A rock reservoir saturation analysis system based on nuclear magnetic resonance technology

Abstract

The present invention provides a rock reservoir saturation analysis system based on nuclear magnetic resonance technology, and relates to the technical field of rock storage saturation analysis. The rock reservoir saturation analysis system based on nuclear magnetic resonance technology includes a nuclear magnetic resonance device, a frequency selection mechanism, a temperature compensation unit, a signal processing unit and a multidimensional data analysis unit. The nuclear magnetic resonance device measures the rock in the reservoir, and the signal processing unit optimizes the signal quality and reduces environmental interference; the frequency selection mechanism adjusts the measurement frequency according to the reservoir characteristics of high salt, high mineralization or high temperature; the temperature compensation unit predicts the signal change based on the mathematical model through real-time temperature data to ensure the measurement accuracy under high temperature; the multidimensional data analysis unit combines data from different sources and improves the accuracy of rock saturation analysis through a multidimensional data model. The present invention effectively improves the measurement efficiency and accuracy in complex reservoir environments, and is of great significance to oil and gas exploration and development.

Description

Technical Field

[0001] The invention relates to the technical field of rock storage saturation analysis, and in particular to a rock reservoir saturation analysis system based on nuclear magnetic resonance technology. Background Art

[0002] In the field of oil and gas exploration and development, rock saturation analysis is a key parameter for evaluating reservoir productivity and recoverable resources. Nuclear magnetic resonance technology is a widely used method for rock saturation analysis. It infers rock saturation by measuring the relaxation time of fluid molecules in rock samples. Traditional nuclear magnetic resonance measurement technology encounters a series of challenges when facing high-salt, high-mineralization or high-temperature reservoir environments.

[0003] In high-salinity, high-mineralization reservoirs, the high ion content in the rock will cause severe electromagnetic interference to the NMR signal and degrade the signal quality; in high-temperature reservoirs, the amplitude, frequency and phase of the NMR signal will be affected, resulting in distorted measurement results; traditional NMR equipment usually uses a fixed radio frequency for measurement, which is not the best choice under complex reservoir conditions and cannot maximize the signal-to-noise ratio. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the shortcomings of the prior art, the present invention provides a rock reservoir saturation analysis system based on nuclear magnetic resonance technology, which solves the problems of how to select the nuclear magnetic resonance frequency according to the high salinity, high mineralization or high temperature conditions of the reservoir; and how to analyze the rock saturation by combining the nuclear magnetic resonance signal with the geological, chemical and physical property data of the reservoir.

[0006] (II) Technical solution

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions: a rock reservoir saturation analysis system based on nuclear magnetic resonance technology, comprising:

[0008] a nuclear magnetic resonance device for obtaining nuclear magnetic resonance signals of reservoir rocks;

[0009] a frequency selection mechanism that selects the frequency of the NMR according to the specific environment of the reservoir;

[0010] A temperature compensation unit, which measures the temperature of the rock in the reservoir through a temperature sensor and performs temperature compensation to adapt it to the high-temperature reservoir environment and ensure the measurement results;

[0011] a signal processing unit for optimizing the nuclear magnetic resonance signal to reduce the signal characteristics unique to a specific environmental reservoir through optimization;

[0012] A multidimensional data analysis unit uses the NMR signal processed by the signal processing unit in combination with the geological data, chemical data and physical property data of the reservoir as the input of the multidimensional data model to output accurate rock saturation analysis.

[0013] Preferably, rocks in the reservoir are collected, cleaned and dried, and then placed in a sample chamber of a nuclear magnetic resonance device to stabilize them and place them in a magnetic field; the magnetic field strength, radio frequency frequency and pulse sequence of the device are set according to the characteristics of the rocks in high-salinity, high-mineralization and high-temperature reservoirs; the nuclear magnetic resonance device excites hydrogen nuclei in the rock sample through radio frequency pulses to deviate from the equilibrium state; the hydrogen nuclei emit nuclear magnetic resonance signals when they relax back to the equilibrium state, and are received and recorded by the nuclear magnetic resonance device; the higher the quality of the nuclear magnetic resonance signal, the higher the fluid content of the rock, the better the fluidity of the rock pore structure, and thus the higher the rock saturation.

