A shale oil pyrolysis adsorbed oil and free oil correction method based on nuclear magnetic experiment
By combining nuclear magnetic resonance experiments and pyrolysis experiments, the problem of inaccurate calculation of adsorbed oil content in shale oil pyrolysis was solved, resulting in more accurate shale oil exploration results.
Patent Information
- Application Number
- CN202511146083.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-15
- Publication Date
- 2025-11-21
- Estimated Expiration
- 2045-08-15
AI Technical Summary
In existing technologies, insufficient division of rock pyrolysis heating temperature steps in shale oil pyrolysis experiments leads to errors in the calculation of free oil and adsorbed oil content. Furthermore, the traditional Rock-Eval6 instrument suffers from inaccurate calculations due to its small sample size.
A multi-state nuclear magnetic resonance experiment was used to construct an adsorbed oil evaluation model and correct the content of free oil and adsorbed oil by cutting the core, pre-processing, nuclear magnetic resonance measurement and pyrolysis experiment.
Precise calculation of adsorbed oil content compensates for the shortcomings of traditional methods, reduces calculation errors, and improves the accuracy of shale oil exploration.
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Figure CN120721782B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of unconventional oil and gas exploration technology, and in particular to a method for correcting adsorbed oil and free oil in shale oil pyrolysis based on nuclear magnetic resonance experiments. Background Technology
[0002] In recent years, shale oil and gas resources, with their enormous potential, have gradually become a research hotspot. As an unconventional oil and gas resource, shale exhibits significant compositional diversity, and can be classified into fluid and non-fluid components based on their occurrence properties. According to the research of Jiang Qigui et al., in shale pyrolysis experiments, hydrocarbons in shale can be divided into free hydrocarbons, adsorbed hydrocarbons, and cracked hydrocarbons based on their different pyrolysis release temperatures. Among these, free oil and adsorbed oil are among the main hydrocarbon components affecting reserves and are the primary targets in shale oil extraction. Therefore, accurate identification and quantitative calculation of adsorbed oil are crucial for shale oil exploration and development research.
[0003] In recent years, numerous methods have been proposed by domestic and international experts and scholars for calculating shale adsorbed oil. Among these, the experimental method is one of the main methods for shale oil adsorption. Previous researchers have explored various methods, such as rock pyrolysis, solvent extraction, adsorption experiments, and two-dimensional nuclear magnetic resonance, to calculate the content of free oil and adsorbed oil in shale. Specifically, Lu Shuangfang et al., using swelling and temperature-gradient pyrolysis experiments, based on the study of the control effect of maturity evolution on kerogen adsorption-swelling, and considering the influence of the surface area of clay pores containing adsorbed oil and formation temperature in shale samples, proposed a comprehensive shale adsorbed oil evaluation model by conducting swelling oil experiments on naturally evolved kerogen samples and adsorbed oil experiments on clay samples separated from mudstone and shale. However, this method also has obvious drawbacks. First, the temperature steps for rock pyrolysis are insufficient. This method uses 90℃, 300℃, 450℃, and 600℃ as temperature steps to determine gaseous hydrocarbons, free oil, adsorbed oil, and cracked non-hydrocarbon gases, respectively. It is generally believed that adsorbed oil precipitates at 300~450℃, but because some products precipitate before 300℃ during the heating process, and due to limitations in solvent extraction, parameters such as the free oil content and cracked hydrocarbon content obtained from pyrolysis may have errors, leading to an inflated free oil content. Second, the pyrolysis experiment based on the Rock-Eval6 instrument has obvious limitations. It can only conduct experiments with a small number of fragmented samples, resulting in inaccurate adsorbed oil and free oil content, leading to errors in the evaluation of different hydrocarbon contents. Further research is needed on methods for calculating and correcting adsorbed oil in this regard.
[0004] Therefore, there is an urgent need to study a laboratory method for calculating and correcting adsorbed oil and free oil in shale. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention discloses a method for correcting adsorbed and free oil in shale oil pyrolysis based on nuclear magnetic resonance experiments. This method solves the problem of inaccurate measurement of adsorbed oil content in shale reservoirs during rock pyrolysis through multi-state nuclear magnetic resonance experiments.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] A method for correcting adsorbed and free oil from shale oil pyrolysis based on nuclear magnetic resonance experiments includes the following steps:
[0008] s1. Cut the full-diameter core to obtain standard plunger samples and parallel fragment core samples, and pre-process them;
[0009] s2. Perform nuclear magnetic resonance experiments on standard plunger core samples at 200℃ with the original sample, oil-saturated sample, oil-washed sample, and 2D nuclear magnetic resonance T1-T2 spectra.
