Apparatus and method for three-phase coexistence porous medium sample preparation and sonic and electrical property measurement

Abstract

This invention discloses a device and method for preparing three-phase coexisting porous media samples and measuring their acoustic and electrical properties, belonging to the field of experimental acoustic and electrical measurement in rock physics. It includes: a sample chamber, with a rubber sleeve, a hydraulic oil tank, a cooling liquid tank, and a reaction vessel arranged sequentially from the inside out; a first acoustic-electric composite probe is installed at the top of the sample chamber, and a second acoustic-electric composite probe is installed at the bottom; a water pump is connected to the top of the sample chamber via a liquid pipeline, and gas cylinders A and B are connected to the top of the sample chamber via gas pipelines; a vacuum pump is connected to the bottom of the sample chamber via a gas pipeline, and a fluid metering device is also connected to the bottom of the sample chamber; one end of the acoustic-electric measurement and control system is connected to the first acoustic-electric composite probe, and the other end of the acoustic-electric measurement and control system is connected to the second acoustic-electric composite probe; a confining pressure system is connected to the hydraulic oil tank, and a temperature control system is connected to the cooling liquid tank; corresponding valves are installed on each gas pipeline and liquid pipeline. The saturation in the porous media sample of this invention can be controlled and adjusted.

Description

Technical Field

[0001] This invention relates to the field of acoustic and electrical measurement technology, and more specifically to a device and method for preparing three-phase coexisting porous media samples and measuring their acoustic and electrical properties. Background Technology

[0002] Natural gas hydrate, also known as "combustible ice," is an ice-like, crystalline, supramolecular cage-like compound formed by natural gas and water molecules under high pressure and low temperature. It is widely distributed and abundant in the South China Sea, and due to its clean combustion, it is considered a type of unconventional natural gas resource with great development potential. Because core samples containing natural gas hydrate are difficult to obtain and unstable under environmental temperature and pressure, the physical properties of sediments containing natural gas hydrate are mainly studied by simulating laboratory-synthesized samples. Currently, most methods for simulating laboratory-synthesized samples of natural gas hydrate sediments target only the two phases of water and natural gas hydrate. Exploration practice shows that shallow gas-hydrate mixing zones exist in marine sedimentary bodies, where natural gas, water, and hydrate coexist. Existing methods for preparing porous media samples containing natural gas hydrate produce samples with either only two phases (hydrate and water) or only two phases (gas and hydrate), failing to simulate the reservoir properties of shallow gas-hydrate mixing zones with three phases. However, actual exploration in the South my country Sea has revealed the existence of mixed reservoirs at the bottom of hydrated layers, where gas, water, and hydrates coexist. Their formation is primarily controlled by geological conditions, and their temperature and pressure conditions may be at the critical levels for natural gas hydrate formation.

[0003] Geophysical logging is an engineering technique for continuously measuring and recording the rock physical responses of various formations at different depths. Resistivity logging data is crucial for the quantitative evaluation of reservoir parameters. The rock physical response characteristics of mixed zones are complex. For logging interpretation and evaluation, when the reservoir contains hydrates, the reservoir resistivity increases, and the sonic transit time (the reciprocal of the sonic velocity) decreases (the sonic velocity increases). When the reservoir contains gas, the reservoir resistivity increases, but the sonic transit time decreases. Therefore, for the evaluation of reservoir saturation in mixed zones, a comprehensive analysis combining resistivity data and sonic logging data is required. This invention relates to a method and apparatus for preparing porous media samples containing gas, water, and gas hydrates under laboratory conditions and measuring their sonic velocity and resistivity. The apparatus and method of this invention, used to conduct acoustic and electrical response experiments on porous media samples containing gas, water, and gas hydrates under varying saturation conditions, can provide support for research on quantitative evaluation methods for mixed zone saturation logging.

