A method and system for quantitatively determining oil saturation in shale

Abstract

The present application provides a kind of shale oil saturation quantitative determination method and system, quantitative determination method includes: preparation shale plug sample;The shale plug sample is washed oil, dried, vacuum pressurized saturated deionized water, carries out one-dimensional nuclear magnetic resonance test, obtains shale plug sample pore volume;Step 3: the shale plug sample is dried again, and the dynamic change characteristics of the one-dimensional and two-dimensional nuclear magnetic resonance test results of the shale plug sample are obtained, and the oil output at the end of the displacement device is measured by measuring cylinder;According to the shale plug sample, the oil and water distribution area is determined, and the limit value of the two is divided;The oil saturation of different displacement stages of the displacement oil and the displacement non-oil shale plug sample is calculated respectively;According to the characteristic parameters of shale plug sample, an oil saturation calculation model is established based on least square method, and a chart is constructed.A shale oil saturation interpretation chart based on different displacement stages of nuclear magnetic characteristics is provided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas exploration, and particularly relates to a shale oil saturation quantitative determination method and system. BACKGROUND

[0002] With the decrease of conventional oil and gas resources and the transformation of global energy structure, unconventional oil and gas resources, especially shale oil resources, gradually become the focus of exploration and development. Quantitative calculation of oil saturation of shale oil reservoirs is of great significance for sweet spot layer division, movable resource evaluation and enhanced oil recovery of shale oil reservoirs. Compared with conventional sandstone and glutenite reservoirs, the conduction mechanism of shale reservoirs becomes extremely complex due to the presence of clay minerals, TOC and pyrite, resulting in large errors in the calculation results of saturation calculation models such as Archie formula, Indonesia equation and Simandoux equation. In addition, conventional distillation method and dry distillation method are difficult to apply due to the tightness of shale samples, complex pore structure and the presence of kerogen, such as kerogen cracking under high temperature conditions during dry distillation. Therefore, considering the deficiencies of the existing shale oil saturation quantitative determination methods, a shale oil saturation interpretation chart based on the characteristics of nuclear magnetic resonance at different displacement stages is designed.

[0003] Prior art related to the present application:

[0004] Chinese invention patent, patent number: CN202010403810.7, name: a method for calculating shale oil saturation. The invention includes the following steps: S1: sample preparation; S2: apparent density determination; S3: helium porosity determination; S4: calculation of hydrocarbon occupied porosity;

[0005] S5: total porosity calculation; S6: shale sample current oil saturation calculation; S7: shale sample original oil saturation calculation. The method has the advantages of clear idea, easy operation and simple calculation, but has the following deficiencies: (1) the invention uses pyrolysis parameter S1 as an approximation of liquid hydrocarbon content in shale samples to calculate oil saturation, but this parameter needs to be corrected for heavy hydrocarbons in addition to light hydrocarbons, i.e. part of the liquid hydrocarbons have too high boiling point and cannot be evaporated below 300℃; (2) the total porosity calculation process misses the pore space occupied by heavy hydrocarbons, non-hydrocarbons and asphaltene.

[0006] Prior art related to the present application:

[0007] CN202011374966.3, entitled "Shale oil saturation evaluation model, evaluation method and application". The invention measures nuclear magnetic resonance T2 spectrum on the basis of oil washing and low-temperature drying of mature shale samples; then, the samples are saturated with oil under vacuum and pressure and aged, and the experiment of imbibition of heavy water is carried out, and nuclear magnetic resonance T2 spectrum measurement is carried out in the process until the nuclear magnetic spectrum does not change basically, and the content of the oil stored in the pore throat is inversely calculated according to the sample nuclear magnetic signal amount. Finally, the oil saturation of the rock sample is obtained by using the oil volume and the pore volume. However, the oil saturation obtained by the method is the residual oil saturation of the sample after the imbibition of heavy water reaches equilibrium, and the type and content of the fluid stored in the sample at this time are different from those of the original untreated sample. SUMMARY

[0008] In view of the above problems, the present invention is proposed in order to provide a shale oil saturation quantitative determination method and system which overcomes the above problems or at least partially solves the above problems.

