Method for creating a cavity in a salt cavern gas storage reservoir

Abstract

The present invention relates to the technical field of cavity formation in salt cavern gas storage, and specifically relates to a method for forming a cavity in a salt cavern gas storage, which includes cavity segmentation, cavity formation in the first cavity section N1, cavity formation at the bottom of the second cavity section N2, protection of the bottom of the second cavity section N2, and cavity formation above the second cavity section N2. The first cavity section N1 and the second cavity section N2 are connected, and finally the brine is discharged to complete the overall cavity formation. By dividing the entire cavity into the first cavity section N1 and the second cavity section N2, after the cavity formation in the first cavity section N1 is completed, the cavity formation in the second cavity section N2 is carried out, reducing the contact time between the cavity bottom and the unsaturated brine. During the cavity formation process of the second cavity section N2, the bottom of the cavity is first corroded and formed, and then saturated brine is injected to protect the bottom of the cavity, further reducing the dissolution rate of the formed cavity bottom, shortening the dissolution time of the cavity bottom, protecting the shape of the cavity bottom, making the formed cavity bottom shape conform to the designed cavity bottom shape to the greatest extent, avoiding uncontrollable changes in the structural strength caused by the abnormal shape of the cavity bottom, and reducing potential safety hazards.

Description

Technical Field

[0001] The present invention relates to the technical field of cavity formation in salt cavern gas storage, and more particularly to a method for forming a cavity in a salt cavern gas storage. Background Art

[0002] Salt cavern reservoirs have characteristics such as low permeability and low porosity. They utilize the salt rock cavities left by solution mining for storing oil or natural gas. Salt cavern gas storage also has advantages such as high injection-production rate, large short-term throughput, low cushion gas volume, and complete recoverability, making it play a very important role in energy reserve and peak shaving emergency.

[0003] Utilizing the dissolvable characteristics of rock salt, the current cavity formation in salt cavern reservoirs generally adopts the solution mining method, forming the cavity integrally from bottom to top. Fresh water is transported to the bottom of the cavity, the salt layer is dissolved, and the brine is discharged. Then, the dissolution progresses gradually upward, and a resistance-capacitance agent is used to control the cavity shape. However, when forming the cavity gradually upward, there is always unsaturated brine at the pre-formed bottom of the cavity. Under the action of the unsaturated brine, the rock salt at the bottom of the cavity will dissolve, making it difficult to control the shape of the bottom of the cavity, resulting in the phenomenon of an irregular bottom of the cavity, causing a deviation between the shape of the entire cavity and the designed shape, and leading to an uncontrollable change in the structural strength. Therefore, there is an urgent need for a method for forming a cavity in a salt cavern gas storage to solve the above problems. Summary of the Invention

[0004] The present invention provides a method for forming a cavity in a salt cavern gas storage, comprising the following steps:

[0005] S1. Cavity segmentation: According to the depth of the pre-formed cavity, the pre-formed cavity is longitudinally divided into a first cavity segment N1 and a second cavity segment N2. The first cavity segment N1 includes a plurality of first cavities distributed longitudinally, and the second cavity segment N2 includes a second cavity located at the bottom of the first cavities.

[0006] S2. Cavity formation in the first cavity segment N1: The plurality of first cavities included in the first cavity segment N1 are formed from top to bottom in sequence until all the first cavities are connected, and then the brine is discharged, and the cavity formation in the first cavity segment N1 is completed.

[0007] S3. Cavity bottom formation in the second cavity segment N2: After the plurality of first cavities in the first cavity segment N1 are connected, a drill is used to drill to the bottom of the second cavity included in the second cavity segment N2, and then a first jet device is used to spray fresh water laterally and circumferentially rotate at the bottom of the second cavity. The fresh water dissolves the rock salt, and at the same time, the laterally sprayed fresh water exerts an impact force on the rock salt in the horizontal direction of the second cavity, accelerating the erosion of the horizontal direction of the bottom of the second cavity. After the bottom of the second cavity is formed, the unsaturated brine formed by dissolution is discharged.