[0004] Therefore, proposing a device and method for preparing three-phase coexisting porous media samples and measuring their acoustic and electrical properties to solve the difficulties existing in the prior art is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method and apparatus for preparing three-phase coexisting porous media samples and measuring their acoustic and electrical properties, in order to solve the technical problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A device for preparing samples of three-phase coexisting porous media and measuring their acoustic and electrical properties includes: a sample chamber, and a rubber sleeve, a hydraulic oil tank, a cooling liquid tank, and a reaction vessel arranged sequentially from the inside out of the sample chamber. The top of the sample chamber is equipped with a first acoustic-electric composite probe, and the bottom of the sample chamber is equipped with a second acoustic-electric composite probe. A water pump is connected to the top of the sample chamber via a liquid pipeline, and gas cylinders A and B are connected to the top of the sample chamber via a gas pipeline. A vacuum pump is connected to the bottom of the sample chamber via a gas pipeline, and a fluid metering device is also connected to the bottom of the sample chamber. One end of the acoustic-electric measurement and control system is connected to the first acoustic-electric composite probe, and the other end of the acoustic-electric measurement and control system is connected to the second acoustic-electric composite probe; The confining pressure system is connected to the hydraulic oil tank, and the temperature control system is connected to the cooling liquid tank. Each gas and liquid pipeline is equipped with a corresponding valve.

[0007] A method for preparing and measuring the acoustic and electrical properties of a three-phase coexisting porous medium sample, using the aforementioned apparatus for preparing and measuring the acoustic and electrical properties of a three-phase coexisting porous medium, includes the following steps: S1. Load the porous media sample into the sample chamber, close the reactor, and shut off all pipeline valves; S2. Open the vacuum pump and the valve connected to it to perform vacuum treatment on the porous medium sample in the sample chamber. After the vacuum treatment is completed, close the valve connected to the vacuum pump. S3. Open the water pump and the valve connected to it to fill the pore space of the porous medium sample with water, and then close the corresponding valve. S4. Open gas cylinder A and its connected valves, as well as the fluid metering device and its valves. Gas A displaces the aqueous solution in the pores. Record the water output of gas cylinder A. ; S5. Close gas cylinder A and its connected valves, open gas cylinder B and its connected valves. Gas B begins to enter the pores of the porous medium sample, displacing the aqueous solution from one end of the fluid metering device. Measure the water output of gas cylinder B. ; S6. Close gas cylinder B and its connected valves, as well as the fluid metering device and its valves; S7. Hydraulic oil is injected into the hydraulic oil tank through the confining pressure system. The hydraulic oil transmits pressure to the side of the porous medium sample through the rubber sleeve to form confining pressure. S8. Reopen the water pump and the valve connected to it to apply pore pressure to the porous medium sample through the water pump and keep the pore pressure constant. S9. The cooling liquid is injected into the cooling liquid tank for circulation through the temperature control system to control the temperature of the reactor. S10. Under steady-state conditions, the pore space of the porous medium sample is a three-phase medium consisting of water, gas B, and gas A hydrates. S11. Based on the amount of substance of gas A injected in S4 and the volume of gas B injected in S5, calculate the amount and volume of the generated hydrate, and then calculate the saturation of the three-phase medium of water, gas B, and gas A hydrate in the pore space of the porous medium sample under steady-state conditions. S12. After the porous medium sample is formed, the first and second acoustic-electric composite probes are controlled by the acoustic-electric measurement and control system to measure the resistance R and the sound wave propagation time Δt of the porous medium sample, so as to obtain the resistivity and sound wave velocity of the porous medium sample.

[0008] Optionally, in S4, after a certain period of time, gas cylinder A and its connected valve are closed. At this time, the fluids in the pore space of the porous medium sample are gas A and water, and the saturation of the two fluids is:

[0009] in, The porosity of the porous medium sample. This represents the water output of cylinder A. Water saturation Let be the saturation level of gas A.

[0010] Optionally, in S5, after a certain period of time, gas cylinder B and its connected valve are closed. At this time, the fluids in the pore space of the porous medium sample are gas A, gas B, and water, and the saturation of the three fluids is:

[0011] in, The porosity of the porous medium sample. This represents the water output of cylinder A. This represents the water output from gas cylinder B. Water saturation Let be the saturation level of gas A. Let be the saturation level of gas B.