[0010] s3. Based on the location and content of adsorbed oil in the 2D NMR T1-T2 spectrum, an evaluation model for adsorbed oil is constructed.
[0011] s4. Conduct pyrolysis experiments at different temperature levels on parallel fragment core samples of the same mass to obtain the contents of free oil and adsorbed oil;
[0012] s5. Based on the pyrolysis experiment results, the free oil content S1 and adsorbed oil content S... 2-1 Perform corrections.
[0013] Optionally, in step s1, core samples from the study area are collected, and standard plunger samples are processed using wire cutting. Their length, diameter, and mass are measured. The remaining core samples after plunger processing are then crushed to 60 mesh using a core pulverizer. Subsequently, the same mass of crushed samples is taken out and heated in a vacuum environment at a heating rate of 20℃ / min. The products are collected at 300℃ and 450℃ as boundaries to obtain the free oil content S1 and the adsorbed oil content S2. 2-1 .
[0014] Optionally, in step s2, the nuclear magnetic resonance signal of the dry core sample is measured using a nuclear magnetic resonance spectrometer with parameters including: TE=0.06ms, TW=2000ms; NECH=32. The nuclear magnetic resonance spectrometer can measure the nuclear magnetic signals of substances including kerogen, structural water, bitumen, and hydrogen-containing substances with higher fluidity than bitumen. The 2D nuclear magnetic T1-T2 spectrum is obtained by inverting the measured signal.
[0015] Optionally, in step s2, the sample is evacuated for 4 hours, then saturated with aviation kerosene for 72 hours, pressurized to 35 MPa, and then the 2D NMR T1-T2 spectrum of the plunger sample saturated oil is measured. The sample is washed with a mixture of dichloromethane and acetone at 80°C and 0.2 MPa for 7 days. Subsequently, the sample is evacuated and dried at 110°C to fully remove residual oil from the shale pore system. The 2D NMR T1-T2 spectrum of the washed and dried shale is measured. The washed core is heated at 200°C for 10 hours, and after cooling, the 2D NMR T1-T2 spectrum is measured.
[0016] Optionally, in step s3, the NMR spectra of oil standards of different masses are measured to establish a linear conversion relationship between the standard signal intensity and the unit mass of oil. The location of adsorbed oil is determined by comparing NMR spectra at different states. Based on the linear conversion relationship, the adsorbed oil content per unit mass of laboratory NMR sample is determined. The correlation between the adsorbed oil content and the organic carbon content and clay mineral content is analyzed, forming the following correlation between the adsorbed oil content and both:
[0017] ;
[0018] In the formula, A is the adsorbed oil content per unit mass of laboratory nuclear magnetic resonance sample, TOC is the organic carbon content, CLAY is the clay mineral content, and a, b, and c are fitting parameters.
[0019] Optionally, in step s4, the broken sample is heated in a vacuum environment at a heating rate of 20℃ / min, and the product is collected at 300℃ and 450℃ as boundaries to obtain the free oil content S1 and the adsorbed oil content S2. 2-1 .
[0020] Optionally, in step s5, the contents of free oil and adsorbed oil obtained from rock pyrolysis are corrected based on the laboratory adsorbed oil content as follows:
[0021] ;
[0022] ;
[0023] In the formula, This is the corrected free oil content. It refers to the free oil content. It is the adsorbed oil content. This is the corrected adsorbed oil content.
[0024] The beneficial effect of this invention is that it addresses the limitations of existing pyrolysis calculations for S1 and S2. 2-1 Limited by incomplete solvent extraction, resulting in S1 and S 2-1To address the issue of inaccurate calculation results, this invention conducts 2D nuclear magnetic resonance (NMR) measurements using parallel plunger samples of the same mass. Utilizing the NMR method's ability to obtain all magnetic resonance signals reflecting oil and water and its ability to segment fluids, a conversion relationship between the NMR signal intensity and adsorbed oil content of the unpyrolyzed plunger core samples is established using standard samples. This compensates for the shortcomings of pyrolysis methods, accurately calculating the adsorbed oil content. Furthermore, a NMR-based adsorbed oil evaluation model is constructed by combining parameters related to organic carbon and clay minerals associated with the adsorbed oil, allowing for correction of the adsorbed and free oil content obtained from pyrolysis. Moreover, unlike traditional Rock-Eval6 pyrolysis experiments which use small, fragmented samples, this invention uses larger core samples, avoiding the inaccuracies in calculating adsorbed and free oil content caused by smaller sample sizes, as well as errors in evaluating different hydrocarbon contents. Attached Figure Description
[0025] Figure 1 This is a flowchart of a method for correcting adsorbed oil and free oil in shale oil pyrolysis based on nuclear magnetic resonance experiments according to the present invention.
