CN116068006A - An experimental system and method for nuclear magnetic resonance core measurement - Google Patents

Abstract

The invention relates to a nuclear magnetic resonance core measurement experiment system and method, wherein the system comprises a computer control system, a continuous high-pressure system, a high-temperature circulation system, an auxiliary cooling system, a core holder, a high-temperature high-pressure probe, a low-field nuclear magnetic resonance core analyzer and a circulating liquid collection container, wherein the computer control system is electrically connected with the continuous high-pressure system, the high-temperature circulation system and the auxiliary cooling system; the continuous high-pressure system is connected with the high-temperature circulating system; the high-temperature circulating system is used for providing stable temperature for the inside of the core holder; the auxiliary cooling system is used for assisting in reducing the temperature of the high-temperature high-pressure probe; the core holder is fixed on the high-temperature high-pressure probe; the high-temperature high-pressure probe part is arranged in the cavity of the low-field nuclear magnetic resonance core analyzer; the circulating liquid collecting container is used for recovering experimental waste liquid. The nuclear magnetic resonance core measurement experiment system and method can simulate the underground high-temperature high-pressure environment and dynamically adjust the underground high-temperature high-pressure environment.

Description

An experimental system and method for nuclear magnetic resonance core measurement

technical field

The invention belongs to the field of oil and gas exploration and development, and in particular relates to a dynamic adjustment-based nuclear magnetic resonance core measurement experiment system and method for simulating an underground high-temperature and high-pressure environment.

Background technique

As an important technical means, nuclear magnetic resonance has been widely used in the field of oil and gas detection after decades of development. Its core experiment analysis and fast downhole nuclear magnetic resonance measurement have important application value for the evaluation of conventional and unconventional reservoirs. It can provide important reservoir evaluation parameters such as porosity, permeability, and oil saturation. Its non-destructive and fast characteristics are favored by front-line oil and gas workers and researchers. With the advancement of drilling technology and the development of deep and ultra-deep oil and gas reservoirs, new requirements are constantly put forward for existing instruments and equipment. With the increase of formation depth, the formation temperature and pressure will also increase, and its temperature and pressure may have a certain impact on the properties of pore fluids. Therefore, it is very urgent to vigorously develop the matching high temperature and high pressure experimental system.

After a lot of investigation and practice, it is found that the design temperature of the existing high-temperature or high-pressure nuclear magnetic resonance experimental equipment is mostly above 100°C, the design pressure is mostly above 35MPa, and fluorine oil is mostly used for the confining pressure circulating fluid. The circulating fluid adopts perfluorinated oil without nuclear magnetic signal, its boiling point is about 155°C, and its coefficient of thermal expansion is positive, that is, the volume increases when the temperature rises. The expansion coefficient of fluorine oil is very large, and the system pressure will increase rapidly by several degrees with the increase of temperature. Ten MPa, in this way, the internal pressure of the system is too high instantaneously, which may exceed the tolerance range of the instrument, resulting in the problems of reduced instrument life and low experimental safety. At the same time, it is also found through practice that during the experiment, the temperature of the fluid at the inlet of the core holder is often higher than the design temperature of the experiment, and heat conduction will lead to an increase in the temperature of the RF coil and magnet of the low-field NMR core analyzer. The radio frequency coil itself has a lot of power when it works, and the magnet also needs to work under constant temperature conditions. Since the magnetism of the magnet will be affected by the temperature, it needs to be maintained at 35°C, and the temperature deviation will cause the main frequency to shift, thus affecting the experimental measurement results.

Contents of the invention

In order to solve all or part of the above problems, the object of the present invention is to provide a nuclear magnetic resonance core measurement experiment system and method, which can simulate the downhole high temperature and high pressure environment, and can dynamically adjust the downhole high temperature and high pressure environment.

According to the first aspect of the present application, a nuclear magnetic resonance core measurement experiment system is provided, including a computer control system, a continuous high-pressure system, a high-temperature circulation system, an auxiliary cooling system, a core holder, a high-temperature and high-pressure probe, and a low-field nuclear magnetic resonance core Analyzer, circulating fluid collection container, wherein: the computer control system is electrically connected with the continuous high-pressure system, high-temperature circulation system, and auxiliary cooling system for controlling each system; the continuous high-pressure system is connected with the high-temperature circulation system and used for core The inside of the holder provides a stable confining pressure, and at the same time, it is used for the displacement experiment of the core in the core holder; the high temperature circulation system is used to provide a stable temperature inside the core holder; the auxiliary cooling system is used to assist in reducing The temperature of the high-temperature and high-pressure probe; the core holder is fixed on the high-temperature and high-pressure probe for placing the core sample; the high-temperature and high-pressure probe is partly set in the cavity of the low-field nuclear magnetic resonance core analyzer for replacing the core sample required for the experiment; The circulating liquid collection container is used for the recovery of experimental waste liquid.

In some embodiments, the continuous high-pressure system includes a continuous confining pressure system, and the continuous confining pressure system includes a confining pressure liquid container, a confining pressure system intermediate container, a hydraulic oil container, and two confining pressure system constant speed and constant pressure pumps, wherein: the confining pressure The liquid container is sequentially connected to the first manual valve, the pneumatic valve and the intermediate container of the confining pressure system through the pipeline; the liquid outlet of the intermediate container of the confining pressure system is divided into the first road and the second road. The oil container is connected, and the second road is further divided into two roads. The two roads are respectively connected to the liquid inlets of the constant speed and constant pressure pumps of the two confining pressure systems through pneumatic valves, and the liquid replenishment ports of the two constant speed and constant pressure pumps of the confining pressure systems are passed through. The pipeline is connected to the hydraulic oil container; the first manual valve is connected to the confining pressure inlet of the core holder through the confining pressure pipeline, and a pressure sensor is arranged on the confining pressure pipeline.

