Method for evaluating producing rate of shale oil in different occurrence states in imbibition process by two-dimensional nuclear magnetic resonance

Abstract

The application discloses a method for evaluating the producing rate of shale oil in different occurrence states in a two-dimensional nuclear magnetic osmosis process, which comprises the following steps: using nuclear magnetic resonance to analyze unsaturated oil, saturated oil and experimental shale samples after osmosis, inverting the obtained relaxation time nuclear magnetic data to obtain a nuclear magnetic spectrum, dividing the nuclear magnetic spectrum into free oil area and adsorbed mutual solubility oil area according to the hydrogen signal of oil in the nuclear magnetic spectrum, and calculating the peak area of the free oil area and the adsorbed mutual solubility oil area; the producing rate of free oil and the producing rate of adsorbed mutual solubility oil in the experimental shale sample can be obtained by calculating the area change of the free oil hydrogen signal peak and the adsorbed mutual solubility oil hydrogen signal peak of the experimental shale sample before and after different osmosis time. The experimental method is simple and accurate, can quantitatively evaluate the producing rate of free oil and adsorbed mutual solubility oil in shale, and provides important parameters and basis for numerical simulation of an oil reservoir and actual development.

Description

Technical Field

[0001] This invention relates to the field of petroleum engineering, and in particular to a method for evaluating the utilization rate of shale oil in different occurrence states during the adsorption process using two-dimensional nuclear magnetic resonance. Background Technology

[0002] Shale oil, as an important unconventional energy source, boasts enormous reserves and is gradually becoming a major oil and gas resource for ensuring effective energy supply in the future. However, shale oil reservoirs are rich in organic matter, highly heterogeneous, and have low permeability, making their development difficult and costly. Numerous laboratory experiments have shown that the primary recovery rate of shale oil reservoirs is only 10%–15% lower than the geological reserves, with a large amount of crude oil still existing in an adsorbed and miscible state within the shale organic matter. Therefore, the key to improving the recovery rate of shale oil reservoirs lies in increasing the utilization rate of the adsorbed and miscible crude oil within the organic matter.

[0003] Shale oil reservoirs often have very low initial water saturation due to hydrocarbon generation and drainage processes, and their pores are generally at the micro-nano scale, resulting in much stronger capillary forces than conventional reservoirs. Under the influence of these strong capillary forces, fracturing fluid is drawn into the pores and displaces the crude oil, creating an adsorption-driven oil displacement effect. The capillary force acting on the oil-water-pore interface can generate a pressure gradient much higher than the production pressure differential. Therefore, adsorption is a crucial driving force for oil displacement in tight reservoirs.

[0004] Current technologies only evaluate the total utilization rate of shale oil during the infiltration process using one-dimensional nuclear magnetic resonance (NMR), which cannot accurately distinguish the utilization rates of free oil and adsorbed miscible oil. Two-dimensional NMR technology can obtain T2-T1 spectra, analyzing hydrogen signals from two dimensions, but it is currently mainly used to differentiate the mobility of oil and water in different pores. It does not quantitatively describe the percentage content of free oil and adsorbed miscible oil in shale, and it cannot measure the utilization rate of oil under different occurrence states during the infiltration process. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and propose a method for evaluating the recovery rate of shale oil in different occurrence states during the infiltration process using two-dimensional nuclear magnetic resonance (NMR). This method addresses the problem of unclear calculation of the recovery volume of free and adsorbed miscible oil in the shale oil development process using fracturing fluid infiltration. It proposes to quantitatively calculate the recovery volume of free and adsorbed miscible oil in shale using two-dimensional NMR, thereby allowing for targeted adjustments to development parameters to effectively utilize the adsorbed miscible oil and improve shale oil recovery. This also provides important parameters and basis for reservoir numerical simulation and actual development.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] On the one hand, this invention discloses a method for evaluating the shale oil recovery rate under different occurrence states during the adsorption process using two-dimensional nuclear magnetic resonance, comprising the following steps:

[0008] (1) Experimental shale samples of unsaturated oil were analyzed by nuclear magnetic resonance to obtain the T2-T1 two-dimensional relaxation time nuclear magnetic resonance data of the unsaturated oil samples, where T2 is the transverse relaxation time and T1 is the longitudinal relaxation time. The T2-T1 two-dimensional relaxation time nuclear magnetic resonance data of the unsaturated oil samples were inverted to obtain the T2-T1 two-dimensional nuclear magnetic spectrum of the unsaturated oil samples.

[0009] (2) Experimental shale samples of saturated oil were analyzed by nuclear magnetic resonance to obtain the T2-T1 two-dimensional relaxation time nuclear magnetic data of the saturated oil samples. The T2-T1 two-dimensional relaxation time nuclear magnetic data of the saturated oil samples were inverted to obtain the T2-T1 two-dimensional nuclear magnetic spectrum of the saturated oil samples.

[0010] (3) Divide the T2-T1 two-dimensional NMR spectrum of the saturated oil sample into a free oil region and an adsorbed miscible oil region;

[0011] The peak area of ​​the hydrogen signal in the adsorbed miscible oil region in the T2-T1 two-dimensional NMR spectrum of the saturated oil sample is denoted as S. ta The peak area of ​​the hydrogen signal in the free oil region of the T2-T1 two-dimensional NMR spectrum of the saturated oil sample is denoted as S. tf ;

[0012] (4) Divide the T2-T1 two-dimensional NMR spectrum of the unsaturated oil sample into a free oil region and an adsorbed miscible oil region;

[0013] The peak area of ​​the hydrogen signal in the adsorbed miscible oil region in the T2-T1 two-dimensional NMR spectrum of the unsaturated oil sample is denoted as S. oa The peak area of ​​the hydrogen signal in the free oil region of the T2-T1 two-dimensional NMR spectrum of the unsaturated oil sample is denoted as S. of ;

[0014] (5) The experimental shale sample of the saturated oil is immersed in heavy water to spontaneously absorb the oil, and the experimental shale sample after absorption is obtained. The experimental shale sample after absorption is analyzed by nuclear magnetic resonance to obtain the T2-T1 two-dimensional relaxation time nuclear magnetic resonance data after absorption. The T2-T1 two-dimensional relaxation time nuclear magnetic resonance data after absorption is inverted to obtain the T2-T1 two-dimensional nuclear magnetic resonance spectrum after absorption.

[0015] (6) Divide the T2-T1 two-dimensional NMR spectrum after permeation into a free oil region and an adsorbed miscible oil region;

[0016] The peak area of ​​the hydrogen signal in the adsorbed miscible oil region in the T2-T1 two-dimensional NMR spectrum of the experimental shale sample after the first infiltration is denoted as S. ta-1The peak area of ​​the hydrogen signal in the free oil region in the T2-T1 two-dimensional NMR spectrum of the experimental shale sample after the first infiltration is denoted as S. tf-1 ;

[0017] (7) Repeat steps (5)-(6) to obtain the peak area of ​​hydrogen signal in the free oil region in the T2-T1 two-dimensional NMR spectrum of the experimental shale sample after multiple infiltrations. This peak area is denoted as S. tf-i The peak area of ​​hydrogen signals in the adsorbed miscible oil region in the T2-T1 two-dimensional NMR spectrum of the experimental shale sample after multiple infiltrations is denoted as S. ta-i , where i is the number of absorptions;

[0018] (8) The peak area S of hydrogen signal in the free oil region in the T2-T1 two-dimensional NMR spectra of experimental shale samples before and after infiltration. tf-i The peak area S of the hydrogen signal in the adsorbed miscible oil region ta-i The utilization rate of free oil and adsorbed miscible oil in the experimental shale sample can be calculated from the area change.