[0009] According to one aspect of the present invention, a shale oil saturation quantitative determination method is provided, which comprises:

[0010] Step 1: preparing a shale plug sample;

[0011] Step 2: washing the shale plug sample with oil and drying, and saturating deionized water under vacuum and pressure, and carrying out one-dimensional nuclear magnetic resonance test to obtain the pore volume of the shale plug sample;

[0012] Step 3: drying the shale plug sample again to obtain the dynamic change characteristics of one-dimensional and two-dimensional nuclear magnetic resonance test results of the shale plug sample and the oil amount at the end of the displacement device measured by a measuring cylinder;

[0013] Step 4: determining the oil and water distribution areas of the shale plug sample and dividing the limit values of the two areas;

[0014] Step 5: calculating the oil saturation of the shale plug sample at different displacement stages of the displaced oil and the displaced non-oil;

[0015] Step 6: extracting characteristic parameters from the shale plug sample and establishing an oil saturation calculation model based on the least squares method and constructing a chart.

[0016] Optionally, the step 3: drying the shale plug sample again to obtain the dynamic change characteristics of one-dimensional and two-dimensional nuclear magnetic resonance test results of the shale plug sample and the oil amount at the end of the displacement device measured by a measuring cylinder specifically comprises:

[0017] Step 3: The shale plug sample is dried again, saturated with oil under vacuum and pressure, and then displaced with deionized water under pressure, and one-dimensional and two-dimensional nuclear magnetic resonance tests are carried out during the displacement process to obtain the dynamic variation characteristics of the one-dimensional and two-dimensional nuclear magnetic resonance test results of the shale plug sample, and the oil output at the end of the displacement device is measured by a measuring cylinder.

[0018] Optionally, the oil used in the vacuum and pressure oil saturation is n-dodecane.

[0019] Optionally, step 4: determining the oil and water distribution areas and dividing the boundary values of the two according to the shale plug sample specifically includes:

[0020] According to the dynamic variation characteristics of the signal intensity of the two-dimensional nuclear magnetic T1-T2 spectrum of the shale plug sample at different displacement stages, the oil and water distribution areas are determined and the boundary values of the two are divided.

[0021] Optionally, step 6: extracting characteristic parameters from the shale plug sample and establishing an oil saturation calculation model based on the least square method and constructing a chart specifically includes:

[0022] According to the dynamic variation characteristics of the one-dimensional nuclear magnetic T2 spectrum of the shale plug sample at different displacement stages, the characteristic parameters are extracted and an oil saturation calculation model is established based on the least square method and a chart is constructed.

[0023] Optionally, the one-dimensional nuclear magnetic resonance test specifically includes:

[0024] During the displacement process, one-dimensional nuclear magnetic resonance experiments are carried out to measure the dynamic variation characteristics of the one-dimensional nuclear magnetic T2 spectrum of the sample at different displacement stages.

[0025] Optionally, the two-dimensional nuclear magnetic resonance test specifically includes:

[0026] During the displacement process, two-dimensional nuclear magnetic resonance experiments are carried out to measure the dynamic variation characteristics of the two-dimensional nuclear magnetic T1-T2 spectrum of the sample at different displacement stages.

[0027] Optionally, step 5: calculating the oil saturation of the displaced oil and the displaced oil shale plug sample at different displacement stages specifically includes:

[0028] S501: Calculate the oil saturation of the displaced oil shale plug sample at different displacement stages, for example, water displacement stage 1, and the oil saturation calculation method of the remaining stages is similar to that of water displacement stage 1:

[0029]

[0030]

[0031] In the formula: S is the oil saturation of the oil shale plug sample after the water flooding stage 1, %; V 饱油 S is the original oil volume of the oil-saturated oil shale plug sample, ml; V 水驱阶段1出油 S is the oil volume measured in the graduated cylinder after the water flooding stage 1, ml; V 孔隙 S is the pore volume measured in the oil displacement oil shale plug sample in step 2, ml; m 饱油前 S is the mass of the oil displacement oil shale plug sample before vacuum saturation, g; m 饱油后 S is the mass of the oil displacement oil shale plug sample after vacuum saturation, g; p 油 S is the oil density, g / cm 3 .

