %; is the nuclear magnetic resonance signal amount after the (I-1)-th round of huff and puff, is the nuclear magnetic resonance signal amount after the I-th round of huff and puff, is the nuclear magnetic resonance signal amount after oil saturation, and I is the number of huff and puff rounds;

[0019] Further, in combination with the multi-temperature stage pyrolysis fluid component division chart, assuming there are n kinds of fluids, by superimposing the nuclear magnetic resonance signal amounts in different fluid component regions, the change rate of each fluid is calculated, and the formula is:

[0020] ;

[0021] Wherein, is the change rate after the I-th round of huff and puff of the j-th fluid, %; is the nuclear magnetic resonance signal amount of the j-th fluid after the (I-1)-th round of huff and puff, is the nuclear magnetic resonance signal amount of the j-th fluid after the I-th round of huff and puff, is the nuclear magnetic resonance signal amount after oil saturation, I is the number of huff and puff rounds, and j is the fluid type;

[0022] When the change rate is less than 0.2%, the experiment is terminated; otherwise, repeat steps S2 and S3 to conduct multiple rounds of CO2 huff and puff experiments and 2D nuclear magnetic resonance joint measurement experiments.

[0023] Optionally, in step S4, through the CO2 huff and puff-2D joint measurement experiment, the saturated oil 2D nuclear magnetic resonance T1-T2 spectrum and the 2D nuclear magnetic resonance T1-T2 spectrum signal amounts after multiple rounds of huff and puff are obtained. Using the nuclear magnetic resonance signal amount of the unit volume porosity standard sample, the signal amount is converted into pore volume, and the recovery factor is calculated by combining the core volume and the nuclear magnetic resonance porosity , and the formula is:

[0024] ;

[0025] Wherein, is the recovery factor, %; are respectively the nuclear magnetic resonance signal change amounts after oil saturation and after multiple rounds of huff and puff, dimensionless; C is the conversion coefficient between the nuclear magnetic resonance signal amount of the standard sample and the pore volume, dimensionless; is the nuclear magnetic resonance porosity, %; V is the core volume.

[0026] Optionally, in step S5, in combination with the pyrolysis fluid component partitioning chart at multiple temperature stages, according to the type of fluid components in the target area, by calculating the nuclear magnetic resonance signal amounts in different fluid regions of the 2D nuclear magnetic resonance T1-T2 spectrum, the nuclear magnetic resonance recovery factor is subdivided into the recovery factors of different fluid components. When it is assumed that the fluid components of the shale only include free oil, adsorbed oil, and heavy oil, the formula is:

[0027] ;

[0028] In the formula, , , are the recovery factors of free oil, adsorbed oil, and heavy oil, respectively, %; , , are the changes in nuclear magnetic resonance signals before and after multiple rounds of huff and puff of free oil, adsorbed oil, and heavy oil, respectively, dimensionless.

[0029] The beneficial effect of the present invention is that the present invention proposes a calculation method for the recovery factors of different fluid components based on the combination of CO2 huff and puff and 2D nuclear magnetic resonance measurement. By combining multiple rounds of CO2 huff and puff experiments with 2D nuclear magnetic resonance dynamic monitoring, the pore utilization efficiency at different injection stages is quantified; through 2D difference spectrum analysis, the utilization efficiency of different types of crude oil in different pore sizes is quantified, making up for the defects that the traditional mass method only focuses on the macroscopic quality and is affected by the residual oil film during the core surface displacement process, resulting in a smaller calculated value of the recovery factor, and the one-dimensional nuclear magnetic resonance method can only calculate the recovery factors of oil and gas in different pore size ranges. By using the characteristic that 2D nuclear magnetic resonance can distinguish fluid types, the spatial distributions of different fluid components (such as free oil, adsorbed oil) are obtained, realizing the quantitative and qualitative evaluation of the recovery factor for all-dimensional analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a flowchart of the calculation method for the recovery factors of different fluid components based on the combination of CO2 huff and puff and 2D nuclear magnetic resonance measurement of the present invention;

