CN104407233B - Hydrate dielectric property test device in a kind of deposit - Google Patents

Abstract

The invention discloses a device for testing the dielectric properties of hydrates in sediments, which includes a built-in reaction kettle, a gas supply system, a vacuum system, a data acquisition system, a temperature control system and a measurement and control system. The interference shielding line also includes a removable capacitance test chamber, a first cylindrical electrode, a second cylindrical electrode and a tin film. Tin film is adhered on one end surface of the electrode, and then touches both ends of the sample respectively, and the other end surface is respectively embedded in the opposite sides of the removable capacitance test chamber and elastically fixed. The measurement and control system also includes an inductance component, the first cylindrical electrode and the second The two cylindrical electrodes are connected to the Q meter through the anti-interference shielding wire and the inductance component. The measuring device can measure the dielectric loss factor and the dielectric constant of solid insulating materials in situ under the extreme conditions of high pressure and low temperature, expands the temperature and pressure application range of the existing device, and improves the measurement accuracy.

Description

A device for testing the dielectric properties of hydrates in sediments

technical field

The invention relates to a testing device for in-situ measurement of the dielectric loss of insulating solid materials, including the dielectric loss factor and dielectric constant of the insulating material, in particular to an in-situ synthesis of hydrates in porous media at high pressure and low temperature and their dielectric loss and dielectric constant testing device.

Background technique

Gas hydrate is an ice-like solid formed by gas (or volatile liquid) and water under certain temperature and pressure conditions, commonly known as combustible ice, widely distributed in the sediments below the surface of the tundra and under the seabed at the continental margin middle. Natural gas hydrate has huge natural gas storage capacity. The ideal structure type I methane hydrate contains 164 times the methane gas in the standard state, and the type II structure gas hydrate contains 184 times the natural gas in the standard state. The natural gas hydrate reserves in the world are huge. It is estimated that the natural gas resources in hydrates are 2×10 ¹⁶ m ³ , which is equivalent to 2×10 ⁵⁰⁰ million tons of oil equivalent, which is twice the total carbon content of conventional fuels in the world.

In the process of exploration and development of oil and gas, geophysical method has been proved to be a very effective method. Electromagnetic wave propagation logging (also known as dielectric logging) is a new logging method developed in the 1980s. It is mainly used to measure the dielectric constant (ε _r ) of formations, and multi-frequency dielectric scanning imaging logging is more commonly used. The principle is based on the obvious difference in the dielectric constant of water (ε _r = 50-80), rock (ε _r = 5-10) and crude oil (ε _r = 2-3), so the determination of the dielectric constant in rock is It is an important basis for judging oil-bearing layers or water-bearing layers, and this technology is widely used in pore fluid analysis, skeleton analysis and geological structure analysis, stratum evaluation and reserve estimation. The size of the dielectric constant in the rock is an information carrier that can better reflect the physical properties of the formation. From the analysis of well logging data, it can be seen that the dielectric constant is closely related to the lithology of the formation, the internal structure of the rock, and especially the identification of oil and gas. Relationship. However, at present, the dielectric constant measurement of gas hydrate-bearing formations is in the stage of on-site well drilling verification and reverse deduction, and the cost of well drilling measurement is high, and the data acquisition is greatly disturbed. Therefore, the research on the dielectric constant characteristics of gas hydrates and reservoirs and the development of dielectric logging methods for gas hydrates are of great significance to the exploration, resource evaluation and development of gas hydrates, and have great market prospects. However, the existing dielectric loss and dielectric constant devices are mainly designed at normal temperature and pressure, which cannot meet the in-situ measurement of gas hydrate under low temperature and high pressure conditions.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned shortcomings, to provide a device for in-situ measurement of dielectric loss factor and dielectric constant of solid insulating materials under extreme conditions of high pressure and low temperature, which expands the use range of current device temperature and pressure, and improves measurement accuracy .