[0014] Preferably, the frequency selection mechanism selects a preliminary frequency range according to the characteristics of high salt, high mineralization or high temperature of the reservoir, through the nuclear magnetic resonance equipment and the specific environment of rock storage, and performs experimental measurements within the selected frequency range to analyze the signal intensity and relaxation time at different frequencies; according to the experimental results, the frequency range is adjusted to select a frequency range with high signal intensity and moderate relaxation time; the steps of experimental measurement and frequency range adjustment are repeated until the optimal frequency range is found; within the determined frequency range, a frequency scan is performed to measure the nuclear magnetic resonance signal intensity and noise level at different frequencies; the measurements at each frequency are recorded for subsequent adjustment of the nuclear magnetic resonance frequency. rate; high-salinity reservoirs increase the conductivity of rock fluids, thereby increasing the attenuation of RF pulses and reducing the penetration depth of signals. Low-frequency electromagnetic waves have less attenuation in conductive media, so low frequencies are selected to improve signal penetration; high-mineralization reservoirs contain a variety of minerals, which interfere with NMR signals and affect the intensity and resolution of NMR signals. In high-mineralization reservoirs, specific frequencies obtained through experiments are selected to reduce the impact of minerals on signals; as temperature rises, the frequency of NMR equipment will increase. In high-temperature reservoirs, higher frequencies are selected to match NMR equipment. High-frequency NMR can improve the signal-to-noise ratio of NMR signals and the sensitivity of tests.

[0015] Preferably, the temperature compensation unit measures the real-time temperature in the reservoir by using a temperature sensor, and determines the specific influence of the temperature change on the nuclear magnetic resonance signal by simulating the temperature change of the rock in the reservoir, which involves measuring the nuclear magnetic resonance signals at different temperatures, and establishing a mathematical model A(t)=a0+a1*t of the temperature influence on the nuclear magnetic resonance signal according to the influence of the temperature change of the rock in the reservoir on the nuclear magnetic resonance signal; wherein a0 represents the value of the nuclear magnetic resonance signal amplitude at the zero temperature point, a1 represents the change in the nuclear magnetic resonance signal amplitude when the temperature changes by one unit, and t is the temperature; based on the mathematical model, a temperature compensation algorithm is developed to predict the theoretical value of the nuclear magnetic resonance signal at different temperatures; during the nuclear magnetic resonance measurement process, the signal is collected in real time and preprocessed, including filtering and denoising; the collected signal is combined with the temperature compensation algorithm to calculate the equivalent value of the temperature signal of the rock in the reservoir; the corrected signal is further processed, including normalization and baseline correction; the temperature change is continuously monitored during the measurement process, and the compensation parameters are dynamically adjusted according to the real-time data to cope with the fluctuations in the amplitude, frequency and phase of the nuclear magnetic resonance signal.

[0016] Preferably, the temperature compensation algorithm establishes an algorithm framework, which receives the real-time collected nuclear magnetic resonance signal and temperature data as input; the algorithm uses the nuclear magnetic resonance signal and temperature data input to calculate the correction factor, wherein the correction factor is used to adjust the actual measurement value; based on the real-time temperature and the mathematical model, a new correction factor is calculated, and the new correction factor reflects the difference between the signal at the current temperature and the signal at the rock temperature in the reservoir; the correction factor adjusts the actual measured nuclear magnetic resonance signal by simple multiplication, and the algorithm is tested at different temperatures to verify the accuracy of the algorithm; the algorithm is integrated into the rock reservoir saturation analysis system so that the algorithm works in coordination with other parts of the rock reservoir saturation analysis system.