[0031] Figure 2 is a saturated oil 2D nuclear magnetic resonance T1-T2 spectrum diagram shown in an embodiment of the present invention;

[0032] Figure 3 is a 2D nuclear magnetic resonance T1-T2 spectrum diagram of different huff and puff rounds shown in an embodiment of the present invention;

[0033] Figure 4 is the change rate obtained by the mass method and the nuclear magnetic resonance method shown in an embodiment of the present invention;

[0034] Figure 5 is the change rate of free oil and adsorbed oil obtained by the nuclear magnetic resonance method shown in an embodiment of the present invention;

[0035] Figure 6The recovery factor obtained by the mass method and the nuclear magnetic method shown in an embodiment of the present invention;

[0036] Figure 7 The recovery factors of free oil and adsorbed oil obtained by the nuclear magnetic method shown in an embodiment of the present invention. Detailed implementation manners

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. Therefore, the detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0038] The calculation method for the recovery factors of different fluid components based on CO2 huff and puff and 2D nuclear magnetic joint measurement in this embodiment is illustrated by the experimental data analysis and recovery factor calculation of three cores from Well FX184 in Shengli Oilfield. The process is as Figure 1 shown and includes the following steps:

[0039] S1. Cut the three cores into standard plug-like cores respectively, dry the cores in an oven at 80 °C, weigh the mass of the cores every 24 h until the mass change of the cores is less than 5%; then conduct a vacuum pumping and pressure saturation oil experiment on the cores. Use a professional pressure saturation oil instrument to pump the pressure chamber for 24 h, then inject aviation kerosene, apply a pressure of 30 MPA through a pressure pump, and keep the state of oil saturation for 72 h; wrap the oil-saturated cores with special non-nuclear magnetic signal films to prevent oil and gas from escaping, and measure the one-dimensional nuclear magnetic T1 spectrum and the 2D nuclear magnetic T1-T2 spectrum of the oil-saturated cores respectively, as Figure 2 shown; among them, the nuclear magnetic measurement parameters are: the echo spacing is 0.06 ms, the waiting time is 5000 ms. Combine the nuclear magnetic porosity standard sample, and calculate the nuclear magnetic porosity using the oil-saturated one-dimensional nuclear magnetic T2 spectrum, as shown in Table 1, and measure the oil-saturated mass.

[0040] S2. Conduct supercritical CO2 huff and puff - 2D NMR joint measurement experiments on the oil - saturated core and record the core mass. Specifically, use the CO2 huff and puff experimental instrument to set the injection pressure at 20 MPa and the system temperature at 70 °C, and conduct periodic huff and puff on the core. The parameters for a single experiment include: high - pressure pulsed injection (fluctuating pressure from 20 to 25 MPa, frequency 0.1 Hz), soaking for 4 h, step - down pressure (each step of pressure reduction is 5 MPa, stabilizing pressure for 10 min) to atmospheric pressure. After the core stops producing oil, let it stand for 2 h, which is regarded as completing one huff and puff experiment.

[0041] Measure the one - dimensional NMR T2 spectrum and 2D NMR T1 - T2 spectrum of the core after huff and puff. The NMR measurement parameters are: echo spacing of 0.06 ms, waiting time of 5000 ms, and the number of echoes of 32, and measure the mass M i , and the core mass data of different huff and puff rounds of three cores are shown in Table 1.

[0042] Table 1 Summary table of core NMR porosity and mass

[0043]

[0044] S3. Calculate the change rate and conduct dynamic NMR response monitoring. When the relative error of the change rate is less than 0.2%, stop the joint measurement experiment; otherwise, repeat steps S2 and S3 until the relative error of the change rate is less than 0.2%.

[0045] With the help of the 2D NMR T1 - T2 spectra of the oil - saturated core and the core after each round of huff and puff, as Figure 3 shown, they are the 2D NMR T1 - T2 spectra of multiple rounds of huff and puff of cores B28, B42, and B85 respectively. Subtract the corresponding signal change regions to obtain the 2D NMR difference spectrum between adjacent two rounds of huff and puff. Stack the NMR signal amounts of the 2D NMR difference spectrum and calculate the change rate , as shown in the following formula:

[0046] ;

[0047] In the formula, is the change rate after the I - th round of huff and puff, is the NMR signal amount after the (I - 1) - th round of huff and puff, is the NMR signal amount after the I - th round of huff and puff, is the NMR signal amount after oil saturation, and I is the number of huff and puff rounds.