[0032] Step S502: Calculate the two-dimensional nuclear magnetic oil distribution area signal intensity ratio of all shale plug samples in different displacement stages:

[0033]

[0034] In the formula: S is the two-dimensional nuclear magnetic oil distribution area signal intensity ratio of the water flooding stage 1, decimal; S is the two-dimensional nuclear magnetic oil distribution area signal intensity of the water flooding stage 1, a.u.; S is the total signal intensity of the two-dimensional nuclear magnetic T1-T2 spectrum of the water flooding stage 1, a.u.

[0035] Step S503: Use the least square method to fit the two-dimensional nuclear magnetic oil distribution area signal intensity ratio of all oil displacement oil shale plug samples in different displacement stages and the measured oil saturation, and establish an oil saturation calculation model based on the two-dimensional nuclear magnetic oil distribution area signal intensity ratio.

[0036] Step S504: Use the fitting model established in S3, combined with the two-dimensional nuclear magnetic oil distribution area signal intensity ratio of the oil displacement sample in different displacement stages, to calculate the oil saturation of the oil displacement sample in different displacement stages.

[0037] Optionally, the step 6: extracting characteristic parameters from the shale plug sample and establishing an oil saturation calculation model based on the least square method and constructing a chart specifically includes:

[0038] Nuclear magnetic T2 spectrum characteristic parameter extraction:

[0039] Nuclear magnetic T2 geometric mean:

[0040]

[0041] In the formula: T 2gm S is the nuclear magnetic T2 geometric mean; T 2i S is the i-th nuclear magnetic resonance transverse relaxation time; for the corresponding porosity component; for the nuclear magnetic resonance test porosity value; N is the number of nuclear magnetic resonance T2 spectrum sampling points;

[0042] The first peak amplitude of the nuclear magnetic T2 spectrum is the longitudinal amplitude component corresponding to the first peak of the T2 spectrum.

[0043] The relationship between the characteristic parameters and the measured oil saturation is fitted by the least square method, an oil saturation calculation model based on one-dimensional nuclear magnetic T2 spectrum characteristic parameters is established, and a chart is constructed.

[0044] Optionally, the drying of the shale plug sample specifically comprises: placing the shale plug sample after oil washing into a drying device, and drying at 100 DEG C for about 12h.

[0045] The application further provides a shale oil saturation quantitative determination system, which is applied to the shale oil saturation quantitative determination method.

[0046] The plug sample preparation module is used for preparing the shale plug sample.

[0047] The one-dimensional nuclear magnetic resonance module is used for oil washing, drying, vacuumizing, pressurizing, deionized water saturation, one-dimensional nuclear magnetic resonance test, and obtaining the pore volume of the shale plug sample.

[0048] The oil output calculation module is used for re-drying the shale plug sample, obtaining the dynamic change characteristics of one-dimensional and two-dimensional nuclear magnetic resonance test results of the shale plug sample, and measuring the oil output at the end of the displacement device by using a measuring cylinder.

[0049] The limit value division module is used for determining the oil and water distribution regions of the shale plug sample and dividing the limit values of the two regions.

[0050] The saturation calculation module is used for calculating the oil saturation of the shale plug sample in different displacement stages of displacement oil and displacement non-oil, respectively.

[0051] The chart construction module is used for extracting characteristic parameters from the shale plug sample, establishing an oil saturation calculation model based on the least square method, and constructing a chart.

[0052] The application provides a shale oil saturation quantitative determination method and system, and the quantitative determination method comprises the following steps: step 1, shale plug samples are prepared; step 2, the shale plug samples are washed, dried, vacuumized, pressurized and saturated with deionized water, one-dimensional nuclear magnetic resonance testing is carried out, and the pore volume of the shale plug samples is obtained; step 3, the shale plug samples are dried again, the dynamic change characteristics of the one-dimensional and two-dimensional nuclear magnetic resonance test results of the shale plug samples are obtained, and the oil output at the end of the displacement cylinder metering displacement device is measured; step 4, the oil and water distribution areas of the shale plug samples are determined, and the limit values of the two areas are divided; step 5, the oil saturation of the shale plug samples in different displacement stages is calculated; step 6, characteristic parameters of the shale plug samples are extracted, an oil saturation calculation model is established based on the least square method, and a chart is constructed. A shale oil saturation interpretation chart based on the nuclear magnetic characteristics in different displacement stages is provided.

