A three-dimensional nuclear magnetic resonance rock sample fluid experiment analysis method and device based on a static gradient magnetic field

Abstract

The application discloses a three-dimensional nuclear magnetic resonance rock sample fluid experiment analysis method and device based on a static gradient magnetic field, and the method comprises the following steps: performing fluid saturation treatment on a to-be-detected core, placing the treated to-be-detected core in a preset environment condition, and simulating fluid occurrence states in a reservoir under different diffusion time conditions; performing nuclear magnetic resonance experiments on the to-be-detected core based on the static gradient magnetic field at each diffusion time point, and collecting nuclear magnetic resonance echo data of the to-be-detected core at multiple different time points; performing three-dimensional inversion calculation on the nuclear magnetic resonance echo data, obtaining T1-T2-t three-dimensional distribution data, and performing visual analysis on the T1-T2-t three-dimensional distribution data, so as to represent the space-time variation characteristics of the reservoir fluid. The application combines the diffusion process of the fluid with the nuclear magnetic resonance T1-T2 distribution, forms three-dimensional nuclear magnetic resonance data, and can effectively capture the space-time variation of the complex fluid occurrence state in the unconventional oil and gas reservoir.

Description

TECHNICAL FIELD

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

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

[0003] However, with the development of unconventional oil and gas resources (such as shale gas, tight oil and gas) as the focus, the traditional nuclear magnetic resonance logging technology faces a series of technical bottlenecks in application. Mainly including the following aspects: first, the one-dimensional nuclear magnetic resonance measurement method (such as T2 relaxation spectrum) only relies on single parameter analysis, so when affected by complex pore structure and fluid occurrence state, it is easy to produce multiple solutions. For example, in tight oil and gas reservoirs, the signal of short relaxation component is strong, which leads to the overlap of oil, gas and water signals, and it is difficult to realize accurate distinction. Secondly, although two-dimensional nuclear magnetic resonance logging (such as T1-T2 two-dimensional spectrum) can combine T1 and T2 parameters to more comprehensively characterize the fluid properties in complex reservoirs, the sensitivity to short relaxation time signals is limited, and the information of fluid in nanoscale pores in tight reservoirs is easy to be lost; in addition, in unconventional oil and gas reservoirs, the complex dispersion process (such as volatile oil dispersion caused by different pore sizes) is difficult to be fully captured by two-dimensional spectrum.

[0004] Therefore, the present application proposes a three-dimensional nuclear magnetic resonance rock sample fluid experiment analysis method and device based on a static gradient magnetic field, which breaks through the limitations of traditional nuclear magnetic resonance measurement methods by introducing three-dimensional nuclear magnetic resonance imaging technology, and provides a higher precision technical means for unconventional oil and gas reservoir evaluation and fluid identification. SUMMARY

[0005] Therefore, the present application provides a three-dimensional nuclear magnetic resonance rock sample fluid experiment analysis method and device based on a static gradient magnetic field, which solves the technical problem that the existing nuclear magnetic resonance logging technology has insufficient ability to capture complex fluid occurrence state and dispersion process in unconventional oil and gas resources, and cannot accurately characterize the spatial and temporal variation characteristics of reservoir fluid.

[0006] To achieve the above technical purpose, the present application adopts the following technical scheme:

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

[0008] The fluid-saturated treatment is performed on the measured core, and the treated measured core is placed in a preset environment condition to simulate fluid occurrence states in the reservoir under different diffusion time conditions.

[0009] The nuclear magnetic resonance experiment is performed on the measured core based on the static gradient magnetic field at each diffusion time point, and nuclear magnetic resonance echo data of the measured core at multiple different time points are acquired.

[0010] The acquired 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 subjected to visual analysis to represent the space-time variation characteristics of the reservoir fluid.

[0011] Further, the fluid-saturated treatment is performed on the measured core, and the treated measured core is placed in a preset environment condition, including:

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

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

[0014] Further, the nuclear magnetic resonance experiment is performed on the measured core based on the static gradient magnetic field at each diffusion time point, including:

[0015] At each diffusion time point, the following nuclear magnetic resonance experiment is performed on the measured core based on the static gradient magnetic field:

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

[0017] A echo signal is acquired every 2τ after the initial moment, until N echo signals are acquired.

[0018] Wherein, τ represents a half echo interval time, and N represents a preset echo quantity threshold.

