Method and system for testing connectivity of sediment at bottom of old storage tank cavity for brine mining in salt mine

Abstract

The invention provides a method and a system for testing connectivity of sediment at the bottom of a cavity of an old storage tank for brine mining in a salt mine, and the system comprises the storage tank with sediment at the bottom of the cavity; the injection well is communicated with the top of the repository, and a wellhead of the injection well is connected with an injection flow and pressure measuring mechanism; the communicating position of the testing well and the storage tank is located in a sediment area at the bottom of the storage tank, and a well mouth of the testing well is connected with a discharge flow and pressure measuring mechanism; the testing method comprises the following steps: testing liquid injected into the storage tank by the injection well flows into the testing well after flowing through sediment at the bottom of the cavity of the storage tank, and is discharged through the testing well; the injection flow and pressure measuring mechanism measures the flow and pressure of the injection end, and the discharge flow and pressure measuring mechanism measures the flow and pressure of the discharge end, so that the technical problem that the sediment characteristics at the bottom of the cavity of the repository are difficult to test is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of the construction process of gas storage caverns and energy storage caverns, and particularly relates to a method and a system for testing the connectivity of sediment at the bottom of an old storage cavern formed by brine extraction from a salt mine. Background Art

[0002] The cavity formation of a salt cavern gas storage is achieved by drilling to reach the target formation for cavity formation, and by using a mechanical pumping method to inject fresh water from the ground into the salt layer through a pipe string. Utilizing the characteristic that salt minerals are easily soluble in water, a cavity with a certain shape and volume is dissolved in the salt layer for storing gases such as natural gas. By using a method similar to that of the gas storage, an energy storage cavern can also be manufactured for storing pressurized gas.

[0003] Sediment usually exists at the bottom of the cavities of gas storage caverns and energy storage caverns. The sediment is blocky and granular insoluble matter generated during the cavity dissolution process, and the sediment accumulates together to form a loose accumulation. Affected by geological conditions, the salt rock quality in the formation where some gas storage caverns or energy storage caverns are constructed is poor, and the content of insoluble matter is relatively high.

[0004] Combined with the formation process of the sediment, the main sources of the sediment are as follows: (1) During the cavity formation process, after a large amount of sodium chloride in the salt formation is dissolved, most of the insoluble substances in the salt formation are released, forming insoluble substances with different particle sizes. By measuring the particle size of the brine produced at the site, only a very small part of the fine particles (particle size < 1 mm) of insoluble matter return to the ground through the brine discharge pipe string. The remaining most of the insoluble matter particles settle under their own gravity and gradually accumulate at the bottom of the cavity of the gas storage cavern or energy storage cavern, forming sediment. (2) For the salt mine in the layered salt rock formation, there are many interlayers (such as anhydrite layers, mudstone layers, glauberite layers, etc.), and the intergrowth of soluble salt layers and interlayers is a very typical feature. These interlayers are all difficult to dissolve; therefore, during the cavity formation process, along with the dissolution of the soluble salt layer, the insoluble and indissoluble interlayers in the cavity formation section are exposed; as the salt layer above the insoluble interlayer dissolves, the interlayer is in a suspended state and is immersed in unsaturated brine for a long time. The soluble components in the interlayer dissolve rapidly, forming a large number of cracks inside the interlayer; at the same time, the muddy interlayer contains relatively more clay minerals, and the clay minerals swell when encountering water, causing more micro-cracks to be generated in the interlayer. The brine enters the inside of the interlayer along these cracks, and more soluble substances and muddy cementing substances soften and dissolve, and the cracks in the interlayer further increase. During the process of water-soluble cavity formation, a large amount of insoluble matter generated by the dissolution of salt rock accumulates at the bottom of the cavity.

[0005] The generation and accumulation of insolubles restrict the construction of salt cavern gas storage and energy storage in many ways. While affecting the progress of cavity construction, it also affects the gas storage effect of the gas storage and the energy storage effect of the energy storage. In areas where the salt rock quality of salt cavern gas storage / energy storage is low, there are more insolubles, resulting in a low cavity formation rate of salt caverns and a high cost per cubic meter of gas storage space.

[0006] At the same time, the insoluble matter accumulated at the bottom of the cavity is often in different forms such as granular or blocky. The cavity is located at a great depth underground and has a large cavity space. Sampling the sediment at the bottom of the cavity is technically difficult, so it is difficult to test the insoluble sediment at the bottom of the cavity. Summary of the invention

[0007] The purpose of the present invention is to provide a method and system for testing the connectivity of sediment at the bottom of an old storage chamber of a salt mine, so as to solve the technical problem that the sediment characteristics at the bottom of the storage chamber are difficult to test.