[0008] S4. Protection of the bottom of the second cavity section N2: After the unsaturated brine at the bottom of the second cavity section N2 is drained, a protective agent is continuously injected into the bottom to slow down the dissolution rate of the rock salt at the bottom.

[0009] S5. Cavity formation above the second cavity section N2: After the protective agent injected at the bottom of the second cavity section N2 completely covers the bottom, the first jet device gradually moves upward along the bottom of the second cavity section N2 and rotates circumferentially to erode and dissolve the remaining rock salt above the second cavity section N2. The dissolved brine is discharged in real time until the cavity formation of the second cavity section N2 is completed and is completely connected to the first cavity section N1. After the cavity formation of the second cavity section N2 is completed, the brine in the first cavity section N1 and the second cavity section N2 is completely drained, and finally the overall cavity formation of the first cavity section N1 and the second cavity section N2 is completed.

[0010] Preferably, the ratio of the depth to the maximum diameter of each of the several first cavities included in the first cavity section N1 in the above step S1 is 1.1 - 1.2.

[0011] Preferably, the ratio of the depth to the maximum diameter of the second cavity included in the second cavity section N2 in the above step S1 is 0.5 - 0.7.

[0012] Preferably, for the cavity formation of each of the several first cavities included in the first cavity section N1 in the above step S2, the cavity formation of each first cavity includes the following steps:

[0013] Step S21a: Use a drill to drill to the bottom of the cavity, then inject fresh water to dissolve the rock salt and drain the brine.

[0014] Step S22a: Inject a solvent inhibitor into the cavity to effectively control the position where the fresh water dissolves the rock salt, so as to control the cavity shape and make a single first cavity fully formed.

[0015] Among them, the multiple first cavities included in the first cavity section N1 are formed in sequence from top to bottom.

[0016] Preferably, the solvent inhibitor is nitrogen.

[0017] Preferably, for the cavity formation of each of the several first cavities included in the first cavity section N1 in the above step S2, the cavity formation depth of each first cavity is 9 / 10 of the cavity depth, so that a dissolution and collapse layer is formed between adjacent cavities in the first cavity section N1. After the cavity below the dissolution and collapse layer is formed, the dissolution and collapse layer is in a suspended state. When the fresh water dissolves the cavity below, the suspended dissolution and collapse layer is accelerated to collapse and peel off under the influence of gravity.

[0018] Preferably, a second jet device is used to directly erode the suspended dissolution and collapse layer.

[0019] Preferably, for the cavity formation of each of the several first cavities included in the first cavity section N1 in the above step S2, the cavity formation of each first cavity includes the following steps:

[0020] Step S21b: Drill to the bottom of the first cavity with a drill tool, then use a jet device to spray fresh water laterally and rotate circumferentially to dissolve the rock salt with fresh water.

[0021] Step S22b: The fresh water sprayed laterally exerts an impact force on the rock salt in the horizontal direction of the first cavity, accelerating the dissolution of the rock salt in the horizontal direction of the first cavity, increasing the forming speed in the horizontal direction of the first cavity, and the second jet device gradually moves upward along the bottom of the cavity, eroding and dissolving the rock salt in the first cavity from bottom to top step by step, and discharging the brine to form a single first cavity.

[0022] Among them, the multiple first cavities included in the first cavity section N1 are formed successively from top to bottom.

[0023] Preferably, the brine dissolved in the above step S5 is pumped out by a jet pump, and the input end of the jet pump is located at the liquid level of the protective agent in the above step S4..

