Simulation device for identifying shallow gas

Abstract

The invention discloses a simulation device for identifying shallow gas. The device comprises a reaction kettle, a shallow flow layer is arranged in the reaction kettle, a pressure-controllable closed air bag is arranged in the shallow flow layer, and the pressure-controllable closed air bag is connected with external gas and a pressure gauge; the sound wave transmitting and receiving assembly is provided with three groups of transmitters and three groups of receivers, two groups of transmitters are arranged at the top of the pressure-controllable closed air bag, three groups of receivers are arranged at the top of the reaction kettle, and the rest group of transmitters are arranged in the shallow flow layer and used for measuring ultrasonic signals of the shallow gas stratum; and the processor digitizes the ultrasonic signal and is used for identifying the shallow gas. Acoustic wave transmitting and receiving equipment is additionally arranged in the simulation device for identifying the shallow gas, monitoring parameters are increased, and multi-source data such as longitudinal wave velocity, frequency and amplitude can be collected. The device can simulate more complex marine environment, water depth and water temperature, and can simulate stratums with different holes, seepage and saturation, covering layers with different thicknesses and the like.

Description

Technical Field

[0001] The present invention relates to the field of oil and gas field development, and more particularly to a simulation device for identifying shallow gas. Background Art

[0002] The potential for shallow gas geological hazards is typically assessed through wellsite surveys using geophysical methods such as high-resolution seismic, multi-beam sounding, side-by-side sonar, and shallow stratigraphic profiling. This combination of methods clearly defines the seafloor topography within the wellsite. This approach reveals how the presence of shallow gas affects the propagation velocity of acoustic waves in the rock and soil, as well as how pressure changes within the shallow gas layer affect the propagation velocity of acoustic waves, enabling more accurate predictions of shallow gas geological hazards. Common methods for identifying the size and depth of shallow gas deposits during well logging include neutron gamma curve overlap and compensated neutron-compensated density curve overlap. Based on seismic wavefield variations and considering the viscosity of the seafloor medium, a two-dimensional viscoelastic wave equation is developed, establishing a shallow seafloor gas model that incorporates physical parameters such as density and quality factor. Internationally, MIP-CPT technology, supplemented by various other geophysical exploration methods, can accurately identify shallow seafloor gas deposits. While MIP-CPT offers advantages over traditional shallow gas detection methods in terms of speed, intuitiveness, and multi-data availability, it also suffers from limited accuracy. An improved AVO identification method has been proposed in China to predict the distribution of shallow gas. Building on conventional AVO identification technology, this method uses a scanning method to determine the angular range within a gather, selecting angle gathers that effectively reflect shallow-layer information. Seismic amplitudes vary at different angles, influenced by the presence of gas. Based on this, energy envelope difference profiles are calculated at different angles to identify favorable gas-bearing zones. However, this method is not suitable for large-scale leak detection and has limitations.

[0003] Publication number CN114280099A relates to an experimental device for evaluating the thermoacoustic properties of deepwater drilling fluids containing hydrates. Publication number CN111827909A relates to an active control method and control device for wellbore pressure in open-circuit drilling of natural gas hydrates in the sea. Publication number CN111608651A relates to a comprehensive detection device for the mechanical properties of seabed sediments and shallow gas. Publication number CN106814166A relates to an experimental device for evaluating the formation and aggregation behavior of hydrates in deepwater drilling. In summary, at present, in view of the geological characteristics and technical difficulties of deepwater and high-temperature and high-pressure shallow drilling, there has been no full-scale field simulation test on shallow gas geological hazards and research on key technologies for shallow gas prediction and prevention. There is no detailed process and optimization description in the existing technology, and there is a lack of small-scale simulation tests for the identification of shallow gas geological hazards at home and abroad. Most experimental methods are relatively simple and the monitoring parameters are relatively single, which cannot meet the needs of safe and efficient well construction in deepwater, especially ultra-deepwater areas. Summary of the Invention

[0004] In response to the above-mentioned defects or improvement needs of the prior art, the present invention provides a simulation device for identifying shallow gas. Its purpose is to simulate shallow gas-containing strata in different sea areas by designing an indoor experimental device, carry out experimental research on shallow gas strata identification under different conditions, explore the change law of key parameters for shallow gas identification under different simulation conditions, and guide the drilling construction site to accurately identify the distribution area of shallow geological disasters and the risk level of shallow geological disasters in advance, so as to effectively avoid well construction in shallow geological disaster areas or take well control measures in advance to reduce well control risks.