[0019] Further, the nuclear magnetic resonance echo data of the measured core at multiple different time points are acquired, including:

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

[0021]

[0022] In the formula, b i is the i-th echo at the waiting time Tws the amplitude of the echo; m is the number of transverse relaxation times T 2j 1k the number of longitudinal relaxation times T r 2j 1k r 2j 1k r r g r g i Tws is the waiting time; t

[0023] Further, the nuclear magnetic resonance experiment is performed on the measured core based on the static gradient magnetic field at each diffusion time point respectively, and the nuclear magnetic resonance echo data of the measured core at multiple different time points is collected, which further includes:

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

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

[0026] The T1-T2-t three-dimensional distribution data is obtained based on the collected nuclear magnetic resonance echo data by using the three-dimensional inversion algorithm;

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

[0028] Further, the three-dimensional nuclear magnetic resonance T1-T2-t distribution map is obtained by processing the three-dimensional visualization algorithm, which further includes:

[0029] According to the fluid behavior data characteristics, the effective numerical range is set, the data in the T1-T2-t three-dimensional distribution data which does not belong to the effective numerical range is deleted, and the visualization effect is optimized.

[0030] Further, the fluid saturation treatment is performed on the measured core, and the processed measured core is placed in a predetermined environmental condition, which further includes:

[0031] ​​​​​​​​​​​​Adjust the pressure parameter in the preset environmental condition to simulate the influence of different underground depths on fluid dissipation characteristics.

[0032] In another aspect, the application also provides a three-dimensional nuclear magnetic resonance rock sample fluid experiment analysis device based on a static gradient magnetic field, applied to the technical solution, comprising: a data processing module, and a data acquisition module and an experiment environment control module connected with the data processing module;

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

[0034] The experiment environment control module is configured to provide a preset temperature and humidity environment for the rock core to be measured to simulate a formation environment.

[0035] The data processing module 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.

[0036] Further, the data acquisition module comprises a magnet system, a gradient system and a radio frequency system.

[0037] The magnet system is configured to provide a stable static magnetic field.

[0038] The gradient system is configured to apply an adjustable magnetic field gradient.

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

[0040] Compared with the prior art, the three-dimensional nuclear magnetic resonance rock sample fluid experiment analysis method and device based on a static gradient magnetic field can effectively capture the space-time variation of the complex fluid occurrence state in unconventional oil and gas reservoirs by introducing a time dimension, combining the dissipation process of the fluid with the nuclear magnetic resonance T1-T2 distribution, forming three-dimensional nuclear magnetic resonance data, and more comprehensively representing the fluid behavior in complex formations, thereby providing a higher precision technical means for tight reservoir pore characterization and fluid type identification, and providing a technical guarantee for efficient development of unconventional oil and gas reservoirs. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 A flowchart of the three-dimensional nuclear magnetic resonance rock sample fluid experiment analysis method based on a static gradient magnetic field provided by the application is shown.

[0042] Figure 2 A T1-T2-t three-dimensional nuclear magnetic resonance response diagram for simulating fluid dissipation provided by the application is shown.

[0043] Figure 3A structure schematic diagram of a three-dimensional nuclear magnetic resonance rock sample fluid experiment analysis device based on a static gradient magnetic field is provided. DETAILED DESCRIPTION

[0044] The preferred embodiments of the present application will be described in detail below with reference to the drawings, wherein the drawings constitute a part of this application, and are used to explain the principles of the embodiments of the present application, but are not used to limit the scope of the present application.

[0045] Embodiment 1

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

[0047] Step S101: performing fluid saturation treatment on a to-be-tested core, and placing the treated to-be-tested core in a preset environment condition to simulate fluid occurrence states in a reservoir under different diffusion time conditions;

[0048] Step S102: performing nuclear magnetic resonance experiment on the to-be-tested core based on a static gradient magnetic field at each diffusion time point, and collecting nuclear magnetic resonance echo data of the to-be-tested core at multiple different time points;

[0049] Step S103: performing three-dimensional inversion calculation on the collected nuclear magnetic resonance echo data to obtain T1-T2-t three-dimensional distribution data, and performing visual analysis on the T1-T2-t three-dimensional distribution data to represent the space-time 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 provided in the embodiment combines the diffusion process of the fluid with the nuclear magnetic resonance T1-T2 distribution by introducing the time dimension t, forms three-dimensional nuclear magnetic resonance data, and can effectively capture the space-time variation of the complex fluid occurrence state in the unconventional oil and gas reservoir, more comprehensively represents the fluid behavior in the complex formation, provides a higher-precision technical means for the tight reservoir pore characterization and fluid type identification, and provides a technical guarantee for the efficient development of the unconventional oil and gas reservoir.