[0012] Optionally, in S11, the saturation of the three-phase medium consisting of water, gas B, and gas A hydrates in the pore space of the porous medium sample under steady-state conditions is calculated as follows: The molecular molar mass of gas A is The density is The volume is The amount of substance of gas A is:

[0013] During the formation of hydrate from gas A, one gas molecule forms a complex. X If there are 1 water molecule, then the molar mass of its hydrate is:

[0014] Volume is The amount of gas A that can form a hydrate is... n ; The density of hydrates is The volume of the hydrate formed is then... ; Therefore, the saturation of the hydrate three-phase medium under steady state is: The saturation level of gas B is Water saturation is ,in, The porosity of the porous medium sample. This represents the water output of gas cylinder B.

[0015] Optionally, the first and second acoustic-electric composite probes in S12 can be used as impedance measurement electrodes or as sound wave transmitting and receiving probes.

[0016] Optionally, the formulas for the resistivity and acoustic velocity of the porous medium sample in S12 are as follows:

[0017] in, L The length of the porous medium sample. S The cross-sectional area of ​​the porous medium sample is... R For resistance, For the time required for sound wave transmission, v For the speed of sound waves, is the resistivity.

[0018] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a device and method for preparing three-phase coexisting porous media samples and measuring their acoustic and electrical properties, the beneficial effects of which are: 1) This invention can guide the preparation of porous media samples in which gas, water and hydrate coexist under laboratory conditions, and the saturation of the three phases in the porous media sample can be controlled and adjusted; 2) With the help of probes such as acoustic wave and resistivity probes, rock physics experimental measurements of three-phase coexisting porous media can be carried out, followed by rock physics simulation experimental research on shallow gas and natural gas hydrate mixed zone, which serves the research on reservoir evaluation methods for shallow gas and natural gas hydrate mixed zone reservoirs. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 This invention provides a structural diagram of a device for preparing samples of three-phase coexisting porous media and measuring their acoustic and electrical properties. Figure 2 A flowchart of a method for preparing and measuring the acoustic and electrical properties of a three-phase coexisting porous medium sample provided by the present invention; Figure 3 A schematic diagram of the core sleeve provided by the present invention; Figure 4 Schematic diagram of the pore fluid state at different stages of the sample preparation scheme provided by the present invention; Among them, 1-water pump, 2-gas cylinder A, 3-reaction vessel, 4-containment pressure system, 5-hydraulic oil tank, 6-rubber sleeve, 7-vacuum pump, 8-fluid metering device, 9-temperature control system, 10-cooling liquid tank, 11-sample tank, 12-gas cylinder B, 13-first acoustic-electric composite probe, 14-second acoustic-electric composite probe, 15-acoustic-electric measurement and control system. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] See Figure 1 As shown, the device for preparing samples of three-phase coexisting porous media and measuring their acoustic and electrical properties includes: a sample chamber 11, and arranged in sequence from the inside to the outside of the sample chamber 11, such as a rubber sleeve 6, a hydraulic oil tank 5, a cooling liquid tank 10, and a reaction vessel 3. A first acoustic-electric composite probe 13 is installed at the top of the sample chamber 11, and a second acoustic-electric composite probe 14 is installed at the bottom of the sample chamber 11; a water pump 1 is connected to the top of the sample chamber 11 through a liquid pipeline, and gas cylinder A 2 and gas cylinder B 12 are connected to the top of the sample chamber 11 through a gas pipeline; a vacuum pump 7 is connected to the bottom of the sample chamber 11 through a gas pipeline, and a fluid metering device 8 is also connected to the bottom of the sample chamber 11. One end of the acoustic-electric measurement and control system 15 is connected to the first acoustic-electric composite probe 13, and the other end of the acoustic-electric measurement and control system 15 is connected to the second acoustic-electric composite probe 14. The confining pressure system 4 is connected to the hydraulic oil tank 5, and the temperature control system 9 is connected to the cooling liquid tank 10; Each gas and liquid pipeline is equipped with a corresponding valve.

