Three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis method and device based on static gradient magnetic field

Abstract

The invention discloses a three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis method and device based on a static gradient magnetic field, and the method comprises the steps: carrying out fluid saturation treatment on a to-be-measured rock core, placing the treated to-be-measured rock core in a preset environment condition, and simulating the fluid occurrence state in a reservoir under different escape time conditions; performing a nuclear magnetic resonance experiment on the to-be-tested rock core based on the static gradient magnetic field at each dissipation time point, and acquiring nuclear magnetic resonance echo data of the to-be-tested rock core at a plurality of different time points; and carrying out three-dimensional inversion calculation on the nuclear magnetic resonance echo data to obtain T1-T2-t three-dimensional distribution data, and carrying out visual analysis on the T1-T2-t three-dimensional distribution data to represent the temporal and spatial variation characteristics of the reservoir fluid. According to the method, the dissipation process of the fluid is combined with nuclear magnetic resonance T1-T2 distribution to form three-dimensional nuclear magnetic resonance data, and the spatial and temporal change of the occurrence state of the complex fluid in the unconventional oil and gas reservoir can be effectively captured.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas exploration, and particularly to a three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis method and device based on a static gradient magnetic field. Background Art

[0002] Nuclear Magnetic Resonance (NMR) logging technology is one of the important methods in modern oil and gas exploration, with significant advantages such as non-destructive detection, real-time analysis, and high precision. By measuring the magnetic resonance characteristics of hydrogen nuclei in fluids in the formation, NMR logging technology can achieve porosity analysis, permeability estimation, fluid type identification, etc.

[0003] However, with the development of unconventional oil and gas resources (such as shale gas and tight oil and gas) becoming the focus, traditional nuclear magnetic resonance logging technology faces a series of technical bottlenecks in application. These mainly include the following aspects: First, one-dimensional nuclear magnetic resonance measurement methods (such as T2 relaxation spectra) rely only on single-parameter analysis, so when affected by complex pore structures and fluid occurrence states, they are prone to multi-solution problems. For example, in tight oil and gas reservoirs, the short relaxation component signals are stronger, resulting in the overlap of oil, gas, and water signals, making it difficult to achieve precise discrimination. Second, two-dimensional nuclear magnetic resonance logging (such as T1-T2 two-dimensional spectra) can comprehensively characterize the fluid properties in complex reservoirs by combining T1 and T2 parameters, but its sensitivity to short relaxation time signals is limited, and it is easy to lose information on fluids in nanoscale pores in tight reservoirs; in addition, in unconventional oil and gas reservoirs, complex dissipation processes (such as the dissipation of volatile oils caused by different pore scales) are difficult to fully capture by two-dimensional spectra.

[0004] Therefore, the present invention proposes a three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis method and device based on a static gradient magnetic field. By introducing three-dimensional nuclear magnetic resonance imaging technology, the limitations of traditional nuclear magnetic resonance measurement methods are broken through, providing a higher-precision technical means for the evaluation of unconventional oil and gas reservoirs and fluid identification. Summary of the Invention

[0005] In view of this, the present invention provides a three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis method and device based on a static gradient magnetic field to solve the technical problem that existing nuclear magnetic resonance logging technology has insufficient ability to capture complex fluid occurrence states and dissipation processes in unconventional oil and gas resources and cannot accurately characterize the spatio-temporal variation characteristics of reservoir fluids.

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

[0007] On the one hand, the present invention provides a three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis method based on a static gradient magnetic field, including:

[0008] The core to be measured is subjected to fluid saturation treatment, and the treated core to be measured is placed in a preset environmental condition to simulate the fluid occurrence state in the reservoir under different dissipation time conditions;

[0009] At each dissipation time point, nuclear magnetic resonance (NMR) experiments are performed on the core to be measured based on a static gradient magnetic field, and NMR echo data of the core to be measured at multiple different time points are acquired;

[0010] Three-dimensional inversion calculation is performed on the acquired NMR echo data to obtain T1-T2-t three-dimensional distribution data, and visual analysis is performed on the T1-T2-t three-dimensional distribution data to characterize the spatio-temporal variation characteristics of the reservoir fluid.