[0019] In one possible design, step (3), dividing the T2-T1 two-dimensional NMR spectrum of the saturated oil sample into a free oil region and an adsorbed miscible oil region, includes:

[0020] Based on the differences in hydrogen signals of oil molecules in different occurrence states in the T2-T1 two-dimensional NMR spectrum of the saturated oil sample, the critical relaxation time of the free state oil and the critical relaxation time of the adsorbed miscible state oil in the T2-T1 two-dimensional NMR spectrum of the saturated oil sample are determined.

[0021] Based on the critical relaxation time of the free oil and the critical relaxation time of the adsorbed miscible oil in the saturated oil sample, the T2-T1 two-dimensional NMR spectrum of the saturated oil sample is divided into a free oil region and an adsorbed miscible oil region.

[0022] In one possible design, step (4) of dividing the T2-T1 two-dimensional NMR spectrum of the unsaturated oil sample into a free oil region and an adsorbed miscible oil region includes:

[0023] Based on the critical relaxation time of the free oil and the critical relaxation time of the adsorbed miscible oil in the T2-T1 two-dimensional NMR spectrum of the saturated oil sample, the T2-T1 two-dimensional NMR spectrum of the unsaturated oil sample is divided into a free oil region and an adsorbed miscible oil region.

[0024] In one possible design, step (6) involves dividing the T2-T1 two-dimensional NMR spectrum after percolation into a free oil region and an adsorbed miscible oil region, including:

[0025] Based on the critical relaxation time of the free oil and the critical relaxation time of the adsorbed miscible oil in the T2-T1 two-dimensional NMR spectrum of the saturated oil sample, the T2-T1 two-dimensional NMR spectrum after permeation is divided into a free oil region and an adsorbed miscible oil region.

[0026] In one possible design, the experimental shale samples contain shale oil in different occurrence states, including free oil and adsorbed miscible oil.

[0027] In one possible design, the peak areas of hydrogen signals from shale oil in different occurrence states in the T2-T1 two-dimensional NMR spectrum of the unsaturated oil sample are denoted as S. o S o For the S oa and the S of The sum of;

[0028] The peak areas of hydrogen signals from shale oil in different occurrence states in the T2-T1 two-dimensional NMR spectra of the saturated oil sample are denoted as S. t S t For the S ta and the S tf The sum of;

[0029] The peak areas of the oil and hydrogen signals of shale in different occurrence states in the T2-T1 two-dimensional NMR spectra of the experimental shale samples after infiltration are denoted as S. t-i S t-i For the S ta-i and the S tf-i The sum of , where i is the number of osmosis.

[0030] In one possible design, the expression for the utilization rate of free oil in the experimental shale sample by the infiltration process is:

[0031]

[0032] In the formula, η tf-i S represents the utilization rate of free oil in the experimental shale sample after the i-th infiltration, where i is a positive integer ≥ 1; tf S represents the peak area of ​​the hydrogen signal in the free oil region of the T2-T1 two-dimensional NMR spectrum of a saturated oil sample; of S represents the peak area of ​​the hydrogen signal in the free oil region of the T2-T1 two-dimensional NMR spectrum of an unsaturated oil sample; tf-i The peak area of ​​hydrogen signal in the free oil region in the T2-T1 two-dimensional NMR spectrum of the experimental shale sample after the i-th infiltration.

[0033] In one possible design, the expression for the utilization rate of adsorbed miscible oil in the experimental shale sample during the infiltration process is:

[0034]

[0035] In the formula, η ta-i S represents the utilization rate of adsorbed miscible oil in the experimental shale sample after the i-th infiltration, where i is a positive integer ≥ 1; ta S represents the peak area of ​​hydrogen signals in the adsorbed miscible oil region in the T2-T1 two-dimensional NMR spectrum of a saturated oil sample; oa S represents the peak area of ​​hydrogen signals in the adsorbed miscible oil region in the T2-T1 two-dimensional NMR spectrum of an unsaturated oil sample; ta-i The peak area of ​​hydrogen signal in the adsorbed miscible oil region in the T2-T1 two-dimensional NMR spectrum of the experimental shale sample after the i-th infiltration is denoted as .

[0036] In one possible design, the expression for the total shale oil utilization rate under different occurrence states during the infiltration process is:

[0037]

[0038] In the formula, η t-i S represents the total utilization rate of shale oil in different occurrence states in the experimental shale sample after the i-th infiltration, where i is a positive integer ≥ 1; t The peak areas of hydrogen signals in shale oil under different occurrence states are shown in the T2-T1 two-dimensional NMR spectra of saturated oil samples; S o The peak areas of hydrogen signals in shale oil at different occurrence states are shown in the T2-T1 two-dimensional NMR spectra of unsaturated oil samples; S t-i The peak areas of the oil and hydrogen signals in the T2-T1 two-dimensional NMR spectra of the experimental shale sample after the i-th infiltration are the peak areas of the shale oil and hydrogen signals in different occurrence states.

[0039] On the other hand, the present invention also discloses the application of the above method in reservoir numerical simulation and actual development.

[0040] The beneficial effects of this invention are as follows:

[0041] Nuclear magnetic resonance (NMR) technology has unique advantages in characterizing reservoirs and contained fluids. Its measurement signals are not affected by the rock skeleton and rock sample shape, and it has different NMR responses to different fluids in the reservoir. It can provide rich information on reservoir properties and contained fluids, and can penetrate deep into the object without damaging the sample. The measurement process is rapid, accurate and has high resolution.

[0042] This invention first identifies the T2 and T1 relaxation intervals of hydrogen nuclei (excluding kerogen) in a two-dimensional nuclear magnetic resonance (NMR) spectrum based on the signal intensity of the hydrogen nuclei. These intervals are then used to delineate regions for free oil and adsorbed miscible oil, yielding the respective areas of free oil and adsorbed miscible oil. These areas represent the content of free oil and adsorbed miscible oil. This method is simple and accurate, enabling quantitative evaluation of the content of free oil and adsorbed miscible oil in shale, and providing important parameters and basis for reservoir numerical simulation and actual development.

[0043] This invention, based on the quantitative evaluation of the content of free oil and adsorbed miscible oil in shale, uses nuclear magnetic resonance (NMR) technology to analyze the percolation process of heavy water in shale oil samples. Utilizing the characteristic that heavy water has no signal in the NMR spectrum while oil does, the distribution characteristics of residual oil in the core during the percolation process are visually presented. Simultaneously, by comparing and calculating the signal changes of oil in the NMR spectra at different percolation times, the utilization rate of oil in the pores due to percolation and the distribution characteristics of residual oil in the core can be obtained, accurately calculating the utilization rate of shale oil in different occurrence states during the percolation process. The method of this invention can obtain conditions for increasing the production of adsorbed miscible oil, such as pressure and interfacial tension, providing important parameters and basis for reservoir numerical simulation and actual development.

[0044] This method determines the critical relaxation time of free and adsorbed miscible oil by comparing the two-dimensional nuclear magnetic resonance spectra of unsaturated and saturated oil in experimental shale samples during the percolation process. This allows for more reasonable and accurate regional division and enables quantitative evaluation of the momentum of free and adsorbed miscible oil during the percolation process in shale.

[0045] The method of the present invention uses a simple device structure, which does not require complex analytical equipment such as chromatographic testing, but only a saturation device and nuclear magnetic resonance equipment.