[0053] The above description is only a summary of the technical scheme of the application, in order to more clearly understand the technical means of the application, the content of the specification can be implemented, and in order to make the above and other purposes, characteristics and advantages of the application more obvious and easy to understand, the specific embodiments of the application are described below. BRIEF DESCRIPTION OF DRAWINGS

[0054] In order to more clearly illustrate the technical scheme of the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0055] Figure 1 A flowchart of a shale oil saturation quantitative determination method provided by the embodiments of the application is provided.

[0056] Figure 2 A dynamic change characteristic diagram of the one-dimensional nuclear magnetic test results of the F15 sample in different displacement stages provided by the embodiments of the application is provided.

[0057] Figure 3 A dynamic change characteristic diagram of the two-dimensional nuclear magnetic T1-T2 spectrum of the F15 sample in different displacement stages provided by the embodiments of the application is provided.

[0058] Figure 4 A relationship diagram of the oil region signal intensity and the measured oil saturation of the two-dimensional nuclear magnetic resonance is provided.

[0059] Figure 5 A relationship analysis diagram of the nuclear magnetic characteristic parameters and the measured oil saturation is provided.

[0060] Figure 6An oil saturation fitting effect test chart provided for the embodiment of the present application;

[0061] Figure 7 A shale sample oil saturation estimation chart provided for the embodiment of the present application. DETAILED DESCRIPTION

[0062] Exemplary embodiments of the present disclosure will be described in greater detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it is understood that the present disclosure can be embodied in various forms without being limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure can be more thoroughly understood, and so that the scope of the present disclosure can be completely conveyed to those skilled in the art.

[0063] The terms "include" and "have" and any variations thereof in the specification, claims and drawings of the present application are intended to cover the non-exclusive inclusion, for example, the inclusion of a series of steps or units.

[0064] The technical solutions of the present application will be described in further detail below in conjunction with the drawings and embodiments.

[0065] As shown in the drawings, Figure 1 A shale oil formation oil saturation quantitative determination method based on two-dimensional nuclear magnetic experiments, comprising the following steps:

[0066] Step 1: shale plug sample preparation;

[0067] Step 2: shale plug sample oil washing, drying, vacuum pressure saturation of deionized water, one-dimensional nuclear magnetic resonance test is carried out, and shale plug sample pore volume is obtained;

[0068] Step 3: The shale plug sample is dried again, saturated with oil (n-dodecane) after vacuum pressure, and then displaced with deionized water under pressure, and one-dimensional and two-dimensional nuclear magnetic resonance tests are carried out during displacement to obtain the dynamic change characteristics of the one-dimensional and two-dimensional nuclear magnetic resonance test results of the shale plug sample and the oil displacement amount at the end of the displacement device is measured by a measuring cylinder;

[0069] Step 4: According to the dynamic change characteristics of the signal intensity of the two-dimensional nuclear magnetic T1-T2 spectrum of the shale plug sample at different displacement stages, the oil and water distribution areas are determined and the boundary values are divided;

[0070] Step 5: Calculate the oil saturation of the shale plug sample at different displacement stages for displacement oil and displacement non-oil, respectively;

[0071] Step 6: According to the dynamic change characteristics of the one-dimensional nuclear magnetic T2 spectrum of the shale plug sample at different displacement stages, the characteristic parameters are extracted, and an oil saturation calculation model is established based on the least squares method and a chart is constructed.

[0072] The shale plug sample preparation process in step 1 is as follows:

[0073] The block-shaped shale sample to be analyzed is cut into a plug sample with a diameter of about 2.5 cm and a height of about 4 cm.