[0011] Furthermore, the core to be measured is subjected to fluid saturation treatment, and the treated core to be measured is placed in a preset environmental condition, including:

[0012] The core to be measured in the irreducible water state is subjected to oil saturation treatment to simulate different fluid occurrence states in the reservoir;

[0013] The treated core to be measured is placed in an environment with a preset temperature and humidity for different lengths of time periods to simulate the dissipation process under the temperature and humidity conditions of an actual oil and gas reservoir.

[0014] Furthermore, at each dissipation time point, NMR experiments are performed on the core to be measured based on a static gradient magnetic field, including:

[0015] At each dissipation time point, the following NMR experiments are performed on the core to be measured based on a static gradient magnetic field:

[0016] At the initial moment, a 90° radio frequency pulse is applied to the core to be measured, a 180° radio frequency pulse is applied after an interval of half of the echo interval τ, and then a 180° radio frequency pulse is applied every 2τ thereafter;

[0017] Starting from the initial moment, an echo signal is acquired every 2τ until N echo signals are acquired;

[0018] where τ represents half of the echo interval time, and N represents a preset echo number threshold.

[0019] Furthermore, NMR echo data of the core to be measured at multiple different time points are acquired, including:

[0020] In the spin echo data at each time point, the echo amplitude is expressed as:

[0021]

[0022] In the formula, b i is the i-th echo at the waiting time Tws The amplitude of the echo at time; m is the transverse relaxation time T 2j The number of; p is the longitudinal relaxation time T 1k The number of; n is the fluid dissipation time point t r The number of; f(T 2j ,T 1k ,t r ) is the distribution function with respect to the transverse relaxation time T 2j , the longitudinal relaxation time T 1k , and the fluid dissipation time point t r ; L(t r ,X g ) is the function related to the dissipation time t r and the experimental condition X g ; Tws is the waiting time; t i is the acquisition time of the i-th echo.

[0023] Furthermore, at each fluid dissipation time point, nuclear magnetic resonance experiments are performed on the core to be measured based on a static gradient magnetic field, and nuclear magnetic resonance echo data of the core to be measured at multiple different time points are collected, further including:

[0024] When collecting signals each time, the method of superimposing and averaging multiple echo signals is used to improve the signal-to-noise ratio and data stability.

[0025] Furthermore, three-dimensional inversion calculation is performed on the collected nuclear magnetic resonance echo data to obtain three-dimensional T1-T2-t distribution data, and visual analysis is performed on the three-dimensional T1-T2-t distribution data, including:

[0026] Using a three-dimensional inversion algorithm based on the collected nuclear magnetic resonance echo data to obtain three-dimensional T1-T2-t distribution data;

[0027] Based on the three-dimensional T1-T2-t distribution data, through three-dimensional visualization algorithm processing, a three-dimensional nuclear magnetic resonance T1-T2-t distribution map is obtained.

[0028] Furthermore, through three-dimensional visualization algorithm processing to obtain a three-dimensional nuclear magnetic resonance T1-T2-t distribution map, it further includes:

[0029] Setting an effective numerical range according to the characteristics of fluid behavior data, deleting the data in the three-dimensional T1-T2-t distribution data that does not belong to the effective numerical range, and optimizing the visualization effect.

[0030] Furthermore, when performing fluid saturation treatment on the core to be measured and placing the treated core to be measured in a preset environmental condition, it further includes:

[0031] Adjust the pressure parameter in the preset environmental conditions to simulate the influence of the fluid escape characteristics corresponding to different underground depths.