[0017] Preferably, the signal processing unit receives the nuclear magnetic resonance signal collected by the nuclear magnetic resonance device, and the signal processing unit identifies and distinguishes the signal characteristics caused by high salinity, high mineralization or high temperature, including the frequency components, amplitude and phase characteristics of the nuclear magnetic resonance signal; separates the noise and interference components from the original signal by wavelet transform, thereby reducing the signal characteristics unique to the high salinity, high mineralization or high temperature reservoir; in the frequency domain of the nuclear magnetic resonance signal, removes low-frequency noise and high-frequency interference by a bandpass filter, and retains the frequency components related to the rock pore structure; performs multi-scale decomposition of the nuclear magnetic resonance signal by wavelet transform, identifies and removes noise on different time scales; in the analysis of the amplitude and phase characteristics of the signal, uses statistical methods to identify outliers, which are caused by high salinity or high mineralization conditions; and improves the stability and reliability of the signal by eliminating or correcting outliers.

[0018] Preferably, the multidimensional data analysis unit obtains the processed nuclear magnetic resonance signal through the nuclear magnetic resonance equipment, eliminates noise and improves data quality after preprocessing; after data preprocessing, feature extraction is performed to identify key parameters that can represent reservoir characteristics, including relaxation time, rock pores and fluid content, and the key parameters representing reservoir characteristics are integrated with geological data, chemical data and physical property data; geological data include rock type, pore structure and permeability; chemical data involve fluid type, ion concentration and pH value; physical property data include temperature, pressure and density; a multidimensional data model created by deep learning is established based on the integration of data; data from different sources are input into the multidimensional data model for comprehensive analysis to understand the relationship between data and the impact on nuclear magnetic resonance signals, such as the impact of rock pore structure on fluid fluidity, the impact of chemical composition changes on reservoir permeability and fluid phase, and the impact of environmental conditions on nuclear magnetic resonance signals and reservoir characteristics; comprehensive analysis helps to evaluate the relationship between nuclear magnetic resonance signals and reservoir characteristics, and provide an important scientific basis for oil and gas exploration and development.

[0019] (III) Beneficial effects

[0020] The present invention provides a rock reservoir saturation analysis system based on nuclear magnetic resonance technology, which has the following beneficial effects:

[0021] 1. The present invention uses a signal preprocessing unit so that the system can identify and reduce specific signal features such as noise and interference in high-salinity, high-mineralization or high-temperature environments, thereby improving the quality of nuclear magnetic resonance signals.

[0022] 2. The present invention can select the optimal NMR frequency according to the specific environmental conditions of the reservoir and reduce the impact of complex environments on the NMR equipment. This means that the NMR equipment can be adjusted in different reservoir environments to ensure the best measurement effect, thereby improving the accuracy of rock saturation analysis. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0024] Rocks are obtained from the reservoir. These rocks are cleaned and dried to ensure the purity of the NMR signal. The rocks are placed in the sample chamber of the NMR equipment to ensure that they are stable and located in the magnetic field. According to the specific environment of the reservoir, such as high salt, high mineralization or high temperature, the magnetic field strength, radio frequency frequency and pulse sequence of the NMR equipment are set to adapt to the specific environment of the reservoir and optimize the reception of signals.

[0025] The nuclear magnetic resonance device uses radio frequency pulses to excite the hydrogen nuclei in the rock sample, causing them to deviate from the equilibrium state. When the hydrogen nuclei relax back to the equilibrium state, they emit nuclear magnetic resonance signals, which are received and recorded by the equipment. The quality of the nuclear magnetic resonance signal is directly related to the fluid content of the rock and the fluidity of the pore structure, thus affecting the assessment of rock saturation.

[0026] In order to adapt to the high salinity, high mineralization or high temperature characteristics of the reservoir, the radio frequency is selected, and a set of optimal frequency ranges are determined through experiments or theoretical analysis. Scans are performed at these frequencies to measure the intensity and noise level of the nuclear magnetic resonance signal. For example, in high-salinity reservoirs, due to the increase in the conductivity of rock fluids, low frequencies are selected to improve the penetration of the signal; in high-mineralization reservoirs, specific frequencies obtained based on experiments are selected to reduce the interference of minerals on the signal; in high-temperature reservoirs, higher frequencies are selected to match the nuclear magnetic resonance equipment to improve the signal-to-noise ratio and test sensitivity.