[0005] To achieve the above object, according to one aspect of the present invention, a simulation device for identifying shallow gas is provided, the device comprising:

[0006] A reactor, wherein a shallow flow layer is provided in the reactor, a pressure-controlled sealed airbag is provided in the shallow flow layer, and the pressure-controlled sealed airbag is connected to external gas and a pressure gauge;

[0007] The acoustic wave transmitting and receiving component is provided with three groups of transmitters and three groups of receivers, wherein two groups of transmitters are arranged on the top of the controllable pressure sealed airbag, three groups of receivers are arranged on the top of the reactor, and the remaining group of transmitters is arranged in the shallow flow layer, for measuring the acoustic wave characteristics of the shallow gas formation.

[0008] As a further improvement and supplement to the above solution, the present invention also includes the following additional technical features.

[0009] Preferably, the reactor further comprises:

[0010] marine layers, overburden, and underlying strata;

[0011] Valves are respectively provided on the sides of the seawater layer, the cover layer and the underlying stratum, and the valves control the seawater capacity.

[0012] Preferably, the controllable pressure-sealed airbag includes a soil-filled airbag and an air-filled airbag. The filler in the soil-filled airbag is a sand-clay mixed soil, and the soil body of the filler in the soil-filled airbag is consistent with the soil body of the shallow gas stratum. The filling gas in the air-filled airbag is nitrogen.

[0013] Preferably, the soil in the soil-filled air bag is a soil sample with a density of 1.6-2.2 g / cm3, a porosity of 15%-60%, a moisture content of 5%-50%, and a saturation of 30%-100%.

[0014] Preferably, the pressure in the inflatable airbag ranges from 0.5 MPa to 10 MPa.

[0015] Preferably, sound wave emitters are provided on the surfaces of the air-filled airbag and the soil-filled airbag.

[0016] Preferably, the device further comprises a constant temperature water bath assembly, the reactor is placed in the constant temperature water bath assembly, and the constant temperature water bath assembly is used to adjust the temperature inside the reactor.

[0017] Preferably, the covering layer includes at least two types of covering layers, the covering layers are simulated soil layers, and the soil layer materials of each covering layer are different.

[0018] Preferably, the device further comprises a condensation component, which is arranged on the top of the seawater layer, and is used to adjust the temperature of the seawater, and the condensation component comprises a resistance wire.

[0019] Preferably, the device further comprises a pressurizing component, which is arranged on top of the seawater layer and is used to pressurize the interior of the reactor.

[0020] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:

[0021] The present invention adds acoustic wave transmitting and receiving equipment to the simulation device for identifying shallow gas, increases monitoring parameters, and can collect multi-source data such as longitudinal wave velocity, frequency, and amplitude. The improvements and enhancements based on the previous work are mainly reflected in the following three aspects:

[0022] (1) More parameters are monitored, including longitudinal wave velocity, amplitude, frequency, phase and wave impedance, rather than just the traditional wave velocity.

[0023] (2) The ocean environment that can be simulated is more complex, including water depth (pressure), water temperature, etc.

[0024] (3) The strata that can be simulated are more complex, and strata with different porosity, permeability, and saturation, as well as overburden layers of different thicknesses, can be simulated. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0026] Figure 1 This is a schematic diagram of a simulation device for identifying shallow gas provided in this embodiment;

[0027] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0028] 1—reactor, 2—shallow flow layer, 3—controllable pressure sealed airbag, 4—acoustic wave transmitting and receiving assembly, 41—transmitter, 42—receiver, 5—cover layer, 51—first cover layer, 52—second cover layer, 6—seawater layer, 7—converter, 8—underlying stratum, 9—condensation assembly, 10—processor. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0030] In the description of the present invention, the terms "inside", "outside", "longitudinal", "lateral", "upper", "lower", "top", "bottom", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention.