[0074] The treatment in step 2 includes shale plug sample oil washing, drying, vacuum pressure saturation of deionized water, one-dimensional nuclear magnetic resonance experiment test:

[0075] Shale plug sample oil washing: the shale plug sample is placed in a Soxhlet extraction device for cyclic immersion in oil washing, the solvent is toluene, and the oil washing time is 7 days;

[0076] Shale plug sample drying: after oil washing, the shale plug sample is placed in a drying device, and dried at 100°C for about 12h;

[0077] Vacuum pressure saturation of deionized water: after oil washing and drying, the shale plug sample is placed in a vacuum pressure saturation device, vacuumed (about -0.1 MPa) for about 2h, and then saturated with deionized water under pressure (15 MPa, 12h);

[0078] One-dimensional nuclear magnetic resonance test: one-dimensional nuclear magnetic resonance test is carried out on the shale plug sample saturated with deionized water, and the pore volume of the shale plug sample is obtained, referring to the standard SY / T 6490-2014.

[0079] The treatment in step 3 includes shale plug sample drying, vacuum pressure oil saturation, pressure displacement, one-dimensional nuclear magnetic resonance test, two-dimensional nuclear magnetic resonance test, and end oil metering;

[0080] Shale plug sample drying: the shale sample is placed in a drying device, and dried at 100°C for about 12h;

[0081] Vacuum pressure oil saturation: after drying, the shale plug sample is placed in a vacuum pressure saturation device, vacuumed (about -0.1 MPa) for about 2h, and then saturated with n-dodecane under pressure (15 MPa, 12h);

[0082] Pressure displacement: after pressure oil saturation, the shale plug sample is placed in a displacement device, and displacement experiment is carried out with deionized water (displacement pressure is about 40 MPa);

[0083] One-dimensional nuclear magnetic resonance test: during displacement, one-dimensional nuclear magnetic resonance experiment is carried out on the shale plug sample to obtain the dynamic change characteristics of one-dimensional nuclear magnetic T2 spectrum of the sample at different displacement stages;

[0084] Two-dimensional nuclear magnetic resonance test: during displacement, two-dimensional nuclear magnetic resonance experiment is carried out on the shale plug sample to obtain the dynamic change characteristics of two-dimensional nuclear magnetic T1-T2 spectrum of the sample at different displacement stages;

[0085] Displacement device end oil output metering: use a measuring cylinder to measure the oil output at the displacement device outlet.

[0086] Step 4: Determine the oil and water distribution areas and divide the boundary values according to the dynamic change characteristics of the signal intensity of the two-dimensional nuclear magnetic T1-T2 spectrum of the shale plug sample at different displacement stages. The specific operation is as follows:

[0087] Analyze the two-dimensional nuclear magnetic measurement results of the shale plug sample at different displacement stages (oil-saturated state, water drive stage 1, water drive stage 2, …), and divide the oil and water distribution areas according to the signal intensity change characteristics of the two-dimensional nuclear magnetic T1-T2 spectrum, and determine the boundary values.

[0088] Step 5: The oil saturation calculation process of the displacement oil and non-displacement oil shale plug sample at different displacement stages is as follows:

[0089] S1: Calculate the oil saturation of the displacement oil shale plug sample at different displacement stages (take water drive stage 1 as an example, the oil saturation calculation method of the remaining stages is similar to that of water drive stage 1):

[0090]

[0091]

[0092] In the formula: is the oil saturation of the displacement oil shale plug sample after water drive stage 1, %; V 饱油 is the original oil volume of the oil-saturated shale plug sample, ml; V 水驱阶段1出油 is the oil volume measured in the measuring cylinder after water drive stage 1, ml; V 孔隙 is the pore volume of the displacement oil shale plug sample measured in step 2, ml; m 饱油前 is the mass of the displacement oil shale plug sample before vacuum oil saturation, g; m 饱油后 is the mass of the displacement oil shale plug sample after vacuum oil saturation, g; p 油 is the oil density, g / cm 3 .

[0093] S2: Calculate the signal intensity proportion of the two-dimensional nuclear magnetic oil distribution area of all shale plug samples at different displacement stages (take water drive stage 1 as an example, the oil saturation calculation method of the remaining stages is similar to that of water drive stage 1):

[0094]

[0095] In the formula: is the signal intensity proportion of the two-dimensional nuclear magnetic oil distribution area of water drive stage 1, decimal; is the signal intensity of the two-dimensional nuclear magnetic oil distribution area of water drive stage 1, a.u.; Total signal intensity of 2D NMR T1-T2 map for water flooding stage 1, a.u.