[0008] The above-mentioned purpose of the present invention can be achieved by adopting the following technical solutions:

[0009] The present invention provides a method for testing connectivity of sediment at the bottom of an old storage tank cavity of salt mine brine, and adopts a system for testing connectivity of sediment at the bottom of an old storage tank cavity of salt mine brine;

[0010] The connectivity testing system for sediment at the bottom of the old storage chamber of salt mine includes:

[0011] A storage reservoir, wherein sediment exists at the bottom of the cavity of the storage reservoir;

[0012] An injection well, which is connected to the top of the storage reservoir, and the wellhead of the injection well is connected to an injection flow and pressure measuring mechanism;

[0013] A test well, wherein the communication position between the test well and the storage reservoir is located in the sediment area at the bottom of the storage reservoir, and the wellhead of the test well is connected to a discharge flow and pressure measurement mechanism;

[0014] The method for testing connectivity of sediment at the bottom of the old storage chamber of salt mine includes:

[0015] The test liquid injected into the storage reservoir by the injection well flows into the test well after passing through the sediment at the bottom of the cavity of the storage reservoir, and is discharged through the test well;

[0016] The injection flow and pressure measuring mechanism measures the flow and pressure at the injection end, and the discharge flow and pressure measuring mechanism measures the flow and pressure at the discharge end.

[0017] In a preferred embodiment, the method for testing the connectivity of sediment at the bottom of the old storage cavity for brine extraction from salt mines includes a fluidity test, and the fluidity test includes: the injection well continuously injects a test fluid into the storage cavity at a first flow rate. After the flow rate and pressure at the discharge end are stable, measure and record the flow rate and pressure at the discharge end, and the pressure at the injection end.

[0018] In a preferred embodiment, the fluidity test includes: after completing the test at the first flow rate, successively increase the flow rate value on the basis of the first flow rate, and respectively measure and record the flow rate and pressure at the discharge end after stabilization, and the pressure at the injection end.

[0019] In a preferred embodiment, the method for testing the connectivity of sediment at the bottom of the old storage cavity for brine extraction from salt mines includes a maximum discharge flow rate test, and the maximum discharge flow rate test includes: closing the test well, injecting a test fluid into the storage cavity through the injection well until the pressure at the injection end reaches a first pressure; the injection well stops injecting the test fluid and closes the injection well, then opens the test well, and measure and record the flow rate and pressure at the discharge end.

[0020] In a preferred embodiment, the maximum discharge flow rate test includes: after completing the test at the first pressure, the injection well continues to inject the test fluid into the storage cavity, and successively increases the pressure value on the basis of the first pressure to the upper limit pressure of the cavity of the storage cavity in a stepwise pressure increase manner, and respectively measure and record the flow rate and pressure at the discharge end after closing the injection well and opening the test well.

[0021] In a preferred embodiment, the maximum discharge flow rate test is carried out after the fluidity test.

[0022] In a preferred embodiment, according to the flow rate and pressure at the injection end, and the flow rate and pressure at the discharge end, calculate the frictional resistance of the test well string, the frictional resistance of the injection well string and the sediment frictional resistance.

[0023] In a preferred embodiment, the system for testing the connectivity of sediment at the bottom of the old storage cavity for brine extraction from salt mines includes a first liquid storage tank, a water injection truck and a first valve connected in series in sequence, and the first valve is connected to the injection well through an injection main pipeline.

[0024] In a preferred embodiment, the system for testing the connectivity of sediment at the bottom of the old storage cavity for brine extraction from salt mines includes a second liquid storage tank and a second valve connected in series in sequence, and the second valve is connected to the test well through a discharge main pipeline.

[0025] In a preferred embodiment, the first liquid storage tank is connected to the second liquid storage tank, and the test fluid in the second liquid storage tank can flow into the first liquid storage tank to achieve circulation.