[0032] On the other hand, the present invention also proposes a three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis device based on a static gradient magnetic field for the above technical solution, including: a data processing module, and a data acquisition module and an experimental environment control module connected to the data processing module;

[0033] The data acquisition module is used to provide a stable static magnetic field and a radio frequency magnetic field for the core to be measured, apply a magnetic field gradient, and acquire the nuclear magnetic resonance echo data of the core to be measured;

[0034] The experimental environment control module is used to provide a preset temperature and humidity environment for the core to be measured to simulate the formation environment;

[0035] The data processing module is used to perform three-dimensional inversion calculation on the acquired nuclear magnetic resonance echo data to obtain the three-dimensional distribution data of T1-T2-t, and perform visual analysis and display on the data.

[0036] Furthermore, the data acquisition module includes a magnet system, a gradient system, and a radio frequency system;

[0037] The magnet system is used to provide a stable static magnetic field;

[0038] The gradient system is used to apply an adjustable magnetic field gradient;

[0039] The radio frequency system is used to generate a radio frequency magnetic field and acquire the nuclear magnetic resonance echo data of the core to be measured.

[0040] Compared with the prior art, the three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis method and device based on a static gradient magnetic field proposed by the present invention introduce the time dimension, combine the fluid escape process with the nuclear magnetic resonance T1-T2 distribution to form three-dimensional nuclear magnetic resonance data, so as to effectively capture the spatio-temporal changes of the complex fluid occurrence state in unconventional oil and gas reservoirs, more comprehensively characterize the fluid behavior in complex formations, provide a higher-precision technical means for pore characterization and fluid type identification of tight reservoirs, and provide technical guarantee for the efficient development of unconventional oil and gas reservoirs. Description of the Drawings

[0041] Figure 1 It is a schematic flow chart of the three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis method provided by the present invention;

[0042] Figure 2 It is a schematic diagram of the three-dimensional nuclear magnetic resonance response of T1-T2-t for simulating fluid escape provided by the present invention;

[0043] Figure 3Schematic structural diagram of the three-dimensional nuclear magnetic resonance rock sample fluid experiment analysis device based on a static gradient magnetic field provided by the present invention. Specific embodiments

[0044] The following will specifically describe the preferred embodiments of the present invention in conjunction with the accompanying drawings. The accompanying drawings form a part of this application and are used together with the embodiments of the present invention to explain the principles of the present invention, rather than to limit the scope of the present invention.

[0045] Example 1

[0046] Please refer to Figure 1 , this embodiment provides a three-dimensional nuclear magnetic resonance rock sample fluid experiment analysis method based on a static gradient magnetic field, including:

[0047] Step S101: Perform fluid saturation treatment on the core to be measured, and place the treated core to be measured in a preset environmental condition to simulate the fluid occurrence state in the reservoir under different dissipation time conditions;

[0048] Step S102: Perform nuclear magnetic resonance experiments on the core to be measured based on the static gradient magnetic field at each dissipation time point, and collect the nuclear magnetic resonance echo data of the core to be measured at multiple different time points;

[0049] Step S103: Perform three-dimensional inversion calculation on the collected nuclear magnetic resonance echo data to obtain the three-dimensional distribution data of T1-T2-t, and perform visual analysis on the three-dimensional distribution data of T1-T2-t to characterize the spatio-temporal variation characteristics of the reservoir fluid.

[0050] The three-dimensional nuclear magnetic resonance rock sample fluid experiment analysis method based on a static gradient magnetic field proposed in this embodiment combines the fluid dissipation process with the nuclear magnetic resonance T1-T2 distribution by introducing the time dimension t to form three-dimensional nuclear magnetic resonance data, thereby being able to effectively capture the spatio-temporal variation of the complex fluid occurrence state in unconventional oil and gas reservoirs, more comprehensively characterize the fluid behavior in complex formations, provide a higher-precision technical means for pore characterization and fluid type identification in tight reservoirs, and provide technical support for the efficient development of unconventional oil and gas reservoirs.

