Method for establishing shale oil two-dimensional nuclear magnetic resonance fluid distribution chart
By combining full-diameter closed core two-dimensional nuclear magnetic resonance (NMR) measurements with fragmented sample multi-temperature-level oxygen-free heating and geochemical pyrolysis experiments, the problem of low accuracy in two-dimensional NMR fluid identification of shale oil in existing technologies has been solved. A simplified fluid component identification method has been realized, which is suitable for the establishment of two-dimensional NMR fluid distribution maps for shale oil.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA NAT PETROLEUM CORP
- Filing Date
- 2022-09-20
- Publication Date
- 2026-06-02
AI Technical Summary
The lack of standardized methods in the current technology to establish accurate two-dimensional nuclear magnetic resonance fluid identification charts for shale oil results in low fluid identification accuracy. Furthermore, existing methods involve complex sample preparation and long experimental cycles, and cannot fully reflect the specific fluid distribution characteristics of a region.
By combining two-dimensional nuclear magnetic resonance (NMR) measurements of full-diameter sealed cores, multi-temperature-level oxygen-free heating of fragmented samples, and geochemical pyrolysis experiments, the composition of two-dimensional NMR fluids in shale oil was identified and fluid distribution maps were drawn by comparing changes in NMR spectral signals and hydrocarbon content.
It provides a more sufficient theoretical basis, ensures the accuracy of fluid component identification, simplifies the process flow, improves operability and timeliness, and facilitates field application.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of shale oil and gas exploration and development technology, and relates to a method for establishing a two-dimensional nuclear magnetic resonance fluid distribution map of shale oil. Background Technology
[0002] Parameters such as shale organic matter abundance, pore fluid properties, and mobile hydrocarbon content are key parameters for shale reservoir evaluation, directly affecting the reservoir's development potential and development strategies. Accurately characterizing these parameters is currently a challenge and a critical issue in shale oil evaluation. Nuclear magnetic resonance (NMR) has advantages in hydrocarbon component classification, pore structure measurement, and fluid occurrence characterization, and has been increasingly used in recent years for fluid identification and quantitative calculation of oil content in low-porosity and low-permeability reservoirs such as shale. Medium- and high-frequency two-dimensional NMR can intuitively and rapidly classify kerogen and pore fluids and perform quantitative calculations. The experimental process has advantages such as speed, non-destructive nature, and quantitative analysis. Furthermore, with the widespread application of downhole two-dimensional NMR, the need for laboratory data calibration and standardization is increasing, leading to a growing demand for two-dimensional NMR experiments.
[0003] Due to the diverse types of shale oil reservoirs and the varying 2D NMR response characteristics of core samples from different regions, the identification and classification of reservoir components requires tailored approaches to ensure accurate fluid identification. Currently, there is no standardized method or procedure for establishing accurate regional 2D NMR fluid identification maps. Two main approaches exist: The first approach involves performing low-field, high-frequency 2D NMR measurements on kerogen, extracted dry shale, and clay minerals in their original, saturated oil-water, and centrifuged states. A 2D NMR component map is then established based on the response positions on the NMR spectrum. This method is complex to prepare samples and has a long experimental cycle, making it suitable only for scientific research. Furthermore, the composition of saturated oil-water samples is often inconsistent with that of in-situ fluids, failing to fully reflect the specific fluid distribution characteristics of a region. The second approach utilizes high-frequency 2D NMR technology to analyze organic-rich shale samples after extraction with polar organic solvents. However, this method cannot distinguish between free and adsorbed oil and gas, resulting in fewer component categories. Because shale oil reservoirs are diverse and the two-dimensional nuclear magnetic resonance response characteristics of cores vary from region to region, it is necessary to establish targeted identification and classification charts for reservoir components in order to ensure the accuracy of fluid identification. Summary of the Invention
[0004] The purpose of this invention is to solve the problems in the prior art and provide a method for establishing a two-dimensional nuclear magnetic resonance fluid distribution map of shale oil. Based on the two-dimensional nuclear magnetic resonance response characteristics of the core, the method can specifically identify reservoir components and divide the map, ensuring the accuracy of fluid component identification.
[0005] To achieve the above objectives, the present invention employs the following technical solution:
[0006] A method for establishing a two-dimensional nuclear magnetic resonance fluid distribution map of shale oil includes the following steps:
[0007] Two-dimensional nuclear magnetic resonance measurements were performed on a full-diameter sealed rock core.
[0008] Samples were taken from a full-diameter sealed core, ground into fragments, and two-dimensional nuclear magnetic resonance measurements were performed on the original fragments.