In order to achieve the purpose of the foregoing invention, the present invention is realized through the following technical solutions:

A device for testing the dielectric properties of hydrates in sediments according to the present invention includes a reaction kettle with a built-in sample to be tested, a gas supply system and a vacuum system connected in parallel with the gas inlet and outlet of the reaction kettle, and a temperature control system on the reaction kettle. A data acquisition system for electrically connecting the sensor to a pressure sensor, a temperature control system for maintaining the reaction temperature in the reactor, and a measurement and control system for testing the dielectric constant of the sample. The measurement and control system includes a Q meter and an anti-interference shield connecting the reactor and the Q meter line, the test device of the present invention also includes a removable capacitance test chamber, a first cylindrical electrode, a second cylindrical electrode and a tin film arranged in the reaction kettle, and a sample loading sheet is arranged in the middle of the removable capacitance measurement and control chamber. One end surface of the first cylindrical electrode and the second cylindrical electrode are adhered with tin film and then contact the two ends of the sample respectively, and the other end surfaces of the first cylindrical electrode and the second cylindrical electrode are respectively embedded in both sides of the removable capacitance test chamber , and elastically fixed on the opposite wall, the Q meter of the measurement and control system is electrically connected to the first cylindrical electrode and the second cylindrical electrode of the above-mentioned removable capacitance test chamber, and there is a parallel connection between the Q meter and the removable capacitance test chamber Inductive components.

The Q meter of the measurement and control system includes a capacitance Cx test loop and an inductance Lx test loop. After the inductance Lx test loop is connected in series with an inductor component, it is connected in parallel with the capacitance Cx test loop and electrically connected to the first cylindrical electrode or the second electrode. Cylindrical electrode, the other electrode is connected to the Q meter through the anti-interference shielded wire. Through the inductance component, the resonance method can be used to solve the interference of the inherent capacitance of the component, and the dielectric loss of the sample can be accurately measured.

Both sides of the tin film are evenly coated with vaseline, which acts as an adhesive and can eliminate residual air between the contact surfaces.

The first cylindrical electrode and the second cylindrical electrode are respectively fixed on the opposite wall surface of the removable capacitance test chamber by springs at the other end faces, so as to realize the stretchability of the electrodes in this way, thereby ensuring that the electrodes can be compatible with samples of different thicknesses. Full contact.

The first cylindrical electrode and the second cylindrical electrode are cylindrical copper blocks, and their end surfaces are mirror-surface structures. The mirror structure can ensure that the electrode end face is in uniform contact with the sample.

Compared with the prior art, the present invention has the following advantages:

1. The present invention solves the interference of the inherent capacitance of components through the resonance method, and can accurately measure the dielectric loss of the sample;

2. The temperature and pressure can be adjusted to measure the dielectric loss parameters of solid samples under different temperatures and pressures, ensuring the feasibility of high-pressure and low-temperature measurement;

3. The reaction kettle can measure the change of dielectric loss parameters during the chemical reaction process, detect the progress of the reaction, and measure the different reaction states of the sample under in situ conditions;

4. The retractable capacitance test chamber is embedded with retractable electrodes. The removable capacitance test chamber can effectively ensure the loading of samples, and the retractable electrodes can ensure full contact between samples and electrodes;

5. The functions of each part of the system are clear, with good upgradeability and expandability, and wide adaptability.

Description of drawings

Fig. 1 is a schematic structural diagram of the device for testing the dielectric properties of hydrates in sediments according to the present invention, in which the reactor is a structural diagram from a top view.

Fig. 2 is a schematic structural view of the reactor shown in Fig. 1 in a horizontal view.

Fig. 3 shows the dielectric constant of gas hydrate-bearing rock samples at different frequencies.