[0051] As a preferred embodiment, in step S101, the performing fluid saturation treatment on the core to be measured and placing the treated core to be measured in a preset environmental condition includes:

[0052] Perform saturated oil treatment on the core to be measured in the bound water state to simulate different fluid occurrence states in the reservoir;

[0053] Place the treated core to be measured in an environment with a preset temperature and humidity for different lengths of time periods to simulate the dissipation process under the temperature and humidity conditions of an actual oil and gas reservoir.

[0054] It should be noted that the core sample to be tested in the bound water state is selected because in the underground oil reservoir, the reservoir water is usually not completely free water but exists in the form of bound water. Therefore, selecting the core sample to be tested in the bound water state for saturated oil treatment can obtain experimental data closer to the actual reservoir conditions. In addition, the selected core needs to have a typical pore structure of the oil and gas reservoir, especially the nanoscale pores commonly found in unconventional oil and gas reservoirs. Different pore structures have a great impact on the storage, flow, and permeability of oil and gas. The pore structure of the core is highly correlated with the actual situation of the oil and gas reservoir. Selecting a core with a typical pore structure can better reproduce the behavior of fluids in the reservoir and provide real experimental data.

[0055] At the beginning of the experiment, the core sample in the bound water state is treated with saturated n-dodecane to simulate different fluid occurrence states in the reservoir; then the saturated core is placed in an experimental chamber with temperature control and humidity control to simulate the temperature and humidity conditions of the actual oil and gas reservoir. Specifically, the ambient temperature is controlled at 25 °C and the humidity is controlled at 40% to simulate the dissipation process of different fluids. The placement duration is set to 1 hour, 2 hours, 4 hours, etc. to simulate different dissipation times (the dissipation time is dynamically adjusted according to the experimental requirements). At the time point at the end of each dissipation period, the sample is sampled and detected. The weight of the core is measured using an electronic balance, and the weight change of the core and the corresponding nuclear magnetic resonance response at each stage are recorded.

[0056] Each time a nuclear magnetic resonance experiment is performed, the weighed core sample is wrapped successively with plastic wrap and polytetrafluoroethylene, and the wrapped core is placed in a magnetic field container, and a radio frequency pulse is applied through a radio frequency coil to form a static gradient magnetic field. Under the static gradient magnetic field, a nuclear magnetic resonance pulse sequence is applied to the sample to collect the echo train signal of the core. By changing the dissipation time t and the waiting time TW parameters, nuclear magnetic resonance echo data at different dissipation stages are obtained; among them, the waiting time (TW) refers to the interval between single pulses in the pulse sequence used in the nuclear magnetic resonance experiment.

[0057] In order to simulate the fluid occurrence state of the actual underground oil and gas reservoir, in some embodiments, for the fluid saturation treatment of the core to be tested and placing the treated core to be tested in a preset environmental condition, it further includes:

[0058] Adjust the pressure parameter in the preset environmental condition to simulate the influence of fluid dissipation characteristics corresponding to different underground depths.

[0059] By adjusting the pressure parameter in the temperature-controlled environment, the fluid dissipation characteristics corresponding to different underground depths are simulated. During some experimental processes, a tracer can also be used to calibrate the fluid dissipation process to improve the comparability of the data.

[0060] As a preferred embodiment, in step S102, at the end of each waiting duration, a nuclear magnetic resonance experiment is performed on the core to be measured based on a static gradient magnetic field, including:

[0061] At each dissipation time point, the following nuclear magnetic resonance experiments are performed on the core to be measured based on a static gradient magnetic field:

[0062] Apply a 90° radio frequency pulse to the core to be measured at the initial moment, apply a 180° radio frequency pulse after an interval of half of the echo interval τ, and then apply a 180° radio frequency pulse every 2τ thereafter;

[0063] Collect an echo signal every 2τ starting from the initial moment until N echo signals are collected;

[0064] Where τ represents half of the echo interval time, and N represents a preset echo number threshold.