[0009] A portion of the fragmented original sample was heated at several temperature levels in an oxygen-free environment, and after cooling, two-dimensional nuclear magnetic resonance measurements were performed.
[0010] A portion of the original fragmented sample and a portion of the fragmented sample heated in an oxygen-free environment were subjected to several temperature-level geochemical pyrolysis experiments to determine the hydrocarbon content.
[0011] By comparing the signal changes in the two-dimensional nuclear magnetic resonance (NMR) spectra of full-diameter sealed cores and original fragments, comparing the signal changes in the two-dimensional NMR spectra of fragments before and after oxygen-free heating at different temperature levels, and comparing the changes in hydrocarbon content before and after geochemical pyrolysis experiments at different temperature levels, the components of two-dimensional NMR fluids in shale oil were identified, and a two-dimensional NMR fluid distribution map of shale oil was drawn.
[0012] Furthermore, when performing two-dimensional nuclear magnetic resonance measurements on a full-diameter sealed core, the measurement frequency was 12.5 MHz and the echo interval was 0.2 ms, and the two-dimensional nuclear magnetic resonance T1-T2 spectrum was measured.
[0013] Furthermore, the particle size of the original fragmented sample is 80 mesh.
[0014] Furthermore, when performing two-dimensional nuclear magnetic resonance measurements on the original fragmented sample, the measurement frequency was 21 MHz and the echo interval was 0.1 ms, and the two-dimensional nuclear magnetic resonance T1-T2 spectrum was measured.
[0015] Furthermore, the changes in hydrocarbon content before and after the geochemical pyrolysis experiment were measured using the YQ-VIIIA oil and gas display evaluation instrument.
[0016] Furthermore, the measurement frequency for two-dimensional nuclear magnetic resonance (NMR) measurements after oxygen-free heating and cooling was 21 MHz, the echo interval was 0.1 ms, and the two-dimensional NMR T1-T2 spectrum was measured.
[0017] Furthermore, the temperature values of the temperature steps are determined by the clay type, pyrolysis peak temperature, and crude oil properties of the regional reservoir, with the number of fragmented samples and the corresponding temperature step number being 4 to 6.
[0018] Furthermore, in the geochemical pyrolysis experiment, the original fragmented sample and the fragmented sample heated under anaerobic conditions had the same mass.
[0019] Furthermore, the oxygen-free heating method is direct heating, with a heating rate of 50℃ / min, and each temperature step is held constant for 1-2 minutes.
[0020] Furthermore, the geochemical pyrolysis experiment used a continuous heating method with a heating rate of 50℃ / min.
[0021] Compared with the prior art, the present invention has the following beneficial effects:
[0022] This invention provides a method for establishing a two-dimensional nuclear magnetic resonance (NMR) fluid distribution map of shale oil. It utilizes a combination of two-dimensional NMR experiments with full-diameter sealed cores, two-dimensional NMR experiments of fragmented samples before and after multi-temperature-level oxygen-free heating, and multi-temperature-level geochemical pyrolysis experiments to measure the diffusion sequence of components in different occurrence states in the NMR T1-T2 spectrum. These two methods mutually verify each other, providing a more sufficient theoretical basis for fluid component identification and a more comprehensive determination of components. This provides a feasible experimental scheme and analytical method for two-dimensional NMR fluid identification in shale oil and provides important evidence for further calibration of downhole two-dimensional NMR saturation processing results. The method and measurement process of this invention are simple, highly operable, and timely, facilitating field application. Attached Figure Description
[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0024] Figure 1 This is a flowchart of the technical process of Embodiment 1 of the present invention.
[0025] Figure 2 This is a two-dimensional nuclear magnetic resonance spectrum of a full-diameter sealed core from Example 1 of the present invention.
[0026] Figure 3 The graph shows the detection results of hydrocarbon signals in the geochemical pyrolysis experiments of the original fragmented sample and the sample heated at different temperature levels in Example 1 of the present invention.
[0027] Figure 4 These are two-dimensional nuclear magnetic resonance spectra of the original fragmented sample and the sample after heating at different temperature levels in Example 1 of the present invention.
[0028] Figure 5 The two-dimensional nuclear magnetic resonance fluid distribution map layout established for Embodiment 1 of the present invention.
[0029] Wherein: 4(a) - NMR spectrum of the original fragment sample, 4(b) - NMR spectrum of the original sample after heating to 80℃, 4(c) - NMR spectrum of the original sample after heating to 200℃, 4(d) - NMR spectrum of the original sample after heating to 350℃, 4(e) - NMR spectrum of the original sample after heating to 450℃, 4(f) - NMR spectrum of the original sample after heating to 600℃. Detailed Implementation
[0030] 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 some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.