In some embodiments, the continuous high-pressure system further includes a continuous displacement system, and the continuous displacement system includes a displacement liquid container, an intermediate container of the displacement system, and two constant-speed and constant-pressure pumps of the displacement system, wherein: the displacement liquid container passes through The pipeline is connected to the third manual valve, the pneumatic valve and the intermediate container of the displacement system in sequence; the liquid outlet of the intermediate container of the displacement system is divided into the third and fourth channels, and the third channel is connected to the hydraulic oil container through the fourth manual valve. The fourth road is further divided into two roads, the two roads are respectively connected to the liquid inlets of the two displacement system constant speed and constant pressure pumps through pneumatic valves, and the liquid replenishment ports of the two displacement system constant speed and constant pressure pumps are connected to the hydraulic oil through pipelines. The container is connected; the third manual valve is connected with the displacement inlet of the core holder through a displacement pipeline, and a pressure sensor is arranged on the displacement pipeline.

In some embodiments, the third manual valve, the pneumatic valve, and the intermediate container of the displacement system, which are sequentially connected to the displacement fluid container through pipelines, are all detachable.

In some embodiments, the high-temperature circulation system includes a high-temperature circulation pump, a constant temperature oil bath heater, and a three-way pneumatic ball valve, wherein: the confining pressure outlet of the continuous high-pressure system is sequentially connected to the fifth manual valve, the high-temperature circulation pump, and the constant temperature oil bath through pipelines Heater, back pressure valve, three-way pneumatic ball valve, sixth manual valve, a temperature sensor is installed on the pipeline between the confining pressure outlet of the continuous high pressure system and the fifth manual valve, and a temperature sensor is installed between the constant temperature oil bath heater and the back pressure valve. A temperature sensor and a pressure sensor are arranged on the pipeline, and a pressure sensor and a temperature sensor are arranged on the pipeline between the sixth manual valve and the confining pressure inlet of the continuous high pressure system.

In some embodiments, the circulating fluid collection container is arranged respectively under the confining pressure outlet of the core holder, the displacement outlet of the core holder, and the three-way pneumatic ball valve of the high temperature circulation system, wherein the surrounding pressure of the core holder The pressure outlet is also provided with a seventh manual valve; the displacement outlet of the core holder is also provided with a back pressure valve, an eighth manual valve and a balance; the three-way pneumatic ball valve is connected to the circulating fluid collection container through a pipeline.

In some embodiments, the auxiliary cooling system includes: two gradient coils and magnet groups, respectively arranged at intervals on both sides of the high temperature and high pressure probe; two temperature sensors, respectively used to measure the temperature of the two gradient coils and magnet groups; The machine extends through pipelines to the gap between the high temperature and high pressure probe and the two gradient coils and magnet groups.

In some embodiments, the core holder includes: a heat-shrinkable tube with a core sample inside, and the two ends of the heat-shrinkable tube are sealed by a core plunger, and the core plunger is provided with a sealing rubber ring for sealing connection and gasket; the core plunger is connected with a displacement pipeline; wherein, the high-temperature and high-pressure probes are arranged at intervals and in parallel on both sides of the heat-shrinkable tube, and the two ends of the high-temperature and high-pressure probes on both sides are sealed and connected through plugs, so that both sides A sealed cavity is formed between the high-temperature and high-pressure probes, and the plugs on both sides are respectively provided with a confining pressure outlet and a confining pressure inlet; The plug is fixed with the plug by the sealing bolt.

In some embodiments, the high temperature and high pressure probe is detachably arranged in the cavity of the low field nuclear magnetic resonance core analyzer.

According to the second aspect of the present application, a kind of nuclear magnetic resonance rock core measurement experimental method is provided, which is applied to the above-mentioned nuclear magnetic resonance rock core measurement experimental system. The nuclear magnetic resonance rock core measurement experimental method includes: step 1, preparing a standard plunger core sample, and performing a test on the core Sample pretreatment; Step 2, low-field NMR core analyzer calibration and measurement parameter setting; Step 3, installing core samples; Step 4, pressure test and pipeline tightness detection; Step 5, pressurization and heating experiment; Step 6 , displacement experiment; Step 7, data processing of nuclear magnetic resonance experiment.

In some embodiments, step five further includes:

Set confining pressure and temperature;

The system rises to the target pressure with the preset pressure gradient, and judges whether the target confining pressure is reached, and if not, continues to raise the pressure;

The system raises the oil bath to the target temperature with the preset temperature gradient, and judges whether the temperature of the oil bath heater reaches the target temperature, and if not, continues to heat up;

Determine whether the system pressure is stable, if so: determine whether the inside of the core holder reaches the target temperature, if not, release or replenish pressure, or determine whether the circulation pump reaches the maximum speed; further: if the circulation pump reaches the maximum speed, the oil The bath continues to heat up or cool down with a preset temperature gradient;

Judging whether the system pressure is stable, if not: pressure relief or supplementary pressure;

Judging the change range of the internal temperature of the core holder within a preset time, if not, the oil bath continues to heat up or cool down with a preset temperature gradient; if so, start the nuclear magnetic resonance measurement test.

It can be seen from the above technical scheme that the NMR core measurement experiment system and method for simulating the downhole high-temperature and high-pressure environment of the present invention provide a method and system for NMR evaluation of high-temperature and high-pressure reservoirs. played an important role.

Description of drawings

Fig. 1 is the system connection schematic diagram of the nuclear magnetic resonance rock core measurement experiment system of the embodiment of the present invention;

Fig. 2 is the system connection schematic diagram of the continuous high pressure system of the embodiment of the present invention;

Fig. 3 is a schematic diagram of the system connection of the high temperature circulation system of the embodiment of the present invention;

4 is a schematic diagram of the system connection of the auxiliary cooling system of the embodiment of the present invention;

Fig. 5 is the structural representation of the core holder of the embodiment of the present invention;

Fig. 6 is the schematic flow sheet of the nuclear magnetic resonance rock core measurement experimental method of the embodiment of the present invention;

Fig. 7 is a flow chart of the method of the pressurization and heating experiment of the embodiment of the present invention.

Detailed ways

In order to better understand the purpose, structure and function of the present invention, a nuclear magnetic resonance core measurement experimental system simulating the downhole high temperature and high pressure environment of the present invention will be further described in detail in conjunction with the accompanying drawings.