[0048] Furthermore, combined with the multi - temperature - stage pyrolysis fluid component division chart, in Well FX184, the fluid component division chart shows that the fluid types are mainly free oil and adsorbed oil, as Figure 5As shown, when the throughput cycle is 4, the change rate changes simultaneously in two consecutive cycles and satisfies less than 0.2%. It is considered that most of the movable oil in the core has been displaced by CO2, and a total of four throughput experiments have been carried out. The formulas for calculating the change rates of free oil and adsorbed oil are as follows:

[0049] ;

[0050] ;

[0051] In the formula, 、 are the change rates of free oil and adsorbed oil after the fourth throughput; 、 are the NMR signal amounts of free oil and adsorbed oil after the third throughput; 、 are the NMR signal amounts of free oil and adsorbed oil after the fourth throughput; 、 are the NMR signal amounts of free oil and adsorbed oil after oil saturation.

[0052] S4. Calculate the recovery factor using the 2D NMR T1-T2 spectral signal amounts of oil saturation and different throughput cycles.

[0053] Through the CO2 throughput-2D joint measurement experiment, the 2D NMR T1-T2 spectral signal amounts of oil saturation and the 2D NMR T1-T2 spectrum after four throughput cycles are obtained. Using the NMR signal amount of the unit volume porosity standard sample, the signal amount is converted into pore volume, and the recovery factor is calculated in combination with the core volume and porosity , and the formula is:

[0054] ;

[0055] In the formula, is the recovery factor, %; are the NMR signal change amounts of oil saturation and after four throughput cycles respectively, dimensionless; C is the conversion coefficient of the NMR signal amount of the standard sample and the pore volume, dimensionless; is the NMR porosity, %; V is the core volume.

[0056] S5. Based on the multi-temperature-step pyrolysis fluid component division chart, combined with the 2D NMR T1-T2 spectral signal amounts of oil saturation and after four throughput cycles, core volume, and porosity, calculate the recovery factors of different fluid components respectively.

[0057] According to the petroleum and natural gas industry standards "Rock Pyrolysis Analysis Method SY / T 5117-1996" and "Rock Pyrolysis Analysis GB / T 18602-2012", the fluid component division chart of Well FX184 is obtained through multi-temperature pyrolysis experiments. The regional signals of 2D nuclear magnetic difference spectra are mainly located in the free oil and adsorbed oil signal regions. Through the following formula, the recovery calculation methods of free oil and adsorbed oil are calculated respectively, so as to realize the evaluation of the recovery of different fluid components.

[0058] ;

[0059] In the formula, , are the recoveries of free oil and adsorbed oil respectively, %; V is the core volume, cm 3 ; is the nuclear magnetic porosity, %; , are the changes in nuclear magnetic signals of free oil and adsorbed oil before and after four rounds of huff and puff respectively, dimensionless; C is the conversion coefficient of the nuclear magnetic signal amount of the standard sample to the pore volume, dimensionless.

[0060] The calculation results of the recoveries of free oil and adsorbed oil in Well FX184 are as Figure 7 shown. The recovery of free oil is 0.1% - 0.2%, while the recovery of adsorbed oil is 0.03% - 0.05%, indicating that the main pores affected by the CO2 huff and puff experiment are macropores, and the change of adsorbed pores is basically small.

[0061] In order to facilitate the comparison of the recovery calculation effect, the mass method is also used to calculate the recovery in this embodiment, and four rounds of huff and puff experiments are carried out. Using the mass M0 of the core saturated with oil before huff and puff in Table 1, the mass M3 after the third round of huff and puff, and the mass M4 after the fourth round of huff and puff, calculate the change rate , as Figure 4 shown. The calculation formula is:

[0062] ;

[0063] In the formula, is the change rate after the fourth round of huff and puff using the mass method, is the core mass after the third round of huff and puff, g; is the core mass after the fourth round of huff and puff, g; is the core mass after saturation with oil, g.