[0031] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.
[0032] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.
[0033] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0034] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.
[0035] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.
[0036] The present invention will now be described in further detail with reference to the accompanying drawings:
[0037] This invention provides a method for establishing a two-dimensional nuclear magnetic resonance fluid distribution map of shale oil, comprising the following steps:
[0038] Fresh, full-diameter sealed cores, sealed with wax and plastic wrap, were subjected to laboratory two-dimensional nuclear magnetic resonance T1-T2 measurements at a frequency of 12.5 MHz and an echo interval of 0.2 ms.
[0039] Samples were taken from the full-diameter sealed core and ground into m+1 80-mesh original samples. Two-dimensional nuclear magnetic resonance T1-T2 measurements were performed on the original state of the original samples and after direct heating at m temperature levels in an oxygen-free environment. The measurement frequency was 21MHz, the echo interval was 0.1ms, the heating rate in an oxygen-free environment was 50℃ / min, and each temperature level was held at a constant temperature for 1-2min.
[0040] Samples of equal mass were taken from both the original fragmented sample and the fragmented sample after oxygen heating and subjected to a geochemical pyrolysis experiment with continuous heating at m temperature levels. The heating rate was 50℃ / min. The hydrocarbon content in the fragmented sample before and after the geochemical pyrolysis experiment was detected by the YQ-VIIIA oil and gas display evaluation instrument.
[0041] Comparative analysis of signal changes in the two-dimensional nuclear magnetic resonance T1-T2 spectra of full-diameter sealed cores and fragmented original samples;
[0042] Compare the two-dimensional nuclear magnetic resonance T1-T2 spectral characteristics of the original fragmented sample and the fragmented sample after oxygen-free heating;
[0043] Compare the hydrocarbon detection results before and after the multi-temperature-step geochemical pyrolysis experiment;
[0044] Based on the comparison results, the two-dimensional nuclear magnetic resonance (NMR) T1-T2 spectrum signals of the full-diameter sealed core can basically reflect the fluid occurrence state in its original state. Compared with the original fragmented sample's two-dimensional NMR T1-T2 spectrum, grinding the sample into fragments results in the loss of most of the movable fluid. The signal loss in the original fragmented sample's NMR spectrum can reflect the location of movable and bound oil. By comparing the disappearance and appearance of the two-dimensional NMR signals of the original fragmented sample and after oxygen-free heating at different temperature levels with the hydrocarbon signals precipitated before and after geochemical pyrolysis experiments at different temperature levels, and considering the clay type, pyrolysis peak temperature, and crude oil properties in the core of the regional reservoir, the distribution of various components and fluids on the two-dimensional NMR T1-T2 spectrum is determined. The distribution positions of capillary bound water, movable water, clay-bound water, hard organic matter, and kerogen on the two-dimensional NMR spectrum are determined, thus obtaining a two-dimensional NMR fluid distribution map.
[0045] Furthermore, the specific values for each temperature level are determined by the clay type, pyrolysis peak temperature, and crude oil properties of the regional reservoir.
[0046] Furthermore, the number of fragmented samples and the corresponding temperature order m are 4 to 6.
[0047] Example 1:
[0048] See Figures 1 to 5 Two-dimensional nuclear magnetic resonance fluid distribution maps of shale oil were constructed from shale oil cores from the Qingshankou Formation in the Songliao Basin.
[0049] A full-diameter sealed core, sealed with wax and plastic wrap, was taken. A two-dimensional nuclear magnetic resonance (NMR) T1-T2 spectrum was measured at an echo interval of 0.2 ms and a measurement frequency of 12.5 MHz. The measurement results are as follows: Figure 2 As shown.
[0050] Samples were taken from a full-diameter sealed core, ensuring a core mass of at least 110g at the same depth. The core was crushed to 80 mesh and divided into five 20g portions and one 10g portion for later use. First, one 20g original sample was taken, and two-dimensional nuclear magnetic resonance T1-T2 measurements were performed at an echo interval of 0.1ms and a measurement frequency of 21MHz.
[0051] Five 20g fragments were heated directly to 80℃, 200℃, 350℃, 450℃ and 600℃ in an anaerobic environment at a heating rate of 50℃ / min. Each temperature was held for 2 minutes. After cooling, two-dimensional nuclear magnetic resonance T1-T2 measurements were performed with an echo interval of 0.1ms and a measurement frequency of 21MHz.