[0065] In the specific experimental implementation process, a 90° radio frequency pulse is applied to the sample to be measured at time 0; wait for half of the echo interval TE, and apply a 180° radio frequency pulse at time τ; wait for half of the echo interval TE, and a complete discrete spin echo signal is collected at time 2τ; apply 180° radio frequency pulses at 3τ, 5τ... (2n - 1)τ respectively, n = 1, 2... N; repeat the above steps until N spin echo signals are collected at 4τ, 6τ... 2nτ, and the N spin echo signals form an echo train signal.

[0066] After each application of the 180° radio frequency pulse, by collecting the echo signal, the relaxation process (T1, T2) of the spin can be accurately recorded in the time domain. Through the collection of echo signals at multiple moments, richer spatio-temporal data can be provided for subsequent data analysis and modeling. In the data fitting and modeling process, the time interval information between multiple echo signals can be utilized to obtain more accurate model parameters, especially for the accurate evaluation of reservoir fluid properties, porosity, permeability, etc. Especially for the fluid behavior in unconventional oil and gas reservoirs. This helps to identify the distribution state of the fluid, understand the behavior of the fluid in the pores, and can more realistically simulate the flow characteristics of the fluid in the actual reservoir.

[0067] As a preferred embodiment, nuclear magnetic resonance echo data of the core to be measured at multiple different time points are collected, including:

[0068] In the spin echo data of each time point, the echo amplitude is expressed as:

[0069]

[0070] In the formula, b i is the i-th echo at the waiting time T wsAmplitude of the echo at that time; m is the transverse relaxation time T 2j The number of; p is the longitudinal relaxation time T 1k The number of; n is the fluid dissipation time point t r The number of; f(T 2j ,T 1k ,t r ) is the distribution function with respect to the transverse relaxation time being T 2j , the longitudinal relaxation time being T 1k , and the fluid dissipation time point t r ; L(t r ,X g ) is the function related to the dissipation time t r and the experimental condition X g ; Tws is the waiting time; t i is the acquisition time of the i-th echo.

[0071] By performing three-dimensional inversion on Equation (1), the three-dimensional distribution data of T1 - T2 - t can be obtained.

[0072] As a specific embodiment, during each acquisition of nuclear magnetic resonance signals, by adjusting parameters such as the amplitude, frequency, echo interval (TE), and waiting time (TW) of the radio frequency pulse, the timing of signal acquisition is optimized.

[0073] By precisely controlling the parameters, noise and background interference can be reduced, the quality of the signal can be improved, which helps to accurately measure the relaxation time of the sample and the physical properties of molecular motion, providing a basis for subsequent analysis.

[0074] Furthermore, for each acquired signal, in addition to the conventional measurement of echo intensity, a method of superimposing and averaging multiple echo signals is also introduced to improve the signal-to-noise ratio and data stability. The nuclear magnetic resonance echo signals at each dissipation time are acquired and superimposed multiple times to improve the signal-to-noise ratio. The acquired data includes the T1 and T2 relaxation times, as well as the signal intensities at each dissipation stage.

[0075] As a specific embodiment, during the experiment, the magnetic field intensity is set to 0.5 T (resonance frequency is 21 MHz), and the T1 - T2 two-dimensional spectra at different dissipation stages are acquired using CPMG and IR - CPMG sequences. The number of echoes (NECH) is set to 12000, the number of superimpositions (SCAN) is set to 16, the echo interval (TE) is set to 0.1 ms, and the waiting time (TW) is set to 4000 ms. The exposure time of core dissipation is set to 0 hours, 1 hour, 2 hours, 4 hours, 8 hours, 16 hours, 32 hours, 64 hours, 96 hours, 160 hours, 248 hours.

[0076] As a preferred embodiment, in step S103, three-dimensional inversion calculation is performed on the collected nuclear magnetic resonance echo data to obtain T1-T2-t three-dimensional distribution data, and visual analysis is performed on the T1-T2-t three-dimensional distribution data, including:

[0077] Using a three-dimensional inversion algorithm based on the collected nuclear magnetic resonance echo data to obtain T1-T2-t three-dimensional distribution data;

[0078] Based on the T1-T2-t three-dimensional distribution data, through three-dimensional visualization algorithm processing, a three-dimensional nuclear magnetic resonance T1-T2-t distribution map is obtained.