[0027] The temperature compensation unit plays a key role in this process. By using a temperature sensor to measure the real-time temperature in the reservoir, a mathematical model is established, which describes the impact of temperature changes on the nuclear magnetic resonance signal. Based on the mathematical model, a temperature compensation algorithm is developed to predict the theoretical value of the nuclear magnetic resonance signal at different temperatures. During the measurement process, the signal is collected in real time and preprocessed, including filtering and denoising. The collected signal is combined with the temperature compensation algorithm to calculate the equivalent value of the signal at the rock temperature in the reservoir.

[0028] The signal processing unit receives the nuclear magnetic resonance signal collected by the nuclear magnetic resonance device, and identifies and distinguishes the signal characteristics caused by high salinity, high mineralization or high temperature, including the frequency component, amplitude and phase characteristics of the nuclear magnetic resonance signal; separates the noise and interference components from the original signal by wavelet transform, thereby reducing the signal characteristics unique to the high salinity, high mineralization or high temperature reservoir; in the frequency domain of the nuclear magnetic resonance signal, removes low-frequency noise and high-frequency interference by a bandpass filter, and retains the frequency components related to the rock pore structure; performs multi-scale decomposition of the nuclear magnetic resonance signal by wavelet transform, identifies and removes noise on different time scales; in the analysis of the amplitude and phase characteristics of the signal, identifies outliers by statistical methods, and the outliers are caused by high salinity or high mineralization conditions; and improves the stability and reliability of the signal by eliminating or correcting the outliers.

[0029] The multidimensional data analysis unit obtains the processed nuclear magnetic resonance signals through the nuclear magnetic resonance equipment, and eliminates noise and improves data quality after preprocessing; after data preprocessing, feature extraction is performed to identify key parameters that can represent reservoir characteristics, including relaxation time, rock pores and fluid content, and the key parameters representing reservoir characteristics are integrated with geological data, chemical data and physical property data; geological data include rock type, pore structure and permeability; chemical data involve fluid type, ion concentration and pH value; physical property data include temperature, pressure and density; a multidimensional data model created by deep learning is established based on the integration of data; data from different sources are input into the multidimensional data model for comprehensive analysis to understand the relationship between data and the impact on nuclear magnetic resonance signals, such as the impact of rock pore structure on fluid fluidity, the impact of chemical composition changes on reservoir permeability and fluid phase, and the impact of environmental conditions on nuclear magnetic resonance signals and reservoir characteristics; comprehensive analysis helps to evaluate the relationship between nuclear magnetic resonance signals and reservoir characteristics, and provide an important scientific basis for oil and gas exploration and development.

[0030] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A rock reservoir saturation analysis system based on nuclear magnetic resonance technology, characterized in that: include: a nuclear magnetic resonance device for obtaining nuclear magnetic resonance signals of reservoir rocks; a frequency selection mechanism that selects the frequency of the NMR according to the specific environment of the reservoir; A temperature compensation unit obtains the reservoir temperature range through geological logging and performs temperature compensation to restore the reservoir ambient temperature to ensure the measurement results; A signal processing unit is used to optimize the nuclear magnetic resonance signal and reduce the signal characteristics unique to the specific environmental reservoir by optimization; A multidimensional data analysis unit, which uses the NMR signal processed by the signal processing unit combined with the geological data, chemical data and physical property data of the reservoir as the input of the multidimensional data model to output accurate rock saturation analysis; The nuclear magnetic resonance device obtains the nuclear magnetic resonance signal of the reservoir rock; the rock obtained from the reservoir is cleaned and wrapped with a film, and then placed in the sample chamber of the nuclear magnetic resonance device to stabilize it and place it in the magnetic field; the magnetic field strength, radio frequency frequency and pulse sequence of the nuclear magnetic resonance device are set according to the different characteristics of the rock in the reservoir in a specific environment, wherein the reservoir in the specific environment is high in salt, high in mineralization or high in temperature; the nuclear magnetic resonance device receives and records the nuclear magnetic resonance signal; the stronger the nuclear magnetic resonance long relaxation time signal, the better the pore structure of the rock; the higher the signal amplitude, the higher the fluid content; The frequency selection mechanism selects the frequency of the NMR device according to the characteristics of high salt, high mineralization or high temperature of the reservoir; a preliminary frequency range is selected through the specific environment of the NMR device and the rock reservoir, and experimental measurements are carried out within the selected frequency range to analyze the signal intensity and long relaxation time at different frequencies; According to the experimental results, the frequency range is adjusted to select a frequency range with high signal intensity and moderate long relaxation time; the steps of experimental measurement and frequency range adjustment are repeated until the optimal frequency range is found.