[0046] The method of this invention uses the nuclear magnetic resonance signal of saturated alkanes in the core as a method for measuring the amount of alkane mobilized in the core, and the measurement process is fast and accurate.

[0047] The method of this invention simulates the process of fracturing fluid extraction of formation crude oil using an absorption method, which is quick and convenient. By scanning experimental samples at different absorption times using nuclear magnetic resonance technology, the changes in free oil and adsorbed miscible oil in shale samples at different absorption times can be obtained, avoiding the problems of incomplete or unreached absorption during the absorption process, and the obtained data has more theoretical guiding significance. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 This is the T2-T1 two-dimensional NMR spectrum of sample A, which is an unsaturated oil.

[0050] Figure 2 This is the T2-T1 two-dimensional NMR spectrum of sample A after oil saturation;

[0051] Figure 3 The T2-T1 two-dimensional NMR spectra of sample A after different cumulative percolation times are: (a) percolation for 2 h, (b) percolation for 7 h, (c) percolation for 11 h, (d) percolation for 27 h, and (e) percolation for 37 h.

[0052] Figure 4 This is a graph showing the relationship between the utilization rate of shale oil in different occurrence states and different cumulative percolation times in sample A;

[0053] Figure 5 This is the T2-T1 two-dimensional NMR spectrum of sample B, which is an unsaturated oil.

[0054] Figure 6 This is the T2-T1 two-dimensional NMR spectrum of sample B after oil saturation;

[0055] Figure 7 The T2-T1 two-dimensional NMR spectra of sample B after different cumulative percolation times are: (a) percolation for 4 h, (b) percolation for 20 h, (c) percolation for 33 h, (d) percolation for 47 h, and (e) percolation for 57 h.

[0056] Figure 8 This is a graph showing the relationship between the utilization rate of shale oil in different occurrence states and different cumulative percolation times in sample B. Detailed Implementation

[0057] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0058] On the one hand, this invention discloses a method for evaluating the shale oil recovery rate under different occurrence states during the adsorption process using two-dimensional nuclear magnetic resonance, comprising the following steps:

[0059] (1) Experimental shale samples of unsaturated oil were analyzed by nuclear magnetic resonance to obtain the two-dimensional relaxation time NMR data of the unsaturated oil samples from T2 to T1, where T2 is the transverse relaxation time and T1 is the longitudinal relaxation time. The two-dimensional relaxation time NMR data of the unsaturated oil samples from T2 to T1 were inverted to obtain the two-dimensional NMR spectrum of the unsaturated oil samples from T2 to T1.

[0060] (2) Experimental shale samples of saturated oil were analyzed by nuclear magnetic resonance to obtain the T2-T1 two-dimensional relaxation time nuclear magnetic resonance data of the saturated oil samples. The T2-T1 two-dimensional relaxation time nuclear magnetic resonance data of the saturated oil samples were inverted to obtain the T2-T1 two-dimensional nuclear magnetic spectrum of the saturated oil samples.

[0061] (3) Divide the T2-T1 two-dimensional NMR spectrum of the saturated oil sample into a free oil region and an adsorbed miscible oil region;

[0062] The peak area of ​​hydrogen signals in the adsorbed miscible oil region of the T2-T1 two-dimensional NMR spectrum of a saturated oil sample is denoted as S. taThe peak area of ​​the hydrogen signal in the free oil region in the T2-T1 two-dimensional NMR spectrum of a saturated oil sample is denoted as S. tf ;

[0063] (4) Divide the T2-T1 two-dimensional NMR spectrum of the unsaturated oil sample into a free oil region and an adsorbed miscible oil region;

[0064] The peak area of ​​hydrogen signals in the adsorbed miscible oil region of the T2-T1 two-dimensional NMR spectrum of an unsaturated oil sample is denoted as S. oa The peak area of ​​the hydrogen signal in the free oil region in the T2-T1 two-dimensional NMR spectrum of an unsaturated oil sample is denoted as S. of ;

[0065] (5) The experimental shale sample with saturated oil was immersed in heavy water to spontaneously absorb the oil, and the experimental shale sample after absorption was obtained. The experimental shale sample after absorption was analyzed by nuclear magnetic resonance to obtain the T2-T1 two-dimensional relaxation time nuclear magnetic data after absorption. The T2-T1 two-dimensional relaxation time nuclear magnetic data after absorption was inverted to obtain the T2-T1 two-dimensional nuclear magnetic spectrum after absorption.

[0066] (6) The T2-T1 two-dimensional NMR spectrum after permeation was divided into a free oil region and an adsorbed miscible oil region;

[0067] The peak area of ​​hydrogen signals in the adsorbed miscible oil region of the T2-T1 two-dimensional NMR spectrum of the experimental shale sample after the first infiltration is denoted as S. ta-1 The peak area of ​​the hydrogen signal in the free oil region in the T2-T1 two-dimensional NMR spectrum of the experimental shale sample after the first infiltration is denoted as S. tf-1 ;

[0068] (7) Repeat steps (5)-(6) to obtain the peak area of ​​hydrogen signal in the free oil region in the T2-T1 two-dimensional NMR spectrum of the experimental shale sample after multiple infiltrations. This peak area is denoted as S. tf-i The peak area of ​​hydrogen signals in the adsorbed miscible oil region in the T2-T1 two-dimensional NMR spectrum of the experimental shale sample after multiple infiltrations is denoted as S. ta-i , where i is the number of absorptions;

[0069] (8) The peak area S of hydrogen signal in the free oil region in the T2-T1 two-dimensional NMR spectra of experimental shale samples before and after infiltration. tf-i The peak area S of the hydrogen signal in the adsorbed miscible oil region ta-i The utilization rate of free oil and adsorbed miscible oil in the experimental shale sample can be calculated from the area change.

[0070] Preferably, before performing nuclear magnetic resonance analysis on the experimental shale samples containing unsaturated oil, the experimental shale samples are thoroughly cleaned, dried, and prepared into granules. This ensures that the experimental shale samples are in full contact with the simulated oil and heavy water, which is beneficial for the analysis of experimental phenomena.

[0071] Preferably, the saturated oil sample in the experimental shale sample is a simulated oil dodecane.

[0072] Preferably, in step (2), the experimental saturated oil shale sample is obtained through the following steps:

[0073] The unsaturated oil experimental shale sample was cleaned and dried. The vacuum degree of the unsaturated oil experimental shale sample was brought to 0.1 Pa by vacuuming. Then, the oil was saturated into the experimental shale sample under a pressure of 10 MPa to obtain the oil-saturated experimental shale sample.

[0074] In one possible design, step (3) involves dividing the T2-T1 two-dimensional NMR spectrum of the saturated oil sample into a free oil region and an adsorbed miscible oil region, including:

[0075] Based on the differences in hydrogen signals of oil molecules in different occurrence states in the T2-T1 two-dimensional NMR spectra of saturated oil samples, the critical relaxation time of free oil and critical relaxation time of adsorbed miscible oil in the T2-T1 two-dimensional NMR spectra of saturated oil samples were determined.

[0076] Based on the critical relaxation time of the free oil and the critical relaxation time of the adsorbed miscible oil in the saturated oil sample, the T2-T1 two-dimensional NMR spectrum of the saturated oil sample is divided into a free oil region and an adsorbed miscible oil region.