[0023] See Figure 2 As shown, a method for preparing and measuring the acoustic and electrical properties of a three-phase coexisting porous medium sample, using the aforementioned apparatus for preparing and measuring the acoustic and electrical properties of a three-phase coexisting porous medium sample, includes the following steps: S1. Load the porous media sample into the sample chamber 11, close the reaction vessel 3, and close all pipeline valves; S2. Open the vacuum pump 7 and the valve connected to it to perform vacuum treatment on the porous medium sample in the sample chamber 11. After the vacuum treatment is completed, close the valve connected to the vacuum pump 7. S3. Open water pump 1 and the valve connected to it to fill the pore space of the porous medium sample with water, and then close the corresponding valve. S4. Open gas cylinder A2 and its connected valves, as well as fluid metering device 8 and its valves. Gas A displaces the aqueous solution in the pores, and record the water output of gas cylinder A2. That is, the volume of gas A injected; S5. Close gas cylinder A2 and its connected valves, open gas cylinder B12 and its connected valves. Gas B begins to enter the pores of the porous medium sample, displacing the aqueous solution from one end of the fluid metering device 8. Measure the outflow of water from gas cylinder B12. That is, the volume of gas B injected; V w ’

[0024] S6. Close gas cylinder B12 and its connected valves, as well as fluid metering device 8 and its valves; S7. Hydraulic oil is injected into the hydraulic oil tank 5 through the confining pressure system 4. The hydraulic oil transmits pressure to the side of the porous medium sample through the rubber sleeve 6 to form confining pressure. S8. Reopen water pump 1 and the valve connected to it to apply pore pressure to the porous medium sample through water pump 1 and keep the pore pressure constant. S9. Cooling liquid is injected into cooling liquid tank 10 for circulation through temperature control system 9 to control the temperature of reactor 3; S10. Under steady-state conditions, the pore space of the porous medium sample is a three-phase medium consisting of water, gas B, and gas A hydrates. S11. Based on the amount of substance of gas A injected in S4 and the volume of gas B injected in S5, calculate the amount and volume of the generated hydrate, and then calculate the saturation of the three-phase medium of water, gas B, and gas A hydrate in the pore space of the porous medium sample under steady-state conditions. S12. After the porous medium sample is formed, the first acoustic-electric composite probe 13 and the second acoustic-electric composite probe 14 are controlled by the acoustic-electric measurement and control system 15 to measure the resistance R and the sound wave propagation time Δt of the porous medium sample, so as to obtain the resistivity and sound wave velocity of the porous medium sample.

[0025] Specifically, temperature control in S9 is to ensure that the temperature and pore pressure conditions are suitable for gas A to form hydrates while gas B cannot form hydrates.

[0026] For details, see Figure 3 As shown, when preparing samples, for porous media such as consolidated rocks, the material can be directly processed into regular samples. For loose porous media samples, a shell can be made of a specified solid material, and the loose porous media sample can be placed inside the specially made shell. The material of the shell depends on the nature of the experiment to be conducted. Several vent holes need to be machined on the shell to ensure that gas can enter the pore space of the porous media from outside the shell. A breathable but waterproof membrane (such as the fleece fabric in medical masks) needs to be added to the inner surface of the shell to ensure that water in the porous media does not flow out through the vent holes.

[0027] Specifically, the porous media sample in S3 has a water saturation of 100%.

[0028] Furthermore, in S4, after a certain period of time, gas cylinder A2 and its connected valve are closed. At this time, the fluids in the pore space of the porous medium sample are gas A and water, and the saturation of the two fluids is:

[0029] in, The porosity of the porous medium sample. This represents the water output of cylinder A. Water saturation Let be the saturation level of gas A.

