Air-tight seal test device for cavity top position detection and cavity top position detection method thereof

Abstract

The invention provides an air-tight seal test device for cavity top position detection and a cavity top position detection method thereof. The device comprises a variable-diameter flange, an air injection pipeline and a pressure gauge, the method is suitable for the air-tight seal test device for cavity top position detection, and comprises the following steps: S1, connecting cavity opening equipment of the salt cavern; s2, nitrogen injection and pressure boosting; s3, measuring a gas-halogen interface; and S4, drawing a curve graph of the nitrogen pressure of the cavity opening of the salt cavern and the depth of the gas-halogen interface, so that the operation is simple, and the highest position of the salt cavern top of a single well and a single cavity can be accurately detected.

Description

Technical Field

[0001] The invention relates to the technical field of underground salt cavern storage engineering, and in particular to an airtightness test device for detecting a cavern top position and a cavern top position detection method thereof. Background Art

[0002] Due to the inclination of the strata, there is an obvious partial dissolution phenomenon in the process of water dissolution of salt caverns, resulting in the highest point of the salt cavern not being the position where the injection and production wells originally entered the cavern. At present, the domestic understanding of the morphology of salt cavern cavities mostly adopts sonar cavity measurement, three-dimensional seismic and other testing methods. Due to the limitations of sonar detection equipment, when the underground cavity morphology range exceeds the morphology range detectable by sonar, the sonar cavity measurement cannot detect the highest position of the salt cavern cavity top. When performing three-dimensional seismic detection, it is often necessary to understand the distribution morphology of the salt cavern cavity in detail and set the three-dimensional seismic wiring range in a targeted manner. However, the fracturing range of the fracturing well is difficult to predict, and the distribution of the cavity formed is also complex and changeable. Therefore, it often happens that the cavity boundary measured by three-dimensional seismic has exceeded the three-dimensional seismic wiring range, resulting in the inability to detect the highest position of the salt cavern cavity top. At the same time, there are systematic errors in the burial depth of the cavity detected by three-dimensional seismic.

[0003] Since the buried depth of the top of the salt cavern is unknown, there are certain risks in the design of underground salt cavern storage pressure, and it also brings difficulties to the location setting of injection and production wells. How to obtain the buried depth of the cavern top has positive significance. Summary of the invention

[0004] In order to solve the above technical problems, one of the technical solutions adopted by the present invention is: an airtight test device for detecting the position of the cavity top, an injection and production pipe string 1 and an annular packer 2 are provided in the injection and production well, the injection and production pipe string 1 is vertically inserted into the cavity of the salt cavern; the annular packer 2 is located in the gap between the injection and production pipe string 1 and the inner wall of the cavity of the salt cavern; the device is installed at the cavity top of the salt cavern, and the device comprises:

[0005] A reducing flange, which is installed on the injection and production pipe string 1;

[0006] A gas injection pipeline, which is installed on a reducing flange and has one end extending into the injection and production pipe string 1;

[0007] The pressure gauge 3 is installed on the reducing flange and is used to monitor the pressure in the injection and production pipe string 1 after gas injection.

[0008] Furthermore, the other end of the gas injection pipeline is connected to an external nitrogen production device;

[0009] A gate valve is provided on the gas injection pipeline to control the amount of gas intake.

[0010] Another technical solution adopted by the present invention is: a cavity top position detection method, which is applicable to the above-mentioned gas sealing test device for cavity top position detection, and the method comprises:

[0011] S1, equipment connection of the salt cavern cavity mouth;

[0012] S2, nitrogen injection to increase pressure;

[0013] S3, gas-halogen interface measurement;

[0014] S4. Draw a graph of the nitrogen pressure at the salt cavern cavity and the depth of the gas-brine interface.

[0015] Furthermore, in S1, preparations are made for going down into the well, and a reducing flange, a gate valve, a gas injection pipeline and a pressure gauge 3 are installed at the cavity opening of the salt cavern; and pressure tests are performed on the connection parts of the wellhead equipment to ensure that the pressure tests are qualified.

[0016] Further, in S2, the gas injection gate valve is opened, and nitrogen is injected into the injection and production pipe string 1 through the existing nitrogen generator;

[0017] When nitrogen is injected into the cavity entry point of injection and production pipe string 1, the gas injection gate valve is closed.

[0018] Furthermore, in S3, an existing optical fiber or neutron logging instrument is lowered into the cavity of the salt cavern to continuously read the gas-halogen interface depth during the nitrogen injection and pressure raising process.