[0077] It should be noted that in the T2-T1 two-dimensional NMR spectrum, there are... 1 Organic matter containing H, such as kerogen, has a high T1. T2 is similar to that containing... 1 The viscosity and fluidity of H compounds are positively correlated; that is, the higher the T2 value, the lower the viscosity and the better the fluidity. Therefore, oil molecules in different states also have different hydrogen nucleus component signals in the two-dimensional spectrum, that is, the T2 value of free oil is higher than that of adsorbed miscible oil.

[0078] It should be noted that in the T2-T1 two-dimensional NMR spectrum, the signals of kerogen and oils in different occurrence states can be effectively distinguished. Furthermore, the focus of this invention is on the utilization of shale oils in different occurrence states by the percolation process. Therefore, except for the T2-T1 two-dimensional NMR spectrum of unsaturated oil samples which contains the signal of kerogen, the signals of kerogen are no longer considered in the other T2-T1 two-dimensional NMR spectra. This processing method does not affect the experimental results.

[0079] Preferably, dividing the T2-T1 two-dimensional NMR spectrum of the saturated oil sample into a free oil region and an adsorbed miscible oil region includes, in the T2 dimension of the T2-T1 two-dimensional NMR spectrum of the saturated oil sample, the T2 value at which the hydrogen signal begins to appear is the T value of the adsorbed miscible oil. 2-min The first trough value corresponds to the T2 value of the adsorbed miscible oil T. 2-max T and free oil 2-min The T2 value at the end of the hydrogen signal is the T value of the free oil. 2-max ;

[0080] In the T1 dimension of the T2-T1 two-dimensional NMR spectrum of a saturated oil sample, the T1 value at which the hydrogen signal begins to appear is the T1 value of the free oil. 1-min The T1 value at the end of the hydrogen signal is the T value of the free oil. 1-max ;

[0081] T adsorbed miscible oil 1-max It is determined based on the time when the hydrogen signal in the adsorbed miscible oil region divided from the T2 dimension ends in the T1 dimension.

[0082] T of free oil 1-min Then, the T1 / T2 = 1 line and the adsorbed miscible oil T 2-max The point is determined by the intersection of the perpendicular lines.

[0083] Based on the T2 and T1 critical values ​​defined above, the relaxation intervals of the free oil region and the adsorbed miscible oil region can be delineated in the T2-T1 two-dimensional NMR spectrum of the saturated oil sample, thus dividing it into the free oil region and the adsorbed miscible oil region.

[0084] Preferably, the peak areas of hydrogen signals in the free oil region and the adsorbed miscible oil region in the NMR spectrum are obtained by re-inverting the critical relaxation time of the free oil and the critical relaxation time of the adsorbed miscible oil in the hydrogen nuclear component settings of the "Niumag NMR Data Analysis Software".

[0085] In one possible design, step (4) involves dividing the T2-T1 two-dimensional NMR spectrum of the unsaturated oil sample into a free oil region and an adsorbed miscible oil region, including:

[0086] Based on the critical relaxation time of the free oil and the critical relaxation time of the adsorbed miscible oil in the T2-T1 two-dimensional NMR spectrum of the saturated oil sample, the T2-T1 two-dimensional NMR spectrum of the unsaturated oil sample is divided into a free oil region and an adsorbed miscible oil region.

[0087] Preferably, spontaneous osmosis in step (5) is atmospheric pressure osmosis.

[0088] In one possible design, step (6) involves dividing the T2-T1 two-dimensional NMR spectrum after percolation into a free oil region and an adsorbed miscible oil region, including:

[0089] Based on the critical relaxation time of the free oil and the critical relaxation time of the adsorbed miscible oil in the T2-T1 two-dimensional NMR spectrum of the saturated oil sample, the T2-T1 two-dimensional NMR spectrum after percolation is divided into a free oil region and an adsorbed miscible oil region.

[0090] In one possible design, the experimental shale samples contain shale oil in different occurrence states, including free oil and adsorbed miscible oil.

[0091] In one possible design, the peak area of ​​hydrogen signals from shale oil in different occurrence states in the T2-T1 two-dimensional NMR spectrum of an unsaturated oil sample is denoted as S. o S o For S oa and S of The sum of;

[0092] The peak area of ​​hydrogen signal in shale oil at different occurrence states in the T2-T1 two-dimensional NMR spectrum of saturated oil samples is denoted as S. t S t For S ta and S tf The sum of;

[0093] The peak areas of hydrogen signals from shale oil in different occurrence states in the T2-T1 two-dimensional NMR spectra of the experimental shale samples after infiltration are denoted as S. t-i S t-i For S ta-i and S tf-i The sum of , where i is the number of osmosis.

[0094] In one possible design, the expression for the utilization rate of free oil in the experimental shale sample by the infiltration process is:

[0095]

[0096] In the formula, η tfi S represents the utilization rate of free oil in the experimental shale sample after the i-th infiltration, where i is a positive integer ≥ 1; tf S represents the peak area of ​​the hydrogen signal in the free oil region of the T2-T1 two-dimensional NMR spectrum of a saturated oil sample; of S represents the peak area of ​​the hydrogen signal in the free oil region of the T2-T1 two-dimensional NMR spectrum of an unsaturated oil sample; tfi The peak area of ​​the hydrogen signal in the free oil region in the T2-T1 two-dimensional NMR spectrum of the experimental shale sample after the i-th infiltration is denoted as .

[0097] In one possible design, the expression for the utilization rate of adsorbed miscible oil in the experimental shale sample during the infiltration process is:

[0098]

[0099] In the formula, η tai S represents the utilization rate of adsorbed miscible oil in the experimental shale sample after the i-th infiltration, where i is a positive integer ≥ 1; ta S is denoted by the peak area of ​​the hydrogen signal in the adsorbed miscible oil region in the T2-T1 two-dimensional NMR spectrum of the saturated oil sample; oa S represents the peak area of ​​hydrogen signals in the adsorbed miscible oil region in the T2-T1 two-dimensional NMR spectrum of an unsaturated oil sample; tai The peak area of ​​hydrogen signal in the adsorbed miscible oil region in the T2-T1 two-dimensional NMR spectrum of the experimental shale sample after the i-th infiltration is denoted as .

[0100] In one possible design, the expression for the total utilization rate of shale oil under different occurrence states during the infiltration process is:

[0101]

[0102] In the formula, η ti S represents the total utilization rate of shale oil in different occurrence states in the experimental shale sample after the i-th infiltration, where i is a positive integer ≥ 1; t The peak areas of hydrogen signals in shale oil under different occurrence states are shown in the T2-T1 two-dimensional NMR spectra of saturated oil samples; S o The peak areas of hydrogen signals in shale oil at different occurrence states are shown in the T2-T1 two-dimensional NMR spectra of unsaturated oil samples; S ti The peak areas of the oil and hydrogen signals in the T2-T1 two-dimensional NMR spectra of the experimental shale sample after the i-th infiltration are the peak areas of the shale oil and hydrogen signals in different occurrence states.

[0103] On the other hand, the present invention also discloses the application of the above method in reservoir numerical simulation and actual development.

[0104] It is understandable that, during the development process, how to specifically improve the development level of adsorbed miscible oil, i.e., the utilization rate, is of great significance for increasing shale oil production. The method of this invention can obtain conditions for increasing the production of adsorbed miscible oil, such as the number of adsorption cycles and adsorption time, providing important parameters for reservoir numerical simulation and actual development.

[0105] All of the above-mentioned optional technical solutions can be combined in any way to form the optional embodiments disclosed in this invention, and will not be described in detail here.

[0106] The present invention will be further described below through specific embodiments.

[0107] Unless otherwise specified, the experimental methods used in the following specific embodiments are conventional methods.