[0026] The present invention provides a system for testing the connectivity of sediment at the bottom of an old storage cavity in a salt mine brine extraction, which is applied to the method for testing the connectivity of sediment at the bottom of an old storage cavity in a salt mine brine extraction. The system for testing the connectivity of sediment at the bottom of an old storage cavity in a salt mine brine extraction includes:

[0027] A storage cavity, where sediment exists at the bottom of the cavity;

[0028] An injection well, which is connected to the top of the storage cavity, and an injection flow rate and pressure measuring mechanism is connected to the wellhead of the injection well;

[0029] A test well, which is connected to the side or bottom of the storage cavity, and a discharge flow rate and pressure measuring mechanism is connected to the wellhead of the test well;

[0030] The test liquid injected into the storage cavity by the injection well can flow through the sediment at the bottom of the cavity of the storage cavity, then flow into the test well, and be discharged through the test well; the injection flow rate and pressure measuring mechanism is used to measure the flow rate and pressure at the injection end, and the discharge flow rate and pressure measuring mechanism is used to measure the flow rate and pressure at the discharge end.

[0031] The characteristics and advantages of the present invention are:

[0032] The connection position of the test well and the storage cavity is set at the side or bottom of the storage cavity, so that the test liquid can flow through the sediment at the bottom of the cavity of the storage cavity and then flow into the test well and be discharged. By injecting the test liquid through the injection well and discharging the test liquid through the test well, the connectivity of the injection well, the test well, the storage cavity and the sediment, as well as the physical properties of the sediment, are tested, the pore space and flow resistance of the bottom sediment are verified, effective data support is provided for subsequent gas injection and brine extraction and the calculation of the cavity volume of the storage cavity, which is convenient for the utilization of the sediment formed by insoluble substances at the bottom of the storage cavity of the salt mine, and the available storage volume of the salt mine storage cavity is greatly increased. Description of the Drawings

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0034] Figure 1 It is a schematic structural diagram of the system for testing the connectivity of sediment at the bottom of an old storage cavity in a salt mine brine extraction provided by the present invention;

[0035] Figure 2 It is a schematic diagram of the fluidity test in the method for testing the connectivity of sediment at the bottom of an old storage cavity in a salt mine brine extraction provided by the present invention;

[0036] Figure 3 Schematic diagram of the maximum discharge flow rate test in the method for testing the connectivity of sediment at the bottom of the old storage cavity for salt mine brine extraction provided by the present invention;

[0037] Figure 4 Table showing the relationship between the empirical formula of the resistance coefficient, the Reynolds number, and the flow pattern in the method for testing the connectivity of sediment at the bottom of the old storage cavity for salt mine brine extraction provided by the present invention.

[0038] Explanation of the reference numerals in the attached drawings:

[0039] 10. Injection well; 11. Injection flow rate and pressure measuring mechanism;

[0040] 21. First liquid storage tank; 22. First valve; 23. Injection main pipeline; 24. Injection water pump truck;

[0041] 30. Test well; 31. Discharge flow rate and pressure measuring mechanism;

[0042] 41. Second liquid storage tank; 42. Second valve; 43. Discharge main pipeline;

[0043] 50. Storage cavity; 51. Sediment. Detailed implementation manners

[0044] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0045] The physical properties of the insoluble sediment vary in different regions, and the porosity and permeability also differ. Since the physical properties of the sediment at the bottom of the salt mine storage cavity are not understood, it is not known whether the voids in the sediment can be utilized during storage, thus reducing the available storage volume of the storage cavity.

[0046] Solution 1

[0047] The present invention provides a method for testing the connectivity of sediment at the bottom of the old storage cavity for salt mine brine extraction, which uses a test system for the connectivity of sediment at the bottom of the old storage cavity for salt mine brine extraction; as Figure 1 shown, the test system for the connectivity of sediment at the bottom of the old storage cavity for salt mine brine extraction includes: a storage cavity 50, an injection well 10, and a test well 30. There is sediment 51 at the bottom of the storage cavity 50; the injection well 10 is connected to the top of the storage cavity 50, and an injection flow rate and pressure measuring mechanism 11 is connected to the wellhead of the injection well 10; the connection position of the test well 30 and the storage cavity 50 is within the sediment area at the bottom of the storage cavity 50, and a discharge flow rate and pressure measuring mechanism 31 is connected to the wellhead of the test well 30.

[0048] The method for testing the connectivity of sediment at the bottom of the old brine storage cavity in the salt mine includes:

[0049] The test fluid injected by the injection well 10 into the storage cavity 50 flows through the sediment 51 at the bottom of the cavity of the storage cavity 50 and then flows into the test well 30 and is discharged through the test well 30.

[0050] The injection flow rate and pressure measuring mechanism 11 measures the flow rate and pressure at the injection end, and the discharge flow rate and pressure measuring mechanism 31 measures the flow rate and pressure at the discharge end.