FIG. 1 is a schematic diagram of the system connection of a nuclear magnetic resonance core measurement experimental system 100 according to an embodiment of the present invention. As shown in Fig. 1, the nuclear magnetic resonance core measurement experiment system 100 includes a computer control system 1, a continuous high-pressure system 2, a high-temperature circulation system 3, an auxiliary cooling system 4, a core holder 5, a high-temperature and high-pressure probe 7, a low-field nuclear magnetic Resonance core analyzer 8, circulating fluid collection container 6, wherein: computer control system 1 is electrically connected with continuous high-pressure system 2, high-temperature circulation system 3, and auxiliary cooling system 4, so as to control each system; continuous high-pressure system 2 and The high temperature circulation system 3 is connected, and is used to provide a stable confining pressure inside the core holder 5, and at the same time, is used to carry out a displacement experiment on the rock core in the core holder 5; the high temperature circulation system 3 is used to hold the core The interior of the device 5 provides a stable temperature; the auxiliary cooling system 4 is used to assist in reducing the temperature of the high-temperature and high-pressure probe 7; the core holder 5 is fixed on the high-temperature and high-pressure probe 7 for placing rock core samples; The cavity of the nuclear magnetic resonance core analyzer 8 is used to replace the core samples required for the experiment; the circulating fluid collection container 6 is used for the recovery of the experimental waste liquid.

The computer control system 1 mentioned in this application is connected with the continuous high-pressure system 2, the high-temperature circulation system 3 and the auxiliary cooling system 4 through cables, and is used to set parameters such as temperature, pressure, and the speed of the high-temperature circulation pump 31, and select the pressure mode , control the pneumatic valve 201 on each system, monitor the pressure and temperature on each node, and dynamically control the temperature and pressure in the system during the heating process through a certain feedback mechanism.

Fig. 2 is a schematic diagram of the system connection of the continuous high pressure system 2 of the embodiment of the present invention. As shown in FIG. 2 , in some embodiments, the continuous high pressure system 2 may include a continuous confining pressure system, and the continuous confining pressure system includes a confining pressure liquid container 21, a confining pressure system intermediate container 22, a hydraulic oil container 23 and two confining pressure System constant speed and constant pressure pump 24, wherein: the confining pressure liquid container 21 is sequentially connected to the first manual valve 25, the pneumatic valve 201 and the intermediate container 22 of the confining pressure system through the pipeline; the liquid outlet of the intermediate container 22 of the confining pressure system is divided into the first The first road and the second road, the first road is connected with the hydraulic oil container 23 through the second manual valve 26, the second road is further divided into two roads, and the two roads pass through the pneumatic valve 201 and two constant-speed constant-pressure pumps of the confining pressure system respectively. 24 is connected to the liquid inlet, and the liquid replenishment ports of the two constant-speed constant-pressure pumps 24 of the confining pressure system are connected to the hydraulic oil container 23 through the pipeline; the first manual valve 25 is connected to the confining pressure inlet of the core holder 5 through the confining pressure pipeline , a pressure sensor 202 is arranged on the confining pressure pipeline.

Continuing to refer to Fig. 2, in some embodiments, the continuous high-pressure system 2 can also include a continuous displacement system, and the continuous displacement system includes a displacement liquid container 27, a displacement system intermediate container 28, and two displacement system constant speed Constant pressure pump 29, wherein: the displacement liquid container 27 is connected to the third manual valve 211, the pneumatic valve 201 and the intermediate container 28 of the displacement system in sequence through pipelines; the liquid outlet of the intermediate container 28 of the displacement system is divided into the third path and the second Four routes, the third route is connected with the hydraulic oil container 23 through the fourth manual valve 212, the fourth route is further divided into two routes, and the two routes respectively pass through the pneumatic valve 201 and the liquid inlet of the two displacement system constant speed and constant pressure pumps 29 The fluid replenishment port of the constant speed and constant pressure pump 29 of the two displacement systems is connected with the hydraulic oil container 23 through the pipeline; the third manual valve 211 is connected with the displacement inlet of the core holder 5 through the displacement pipeline, and the displacement pipeline A pressure sensor 202 is provided on it.

In this application, the continuous high-pressure system 2 includes two parts: a continuous confining pressure system and a continuous displacement system. Both systems are controlled by the computer control system 1 and connected to the high-temperature circulation system 3. The inside of the holder 5 provides a stable confining pressure, and the continuous displacement system is used for continuous displacement experiments on the core.

In the continuous confining pressure system in this application, the confining pressure fluid container 21 is filled with liquid, which is used to replenish the confining pressure system intermediate container 22 during the experiment preparation stage, and the confining pressure system intermediate container will be driven when the confining pressure fluid is replenished. The piston in 22 moves downwards. The intermediate container 22 of the confining pressure system is connected with the hydraulic oil container 23 through the second manual valve 26, and is used to supplement the hydraulic oil in the intermediate container 22 of the confining pressure system during the boost stage, and the intermediate container 22 of the confining pressure system is connected with the hydraulic oil container 23 through the pneumatic valve Two confining pressure system constant speed and constant pressure pumps 24 are connected to provide stable and continuous pressure to the intermediate container 22 of the confining pressure system, and the confining pressure system constant speed and constant pressure pump 24 is connected to the hydraulic oil container 23 through pipelines for supplementing hydraulic oil ; The confining pressure outlet of the continuous confining pressure system is connected with the confining pressure inlet of the pressure sensor 202 and the core holder 5 through a pipeline.

In the continuous displacement system in this application, the displacement liquid container 27 is filled with liquid, which is used to replenish the confining pressure liquid to the intermediate container 28 of the displacement system during the experimental preparation stage, and the intermediate container of the displacement system will be driven when the displacement liquid is replenished The piston in 28 moves downward; the displacement system intermediate container 28 is connected with the hydraulic oil container 23 through the fourth manual valve 212, and is used to replenish hydraulic oil to the displacement system intermediate container 28 during the displacement boosting stage, and the displacement system The intermediate container 28 is connected with two displacement system constant speed and constant pressure pumps 29 through a pneumatic valve 201 to provide stable and continuous pressure for the displacement system intermediate container 28. The two displacement system constant speed and constant pressure pumps 29 communicate with each other through pipelines. The hydraulic oil container 23 is connected to replenish hydraulic oil; the displacement outlet of the continuous displacement system is connected with the pressure sensor 202 and the displacement inlet of the core holder 5 through pipelines.