Explanation of reference signs: 1-data acquisition system, 2-computer, 3-inductance component, 4-Q meter, 5-pressure sensor, 6-vacuumizing system, 7-temperature sensor, 8-gas supply system, 9-response Kettle, 10-sample, 11-retractable spring, 12-removable capacitance test chamber, 13-cylindrical electrode, 14-bolt, 15-sample loading sheet, 16-low temperature constant chamber, 17-reaction kettle bottom loop connector, 18-anti-interference shielded wire, 19-base, 20-end cover, 21-polytetrafluoroethylene insulated liner, 22-reactor, f1-first valve, f2-second valve.

detailed description

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings and embodiments. Apparently, the described embodiments are only some of the embodiments of the present invention, not all of them.

For an embodiment of the device for testing the dielectric properties of hydrates in sediments according to the present invention, please refer to FIG. 1 . FIG. 1 is a schematic structural diagram of the device for testing the dielectric properties of hydrates in sediments in this embodiment. A device for testing the dielectric properties of hydrates in sediments includes a reaction kettle 22 with a built-in test sample 10, a gas supply system 8 for providing a gas source for the reaction kettle 22, a vacuum system 6, a data acquisition system 1, and a maintenance reactor The temperature control system of the reaction temperature within 22 and the measurement and control system of the dielectric constant of the test sample.

The reaction kettle 22 is provided with an end cover 20, and the end cover 20 and the reaction kettle 22 are connected by bolts and sealed with an O-ring to prevent the high-pressure gas in the reaction kettle 22 from leaking out.

The reaction kettle 22 is provided with a sample loading sheet 15. The specifications of the sample loading sheet 15 are: 3.5mm*3mm, φ25mm. The sample loading sheet 15 of this specification allows a sample with a diameter of φ25mm to be loaded into the removable capacitance test chamber 12 , please refer to Fig. 2, the outer wall of the reaction kettle 22 is made of stainless steel, and the insulating liner 21 is made of insulating polytetrafluoroethylene to ensure that it is not affected by the conduction of the stainless steel reaction kettle wall, and is also made of insulating polytetrafluoroethylene The sample loading sheet 15 and the polytetrafluoroethylene removable capacitance test chamber 12 are embedded with a first cylindrical electrode 13 and a second cylindrical electrode 23 with a diameter of φ2 cm and a length of 1 cm, which are well conductive.

In a common test system, it is required that the sliced sample described in the sample requirement may be a cylindrical shape for the sample to be tested. This is an effective way to reduce errors caused by sample edge leakage and fringe electric fields. The thickness of the sample can be between 0.5-5mm. If it is too thin or too thick, the test accuracy will decrease, and the sample should be as straight as possible. Existing samples, such as rock slices, etc., but hydrate-containing samples need to be measured under high pressure and low temperature, so it is often impossible to test samples with high fidelity. Through the present invention, after the rock core in the target area is selected, natural gas hydrate is synthesized in situ under high pressure and low temperature conditions in the target area by adding natural gas of the same composition, and then its capacitance property is tested.

The sample loading sheet 15 is put into the removable capacitance testing chamber 12, and the first cylindrical electrode 13 and the second cylindrical electrode 23 embedded in the removable capacitance testing chamber 12 contact the two ends of the sample 10 respectively through the tin film on one end surface. The two sides of described tin film are evenly coated with a thin layer of vaseline, which plays an adhesion role and can get rid of residual air between the contact surfaces, and the tin film sticks to the first columnar electrode 13 and the second columnar electrode 23 again. end face. The first cylindrical electrode 13 and the second cylindrical electrode 23 are cylindrical copper blocks with a mirror structure on their end faces. The other end faces are respectively embedded in the removable capacitance test chamber 12 and connected to the opposite wall by springs.

The measurement and control system includes a Q meter 4 , an inductance component 3 and an anti-interference shielded wire 18 . The Q meter includes three joints and two test loops, that is, the capacitance Cx test loop and the inductance Lx test loop are connected in parallel. The used inductance Lx test loop is directly connected to the inductor component 3 according to the frequency. The used capacitance Cx test loop enters the inside of the reactor 22 through the anti-interference shielding wire 18 through the loop connector 17 at the bottom of the reactor, and is connected with the first cylindrical electrode 13 and the second cylindrical electrode 23 of the corresponding removable capacitance test chamber 12 .