[0026] Figure 2 The original sample NMR T1-T2 spectrum is shown in an embodiment of the present invention;
[0027] Figure 3 The T1-T2 NMR spectrum of saturated oil is shown in an embodiment of the present invention.
[0028] Figure 4 The above is a T1-T2 NMR spectrum of the wash oil, as shown in an embodiment of the present invention.
[0029] Figure 5 The T1-T2 NMR spectrum after washing oil and heating at 200°C is shown in one embodiment of the present invention.
[0030] Figure 6 This is a compositional diagram showing the location of adsorbed oil components according to an embodiment of the present invention;
[0031] Figure 7 This is a graph showing the correlation between the experimental adsorbed oil content and the calculated adsorbed oil content in an embodiment of the present invention. Detailed Implementation
[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0033] A method for correcting adsorbed and free oil in shale oil pyrolysis based on nuclear magnetic resonance experiments, such as... Figure 1 As shown, it includes the following steps:
[0034] S1. Shale samples were obtained by core sampling. Standard plunger samples were fabricated from the cores using wire cutting. The core dimensions used in this example were as follows: length 5cm, diameter 2.5cm, and mass 57g. The same mass of sample was pulverized into 60-mesh pieces using a high-speed pulverizer. The pulverized sample was then heated in a vacuum environment at a heating rate of 20℃ / min. The products were collected at 300℃ and 450℃ as boundaries to obtain the free oil content S1 and adsorbed oil content S2. 2-1。
[0035] s2. The nuclear magnetic resonance (NMR) signal of the core plunger sample in its original state was measured using a MesoMR23-060H-I type NMR spectrometer. The purpose of measuring the original 2D NMR T1-T2 spectrum of the sample was to measure the NMR signals of the remaining hydrogen-containing components in the sample, including kerogen, structural water, bitumen, and all components with higher fluidity than bitumen. Subsequently, the measured signals were inverted to obtain the NMR T2 spectrum, as shown below. Figure 2 As shown in the figure, the green, red, and blue lines are the scale lines for T1 / T2 being 1, 10, and 100, respectively. The main parameters are: TE=0.06ms, TW=2000ms; NECH=32.
[0036] The sample was then evacuated for 4 hours, saturated with aviation kerosene for 72 hours, and pressurized to 35 MPa. After removal, the two-dimensional nuclear magnetic resonance T1-T2 spectrum of the plunger sample saturated with oil was measured. Figure 3 As shown, the sample was treated with a mixture of dichloromethane and acetone at 80℃ and 0.2MPa for 7 days. Subsequently, the sample was vacuum-sealed and dried at 110℃ to thoroughly remove residual oil from the shale pore system. The T1-T2 spectra of the dried shale were then analyzed. Figure 4As shown, the core sample after oil washing was further heated at 200℃ for 10 hours. After cooling, a two-dimensional nuclear magnetic resonance (NMR) experiment was performed to measure the T1-T2 spectrum. Figure 5 As shown.
[0037] s3. By measuring the NMR spectra of oil standard samples of different masses, a linear conversion relationship between the signal intensity of the standard sample and the unit mass of oil is established, as shown in the following formula:
[0038] ;
[0039] In the formula, M S For a unit mass of oil, S NMR ρ represents the nuclear magnetic resonance signal of a core sample per unit porosity, and ρ represents the density of the oil.
[0040] Further comparison of NMR spectra of the original sample, saturated oil, washed oil, and post-washed oil heating clarified the location of the adsorbed oil, thus obtaining a fluid partition map of the adsorbed oil components, such as... Figure 6 As shown, by further utilizing the above conversion relationship, the signals of the adsorbed oil region are summed to obtain the corresponding laboratory nuclear magnetic resonance adsorbed oil mass.
[0041] By analyzing the correlation between adsorbed oil content and organic carbon content and clay mineral content using nuclear magnetic resonance (NMR), the following correlation was established between adsorbed oil content and both:
[0042] ;
[0043] In the formula, A is the adsorbed oil content per unit mass of laboratory nuclear magnetic resonance sample, TOC is the organic carbon content, and CLAY is the clay mineral content.