[0024] Compared with the prior art, the advantages of the present invention are as follows:

[0025] By dividing the entire cavity into a first cavity section N1 and a second cavity section N2, after the cavity formation of the first cavity section N1 is completed, then the cavity formation of the second cavity section N2 is carried out, reducing the contact time between the cavity bottom and the unsaturated brine. And during the cavity formation process of the second cavity section N2, first, the cavity bottom is eroded and formed, and then saturated brine is injected to protect the cavity bottom, further reducing the dissolution speed of the cavity bottom after formation, shortening the dissolution time of the cavity bottom, protecting the shape of the cavity bottom, making the formed cavity bottom shape conform to the designed cavity bottom shape to the greatest extent, avoiding uncontrollable changes in the structural strength caused by the abnormal shape of the cavity bottom, and reducing potential safety hazards. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings are not intended to be drawn to scale. In the drawings, each identical or approximately identical component shown in each figure may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Now, embodiments of various aspects of the present invention will be described by way of example and with reference to the drawings, wherein:

[0027] Figure 1 is a schematic diagram of the cavity segmentation of the cavity formation method of the salt cavern gas storage shown in the present invention;

[0028] Figure 2 is a schematic diagram of the cavity formation of the first cavity section N1 in the cavity formation method of the salt cavern gas storage shown in the present invention;

[0029] Figure 3 is a schematic diagram of the formation of the collapse layer in the cavity formation method of the salt cavern gas storage shown in the present invention;

[0030] Figure 4It is a schematic diagram of the erosion of the collapse layer in the cavity formation method of the salt cavern gas storage shown in the present invention;

[0031] Figure 5 It is a schematic diagram of the drilling of the second cavity section N2 in the cavity formation method of the salt cavern gas storage shown in the present invention;

[0032] Figure 6 It is a schematic diagram of the cavity formation of the second cavity section N2 in the cavity formation method of the salt cavern gas storage shown in the present invention;

[0033] Figure 7 It is a schematic diagram of the cavity formation of the first cavity section N1 using a jet nozzle in the cavity formation method of the salt cavern gas storage shown in the present invention.

[0034] In the figure, 1 is a drilling rig; 2 is a solvent inhibitor delivery channel; 3 is a brine discharge channel; 4 is a fresh water delivery channel; 5 is a first jet nozzle; 6 is a first jet pump; 7 is a protective agent delivery pipe; 8 is a second jet nozzle; 9 is a third jet nozzle; 10 is a second jet pump. Specific embodiments

[0035] In order to better understand the technical content of the present invention, specific embodiments are hereby given and described in conjunction with the accompanying drawings as follows.

[0036] At present, using the dissolvable property of rock salt, the cavity formation of salt cavern reservoirs all adopts the solution mining method, forming the cavity integrally from bottom to top, delivering fresh water to the bottom of the cavity, discharging the brine after dissolving the salt layer, then gradually dissolving upward, and using a solvent inhibitor to control the cavity shape. However, when gradually dissolving upward to form the cavity, there is always unsaturated brine at the pre-formed bottom of the cavity. Under the action of the unsaturated brine, the rock salt at the bottom of the cavity will dissolve, making it difficult to control the shape of the bottom of the cavity, resulting in the phenomenon of an irregular bottom of the cavity, causing a deviation between the shape of the entire cavity and the designed shape, leading to an uncontrollable change in the structural strength. When storing gas under high pressure, there are potential safety hazards such as cracking, leakage, and even collapse of the cavity, and the brine cannot be completely discharged, resulting in the inability to fully utilize the space inside the cavity.