[0031] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0032] Example 1

[0033] This embodiment provides a simulation device for identifying shallow gas, such as Figure 1 As shown, the device includes:

[0034] A reactor 1, wherein a shallow flow layer 2 is provided in the reactor, a pressure-controlled sealed airbag 3 is provided in the shallow flow layer 2, and the pressure-controlled sealed airbag 3 is connected to external gas and a pressure gauge;

[0035] An acoustic wave transmitting and receiving assembly 4 is provided with three groups of transmitters 41 and three groups of receivers 42, wherein two groups of transmitters 41 are provided on the top of the controllable pressure sealed airbag, three groups of receivers 42 are provided on the top of the reactor 1, and the remaining group of transmitters 41 is provided in the shallow flow layer 2, for measuring the acoustic wave characteristics of the shallow gas formation;

[0036] The processor 10 digitizes the ultrasonic signal for identifying shallow gas.

[0037] Ultrasonic signals are emitted by transmitter 41. After passing through shallow gas formation 2, overburden 5, and seawater 6, they are received by receiver 42. Converter 7 converts them into digitized waveforms and records them in a computer. Shallow gas is identified based on the digitized waveforms, including but not limited to P-wave velocity, frequency, amplitude, and other multi-source data.

[0038] Figure 1 Except for the seawater layer, all other layers are soil. The shallow flow layer 2 is a fluid (water or gas) contained in a shallow, underconsolidated stratum, exhibiting high pressure characteristics. In this first embodiment, the shallow flow layer 2 is topped by two overburden layers: a first overburden layer 51 of mud and a second overburden layer 52 of sand.

[0039] The controllable pressure sealed airbags include two, one of which is a soil-filled airbag 31 and the other is an air-filled airbag 32, both of which are set in a shallow flow layer environment.

[0040] In combination with the embodiment of the present invention, there is also a preferred implementation scheme. Specifically, the reactor further includes:

[0041] seawater layer 6, overburden layer 5 and underlying strata 8;

[0042] Valves are respectively provided on the sides of the seawater layer 6, the cover layer 5 and the underlying stratum 8, and the valves control the seawater capacity.

[0043] In combination with the embodiment of the present invention, there is also a preferred implementation scheme. Specifically, the controllable pressure-sealed airbag 3 includes a soil-filled airbag 31 and an inflatable airbag 32. The filler in the soil-filled airbag 31 is a sand-clay mixed soil, and the soil body of the filler in the soil-filled airbag 31 is consistent with the soil body of the shallow gas stratum, and the filling gas in the inflatable airbag 32 is nitrogen.

[0044] The soil of the filling material in the soil-filled air bag 31 is consistent with the soil of the shallow gas stratum. The soil-filled air bag is used as a reference, i.e., a background value. The soil-filled air bag 31 is filled with soil according to the soil layer set in the shallow flow layer. The pressure of the inflated air bag 32 is not adjusted. The change of the ultrasonic signal of the monitoring air bag is detected when the seawater pressure is adjusted. The ultrasonic signal is recognized by the transducer.

[0045] In the field of ultrasound, transducers are primarily used to transmit and receive ultrasonic waves. They can identify the time, amplitude, frequency, and phase information of the echo signal.

[0046] In combination with the embodiment of the present invention, there is also a preferred implementation scheme. Specifically, the soil in the soil-filled air bag is selected to have a density of 1.6-2.2 g / cm 3 , soil samples with porosity of 15%-60%, moisture content of 5%-50%, and saturation of 30%-100%.

[0047] Prepare the experimental soil samples. In the process of preparing soil samples, the soil samples need to be screened, saturated with water, vibrated, compacted, etc. At the same time, the soil samples used must be homogeneous.

[0048] First, soil samples were removed for preliminary testing, and the soil was preliminarily selected for the experiment. The samples were then exposed to the sun, crushed, and sieved. The preliminarily selected soil samples were placed in a large test container. To ensure that the conditions of saturated submarine soil were simulated, water was added every 0.2m of soil sample filling. Once the water submerged the sample, it was vibrated with a vibrator. After 10 minutes of vibrating, a large weight was placed on the surface of the soil sample to pressurize it. After 2 hours of pressurized rest, the next layer of soil sample was placed until the container filled up completely. The container was then left to rest for approximately one week, allowing the soil to drain and consolidate. During this period, the soil samples were pressurized with an appropriate weight to simulate the pressure environment of submarine soil. After each test, the samples were vibrated for approximately 15 minutes and then left to rest for an additional 24 hours to stabilize and ensure consistent mechanical and physical properties. Soil samples from the container were then subjected to geotechnical testing, testing common physical parameters such as density, porosity, moisture content, and saturation.