[0096] S3: Use the least square method to fit the relationship between the signal intensity ratio of the oil distribution area of 2D NMR and the measured oil saturation of all the different displacement stages of the shale plug sample, and establish an oil saturation calculation model based on the signal intensity ratio of the oil distribution area of 2D NMR.

[0097] S4: Use the fitting model established in S3, combined with the signal intensity ratio of the oil distribution area of 2D NMR of the different displacement stages of the non-oil-out sample, to calculate the oil saturation of the different displacement stages of the non-oil-out sample:

[0098] The operation in step 6 includes extracting characteristic parameters, establishing a relationship model of characteristic parameters and oil saturation, and constructing a chart according to the dynamic change characteristics of the 1D NMR T2 spectrum of the shale plug sample at different displacement stages:

[0099] S1: NMR T2 spectrum characteristic parameter extraction:

[0100] NMR T2 geometric mean:

[0101]

[0102] In the formula: T 2gm is the NMR T2 geometric mean; T 2i is the ith NMR transverse relaxation time; is the corresponding porosity component; is the NMR test porosity value; N is the number of NMR T2 spectrum sampling points.

[0103] NMR T2 spectrum first peak amplitude: the longitudinal amplitude component corresponding to the first peak of the T2 spectrum.

[0104] S2: Use the least square method to fit the relationship between the characteristic parameters and the measured oil saturation, and establish an oil saturation calculation model based on the 1D NMR T2 spectrum characteristic parameters and construct a chart.

[0105] Beneficial effect: Provide a shale oil saturation interpretation chart based on the characteristics of different displacement stages of NMR.

[0106] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for quantitative determination of oil saturation in shale, characterized by, The quantitative determination method comprises: Step 1: preparing a shale plug sample; Step 2: washing and drying the shale plug sample, vacuumizing and pressurizing the shale plug sample to be saturated with deionized water, and performing one-dimensional nuclear magnetic resonance test to obtain the pore volume of the shale plug sample; Step 3: drying the shale plug sample again, vacuumizing and pressurizing the shale plug sample to be saturated with oil, pressurizing the shale plug sample with deionized water to displace the oil, and performing one-dimensional and two-dimensional nuclear magnetic resonance test during the displacement process to obtain the dynamic change characteristics of the one-dimensional and two-dimensional nuclear magnetic resonance test results of the shale plug sample and the oil output at the end of the displacement device measured by a measuring cylinder; Step 4: determining the oil and water distribution areas of the shale plug sample and dividing the limit values of the two areas; Step 5: calculating the oil saturation of the oil-displaced shale plug sample and the oil-un-displaced shale plug sample at different displacement stages, comprising: Step S501: calculating the oil saturation of the oil-displaced shale plug sample at different displacement stages, taking water displacement stage 1 as an example, and the oil saturation calculation method of the remaining stages is similar to that of water displacement stage 1; where: Vdispl is the oil saturation, % of the oil shale plug displaced after waterflood phase 1 ; 饱油 Vorig is the original oil volume, ml, of the oil-saturated oil shale plug; 水驱阶段1出油 Vmeas is the volume of oil measured in the graduated cylinder, ml, after waterflood phase 1 ; 孔隙 Vpor is the pore volume, ml, measured in step 2 of displacing the oil from the oil shale plug; 饱油前 mpre is the mass, g, of the oil-saturated oil shale plug before evacuation; 饱油后 mpost is the mass, g, of the oil-saturated oil shale plug after evacuation; 油 p is the density of the oil, g / cm3; and 3 ; Step S502: calculating the signal intensity proportion of the two-dimensional nuclear magnetic oil distribution area at different displacement stages of all shale plug samples; wherein: is the fraction of the signal intensity of the 2D NMR oil distribution region for waterflood stage 1, decimal; is the signal intensity of the 2D NMR oil distribution region for waterflood stage 1, a.u.; is the total signal intensity of the 2D NMR T1-T2 map for waterflood stage 1, a.u.; Step S503: fitting the relationship between the signal intensity proportion of the two-dimensional nuclear magnetic oil distribution area at different displacement stages of all oil-displaced shale plug samples and the measured oil saturation by using the least square method, and establishing an oil saturation calculation model based on the signal intensity proportion of the two-dimensional nuclear magnetic oil distribution area; Step S504: using the fitting model established in S503, combining the signal intensity proportion of the two-dimensional nuclear magnetic oil distribution area at different displacement stages of the oil-un-displaced sample, and calculating the oil saturation of the oil-un-displaced sample at different displacement stages; Step 6: extracting characteristic parameters from the shale plug sample and establishing an oil saturation calculation model based on the least square method and constructing a chart, comprising: Extraction of nuclear magnetic T2 spectrum characteristic parameters: Nuclear magnetic T2 geometric mean value: where: T 2gm is the geometric mean of the nuclear magnetic T2; T 2i is the i-th nuclear magnetic resonance transverse relaxation time; is the corresponding porosity component; is the nuclear magnetic resonance test porosity value; N is the number of nuclear magnetic resonance T2 spectrum sampling points; Nuclear magnetic T2 spectrum first peak amplitude: the longitudinal amplitude component corresponding to the T2 spectrum first peak; Fitting the relationship between the characteristic parameters and the measured oil saturation by using the least square method, establishing an oil saturation calculation model based on the one-dimensional nuclear magnetic T2 spectrum characteristic parameters, and constructing a chart.