In some embodiments, the constant speed and constant pressure pump 24 of the confining pressure system and the constant speed and constant pressure pump 29 of the displacement system are further connected with another hydraulic oil container 23 .

In some embodiments, the third manual valve 211 , the pneumatic valve 201 , and the intermediate container 28 of the displacement system, which are sequentially connected to the displacement fluid container 27 through pipelines, are configured to be detachable. With this arrangement, other displacement fluids can be easily replaced.

Fig. 3 is a schematic diagram of the system connection of the high temperature circulation system 3 of the embodiment of the present invention. As shown in FIG. 3 , in some embodiments, the high temperature circulation system 3 may include a high temperature circulation pump 31 , a constant temperature oil bath heater 32 , and a three-way pneumatic ball valve 33 . Among them: the confining pressure outlet of the continuous high-pressure system 2 is connected to the fifth manual valve 34, the high-temperature circulation pump 31, the constant temperature oil bath heater 32, the back pressure valve 301, the three-way pneumatic ball valve 33, and the sixth manual valve 35 through pipelines, continuously A temperature sensor 302 is provided on the pipeline between the confining pressure outlet of the high pressure system 2 and the fifth manual valve 34, a temperature sensor 302 and a pressure sensor 202 are provided on the pipeline between the constant temperature oil bath heater 32 and the back pressure valve 301, A pressure sensor 202 and a temperature sensor 302 are arranged on the pipeline between the sixth manual valve 35 and the confining pressure inlet of the continuous high pressure system 2 .

In this application, the high-temperature circulation system 3 is used to provide a stable temperature inside the core holder 5 , which receives the control of the computer control system 1 and is connected with the continuous high-pressure system 2 . The temperature sensor 302 is used to monitor the temperature at the high temperature circulation inlet (confined pressure outlet), the oil bath heating and the high temperature circulation outlet (confined pressure inlet) respectively. The back pressure valve 301 is set to ensure the safety of the experiment. The three-way pneumatic ball valve 33 and the back The pressure valve 301 is used to release the pressure generated during the heating process of the system.

Please refer to Figures 1 to 3, in some embodiments, the circulating fluid collection container 6 can be respectively arranged at the confining pressure outlet of the core holder 5, the displacement outlet of the core holder 5, and the high temperature circulation system 3. Below the three-way pneumatic ball valve 33, wherein, the confining pressure outlet of the core holder 5 can also be provided with a seventh manual valve 213; the displacement outlet of the core holder 5 can also be provided with a back pressure valve 301, an eighth manual valve The valve 214 and the balance 215; the three-way pneumatic ball valve 33 are connected to the circulating liquid collection container 6 through pipelines. With this setting, the set circulating fluid collection container 6 can be used to recover the liquid after the experiment is over. The liquid can be the confining pressure liquid in the continuous confining pressure system, the displacement liquid in the continuous displacement system, or it can be simulated downhole high temperature After the nuclear magnetic resonance core measurement experimental system in a high-pressure environment is released and cooled, the fluid stored in the pipeline and the core holder 5, that is, the fluorine oil used in the experiment and various waste liquids are recovered.

Fig. 4 is a schematic diagram of the system connection of the auxiliary cooling system 4 according to the embodiment of the present invention. As shown in FIG. 4, in some embodiments, the auxiliary cooling system 4 may include: two gradient coils and magnet groups 41, which are respectively arranged on both sides of the high temperature and high pressure probe 7 at intervals; two temperature sensors 302, which are respectively used for measuring The temperature of the two gradient coils and the magnet group 41 ; the refrigerator 42 respectively extends to the gap 43 between the high temperature and high pressure probe 7 and the two gradient coils and the magnet group 41 .

The auxiliary cooling system 4 of the present application is used to assist in lowering the temperature of the gradient coil and the magnet group 41 in the low-field nuclear magnetic resonance core analyzer 8 , which is controlled by the computer control system 1 . The refrigerator 42 can be logically controlled by two high-precision infrared temperature sensors 302, the measured gradient coil and the temperature of the magnet group 41, and the refrigerator 42 can stably output gas at about 35°C through the pipeline (the problem of the gas can be determined according to specific needs Controlled by the refrigerator 42), the gas passes through the pipeline to the gap 43 between the probe, the gradient coil and the magnet group 41, thereby cooling the gradient coil and the magnet group 41 to play the role of auxiliary cooling.

In some embodiments, the low-field nuclear magnetic resonance core analyzer 8 adopts a core analyzer 8 with a main frequency of 2 MHz.

In some embodiments, the high temperature and high pressure probe 7 is detachably arranged in the cavity of the low field nuclear magnetic resonance core analyzer 8 .

Fig. 5 is a schematic structural view of a core holder 5 according to an embodiment of the present invention. As shown in FIG. 5 , in some embodiments, the core holder 5 includes: a heat-shrinkable tube 59, in which a core sample 55 is arranged, and the two ends of the heat-shrinkable tube 59 are sealed by a core plunger 54, and the core plunger 54 is provided with a sealing rubber ring and a gasket for sealing connection; the core plunger 54 is connected with a displacement pipeline 57; The two ends of 7 are sealed and connected by plugs 53, so that a sealed cavity 511 is formed between the high temperature and high pressure probes 7 on both sides, and the plugs 53 on both sides are respectively provided with a confining pressure outlet 58 and a confining pressure inlet 513; Wherein, the plug 53 is also provided with a pressure gauge 52 , a temperature sensor 302 and a pressure relief valve 512 , and the displacement pipeline 57 passes through the plug 53 and is fixed with the plug 53 by the sealing bolt 51 .