[0049] In combination with the embodiment of the present invention, there is also a preferred implementation scheme. Specifically, the pressure range of the inflatable airbag is 0.5 MPa to 10 MPa.

[0050] A confining pressure range of 2 to 16 MPa was applied to the reactor to simulate different operating water depths and overburden pressures. After the confining pressure was applied, the pressure was first maintained at the minimum shallow gas overpressure. Then, an additional 0.5 to 10 MPa (approximately 5 to 100 atmospheres) was added to simulate a realistic experimental environment. Specifically, a high-pressure gas flowmeter was used to inject gas into the sealed airbag to increase the pressure. The injected gas pressure level was 0.5 to 10 MPa.

[0051] In combination with the embodiment of the present invention, there is also a preferred implementation scheme. Specifically, sound wave emitters 41 are provided on the surfaces of the air-filled airbag and the soil-filled airbag.

[0052] In combination with the embodiment of the present invention, there is also a preferred implementation scheme. Specifically, the device further includes a constant temperature water bath component, the reactor 1 is placed in the constant temperature water bath component, and the constant temperature water bath component is used to adjust the temperature inside the reactor.

[0053] In combination with the embodiment of the present invention, there is also a preferred implementation scheme. Specifically, the covering layer includes at least two covering layers, the covering layer is a simulated soil layer, and the soil layer material of each covering layer is different.

[0054] In the first embodiment, the first covering layer 51 is a mud layer, and the second covering layer 52 is a sand layer.

[0055] In combination with the embodiment of the present invention, there is also a preferred implementation scheme. Specifically, the device also includes a condensation component 9, which is arranged on the top of the seawater layer. The condensation component is used to adjust the seawater temperature, and the condensation component includes a resistance wire.

[0056] In combination with the embodiment of the present invention, there is also a preferred implementation scheme. Specifically, the device further includes a pressurizing component, which is arranged on the top of the seawater layer and is used to pressurize the interior of the reactor.

[0057] After the pressurizing assembly pressurizes the seawater, the acoustic wave transmitter 41 monitors the acoustic wave characteristics of the inflated airbag under different pressures, including longitudinal wave velocity, amplitude, frequency, phase and wave impedance.

[0058] The first embodiment of the present invention provides a simulation device for identifying shallow gas. The principle is to compact sand-clay mixtures of different porosities and densities, encapsulate them, and implant them into a soil-filled air bag in a high-pressure, low-temperature reactor. The soil-filled air bag serves as a reference, i.e., a background value. The corresponding soil is filled according to the different soil layers set in the shallow flow layer. The pressure of the inflated air bag is adjusted to monitor the results of transducer recognition under different air bag pressures, the results of recognition by two transmitters (two transmitters above the air bag and above the sea water), and the results of recognition by transmitters at different directions (the position on the transmitter plane is adjustable).

[0059] like Figure 1 As shown, the condensation device above the seawater layer 6 is used to regulate the seawater temperature, and the pressurizing device is used to pressurize the entire device to simulate the pressure of seawater in ultra-deepwater conditions. Data to be monitored can be added as needed, and corresponding sensors that can obtain relevant parameters can be added to the diagram. A wave generator can also be added to simulate seawater waves, and the processed results can be used to accurately identify shallow gas.

[0060] Example 2

[0061] The second embodiment provides a simulation experiment for identifying shallow gas using the simulation device for identifying shallow gas in the first embodiment. Data of sound waves at different pressure levels are collected in a high-pressure reactor.

[0062] S1: Sand-clay mixtures of varying porosity and density were compacted, sealed, and placed in two airbags within a high-pressure, low-temperature reactor. A soil-filled airbag served as a reference, or background value. Five flow layers were set up within the reactor to simulate the experimental environment: seawater, a primary overburden layer, a secondary overburden layer, a shallow flow layer, and the underlying stratum.