[0051] In this test method, the connection position between the test well 30 and the storage cavity 50 is set at the side or bottom of the storage cavity 50, so that the test fluid can flow through the sediment 51 at the bottom of the cavity of the storage cavity 50 and then flow into the test well 30 and be discharged. By injecting the test fluid through the injection well 10 and returning the test fluid through the test well 30, the connectivity of the injection well 10, the test well 30, the storage cavity 50 and the sediment 51, as well as the physical properties of the sediment 51, are tested, the pore space and flow resistance of the bottom sediment 51 are verified, providing effective data support for subsequent gas injection and brine drainage and the calculation of the cavity volume of the storage cavity 50, facilitating the utilization of the sediment 51 formed by insoluble substances at the bottom of the cavity of the storage cavity 50, and greatly increasing the available storage volume of the salt mine storage cavity 50.

[0052] In one embodiment, the method for testing the connectivity of sediment at the bottom of the old brine storage cavity in the salt mine includes a fluidity test, such as Figure 2 As shown, the fluidity test includes: the injection well 10 continuously injects the test fluid into the storage cavity 50 at a first flow rate. After the flow rate and pressure at the discharge end are stable, the flow rate and pressure at the discharge end and the pressure at the injection end are measured and recorded to test the connectivity of the injection well 10, the test well 30, the storage cavity 50 and the sediment 51, and to understand the influence of the injection well 10, the test well 30, the storage cavity 50 and the sediment 51 on the flow rate and pressure of the injected gas, facilitating the utilization of the cavity of the storage cavity 50.

[0053] Furthermore, the fluidity test includes: after the test at the first flow rate is completed, the flow rate value is gradually increased on the basis of the first flow rate, and the flow rate and pressure at the discharge end and the pressure at the injection end after stabilization are respectively measured and recorded to obtain the flow rate and pressure data at the discharge end when injecting the test fluid at different flow rates, providing effective data support for subsequent gas injection and brine drainage and the calculation of the cavity volume of the storage cavity 50.

[0054] In a specific embodiment, in the first stage of the test, the injection flow rate of the injection well 10 is controlled at about 20 cubic meters per hour until a pressure display appears at the wellhead end of the test well 30. Then, the flow rate of the injection well 10 is increased to 40 cubic meters per hour. After stabilizing the flow rate at 40 cubic meters per hour for a period of time, observe the pressure and flow rate at the wellhead end of the test well 30. If the wellhead pressure of the test well 30 stabilizes at a certain value, continue to increase the injection flow rate of the injection well 10 to 60 cubic meters per hour. After stabilizing at 60 cubic meters per hour for a period of time, observe the fluctuations in the flow rate and pressure at the wellhead of the test well 30. If the wellhead pressure and flow rate basically remain unchanged or are stable within a certain range, continue to increase the flow rate of the injection well 10 to 80 cubic meters per hour. And so on, until the injection displacement of the injection well 10 is increased to 120 cubic meters per hour. After the flow rate at the wellhead of the test well 30 stabilizes, the injection well 10 stops injecting. During the test process, record the pressure and flow rate at the wellhead of the injection well 10 and the pressure and flow rate at the wellhead of the test well 30 when the injection well 10 injects at different injection flow rates, and record them in a table.

[0055] In one embodiment, the method for testing the connectivity of the sediment at the bottom of the old storage cavity for brine extraction in a salt mine includes a maximum discharge flow rate test, as Figure 3 shown. The maximum discharge flow rate test includes: closing the test well 30, injecting a test liquid into the storage reservoir 50 through the injection well 10 until the pressure at the injection end reaches a first pressure; stopping the injection of the test liquid by the injection well 10 and closing the injection well 10, opening the test well 30, and measuring and recording the flow rate and pressure at the discharge end. The connectivity of the injection well 10, the test well 30, the storage reservoir 50, and the sediment 51 is tested through the pressure difference between the test well 30 and the injection well 10 and the discharge flow rate at the discharge end.

[0056] Furthermore, the maximum discharge flow rate test includes: after completing the test of the first pressure, the injection well 10 continues to inject the test liquid into the storage reservoir 50, and gradually increases the pressure value in stages on the basis of the first pressure to the upper limit pressure of the cavity of the storage reservoir 50, and respectively measures and records the flow rate and pressure at the discharge end after closing the injection well 10 and opening the test well 30. Through the method of increasing the pressure in stages, the pressure at the discharge end, the pressure difference between the two ends, and the discharge flow rate when the injection end is at different pressures are obtained.