In this application, the core holder 5 is fixed on the high temperature and high pressure probe 7 . The rock core holder 5 is constructed to withstand high temperature and high pressure. The rock core holder 5 is used to place rock core samples during the experiment, and its inside can accommodate two different diameters of 1 inch (about 2.5 cm) and 1.5 inches (about 3.8 cm). Standard core samples of the same size.

In this application, the high-temperature and high-pressure probe 7 is placed in the cavity of the low-field nuclear magnetic resonance core analyzer 8 and is configured to be detachable, so as to replace the core samples required for the experiment. The high-temperature and high-pressure probe 7 needs to be connected with the spectrometer part of the low-field nuclear magnetic resonance core analyzer 8 through joints and wiring.

In this application, the low-field nuclear magnetic resonance core analyzer 8 can use a core analyzer 8 with a main frequency of 2 MHz, which has a large internal cavity and is specially optimized for high-temperature and high-pressure experiments.

FIG. 6 is a schematic flowchart of an experimental method 200 for nuclear magnetic resonance core measurement according to an embodiment of the present invention. A nuclear magnetic resonance core measurement experiment method 200 for simulating an underground high temperature and high pressure environment will be specifically provided below in combination with the above-mentioned nuclear magnetic resonance core measurement experiment system 100 . The nuclear magnetic resonance core measurement experimental method 200 for simulating the downhole high temperature and high pressure environment specifically includes:

Step 1 S01, preparing a standard plunger core sample, and performing pretreatment on the core sample;

In some embodiments, step 1 S01 further includes: making the core into a standard size core sample; numbering the core sample, and measuring the rock sample volume and gas porosity of the core sample; Salt treatment; drying in a constant temperature box until constant weight; put the prepared core sample into a vacuum saturator, and put it into a container filled with a corresponding saturated solution for sealed storage after saturation.

Concrete: the artificial core is made into a standard size core sample with a diameter of 38mm (1.5in) or 25.4mm (1in) and a length of 30-100mm. The surface of the sample should be smooth and smooth, and the sample number is used to measure the volume of the rock sample. The porosity is measured by air, and then the standard core sample is washed with oil and salt, and then put into a constant temperature box to dry until it reaches a constant weight, and then prepare a solution of 20000ml of the required solute according to the salinity of the solution required for the experiment. Put the core sample prepared above into a vacuum saturator. In order to ensure that the sample is fully saturated, the vacuuming time should not be less than 8 hours, and the saturation pressurization time should not be less than 48 hours. For low-porosity and low-permeability core samples, the above time It should be grown according to the situation. After the saturation is completed, put it in a container filled with the corresponding saturated solution and store it tightly.

Step 2 S02, calibration of the low-field nuclear magnetic resonance core analyzer 8 and setting of measurement parameters;

In some embodiments, step 2 S02 further includes: adjusting the center position of the magnetic field so that the optimum resonance frequency of the probe is consistent with the nuclear magnetic resonance frequency; placing a core sample, and adjusting the nuclear magnetic resonance offset value, pulse width and amplitude using a free decay pulse sequence ; Carry out pre-measurement on the rock core samples with the same or similar physical parameters to determine the corresponding experimental measurement parameters; usually set the echo interval and the number of points for the acquisition parameters of the core samples; set the magnetic field gradient for the acquisition parameters of the diffusion time of the core samples.

Specifically: adjust the center position of the magnetic field so that the best resonance frequency of the probe is consistent with the nuclear magnetic resonance frequency, put in the standard sample and use the free decay pulse sequence to adjust the nuclear magnetic resonance offset value O1 and 90°, 180° pulse width and amplitude, for the same or Pre-measure the T2, T1, diffusion coefficient, etc. of the core sample with similar physical parameters to determine the corresponding experimental measurement parameters. For the acquisition parameters of the core sample T2, the echo interval is usually set to ≤0.2, and the complete recovery time depends on the pore structure and the nature of the saturated fluid. It was decided that the number of echoes should be set on the principle of enhancing the resolution of long relaxation components, and the number of repetitions and gain should be set on the principle of ensuring that the signal-to-noise ratio is above 100; for the acquisition parameters of core sample T1, the number of points usually set is not low For 10, the shortest time should be 0.05ms, the longest time should be greater than 5 times of T1, and the recovery time should also be greater than the recovery time of T2 measurement; for the acquisition parameters of core sample diffusion time, the minimum magnetic field gradient is usually set not less than 0.058 T/m, other parameters can be set as appropriate with reference to the corresponding parameters measured by T2 and T1.

Step 3 S03, install the core sample;

In some embodiments, step 3 S03 further includes: placing the saturated core sample between two core plungers; wrapping the core sample and the core plunger with a heat-shrinkable tube, heating the heat-shrinkable tube until the heat-shrinkable tube, The core sample and the core plunger are fully fitted; the 5 lower plugs of the core holder are installed, so that the displacement pipeline on the core plunger passes through the pipeline channel of the lower plug, and after fixing, the 5 upper plugs of the core holder are installed. And adjust the position of the rock core up and down to the middle of the rock core holder 5; after the rock core sample is installed, the high temperature and high pressure probe 7 is installed in the instrument cavity and fixed, and at the same time, connect the power supply, transmitting, and receiving line ports; The analyzer 8 operates the measurement FID for signal testing.

Specifically: put the saturated core sample between the two core plungers, measure its length, then cut a heat-shrinkable tube slightly longer than the length of the rock sample plus the two plungers, wrap the rock sample and the plunger, and then use the setting The electric heat gun with a temperature not exceeding 200°C heats the heat-shrinkable tube evenly and slowly until the heat-shrinkable tube is completely attached to the rock sample and the plunger. Make the displacement pipeline on the plunger pass through the pipeline channel of the lower plug, install the upper plug of the core holder 5 after fixing it, and then adjust the position of the core up and down to the middle of the core holder 5 to ensure that the rock sample All are located between the radio frequency coil and the magnet and can obtain the maximum measurement signal. After the core sample is installed, the high temperature and high pressure probe 7 is installed in the instrument cavity, the fixing bolts are fixed, and the power supply, transmitting and receiving line ports are connected. The field nuclear magnetic resonance core analyzer 8 is operated to measure the FID for signal testing.