[0052] A pyrolysis experiment was conducted at five temperature levels: 80℃, 200℃, 350℃, 450℃, and 600℃, using 100mg of original fragmented sample taken from each sample after oxygen-free heating and 100mg of original sample taken from each sample. The temperature was increased at a rate of 50℃ / min. The hydrocarbon signals precipitated in the samples at each stage were detected by the YQ-VIIIA oil and gas display evaluation instrument.
[0053] Experimental results analysis and establishment of two-dimensional nuclear magnetic resonance fluid distribution plots:
[0054] like Figure 4 -(a) and Figure 4 As shown in (b), comparing the two-dimensional nuclear magnetic resonance spectra of the original fragmented sample and the fragmented sample heated to 80℃, region A in the spectrum of 4-(a) disappears after heating to 80℃. Based on the detection results of hydrocarbon signals from geochemical pyrolysis experiments, such as... Figure 3 As shown, no hydrocarbon signal was detected during the 0–2 min heating stage at 80 °C, indicating that the signal in region A is water, not oil or gas. In addition, capillary-bound water in shale can be easily removed under low-temperature heating conditions. Therefore, it can be determined that region A, where the signal disappears after heating at 80 °C, is capillary-bound water in the two-dimensional NMR spectrum of the sealed core fragments. T2 is distributed between 0.2 and 2 ms, with the central position around 0.6 ms, and T1 is distributed between 0.2 and 5 ms.
[0055] like Figure 4 -(b) and Figure 4 As shown in (c), after the sample was heated from 80℃ to 200℃, the signal in region B near the water line (T1 / T2=1) with short T2 and short T1 was significantly weakened. Generally, clay-bound water is difficult to flow and can only be removed at a temperature of 200℃ or higher. Therefore, region B is identified as clay-bound water. T2 is distributed between 0.02 and 0.2 ms, with the center position at about 0.7 ms, and T1 is distributed between 0.05 and 5 ms.
[0056] like Figure 2 As shown, the movable water is located in region C of length T2 on the waterline (T1 / T2=1), with T2 ranging from 2 to 50 ms and the central position around 10 ms. T1 ranges from 0.8 to 200 ms. Two-dimensional nuclear magnetic resonance spectra of the full-diameter sealed core show no obvious movable water in this region.
[0057] like Figure 4 As shown, Figure 4 In the two-dimensional NMR spectrum of -(a), the signal in region D increases with temperature. Figure 4 -(d)350℃ weakens, and at the same time, as Figure 3The results of the geochemical pyrolysis experiment on hydrocarbon signals show that when the original fragmented sample and the sample heated to 80℃ and 200℃ are heated to 350℃, a large amount of S2-1 hydrocarbon components are generated. At this time, the temperature does not reach the pyrolysis peak temperature of 445℃ in this region, and it is judged to be a hard organic matter pyrolysis product. Therefore, region D is hard organic matter. T2 is distributed between 0.02 and 0.2 ms, with the center position at about 0.7 ms, and T1 is distributed between 5 and 1000 ms.
[0058] like Figure 4 As shown, Figure 4 In the two-dimensional NMR spectrum of -(a), the signal in region E increases with temperature. Figure 4 -(e) The signal weakens after 450℃, while the signal in region D strengthens, such as Figure 3 The geochemical pyrolysis experiment results for hydrocarbon signals show that a large amount of S2-2 heavy hydrocarbon components are generated between 350℃ and 450℃. At this temperature, the regional pyrolysis peak temperature of 445℃ is reached. Kerogen undergoes extensive cracking to generate hydrocarbons and asphaltenes, resulting in signal enhancement in region D. Therefore, region E is identified as kerogen. T2 is distributed between 0.02 and 0.2 ms, with the central position around 0.7 ms, and T1 is distributed between 5 and 1000 ms.
[0059] like Figure 4 -(a) shows the original fragment sample and Figure 2 The comparison of two-dimensional nuclear magnetic resonance spectra of the full-diameter sealed cores shows a significant signal attenuation in regions F and G, indicating that the fluid in these regions was largely lost during sample preparation. The shale oil in this area has a density of 0.8537 g / cm³ and a viscosity of 15.10 mPa·s, characteristic of light oil, making it highly diffusive. Meanwhile, as... Figure 3 The geochemical pyrolysis experiment results for hydrocarbon signals show that the S0 signal is 0, therefore the signal in region F is mainly mobile oil. T2 is distributed between 2 and 50 ms, with the central position around 5 ms, and T1 is distributed between 10 and 1000 ms. Region G continues to lose hydrocarbons after heating at 80℃ and 200℃, as shown... Figure 3 The geochemical pyrolysis results shown indicate that a small amount of S1 signal is generated, indicating that region G is a bound oil region (containing movable oil). The location of the adsorbed oil was determined by comprehensively utilizing three experimental series: T2 is distributed between 0.2 and 2 ms, with the central position at around 0.6 ms, and T1 is distributed between 5 and 1000 ms.