[0030] Furthermore, in S5, after a certain period of time, gas cylinder B12 and its connected valve are closed. At this time, the fluids in the pore space of the porous medium sample are gas A, gas B, and water, and the saturation of the three fluids is:

[0031] in, The porosity of the porous medium sample. This represents the water output of cylinder A. This represents the water output from gas cylinder B. Water saturation Let be the saturation level of gas A. Let be the saturation level of gas B.

[0032] Furthermore, in S11, the saturation of the three-phase medium consisting of water, gas B, and gas A hydrates in the pore space of the porous medium sample under steady-state conditions is calculated as follows: The molecular molar mass of gas A is The density is The volume is The amount of substance of gas A is:

[0033] During the formation of hydrate from gas A, one gas molecule forms a complex. X If there are 1 water molecule, then the molar mass of its hydrate is:

[0034] Volume is The amount of gas A that can form a hydrate is... n ; The density of hydrates is The volume of the hydrate formed is then... ; Therefore, the saturation of the hydrate three-phase medium under steady state is: The saturation level of gas B is Water saturation is ,in, The porosity of the porous medium sample. This represents the water output of gas cylinder B.

[0035] Specifically, because different gases require different temperature and pressure conditions to form hydrates, maintaining suitable temperature and pore pressure conditions allows for the formation of hydrates corresponding to gas A, while gas B will not form hydrates. During hydrate formation, the pore pressure drop caused by gas consumption is replenished by a water pump.

[0036] Specifically, under steady-state conditions, the three phases within the pores of the porous medium are water (liquid), a hydrate of gas A (solid), and gas B (gas). The saturation level of the hydrate of gas A is... Since gas B did not form a hydrate, the saturation level of gas B remains at [value missing]. Since the pore pressure is maintained by replenishing water after gas A is consumed, the water saturation level is: .

[0037] Furthermore, the first acoustic-electric composite probe 13 and the second acoustic-electric composite probe 14 in S12 serve as impedance measurement electrodes or as sound wave transmitting and receiving probes.

[0038] Specifically, one serves as the transmitting probe and the other as the receiving probe, with no restrictions on their relative vertical positions.

[0039] Furthermore, the formulas for the resistivity and acoustic velocity of the porous medium sample in S12 are as follows:

[0040] in, L The length of the porous medium sample. S The cross-sectional area of ​​the porous medium sample is... R For resistance, For the time required for sound wave transmission, v For the speed of sound waves, is the resistivity.

[0041] For details, see Figure 4 As shown, by controlling the intake of two gases (gas A and gas B), the saturation of the gas, water, and hydrate phases in the steady-state sample can be adjusted.