[0079] Through the visual analysis of the T1-T2-t three-dimensional nuclear magnetic resonance data, the spatial distribution and dynamic evolution process of reservoir fluids can be accurately characterized, significantly improving the fluid identification accuracy and reservoir evaluation ability.

[0080] As Figure 2 shown, Figure 2 The generated T1-T2-t three-dimensional nuclear magnetic resonance distribution map is shown. Each planar graph in the figure represents the T1-T2 distribution at a specific dissipation time. The T1-T2-t three-dimensional data is used to distinguish different fluid types such as oil, water, and gas. Multiple planar graphs are superimposed together, and the changes of fluids at different time points are shown by translating different time axes. The color depth of each data point represents the intensity of the fluid signal, so as to achieve accurate distinction of different fluid types (such as oil, water, gas). At the same time, using high-precision interpolation technology, it is ensured that the generated three-dimensional data map has higher spatial resolution and more detailed hierarchical structure. The T1-T2-t three-dimensional data can provide a quantitative basis for the reservoir evaluation of unconventional oil and gas reservoirs.

[0081] As a specific embodiment, in order to effectively remove data noise, enhance the clarity of the graph, so that only the key signal part is visually displayed, helping researchers to focus more on the actual measurement results, the method of setting a data threshold range is adopted to remove the low-value data (such as data that does not conform to significant fluid behavior) in the echo data to achieve a transparency effect. As the data at different dissipation times (t) are displayed in layers according to the time axis position, the change trend of the fluid over time can be reflected. Through this three-dimensional layered display method, the fluid behavior at each time point can be clearly compared, revealing the evolution law of the reservoir.

[0082] In some embodiments, in order to ensure the representativeness of the experiment, the experiment will conduct multiple repeated tests on different types of cores, analyze their effects on fluid behavior, and optimize the temperature, humidity, time parameters, etc. of the dissipation simulation by analyzing the comparison between the experimental results and the geological model.

[0083] By introducing the dissipation time (t) as the third dimension and drawing a three-dimensional heat map, the method of this embodiment can visualize the fluid occurrence state in the reservoir, helping researchers more intuitively identify and analyze the fluid distribution.

[0084] Embodiment 2

[0085] As Figure 3 shown, this embodiment also provides an apparatus 300 applied to the above three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis method based on a static gradient magnetic field, including: a data processing module 303, and a data acquisition module 301 and an experimental environment control module 302 connected to the data processing module 303;

[0086] The data acquisition module 301 is configured to provide a stable static magnetic field and a radio frequency magnetic field for the core to be measured, apply a magnetic field gradient, and acquire nuclear magnetic resonance echo data of the core to be measured;

[0087] The experimental environment control module 302 is configured to provide a preset temperature and humidity environment for the core to be measured to simulate the formation environment;

[0088] The data processing module 303 is configured to perform three-dimensional inversion calculation on the acquired nuclear magnetic resonance echo data to obtain T1-T2-t three-dimensional distribution data, and perform visual analysis and display on the data.

[0089] As a preferred embodiment, the data acquisition module includes a magnet system, a gradient system, and a radio frequency system;

[0090] The magnet system is configured to provide a stable static magnetic field;

[0091] The gradient system is configured to apply an adjustable magnetic field gradient;

[0092] The radio frequency system is configured to generate a radio frequency magnetic field and acquire nuclear magnetic resonance echo data of the core to be measured.

[0093] The magnet system is used to provide a stable static B0 magnetic field, the gradient system provides a controllable magnetic field gradient, and the radio frequency system performs signal acquisition through nuclear magnetic resonance CPMG and IR-CPMG pulse sequences.