[0060] Based on the above analysis, a two-dimensional nuclear magnetic resonance fluid distribution map of shale oil was drawn, as follows: Figure 5 As shown, the shale oil in this region is classified into seven types: capillary bound water, clay bound water, mobile water, hard organic matter, kerogen, mobile oil, and bound oil.
[0061] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for establishing a two-dimensional nuclear magnetic resonance fluid distribution map of shale oil, characterized in that, Includes the following steps: Two-dimensional nuclear magnetic resonance measurements were performed on a full-diameter sealed rock core. Samples were taken from a full-diameter sealed core, ground into fragments, and two-dimensional nuclear magnetic resonance measurements were performed on the original fragments. A portion of the fragmented original sample was heated at several temperature levels in an oxygen-free environment, and after cooling, two-dimensional nuclear magnetic resonance measurements were performed. A portion of the original fragmented sample and a portion of the fragmented sample heated in an oxygen-free environment were subjected to several temperature-level geochemical pyrolysis experiments to determine the hydrocarbon content. By comparing the signal changes in the two-dimensional nuclear magnetic resonance (NMR) spectra of full-diameter sealed cores and original fragments, comparing the signal changes in the two-dimensional NMR spectra of fragments before and after oxygen-free heating at different temperature levels, and comparing the changes in hydrocarbon content before and after geochemical pyrolysis experiments at different temperature levels, the components of two-dimensional NMR fluids in shale oil were identified, and a two-dimensional NMR fluid distribution map of shale oil was drawn.
2. The method for establishing a two-dimensional nuclear magnetic resonance fluid distribution map of shale oil according to claim 1, characterized in that, The measurement frequency for two-dimensional nuclear magnetic resonance (NMR) measurements of a full-diameter sealed core was 12.5 MHz, the echo interval was 0.2 ms, and the two-dimensional NMR T1-T2 spectrum was measured.
3. The method for establishing a two-dimensional nuclear magnetic resonance fluid distribution map of shale oil according to claim 1, characterized in that, The particle size of the original fragmented sample is 80 mesh.
4. The method for establishing a two-dimensional nuclear magnetic resonance fluid distribution map of shale oil according to claim 1, characterized in that, The measurement frequency for two-dimensional nuclear magnetic resonance (NMR) measurements on the original fragmented sample was 21 MHz, the echo interval was 0.1 ms, and the two-dimensional NMR T1-T2 spectrum was measured.
5. The method for establishing a two-dimensional nuclear magnetic resonance fluid distribution map of shale oil according to claim 1, characterized in that, Changes in hydrocarbon content before and after geochemical pyrolysis experiments were measured using the YQ-VIIIA oil and gas display and evaluation instrument.
6. The method for establishing a two-dimensional nuclear magnetic resonance fluid distribution map of shale oil according to claim 1, characterized in that, The measurement frequency for two-dimensional nuclear magnetic resonance (NMR) measurements after oxygen-free heating and cooling was 21 MHz, the echo interval was 0.1 ms, and the two-dimensional NMR T1-T2 spectrum was measured.
7. The method for establishing a two-dimensional nuclear magnetic resonance fluid distribution map of shale oil according to claim 1, characterized in that, The temperature values of the temperature steps are determined by the clay type, pyrolysis peak temperature, and crude oil properties of the regional reservoir. The number of fragmented samples and the corresponding temperature steps are both 4 to 6.
8. The method for establishing a two-dimensional nuclear magnetic resonance fluid distribution map of shale oil according to claim 1, characterized in that, In the geochemical pyrolysis experiment, the original fragment sample and the fragment sample heated under oxygen-free conditions had the same mass.
9. The method for establishing a two-dimensional nuclear magnetic resonance fluid distribution map of shale oil according to claim 1, characterized in that, The oxygen-free heating method is direct heating, with a heating rate of 50℃ / min, and each temperature step is held constant for 1 to 2 minutes.
10. The method for establishing a two-dimensional nuclear magnetic resonance fluid distribution map of shale oil according to claim 1, characterized in that, The geochemical pyrolysis experiment used a continuous heating method with a heating rate of 50℃ / min.