[0037] [[ID=2**]]Example 1 -

[0038] Combined with Figures 1-6 shown, the present invention provides a cavity formation method for a salt cavern gas storage, including the following steps:

[0039] S1. Cavity design in segments: The preformed cavity is longitudinally divided into a first cavity segment N1 and a second cavity segment N2 according to the depth of the preformed cavity. The first cavity segment N1 includes a plurality of first cavities distributed longitudinally, and the second cavity segment N2 includes a second cavity. The ratio of the depth of several first cavities included in the first cavity segment N1 to the maximum diameter of the cavity is 1.1 - 1.2, and the preferred ratio is 1.1, so that the axial cross-section of the first cavity tends to be square, which is beneficial to the control of the cavity shape during the formation of cavity by dissolving rock salt. The ratio of the depth of the second cavity included in the second cavity segment N2 to the maximum diameter of the cavity is 0.5 - 0.7, and the preferred ratio is 0.6, so that the axial cross-sectional area of the second cavity tends to be a flat rectangle, and the depth dimension of the second cavity is smaller than the width dimension. When using side jet dissolution with fresh water, the dissolution speed in the horizontal direction is fast, and at the same time, the axial dissolution time is short, enabling the rapid formation of the cavity in the second cavity segment N2 and avoiding abnormal shapes at the cavity bottom;

[0040] S2. Cavity formation in the first cavity segment N1, including the following steps:

[0041] Step S21a: Use the drill 1 to drill to the bottom of the cavity, then inject fresh water, dissolve the rock salt, and discharge the brine;

[0042] Step S22a: Inject a solvent inhibitor into the cavity to effectively control the position where fresh water dissolves the rock salt, so as to control the cavity shape and make a single first cavity fully formed;

[0043] Among them, the multiple first cavities included in the first cavity segment N1 are formed successively from top to bottom. After the cavity formation in the first cavity segment N1 is completed, the solvent inhibitor used is nitrogen;

[0044] S3. Cavity formation at the bottom of the second cavity segment N2: After the multiple first cavities in the first cavity segment N1 are connected, use the drill 1 to drill to the bottom of the second cavity included in the second cavity segment N2, and then use the first jet nozzle 5 to laterally spray fresh water to the bottom of the second cavity and rotate circumferentially. Dissolve the rock salt with fresh water. At the same time, the laterally sprayed fresh water exerts an impact force on the rock salt in the horizontal direction of the second cavity, accelerating the dissolution of the rock salt at the bottom of the second cavity in the horizontal direction. After the bottom of the second cavity is formed, discharge the unsaturated brine and residues formed by dissolution to the ground;

[0045] S4. Protection of the bottom of the second cavity segment N2: After the unsaturated brine at the bottom of the second cavity segment N2 is discharged, continuously inject a protective agent into the bottom to slow down the dissolution speed of the rock salt at the bottom. The protective agent is saturated brine;

[0046] S5. Cavity formation above the second cavity section N2: After the protective agent injected at the bottom of the second cavity section N2 completely covers the bottom, the first jet nozzle 5 gradually moves upward along the bottom of the second cavity section N2 and rotates circumferentially to erode and dissolve the remaining rock salt above the second cavity section N2. The dissolved brine is discharged in real time until the cavity formation of the second cavity section N2 is completed and is completely connected to the first cavity section N1. After the cavity formation of the second cavity section N2 is completed, the brine in the first cavity section N1 and the second cavity section N2 is completely discharged, and finally the overall cavity formation of the first cavity section N1 and the second cavity section N2 is completed.

[0047] Combined with Figure 1 and Figure 2 As shown, in the above step S2, the injection of fresh water, the injection of inhibitor, and the discharge of brine are all transported through a composite pipe. Inside the composite pipe, there are an inhibitor transport channel 2, a brine discharge channel 3, and a fresh water transport channel 4. The composite pipe extends into the borehole. Fresh water is transported to the cavity through the fresh water transport channel 4, the inhibitor is transported to the cavity through the inhibitor transport channel 2, and the brine is discharged to the ground through the brine discharge channel 3. Among them, the brine is discharged to the ground by the method of injecting gas to discharge brine.

[0048] Combined with Figure 3 As shown, for the cavity formation of several cavities included in the first cavity section N1 in the above step S2, the cavity formation depth of each cavity is 9 / 10 of the cavity depth, so that a dissolution and collapse layer is formed between adjacent cavities in the first cavity section N1. After the cavity below the dissolution and collapse layer is formed, the dissolution and collapse layer is in a suspended state. When fresh water dissolves the cavity below, the suspended dissolution and collapse layer is accelerated to collapse and spall under the influence of gravity.