Step 4 S04, pressure test and pipeline tightness detection;

In some embodiments, step 4 S04 further includes: maintaining the normal temperature of the confining pressure fluid, increasing the fixed pressure until the confining pressure reaches a preset range higher than the pressure required by the experimental design, and maintaining the pressure at the maximum pressure Not less than twice the time required for nuclear magnetic experiment measurement; observe whether there is any leakage at all pipelines and joints, and at the same time observe whether the readings of each pressure monitoring point have an instantaneous change higher than the preset value. Or if the pressure value changes within the preset range, stop the pressure test and perform pressure relief for troubleshooting.

Specifically: During the pressure test, the whole process is operated on the computer system side, without increasing the temperature, maintaining the normal temperature of the confining pressure fluid, and increasing the pressure by 1-5MPa each time until the confining pressure value reaches a pressure slightly higher than the pressure required by the experimental design. And keep the pressure at the maximum pressure for not less than 2 times the time required for the nuclear magnetic test measurement. During the pressure test, pay close attention to whether there is any leakage at all pipelines and interfaces of the system, and observe whether the readings of each pressure monitoring point are instantaneous. If there is a change higher than 0.1MPa, if there is a liquid leakage or a large change in the pressure value, the pressure test should be stopped immediately and the pressure should be released, and the leak point should be checked immediately, and parts should be replaced or replaced at the leak. Plugging, it is recommended to reduce the pressure by 1-5MPa each time when releasing the pressure. Excessive pressure relief speed may cause the continuous displacement pump to fail. Proceed to the next step.

Step 5 S05, pressurization and heating experiment;

Please refer to FIG. 7, in some embodiments, Step 5 S05 further includes:

Set the confining pressure and temperature, the system rises to the target pressure with the preset pressure gradient, and the preset pressure can be 1-5MPa. Determine whether the target confining pressure is reached, if not, continue to increase the pressure; if so, set the temperature. The system raises the oil bath to the target temperature with a preset temperature gradient, and the preset temperature can be 1-5°C. Determine whether the temperature of the oil bath heater reaches the target temperature, if not, continue to raise the oil bath to the target temperature with the preset temperature gradient;

Determine whether the system pressure is stable, if so: determine whether the inside of the core holder reaches the target temperature, if not, release or replenish pressure, or determine whether the circulation pump reaches the maximum speed; further: if the circulation pump reaches the maximum speed, the oil The bath continues to heat up or cool down with a preset temperature gradient, the preset temperature can be 1°C; judge whether the system pressure is stable, if not: release or replenish pressure;

Judging the change range of the internal temperature of the core holder within a preset time, the change range can also be set to: change within 1 minute ≤ 0.2°C. If not, the oil bath continues to heat up or cool down with a preset temperature gradient, the preset temperature may be 1° C.; if so, start the nuclear magnetic resonance measurement test.

Specifically: when conducting high-temperature and high-pressure experiments, the whole process can be operated on the computer system side. First, set the back pressure valve 301 higher than the experimental design pressure 5MPa, and then set the system confining pressure to the pressure required for the experimental design, and then set the laboratory. Need temperature, computer control system 1 can automatically adjust the temperature of constant temperature oil bath heater 32 and the rotating speed of high temperature circulation pump 31, raise the temperature of constant temperature oil bath heater 32 and the rotating speed of high temperature circulation pump 31 can make core holder 5 The internal temperature increases, and as the temperature rises, the fluorine oil will gradually expand and increase the internal pressure of the system. At this time, the continuous high-pressure system 2 will automatically perform a depressurization operation because it detects that the pressure exceeds the set value, but its depressurization Efficiency is very limited, so there is an automatic control system integrated in the computer control system 1 to dynamically adjust the internal pressure and temperature of the core holder 5. The working logic is that after the temperature required for the experimental design is set in the system, the system The internal temperature of the core holder 5 will not be raised immediately, but the temperature of the constant temperature oil bath heater 32 and the speed of the high temperature circulation pump 31 will be gradually increased. When the pressure sensor 202 detects that the pressure rise exceeds 0.1MPa, the tee will be opened automatically When the pneumatic valve 201 releases the pressure, the internal pressure of the system will decrease. When the internal pressure of the system decreases beyond the set value of 0.1MPa, the pneumatic valve 201 will be automatically closed, and the temperature can be cycled up and down in this way. Dynamically adjust the internal pressure of the core holder 5 in real time. After reaching the required pressure and temperature for the experiment, the low-field nuclear magnetic resonance core analyzer 8 can be used to record the one-dimensional T2 spectrum, T1 spectrum, diffusion coefficient, two-dimensional T1- T2 spectrum, D-T2 spectrum, etc., to determine the original condition of the internal fluid.

Step 6 S06, displacement experiment;

In some embodiments, step 6 S06 further includes: setting the differential pressure between displacement and confining pressure to not exceed a preset value; selecting a displacement liquid, opening a valve, and continuously displacing fluid with a preset multiple of pore volume to achieve complete Flooding: observe the volume of the displacement fluid, the weight of the displaced fluid, and use the low-field nuclear magnetic resonance core analyzer 8 to record the relevant parameters of the core sample to determine the fluid migration inside the rock sample.

Specifically: set the pressure difference between displacement and confining pressure to not exceed 2MPa, select a certain displacement liquid, open the valve, and continuously displace the fluid twice the pore volume. Instead of the weight of the discharged fluid, use the low-field nuclear magnetic resonance core analyzer 8 to record the one-dimensional T2 spectrum, T1 spectrum, diffusion coefficient, two-dimensional T1-T2 spectrum, D-T2 spectrum, etc. of the core sample to determine the fluid movement inside the rock sample. Move the situation. The displaced fluid is treated as waste liquid, and the high-precision constant-speed constant-pressure pump can calculate the volume of the displaced fluid.