[0094] As a specific embodiment, the experimental environment control module includes a constant temperature and humidity chamber and a fluid dissipation control device, which can dynamically adjust the temperature, humidity, and pressure to simulate different underground oil and gas reservoir conditions and simulate the formation environment. Before the experiment starts, the set temperature, humidity, and pressure values are sent to the data processing module for condition recording.

[0095] In some embodiments, the environment control module in the three-dimensional nuclear magnetic resonance experimental device includes an automatic adjustment unit;

[0096] The automatic adjustment unit is used to automatically adjust the temperature, humidity and air pressure according to different experimental settings, ensuring the stability of experimental conditions and avoiding the interference of environmental factors on experimental results.

[0097] In some embodiments, the data processing module further includes a high-performance processor and a dedicated algorithm program for generating a high-resolution T1-T2-t three-dimensional distribution heat map.

[0098] Specifically, the dedicated algorithm program first uses Tikhonov regularization, Levenberg-Marquardt optimization algorithm, etc. to invert the T1, T2 relaxation time and time resolution data to obtain accurate T1-T2-t three-dimensional data; then uses efficient image processing algorithms (such as fast Fourier transform (FFT), discrete wavelet transform (DWT), etc.) to perform three-dimensional reconstruction on the inversion results, and removes the noise in the data through methods such as Kalman filtering and SVD (singular value decomposition) to ensure a high signal-to-noise ratio of the analysis results. Finally, the data points (T1-T2-t three-dimensional distribution) are converted into a visual effect through a heat map mapping and rendering algorithm.

[0099] The three-dimensional nuclear magnetic resonance rock sample fluid experiment analysis method and device based on a static gradient magnetic field provided by the present invention introduce the time dimension, combine the dissipation process of the fluid with the nuclear magnetic resonance T1-T2 distribution to form three-dimensional nuclear magnetic resonance data, so as to effectively capture the spatio-temporal changes of the complex fluid occurrence state in unconventional oil and gas reservoirs, more comprehensively characterize the fluid behavior in complex formations, and provide a higher-precision technical means for pore characterization of tight reservoirs and fluid type identification. The present invention realizes the comprehensive characterization of the fluid characteristics of complex reservoirs, improves the accuracy of fluid identification and the accuracy of reservoir evaluation, breaks through the limitations of traditional nuclear magnetic resonance measurement methods, and has important application value in reservoir evaluation, fluid identification, etc. of unconventional oil and gas reservoirs (such as shale gas, tight oil and gas).

[0100] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis method based on a static gradient magnetic field, characterized in that: include: Perform fluid saturation treatment on the core to be tested, place the treated core to be tested in preset environmental conditions, and simulate the fluid occurrence state in the reservoir under different escape time conditions; Performing nuclear magnetic resonance experiments on the core to be tested based on a static gradient magnetic field at each escape time point, and acquiring nuclear magnetic resonance echo data of the core to be tested at multiple different time points; The collected nuclear magnetic resonance echo data are subjected to three-dimensional inversion calculation to obtain T1-T2-t three-dimensional distribution data, and the T1-T2-t three-dimensional distribution data are visualized and analyzed to characterize the temporal and spatial variation characteristics of the reservoir fluid.

2. The three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis method based on static gradient magnetic field according to claim 1 is characterized in that: The core to be tested is subjected to fluid saturation treatment and the treated core to be tested is placed in a preset environmental condition, including: The core to be tested in the bound water state is saturated with oil to simulate the different fluid occurrence states in the reservoir; The processed core to be tested is placed in an environment with preset temperature and humidity for different time periods to simulate the escape process under the temperature and humidity conditions of actual oil and gas reservoirs.

3. The three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis method based on static gradient magnetic field according to claim 1 is characterized in that: At each escape time point, nuclear magnetic resonance experiments are performed on the core to be tested based on a static gradient magnetic field, including: At each escape time point, the following NMR experiments were performed on the core to be tested based on a static gradient magnetic field: At the initial moment, a 90° RF pulse is applied to the core to be tested, and a 180° RF pulse is applied after half the echo interval τ, and then a 180° RF pulse is applied after every 2τ interval; After the initial moment, an echo signal is collected every 2τ until N echo signals are collected; Wherein, τ represents half the echo interval time, and N represents the preset echo quantity threshold.