[0049] Combined with Figure 4 As shown, the second jet nozzle 8 is used to directly erode the suspended dissolution and collapse layer to further promote the collapse and spall of the dissolution and collapse layer.

[0050] Optionally, the second jet nozzle 8 is sent to the dissolution and collapse layer through a pipeline, and high-pressure water is transported to the second jet nozzle 8 through the pipeline.

[0051] Combined with Figure 5 and Figure 6 As shown, the first jet nozzle 6 in the above steps S3 and S5 is installed at the bottom of the pipe string. A first jet pump 6 and a protective agent delivery pipe 7 are also installed at the bottom of the pipe string. Inside the pipe string, there are a channel for supplying water to the first jet nozzle 5, a channel for supplying water to the jet pump, a channel for the jet pump to drain water, and a channel for transporting the protective agent to the protective agent delivery pipe. After the borehole is completed, the pipe string extends into the borehole. Water is supplied to the first jet nozzle 5 through the water supply channel inside the pipe string. The first jet nozzle 5 laterally sprays fresh water to erode the rock salt. The brine and residues in the cavity are discharged to the ground through the first jet pump 6, and the working liquid of the first jet pump 6 is transported through the corresponding water supply channel inside the pipe string. The protective agent is transported to the bottom of the cavity through the protective agent delivery pipe 7.

[0052] Further, the water injection pressure of the first jet nozzle 5 in the above steps S3 and S5 is 7.0 - 10.0 MPa, so that the water flow ejected by the first jet nozzle 5 has sufficient impact force to impact the rock salt and accelerate the erosion of the rock salt.

[0053] Furthermore, in the above step S4, the liquid level height of the protective agent gradually increases as the first jet nozzle 5 rises, so that the unsaturated brine formed by dissolution is always on the upper layer of the protective agent. At the same time, the input end of the first jet pump 6 also gradually rises as the jet nozzle rises, so that the input end of the first jet pump 6 is located on the upper layer of the protective agent in the above step S4. The input end of the first jet pump 6 can always extract the unsaturated brine on the upper layer of the protective agent, continuously discharge the upper-layer unsaturated brine through the first jet pump 6, and the protective agent delivery pipe 7 continuously supplements saturated brine to the bottom of the cavity, so that the bottom of the cavity is always in a state covered by saturated brine, avoiding the dissolution of the rock salt at the bottom of the cavity by the unsaturated brine and protecting the shape of the bottom of the cavity.

[0054] Embodiment 2

[0055] Compared with Embodiment 1, in Embodiment 2, the multiple longitudinally distributed first cavities included in the first cavity section N1 use jet nozzles to erode and dissolve the rock salt, accelerating the peeling and dissolution rate of the rock salt.

[0056] Combined with Figure 1 、 Figures 5-7 As shown, the present invention provides a method for creating a cavity in a salt cavern gas storage, including the following steps:

[0057] S1. Cavity design segmentation: The preformed cavity is longitudinally divided into a first cavity section N1 and a second cavity section N2 according to the depth of the preformed cavity. The first cavity section N1 includes multiple longitudinally distributed first cavities, and the second cavity section N2 includes a second cavity. The ratio of the depth of several first cavities included in the first cavity section N1 to the maximum diameter of the cavity is 1.1 - 1.2, and the preferred ratio is 1.1, so that the axial section of the first cavity tends to be square. When eroding and dissolving the rock salt to create a cavity, it is beneficial to control the shape of the cavity. The ratio of the depth of the second cavity included in the second cavity section N2 to the maximum diameter of the cavity is 0.5 - 0.7, and the preferred ratio is 0.6, so that the axial section area of the second cavity tends to be a flat rectangular shape. The depth dimension of the second cavity is smaller than the width dimension. When using fresh water for side jet erosion, the horizontal erosion speed is fast, and at the same time, the axial erosion time is short, enabling the rapid formation of the cavity in the second cavity section N2 and avoiding the appearance of abnormal shapes at the bottom of the cavity;