[0057] Furthermore, performing the maximum discharge flow rate test after the fluidity test is beneficial to enabling the fluidity test and the maximum discharge flow rate test to be carried out continuously, improving the overall efficiency of the test.

[0058] In one embodiment, according to the flow rate and pressure at the injection end, as well as the flow rate and pressure at the discharge end, the frictional resistance of the string in the test well 30, the frictional resistance of the string in the injection well 10, and the sediment frictional resistance are calculated, so as to quantitatively understand the physical properties of the sediment 51 in the storage repository 50, provide effective data support for the subsequent calculation of the cavity volume of the storage repository 50, facilitate the full utilization of the sediment 51, and increase the available storage volume of the storage repository 50. Specifically, the fluid motion state can be judged first, and different fluid states can be distinguished according to the Reynolds number; then, according to the distinguished flow patterns such as laminar flow, hydraulically smooth, and hydraulically rough, the corresponding empirical formulas are selected to calculate the resistance coefficient, and the corresponding empirical formulas are selected to calculate the frictional resistance h fc and h fl of the string in the test well 30 and the string in the injection well 10; then, according to the frictional resistance h fc and h fl， of the string in the test well 30 and the string in the injection well 10, the sediment frictional resistance M is calculated. Through the present invention, it is possible to test the porosity, permeability, and flow frictional resistance of the sediment, etc.

[0059] In one embodiment, as Figure 1 shown, the sediment connectivity test system at the bottom of the old storage cavity of the salt mine brine extraction includes a first liquid storage tank 21, a water injection pump truck 24, and a first valve 22 connected in series in sequence. The first valve 22 is connected to the injection well 10 through an injection main pipeline 23. The test liquid is stored in the first liquid storage tank 21 and flows into the injection main pipeline 23 through the water injection pump truck 24, and then through the first valve 22, flows into the wellhead of the injection well 10 and continues to flow into the wellbore of the injection well 10. The injection flow rate and pressure measuring mechanism 11 includes a pressure gauge and a flow meter arranged at the wellhead to monitor the fluid pressure and fluid flow rate flowing into the wellhead.

[0060] The first liquid storage tank 21, the water injection pump truck 24, the injection main pipeline 23, the first valve 22, and the injection flow rate and pressure measuring mechanism 11 form an injection system. The test liquid in the first liquid storage tank 21 is pressurized by the water injection pump truck 24, and the test liquid enters the wellbore of the injection well 10 and the cavity of the storage repository 50 through the injection main pipeline 23, the first valve 22, and the wellhead of the injection well 10.

[0061] After the test liquid is injected, it enters the internal pore space of the sediment 51 through the cavity of the storage repository 50 and flows to the wellbore of the test well 30 through seepage.

[0062] As Figure 1As shown, the inlet point position of the test well 30 can be set at the side or bottom of the storage repository 50. In one embodiment, the sediment connectivity test system at the bottom of the old storage cavity of the salt mine brine extraction includes a second liquid storage tank 41 and a second valve 42 connected in series in sequence. The second valve 42 is connected to the test well 30 through a discharge main pipeline 43. The test liquid flows into the discharge main pipeline 43 through the wellhead of the test well 30, and the test liquid enters the second liquid storage tank 41 through the second valve 42 to monitor the pressure and flow rate at the discharge end, and at the same time collect the test liquid flowing out from the discharge end. The power source for the whole process is the injection pump truck 24. The discharge flow rate and pressure measuring mechanism 31 includes a pressure gauge and a flow meter arranged at the wellhead of the test well 30. The first valve 22 and the second valve 42 can adopt gate valves.

[0063] Further, the first liquid storage tank 21 is connected to the second liquid storage tank 41, and the test liquid in the second liquid storage tank 41 can flow into the first liquid storage tank 21 to realize circulation, so as to realize the recycling of the test liquid, save resources and reduce the test cost.

[0064] The storage repository 50 is a gas storage repository or an energy storage repository. The test liquid can adopt saturated brine. The injection well 10 can be an old well, and the test well 30 can be a brine discharge well.

[0065] In one embodiment, the specific process of the sediment connectivity test method for the bottom of the old storage cavity of the salt mine brine extraction provided by the present invention includes:

[0066] (1) Fill the first liquid storage tank 21 with saturated brine, and the volume of the brine is at least 300 cubic meters; the storage volume of the second liquid storage tank 41 is at least 300 cubic meters, and before the start of the test, the second liquid storage tank 41 needs to be kept empty.