[0051] As a preferred embodiment, in step S101, the fluid saturation treatment on the to-be-tested core and the placement of the treated to-be-tested core in the preset environment condition comprise:

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

[0053] Placing the treated to-be-tested core in an environment with a preset temperature and humidity for a time period with different lengths to simulate the diffusion process under the actual oil and gas reservoir temperature and humidity conditions.

[0054] It should be noted that the core sample to be measured 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, by treating the core sample to be measured in the bound water state with saturated oil, experimental data closer to the actual reservoir conditions can be obtained. In addition, the selected core needs to have a typical oil and gas reservoir pore structure, especially the nanoscale pores commonly found in unconventional oil and gas reservoirs. Different pore structures have a great influence on the storage, flow and permeability of oil and gas. The pore structure of the core is highly related to the actual situation of the oil and gas reservoir. By selecting a core with a typical pore structure, the behavior of the fluid in the oil reservoir can be better reproduced, and real experimental data can be provided.

[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 box with temperature and humidity control to simulate the temperature and humidity conditions of the actual oil and gas reservoir. Specifically, the environmental temperature is controlled at 25℃, and the humidity is controlled at 40%. The escape process of different fluids is simulated. The length of time is set to 1 hour, 2 hours, 4 hours, etc. to simulate different escape times (here, the escape time is dynamically adjusted according to experimental requirements). At the end of each escape time 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 at each stage and the corresponding nuclear magnetic resonance response are recorded.

[0056] In each nuclear magnetic resonance experiment, the weighed core sample is wrapped with cling film and polytetrafluoroethylene in turn, and the wrapped core is placed in a magnetic field container. A static gradient magnetic field is formed by applying a radio frequency pulse through a radio frequency coil. 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 escape time t and the waiting time TW parameters, nuclear magnetic resonance echo data at different escape stages is obtained; wherein the waiting time (TW) is 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, the fluid saturation treatment of the core to be measured, and the placement of the treated core to be measured in the preset environmental conditions further comprises:

[0058] Adjust the pressure parameter in the preset environmental conditions to simulate the influence of different underground depths on the fluid escape characteristics.

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

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

[0061] The following nuclear magnetic resonance experiment is performed on the to-be-tested core based on the static gradient magnetic field at each T2 relaxation time point:

[0062] A 90° radio frequency pulse is applied to the to-be-tested core at the initial moment, a 180° radio frequency pulse is applied after an interval of half echo interval τ, and then a 180° radio frequency pulse is applied every interval of 2τ;

[0063] A echo signal is collected every interval of 2τ after the initial moment, until N echo signals are collected;

[0064] Wherein, τ represents a half echo interval time, and N represents a preset echo quantity threshold.

[0065] In a specific experimental implementation process, a 90° radio frequency pulse is applied to the to-be-tested core at 0 moment; a 180° radio frequency pulse is applied at τ moment after waiting for a half echo interval TE; a complete discrete spin echo signal is collected at 2τ moment; a 180° radio frequency pulse is applied at 3τ, 5τ, …, (2n-1)τ moment, n = 1, 2, …, N; the above steps are repeated until N spin echo signals are collected at 4τ, 6τ, …, 2nτ moment, and the N spin echo signals form an echo train signal.

[0066] After each application of a 180° radio frequency pulse, the relaxation process (T1, T2) of the spin can be accurately recorded in the time domain by collecting echo signals. Through multi-time echo signal collection, more abundant space-time data can be provided for subsequent data analysis and modeling. In the data fitting and modeling process, higher precision model parameters can be obtained by utilizing the time interval information between multiple echo signals, especially in the accurate evaluation of reservoir fluid properties, porosity, permeability, etc. Especially in 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 pore, and more realistically simulate the flow characteristics of the fluid in the actual reservoir.

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

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

[0069]

[0070] In the formula, b i is the i th echo at the waiting time T wsthe amplitude of the echo; m is the transverse relaxation time T 2j the number of individual T2 relaxation times; p is the longitudinal relaxation time T 1k the number of individual fluid transit time points t r ; f(T 2j , T 1k , t r ) is a distribution function for the transverse relaxation time T 2j , the longitudinal relaxation time T 1k , and the fluid transit time point t r ; L(t r , X g ) is a function of the transit time t r and the experimental conditions X g ; Tws is the waiting time; t i is the acquisition time of the i-th echo.