[0019] Further, in S4, the inflection point of the curve of the nitrogen pressure at the cavity mouth of the salt cavern and the depth of the gas-brine interface under the monitoring data of the pressure gauge 3 and the gas-liquid interface is the highest position of the salt cavern cavity top.

[0020] The advantages and positive effects of the present invention are: the method is simple to operate and can accurately detect the highest position of the salt cavern roof of a single well and single cavity. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of a gas-tight test device for detection at the cavity top position;

[0022] Figure 2 A schematic diagram of a gas-tightness test device for detecting the position of the cavity top after nitrogen injection;

[0023] Figure 3 Physical process diagram of the airtight test device for the mathematical model of liquid elastic compression;

[0024] Figure 4 Physical process diagram of the airtight test device for the mathematical model of the liquid column pressure;

[0025] Figure 5 Monitor the time history graph for the pressure gauge;

[0026] In the figure: 1. Injection and production pipe string; 2. Annular packer; 3. Pressure gauge. DETAILED DESCRIPTION

[0027] In order to better understand the present invention, the present invention is further described below in conjunction with specific embodiments and drawings.

[0028] Example 1

[0029] like Figure 1-2 As shown, an airtight test device for detecting the position of the cavity top is provided in the injection and production well with an injection and production pipe string 1 and an annular packer 2, the injection and production pipe string 1 is vertically inserted into the cavity of the salt cavern; the annular packer 2 is located in the gap between the injection and production pipe string 1 and the inner wall of the cavity of the salt cavern; the device is installed at the cavity top of the salt cavern, and the device includes:

[0030] A reducing flange, which is installed on the injection and production pipe string 1;

[0031] A gas injection pipeline, which is installed on a reducing flange and has one end extending into the injection and production pipe string 1;

[0032] The pressure gauge 3 is installed on the reducing flange and is used to monitor the pressure in the injection and production pipe string 1 after gas injection.

[0033] Specifically, the test pressure gauge is a high-precision and high-density pressure gauge with an accuracy of up to 0.0001 MPa, and data can be read in seconds.

[0034] Furthermore, the other end of the gas injection pipeline is connected to an external nitrogen production device;

[0035] The annular packer 2 is filled with protective fluid.

[0036] A gate valve is provided on the gas injection pipeline to control the amount of gas intake.

[0037] Example 2

[0038] A cavity top position detection method, which is applicable to the gas sealing test device for cavity top position detection described in the above embodiment 1, comprises:

[0039] S1, equipment connection of the salt cavern cavity mouth;

[0040] S2, nitrogen injection to increase pressure;

[0041] S3, gas-halogen interface measurement;

[0042] S4. Draw a graph of the nitrogen pressure at the salt cavern cavity and the depth of the gas-brine interface.

[0043] Furthermore, in S1, preparations are made for going down into the well, and a reducing flange, a gate valve, a gas injection pipeline and a pressure gauge 3 are installed at the cavity opening of the salt cavern; and pressure tests are performed on the connection parts of the wellhead equipment to ensure that the pressure tests are qualified.

[0044] Further, in S2, the gas injection gate valve is opened, and nitrogen is injected into the injection and production pipe string 1 through the existing nitrogen generator;

[0045] When nitrogen is injected into the cavity entry point of injection and production pipe string 1, the gas injection gate valve is closed.

[0046] Furthermore, in S3, an existing optical fiber or neutron logging instrument is lowered into the cavity of the salt cavern to continuously read the gas-halogen interface depth during the nitrogen injection and pressure raising process.

[0047] Further, in S4, the inflection point of the curve of the nitrogen pressure at the cavity mouth of the salt cavern and the depth of the gas-brine interface under the monitoring data of the pressure gauge 3 and the gas-liquid interface is the highest position of the salt cavern cavity top.

[0048] Its working principle: The salt cavern top position detection technology based on the wellhead pressure data of the injection and production well is to uniformly inject nitrogen at the wellhead until the interface between nitrogen and brine approaches the wellbore entry point. In this process, the high-pressure gas has two physical effects: the first is to compress the saturated brine; the second is to support the saturated brine column;

[0049] The first effect runs through the entire process and may be nonlinear elastic compression; the second one only exists after the gas-liquid interface is lower than the cavity top, and the gas begins to support the brine column above the gas-liquid interface. The pressure required by the first physical effect is defined as P1, and the pressure required by the second physical effect is defined as P2.