[0067] (2) Connect the discharge main pipeline 43 according to the Figure 1 shown structure, and install the wellhead of the test well 30 and the supporting pressure gauge and flow meter.

[0068] (3) Pressurize the ground pipelines such as the discharge main pipeline 43 to ensure no spraying or leakage during the test.

[0069] (4) Before the start of the test, release the pressure in the cavity of the storage repository 50 so that the pressure at the wellhead of the injection well 10 is 0, and the excess brine can be reinjected into the first liquid storage tank 21.

[0070] (5) Start the test, open the first valve 22, the second valve 42 and the wellhead valve on the connecting pipeline, and inject saturated brine into the cavity of the storage repository 50 through the injection pump truck 24 until the flow rate at the discharge end of the test well 30 is stable.

[0071] (6) Increase the injection rate of the injection well 10 to 40 m³ / h. After injecting for a period of time until the flow rate and pressure at the discharge end are stable; after stabilization, record the pressure and flow rate of the test well 30 (i.e., the discharge end) as P L1 and Q L1 , and record the pressure at the injection end as P z1 ;

[0072] (7) And so on, increase the injection rate to 60, 80, 100, 120 m³ / h. (For injection rates of 60, 80, 100, 120 m³ / h, the corresponding pressures and flow rates at the wellhead of the test well 30 are recorded as P L2 , Q L2 , P L3 , Q L3 , and so on);

[0073] (8) After the test at an injection rate of 120 m³ / h is completed, close the wellhead valve of the test well 30;

[0074] (9) After the fluidity test is completed, start the maximum discharge flow rate test: continue to inject saturated brine into the wellhead of the injection well 10. The injection process is carried out in a segmented pressure increase manner. The specific process includes: taking the upper limit pressure of the cavity of the storage reservoir 50 as 4 MPa as an example, if the wellhead pressure at the injection end after the fluidity test is 1 MPa (recorded as P o1 ), then continue to inject saturated brine into the cavity until 2 MPa (recorded as P o2 ), then stop increasing the pressure, close the injection end valve, open the discharge end valve for 1 min, and record the changes in the flow rate and pressure at the discharge end (recorded as P 1 , Q 1 ); then close the discharge end valve, open the injection end valve, continue to inject saturated brine into the cavity of the storage reservoir 50 until 3 MPa, then stop increasing the pressure, close the injection end valve, open the discharge end valve for 1 min, and record the changes in the flow rate and pressure at the discharge end (recorded as P 2 , Q 2 ); repeat the above steps until the upper limit pressure; after the pressure reaches the upper limit pressure, close the wellhead of the injection well 10, open the wellhead of the test well 30, and test the final flow rate at the discharge end (recorded as P max , Q max ).

[0075] Fill in the above data in the following table:

[0076]

[0077] Table 1 Record Table of Connectivity Test Experimental Data

[0078] Conduct experimental parameter analysis and screening:

[0079] For P in the fluidity testL1 , P L2 , P L3 …… and Q L1 , Q L2 , Q L3 …… are plotted into the corresponding curves of pressure and flow rate;

[0080] For P in the maximum discharge flow rate test o1 , P o2 , P o3 ……, P 1 , P 2 , P 3 …P max , and Q 1 , Q 2 , Q 3 …Q max Plot the corresponding curves of pressure and flow rate;

[0081] For the two tests, select the corresponding injection end pressure, discharge end pressure, and flow rate approaching the maximum flow rate, denoted as Pz, P L , Q L , Po, P, Q.

[0082] Then, perform the calculation of flow resistance:

[0083] (1) First, judge the fluid motion state, distinguish different flow states using the Reynolds number, and calculate the resistance coefficient according to the empirical formula of the resistance coefficient. Specifically, refer to Figure 4 the relationship table of the empirical formula of the resistance coefficient, Reynolds number, and flow pattern shown;

[0084] (2) After the resistance coefficient is determined, divide it into three cases according to the flow pattern:

[0085] a) Laminar flow:

[0086]

[0087]

[0088] b) Hydraulically smooth:

[0089]

[0090] c) Hydraulically rough:

[0091]

[0092] In the above formulas: h f is the pipe friction, λ is the friction coefficient, l is the pipe length, v is the flow velocity, d is the pipe diameter, ρ is the fluid density, μ is the dynamic viscosity, Q is the flow rate, ε is the roughness, and △ is the absolute roughness.