Step 7 S07, NMR experiment data processing.

In some embodiments, step 7 S07 further includes: after the measurement is completed, the processing program processes the result; after the result is processed, save relevant data and pictures, and write a test report.

Specifically: after the measurement is completed, the processing program will calculate the one-dimensional T2, T1 distribution and the two-dimensional nuclear magnetic resonance T1-T2, D-T2 distribution, the number of one-dimensional distribution points shall not be less than 128, and the number of two-dimensional distribution points shall not be less than 64 ×64 pcs. After the result processing is completed, save the relevant data and pictures, and write the test report.

In some embodiments, the nuclear magnetic resonance core measurement experimental method 200 also includes: after the experiment is completed, when the system temperature is cooled, first close the continuous displacement system valve and the continuous confining pressure system valve; open the displacement fluid discharge valve to discharge the liquid in the pipeline Recover; open the confining pressure fluid discharge valve, discharge the confining pressure fluid in the inner cavity of the core holder 5 for recovery, and filter the recovered confining pressure fluid; connect the pipeline and probe connected to the core holder 5 Remove the connection line with the nuclear magnetic resonance spectrometer, take out the high temperature and high pressure probe 7 from the cavity of the low field nuclear magnetic resonance core analyzer 8, remove the plug of the core holder 5, the core plunger and other components, remove the heat shrinkable tube, and take out For core samples, clean the inner cavity of the holder, and replace the rubber ring and gasket.

Specifically: After the experiment is completed, after the system temperature cools down, first close the continuous displacement system valve and the continuous confining pressure system valve, then open the displacement fluid discharge valve to recover the liquid in the pipeline, and then open the confining pressure fluid discharge The valve is used to discharge the confining pressure fluid in the inner cavity of the core holder 5 for recovery, and the recovered confining pressure fluid is filtered for use in the next experiment, and finally the pipeline and probe connected to the core holder 5 Remove the connection line with the nuclear magnetic resonance spectrometer, take out the high temperature and high pressure probe 7 from the cavity of the low field nuclear magnetic resonance core analyzer 8, remove the plug of the core holder 5, the core plunger and other components, remove the heat shrinkable tube, and take out For the core sample, clean the inner cavity of the holder, replace the rubber ring and gasket, and prepare for the next experiment.

According to an embodiment of the present invention, an NMR core measurement experiment system 100 for simulating a downhole high temperature and high pressure environment based on dynamic adjustment. The nuclear magnetic resonance core measurement experiment system 100 controls the continuous high pressure system 2, the high temperature circulation system 3, the auxiliary cooling system 4 and each valve on the system through the computer control system 11, monitors the temperature and pressure of each part of the system and displays them on the computer, and integrates The temperature and pressure dynamic adjustment mechanism simulates formation pressure and temperature, and performs real-time NMR measurement under given high temperature and high pressure conditions. During the experiment, the core to be tested is placed in the core holder 5, and the high temperature and high pressure probe 7 and low field NMR The resonance core analyzer 8 measures and records the experiment, obtains one-dimensional and two-dimensional nuclear magnetic resonance data, and uses the auxiliary cooling system 44 to assist the cooling of the radio frequency coil and the magnet. The nuclear magnetic resonance core measurement experiment system 100 based on the dynamic adjustment to simulate the downhole high temperature and high pressure environment of the embodiment of the present invention plays an important role in the nuclear magnetic resonance evaluation of high temperature and high pressure reservoirs.

It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application shall have the usual meanings understood by those skilled in the art to which the present invention belongs.

In the description of the present application, it is to be understood that the terms "central", "longitudinal", "transverse", "upper", "lower", "top", "bottom", "inner", "outer" etc. indicate The orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation or be configured in a specific orientation. and operation, and therefore should not be construed as limiting the invention.

In this application, terms such as "installation", "connection", "connection" and "fixation" should be interpreted in a broad sense, for example, it can be a fixed connection or a detachable connection, unless otherwise clearly specified and limited. , or integrated; it can be mechanically connected or electrically connected; it can be directly connected or indirectly connected through an intermediary, and it can be the internal communication of two components or the interaction relationship between two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. All of them should be covered by the scope of the claims and description of the present invention. In particular, as long as there is no structural conflict, the technical features mentioned in the various embodiments can be combined in any manner. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims (10)