[0044] s4. Conduct a traditional pyrolysis experiment, heating the fragmented sample in a vacuum environment at a heating rate of 20℃ / min, and collecting the products at 300℃ and 450℃ as boundaries to obtain the free oil content S1 and adsorbed oil content S2. 2-1 The measurement results are as follows:
[0045] Table 1. Measurement results of free oil and adsorbed oil content
[0046]
[0047] s5. Using the laboratory adsorbed oil content as a benchmark, correct the free oil and adsorbed oil obtained from rock pyrolysis using the following formula, and compare the calculated adsorbed oil content with the experimentally measured adsorbed oil content. Figure 7 As shown, the relative error between the two is 12%.
[0048] ;
[0049] ;
[0050] In the formula, This is the corrected free oil content. It refers to the free oil content. It is the adsorbed oil content. This is the corrected adsorbed oil content.
[0051] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.
Claims
1. A shale oil pyrolysis adsorbed oil and free oil correction method based on a nuclear magnetic experiment, characterized in that, It comprises the following steps: S1, cutting the full-diameter core to obtain a standard plunger sample and a parallel broken sample core, and pre-treating; S2, performing a 2D nuclear magnetic T1-T2 spectrum test on the standard plunger sample core in the original state, oil saturation, oil washing, and 200 DEG C nuclear magnetic resonance experiment, and obtaining a 2D nuclear magnetic T1-T2 spectrum; S3, constructing an adsorbed oil evaluation model from the adsorbed oil position and content of the 2D nuclear magnetic T1-T2 spectrum; S4, performing pyrolysis experiments at different temperature stages on the same mass of parallel broken sample cores to obtain free oil and adsorbed oil content; s5, based on the pyrolysis experimental results, the free oil content S1, the adsorbed oil content S 2-1 correction is made; In step s1, the cores in the study area are collected, and the standard plunger sample is processed by wire cutting, and the length, diameter and mass of the standard plunger sample are measured. The remaining core after the plunger sample is processed is crushed to 60 mesh by a core crusher; In step s2, the nuclear magnetic resonance signal of the standard plunger sample is measured by a nuclear magnetic resonance instrument, and the parameters include: TE=0.06ms, TW=2000ms; NECH=32, the nuclear magnetic resonance instrument can measure the nuclear magnetic signal of the kerogen, structural water, asphalt and hydrogen-containing substances with higher flowability than asphalt; the 2D nuclear magnetic T1-T2 spectrum is obtained after inversion of the measured signal; Then, the standard plunger sample is vacuumed for 4 hours, then saturated with aviation kerosene for 72 hours, pressurized to 35 MPa, and the 2D nuclear magnetic T1-T2 spectrum of the saturated oil of the plunger sample is measured after being taken out; the standard plunger sample is treated with a mixture of dichloromethane and acetone at 80 DEG C and 0.2 MPa for 7 days; then, the standard plunger sample is vacuumed and dried at 110 DEG C to fully remove the residual oil in the shale pore system; the 2D nuclear magnetic T1-T2 spectrum of the oil-washed and dried shale is tested, and the oil-washed core is further heated at 200 DEG C for 10 hours, and the 2D nuclear magnetic T1-T2 spectrum is measured after cooling; In step s3, the nuclear magnetic spectrum of the oil standard sample of different mass is measured, the linear conversion relationship between the signal intensity of the standard sample and the unit mass of oil is established, the occurrence position of the adsorbed oil is judged according to the comparison of the nuclear magnetic spectrum in different states, the adsorbed oil content in the unit sample mass of the laboratory nuclear magnetic resonance is determined according to the linear conversion relationship, the correlation between the adsorbed oil content of the nuclear magnetic resonance and the organic carbon content and the clay mineral content is analyzed, and the correlation relationship between the adsorbed oil content and the two is formed as an adsorbed oil evaluation model: ； In the formula, A is the adsorbed oil content in the unit sample mass of the laboratory nuclear magnetic resonance, TOC is the organic carbon content, CLAY is the clay mineral content, and a, b and c are fitting parameters; In step s4, the crushed sample core is heated in a vacuum environment at a heating rate of 20°C / min, and the products are collected at 300°C and 450°C as boundaries to obtain the free oil content S1, the adsorbed oil content S2, and the total oil content S3. 2-1 ; In step s5, the free oil and adsorbed oil content obtained by rock pyrolysis is corrected based on the laboratory adsorbed oil content as follows: ； ； wherein is the corrected free oil content, is the free oil content, is the adsorbed oil content, is the corrected adsorbed oil content.