[0042] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0043] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for three-phase coexistence porous media sample preparation and acoustoelectric property measurement, characterized in that, The apparatus for implementing the method includes: a sample chamber (11), with a rubber sleeve (6), a hydraulic oil tank (5), a cooling liquid tank (10), and a reaction vessel (3) arranged sequentially from the inside to the outside of the sample chamber (11). The top of the sample chamber (11) is equipped with a first acoustic-electric composite probe (13), and the bottom of the sample chamber (11) is equipped with a second acoustic-electric composite probe (14); the top of the sample chamber (11) is connected to a water pump (1) through a liquid pipeline, and the top of the sample chamber (11) is connected to gas cylinder A (2) and gas cylinder B (12) through a gas pipeline; the bottom of the sample chamber (11) is connected to a vacuum pump (7) through a gas pipeline, and the bottom of the sample chamber (11) is also connected to a fluid metering device (8); One end of the acoustic-electric measurement and control system (15) is connected to the first acoustic-electric composite probe (13), and the other end of the acoustic-electric measurement and control system (15) is connected to the second acoustic-electric composite probe (14); The confining pressure system (4) is connected to the hydraulic oil tank (5), and the temperature control system (9) is connected to the cooling liquid tank (10); Corresponding valves are installed on each gas and liquid pipeline; The measurement method includes the following steps: S1. Load the porous media sample into the sample chamber (11), close the reactor (3), and close all pipeline valves; S2. Open the vacuum pump (7) and the valve connected to it to perform vacuum treatment on the porous medium sample in the sample chamber (11). After the vacuum treatment is completed, close the valve connected to the vacuum pump (7). S3. Open the water pump (1) and the valve connected to it to fill the pore space of the porous medium sample with water, and then close the corresponding valve. S4, open the gas cylinder A (2) and its connected valve and the fluid metering device (8) and its valve, the gas A displaces the aqueous solution in the pores, record the water discharge of the gas cylinder A (2) ; S5. Close gas cylinder A (2) and its connected valves, and open gas cylinder B (12) and its connected valves. Gas B begins to enter the pores of the porous medium sample, displacing the aqueous solution from one end of the fluid metering device (8). Measure the outflow of water from gas cylinder B (12). ; S6. Close gas cylinder B (12) and its connected valves, as well as the fluid metering device (8) and its valves; S7. Hydraulic oil is injected into the hydraulic oil tank (5) through the confining pressure system (4). The hydraulic oil transmits pressure to the side of the porous medium sample through the rubber sleeve (6) to form confining pressure. S8. Open the water pump (1) and the valve connected to it again, and apply pore pressure to the porous medium sample through the water pump (1) to keep the pore pressure constant. S9. The cooling liquid is injected into the cooling liquid tank (10) through the temperature control system (9) for circulation, and the temperature of the reactor (3) is controlled. S10. Under steady-state conditions, the pore space of the porous medium sample is a three-phase medium consisting of water, gas B, and gas A hydrates. S11. Based on the amount of substance of gas A injected in S4 and the volume of gas B injected in S5, calculate the amount and volume of the generated hydrate, and then calculate the saturation of the three-phase medium of water, gas B, and gas A hydrate in the pore space of the porous medium sample under steady-state conditions. S12. After the porous medium sample is formed, the first acoustic-electric composite probe (13) and the second acoustic-electric composite probe (14) are controlled by the acoustic-electric measurement and control system (15) to measure the resistance R and the sound wave transmission time Δt of the porous medium sample, so as to obtain the resistivity and sound wave velocity of the porous medium sample.

2. The method of claim 1, wherein, In S4, after a certain period of time, gas cylinder A (2) and its connected valve are closed. At this time, the fluid in the pore space of the porous medium sample is gas A and water, and the saturation of the two fluids is: wherein, is the porosity of the porous medium sample, is the water production of gas cylinder A, is the water saturation, is the saturation of gas A.

3. The method of claim 1, wherein, In S5, after a certain period of time, gas cylinder B (12) and its connected valve are closed. At this time, the fluids in the pore space of the porous medium sample are gas A, gas B, and water. The saturation of the three fluids is: in, The porosity of the porous medium sample. This represents the water output of cylinder A. This represents the water output from gas cylinder B. This represents the water saturation level. Let be the saturation level of gas A. Let be the saturation level of gas B.

4. The method of claim 1, wherein, In S11, the saturation of the three-phase medium consisting of water, gas B, and gas A hydrates in the pore space of the porous medium sample under steady-state conditions is calculated as follows: The molecular molar mass of gas A is The density is The volume is The amount of substance of gas A is: During the formation of hydrate from gas A, one gas molecule forms a complex. X If there are 1 water molecule, then the molar mass of its hydrate is: The volume of gas A can be The amount of substance of the hydrate-forming substance of gas A can be n ; The density of the hydrate is The volume of the hydrate formed is then ; Therefore, the hydrate saturation at steady state is The saturation level of gas B is Water saturation is ,in, The porosity of the porous medium sample. This represents the water output of gas cylinder B.

5. The method of claim 1, wherein, The first acoustic-electric composite probe (13) and the second acoustic-electric composite probe (14) in S12 serve as impedance measurement electrodes or as acoustic wave transmitting and receiving probes.

6. The method of claim 1, wherein, The formulas for the resistivity and acoustic velocity of the porous medium sample in S12 are as follows: in, L The length of the porous medium sample. S The cross-sectional area of ​​the porous medium sample is... R For resistance, For the time required for sound wave transmission, v For the speed of sound waves, is the resistivity.

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