4. The three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis method based on static gradient magnetic field according to claim 1 is characterized in that: The nuclear magnetic resonance echo data of the core to be tested at multiple different time points are collected, including: In the spin echo data at each time point, the echo amplitude is expressed as: Where b i is the i-th echo after waiting time T ws The amplitude of the echo at time t; m is the transverse relaxation time T 2j The number of; p is the longitudinal relaxation time T 1k The number of; n is the time point t at which the fluid escapes r The number of 2j ,T 1k ,t r ) is about the transverse relaxation time T 2j , the longitudinal relaxation time is T 1k , fluid escape time t r The distribution function of L(t r ,X g ) is the escape time t r With experimental conditions X g Related functions; Tws is the waiting time; t i is the acquisition time of the ith echo.

5. The three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis method based on static gradient magnetic field according to claim 1 is characterized in that: A nuclear magnetic resonance experiment is performed on the core to be tested based on a static gradient magnetic field at each escape time point, and nuclear magnetic resonance echo data of the core to be tested at multiple different time points are collected, including: Each time the signal is collected, the method of superposition and averaging of multiple echo signals is adopted to improve the signal-to-noise ratio and data stability.

6. The three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis method based on static gradient magnetic field according to claim 1 is characterized in that: Perform three-dimensional inversion calculation on the collected nuclear magnetic resonance echo data to obtain T1-T2-t three-dimensional distribution data, and perform visual analysis on the T1-T2-t three-dimensional distribution data, including: The three-dimensional distribution data of T1-T2-t is obtained based on the collected nuclear magnetic resonance echo data using a three-dimensional inversion algorithm; Based on the T1-T2-t three-dimensional distribution data, the three-dimensional nuclear magnetic resonance T1-T2-t distribution map is obtained through three-dimensional visualization algorithm processing.

7. The three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis method based on static gradient magnetic field according to claim 6 is characterized in that: Through the three-dimensional visualization algorithm processing, the three-dimensional nuclear magnetic resonance T1-T2-t distribution spectrum is obtained, which also includes: The valid numerical range is set according to the characteristics of the fluid behavior data, and the data that does not belong to the valid numerical range in the T1-T2-t three-dimensional distribution data is deleted to optimize the visualization effect.

8. The three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis method based on static gradient magnetic field according to claim 1 is characterized in that: The fluid saturation treatment is performed on the core to be tested, and the treated core to be tested is placed in a preset environmental condition, and further includes: Adjust the pressure parameters in the preset environmental conditions to simulate the influence of fluid escape characteristics corresponding to different underground depths.

9. A three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis device based on a static gradient magnetic field applied to claim 1, characterized in that: include: A data processing module, and a data acquisition module and an experimental environment control module connected to the data processing module; A data acquisition module is used to provide a stable static magnetic field and a radio frequency magnetic field for the core to be tested, apply a magnetic field gradient, and collect nuclear magnetic resonance echo data of the core to be tested; The experimental environment control module is used to provide a preset temperature and humidity environment for the core to be tested to simulate the formation environment; The data processing module is used to perform three-dimensional inversion calculation on the collected nuclear magnetic resonance echo data, obtain T1-T2-t three-dimensional distribution data, and perform visual analysis and display of the data.

10. The three-dimensional nuclear magnetic resonance rock sample fluid experimental analysis device based on static gradient magnetic field according to claim 9, characterized in that: The data acquisition module includes a magnet system, a gradient system and a radio frequency system; A magnet system for providing a stable static magnetic field; a gradient system for applying an adjustable magnetic field gradient; The radio frequency system is used to generate a radio frequency magnetic field and collect nuclear magnetic resonance echo data of the rock core to be tested.

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