[0108] Unless otherwise specified, all operations described in the following specific embodiments are performed under standard conditions or conditions recommended by the manufacturer. Raw materials whose manufacturers and specifications are not specified are all commercially available products.

[0109] The shale samples used in the examples were all taken from the Chang 7 section of the southern Hubei region.

[0110] Example 1

[0111] A method for evaluating the utilization rate of shale oil in different occurrence states using two-dimensional nuclear magnetic resonance (NMR) includes the following steps:

[0112] (a) Select unsaturated oil experimental shale samples and prepare them into granular experimental shale samples A with a diameter of 3-5 mm. After thorough cleaning, drying, and weighing, the mass is recorded as m. a The dried sample A was placed in the MacroMR nuclear magnetic resonance analysis and imaging system for nuclear magnetic resonance analysis. Two-dimensional relaxation time NMR data of the unsaturated oil sample (transverse relaxation time T2 - longitudinal relaxation time T1) were obtained. The T2-T1 two-dimensional relaxation time NMR data of the unsaturated oil sample were then inverted to obtain the T2-T1 two-dimensional NMR spectrum of the unsaturated oil sample, as shown below. Figure 1 As shown.

[0113] (b) Place sample A in a sealed container, and use a vacuum pump to evacuate sample A and the sealed container to a vacuum level of 0.1 Pa. Set a saturation pressure of 10 MPa, and inject simulated oil dodecane into the sealed container. Remove the fully oil-saturated sample A, wipe the oil off the surface, and weigh it. Record the mass as m. a-0 The sample A in saturated oil was subjected to nuclear magnetic resonance analysis and testing using a MacroMR nuclear magnetic resonance analysis and imaging system, and the two-dimensional relaxation time NMR spectrum from T2 to T1 was obtained, as shown below. Figure 2 As shown, to avoid the influence of kerogen signals on the signal intensity of shale oil under different occurrence states, in Figure 2 In subsequent figures, only the NMR signals of shale oil in different occurrence states are shown.

[0114] (c) in Figure 2 In the diagram, the upper one-dimensional curve represents the signal intensity variation of shale oil in different occurrence states in the T2 dimension, while the right one-dimensional curve represents the signal intensity variation of shale oil in different occurrence states in the T1 dimension.

[0115] In the T2 dimension of the T2-T1 two-dimensional NMR spectrum of saturated oil sample A, the T2 value at which the hydrogen signal begins to appear is the T value of the adsorbed miscible oil. 2-minThe first trough value corresponds to the T2 value of the adsorbed miscible oil T. 2-max T and free oil 2-min The T2 value at the end of the hydrogen signal is the T value of the free oil. 2-max In the T1 dimension of the T2-T1 two-dimensional NMR spectrum of saturated oil sample A, the T1 value at which the hydrogen signal begins to appear is the T1 value of the free oil. 1-min The T1 value at the end of the hydrogen signal is the T value of the free oil. 1-max T adsorbed miscible oil 1-max The T1 time of the free oil is determined based on the end time of the hydrogen signal in the adsorbed miscible oil region defined by the T2 dimension in the T1 dimension. 1-min Then, the T1 / T2 = 1 line and the adsorbed miscible oil T 2-max The critical relaxation time of the free oil and the critical relaxation time of the adsorbed miscible oil in the saturated oil sample are determined by the intersection of the vertical lines at the point of intersection.

[0116] Based on the T2 and T1 critical values ​​defined above, as shown in Table 1, the relaxation intervals of the free oil region and the adsorbed miscible oil region can be delineated in the T2-T1 two-dimensional NMR spectrum of saturated oil sample A, respectively. The aforementioned T... 2-min T 2-max T 1-min and T 1-max The values ​​were input into the hydrogen nucleus composition settings of the "Niumag NMR Data Analysis Software" for data processing to obtain the peak area S of the hydrogen signal in the free oil region of saturated oil sample A. tf The peak area S of the hydrogen signal in the adsorbed miscible oil region ta The peak area of ​​hydrogen signals in shale oil under different occurrence states is S t The data is then recorded in Table 2.

[0117] Table 1. Critical relaxation times of NMR for different hydrogen nuclei in sample A.

[0118]

[0119] (d) Based on the critical relaxation times—T2 and T1—of the free oil and adsorbed miscible oil of the saturated oil sample A obtained in step (c), the T2-T1 two-dimensional NMR spectrum of the unsaturated oil sample A is divided into the free oil region and the adsorbed miscible oil region.

[0120] Because the pores in saturated oil samples are completely occupied by fluid, and the flow within the pores is single-phase, it is easy to distinguish the differences in fluid flow within the pores. That is, shale oil in different occurrence states exhibits different relaxation ranges in the two-dimensional NMR spectrum. Saturated oil samples contain... 1The presence of H in the fluid results in a higher signal-to-noise ratio (SNR) for H after NMR testing compared to unsaturated oil samples. This is more advantageous for delineating relaxation regions in two-dimensional NMR spectra, and because unsaturated oil samples contain H... 1 The amount of H fluid is relatively small, so nuclear magnetic resonance (NMR) testing cannot analyze the content of H in unsaturated oil samples. 1 The occurrence state of H fluid.

[0121] The peak area of ​​the hydrogen signal in the adsorbed miscible oil region of the unsaturated oil sample is calculated and denoted as S. oa The peak area of ​​the hydrogen signal in the free oil region is denoted as S. of The data is then recorded in Table 2.

[0122] (e) After saturating with oil, sample A was immersed in heavy water for spontaneous percolation at atmospheric pressure for 2 hours, followed by weighing and nuclear magnetic resonance analysis. The mass was denoted as m. a-1 Two-dimensional relaxation time NMR data of sample A after the first percolation were obtained. After inversion using "Niumag NMRData Analysis Software", the T2-T1 two-dimensional NMR spectrum of sample A after the first percolation was obtained, as shown below. Figure 3 As shown in (a);

[0123] (f) Based on the critical relaxation times—T2 and T1—of the free oil and adsorbed miscible oil obtained in step (c), the T2-T1 two-dimensional NMR spectrum of sample A after the first percolation is divided into the free oil region and the adsorbed miscible oil region.

[0124] Calculate the peak area S of the hydrogen signal in the free oil region of sample A after the first percolation. tf-1 The peak area S of the hydrogen signal in the adsorbed miscible oil region of sample A after the first percolation. ta-1 The peak area of ​​hydrogen signals in shale oil under different occurrence states is S t-1 The data is then recorded in Table 2.

[0125] (g) Repeat steps (e)-(f) of the percolation process, immersing sample A in heavy water multiple times for spontaneous percolation at atmospheric pressure. Weigh sample A after the second, third, fourth, and fifth percolations at different cumulative percolation times, and record the mass as m. a-2 m a-3 m a-4 m a-5 After each percolation, the nuclear magnetic resonance (NMR) analysis of sample A was performed to obtain the corresponding two-dimensional relaxation time NMR data. The T2-T1 two-dimensional NMR spectra of sample A after each percolation were then retrieved using "Niumag NMR Data Analysis Software," as shown below. Figure 3 (b) Figure 3 (c) Figure 3 (d) and Figure 3 As shown in (e);

[0126] Based on the critical relaxation times—T2 and T1—of the free oil and adsorbed miscible oil obtained in step (c), the T2-T1 two-dimensional NMR spectrum after each percolation is divided into the free oil region and the adsorbed miscible oil region.