[0064] Using the changes in the mass of the saturated core and the core mass at different huff and puff rounds in Table 1, the recovery is obtained. The formula is:

[0065] ;

[0066] Wherein, is the recovery factor obtained by the mass method, %; V is the core volume, cm 3 ; is the nuclear magnetic porosity, %; is the core density, cm 3 / g; is the mass change after huff and puff, g.

[0067] The recovery factors obtained by the mass method and the method of this embodiment (abbreviated as the nuclear magnetic method) are shown in Table 2 and Figure 6 As shown, the recovery factors of the three cores obtained by the nuclear magnetic method are all greater than those obtained by the mass method, indicating that the mass method is affected by the oil film on the core surface, resulting in a lower calculated recovery factor, while the recovery factor of the nuclear magnetic method will not have a similar problem.

[0068] Table 2 Summary of recovery factor calculations by the mass method and the nuclear magnetic method

[0069]

[0070] It can be seen that the recovery factor obtained by the nuclear magnetic method is larger than that obtained by the mass method, indicating that during the huff and puff process, the oil film does have an impact on the calculated recovery factor, while the nuclear magnetic method can avoid the influence of the oil film. As shown in the table, the recovery factor calculated by the nuclear magnetic method is mainly provided by free oil, and the average proportion of the adsorbed oil recovery factor of the three cores is 24.5%, reflecting that CO2 flooding has a certain promoting effect on the production of adsorbed oil in shale.

[0071] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions, or substitutions made by those skilled in the art within the essence of the present invention should also fall within the protection scope of the present invention.

Claims

1. A calculation method for the recovery rate of different fluid components based on CO2 huff and puff and 2D nuclear magnetic resonance joint measurement, characterized in that It includes the following steps: S1. Measure the one-dimensional nuclear magnetic resonance (NMR) T2 spectrum and the two-dimensional (2D) NMR T1-T2 spectrum of the oil-saturated core to obtain the NMR porosity; S2. Conduct a supercritical CO2 huff and puff-2D NMR joint measurement experiment on the oil-saturated core to obtain the 2D NMR T1-T2 spectrum; S3. Calculate the change rate from the 2D NMR T1-T2 spectrum and conduct dynamic NMR response monitoring. When the relative error of the change rate is less than 0.2%, stop the joint measurement experiment; Otherwise, repeat steps S2 and S3, and recalculate the change rate until the relative error is less than 0.2%; S4. Calculate the recovery factor using the signal amounts of the 2D NMR T1-T2 spectra of the oil-saturated state and different huff and puff cycles; S5. Based on the multi-temperature stage pyrolysis fluid component division chart, combined with the signal amounts of the 2D NMR T1-T2 spectra of the oil-saturated state and after multiple huff and puff cycles, the core volume, and the NMR porosity, calculate the recovery factors of different fluid components respectively.

2. The calculation method for the recovery rate of different fluid components based on CO2 huff and puff and 2D nuclear magnetic resonance joint measurement according to claim 1, wherein In step S1, place the dried shale core in a vacuum pressurized saturation device, evacuate the core holder for 24 h, inject aviation kerosene to saturate it for 72 h under a pressure of 30 MPa, and then measure the one-dimensional NMR T2 spectrum and the 2D NMR T1-T2 spectrum. Among them, the NMR measurement parameters are: echo spacing of 0.06 ms, waiting time of 5000 ms, number of echoes of 32, and combined with the NMR porosity standard sample, calculate the NMR porosity using the one-dimensional NMR T2 spectrum of the oil-saturated state.