2. The rock reservoir saturation analysis system based on nuclear magnetic resonance technology according to claim 1 is characterized in that: The temperature compensation unit obtains the reservoir temperature range according to geological logging, determines the specific influence of temperature change on the nuclear magnetic resonance signal by simulating the nuclear magnetic resonance signal of the rock in the reservoir at different temperatures, and analyzes the change in the amplitude of the nuclear magnetic resonance signal caused by temperature; establishes a mathematical model A(t)=a0+a1*t of the influence of temperature on the nuclear magnetic resonance signal; wherein a0 represents the value of the nuclear magnetic resonance signal amplitude at the zero temperature point, a1 represents the change in the nuclear magnetic resonance signal amplitude when the temperature changes by one unit, and t is the temperature; based on the mathematical model, develops a temperature compensation algorithm to predict the theoretical value of the nuclear magnetic resonance signal at different temperatures; during the nuclear magnetic resonance measurement process, collects the nuclear magnetic resonance signal in real time and performs preprocessing, including filtering and denoising; combines the collected nuclear magnetic resonance signal with the temperature compensation algorithm to calculate the signal equivalent value of the rock temperature in the reservoir; further processes the corrected signal, including normalization and baseline correction; continuously monitors the temperature change during the measurement process, and dynamically adjusts the compensation parameter according to the real-time data to cope with the temperature fluctuation, wherein the compensation parameter is the correction factor calculated by the temperature compensation algorithm.

3. The rock reservoir saturation analysis system based on nuclear magnetic resonance technology according to claim 2 is characterized in that: The temperature compensation algorithm establishes an algorithm framework that receives real-time collected nuclear magnetic resonance signals and temperature data as input; the algorithm uses the nuclear magnetic resonance signal and temperature data input to calculate a correction factor, wherein the correction factor is used to adjust the actual measurement value; based on the real-time temperature and the mathematical model, a new correction factor is calculated, and the new correction factor reflects the difference between the nuclear magnetic resonance signal of the current temperature and the temperature of the rock in the reservoir; and the actually measured nuclear magnetic resonance signal is adjusted by multiplying the initial signal by the new correction factor.

4. The rock reservoir saturation analysis system based on nuclear magnetic resonance technology according to claim 1 is characterized in that: The signal processing unit receives the nuclear magnetic resonance signal collected by the nuclear magnetic resonance device, identifies and distinguishes the signal characteristics caused by the reservoir in a specific environment, separates the noise and interference components from the nuclear magnetic resonance signal by wavelet transform, thereby reducing the signal characteristics specific to the high-salinity, high-mineralization or high-temperature reservoir; in the frequency domain of the nuclear magnetic resonance signal, retains the frequency components related to the rock pore structure; identifies and removes the noise on different time scales by using wavelet transform; in the amplitude and phase characteristic analysis of the nuclear magnetic resonance signal, identifies the outliers by statistical methods, and the outliers are caused by high-salinity or high-mineralization conditions; and removes or corrects the outliers.

5. The rock reservoir saturation analysis system based on nuclear magnetic resonance technology according to claim 1 is characterized in that: The multidimensional data analysis unit obtains the reservoir rock nuclear magnetic resonance signal processed by the signal processing unit through the nuclear magnetic resonance equipment, and identifies the key parameters representing the reservoir characteristics, including long relaxation time, rock pores and fluid content, by extracting features from the nuclear magnetic resonance signal; integrates the key parameters representing the reservoir characteristics with geological data, chemical data and physical property data; the geological data includes rock type, pore structure and permeability; the chemical data involves fluid type, ion concentration and pH value; the physical property data includes temperature, pressure and density; establishes a multidimensional data model based on the integration of data; and comprehensively analyzes data from different sources to understand the relationship between the data and the impact on the nuclear magnetic resonance signal.