1. A nuclear magnetic resonance core measurement experimental system is characterized in that it comprises a computer control system, a continuous high-pressure system, a high-temperature circulation system, an auxiliary cooling system, a rock core holder, a high-temperature and high-pressure probe, a low-field nuclear magnetic resonance core analyzer, and a circulation system. Liquid collection container, wherein: the computer control system is electrically connected with the continuous high-pressure system, the high-temperature circulation system, and the auxiliary cooling system for controlling each system; the continuous high-pressure system is connected with the high-temperature The circulation system is connected, and is used for providing stable confining pressure to the inside of the core holder, and at the same time, is used for displacing the core in the core holder; the high temperature circulation system is used for the A stable temperature is provided inside the core holder; the auxiliary cooling system is used to assist in reducing the temperature of the high temperature and high pressure probe; the core holder is fixed on the high temperature and high pressure probe for placing core samples; the high temperature The high-voltage probe part is set in the cavity of the low-field nuclear magnetic resonance core analyzer, and is used to replace the core samples required for the experiment; the circulating fluid collection container is used for the recovery of the experimental waste liquid. 2. The nuclear magnetic resonance core measurement experiment system according to claim 1, wherein the continuous high pressure system comprises a continuous confining pressure system, and the continuous confining pressure system comprises a confining pressure liquid container, a confining pressure system intermediate vessel, a hydraulic pressure An oil container and two constant-speed constant-pressure pumps of the confining pressure system, wherein: the confining pressure liquid container is sequentially connected to the first manual valve, the pneumatic valve, and the intermediate container of the confining pressure system through pipelines; the liquid outlet of the intermediate container of the confining pressure system The mouth is divided into a first road and a second road, the first road is connected with the hydraulic oil container through the second manual valve, and the second road is divided into two roads, and the two roads are respectively connected to the two hydraulic oil containers through the pneumatic valve. The liquid inlets of the constant-speed and constant-pressure pumps of the confining pressure system are connected, and the liquid replenishment ports of the two constant-speed and constant-pressure pumps of the confining pressure system are connected with the hydraulic oil container through pipelines; The pipeline is connected to the confining pressure inlet of the core holder, and a pressure sensor is arranged on the confining pressure pipeline. 3. nuclear magnetic resonance rock core measurement experiment system according to claim 2, is characterized in that, described continuous high pressure system also comprises continuous displacement system, and described continuous displacement system comprises displacement liquid container, displacement system intermediate container and Two displacement system constant speed and constant pressure pumps, wherein: the displacement liquid container is sequentially connected to the third manual valve, the pneumatic valve and the displacement system intermediate container through the pipeline; the liquid outlet of the displacement system intermediate container It is divided into a third road and a fourth road, the third road is connected with the hydraulic oil container through the fourth manual valve, and the fourth road is further divided into two roads, and the two roads are respectively connected to the two The liquid inlets of the constant speed and constant pressure pumps of the displacement system are connected, and the replenishment ports of the two constant speed and constant pressure pumps of the displacement system are connected with the hydraulic oil container through pipelines; the third manual valve is connected with the hydraulic oil container through the displacement pipelines. The displacement inlet of the core holder is connected, and a pressure sensor is arranged on the displacement pipeline. 4. The nuclear magnetic resonance rock core measurement experimental system according to claim 3, characterized in that, the high-temperature circulation system comprises a high-temperature circulation pump, a constant temperature oil bath heater, and a three-way pneumatic ball valve, wherein: the enclosure of the continuous high-pressure system The pressure outlet is sequentially connected to the fifth manual valve, the high-temperature circulation pump, the constant temperature oil bath heater, the back pressure valve, the three-way pneumatic ball valve, the sixth manual valve, and the confining pressure outlet of the continuous high-pressure system through pipelines. A temperature sensor is provided on the pipeline between the fifth manual valve, a temperature sensor and a pressure sensor are provided on the pipeline between the constant temperature oil bath heater and the back pressure valve, and the sixth manual valve is connected to the A pressure sensor and a temperature sensor are arranged on the pipeline between the confining pressure inlets of the continuous high pressure system. 5. The nuclear magnetic resonance rock core measurement experimental system according to claim 4, wherein the circulating fluid collection container is respectively arranged at the confining pressure outlet of the rock core holder and the displacement outlet of the rock core holder And below the three-way pneumatic ball valve of the high temperature circulation system, wherein the confining pressure outlet of the core holder is also provided with a seventh manual valve; the displacement outlet of the core holder is also provided with a back pressure valve . An eighth manual valve and a balance; the three-way pneumatic ball valve is connected to the circulating liquid collection container through a pipeline. 6. according to the nuclear magnetic resonance rock core measurement experiment system according to any one of claim 1-5, it is characterized in that, described auxiliary cooling system comprises: Two gradient coils and magnet groups are arranged at intervals on both sides of the high temperature and high pressure probe; Two temperature sensors, respectively used to measure the temperature of the two gradient coils and magnet groups; The refrigerating machine respectively extends to the gap between the high temperature and high pressure probe and the two gradient coils and magnet groups through pipelines. 7. The nuclear magnetic resonance core measurement experimental system according to any one of claims 1-5, wherein the high temperature and high pressure probe is detachably arranged in the cavity of the low-field nuclear magnetic resonance core analyzer. 8. The nuclear magnetic resonance core measurement experimental system according to any one of claims 1-5, wherein the core holder comprises: a heat-shrinkable tube, in which a core sample is arranged, and the heat-shrinkable tube The two ends of the core plug are sealed by a core plug, and a sealing rubber ring and a gasket for a sealed connection are provided on the core plug; a displacement pipeline is connected to the core plug; wherein, the high temperature and high pressure probes are arranged at intervals and in parallel On both sides of the heat-shrinkable tube, the two ends of the high-temperature and high-pressure probes on both sides are sealed and connected through plugs, so that a sealed cavity is formed between the high-temperature and high-pressure probes on both sides, and the two ends of the high-temperature and high-pressure probes on both sides are sealed. The plugs are respectively provided with a confining pressure outlet and a confining pressure inlet; the plug is also provided with a pressure gauge, a temperature sensor and a pressure relief valve, and the displacement pipeline passes through the plug and is connected to the The plug is fixed. 9. A nuclear magnetic resonance rock core measurement experimental method, applied to the nuclear magnetic resonance rock core measurement experimental system according to claims 1 to 8, is characterized in that, the nuclear magnetic resonance rock core measurement experimental method comprises: Step 1, prepare standard plunger rock core sample, and carry out pretreatment to described rock core sample; Step 2, low-field nuclear magnetic resonance core analyzer calibration and measurement parameter setting; Step 3, installing the core sample; Step 4, pressure test and pipeline tightness detection; Step five, pressurization and heating experiment; Step six, displacement experiment; Step seven, NMR experiment data processing. 10. nuclear magnetic resonance rock core measurement experimental method according to claim 9 is characterized in that, described step 5 further comprises: Set confining pressure and temperature; The system rises to the target pressure with the preset pressure gradient, and judges whether the target confining pressure is reached, and if not, continues to raise the pressure; The system raises the oil bath to the target temperature with the preset temperature gradient, and judges whether the temperature of the oil bath heater reaches the target temperature, and if not, continues to heat up; Determine whether the system pressure is stable, if so: determine whether the inside of the core holder reaches the target temperature, if not, release or replenish pressure, or determine whether the circulation pump reaches the maximum speed; further: if the circulation pump reaches the maximum speed, the oil The bath continues to heat up or cool down with a preset temperature gradient; Judging whether the system pressure is stable, if not: pressure relief or supplementary pressure; Judging the change range of the internal temperature of the core holder within a preset time, if not, the oil bath continues to heat up or cool down with a preset temperature gradient; if so, start the nuclear magnetic resonance measurement test.

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