[0050] like Figure 3-4 As shown, 1. Obtain the mathematical model of liquid elastic compression. The first physical action is the elastic compression of the liquid, and its mathematical model is:

[0051]

[0052] Among them, E v is the bulk compression modulus; dP is the pressure increment.

[0053] The initial brine pressure is 0, and the initial brine volume is V0; the gas pressure of the compressed brine is P1, and the brine volume is V i ; Integrate the above formula to get:

[0054]

[0055] Let ΔV = V i -V0, substituting into the above formula, we can get

[0056]

[0057] Will Expand by level

[0058]

[0059] Since the volume of brine in the wellbore is small compared to the overall brine volume, When the amount is small, the small amount above the second order can be ignored, and we get

[0060]

[0061] 2. Obtain the mathematical model of the liquid column pressure. The second physical effect is to support the liquid column pressure, and its mathematical model is:

[0062] P2=ρgΔH

[0063] ΔH=H i -H0

[0064] Where: ρ is the density of saturated brine, 1209.6 kg / m 3 ; g is the acceleration due to gravity, m / s 2 ;H i is the depth of the gas-liquid interface, m; H i is the depth of the cavity top, m; ΔH is the height difference between the gas-liquid interface and the cavity top, m;

[0065] When the gas-liquid interface H i When it is above the cavity top H0, there is only elastic compression of the liquid; when the gas-liquid interface H i When it is below the cavity top H0, in addition to the elastic compression of the liquid, there is also support from the pressure of the liquid column, that is,

[0066]

[0067] Under the pressure gauge monitoring data, a data-intensive pressure monitoring time curve can be obtained, such as Figure 5 As shown in the figure, when the gas-liquid interface crosses the cavern top, due to the different pressure equations, the monitored pressure value will show a significant change in the pressure change trend at a certain time Ti. At this moment, the gas-liquid interface crosses the cavern top. The gas-liquid interface data monitored at this moment is the highest position of the salt cavern top.

[0068] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of this patent.

Claims

1. An airtight test device for detecting the position of a cavity top, wherein an injection and production pipe string (1) and an annular packer (2) are provided in an injection and production well, wherein the injection and production pipe string (1) is vertically inserted into the cavity of a salt cavern; and the annular packer (2) is located in the gap between the injection and production pipe string (1) and the inner wall of the cavity of the salt cavern; and characterized in that: The device is installed at the top of the salt cavern and includes: A reducing flange, which is mounted on the injection and production pipe string (1); A gas injection pipeline, which is installed on the reducer flange and has one end extending into the injection and production pipe string (1); A pressure gauge (3) is installed on the reducing flange and is used to monitor the pressure in the injection and production pipe string (1) after gas injection.

2. The airtightness test device for detecting the position at the cavity top according to claim 1, characterized in that: The other end of the gas injection pipeline is connected to an external nitrogen production device; A gate valve is provided on the gas injection pipeline to control the amount of gas intake.

3. A cavity top position detection method, characterized in that: The method is applicable to the gas sealing test device for detecting the position of the cavity top according to any one of claims 1 to 2, and the method comprises: S1, equipment connection of the salt cavern cavity mouth; S2, nitrogen injection to increase pressure; S3, gas-halogen interface measurement; S4. Draw a graph of the nitrogen pressure at the salt cavern cavity and the depth of the gas-brine interface.

4. The cavity top position detection method according to claim 3, characterized in that: In S1, preparations are made for going down into the well, and a reducing flange, a gate valve, a gas injection pipeline and a pressure gauge (3) are installed at the cavity opening of the salt cavern; and pressure tests are performed on the connection parts of the wellhead equipment to ensure that the pressure tests are qualified.

5. The cavity top position detection method according to claim 4, characterized in that: In S2, the gas injection valve is opened, and nitrogen is injected into the injection and production pipe string (1) through an existing nitrogen generator; When nitrogen is injected into the inlet point of the injection and production pipe string (1), the injection valve is closed.

6. The cavity top position detection method according to claim 5, characterized in that: In S3, an existing optical fiber or neutron logging instrument is lowered into the cavity of the salt cavern to continuously read the gas-halogen interface depth during the nitrogen injection and pressure increase process.

7. The cavity top position detection method according to claim 6, characterized in that: In S4, the inflection point of the curve of the nitrogen pressure at the cavity mouth of the salt cavern and the depth of the gas-brine interface under the monitoring data of the pressure gauge (3) and the gas-liquid interface is the highest position of the salt cavern cavity top.

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