2. The method of quantitative determination of oil saturation in shale according to claim 1, characterized in that, The oil used in the vacuum pressurized oil saturation is n-dodecane.

3. The method of claim 1, wherein, Step 4: determining the oil and water distribution areas of the shale plug sample and dividing the limit values of the two areas specifically comprises: According to the dynamic change characteristics of the signal intensity of the two-dimensional nuclear magnetic T1-T2 spectrum of the shale plug sample at different displacement stages, the oil and water distribution areas are determined and the limit values of the two areas are divided.

4. The method of claim 1, wherein, Step 6: extracting characteristic parameters from the shale plug sample and establishing an oil saturation calculation model based on the least square method and constructing a chart specifically comprises: According to the dynamic change characteristics of the one-dimensional nuclear magnetic T2 spectrum of the shale plug sample at different displacement stages, the characteristic parameters are extracted and an oil saturation calculation model is established based on the least square method and a chart is constructed.

5. The method of quantitative determination of oil saturation in shale according to claim 4, characterized in that, The one-dimensional nuclear magnetic resonance test specifically comprises: During the displacement process, one-dimensional nuclear magnetic resonance experiment measurement of the shale plug sample is performed to obtain the dynamic change characteristics of the one-dimensional nuclear magnetic T2 spectrum of the sample at different displacement stages.

6. The method of quantitative determination of oil saturation in shale according to claim 3, characterized in that, The two-dimensional nuclear magnetic resonance test specifically comprises: During the displacement process, two-dimensional nuclear magnetic resonance experiment measurement of the shale plug sample is performed to obtain the dynamic change characteristics of the two-dimensional nuclear magnetic T1-T2 spectrum of the sample at different displacement stages.

7. The method of claim 1, wherein, The drying of the shale plug sample specifically comprises: placing the shale plug sample after oil washing into a drying device, drying for 12 hours at 100 DEG C.

8. A shale oil saturation quantitative determination system applied to the shale oil saturation quantitative determination method in any one of claims 1-7, characterized in that, The determination system comprises: a plug sample preparation module for preparing a shale plug sample; a one-dimensional nuclear magnetic resonance module for oiling, drying, vacuumizing, pressurizing, and saturating the shale plug sample with deionized water, and carrying out one-dimensional nuclear magnetic resonance test to obtain the pore volume of the shale plug sample; an oil output calculation module for again drying the shale plug sample, obtaining the dynamic change characteristics of the one-dimensional and two-dimensional nuclear magnetic resonance test results of the shale plug sample, and measuring the oil output at the end of the displacement device by using a measuring cylinder; a limit value division module for determining the oil and water distribution areas of the shale plug sample and dividing the limit values of the two areas; a saturation calculation module for calculating the oil saturation of the shale plug sample at different displacement stages of the displaced oil and the non-displaced oil, respectively; a chart construction module for extracting characteristic parameters from the shale plug sample and establishing an oil saturation calculation model based on the least square method and constructing a chart.

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