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

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

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

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

[0075] As a specific example, during the experiment, the magnetic field strength was set to 0.5T (resonance frequency 21MHz), the CPMG and IR-CPMG sequences were used to acquire T1-T2 two-dimensional spectra at different transit stages, the number of echoes (NECH) was set to 12000, the number of superpositions (SCAN) was set to 16, the echo spacing (TE) was set to 0.1ms, the waiting time (TW) was set to 4000ms. The exposure time of the core transit was set to 0 hours, 1 hour, 2 hours, 4 hours, 8 hours, 16 hours, 32 hours, 64 hours, 96 hours, 160 hours, and 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 the T1-T2-t three-dimensional distribution data is visualized and analyzed, including:

[0077] The T1-T2-t three-dimensional distribution data is obtained based on the collected nuclear magnetic resonance echo data using a three-dimensional inversion algorithm;

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

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

[0080] As shown in Figure 2 , Figure 2 The generated T1-T2-t three-dimensional nuclear magnetic resonance distribution map is displayed, and each planar graph in the figure represents the T1-T2 distribution at a specific echo 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 fluid changes at different time points are displayed by different time axis translations. The color depth of each data point represents the intensity of the fluid signal, thereby achieving accurate differentiation of different fluid types (such as oil, water, and gas). At the same time, high-precision interpolation technology is used to ensure that the generated three-dimensional data map has higher spatial resolution and more detailed hierarchical structure. Through the T1-T2-t three-dimensional data, quantitative basis can be provided for the reservoir evaluation of unconventional oil and gas reservoirs.

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

[0082] In some embodiments, in order to ensure the representativeness of the experiment, the experiment will perform repeated tests on different types of cores, analyze the influence on the fluid behavior, and optimize the temperature, humidity, and time parameters of the echo simulation by comparing the experimental results with the geological model.

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

[0084] Embodiment 2

[0085] As shown in Figure 3 The embodiment also provides a device 300 applied to the three-dimensional nuclear magnetic resonance rock sample fluid experiment analysis method based on a static gradient magnetic field, which comprises a data processing module 303, and a data acquisition module 301 and an experiment environment control module 302 connected with 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 to-be-tested core, apply a magnetic field gradient, and collect nuclear magnetic resonance echo data of the to-be-tested core.

[0087] The experiment environment control module 302 is configured to provide a preset temperature and humidity environment for the to-be-tested core to simulate a formation environment.

[0088] The data processing module 303 is configured to 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 and display on the data.

[0089] As a preferred embodiment, the data acquisition module comprises 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 collect nuclear magnetic resonance echo data of the to-be-tested core.

[0093] The magnet system provides a stable static B0 magnetic field, the gradient system provides a controllable magnetic field gradient, and the radio frequency system collects signals through nuclear magnetic resonance CPMG and IR-CPMG pulse sequences.

[0094] As a specific embodiment, the experiment environment control module comprises a constant temperature and humidity box and a fluid escape 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 experiment device comprises an automatic adjusting unit.

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

[0097] In some embodiments, the data processing module further comprises a high-performance processor and a special algorithm program, which are used for generating a high-resolution T1-T2-t three-dimensional distribution thermodynamic map.

[0098] Specifically, the special algorithm program firstly performs inversion of T1, T2 relaxation time and time resolution data by using Tikhonov regularization, Levenberg-Marquardt optimization algorithm and the like, to obtain accurate T1-T2-t three-dimensional data; then performs three-dimensional reconstruction on the inversion result by using an efficient image processing algorithm (for example, fast Fourier transform (FFT), discrete wavelet transform (DWT) and the like), removes noise in the data by using Kalman filtering, SVD (singular value decomposition) and the like, and ensures high signal-to-noise ratio of the analysis result. Finally, the data points (T1-T2-t three-dimensional distribution) are converted into visual effects by using a thermodynamic 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 application combine the fluid diffusion process with the nuclear magnetic resonance T1-T2 distribution by introducing the time dimension, form three-dimensional nuclear magnetic resonance data, and thus can effectively capture the space-time variation of the complex fluid occurrence state in unconventional oil and gas reservoirs, more comprehensively represent the fluid behavior in complex formations, and provide a higher-precision technical means for tight reservoir pore characterization and fluid type identification. The application realizes comprehensive characterization of the fluid characteristics of complex reservoirs, improves the fluid identification precision and the accuracy of reservoir evaluation, breaks through the limitations of traditional nuclear magnetic resonance measurement methods, and has important application value in unconventional oil and gas reservoir (such as shale gas and tight oil and gas) reservoir evaluation and fluid identification.

[0100] The above merely describes a preferred embodiment of the application, but the protection scope of the application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the application, which should be covered within the protection scope of the application.