The temperature control system is a low-temperature constant temperature chamber 16, and the reaction kettle is completely placed in the low-temperature constant temperature chamber 16, and the temperature of the reaction kettle 2 is kept constant through air bath circulation.

In this embodiment, the reaction kettle 22 is provided with an air inlet and an outlet to communicate with the air supply system 8 and the vacuum system 6 through the first valve f1 and the second valve f2 respectively. In order to detect the temperature and pressure in the reactor 22, the device of the present invention is arranged with the temperature test point T of the temperature sensor and the pressure monitoring point P of the pressure sensor, and the temperature and pressure pass the signal to the data acquisition through the temperature sensor 7 and the pressure sensor 5 respectively. System 1, the data is read and processed by the data acquisition system 1, and then transmitted to the computer 2 for display and storage. The pressure sensor 5 leads are electrically connected to the data acquisition system 1, and the other end is connected to the gas supply system 8 and then connected to the reactor 2; the temperature sensor 7 is inserted into the reactor body, and the temperature The sensor 7 is electrically connected with the data acquisition system 1 .

In this embodiment, the data acquisition system 1 adopts the Agilent-34970A data acquisition instrument of Agilent Company to collect the temperature sensor 7 and the pressure sensor 5, and the signal is transmitted to the computer 2 through the network interface after digitization and display adjustment, and the computer 2 can display and store data , and can complete the post-processing of the data. Q meter 3 adopts WY2358D digital display adjustable frequency Q meter. The inductance component adopts LK-2 supporting ten inductance parts in the range of 0.1-1000μH, which are used for Q meter 3 to correct the inherent capacitance of components at different frequencies, and the received Q value and resonance value readings are transmitted to Q meter 3 and counted Obviously, Q Table 3 automatically records the maximum Q value and resonance value for calculating its dielectric loss factor and dielectric constant.

The sample measurement adopts the resonance method (that is, the Q table method, The test frequency range is 10kHz to 260MHz), and the resonance method can effectively avoid the inherent capacitance of the equipment through the inductance component, thereby reducing interference. Based on the natural gas hydrate exploration site frequency near 100MHz, and the laboratory uses in-situ reconstruction of natural gas hydrate core samples and tests.

In the present embodiment, the water-bearing rock sample 10 is first packed into the sample loading sheet 15 made of polytetrafluoroethylene, and the removable capacitance test chamber 12 is installed on both sides, and the two sides of the sample 10 are contacted with the cylindrical electrodes 13, and the The optional capacitance test chamber 12 is inserted into an insulating liner 21 made of polytetrafluoroethylene, connected with an anti-interference shielding wire 18, and sealed with an end cover 20 of the reaction kettle. In order to eliminate the interference of residual air in the pipeline, open the vacuum system 6 and valve F2 to start vacuuming the system. After about 15 minutes, the vacuuming is completed, close the second valve F2, and open the first valve F1 for air intake. After the pressure is balanced, set and open the constant temperature air bath 16, the data acquisition system 1, and the computer 2 to start monitoring the reaction process. The pore pressure is determined by the air pressure, and the data is transmitted to the data acquisition system 1 by the pressure sensor 5 and the temperature sensor 7 . During this process, the dielectric loss of rock samples under different temperature and pressure conditions can be tested. During the continuous growth stage of hydrates, the dielectric loss and dielectric constant of rock samples with different hydrate saturations can be tested under certain temperature and pressure conditions.

The steps to use this device are as follows:

(a) Normal temperature and pressure solid dielectric loss test:

Put the sample into the reaction kettle in advance, and then seal it. After sealing, the inductance components are selected according to different test frequencies to measure the Q value, and the dielectric loss factor and dielectric constant of the insulating material are determined through the calculation of the Q value.