[0127] Calculate the peak area S of the adsorbed miscible oil hydrogen signal of sample A under different percolation cycles. ta-i Peak area S of free oil-hydrogen signal tf-i and the peak area S of hydrogen signals in shale oil under different occurrence states t-i , where i is the number of absorptions, and the data are recorded in Table 2.

[0128] Table 2. Peak area and proportion of hydrogen oil signals in shale samples A under different occurrence states at different infiltration times.

[0129]

[0130] (h) Calculate the mobilization rates of free oil, adsorbed miscible oil, and total mobilization rate of shale oil in sample A for each percolation cycle according to the following expressions, as shown in Table 3. The extraction rates of free oil, adsorbed miscible oil, and total extraction rate vary with the extraction cycle as follows: Figure 4 As shown.

[0131] The expression for the utilization rate of free oil in the experimental shale sample due to the infiltration process is as follows:

[0132]

[0133] In the formula, η tf-i S represents the utilization rate of free oil in experimental shale sample A after the i-th infiltration, where i is a positive integer ≥ 1; tf S represents the peak area of ​​the hydrogen signal in the free oil region of saturated oil shale sample A. of S represents the peak area of ​​the free-state oil hydrogen signal in experimental shale sample A, which contains unsaturated oil; tf-i denoted as the peak area of ​​the free oil-hydrogen signal in shale sample A after the i-th infiltration.

[0134] The expression for the utilization rate of adsorbed miscible oil in the experimental shale sample during the infiltration process is as follows:

[0135]

[0136] In the formula, η ta-i S represents the utilization rate of adsorbed miscible oil in shale sample A after the i-th infiltration, where i is a positive integer ≥ 1; taS represents the peak area of ​​the adsorbed miscible oil hydrogen signal in saturated oil shale sample A. oa S represents the peak area of ​​the adsorbed miscible oil hydrogen signal in experimental shale sample A, which contains unsaturated oil; ta-i denoted as the peak area of ​​the adsorbed miscible oil-hydrogen signal in shale sample A after the i-th infiltration.

[0137] The expression for the utilization rate of shale oil in different occurrence states during the infiltration process is as follows:

[0138]

[0139] In the formula, η t-i S represents the total utilization rate of shale oil in different occurrence states in experimental shale sample A after the i-th infiltration, where i is a positive integer ≥ 1; t S represents the peak area of ​​hydrogen signals in shale oil under different occurrence states in experimental shale sample A, which is saturated with oil; o S represents the peak area of ​​hydrogen signals in shale oil under different occurrence states in experimental shale sample A, representing unsaturated oil. t-i denoted as the peak area of ​​the shale oil-hydrogen signal in different occurrence states of experimental shale sample A after the i-th infiltration.

[0140] Table 3. Utilization rates of adsorbed miscible oil, free oil, and shale oil in different occurrence states in experimental shale sample A.

[0141]

[0142] Comparative experiment: The total utilization rate of shale oil in different occurrence states in experimental shale sample A before and after infiltration was calculated using the mass method.

[0143] The mass m of sample A in unsaturated oil was recorded. o The mass m after saturation of oil a0 and the mass m after each percolation cycle a-i The utilization rates of shale oil in different occurrence states in the permeable shale experimental sample A, as measured by the mass method, are shown in Table 4.

[0144] The expression for calculating the total mobilization rate using the quality method is:

[0145]

[0146] In the formula, R i The total utilization rate (%) of shale oil in sample A under different occurrence states after each infiltration, calculated by the mass method; m a-0 The mass increase of sample A after saturation with oil is expressed as g; m. a-i ρ represents the mass of sample A after each percolation, in grams. w The density of heavy water is 1.1056 g·cm³. -3ρ0 represents the density of simulated oil dodecane, 0.75 g·cm³. -3 V0, the volume of oil phase saturated in the rock sample, in cm³. 3 .

[0147] Table 4 Comparison of mass change and mobilization rate of sample A during the percolation process.

[0148]

[0149] Example 2

[0150] A method for evaluating the utilization rate of shale oil in different occurrence states using two-dimensional nuclear magnetic resonance (NMR) includes the following steps:

[0151] (a) Select unsaturated oil experimental shale samples and prepare them into granular experimental shale samples B with a diameter of 3-5 mm. After thorough cleaning, drying, and weighing, the mass is recorded as m. b The dried sample B was placed in the MacroMR nuclear magnetic resonance analysis and imaging system for nuclear magnetic resonance analysis. Two-dimensional relaxation time NMR data of the unsaturated oil sample (transverse relaxation time T2 - longitudinal relaxation time T1) were obtained. The T2-T1 two-dimensional relaxation time NMR data of the unsaturated oil sample were then inverted to obtain the T2-T1 two-dimensional NMR spectrum of the unsaturated oil sample, as shown below. Figure 5 As shown.

[0152] (b) Place sample B in a sealed container, and evacuate sample B and the sealed container using a vacuum pump to a vacuum level of 0.1 Pa. Set a saturation pressure of 10 MPa, and inject simulated oil dodecane into the sealed container. Remove the fully oil-saturated sample B, wipe the oil off the surface, and weigh it. Record the mass as m. b-0 The sample B in its saturated oil state was subjected to NMR analysis using a MacroMR NMR analysis and imaging system, yielding T2-T1 two-dimensional relaxation time NMR data. The T2-T1 two-dimensional relaxation time NMR data of sample B after oil saturation were then inverted to obtain the T2-T1 two-dimensional NMR spectrum of the saturated oil sample, as shown below. Figure 6 As shown. The critical relaxation time of the free oil and the critical relaxation time of the adsorbed miscible oil in sample B of the saturated oil sample were determined using the method of Example 1.

[0153] (c) Based on the critical relaxation times—T2 and T1—of the free and adsorbed miscible oils in saturated oil sample B determined above, as shown in Table 5, the T2-T1 two-dimensional NMR spectrum of sample B after saturation is divided, and the relaxation intervals of the free and adsorbed miscible oils in the T2-T1 two-dimensional NMR spectrum of sample B after saturation are defined. The T2-T1 two-dimensional NMR spectrum of sample B after saturation is then used to define the relaxation intervals of the free and adsorbed miscible oils. The T2-T1 values ​​obtained in step (b) are then used to define the relaxation intervals of the free and adsorbed miscible oils in the T2-T1 two-dimensional NMR spectrum of sample B after saturation. 2-min T 2-max T 1-min and T1-max The values ​​were input into the hydrogen nucleus composition settings of the "Niumag NMR Data Analysis Software" for data processing to obtain the peak area S of the hydrogen signal in the free oil region of sample B after saturation. tf The peak area S of the hydrogen signal in the adsorbed miscible oil region ta The peak area of ​​hydrogen signals in shale oil under different occurrence states is S t The data is recorded in Table 6.

[0154] Table 5 Critical relaxation times of NMR for different hydrogen nucleus components in sample B

[0155]

[0156] (d) Based on the critical relaxation times—T2 and T1—of the free oil and adsorbed miscible oil of the saturated oil sample B obtained in step (c), the T2-T1 two-dimensional NMR spectrum of the unsaturated oil sample B is divided into the free oil region and the adsorbed miscible oil region.

[0157] The peak area of ​​the hydrogen signal in the adsorbed miscible oil region of the unsaturated oil sample is calculated and denoted as S. oa The peak area of ​​the hydrogen signal in the free oil region is denoted as S. of The data is recorded in Table 6.