[0058] S2. Creating a cavity in the first cavity section N1, including the following steps:

[0059] Step S21b: Drill to the bottom of the first cavity with the drill rig 1, then use the third jet nozzle 9 to perform lateral freshwater spraying and rotate circumferentially to dissolve the rock salt with freshwater.

[0060] Step S22b: The laterally sprayed freshwater exerts an impact force on the rock salt in the horizontal direction of the first cavity, accelerating the corrosion of the rock salt in the horizontal direction of the first cavity, increasing the forming speed of the horizontal direction of the first cavity, and the third jet nozzle 9 gradually moves upward along the bottom of the cavity to erode and dissolve the rock salt in the first cavity from bottom to top, and discharge the brine to form a single first cavity.

[0061] Among them, the multiple first cavities included in the first cavity section N1 are formed successively from top to bottom, and the cavity creation of the first cavity section N1 is completed.

[0062] S3: Cavity creation at the bottom of the second cavity section N2: After the multiple first cavities in the first cavity section N1 are connected, drill to the bottom of the second cavity included in the second cavity section N2 with the drill rig 1, then use the first jet nozzle 5 to perform lateral freshwater spraying on the bottom of the second cavity and rotate circumferentially to dissolve the rock salt with freshwater. At the same time, the laterally sprayed freshwater exerts an impact force on the rock salt in the horizontal direction of the second cavity, accelerating the corrosion of the horizontal direction of the bottom of the second cavity. After the bottom of the second cavity is formed, discharge the unsaturated brine and residues formed by dissolution to the ground.

[0063] S4: Protection of the bottom of the second cavity section N2: After the unsaturated brine at the bottom of the second cavity section N2 is discharged, continuously inject a protective agent into the bottom to slow down the dissolution rate of the rock salt at the bottom. The protective agent is saturated brine.

[0064] S5: Cavity creation above the second cavity section N2: After the protective agent injected at the bottom of the second cavity section N2 completely covers the bottom, the first jet nozzle 5 gradually moves upward along the bottom of the second cavity section N2 and rotates circumferentially to erode and dissolve the remaining rock salt above the second cavity section N2. The dissolved brine is discharged in real time until the cavity creation of the second cavity section N2 is completed and is completely connected to the first cavity section N1. After the cavity creation of the second cavity section N2 is completed, discharge all the brine in the first cavity section N1 and the second cavity section N2, and finally complete the overall cavity creation of the first cavity section N1 and the second cavity section N2.

[0065] Combined with Figure 7 As shown, in the above step S2, the third jet nozzle 9 is installed at the bottom of the casing. A second jet pump 10 is also installed at the bottom of the casing. There are channels inside the casing for delivering water to the third jet nozzle 9, channels for delivering working fluid to the second jet pump 10, and channels for discharging brine. The dissolved brine and residues are pumped out to the ground via the second jet pump 10.

[0066] Combined with Figure 5 and Figure 6As shown in the figure, the first jet nozzle 5 in the above steps S3 and S5 is installed at the bottom of the pipe string. A first jet pump 6 and a protective agent delivery pipe 7 are also installed at the bottom of the pipe string. Inside the pipe string, there are channels for supplying water to the first jet nozzle 5, for supplying water to the jet pump, for draining water from the jet pump, and for delivering the protective agent to the protective agent delivery pipe. After the drilling is completed, the pipe string extends into the drilling hole. Water is supplied to the first jet nozzle 5 through the water supply channel inside the pipe string. The first jet nozzle 5 laterally sprays fresh water to erode the rock salt. The brine and residues in the cavity are discharged to the ground through the first jet pump 6. The working liquid of the first jet pump 6 is delivered through the corresponding water supply channel inside the pipe string. The protective agent is delivered to the bottom of the cavity through the protective agent delivery pipe 7.