(b) High-pressure low-temperature solid dielectric loss test:

When it comes to high-pressure gas, the whole device should be checked for leaks before the reaction, the system exhaust valve should be closed, the inlet valve should be opened to inject a certain pressure of nitrogen into the reaction kettle, and then the gas source should be closed, and the whole reaction should be kept at a constant temperature in a low-temperature and constant temperature room. The kettle is closed for one day, if the indication value of the pressure gauge does not drop significantly, it means that the reactor is well sealed, if not, it means that there is a leak, usually use a foaming agent to check the leak, the existence of the leak seriously affects the indication accuracy of the flowmeter , so it must be strictly sealed; after the leak detection, the nitrogen gas can be released, the end cover of the reactor can be opened, the required sample can be added, after sealing, the system is evacuated, and then the experimental gas is injected and then released, repeated two to three times to ensure that the remaining The air in the reactor can be ignored, and finally inject the required pressure into the reaction air channel, and let it stand for a day after the pressurization is completed, so that the reaction sample, the reactor pipeline and the reactor wall and the gas can be fully dissolved; the constant temperature air bath is set The reaction temperature allows the system to react, and the dielectric loss test of the system can be carried out during the reaction.

The equipment is measured through the calibration of the reference sheet under normal temperature and pressure, and the equipment has small measurement errors and strong reliability. The results of gas hydrate rock samples measured at high pressure and low temperature are as follows:

Figure 3 shows the dielectric constant of gas hydrate-bearing rock samples at different frequencies, with a test temperature of 273.15K and a pressure of 10MPa. It can be seen from the figure that the measurement results conform to the law that the dielectric constant of solid samples decreases with the increase of frequency, which shows that the experimental results are valid and verifies the effectiveness of the equipment for measurement at high pressure and low temperature.

The foregoing embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention; therefore, although the specification has described the present invention in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand , the present invention can still be modified or equivalently replaced; and all technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered by the claims of the present invention.

Claims (4)

1. hydrate dielectric property test device in a kind of deposit, including it is built-in with the reactor of sample, identical reaction kettle Air inlet/outlet and air supply system logical in succession and pumped vacuum systems, the temperature sensor on identical reaction kettle and pressure transducer are electric The observing and controlling system of the data collecting system of connection, the temperature control system of maintenance reaction kettle interior reaction temperature and test sample dielectric constant System, the TT＆C system includes the anti-interference shielding line of Q tables and coupled reaction kettle and Q tables, it is characterised in that：Also include and set In retrievable capacity measurement room, the first cylindrical electrode, the second cylindrical electrode and tin film in reactor, retrievable electric capacity observing and controlling room Centre is provided with sample carrier sheet, and sample is contacted respectively after adhesion tin film on the end face of the first cylindrical electrode and the second cylindrical electrode Product two ends, the other end of the first cylindrical electrode is embedded in the side of retrievable capacity measurement room, the second cylindrical electrode it is another End face is embedded in the opposite side of retrievable capacity measurement room, and the flexible fastening on relative wall, and the Q tables of TT＆C system are electrical Connect the first cylindrical electrode and the second cylindrical electrode of above-mentioned retrievable capacity measurement room, and Q tables and retrievable capacity measurement room Between be parallel with Inductive component；First cylindrical electrode is fixed on retrievable capacity measurement room one in other end by spring On individual wall, second cylindrical electrode is fixed on relative another in retrievable capacity measurement room in other end by spring On wall.

2. hydrate dielectric property test device in deposit according to claim 1, it is characterised in that：The observing and controlling system The Q tables of system include electric capacity Cx test loops and inductance Lx test loops, the inductance Lx test loops tandem electric inductance device assembly Afterwards, then after in parallel with electric capacity Cx test loops the first cylindrical electrode or the second cylindrical electrode are electrically connected, another electrode then passes through Anti-interference shielding line accesses Q tables.

3. hydrate dielectric property test device in deposit according to claim 1, it is characterised in that：The tin film Two sides is evenly coated with vaseline.

4. hydrate dielectric property test device in deposit according to claim 1, it is characterised in that：First post Shape electrode and the second cylindrical electrode are cylindrical copper billet, and its end face is mirror surface structure.