Claims

1. A static gradient magnetic field based three-dimensional nuclear magnetic resonance rock sample fluid experiment analysis method, characterized in that, The method comprises the following steps: The fluid saturation treatment is performed on the test core, and the treated test core is placed in a preset environment condition to simulate the fluid occurrence state in the reservoir under different diffusion time conditions; wherein, the fluid saturation treatment is performed on the test core, and the treated test core is placed in a preset environment condition, comprising: the test core in the bound water state is saturated with oil to simulate different fluid occurrence states in the reservoir; the treated test core is placed in an environment with a preset temperature and humidity for a duration of different lengths of time to simulate the diffusion process under the actual oil and gas reservoir temperature and humidity conditions; NMR experiments are respectively performed on the test core based on a static gradient magnetic field at each diffusion time point to collect NMR echo data of the test core at multiple different time points; the NMR experiments are respectively performed on the test core based on a static gradient magnetic field at each diffusion time point, comprising: at each diffusion time point, the following NMR experiment is performed on the test core based on a static gradient magnetic field: a 90° radio frequency pulse is applied to the test core at the initial moment, a 180° radio frequency pulse is applied after an interval of half echo interval τ, and then a 180° radio frequency pulse is applied every 2τ; an echo signal is collected every 2τ after the initial moment until N echo signals are collected; wherein, τ represents half echo interval time, and N represents a preset echo quantity threshold; The NMR echo data of the test core at multiple different time points are collected, comprising: In the spin echo data at each time point, the echo amplitude is represented as: Where, is the waiting time of the i-th echo The amplitude of the echo; m is the transverse relaxation time The number of; p is the longitudinal relaxation time The number of; n is the time point of fluid escape The number of is about the transverse relaxation time , the longitudinal relaxation time is , fluid escape time point The distribution function of is the escape time and experimental conditions Related functions; Tws is the waiting time; is the acquisition time of the i-th echo; Three-dimensional inversion calculation is performed on the collected 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 represent the space-time variation characteristics of the reservoir fluid; the three-dimensional inversion calculation is performed on the collected NMR echo data to obtain T1-T2-t three-dimensional distribution data, and the visual analysis is performed on the T1-T2-t three-dimensional distribution data, comprising: The T1-T2-t three-dimensional distribution data are obtained based on the collected NMR echo data by using a three-dimensional inversion algorithm; Based on the T1-T2-t three-dimensional distribution data, a three-dimensional NMR T1-T2-t distribution map is obtained by a three-dimensional visualization algorithm; further comprising: setting an effective value range according to the fluid behavior data characteristics, deleting data in the T1-T2-t three-dimensional distribution data that does not belong to the effective value range, and optimizing the visual effect.

2. The static gradient magnetic field based three-dimensional nuclear magnetic resonance rock sample fluid experiment analysis method according to claim 1, characterized in that, The NMR experiments are respectively performed on the test core based on a static gradient magnetic field at each diffusion time point to collect NMR echo data of the test core at multiple different time points, further comprising: When collecting signals each time, a multiple echo signal superposition and averaging method is used to improve the signal-to-noise ratio and data stability.

3. The static gradient magnetic field based three-dimensional nuclear magnetic resonance rock sample fluid experiment analysis method according to claim 1, characterized in that, The fluid saturation treatment is performed on the test core, and the treated test core is placed in a preset environment condition, further comprising: The pressure parameter in the preset environment condition is adjusted to simulate the influence of different underground depths on the fluid diffusion characteristics.

4. A static gradient magnetic field based three-dimensional nuclear magnetic resonance rock sample fluid experiment analysis device, characterized in that, The application discloses a static gradient magnetic field-based three-dimensional nuclear magnetic resonance rock sample fluid experiment analysis method. The data acquisition module is used for providing a stable static magnetic field and a radio frequency magnetic field for a to-be-tested rock core, applying a magnetic field gradient, and collecting nuclear magnetic resonance echo data of the to-be-tested rock core. The experiment environment control module is used for providing a preset temperature and humidity environment for the to-be-tested rock core to simulate a formation environment. The data processing module is used for performing three-dimensional inversion calculation on the collected nuclear magnetic resonance echo data to obtain T1-T2-t three-dimensional distribution data, and performing visual analysis and display on the data.

5. The apparatus of claim 4, wherein the static gradient magnetic field is configured to generate a magnetic field gradient in the z-direction of about 0.1 T / m to about 0.5 T / m. The data acquisition module comprises a magnet system, a gradient system and a radio frequency system. The magnet system is used for providing a stable static magnetic field. The gradient system is used for applying an adjustable magnetic field gradient. The radio frequency system is used for generating a radio frequency magnetic field and collecting nuclear magnetic resonance echo data of the to-be-tested rock core.

Images