[0067] Furthermore, the water injection pressure of the first jet nozzle 5 in the above steps S3 and S5 is 7.0 - 10.0 MPa, so that the water flow ejected by the first jet nozzle 5 has sufficient impact force to impact the rock salt and accelerate the erosion of the rock salt.

[0068] Still further, in the above step S4, the liquid level height of the protective agent gradually increases as the first jet nozzle 5 rises, so that the unsaturated brine formed by dissolution is always on the upper layer of the protective agent. At the same time, the input end of the first jet pump 6 also gradually rises as the jet nozzle rises, so that the input end of the first jet pump 6 is located on the upper layer of the protective agent in the above step S4. The input end of the first jet pump 6 can always extract the unsaturated brine on the upper layer of the protective agent. The unsaturated brine on the upper layer is continuously discharged through the first jet pump 6, and the protective agent delivery pipe 7 continuously replenishes saturated brine to the bottom of the cavity, so that the bottom of the cavity is always in a state covered by saturated brine, avoiding the dissolution of the rock salt at the bottom of the cavity by the unsaturated brine and protecting the shape of the bottom of the cavity.

[0069] Combined with the above embodiments, by dividing the entire cavity into a first cavity section N1 and a second cavity section N2, after the first cavity section N1 is cavity - formed, then the cavity - forming of the second cavity section N2 is carried out, reducing the contact time between the bottom of the cavity and the unsaturated brine. And during the cavity - forming process of the second cavity section N2, first, the bottom of the cavity is eroded and formed, and then saturated brine is injected to protect the bottom of the cavity, further reducing the dissolution speed of the bottom of the cavity after forming, shortening the dissolution time of the bottom of the cavity, protecting the shape of the bottom of the cavity, avoiding uncontrollable changes in the structural strength caused by the abnormal shape of the bottom of the cavity, and reducing potential safety hazards.

[0070] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Those with ordinary knowledge in the technical field to which the present invention pertains can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to what is defined by the claims.

Claims

1. A method for creating a cavity in a salt cavern gas storage reservoir, characterized in that, It includes the following steps: S1. Cavity segmentation: The preformed cavity is longitudinally divided into a first cavity segment N1 and a second cavity segment N2 according to the preformed cavity depth. The first cavity segment N1 includes a plurality of first cavities distributed longitudinally, and the second cavity segment N2 includes a second cavity located at the bottom of the first cavities; S2. Cavity formation in the first cavity segment N1: The plurality of first cavities included in the first cavity segment N1 are formed cavity by cavity from top to bottom until all the first cavities are connected, and then the brine is discharged, and the cavity formation in the first cavity segment N1 is completed; S3. Cavity formation at the bottom of the second cavity segment N2: After the plurality of first cavities in the first cavity segment N1 are connected, a drill is used to drill to the bottom of the second cavity included in the second cavity segment N2, and then a first jet nozzle is used to laterally spray fresh water to the bottom of the second cavity and rotate circumferentially. The fresh water dissolves the rock salt. At the same time, the laterally sprayed fresh water exerts an impact force on the rock salt in the horizontal direction of the second cavity, accelerating the dissolution of the rock salt in the horizontal direction at the bottom of the second cavity. After the bottom of the second cavity is formed, the unsaturated brine formed by dissolution is discharged; S4. Protection of the bottom of the second cavity segment N2: After the unsaturated brine at the bottom of the second cavity segment N2 is discharged, a protective agent is continuously injected into the bottom to slow down the dissolution rate of the rock salt at the bottom; S5. Cavity formation above the second cavity segment N2: After the protective agent injected into the bottom of the second cavity segment N2 completely covers the bottom, the first jet nozzle gradually moves upward along the bottom of the second cavity segment N2 and rotates circumferentially to erode and dissolve the remaining rock salt above the second cavity segment N2. The dissolved brine is discharged in real time until the cavity formation in the second cavity segment N2 is completed and is completely connected to the first cavity segment N1. After the cavity formation in the second cavity segment N2 is completed, the brine in the first cavity segment N1 and the second cavity segment N2 is completely discharged, and finally the overall cavity formation of the first cavity segment N1 and the second cavity segment N2 is completed.