[0158] (e) After saturating with oil, sample B was immersed in heavy water for spontaneous percolation at atmospheric pressure for 4 hours, followed by weighing and nuclear magnetic resonance analysis. The mass was denoted as m. b-1 Two-dimensional relaxation time NMR data of sample B after the first percolation were obtained. After inversion using "Niumag NMRData Analysis Software", the T2-T1 two-dimensional NMR spectrum of sample B after the first percolation was obtained, as shown below. Figure 7 As shown in (a);

[0159] (f) Based on the critical relaxation times of free oil and adsorbed miscible oil obtained in step (c) – T2 and T1 critical values, the T2-T1 two-dimensional NMR spectrum after the first percolation is divided into the free oil region after the first percolation and the adsorbed miscible oil region after the first percolation.

[0160] Calculate the peak area S of the hydrogen signal in the free oil region of sample B after the first round of percolation. tf-1 The peak area S of the hydrogen signal in the adsorbed miscible oil region of sample B after the first round of percolation. ta-1 The peak area of ​​hydrogen signals in shale oil under different occurrence states is S t-1 The data is recorded in Table 6.

[0161] (g) Repeat steps (e)-(f) of the percolation process, immersing sample B in heavy water multiple times for spontaneous percolation at atmospheric pressure. Weigh sample B after the second, third, fourth, and fifth percolations at different cumulative percolation times, and record the mass as m. b-2 m b-3 m b-4 m b-5 After each percolation, the nuclear magnetic resonance (NMR) analysis of sample B was performed to obtain the corresponding two-dimensional relaxation time NMR data. The T2-T1 two-dimensional NMR spectra of sample B after each percolation were then retrieved using "Niumag NMR Data Analysis Software," as shown below. Figure 7 (b) Figure 7 (c) Figure 7 (d) and Figure 7 As shown in (e);

[0162] Based on the critical relaxation times—T2 and T1—of the free oil and adsorbed miscible oil obtained in step (c), the T2-T1 two-dimensional NMR spectra after each percolation are divided into free oil and adsorbed miscible oil regions. The peak area S of the hydrogen signal of the adsorbed miscible oil in sample B at different percolation times is calculated. ta-i Peak area S of free oil-hydrogen signal tf-i and the peak area S of hydrogen signals in shale oil under different occurrence states t-i , where i is the number of absorptions, and the data are recorded in Table 6.

[0163] Table 6. Peak area and proportion of hydrogen oil signals in shale oil samples B under different occurrence states at different infiltration times.

[0164]

[0165] (h) Calculate the utilization rates of free oil, adsorbed miscible oil and total utilization rate of shale oil in different occurrence states in sample B after each infiltration according to the expressions (1)(2)(3) provided in Example 1, as shown in Table 7.

[0166] Table 7. Utilization rates of adsorbed miscible oil, free oil, and shale oil in different occurrence states in experimental shale sample B.

[0167]

[0168] Comparative experiment: The utilization rate of shale oil in different occurrence states in experimental shale sample B before and after infiltration was calculated using the mass method.

[0169] The mass of sample B was recorded in unsaturated oil, after saturation oil, and after each percolation cycle, as shown in Table 8.

[0170] The utilization rate of shale oil in different occurrence states in experimental sample B before and after infiltration can be calculated using the expression (4) of the mobilization rate calculation by the mass method in Example 1, as shown in Table 8.

[0171] Table 8 Comparison of mass change and mobilization rate of sample B during the percolation process.

[0172]

[0173]

[0174] By organizing and plotting the above experimental results, we can obtain the trends of adsorbed miscible oil, free oil, and total oil content in samples A and B as the percolation time increases, as shown in the graphs. Figure 4 and Figure 8 As shown in the figure, the percolation process effectively utilizes free oil, and the total utilization rate is positively correlated with the percolation time; that is, the longer the percolation time, the higher the total utilization rate. When the percolation time is short, water preferentially displaces free oil, exposing some of it to particles and allowing some to enter smaller pores, thus increasing the content of adsorbed miscible oil. As the percolation time increases, free oil is significantly utilized under the percolation process, and the utilization rate gradually increases. However, adsorbed miscible oil is not significantly utilized, and its utilization rate is negative. This indicates that during the percolation process, the water does not effectively utilize the adsorbed miscible oil; instead, it converts some of the free oil into adsorbed miscible oil. The total utilization rate of the two core samples is only about 30%, while the utilization rate of free oil reaches over 50%. Therefore, for water injection development percolation processes, effectively utilizing adsorbed miscible oil will be key to improving shale oil recovery rates.

[0175] By comparing the utilization rate results of the experimental mass method, it can be seen that the total utilization rate calculated by this method is almost consistent with that calculated by the mass method in terms of its trend. The average deviation between the total utilization rate calculated by the mass method and that calculated by the method of this invention is only 2.16%, indicating that the method of this invention has high accuracy in quantitatively characterizing the shale oil utilization rate. Furthermore, the conventional mass method can only calculate the total oil utilization rate by weighing the sample, and cannot distinguish the utilization rate of free oil and adsorbed miscible oil. The method of this invention, by combining nuclear magnetic resonance (NMR) technology with percolation experiments, delineates the boundary between free oil and adsorbed miscible oil in the obtained two-dimensional NMR spectrum. This not only distinguishes between free oil and adsorbed miscible oil, but also quantitatively calculates the percentage content of both and accurately calculates their utilization rates. The method of this invention is accurate and feasible, and can provide important parameters and basis for reservoir numerical simulation and actual development.

[0176] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for evaluating the shale oil recovery rate under different occurrence states during the two-dimensional nuclear magnetic resonance process, characterized in that, The method includes the following steps: (1) Experimental shale samples of unsaturated oil were analyzed using nuclear magnetic resonance to obtain the unsaturated oil sample... T 2- T 1. Two-dimensional relaxation time NMR data, in which T 2 represents the lateral relaxation time. T 1 represents the longitudinal relaxation time for the unsaturated oil sample. T 2- T Unsaturated oil samples were obtained by inversion of two-dimensional relaxation time NMR data. T 2 - T 1 Two-dimensional NMR spectrum; (2) Experimental shale samples with saturated oil were analyzed using nuclear magnetic resonance to obtain the saturated oil sample... T 2- T 1 Two-dimensional relaxation time NMR data for the saturated oil sample T 2 - T 1 Saturated oil samples were obtained by inversion of two-dimensional relaxation time NMR data. T 2 - T 1 Two-dimensional NMR spectrum; (3) saturated oil sample T 2 - T 1 The two-dimensional NMR spectrum is divided into a free oil region and an adsorbed miscible oil region; The saturated oil sample T 2 - T 1 The peak area of ​​the hydrogen signal in the adsorbed miscible oil region in the two-dimensional NMR spectrum is denoted as The saturated oil sample T 2 - T 1 The peak area of ​​the hydrogen signal in the free oil region of the two-dimensional NMR spectrum is denoted as ; (4) The unsaturated oil sample T 2 - T 1 The two-dimensional NMR spectrum is divided into a free oil region and an adsorbed miscible oil region; The unsaturated oil sample T 2 - T 1 The peak area of ​​the hydrogen signal in the adsorbed miscible oil region in the two-dimensional NMR spectrum is denoted as The unsaturated oil sample T 2 - T 1 The peak area of ​​the hydrogen signal in the free oil region of the two-dimensional NMR spectrum is denoted as ; (5) The saturated oil experimental shale sample was immersed in heavy water to undergo spontaneous percolation, resulting in a percolated experimental shale sample. The percolated experimental shale sample was then analyzed using nuclear magnetic resonance to obtain the percolated... T 2- T 1 Two-dimensional relaxation time NMR data for the infiltration after T 2 - T 1 Inversion of two-dimensional relaxation time NMR data yields the post-osmotic pressure data. T 2 - T 1 Two-dimensional NMR spectrum; (6) The absorbed water T 2 - T 1 Two-dimensional NMR spectra are divided into free oil regions and adsorbed miscible oil regions; The experimental shale sample after the first infiltration T 2 - T 1 The peak area of ​​the hydrogen signal in the adsorbed miscible oil region in the two-dimensional NMR spectrum is denoted as The experimental shale sample after the first infiltration T 2 - T 1 The peak area of ​​the hydrogen signal in the free oil region of the two-dimensional NMR spectrum is denoted as ; (7) Repeat steps (5)-(6) to obtain the experimental shale samples after multiple infiltrations. T 2 - T 1 The peak area of ​​the hydrogen signal in the free oil region of the two-dimensional NMR spectrum is denoted as and the experimental shale samples after multiple infiltrations T 2 - T 1 The peak area of ​​the hydrogen signal in the adsorbed miscible oil region in the two-dimensional NMR spectrum is denoted as , where i is the number of absorptions; (8) The shale samples before and after infiltration and absorption T 2 - T 1 Peak area of ​​hydrogen signal in the free oil region of a two-dimensional NMR spectrum Peak area of ​​hydrogen signal in the adsorption miscible oil region The utilization rate of free oil and adsorbed miscible oil in the experimental shale sample can be calculated from the area change.