3. The calculation method for the recovery rate of different fluid components based on CO2 huff and puff and 2D nuclear magnetic resonance joint measurement according to claim 2, characterized in that, In step S2, use the CO2 huff and puff experimental instrument, set the injection pressure of 20 MPa and the system temperature of 70 °C, and conduct periodic huff and puff on the core. The single experimental process includes: fluctuating pressure from 20 to 25 MPa and high-pressure pulse injection at 0.1 Hz, soaking for 4 h, stepwise pressure reduction to atmospheric pressure with a pressure reduction of 5 MPa per stage and a pressure stabilization of 10 min until the core stops producing oil, and then standing for 2 h, which is regarded as the completion of one huff and puff experiment.

4. The calculation method for the recovery rate of different fluid components based on CO2 huff and puff and 2D nuclear magnetic resonance joint measurement according to claim 3, characterized in that, In step S2, measure the one-dimensional NMR T2 spectrum and the 2D NMR T1-T2 spectrum of the core after huff and puff. The NMR measurement parameters are: echo spacing of 0.06 ms, waiting time of 5000 ms, and number of echoes of 32.

5. The calculation method for the recovery factor of different fluid components based on CO2 huff and puff and 2D NMR joint measurement according to claim 4, characterized in that, In step S3, by means of the 2D NMR T1-T2 spectra of the core after being saturated with oil and after each round of huff and puff, the difference between the corresponding signal change regions is taken to obtain the 2D NMR difference spectrum between two adjacent huff and puff operations. The NMR signal amounts of the 2D NMR difference spectrum are superimposed, and the change rate is calculated. ; ； In the formula, is the change rate after the I-th cycle of huff and puff, %; is the nuclear magnetic signal volume after the (I - 1)-th cycle of huff and puff, is the nuclear magnetic signal volume after the I-th cycle of huff and puff, is the nuclear magnetic signal volume after oil saturation, and I is the number of huff and puff cycles; Combined with the multi-temperature pyrolysis fluid component division chart, assuming there are n kinds of fluids, the nuclear magnetic signal amounts in different fluid component regions are superimposed, and the change rate of each fluid is calculated. , the formula is: ； Wherein, is the change rate after the j-th fluid huff and puff in the I-th cycle, %; is the nuclear magnetic resonance signal amount after the j-th fluid huff and puff in the (I-1)-th cycle, is the nuclear magnetic resonance signal amount after the j-th fluid huff and puff in the I-th cycle, is the nuclear magnetic resonance signal amount after oil saturation, I is the number of huff and puff cycles, and j is the type of fluid; When the change rate is less than 0.2%, terminate the experiment; otherwise, repeat steps S2 and S3 to conduct multiple rounds of CO2 huff and puff experiments and 2D NMR joint measurement experiments.

6. The calculation method for the recovery rate of different fluid components based on CO2 huff and puff and 2D nuclear magnetic resonance joint measurement according to claim 5, wherein In step S4, through the CO2 huff and puff-2D joint measurement experiment, the saturated oil 2D NMR T1-T2 spectrum and the signal volume of the 2D NMR T1-T2 spectrum after multiple rounds of huff and puff are obtained. Using the NMR signal volume of the NMR porosity standard sample per unit volume, the signal volume is converted into pore volume, and the recovery rate is calculated by combining the core volume and NMR porosity. , and the formula is: ； In the formula, is the recovery factor, %; are the changes in nuclear magnetic resonance signals after saturated oil and multiple cycles of huff and puff, dimensionless; C is the conversion coefficient of the nuclear magnetic resonance signal of the standard sample to the pore volume, dimensionless; is the nuclear magnetic resonance porosity, %; V is the core volume.

7. The calculation method for the recovery rate of different fluid components based on CO2 huff and puff and 2D nuclear magnetic resonance joint measurement according to claim 6, characterized in that, In step S5, combined with the multi-temperature stage pyrolysis fluid component division chart, according to the type of fluid components in the target area, by calculating the NMR signal amounts in different fluid regions of the 2D NMR T1-T2 spectrum, the recovery factor is subdivided into the recovery factors of different fluid components. The formula is: ； Wherein, , , are the recovery rates of free oil, adsorbed oil, and heavy oil, respectively, %; , , are the changes in nuclear magnetic resonance signals before and after multiple cycles of huff and puff of free oil, adsorbed oil, and heavy oil, respectively, dimensionless.

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