[0063] S2: After the reactor and the soil within the envelope are configured, different soils are filled according to the different soil layers set in the shallow flow layer. After the acoustic transducers are fixed to the reactor and the airbag, the lid is closed and the temperature inside the reactor is lowered to the target block temperature in a low-temperature constant-temperature water bath. The valve on the left releases seawater, the two condensing devices at the top regulate the seawater temperature, and the pressurizing device pressurizes the entire device to simulate the pressure of seawater in ultra-deepwater conditions.

[0064] S3: Apply a confining pressure in the range of 2 to 16 MPa to the reactor to simulate different operating water depths and overburden pressures. After the confining pressure is applied, gas is injected into the closed air bag through a high-pressure gas flow meter to increase the pressure. The injected gas pressure level is 0.5 MPa to 10 MPa.

[0065] S4: Acoustic transmitters are installed on the surface of the two airbags in the shallow flow layer. Another acoustic transmitter is installed in the shallow flow layer as a reference. The test results of the airbags in the experiment are transmitted back to the acoustic receiver outside the device through the acoustic receiver. The experimental results are finally sent to the processor for processing and analysis.

[0066] S5: Debug the acoustic wave measurement system in the reactor to test the shallow gas longitudinal wave velocity, frequency, amplitude, phase, and wave impedance under different confining pressures and shallow gas overpressure conditions applied to the airbag in the experiment, and transmit the results back to the processor for processing and analysis.

[0067] S6: Add a wave maker into the reactor to simulate seawater waves, observe the specific situation of the airbag after adding seawater waves, and finally transmit it back to the processor through the sound wave receiver. The processor accurately identifies shallow gas based on the processing results.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A simulation device for identifying shallow gas, characterized in that: The device comprises: A reactor, wherein a shallow flow layer is provided in the reactor, a pressure-controlled sealed airbag is provided in the shallow flow layer, and the pressure-controlled sealed airbag is connected to external gas and a pressure gauge; An acoustic wave transmitting and receiving assembly is provided with three groups of transmitters and three groups of receivers, wherein two groups of transmitters are provided on the top of the controllable pressure sealed airbag, three groups of receivers are provided on the top of the reactor, and the remaining group of transmitters is provided in the shallow flow layer for measuring ultrasonic signals of shallow gas formations; A processor is provided for digitizing the ultrasonic signal for identifying shallow gas.

2. The simulation device for identifying shallow gas according to claim 1, characterized in that: The reactor also includes: marine layers, overburden, and underlying strata; Valves are respectively provided on the sides of the seawater layer, the cover layer and the underlying stratum, and the valves control the seawater capacity.

3. The simulation device for identifying shallow gas according to claim 1, characterized in that: The controllable pressure sealed airbag includes a soil-filled airbag and an air-filled airbag. The filler in the soil-filled airbag is a sand-clay mixed soil, and the soil body of the filler in the soil-filled airbag is consistent with the soil body of the shallow gas stratum. The filling gas in the air-filled airbag is nitrogen.

4. The simulation device for identifying shallow gas according to claim 3, characterized in that: The soil in the soil-filled airbag has a density of 1.6-2.2 g / cm 3 , soil samples with porosity of 15%-60%, moisture content of 5%-50%, and saturation of 30%-100%.

5. The simulation device for identifying shallow gas according to claim 4, characterized in that: The pressure in the inflatable airbag ranges from 0.5 MPa to 10 MPa.

6. The simulation device for identifying shallow gas according to claim 5, characterized in that: Sound wave emitters are arranged on the surfaces of the air-filled airbag and the soil-filled airbag.

7. The simulation device for identifying shallow gas according to claim 1, characterized in that: The device further comprises a constant temperature water bath component, the reactor is placed in the constant temperature water bath component, and the constant temperature water bath component is used to adjust the temperature inside the reactor.

8. The simulation device for identifying shallow gas according to claim 2, characterized in that: The covering layer includes at least two types of covering layers, the covering layer is a simulated soil layer, and the soil layer material of each covering layer is different.

9. The simulation device for identifying shallow gas according to claim 8, characterized in that: The device further comprises a condensation component, which is arranged on the top of the seawater layer and is used to adjust the temperature of the seawater. The condensation component comprises a resistance wire.

10. The simulation device for identifying shallow gas according to claim 9, characterized in that: The device further comprises a pressurizing component, which is arranged on the top of the seawater layer and is used to pressurize the interior of the reactor.

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