[0093] The test data according to the above step (9): P z , P L , Q L , P o , P, Q, substitute into the above formula to calculate the friction resistance inside the pipe string. Assume the well depth of the test well 30 is h, and the well depth of the old well is H. Other parameters in the friction resistance calculation are substituted according to the actual pipe string parameters, and the friction resistances of the pipe strings in the test well 30 and the old well are calculated as h fc and h fl .

[0094] Then calculate the sediment friction resistance M:

[0095] M = ((P o - P - h fc1 ) + (P z - h fl - h fc2 - P L )) / 2

[0096] The method for testing the connectivity of the sediment at the bottom of the old storage cavity for salt mining in a salt mine provided by the present invention uses the method of returning brine from the water injection and brine discharge well in the old well to test the connectivity among the old wellbore, the cavity 50 of the storage, and the brine discharge well, and tests the basic parameters such as the porosity and flow resistance of the sediment 51 at the bottom, providing first-hand data for the utilization of the sediment 51 and effective data support for subsequent gas injection and brine discharge and cavity volume calculation.

[0097] Solution Two

[0098] The present invention provides a system for testing the connectivity of the sediment at the bottom of the old storage cavity for salt mining, which is applied to the method for testing the connectivity of the sediment at the bottom of the old storage cavity for salt mining in a salt mine as Figure 1 shown. The system for testing the connectivity of the sediment at the bottom of the old storage cavity for salt mining includes:

[0099] A storage 50 with sediment 51 existing at the bottom of the cavity of the storage 50;

[0100] An injection well 10, which is connected to the top of the storage 50, and an injection flow rate and pressure measuring mechanism 11 is connected to the wellhead of the injection well 10;

[0101] A test well 30, which is connected to the side or bottom of the storage 50, and a discharge flow rate and pressure measuring mechanism 31 is connected to the wellhead of the test well 30;

[0102] The test liquid injected into the storage reservoir 50 by the injection well 10 can flow through the sediment 51 at the bottom of the cavity of the storage reservoir 50, then flow into the test well 30, and be discharged through the test well 30; the injection flow rate and pressure measuring mechanism 11 is used to measure the flow rate and pressure at the injection end, and the discharge flow rate and pressure measuring mechanism 31 is used to measure the flow rate and pressure at the discharge end.

[0103] Through this test system, the connectivity test of the sediment at the bottom of the old storage reservoir for brine extraction in the salt mine can be implemented. The test liquid can flow through the sediment 51 at the bottom of the cavity of the storage reservoir 50 and then flow into the test well 30 and be discharged. By injecting the test liquid using the injection well 10 and returning the test liquid from the test well 30, the connectivity of the injection well 10, the test well 30, the storage reservoir 50 and the sediment 51, as well as the physical properties of the sediment 51, can be tested, the pore space and flow resistance of the bottom sediment 51 can be verified, providing effective data support for subsequent gas injection and brine discharge and the calculation of the cavity volume of the storage reservoir 50, facilitating the utilization of the sediment 51 formed by the insoluble substances at the bottom of the cavity of the storage reservoir 50, and greatly increasing the available storage capacity volume of the salt mine storage reservoir 50.

[0104] The above are only several embodiments of the present invention. Those skilled in the art can make various changes or modifications to the embodiments of the present invention without departing from the spirit and scope of the present invention based on the content disclosed in the application documents.

Claims

1. A method for testing the connectivity of sediment at the bottom of an old storage cavity for brine extraction from a salt mine, characterized in that, a testing system for the connectivity of sediment at the bottom of an old storage cavity for brine extraction from a salt mine is adopted; the testing system for the connectivity of sediment at the bottom of an old storage cavity for brine extraction from a salt mine includes: a storage cavity, where sediment exists at the bottom of the cavity; an injection well, which is connected to the top of the storage cavity, and an injection flow rate and pressure measuring mechanism is connected to the wellhead of the injection well; a testing well, the connection position of the testing well and the storage cavity is within the sediment area at the bottom of the storage cavity, and a discharge flow rate and pressure measuring mechanism is connected to the wellhead of the testing well; the method for testing the connectivity of sediment at the bottom of an old storage cavity for brine extraction from a salt mine includes: the test liquid injected into the storage cavity by the injection well flows through the sediment at the bottom of the cavity of the storage cavity, then flows into the testing well, and is discharged through the testing well; the injection flow rate and pressure measuring mechanism measures the flow rate and pressure at the injection end, and the discharge flow rate and pressure measuring mechanism measures the flow rate and pressure at the discharge end.