2. The method for creating a cavity in a salt cavern gas storage reservoir according to claim 1, wherein In the above step S1, the ratio of the depth of each of the several first cavities included in the first cavity segment N1 to the maximum diameter of the cavity is 1.1 - 1.

2.

3. The method for creating a cavity in a salt cavern gas storage reservoir according to claim 1, wherein, In the above step S1, the ratio of the depth of the second cavity included in the second cavity segment N2 to the maximum diameter of the cavity is 0.5 - 0.

7.

4. The method for creating a cavity in a salt cavern gas storage reservoir according to claim 1, characterized in that, In the cavity formation of the several first cavities included in the first cavity segment N1 in the above step S2, the cavity formation of each first cavity includes the following steps: Step S21a. Use a drill to drill to the bottom of the cavity, then inject fresh water, dissolve the rock salt, and discharge the brine; Step S22a. Inject a solvent inhibitor into the cavity to effectively control the position where the fresh water dissolves the rock salt, so as to control the cavity shape and make a single first cavity completely formed; Among them, the plurality of first cavities included in the first cavity segment N1 are formed in sequence from top to bottom.

5. The method for creating a cavity in a salt cavern gas storage reservoir according to claim 4, wherein The solvent inhibitor is nitrogen.

6. The method for creating a cavity in a salt cavern gas storage reservoir according to claim 4, characterized in that, In the cavity formation of the several first cavities included in the first cavity segment N1 in the above step S2, the cavity formation depth of each first cavity is 9 / 10 of the cavity depth, so that a dissolution and collapse layer is formed between adjacent cavities in the first cavity segment N1. After the cavity below the dissolution and collapse layer is formed, the dissolution and collapse layer is in a suspended state. When the fresh water dissolves the cavity below, the suspended dissolution and collapse layer is accelerated to collapse and peel off under the influence of gravity.

7. The method for creating a cavity in a salt cavern gas storage reservoir according to claim 6, characterized in that, Use a second jet nozzle to directly erode the suspended dissolution and collapse layer.

8. The method for creating a cavity in a salt cavern gas storage reservoir according to claim 1, wherein The cavity formation of several first cavities included in the first cavity section N1 in the above step S2, the cavity formation of each first cavity includes the following steps: Step S21b: Drill to the bottom of the first cavity with a drill rig, then use a third jet nozzle to spray fresh water laterally and rotate circumferentially to dissolve rock salt with fresh water; Step S22b: The fresh water sprayed laterally exerts an impact force on the rock salt in the horizontal direction of the first cavity, accelerating the erosion of the first cavity in the horizontal direction, increasing the forming speed of the first cavity in the horizontal direction, and the third jet nozzle gradually moves upward along the bottom of the cavity to erode and dissolve the rock salt in the first cavity from bottom to top and discharge the brine to form a single first cavity; Among them, the multiple first cavities included in the first cavity section N1 are formed in sequence from top to bottom.

9. The method for creating a cavity in a salt cavern gas storage reservoir according to claim 1, characterized in that, In step S4, the liquid level height of the protective agent gradually increases as the self-vibrating cavitation jet device rises.

10. The method for creating a cavity in a salt cavern gas storage reservoir according to claim 1, wherein In step S5, the dissolved brine is pumped out by a jet pump, and the input end of the jet pump is located at the liquid level of the protective agent in the above step S4.

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