2. The method for evaluating the shale oil recovery rate under different occurrence states during the adsorption process using two-dimensional nuclear magnetic resonance as described in claim 1, characterized in that... In step (3), the saturated oil sample is... T 2 - T 1 The two-dimensional NMR spectrum is divided into a free oil region and an adsorbed miscible oil region, including: According to the saturated oil sample T 2 - T 1 The difference in hydrogen signal between oil molecules in different occurrence states in a two-dimensional NMR spectrum is used to determine the saturated oil sample. T 2 - T 1 Critical relaxation time of free oil and critical relaxation time of adsorbed miscible oil in two-dimensional NMR spectra; Based on the critical relaxation time of the free oil and the critical relaxation time of the adsorbed miscible oil in the saturated oil sample, the saturated oil sample... T 2 - T 1 The two-dimensional NMR spectrum is divided into a free oil region and an adsorbed miscible oil region.

3. The method for evaluating the shale oil recovery rate under different occurrence states during the adsorption process using two-dimensional nuclear magnetic resonance, as described in claim 2, is characterized in that... In step (4), the unsaturated oil sample is... T 2 - T 1 The two-dimensional NMR spectrum is divided into a free oil region and an adsorbed miscible oil region, including: According to the saturated oil sample T 2 - T 1 The critical relaxation time of the free oil and the critical relaxation time of the adsorbed miscible oil in the two-dimensional NMR spectrum are used to analyze the unsaturated oil sample. T 2 - T 1 The two-dimensional NMR spectrum is divided into a free oil region and an adsorbed miscible oil region.

4. The method for evaluating the shale oil recovery rate under different occurrence states during the adsorption process using two-dimensional nuclear magnetic resonance, as described in claim 2, is characterized in that... In step (6), the absorbed water is removed from the container. T 2 - T 1 The two-dimensional NMR spectrum is divided into a free oil region and an adsorbed miscible oil region, including: According to the saturated oil sample T 2 - T 1 The critical relaxation time of the free oil and the critical relaxation time of the adsorbed miscible oil in the two-dimensional NMR spectrum, after permeation... T 2 - T 1 The two-dimensional NMR spectrum is divided into a free oil region and an adsorbed miscible oil region.

5. The method for evaluating the shale oil recovery rate under different occurrence states during the adsorption process using two-dimensional nuclear magnetic resonance as described in claim 1, characterized in that... The experimental shale samples contained shale oil in different occurrence states, including free oil and adsorbed miscible oil.

6. The method for evaluating the shale oil recovery rate under different occurrence states during the adsorption process using two-dimensional nuclear magnetic resonance as described in claim 5, characterized in that... The unsaturated oil sample T 2 - T 1 The peak areas of hydrogen signals in shale oil under different occurrence states in a two-dimensional NMR spectrum are denoted as... , For the and the aforementioned The sum of; The saturated oil sample T 2 - T 1 The peak areas of hydrogen signals in shale oil under different occurrence states in a two-dimensional NMR spectrum are denoted as... , For the and the aforementioned The sum of; The experimental shale samples after infiltration T 2 - T 1 The peak areas of hydrogen signals in shale oil under different occurrence states in a two-dimensional NMR spectrum are denoted as... , For the and the aforementioned The sum of , where i is the number of osmosis.

7. The method for evaluating the shale oil recovery rate under different occurrence states during the adsorption process using two-dimensional nuclear magnetic resonance as described in claim 1, characterized in that... The expression for the utilization rate of free oil in the experimental shale sample due to the infiltration process is as follows: (1) ； In the formula, Let i be the utilization rate of free oil in the experimental shale sample after the i-th infiltration, where i is a positive integer ≥ 1; For saturated oil samples T 2 - T 1 Peak area of ​​hydrogen signal in the free oil region in a two-dimensional NMR spectrum; For unsaturated oil samples T 2 - T 1 Peak area of ​​hydrogen signal in the free oil region in a two-dimensional NMR spectrum; The experimental shale sample after the i-th infiltration. T 2 - T 1 Peak area of ​​hydrogen signal in the free oil region in a two-dimensional NMR spectrum.

8. The method for evaluating the shale oil recovery rate under different occurrence states during the percolation process using two-dimensional nuclear magnetic resonance as described in claim 1, characterized in that... The expression for the utilization rate of adsorbed miscible oil in the experimental shale sample during the infiltration process is as follows: (2)； In the formula, The utilization rate of adsorbed miscible oil in the experimental shale sample after the i-th infiltration is denoted as i, where i is a positive integer ≥ 1. For saturated oil samples T 2 - T 1 Peak area of ​​hydrogen signal in the adsorbed miscible oil region in a two-dimensional NMR spectrum; For unsaturated oil samples T 2 - T 1 Peak area of ​​hydrogen signal in the adsorbed miscible oil region in a two-dimensional NMR spectrum; For the experimental shale sample after the i-th infiltration... T 2 - T 1 Peak area of ​​hydrogen signal in the adsorbed miscible oil region in a two-dimensional NMR spectrum.

9. The method for evaluating the shale oil recovery rate under different occurrence states during the adsorption process using two-dimensional nuclear magnetic resonance as described in claim 6, characterized in that... The expression for the total utilization rate of shale oil under different occurrence states during the infiltration process is as follows: (3)； In the formula, Let i be the total utilization rate of shale oil in different occurrence states in the experimental shale sample after the i-th infiltration, where i is a positive integer ≥ 1; For saturated oil samples T 2 - T 1 Peak areas of hydrogen signals in shale oil under different occurrence states in two-dimensional NMR spectra; For unsaturated oil samples T 2 - T 1 Peak areas of hydrogen signals in shale oil under different occurrence states in two-dimensional NMR spectra; For the experimental shale sample after the i-th infiltration... T 2 - T 1 Peak areas of hydrogen signals in shale oil under different occurrence states in two-dimensional NMR spectra.

10. The application of the two-dimensional nuclear magnetic resonance method for evaluating the utilization rate of shale oil in different occurrence states of the seepage process as described in any one of claims 1-9 in reservoir numerical simulation and actual development.

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