2. The method for testing the connectivity of sediment at the bottom of an old storage cavity for brine extraction from a salt mine according to claim 1, characterized in that, the method for testing the connectivity of sediment at the bottom of an old storage cavity for brine extraction from a salt mine includes a fluidity test, and the fluidity test includes: the injection well continuously injects the test liquid into the storage cavity at a first flow rate. After the flow rate and pressure at the discharge end are stable, measure and record the flow rate and pressure at the discharge end, as well as the pressure at the injection end.

3. The method for testing the connectivity of sediment at the bottom of an old storage cavity for brine extraction from a salt mine according to claim 2, characterized in that, the fluidity test includes: after completing the test at the first flow rate, successively increase the flow rate value on the basis of the first flow rate, and respectively measure and record the flow rate and pressure at the discharge end after stabilization, as well as the pressure at the injection end.

4. The method for testing the connectivity of sediment at the bottom of an old storage cavity for brine extraction from a salt mine according to claim 2, characterized in that, the method for testing the connectivity of sediment at the bottom of an old storage cavity for brine extraction from a salt mine includes a maximum discharge flow rate test, and the maximum discharge flow rate test includes: close the testing well, inject the test liquid into the storage cavity through the injection well until the pressure at the injection end is a first pressure; stop injecting the test liquid through the injection well and close the injection well, open the testing well, and measure and record the flow rate and pressure at the discharge end.

5. The method for testing the connectivity of sediment at the bottom of an old storage cavity for brine extraction from a salt mine according to claim 4, characterized in that, the maximum discharge flow rate test includes: after completing the test at the first pressure, the injection well continues to inject the test liquid into the storage cavity, and successively increase the pressure value on the basis of the first pressure to the upper limit pressure of the cavity of the storage cavity in a segmented pressure increasing manner, and respectively measure and record the flow rate and pressure at the discharge end after closing the injection well and opening the testing well.

6. The method for testing the connectivity of sediment at the bottom of an old storage cavity for brine extraction from a salt mine according to claim 4, characterized in that, the maximum discharge flow rate test is carried out after the fluidity test.

7. The method for testing the connectivity of sediment at the bottom of an old storage cavity for brine extraction from a salt mine according to claim 6, Characterized in that, Based on the flow rate and pressure at the injection end, as well as the flow rate and pressure at the discharge end, calculate the frictional resistance of the test well string, the frictional resistance of the injection well string, and the sediment frictional resistance.

8. The method for testing the connectivity of sediment at the bottom of an old storage cavity for salt mine brine extraction according to claim 1, Characterized in that, The system for testing the connectivity of sediment at the bottom of an old storage cavity for salt mine brine extraction includes a first liquid storage tank, an injection water pump truck, and a first valve connected in series in sequence. The first valve is connected to the injection well through an injection main pipeline.

9. The method for testing the connectivity of sediment at the bottom of an old storage cavity for salt mine brine extraction according to claim 8, Characterized in that, The system for testing the connectivity of sediment at the bottom of an old storage cavity for salt mine brine extraction includes a second liquid storage tank and a second valve connected in series in sequence. The second valve is connected to the test well through a discharge main pipeline.

10. The method for testing the connectivity of sediment at the bottom of an old storage cavity for salt mine brine extraction according to claim 9, Characterized in that, The first liquid storage tank is connected to the second liquid storage tank, and the test liquid in the second liquid storage tank can flow into the first liquid storage tank to achieve circulation.

11. A system for testing the connectivity of sediment at the bottom of an old storage cavity for salt mine brine extraction, Characterized in that, Applied to the method for testing the connectivity of sediment at the bottom of an old storage cavity for salt mine brine extraction according to any one of claims 1-10, the system for testing the connectivity of sediment at the bottom of an old storage cavity for salt mine brine extraction includes: A storage cavity, where sediment exists at the bottom of the cavity; An injection well, which is connected to the top of the storage cavity, and an injection flow rate and pressure measuring mechanism is connected to the wellhead of the injection well; A test well, which is connected to the side or bottom of the storage cavity, and a discharge flow rate and pressure measuring mechanism is connected to the wellhead of the test well; The test liquid injected into the storage cavity by the injection well can flow through the sediment at the bottom of the cavity of the storage cavity, then flow into the test well, and be discharged through the test well; the injection flow rate and pressure measuring mechanism is used to measure the flow rate and pressure at the injection end, and the discharge flow rate and pressure measuring mechanism is used to measure the flow rate and pressure at the discharge end.

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